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Hopman LHGA, Solís-Lemus JA, Hofman MBM, Bhagirath P, Borodzicz-Jazdzyk S, van Pouderoijen N, Krafft AJ, Schmidt M, Allaart CP, Niederer SA, Götte MJW. Performance of Image-navigated and Diaphragm-navigated 3D Late Gadolinium-enhanced Cardiac MRI for the Assessment of Atrial Fibrosis. Radiol Cardiothorac Imaging 2024; 6:e230172. [PMID: 38573128 PMCID: PMC11056763 DOI: 10.1148/ryct.230172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 12/19/2023] [Accepted: 02/29/2024] [Indexed: 04/05/2024]
Abstract
Purpose To perform a qualitative and quantitative evaluation of the novel image-navigated (iNAV) 3D late gadolinium enhancement (LGE) cardiac MRI imaging strategy in comparison with the conventional diaphragm-navigated (dNAV) 3D LGE cardiac MRI strategy for the assessment of left atrial fibrosis in atrial fibrillation (AF). Materials and Methods In this prospective study conducted between April and September 2022, 26 consecutive participants with AF (mean age, 61 ± 11 years; 19 male) underwent both iNAV and dNAV 3D LGE cardiac MRI, with equivalent spatial resolution and timing in the cardiac cycle. Participants were randomized in the acquisition order of iNAV and dNAV. Both, iNAV-LGE and dNAV-LGE images were analyzed qualitatively using a 5-point Likert scale and quantitatively (percentage of atrial fibrosis using image intensity ratio threshold 1.2), including testing for overlap in atrial fibrosis areas by calculating Dice score. Results Acquisition time of iNAV was significantly lower compared with dNAV (4.9 ± 1.1 minutes versus 12 ± 4 minutes, P < .001, respectively). There was no evidence of a difference in image quality for all prespecified criteria between iNAV and dNAV, although dNAV was the preferred image strategy in two-thirds of cases (17/26, 65%). Quantitative assessment demonstrated that mean fibrosis scores were lower for iNAV compared with dNAV (12 ± 8% versus 20 ± 12%, P < .001). Spatial correspondence between the atrial fibrosis maps was modest (Dice similarity coefficient, 0.43 ± 0.15). Conclusion iNAV-LGE acquisition in individuals with AF was more than twice as fast as dNAV acquisition but resulted in a lower atrial fibrosis score. The differences between these two strategies might impact clinical interpretation. ©RSNA, 2024.
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Affiliation(s)
- Luuk H. G. A. Hopman
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - José A. Solís-Lemus
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Mark B. M. Hofman
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Pranav Bhagirath
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Sonia Borodzicz-Jazdzyk
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Nikki van Pouderoijen
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Axel J. Krafft
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Michaela Schmidt
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Cornelis P. Allaart
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Steven A. Niederer
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
| | - Marco J. W. Götte
- From the Department of Cardiology, Amsterdam University Medical
Center, De Boelelaan 1118, 1081 HV, Amsterdam, the Netherlands (L.H.G.A.H.,
P.B., S.B.J., N.v.P., C.P.A., M.J.W.G.); Division of Imaging Sciences and
Biomedical Engineering, King’s College London, London, United Kingdom
(J.A.S.L., S.A.N.); Department of Radiology and Nuclear Medicine, Amsterdam UMC,
Amsterdam, the Netherlands (M.B.M.H.); First Department of Cardiology, Medical
University of Warsaw, Warsaw, Poland (S.B.J.); and Siemens Healthineers,
Erlangen, Germany (A.J.K., M.S.)
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Guglielmo M, Rier S, Zan GD, Krafft AJ, Schmidt M, Kunze KP, Botnar RM, Prieto C, van der Heijden J, Van Driel V, Ramanna H, van der Harst P, van der Bilt I. Cardiac magnetic resonance for early atrial lesion visualization post atrial fibrillation radiofrequency catheter ablation. J Cardiovasc Electrophysiol 2024; 35:258-266. [PMID: 38065834 DOI: 10.1111/jce.16152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Revised: 11/01/2023] [Accepted: 11/27/2023] [Indexed: 02/07/2024]
Abstract
BACKGROUND Incomplete atrial lesions resulting in pulmonary vein-left atrium reconnection after pulmonary vein antrum isolation (PVAI), are related to atrial fibrillation (AF) recurrence. Unfortunately, during the PVAI procedure, fluoroscopy and electroanatomic mapping cannot accurately determine the location and size of the ablation lesions in the atrial wall and this can result in incomplete PVAI lesions (PVAI-L) after radiofrequency catheter ablation (RFCA). AIM We seek to evaluate whether cardiac magnetic resonance (CMR), immediately after RFCA of AF, can identify PVAI-L by characterizing the left atrial tissue. METHODS Ten patients (63.1 ± 5.7 years old, 80% male) receiving a RFCA for paroxysmal AF underwent a CMR before (<1 week) and after (<1 h) the PVAI. Two-dimensional dark-blood T2-weighted short tau inversion recovery (DB-STIR), Three-dimensional inversion-recovery prepared long inversion time (3D-TWILITE) and three-dimensional late gadolinium enhancement (3D-LGE) images were performed to visualize PVAI-L. RESULTS The PVAI-L was visible in 10 patients (100%) using 3D-TWILITE and 3D-LGE. Conversely, On DB-STIR, the ablation core of the PAVI-L could not be identified because of a diffuse high signal of the atrial wall post-PVAI. Microvascular obstruction was identified in 7 (70%) patients using 3D-LGE. CONCLUSION CMR can visualize PVAI-L immediately after the RFCA of AF even without the use of contrast agents. Future studies are needed to understand if the use of CMR for PVAI-L detection after RFCA can improve the results of ablation procedures.
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Affiliation(s)
- Marco Guglielmo
- Department of Cardiology, Division of Heart and Lungs, Utrecht University Medical Center, Utrecht University, Utrecht, The Netherlands
- Department of Cardiology, Haga Teaching Hospital, The Hague, The Netherlands
| | - Sophie Rier
- Department of Cardiology, Haga Teaching Hospital, The Hague, The Netherlands
| | - Giulia De Zan
- Department of Cardiology, Division of Heart and Lungs, Utrecht University Medical Center, Utrecht University, Utrecht, The Netherlands
- Department of Translational Medicine, University of Eastern Piedmont, Novara, Italy
| | | | | | - Karl P Kunze
- MR Research Collaborations, Siemens Healthcare Limited, Camberley, UK
- King's College London, London, UK
| | - Rene M Botnar
- MR Research Collaborations, Siemens Healthcare Limited, Camberley, UK
- King's College London, London, UK
| | - Claudia Prieto
- MR Research Collaborations, Siemens Healthcare Limited, Camberley, UK
- King's College London, London, UK
| | | | - Vincent Van Driel
- Department of Cardiology, Haga Teaching Hospital, The Hague, The Netherlands
| | - Hemanth Ramanna
- Department of Cardiology, Haga Teaching Hospital, The Hague, The Netherlands
| | - Pim van der Harst
- Department of Cardiology, Division of Heart and Lungs, Utrecht University Medical Center, Utrecht University, Utrecht, The Netherlands
| | - Ivo van der Bilt
- Department of Cardiology, Division of Heart and Lungs, Utrecht University Medical Center, Utrecht University, Utrecht, The Netherlands
- Department of Cardiology, Haga Teaching Hospital, The Hague, The Netherlands
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Schuchardt FF, Krafft AJ, Miguel Telega L, Küchlin S, Lagrèze WA, Demerath T, Arnold P, Fung C, Kraus LM, Hennemuth A, Beck J, Urbach H, Weiller C, Harloff A. Interrelation Between Cerebrospinal Fluid Pressure, Intracranial Morphology and Venous Hemodynamics Studied by 4D Flow MRI. Clin Neuroradiol 2024:10.1007/s00062-023-01381-0. [PMID: 38277058 DOI: 10.1007/s00062-023-01381-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2023] [Accepted: 12/26/2023] [Indexed: 01/27/2024]
Abstract
PURPOSE To quantify the effects of CSF pressure alterations on intracranial venous morphology and hemodynamics in idiopathic intracranial hypertension (IIH) and spontaneous intracranial hypotension (SIH) and assess reversibility when the underlying cause is resolved. METHODS We prospectively examined venous volume, intracranial venous blood flow and velocity, including optic nerve sheath diameter (ONSD) as a noninvasive surrogate of CSF pressure changes in 11 patients with IIH, 11 age-matched and sex-matched healthy controls and 9 SIH patients, before and after neurosurgical closure of spinal dural leaks. We applied multiparametric MRI including 4D flow MRI, time-of-flight (TOF) and T2-weighted half-Fourier acquisition single-shot turbo-spin echo (HASTE). RESULTS Sinus volume overlapped between groups at baseline but decreased after treatment of intracranial hypotension (p = 0.067) along with a significant increase of ONSD (p = 0.003). Blood flow in the middle and dorsal superior sagittal sinus was remarkably lower in patients with higher CSF pressure (i.e., IIH versus controls and SIH after CSF leak closure) but blood flow velocity was comparable cross-sectionally between groups and longitudinally in SIH. CONCLUSION We were able to demonstrate the interaction of CSF pressure, venous volumetry, venous hemodynamics and ONSD using multiparametric brain MRI. Closure of CSF leaks in SIH patients resulted in symptoms suggestive of increased intracranial pressure and caused a subsequent decrease of intracranial venous volume and of blood flow within the superior sagittal sinus while ONSD increased. In contrast, blood flow parameters from 4D flow MRI did not discriminate IIH, SIH and controls as hemodynamics at baseline overlapped at most vessel cross-sections.
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Affiliation(s)
- Florian F Schuchardt
- Department of Neurology and Neurophysiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
- Department of Neurology and Neurophysiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Str. 64, 79106, Freiburg, Germany.
| | - Axel J Krafft
- Medical Physics, Department of Radiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Lidia Miguel Telega
- Department of Neurology and Neurophysiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Neurosurgery, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sebastian Küchlin
- Department of Neuro-ophthalmology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Wolf A Lagrèze
- Department of Neuro-ophthalmology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Theo Demerath
- Department of Neuroradiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg , Freiburg, Germany
| | - Philipp Arnold
- Department of Neuroradiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg , Freiburg, Germany
| | - Christian Fung
- Department of Neurosurgery, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Luisa M Kraus
- Department of Neurosurgery, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Anja Hennemuth
- Institute for Cardiovascular Computer-assisted Medicine, Charité, Universitätsmedizin Berlin, Campus Virchow-Klinikum, Berlin, Germany
| | - Jürgen Beck
- Department of Neurosurgery, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Horst Urbach
- Department of Neuroradiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg , Freiburg, Germany
| | - Cornelius Weiller
- Department of Neurology and Neurophysiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andreas Harloff
- Department of Neurology and Neurophysiology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Beltrán S, Reisert M, Krafft AJ, Frase S, Mast H, Urbach H, Luetzen N, Hohenhaus M, Wolf K. Spinal cord motion and CSF flow in the cervical spine of 70 healthy participants. NMR Biomed 2023:e5013. [PMID: 37533376 DOI: 10.1002/nbm.5013] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 06/14/2023] [Accepted: 07/10/2023] [Indexed: 08/04/2023]
Abstract
Pulsatile spinal cord and CSF velocities related to the cardiac cycle can be depicted by phase-contrast MRI. Among patients with spontaneous intracranial hypotension, we have recently described relevant differences compared with healthy controls in segment C2/C3. The method might be a promising tool to solve clinical and diagnostic ambiguities. Therefore, it is important to understand the physiological range and the effects of clinical and anatomical parameters in healthy volunteers. Within a prospective study, 3D T2 -weighted MRI for spinal canal anatomy and cardiac-gated phase-contrast MRI adapted to CSF flow and spinal cord motion for time-resolved velocity data and derivatives were performed in 70 participants (age 20-79 years) in segments C2/C3 and C5/C6. Correlations were analyzed by multiple linear regression models; p < 0.01 was required to assume a significant impact of clinical or anatomical data quantified by the regression coefficient B. Data showed that in C2/C3, the CSF and spinal cord craniocaudal velocity ranges were 4.5 ± 0.9 and 0.55 ± 0.15 cm/s; the total displacements were 1.1 ± 0.3 and 0.07 ± 0.02 cm, respectively. The craniocaudal range of the CSF flow rate was 8.6 ± 2.4 mL/s; the CSF stroke volume was 2.1 ± 0.7 mL. In C5/C5, physiological narrowing of the spinal canal caused higher CSF velocity ranges and lower stroke volume (C5/C6 B = +1.64 cm/s, p < 0.001; B = -0.4 mL, p = 0.002, respectively). Aging correlated to lower spinal cord motion (e.g., B = -0.01 cm per 10 years of aging, p < 0.001). Increased diastolic blood pressure was associated with lower spinal cord motion and CSF flow parameters (e.g., C2/C3 CSF stroke volume B = -0.3 mL per 10 mmHg, p < 0.001). Males showed higher CSF flow and spinal cord motion (e.g., CSF stroke volume B = +0.5 mL, p < 0.001; total displacement spinal cord B = +0.016 cm, p = 0.002). We therefore propose to stratify data for age and sex and to adjust for diastolic blood pressure and segmental narrowing in future clinical studies.
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Affiliation(s)
- Saúl Beltrán
- Department of Neurology and Neurophysiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marco Reisert
- Department of Radiology, Medical Physics, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Sibylle Frase
- Department of Neurology and Neurophysiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Hansjoerg Mast
- Department of Neuroradiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Horst Urbach
- Department of Neuroradiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Niklas Luetzen
- Department of Neuroradiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marc Hohenhaus
- Department of Neurosurgery, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Katharina Wolf
- Department of Neurology and Neurophysiology, Medical Center-Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Guggenberger K, Krafft AJ, Ludwig U, Raithel E, Forman C, Meckel S, Hennig J, Bley TA, Vogel P. Intracranial vessel wall imaging framework - Data acquisition, processing, and visualization. Magn Reson Imaging 2021; 83:114-124. [PMID: 34403760 DOI: 10.1016/j.mri.2021.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2020] [Revised: 07/09/2021] [Accepted: 08/12/2021] [Indexed: 10/20/2022]
Abstract
OBJECTIVE Assessment of vessel walls is an integral part in diagnosis and disease monitoring of vascular diseases such as vasculitis. Vessel wall imaging (VWI), in particular of intracranial arteries, is the domain of Magnetic Resonance Imaging (MRI) - but still remains a challenge. The tortuous anatomy of intracranial arteries and the need for high resolution within clinically acceptable scan times require special technical conditions regarding the hardware and software environments. MATERIALS AND METHODS In this work a dedicated framework for intracranial VWI is presented offering an optimized, black-blood 3D T1-weighted post-contrast Compressed Sensing (CS)-accelerated MRI sequence prototype combined with dedicated 3D-GUI supported post-processing tool for the CPR visualization of tortuous arbitrary vessel structures. RESULTS Using CS accelerated MRI sequence, the scanning time for high-resolution 3D black-blood CS-space data could be reduced to under 10 min. These data are adequate for a further processing to extract straightened visualizations (curved planar reformats - CPR). First patient data sets could be acquired in clinical environment. CONCLUSION A highly versatile framework for VWI visualization was demonstrated utilizing a post-processing tool to extract CPR reformats from high-resolution 3D black-blood CS-SPACE data, enabling simplified and optimized assessment of intracranial arteries in intracranial vascular disorders, especially in suspected intracranial vasculitis, by stretching their tortuous course. The processing time from about 15-20 min per patient (data acquisition and further processing) allows the integration into clinical routine.
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Affiliation(s)
- Konstanze Guggenberger
- Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ute Ludwig
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | | | - Stephan Meckel
- Department of Neuroradiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jürgen Hennig
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Thorsten A Bley
- Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany
| | - Patrick Vogel
- Department of Diagnostic and Interventional Radiology, University Hospital Würzburg, Würzburg, Germany; Department of Experimental Physics 5 (Biophysics), University of Würzburg, Würzburg, Germany.
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Shokina N, Teschner G, Bauer A, Tropea C, Egger H, Hennig J, Krafft AJ. Parametric Sequential Method for MRI-Based Wall Shear Stress Quantification. IEEE Trans Med Imaging 2021; 40:1105-1112. [PMID: 33347405 DOI: 10.1109/tmi.2020.3046331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Wall shear stress (WSS) has been suggested as a potential biomarker in various cardiovascular diseases and it can be estimated from phase-contrast Magnetic Resonance Imaging (PC-MRI) velocity measurements. We present a parametric sequential method for MRI-based WSS quantification consisting of a geometry identification and a subsequent approximation of the velocity field. This work focuses on its validation, investigating well controlled high-resolution in vitro measurements of turbulent stationary flows and physiological pulsatile flows in phantoms. Initial tests for in vivo 2D PC-MRI data of the ascending aorta of three volunteers demonstrate basic applicability of the method to in vivo.
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Wolf K, Reisert M, Beltrán SF, Klingler JH, Hubbe U, Krafft AJ, Egger K, Hohenhaus M. Focal cervical spinal stenosis causes mechanical strain on the entire cervical spinal cord tissue - A prospective controlled, matched-pair analysis based on phase-contrast MRI. Neuroimage Clin 2021; 30:102580. [PMID: 33578322 PMCID: PMC7875814 DOI: 10.1016/j.nicl.2021.102580] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Revised: 11/30/2020] [Accepted: 01/21/2021] [Indexed: 12/27/2022]
Abstract
BACKGROUND Focally increased spinal cord motion at the level of cervical spinal stenosis has been revealed by phase-contrast MRI (PC-MRI). OBJECTIVE To investigate spinal cord motion among patients suffering of degenerative cervical myelopathy (DCM) across the entire cervical spine applying automated segmentation and standardized PC-MRI post-processing protocols. METHODS Prospective, matched-pair controlled trial on 29 patients with stenosis at C5/C6. MRI-protocol covering all cervical segments: 3D T2-SPACE, prospectively ECG-triggered sagittal PC-MRI. Segmentation by trained 3D hierarchical deep convolutional neural network and data processing were conducted via in-house software pipeline. Parameters per segment: maximum velocity, peak-to-peak (PTP)-amplitude, total displacement, PTP-amplitudeHB (PTP-amplitude per duration of heartbeat), and, for characterization of intraindividual alterations, the PTP-amplitude index between the cervical segments C3/C4-C7/T1 and C2/C3. RESULTS Spinal cord motion was increased at C4/C5, C5/C6 and C6/C7 among patients (all parameters, p < 0.001-0.025). The PTP-amplitude index revealed an increase from C3/C4 to C4/C5 (p = 0.002), C4/C5 to C5/C6 (p = 0.037) and a decrease from C5/C6 to C6/C7 and C6/C7 to C7/T1 (p < 0.001, each). This implied an up-building stretch on spinal cord tissue cranial and a mechanical compression caudal of the stenotic level. Furthermore, significant far range effects across the entire cervical spinal cord were observed (e.g. PTP-amplitude C2/C3 vs. C6/C7, p = 0.026) in contrast to controls (p = 1.00). CONCLUSION This study revealed the nature and extends of mechanical stress on the entire cervical spinal cord tissue due to focal stenosis. These pathophysiological alterations of spinal cord motion can be expected to be clinically relevant.
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Affiliation(s)
- Katharina Wolf
- Department of Neurology and Neurophysiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany.
| | - Marco Reisert
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Saúl Felipe Beltrán
- Department of Neurology and Neurophysiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Jan-Helge Klingler
- Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Ulrich Hubbe
- Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Karl Egger
- Department of Neuroradiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; Department of Radiology, Tauernklinikum Zell am See/Mittersill, Salzburg, Austria
| | - Marc Hohenhaus
- Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
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Braig M, Menza M, Leupold J, LeVan P, Feng L, Ko CW, von Zur Mühlen C, Krafft AJ, Hennig J, von Elverfeldt D. Analysis of accelerated 4D flow MRI in the murine aorta by radial acquisition and compressed sensing reconstruction. NMR Biomed 2020; 33:e4394. [PMID: 32815236 DOI: 10.1002/nbm.4394] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 07/15/2020] [Accepted: 07/25/2020] [Indexed: 06/11/2023]
Abstract
Preclinical 4D flow MRI remains challenging and is restricted for parallel imaging acceleration due to the limited number of available receive channels. A radial acquisition with combined parallel imaging and temporal compressed sensing reconstruction was implemented to achieve accelerated preclinical 4D flow MRI. In order to increase the accuracy of the measured velocities, a quantitative evaluation of different temporal regularization weights for the compressed sensing reconstruction based on velocity instead of magnitude data is performed. A 3D radial retrospectively triggered phase contrast sequence with a combined parallel imaging and compressed sensing reconstruction with temporal regularization was developed. It was validated in a phantom and in vivo (C57BL/6 J mice), against an established fully sampled Cartesian sequence. Different undersampling factors (USFs [12, 15, 20, 30, 60]) were evaluated, and the effect of undersampling was analyzed in detail for magnitude and velocity data. Temporal regularization weights λ were evaluated for different USFs. Acceleration factors of up to 20 compared with full Nyquist sampling were achieved. The peak flow differences compared with the Cartesian measurement were the following: USF 12, 3.38%; USF 15, 4.68%; USF 20, 0.95%. The combination of 3D radial center-out trajectories and compressed sensing reconstruction is robust against motion and flow artifacts and can significantly reduce measurement time to 30 min at a resolution of 180 μm3 . Concisely, radial acquisition with combined compressed sensing and parallel imaging proved to be an excellent method for analyzing complex flow patterns in mice.
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Affiliation(s)
- Moritz Braig
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marius Menza
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jochen Leupold
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Pierre LeVan
- Departments of Radiology and Paediatrics, Cumming School of Medicine, University of Calgary, Calgary, Canada
- Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Canada
| | - Li Feng
- Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York
| | - Cheng-Wen Ko
- Department of Computer Science and Engineering, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Constantin von Zur Mühlen
- Department of Cardiology and Angiology I, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Juergen Hennig
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Dominik von Elverfeldt
- Department of Radiology Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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9
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Wolf K, Krafft AJ, Egger K, Klingler JH, Hubbe U, Reisert M, Hohenhaus M. Assessment of spinal cord motion as a new diagnostic MRI-parameter in cervical spinal canal stenosis: study protocol on a prospective longitudinal trial. J Orthop Surg Res 2019; 14:321. [PMID: 31606049 PMCID: PMC6790032 DOI: 10.1186/s13018-019-1381-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 09/16/2019] [Indexed: 01/28/2023] Open
Abstract
Background Increased spinal cord motion has been proven to be a relevant finding within spinal canal stenosis disclosed by phase-contrast MRI (PC-MRI). Adapted PC-MRI is a suitable and reliable method within the well deliberated setting. As the decision between conservative and operative treatment can be challenging in some cases, further diagnostic marker would facilitate the diagnostic process. We hypothesize that increased spinal cord motion will correlate to clinical course and functional impairment and will contribute as a new diagnostic marker. Methods A monocentric, prospective longitudinal observational trial on cervical spinal canal stenosis will be conducted at the University Medical Center Freiburg. Patients (n = 130) with relevant cervical spinal canal stenosis, being defined by at least contact to the spinal cord, will be included. Also, we will examine a control group of healthy volunteers (n = 20) as proof-of-principle. We will observe two openly assigned branches of participants undergoing conservative and surgical decompressive treatment (based on current German Guidelines) over a time course of 12 month, including a total of 4 visits. We will conduct a broad assessment of clinical parameters, standard scores and gradings, electrophysiological measurements, standard MRI, and adapted functional PC-MRI of spinal cord motion. Primary endpoint is the evaluation of an expected negative correlation of absolute spinal cord displacement to clinical impairment. Secondary endpoints are the evaluation of positive correlation of increased absolute spinal cord displacement to prolonged evoked potentials, prediction of clinical course by absolute spinal cord displacement, and demonstration of normalized spinal cord motion after decompressive surgery. Discussion With the use of adapted, non-invasive PC-MRI as a quantitative method for assessment of spinal cord motion, further objective diagnostic information can be gained, that might improve the therapeutic decision-making process. This study will offer the needed data in order to establish PC-MRI on spinal cord motion within the diagnostic work-up of patients suffering from spinal canal stenosis. Trial registration German Clinical Trials Register, ID: DRKS00012962, Register date 2018/01/17
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Affiliation(s)
- Katharina Wolf
- Department of Neurology and Neurophysiology, Faculty of Medicine, University of Freiburg, Breisacher Straße 64, 79106, Freiburg, Germany.
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Karl Egger
- Department of Neuroradiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jan-Helge Klingler
- Department of Neurosurgery, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ulrich Hubbe
- Department of Neurosurgery, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marco Reisert
- Department of Radiology, Medical Physics, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marc Hohenhaus
- Department of Neurosurgery, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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10
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Shokina N, Bauer A, Teschner G, Buchenberg WB, Tropea C, Egger H, Hennig J, Krafft AJ. MR-based wall shear stress measurements in fully developed turbulent flow using the Clauser plot method. J Magn Reson 2019; 305:16-21. [PMID: 31158791 DOI: 10.1016/j.jmr.2019.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/21/2019] [Accepted: 05/24/2019] [Indexed: 06/09/2023]
Abstract
In arterial blood flow wall shear stress (WSS) quantifies the frictional force that flowing blood exerts on a vessel wall. WSS can be directly estimated from phase-contrast (PC) MR velocity measurements and has been suggested as a biomarker in cardio-vascular diseases. We present and investigate the application of the Clauser plot method for estimating WSS in fully developed turbulent stationary flow using PC velocity measurements. The Clauser plot method estimates WSS from the logarithmic region of boundary layer in fully developed turbulent stationary flow. The Clauser plot method was evaluated using 2D PC-MR phantom measurements at 3 T for different in-plane resolutions at various Reynolds numbers. WSS values derived from the Clauser plot were compared to results from Laser Doppler Velocimetry (LDV) measurements and theoretical results calculated using the friction factor formula for smooth pipe flow. For all Reynolds numbers, WSS values derived from the Clauser plot were in good agreement with results from LDV measurements and values using the friction factor formula (relative deviations ∼5%). Furthermore, Clauser plot derived results were almost independent of spatial resolution, in contrast to WSS results obtained with our in-house software tool for MR-based WSS quantification showing relative deviations of more than 100%. In fully developed turbulent flow, the Clauser plot method provides highly consistent WSS independent of the underlying spatial resolution. Therefore, it renders a valuable approach for MR-based WSS estimates in controllable flow settings. Although its direct in vivo applicability is severely limited because of the different flow character, it may serve as helpful approach for validation of MR-based WSS quantification algorithms prior to their clinical application.
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Affiliation(s)
- Nina Shokina
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany.
| | - Andreas Bauer
- Institute for Fluid Mechanics and Aerodynamics, Department of Mechanical Engineering, Technische Universität Darmstadt, Darmstadt, Germany
| | - Gabriel Teschner
- Institute for Numerical Analysis and Scientific Computing, Department of Mathematics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Waltraud B Buchenberg
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Cameron Tropea
- Institute for Fluid Mechanics and Aerodynamics, Department of Mechanical Engineering, Technische Universität Darmstadt, Darmstadt, Germany
| | - Herbert Egger
- Institute for Numerical Analysis and Scientific Computing, Department of Mathematics, Technische Universität Darmstadt, Darmstadt, Germany
| | - Jürgen Hennig
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
| | - Axel J Krafft
- Dept. of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany
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11
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Heidt T, Reiss S, Krafft AJ, Özen AC, Lottner T, Hehrlein C, Galmbacher R, Kayser G, Hilgendorf I, Stachon P, Wolf D, Zirlik A, Düring K, Zehender M, Meckel S, von Elverfeldt D, Bode C, Bock M, von Zur Mühlen C. Real-time magnetic resonance imaging - guided coronary intervention in a porcine model. Sci Rep 2019; 9:8663. [PMID: 31209241 PMCID: PMC6572773 DOI: 10.1038/s41598-019-45154-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 06/03/2019] [Indexed: 11/28/2022] Open
Abstract
X-ray fluoroscopy is the gold standard for coronary diagnostics and intervention. Magnetic resonance imaging is a radiation-free alternative to x-ray with excellent soft tissue contrast in arbitrary slice orientation. Here, we assessed real-time MRI-guided coronary interventions from femoral access using newly designed MRI technologies. Six Goettingen minipigs were used to investigate coronary intervention using real-time MRI. Catheters were custom-designed and equipped with an active receive tip-coil to improve visibility and navigation capabilities. Using modified standard clinical 5 F catheters, intubation of the left coronary ostium was successful in all animals. For the purpose of MR-guided coronary interventions, a custom-designed 8 F catheter was used. In spite of the large catheter size, and therefore limited steerability, intubation of the left coronary ostium was successful in 3 of 6 animals within seconds. Thereafter, real-time guided implantation of a non-metallic vascular scaffold into coronary arteries was possible. This study demonstrates that real-time MRI-guided coronary catheterization and intervention via femoral access is possible without the use of any contrast agents or radiation, including placement of non-metallic vascular scaffolds into coronary arteries. Further development, especially in catheter and guidewire technology, will be required to drive forward routine MR-guided coronary interventions as an alternative to x-ray fluoroscopy.
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Affiliation(s)
- Timo Heidt
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany.
| | - Simon Reiss
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Ali Caglar Özen
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Thomas Lottner
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Christoph Hehrlein
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Roland Galmbacher
- Department of Experimental Anesthesiology, University Hospital Heidelberg, Heidelberg, Germany
| | - Gian Kayser
- Department of Pathology, Institute of Surgical Pathology, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Ingo Hilgendorf
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Peter Stachon
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Dennis Wolf
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Andreas Zirlik
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | | | - Manfred Zehender
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Stephan Meckel
- Department of Neuroradiology, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Dominik von Elverfeldt
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Christoph Bode
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
| | - Michael Bock
- Department of Radiology, Medical Physics, University Medical Center Freiburg, Faculty of Medicine, Freiburg, Germany
| | - Constantin von Zur Mühlen
- Cardiology and Angiology I, Heart Center Freiburg University and Faculty of Medicine, Freiburg, Germany
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12
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Tipirneni-Sajja A, Krafft AJ, Loeffler RB, Song R, Bahrami A, Hankins JS, Hillenbrand CM. Autoregressive moving average modeling for hepatic iron quantification in the presence of fat. J Magn Reson Imaging 2019; 50:1620-1632. [PMID: 30761652 DOI: 10.1002/jmri.26682] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 01/28/2019] [Accepted: 01/29/2019] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Measuring hepatic R2* by fitting a monoexponential model to the signal decay of a multigradient-echo (mGRE) sequence noninvasively determines hepatic iron content (HIC). Concurrent hepatic steatosis introduces signal oscillations and confounds R2* quantification with standard monoexponential models. PURPOSE To evaluate an autoregressive moving average (ARMA) model for accurate quantification of HIC in the presence of fat using biopsy as the reference. STUDY TYPE Phantom study and in vivo cohort. POPULATION Twenty iron-fat phantoms covering clinically relevant R2* (30-800 s-1 ) and fat fraction (FF) ranges (0-40%), and 10 patients (four male, six female, mean age 18.8 years). FIELD STRENGTH/SEQUENCE 2D mGRE acquisitions at 1.5 T and 3 T. ASSESSMENT Phantoms were scanned at both field strengths. In vivo data were analyzed using the ARMA model to determine R2* and FF values, and compared with biopsy results. STATISTICAL TESTS Linear regression analysis was used to compare ARMA R2* and FF results with those obtained using a conventional monoexponential model, complex-domain nonlinear least squares (NLSQ) fat-water model, and biopsy. RESULTS In phantoms and in vivo, all models produced R2* and FF values consistent with expected values in low iron and low/high fat conditions. For high iron and no fat phantoms, monoexponential and ARMA models performed excellently (slopes: 0.89-1.07), but NLSQ overestimated R2* (slopes: 1.14-1.36) and produced false FFs (12-17%) at 1.5 T; in high iron and fat phantoms, NLSQ (slopes: 1.02-1.16) outperformed monoexponential and ARMA models (slopes: 1.23-1.88). The results with NLSQ and ARMA improved in phantoms at 3 T (slopes: 0.96-1.04). In patients, mean R2*-HIC estimates for monoexponential and ARMA models were close to biopsy-HIC values (slopes: 0.90-0.95), whereas NLSQ substantially overestimated HIC (slope 1.4) and produced false FF values (4-28%) with very high SDs (15-222%) in patients with high iron overload and no steatosis. DATA CONCLUSION ARMA is superior in quantifying R2* and FF under high iron and no fat conditions, whereas NLSQ is superior for high iron and concurrent fat at 1.5 T. Both models give improved R2* and FF results at 3 T. LEVEL OF EVIDENCE 2 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:1620-1632.
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Affiliation(s)
- Aaryani Tipirneni-Sajja
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Biomedical Engineering, University of Memphis, Memphis, Tennessee, USA
| | - Axel J Krafft
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ralf B Loeffler
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ruitian Song
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Armita Bahrami
- Department of Pathology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Claudia M Hillenbrand
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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13
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Tipirneni-Sajja A, Loeffler RB, Krafft AJ, Sajewski AN, Ogg RJ, Hankins JS, Hillenbrand CM. Ultrashort echo time imaging for quantification of hepatic iron overload: Comparison of acquisition and fitting methods via simulations, phantoms, and in vivo data. J Magn Reson Imaging 2018; 49:1475-1488. [PMID: 30358001 DOI: 10.1002/jmri.26325] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 08/13/2018] [Accepted: 08/13/2018] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Current R2*-MRI techniques for measuring hepatic iron content (HIC) use various acquisition types and fitting models. PURPOSE To evaluate the accuracy and precision of R2*-HIC acquisition and fitting methods. STUDY TYPE Signal simulations, phantom study, and prospective in vivo cohort. POPULATION In all, 132 patients (58/74 male/female, mean age 17.7 years). FIELD STRENGTH/SEQUENCE 2D-multiecho gradient-echo (GRE) and ultrashort echo time (UTE) acquisitions at 1.5T. ASSESSMENT Synthetic MR signals were created to mimic published GRE and UTE methods, using different R2* values (25-2000 s-1 ) and signal-to-noise ratios (SNR). Phantoms with varying iron concentrations were scanned at 1.5T. In vivo data were analyzed from 132 patients acquired at 1.5T. R2* was estimated by fitting using three signal models. Accuracy and precision of R2* measurements for UTE acquisition parameters (SNR, echo spacing [ΔTE], maximum echo time [TEmax ]) and fitting methods were compared for simulated, phantom, and in vivo datasets. STATISTICAL TESTS R2* accuracy was determined from the relative error and by linear regression analysis. Precision was evaluated using coefficient of variation (CoV) analysis. RESULTS In simulations, all models had high R2* accuracy (error <5%) and precision (CoV <10%) for all SNRs, shorter ΔTE (≤0.5 msec), and longer TEmax (≥10.1 msec); except the constant offset model overestimated R2* at the lowest SNR. In phantoms and in vivo, all models produced similar R2* values for different SNRs and shorter ΔTEs (slopes: 0.99-1.06, R2 > 0.99, P < 0.001). In all experiments, R2* results degraded for high R2* values with longer ΔTE (≥1 msec). In vivo, shorter and longer TEmax gave similar R2* results (slopes: 1.02-1.06, R2 > 0.99, P < 0.001) for the noise subtraction model for 25≤R2*≤2000 s-1 . However, both quadratic and constant offset models, using shorter TEmax (≤4.7 msec) overestimated R2* and yielded high CoVs up to ∼170% for low R2* (<250 s-1 ). DATA CONCLUSION UTE with TEmax ≥ 10.1 msec and ΔTE ≤ 0.5 msec yields accurate R2* estimates over the entire clinical HIC range. Monoexponential fitting with noise subtraction is the most robust signal model to changes in UTE parameters and achieves the highest R2* accuracy and precision. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1475-1488.
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Affiliation(s)
- Aaryani Tipirneni-Sajja
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Biomedical Engineering, The University of Memphis, Memphis, Tennessee, USA
| | - Ralf B Loeffler
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Axel J Krafft
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Andrea N Sajewski
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Robert J Ogg
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Claudia M Hillenbrand
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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Kaufhold L, Harloff A, Schumann C, Krafft AJ, Hennig J, Hennemuth A. Image-based assessment of uncertainty in quantification of carotid lumen. J Med Imaging (Bellingham) 2018; 5:034003. [PMID: 30840745 PMCID: PMC6152582 DOI: 10.1117/1.jmi.5.3.034003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/31/2018] [Indexed: 09/01/2023] Open
Abstract
Measurements of the vessel lumen diameter are often used to determine the degree of atherosclerotic disease in carotid arteries. However, quantification results vary with imaging technique and acquisition settings. We aim at providing a tool that quantifies the lumen diameter on different image datasets and gives an estimate of quantification uncertainties, so that they can be taken into consideration when evaluating and comparing measurements. For the segmentation of the vessel lumen, we present an algorithm using ray-casting techniques and partial volume correction. We furthermore propose a scheme for the analysis and exploration of the lumen diameter. Finally, we present a clinically relevant application scenario, in which we explore agreement between lumen diameter estimations in corresponding computed tomography angiography, contrast-enhanced magnetic resonance angiography, time-of-flight, and subtraction images of carotid vessels with severe carotid atherosclerotic plaques.
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Affiliation(s)
- Lilli Kaufhold
- Fraunhofer MEVIS, Bremen, Germany
- Charité-Universitaetsmedizin Berlin, Berlin, Germany
| | - Andreas Harloff
- Medical Center—University of Freiburg, Department of Neurology and Neurophysiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Axel J. Krafft
- Medical Center—University of Freiburg, Department of Radiology—Medical Physics, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Juergen Hennig
- Medical Center—University of Freiburg, Department of Radiology—Medical Physics, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Anja Hennemuth
- Fraunhofer MEVIS, Bremen, Germany
- Charité-Universitaetsmedizin Berlin, Berlin, Germany
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von zur Mühlen C, Reiss S, Krafft AJ, Besch L, Menza M, Zehender M, Heidt T, Maier A, Pfannebecker T, Zirlik A, Reinöhl J, Stachon P, Hilgendorf I, Wolf D, Diehl P, Wengenmayer T, Ahrens I, Bode C, Bock M. Coronary magnetic resonance imaging after routine implantation of bioresorbable vascular scaffolds allows non-invasive evaluation of vascular patency. PLoS One 2018; 13:e0191413. [PMID: 29370208 PMCID: PMC5784929 DOI: 10.1371/journal.pone.0191413] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/04/2018] [Indexed: 12/17/2022] Open
Abstract
Background Evaluation of recurrent angina after percutaneous coronary interventions is challenging. Since bioresorbable vascular scaffolds (BVS) cause no artefacts in magnetic resonance imaging (MRI) due to their polylactate-based backbone, evaluation of vascular patency by MRI might allow for non-invasive assessment and triage of patients with suspected BVS failure. Methods Patients with polylactate-based ABSORB-BVS in proximal coronary segments were examined with 3 Tesla MRI directly (baseline) and one year after implantation. For assessment of coronary patency, a high-resolution 3D spoiled gradient echo pulse sequence with fat-saturation, T2-preparation (TE: 40 ms), respiratory and end-diastolic cardiac gating, and a spatial resolution of (1.08 mm)3 was positioned parallel to the course of the vessel for bright blood imaging. In addition, a 3D navigator-gated T2-weighted variable flip angle turbo spin echo (TSE) sequence with dual-inversion recovery black-blood preparation and elliptical k-space coverage was applied with a voxel size of (1.14 mm)3. For quantitative evaluation lumen diameters of the scaffolded areas were measured in reformatted bright and black blood MR angiography data. Results 11 patients with implantation of 16 BVS in the proximal coronary segments were included, of which none suffered from major adverse cardiac events during the one year follow up. Vascular patency in all segments implanted with BVS could be reliably assessed by MRI at baseline and after one year, whereas segments with metal stents could not be evaluated due to artefacts. Luminal diameter within the BVS remained constant during the one year period. One patient with atypical angina after BVS implantation was noninvasively evaluated showing a patent vessel, also confirmed by coronary angiography. Conclusions Coronary MRI allows contrast-agent free and non-invasive assessment of vascular patency after ABSORB-BVS implantation. This approach might be supportive in the triage and improvement of diagnostic workflows in patients with postinterventional angina and scaffold implantation. Trial registration German Register of Clinical Studies DRKS00007456
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Affiliation(s)
- Constantin von zur Mühlen
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- * E-mail:
| | - Simon Reiss
- Department of Radiology–Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Axel J. Krafft
- Department of Radiology–Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Lisa Besch
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marius Menza
- Department of Radiology–Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Manfred Zehender
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Timo Heidt
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Alexander Maier
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | | | - Andreas Zirlik
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jochen Reinöhl
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Peter Stachon
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ingo Hilgendorf
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Dennis Wolf
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Philipp Diehl
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tobias Wengenmayer
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ingo Ahrens
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Christoph Bode
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Michael Bock
- Department of Cardiology and Angiology I, Heart Center Freiburg University, Faculty of Medicine, University of Freiburg, Freiburg, Germany
- Department of Radiology–Medical Physics, University Medical Center Freiburg, Freiburg, Germany
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Johnston CM, Krafft AJ, Russe MF, Rog-Zielinska EA. A new look at the heart-novel imaging techniques. Herzschrittmacherther Elektrophysiol 2017; 29:14-23. [PMID: 29242981 DOI: 10.1007/s00399-017-0546-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 11/24/2017] [Indexed: 01/20/2023]
Abstract
The development and successful implementation of cutting-edge imaging technologies to visualise cardiac anatomy and function is a key component of effective diagnostic efforts in cardiology. Here, we describe a number of recent exciting advances in the field of cardiology spanning from macro- to micro- to nano-scales of observation, including magnetic resonance imaging, computed tomography, optical mapping, photoacoustic imaging, and electron tomography. The methodologies discussed are currently making the transition from scientific research to routine clinical use, albeit at different paces. We discuss the most likely trajectory of this transition into clinical research and standard diagnostics, and highlight the key challenges and opportunities associated with each of the methodologies.
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Affiliation(s)
- C M Johnston
- Institute for Experimental Cardiovascular Medicine, University Heart Center, Medical Center - University of Freiburg, and Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - A J Krafft
- Department of Radiology, Medical Physics, Medical Center - Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - M F Russe
- Department of Radiology, Medical Center - Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - E A Rog-Zielinska
- Institute for Experimental Cardiovascular Medicine, University Heart Center, Medical Center - University of Freiburg, and Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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17
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Schleicher KE, Bock M, Düring K, Kroboth S, Krafft AJ. Radial MRI with variable echo times: reducing the orientation dependency of susceptibility artifacts of an MR-safe guidewire. MAGMA 2017; 31:235-242. [PMID: 28770356 DOI: 10.1007/s10334-017-0645-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 07/20/2017] [Accepted: 07/21/2017] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Guidewires are indispensable tools for intravascular MR-guided interventions. Recently, an MR-safe guidewire made from a glass-fiber/epoxy compound material with embedded iron particles was developed. The size of the induced susceptibility artifact, and thus the guidewire's visibility, depends on its orientation against B 0. We present a radial acquisition scheme with variable echo times that aims to reduce the artifact's orientation dependency. MATERIALS AND METHODS The radial acquisition scheme uses sine-squared modulated echo times depending on the physical direction of the spoke to balance the susceptibility artifact of the guidewire. The acquisition scheme was studied in simulations based on dipole fields and in phantom experiments for different orientations of the guidewire against B 0. The simulated and measured artifact widths were quantitatively compared. RESULTS Compared to acquisitions with non-variable echo times, the proposed acquisition scheme shows a reduced angular variability. For the two main orientations (i.e., parallel and perpendicular to B 0), the ratio of the artifact widths was reduced from about 2.2 (perpendicular vs. parallel) to about 1.2 with the variable echo time approach. CONCLUSION The reduction of the orientation dependency of the guidewire's artifact via sine-squared varying echo times could be verified in simulations and measurements. The more balanced artifact allows for a better overall visibility of the guidewire.
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Affiliation(s)
- Katharina E Schleicher
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany.
| | - Michael Bock
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | | | - Stefan Kroboth
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology, Medical Physics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Breisacher Strasse 60a, 79106, Freiburg, Germany
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18
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Krafft AJ, Loeffler RB, Song R, Tipirneni-Sajja A, McCarville MB, Robson MD, Hankins JS, Hillenbrand CM. Quantitative ultrashort echo time imaging for assessment of massive iron overload at 1.5 and 3 Tesla. Magn Reson Med 2017; 78:1839-1851. [PMID: 28090666 DOI: 10.1002/mrm.26592] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 01/12/2023]
Abstract
PURPOSE Hepatic iron content (HIC) quantification via transverse relaxation rate (R2*)-MRI using multi-gradient echo (mGRE) imaging is compromised toward high HIC or at higher fields due to the rapid signal decay. Our study aims at presenting an optimized 2D ultrashort echo time (UTE) sequence for R2* quantification to overcome these limitations. METHODS Two-dimensional UTE imaging was realized via half-pulse excitation and radial center-out sampling. The sequence includes chemically selective saturation pulses to reduce streaking artifacts from subcutaneous fat, and spatial saturation (sSAT) bands to suppress out-of-slice signals. The sequence employs interleaved multi-echo readout trains to achieve dense temporal sampling of rapid signal decays. Evaluation was done at 1.5 Tesla (T) and 3T in phantoms, and clinical applicability was demonstrated in five patients with biopsy-confirmed massively high HIC levels (>25 mg Fe/g dry weight liver tissue). RESULTS In phantoms, the sSAT pulses were found to remove out-of-slice contamination, and R2* results were in excellent agreement to reference mGRE R2* results (slope of linear regression: 1.02/1.00 for 1.5/3T). UTE-based R2* quantification in patients with massive iron overload proved successful at both field strengths and was consistent with biopsy HIC values. CONCLUSION The UTE sequence provides a means to measure R2* in patients with massive iron overload, both at 1.5T and 3T. Magn Reson Med 78:1839-1851, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Axel J Krafft
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ralf B Loeffler
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ruitian Song
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Aaryani Tipirneni-Sajja
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - M Beth McCarville
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Matthew D Robson
- OCMR, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Claudia M Hillenbrand
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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19
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Loeffler RB, McCarville MB, Wagstaff AW, Smeltzer MP, Krafft AJ, Song R, Hankins JS, Hillenbrand CM. Can multi-slice or navigator-gated R2* MRI replace single-slice breath-hold acquisition for hepatic iron quantification? Pediatr Radiol 2017; 47:46-54. [PMID: 27752732 PMCID: PMC5203961 DOI: 10.1007/s00247-016-3700-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 07/21/2016] [Accepted: 08/26/2016] [Indexed: 11/25/2022]
Abstract
BACKGROUND Liver R2* values calculated from multi-gradient echo (mGRE) magnetic resonance images (MRI) are strongly correlated with hepatic iron concentration (HIC) as shown in several independently derived biopsy calibration studies. These calibrations were established for axial single-slice breath-hold imaging at the location of the portal vein. Scanning in multi-slice mode makes the exam more efficient, since whole-liver coverage can be achieved with two breath-holds and the optimal slice can be selected afterward. Navigator echoes remove the need for breath-holds and allow use in sedated patients. OBJECTIVE To evaluate if the existing biopsy calibrations can be applied to multi-slice and navigator-controlled mGRE imaging in children with hepatic iron overload, by testing if there is a bias-free correlation between single-slice R2* and multi-slice or multi-slice navigator controlled R2*. MATERIALS AND METHODS This study included MRI data from 71 patients with transfusional iron overload, who received an MRI exam to estimate HIC using gradient echo sequences. Patient scans contained 2 or 3 of the following imaging methods used for analysis: single-slice images (n = 71), multi-slice images (n = 69) and navigator-controlled images (n = 17). Small and large blood corrected region of interests were selected on axial images of the liver to obtain R2* values for all data sets. Bland-Altman and linear regression analysis were used to compare R2* values from single-slice images to those of multi-slice images and navigator-controlled images. RESULTS Bland-Altman analysis showed that all imaging method comparisons were strongly associated with each other and had high correlation coefficients (0.98 ≤ r ≤ 1.00) with P-values ≤0.0001. Linear regression yielded slopes that were close to 1. CONCLUSION We found that navigator-gated or breath-held multi-slice R2* MRI for HIC determination measures R2* values comparable to the biopsy-validated single-slice, single breath-hold scan. We conclude that these three R2* methods can be interchangeably used in existing R2*-HIC calibrations.
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Affiliation(s)
- Ralf B Loeffler
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA
| | - M Beth McCarville
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA
| | - Anne W Wagstaff
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA
- Rhodes College, Memphis, TN, USA
- University of Alabama at Birmingham School of Medicine, Birmingham, AL, USA
| | - Matthew P Smeltzer
- Department of Biostatistics, St. Jude Children's Research Hospital, Memphis, TN, USA
- Division of Epidemiology, Biostatistics, and Environmental Health, School of Public Health, University of Memphis, Memphis, TN, USA
| | - Axel J Krafft
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA
- Department of Radiology, University Hospital Center Freiburg, Freiburg, Germany
| | - Ruitian Song
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Claudia M Hillenbrand
- Diagnostic Imaging, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105-3678, USA.
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20
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Mitrea BG, Krafft AJ, Song R, Loeffler RB, Hillenbrand CM. Paired self-compensated spin-lock preparation for improved T1ρ quantification. J Magn Reson 2016; 268:49-57. [PMID: 27161095 DOI: 10.1016/j.jmr.2016.04.017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 04/28/2016] [Accepted: 04/29/2016] [Indexed: 06/05/2023]
Abstract
PURPOSE Spin-lock (SL) imaging allows quantification of the spin-lattice relaxation time in the rotating frame (T1ρ). B0 and B1 inhomogeneities impact T1ρ quantification because the preparatory block in SL imaging is sensitive to the field heterogeneities. Here, a modified preparatory block (PSC-SL) is proposed that attempts to alleviate SL sensitivity to field inhomogeneities in scenarios where existing approaches fail, i.e. high SL frequencies. METHODS Computer simulations, phantom and in vivo experiments were used to determine the effect of field inhomogeneities on T1ρ quantification. Existing SL preparations were compared with PSC-SL in different conditions to assess the advantages and disadvantages of each method. RESULTS Phantom experiments and computer modeling demonstrate that PSC-SL provides superior T1ρ quantification at high SL frequencies in situations where the existing SL preparation methods fail. This result has been confirmed in pre-clinical neuro and body imaging at 7T. CONCLUSION PSC-SL complements existing methods by increasing the accuracy of T1ρ quantification at high spin-lock frequencies when large field inhomogeneities are present. A-priory information about the experimental conditions such, as field distribution and spinlock frequency are useful for selecting an appropriate spin-lock preparation for specific applications.
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Affiliation(s)
- Bogdan G Mitrea
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Axel J Krafft
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Ruitian Song
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Ralf B Loeffler
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Claudia M Hillenbrand
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, TN, USA.
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21
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Kalis IM, Pilutti D, Krafft AJ, Hennig J, Bock M. Prospective MR image alignment between breath-holds: Application to renal BOLD MRI. Magn Reson Med 2016; 77:1573-1582. [PMID: 27099024 DOI: 10.1002/mrm.26247] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Revised: 03/02/2016] [Accepted: 03/25/2016] [Indexed: 11/10/2022]
Abstract
PURPOSE To present an image registration method for renal blood oxygen level-dependent (BOLD) measurements that enables semiautomatic assessment of parenchymal and medullary R2* changes under a functional challenge. METHODS In a series of breath-hold acquisitions, three-dimensional data were acquired initially for prospective image registration of subsequent BOLD measurements. An algorithm for kidney alignment for BOLD renal imaging (KALIBRI) was implemented to detect the positions of the left and right kidney so that the kidneys were acquired in the subsequent BOLD measurement at consistent anatomical locations. Residual in-plane distortions were corrected retrospectively so that semiautomatic dynamic R2* measurements of the renal cortex and medulla become feasible. KALIBRI was tested in six healthy volunteers during a series of BOLD experiments, which included a 600- to 1000-mL water challenge. RESULTS Prospective image registration and BOLD imaging of each kidney was achieved within a total measurement time of about 17 s, enabling its execution within a single breath-hold. KALIBRI improved the registration by up to 35% as found with mutual information measures. In four volunteers, a medullary R2* decrease of up to 40% was observed after water ingestion. CONCLUSION KALIBRI improves the quality of two-dimensional time-resolved renal BOLD MRI by aligning local renal anatomy, which allows for consistent R2* measurements over many breath-holds. Magn Reson Med 77:1573-1582, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Inge M Kalis
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - David Pilutti
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Axel J Krafft
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany.,German Cancer Consortium, Heidelberg, Germany.,German Cancer Research Center, Heidelberg, Germany
| | - Jürgen Hennig
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
| | - Michael Bock
- Department of Radiology-Medical Physics, University Medical Center Freiburg, Freiburg, Germany
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22
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Reiss S, Krafft AJ, Zehender M, Heidt T, Pfannebecker T, Bode C, Bock M, von Zur Muhlen C. Magnetic resonance imaging of bioresorbable vascular scaffolds: potential approach for noninvasive evaluation of coronary patency. Circ Cardiovasc Interv 2016; 8:CIRCINTERVENTIONS.115.002388. [PMID: 25794509 DOI: 10.1161/circinterventions.115.002388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Simon Reiss
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Axel J Krafft
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Manfred Zehender
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Timo Heidt
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Thomas Pfannebecker
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Christoph Bode
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Michael Bock
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.)
| | - Constantin von Zur Muhlen
- From the Department of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany (S.R., A.J.K., M.B.); German Cancer Consortium (DKTK), Heidelberg, Germany (A.J.K.); Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany (A.J.K.); Department of Cardiology I, University Heart Center Freiburg, Freiburg, Germany (M.Z., T.H., C.B., C.v.z.M.); and ABBOTT Vascular, Wetzlar, Germany (T.P.).
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Krafft AJ, Loeffler RB, Song R, Bian X, McCarville MB, Hankins JS, Hillenbrand CM. Does fat suppression via chemically selective saturation affect R2*-MRI for transfusional iron overload assessment? A clinical evaluation at 1.5T and 3T. Magn Reson Med 2015; 76:591-601. [PMID: 26308155 DOI: 10.1002/mrm.25868] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 07/10/2015] [Accepted: 07/13/2015] [Indexed: 01/01/2023]
Abstract
PURPOSE Fat suppression (FS) via chemically selective saturation (CHESS) eliminates fat-water oscillations in multiecho gradient echo (mGRE) R2*-MRI. However, for increasing R2* values as seen with increasing liver iron content (LIC), the water signal spectrally overlaps with the CHESS band, which may alter R2*. We investigated the effect of CHESS on R2* and developed a heuristic correction for the observed CHESS-induced R2* changes. METHODS Eighty patients [female, n = 49; male, n = 31; mean age (± standard deviation), 18.3 ± 11.7 y] with iron overload were scanned with a non-FS and a CHESS-FS mGRE sequence at 1.5T and 3T. Mean liver R2* values were evaluated using three published fitting approaches. Measured and model-corrected R2* values were compared and statistically analyzed. RESULTS At 1.5T, CHESS led to a systematic R2* reduction (P < 0.001 for all fitting algorithms) especially toward higher R2*. Our model described the observed changes well and reduced the CHESS-induced R2* bias after correction (linear regression slopes: 1.032/0.927/0.981). No CHESS-induced R2* reductions were found at 3T. CONCLUSION The CHESS-induced R2* bias at 1.5T needs to be considered when applying R2*-LIC biopsy calibrations for clinical LIC assessment, which were established without FS at 1.5T. The proposed model corrects the R2* bias and could therefore improve clinical iron overload assessment based on linear R2*-LIC calibrations. Magn Reson Med 76:591-601, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Axel J Krafft
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ralf B Loeffler
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ruitian Song
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Xiao Bian
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Rhodes College, Memphis, Tennessee, USA
| | - M Beth McCarville
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Claudia M Hillenbrand
- Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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Zamecnik P, Schouten MG, Krafft AJ, Maier F, Schlemmer HP, Barentsz JO, Bock M, Fütterer JJ. Automated real-time needle-guide tracking for fast 3-T MR-guided transrectal prostate biopsy: a feasibility study. Radiology 2014; 273:879-86. [PMID: 25061830 DOI: 10.1148/radiol.14132067] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE To assess the feasibility of automatic needle-guide tracking by using a real-time phase-only cross correlation ( POCC phase-only cross correlation ) algorithm-based sequence for transrectal 3-T in-bore magnetic resonance (MR)-guided prostate biopsies. MATERIALS AND METHODS This study was approved by the ethics review board, and written informed consent was obtained from all patients. Eleven patients with a prostate-specific antigen level of at least 4 ng/mL (4 μg/L) and at least one transrectal ultrasonography-guided biopsy session with negative findings were enrolled. Regions suspicious for cancer were identified on 3-T multiparametric MR images. During a subsequent MR-guided biopsy, the regions suspicious for cancer were reidentified and targeted by using the POCC phase-only cross correlation -based tracking sequence. Besides testing a general technical feasibility of the biopsy procedure by using the POCC phase-only cross correlation -based tracking sequence, the procedure times were measured, and a pathologic analysis of the biopsy cores was performed. RESULTS Thirty-eight core samples were obtained from 25 regions suspicious for cancer. It was technically feasible to perform the POCC phase-only cross correlation -based biopsies in all regions suspicious for cancer in each patient, with adequate biopsy samples obtained with each biopsy attempt. The median size of the region suspicious for cancer was 8 mm (range, 4-13 mm). In each region suspicious for cancer (median number per patient, two; range, 1-4), a median of one core sample per region was obtained (range, 1-3). The median time for guidance per target was 1.5 minutes (range, 0.7-5 minutes). Nineteen of 38 core biopsy samples contained cancer. CONCLUSION This study shows that it is feasible to perform transrectal 3-T MR-guided biopsies by using a POCC phase-only cross correlation algorithm-based real-time tracking sequence.
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Affiliation(s)
- Patrik Zamecnik
- From the Department of Radiology, St Radboud University Nijmegen Medical Center, UMC St Radboud, Internal Post Code 766, Postbus 9101, Geert Grooteplein 10, 6500 HB Nijmegen, the Netherlands (P.Z., M.G.S., J.O.B., J.J.F.); Department of Radiological Sciences, St Jude Children's Research Hospital, Memphis, Tenn (A.J.K.); Department of Imaging Physics, University of Texas-MD Anderson Cancer Center, Houston, Tex (F.M.); Department of Radiology, German Cancer Research Center, Heidelberg, Germany (H.P.S.); Department of Radiology, Division of Medical Physics, University of Freiburg, Freiburg, Germany (M.B.); and MIRA Institute for Biomedical Technology and Technical Medicine, University of Twente, Enschede, the Netherlands (J.J.F.)
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Krafft AJ, Rauschenberg J, Maier F, Jenne JW, Bock M. Crushed rephased orthogonal slice selection (CROSS) for simultaneous acquisition of two orthogonal proton resonance frequency temperature maps. J Magn Reson Imaging 2013; 38:1510-20. [DOI: 10.1002/jmri.24118] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 02/15/2013] [Indexed: 01/05/2023] Open
Affiliation(s)
- Axel J Krafft
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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Rauschenberg J, Krafft AJ, Maier F, Zamecnik P, Semmler W, Bock M. Outer volume suppression in steady state sequences (OVSuSS) for percutaneous interventions. Magn Reson Med 2011; 66:123-34. [DOI: 10.1002/mrm.22789] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 11/25/2010] [Accepted: 12/02/2010] [Indexed: 11/10/2022]
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Zamecnik P, Krafft AJ, Maier F, de Oliveira A, Zechmann C, Winkel A, Schlemmer HP, Bock M. MR-gesteuerte laser-induzierte Thermoablation (LITT) von Leberläsionen unter Verwendung von Echtzeitsequenzen. ROFO-FORTSCHR RONTG 2010. [DOI: 10.1055/s-0030-1268298] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Krafft AJ, Jenne JW, Maier F, Stafford RJ, Huber PE, Semmler W, Bock M. A long arm for ultrasound: a combined robotic focused ultrasound setup for magnetic resonance-guided focused ultrasound surgery. Med Phys 2010; 37:2380-93. [PMID: 20527572 DOI: 10.1118/1.3377777] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Focused ultrasound surgery (FUS) is a highly precise noninvasive procedure to ablate pathogenic tissue. FUS therapy is often combined with magnetic resonance (MR) imaging as MR imaging offers excellent target identification and allows for continuous monitoring of FUS induced temperature changes. As the dimensions of the ultrasound (US) focus are typically much smaller than the targeted volume, multiple sonications and focus repositioning are interleaved to scan the focus over the target volume. Focal scanning can be achieved electronically by using phased-array US transducers or mechanically by using dedicated mechanical actuators. In this study, the authors propose and evaluate the precision of a combined robotic FUS setup to overcome some of the limitations of the existing MRgFUS systems. Such systems are typically integrated into the patient table of the MR scanner and thus only provide an application of the US wave within a limited spatial range from below the patient. METHODS The fully MR-compatible robotic assistance system InnoMotion (InnoMedic GmbH, Herxheim, Germany) was originally designed for MR-guided interventions with needles. It offers five pneumatically driven degrees of freedom and can be moved over a wide range within the bore of the magnet. In this work, the robotic system was combined with a fixed-focus US transducer (frequency: 1.7 MHz; focal length: 68 mm, and numerical aperture: 0.44) that was integrated into a dedicated, in-house developed treatment unit for FUS application. A series of MR-guided focal scanning procedures was performed in a polyacrylamide-egg white gel phantom to assess the positioning accuracy of the combined FUS setup. In animal experiments with a 3-month-old domestic pig, the system's potential and suitability for MRgFUS was tested. RESULTS In phantom experiments, a total targeting precision of about 3 mm was found, which is comparable to that of the existing MRgFUS systems. Focus positioning could be performed within a few seconds. During in vivo experiments, a defined pattern of single thermal lesions and a therapeutically relevant confluent thermal lesion could be created. The creation of local tissue necrosis by coagulation was confirmed by post-FUS MR imaging and histological examinations on the treated tissue sample. During all sonications in phantom and in vivo, reliable MR imaging and online MR thermometry could be performed without compromises due to operation of the combined robotic FUS setup. CONCLUSIONS Compared to the existing MRgFUS systems, the combined robotic FUS approach offers a wide range of spatial flexibility so that highly flexible application of the US wave would be possible, for example, to avoid risk structures within the US field. The setup might help to realize new ways of patient access in MRgFUS therapy. The setup is compatible with any closed-bore MR system and does not require an especially designed patient table.
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Affiliation(s)
- Axel J Krafft
- Department of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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