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Shahrouki P, Gupta R, Belani P, Chien A, Doshi AH, De Leacy R, Fifi JT, Mocco J, Nael K. Differential Subsampling with Cartesian Ordering-MRA for Classifying Residual Treated Aneurysms. AJNR Am J Neuroradiol 2022; 43:887-892. [PMID: 35672082 DOI: 10.3174/ajnr.a7532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2021] [Accepted: 04/14/2022] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Differential Subsampling with Cartesian Ordering (DISCO), an ultrafast high-spatial-resolution head MRA, has been introduced. We aimed to determine the diagnostic performance of DISCO-MRA in grading residual aneurysm in comparison with TOF-MRA in patients with treated intracranial aneurysms. MATERIALS AND METHODS Patients with endovascular treatment and having undergone DISCO-MRA, TOF-MRA, and DSA were included for review. The voxel size and acquisition time were 0.75 × 0.75 × 1 mm3/6 seconds for DISCO-MRA and 0.6 × 0.6 × 1 mm3/6 minutes for TOF-MRA. Residual aneurysms were determined using the Modified Raymond-Roy Classification on TOF-MRA and DISCO-MRA by 2 neuroradiologists independently and were compared against DSA as the reference standard. Statistical analysis was performed using the κ statistic and the χ2 test. RESULTS Sixty-eight treated intracranial aneurysms were included. The intermodality agreement was κ = 0.82 (95% CI, 0.67-0.97) between DISCO and DSA and 0.44 (95% CI, 0.28-0.61) between TOF and DSA. Modified Raymond-Roy Classification scores matched DSA scores in 60/68 cases (88%; χ2 = 144.4, P < .001 for DISCO and 46/68 cases (68%; χ2 = 65.0, P < .001) for TOF. The diagnostic accuracy for the detection of aneurysm remnants was higher for DISCO (0.96; 95% CI, 0.88-0.99) than for TOF (0.79; 95% CI, 0.68-0.88). CONCLUSIONS In patients with endovascularly treated intracranial aneurysms, DISCO-MRA provides superior diagnostic performance in comparison with TOF-MRA in delineating residual aneurysms in a fraction of the time.
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Affiliation(s)
- P Shahrouki
- From the Department of Radiological Sciences (P.S., A.C., K.N.), University of California Los Angeles, Los Angeles, California
| | - R Gupta
- Department of Radiology (R.G., P.B., A.D., K.N.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - P Belani
- Department of Radiology (R.G., P.B., A.D., K.N.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - A Chien
- From the Department of Radiological Sciences (P.S., A.C., K.N.), University of California Los Angeles, Los Angeles, California
| | - A H Doshi
- Department of Radiology (R.G., P.B., A.D., K.N.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - R De Leacy
- Department of Neurosurgery (R.D.L., J,F., J.M.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - J T Fifi
- Department of Neurosurgery (R.D.L., J,F., J.M.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - J Mocco
- Department of Neurosurgery (R.D.L., J,F., J.M.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
| | - K Nael
- From the Department of Radiological Sciences (P.S., A.C., K.N.), University of California Los Angeles, Los Angeles, California .,Department of Radiology (R.G., P.B., A.D., K.N.), Icahn School of Medicine at the Mount Sinai Hospital, New York, New York
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Nael K, Drummond J, Costa AB, De Leacy RA, Fung MM, Mocco J. Differential Subsampling with Cartesian Ordering for Ultrafast High-Resolution MRA in the Assessment of Intracranial Aneurysms. J Neuroimaging 2019; 30:40-44. [PMID: 31721362 DOI: 10.1111/jon.12677] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 10/29/2019] [Accepted: 10/29/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE We aimed to evaluate the feasibility of an ultrafast whole head contrast-enhanced MRA (CE-MRA) in morphometric assessment of intracranial aneurysms in comparison to routinely used time-of-flight (TOF)-MRA. METHODS In this prospective single institutional study, patients with known untreated intracranial aneurysm underwent MRA. Routine multislab TOF-MRA was obtained with a 3D voxel sizes of .6 × .6 × 1 (6-minute acquisition time). CE-MRA of whole head was obtained using Differential Subsampling with Cartesian Ordering (DISCO) and 2D Auto-calibrating Reconstruction for Cartesian imaging with a 3D voxel-sizes of .75 × .75 × 1 mm3 during a 6-second temporal resolution. Morphometric features of intracranial aneurysms, including size, aneurysm sac morphology, and the presence of intraluminal thrombosis, were assessed on both techniques. Statistical analysis was performed using a combination of Kappa test, Bland-Altman, and correlation coefficient analysis. RESULTS A total of 34 aneurysms in 28 patients were included. Aneurysm size measurements (mean ± SD) were similar between DISCO-MRA (4.1 ± 2.3 mm) and TOF-MRA (4.3 ± 2.8 mm) (P = .27). Bland-Altman analysis showed a mean difference of .4 mm and there was excellent correlation r = .91 (95% CI: .87-.96). In six aneurysms (17.6%), TOF-MRA was nonconfidant to exclude intraluminal thrombosis. In seven aneurysms (20%), TOF-MRA was unable or nonconfidant in depicting aneurysm sac morphology. CONCLUSIONS Described ultrafast high spatial-resolution MRA is superior to routinely used TOF-MRA in assessment of morphometric features of intracranial aneurysms, such as intraluminal thrombosis and aneurysm morphology, and is obtained in a fraction of the time (6 seconds).
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Affiliation(s)
- Kambiz Nael
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - James Drummond
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Anthony B Costa
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Reade A De Leacy
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY
| | | | - J Mocco
- Department of Neurosurgery, Icahn School of Medicine at Mount Sinai, New York, NY
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Levine E, Daniel B, Vasanawala S, Hargreaves B, Saranathan M. 3D Cartesian MRI with compressed sensing and variable view sharing using complementary poisson-disc sampling. Magn Reson Med 2016; 77:1774-1785. [PMID: 27097596 DOI: 10.1002/mrm.26254] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Revised: 02/22/2016] [Accepted: 04/01/2016] [Indexed: 12/13/2022]
Abstract
PURPOSE To enable robust, high spatio-temporal-resolution three-dimensional Cartesian MRI using a scheme incorporating a novel variable density random k-space sampling trajectory allowing flexible and retrospective selection of the temporal footprint with compressed sensing (CS). METHODS A complementary Poisson-disc k-space sampling trajectory was designed to allow view sharing and varying combinations of reduced view sharing with CS from the same prospective acquisition. These schemes were used for two-point Dixon-based dynamic contrast-enhanced MRI (DCE-MRI) of the breast and abdomen. Results were validated in vivo with a novel approach using variable-flip-angle data, which was retrospectively accelerated using the same methods but offered a ground truth. RESULTS In breast DCE-MRI, the temporal footprint could be reduced 2.3-fold retrospectively without introducing noticeable artifacts, improving depiction of rapidly enhancing lesions. Further, experiments with variable-flip-angle data showed that reducing view sharing improved accuracy in reconstruction and T1 mapping. In abdominal MRI, 2.3-fold and 3.6-fold reductions in temporal footprint allowed reduced motion artifacts. CONCLUSION The complementary-Poisson-disc k-space sampling trajectory allowed a retrospective spatiotemporal resolution tradeoff using CS and view sharing, imparting robustness to motion and contrast enhancement. The technique was also validated using a novel approach of fully acquired variable-flip-angle acquisition. Magn Reson Med 77:1774-1785, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Evan Levine
- Lucas Center, Departments of Electrical Engineering and Radiology, Stanford University, Stanford, California, USA
| | - Bruce Daniel
- Lucas Center, Departments of Electrical Engineering and Radiology, Stanford University, Stanford, California, USA
| | - Shreyas Vasanawala
- Lucas Center, Departments of Electrical Engineering and Radiology, Stanford University, Stanford, California, USA
| | - Brian Hargreaves
- Lucas Center, Departments of Electrical Engineering and Radiology, Stanford University, Stanford, California, USA
| | - Manojkumar Saranathan
- Lucas Center, Departments of Electrical Engineering and Radiology, Stanford University, Stanford, California, USA
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Odéen H, Todd N, Diakite M, Minalga E, Payne A, Parker DL. Sampling strategies for subsampled segmented EPI PRF thermometry in MR guided high intensity focused ultrasound. Med Phys 2015; 41:092301. [PMID: 25186406 DOI: 10.1118/1.4892171] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To investigate k-space subsampling strategies to achieve fast, large field-of-view (FOV) temperature monitoring using segmented echo planar imaging (EPI) proton resonance frequency shift thermometry for MR guided high intensity focused ultrasound (MRgHIFU) applications. METHODS Five different k-space sampling approaches were investigated, varying sample spacing (equally vs nonequally spaced within the echo train), sampling density (variable sampling density in zero, one, and two dimensions), and utilizing sequential or centric sampling. Three of the schemes utilized sequential sampling with the sampling density varied in zero, one, and two dimensions, to investigate sampling the k-space center more frequently. Two of the schemes utilized centric sampling to acquire the k-space center with a longer echo time for improved phase measurements, and vary the sampling density in zero and two dimensions, respectively. Phantom experiments and a theoretical point spread function analysis were performed to investigate their performance. Variable density sampling in zero and two dimensions was also implemented in a non-EPI GRE pulse sequence for comparison. All subsampled data were reconstructed with a previously described temporally constrained reconstruction (TCR) algorithm. RESULTS The accuracy of each sampling strategy in measuring the temperature rise in the HIFU focal spot was measured in terms of the root-mean-square-error (RMSE) compared to fully sampled "truth." For the schemes utilizing sequential sampling, the accuracy was found to improve with the dimensionality of the variable density sampling, giving values of 0.65 °C, 0.49 °C, and 0.35 °C for density variation in zero, one, and two dimensions, respectively. The schemes utilizing centric sampling were found to underestimate the temperature rise, with RMSE values of 1.05 °C and 1.31 °C, for variable density sampling in zero and two dimensions, respectively. Similar subsampling schemes with variable density sampling implemented in zero and two dimensions in a non-EPI GRE pulse sequence both resulted in accurate temperature measurements (RMSE of 0.70 °C and 0.63 °C, respectively). With sequential sampling in the described EPI implementation, temperature monitoring over a 192×144×135 mm3 FOV with a temporal resolution of 3.6 s was achieved, while keeping the RMSE compared to fully sampled "truth" below 0.35 °C. CONCLUSIONS When segmented EPI readouts are used in conjunction with k-space subsampling for MR thermometry applications, sampling schemes with sequential sampling, with or without variable density sampling, obtain accurate phase and temperature measurements when using a TCR reconstruction algorithm. Improved temperature measurement accuracy can be achieved with variable density sampling. Centric sampling leads to phase bias, resulting in temperature underestimations.
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Affiliation(s)
- Henrik Odéen
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84108 and Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Nick Todd
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Mahamadou Diakite
- Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84108 and Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Emilee Minalga
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Allison Payne
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
| | - Dennis L Parker
- Department of Radiology, University of Utah, Salt Lake City, Utah 84108
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Riederer SJ, Haider CR, Borisch EA, Weavers PT, Young PM. Recent advances in 3D time-resolved contrast-enhanced MR angiography. J Magn Reson Imaging 2015; 42:3-22. [PMID: 26032598 DOI: 10.1002/jmri.24880] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/31/2014] [Indexed: 11/11/2022] Open
Abstract
Contrast-enhanced magnetic resonance angiography (CE-MRA) was first introduced for clinical studies approximately 20 years ago. Early work provided 3-4 mm spatial resolution with acquisition times in the 30-second range. Since that time there has been continuing effort to provide improved spatial resolution with reduced acquisition time, allowing high resolution 3D time-resolved studies. The purpose of this work is to describe how this has been accomplished. Specific technical enablers have been: improved gradients allowing reduced repetition times, improved k-space sampling and reconstruction methods, parallel acquisition, particularly in two directions, and improved and higher count receiver coil arrays. These have collectively made high-resolution time-resolved studies readily available for many anatomic regions. Depending on the application, ∼1 mm isotropic resolution is now possible with frame times of several seconds. Clinical applications of time-resolved CE-MRA are briefly reviewed.
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Cheng JY, Zhang T, Ruangwattanapaisarn N, Alley MT, Uecker M, Pauly JM, Lustig M, Vasanawala SS. Free-breathing pediatric MRI with nonrigid motion correction and acceleration. J Magn Reson Imaging 2014; 42:407-20. [PMID: 25329325 DOI: 10.1002/jmri.24785] [Citation(s) in RCA: 108] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2014] [Accepted: 10/06/2014] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To develop and assess motion correction techniques for high-resolution pediatric abdominal volumetric magnetic resonance images acquired free-breathing with high scan efficiency. MATERIALS AND METHODS First, variable-density sampling and radial-like phase-encode ordering were incorporated into the 3D Cartesian acquisition. Second, intrinsic multichannel butterfly navigators were used to measure respiratory motion. Lastly, these estimates are applied for both motion-weighted data-consistency in a compressed sensing and parallel imaging reconstruction, and for nonrigid motion correction using a localized autofocusing framework. With Institutional Review Board approval and informed consent/assent, studies were performed on 22 consecutive pediatric patients. Two radiologists independently scored the images for overall image quality, degree of motion artifacts, and sharpness of hepatic vessels and the diaphragm. The results were assessed using paired Wilcoxon test and weighted kappa coefficient for interobserver agreements. RESULTS The complete procedure yielded significantly better overall image quality (mean score of 4.7 out of 5) when compared to using no correction (mean score of 3.4, P < 0.05) and to using motion-weighted accelerated imaging (mean score of 3.9, P < 0.05). With an average scan time of 28 seconds, the proposed method resulted in comparable image quality to conventional prospective respiratory-triggered acquisitions with an average scan time of 91 seconds (mean score of 4.5). CONCLUSION With the proposed methods, diagnosable high-resolution abdominal volumetric scans can be obtained from free-breathing data acquisitions.
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Affiliation(s)
- Joseph Y Cheng
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.,Department of Radiology, Stanford University, Stanford, California, USA
| | - Tao Zhang
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA.,Department of Radiology, Stanford University, Stanford, California, USA
| | | | - Marcus T Alley
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Martin Uecker
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, USA
| | - John M Pauly
- Magnetic Resonance Systems Research Laboratory, Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Michael Lustig
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California, USA
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Saranathan M, Rettmann DW, Hargreaves BA, Lipson JA, Daniel BL. Variable spatiotemporal resolution three-dimensional Dixon sequence for rapid dynamic contrast-enhanced breast MRI. J Magn Reson Imaging 2013; 40:1392-9. [PMID: 24227703 DOI: 10.1002/jmri.24490] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Accepted: 09/25/2013] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To investigate a new variable spatiotemporal resolution dynamic contrast-enhanced (DCE) MRI method termed DIfferential Subsampling with Cartesian Ordering (DISCO), for imaging of breast cancer. MATERIALS AND METHODS DISCO combines variable density, pseudorandom k-space segmentation and two-point Dixon fat-water separation for high spatiotemporal resolution breast DCE MRI. During the contrast wash-in phase, view sharing is used to achieve high temporal resolution. Forty patients referred for breast MRI were imaged, 26 using the proposed DISCO sequence and 14 using a conventional low-spatial-resolution dynamic sequence (VIBRANT-FLEX) on a 3 Tesla scanner. DISCO dynamic images from 14 patients were compared with VIBRANT-FLEX images from 14 other patients. The image quality assessed by radiologist image ranking in a blinded manner, and the temporal characteristics of the two sequences were compared. RESULTS A spatial resolution of 1.1 × 1.1 × 1.2 mm(3) (160 slices, 28 cm field of view) was achieved with axial bilateral coverage in 120 s. Dynamic images with ∼ 9 s effective temporal resolution were generated during the 2-min contrast wash-in phase. The image quality of DISCO dynamic images ranked significantly higher than low spatial resolution VIBRANT-FLEX images (19.5 versus 9.5, Mann-Whitney U-test P = 0.00914), with no significant differences in the maximum slope of aortic enhancement. CONCLUSION DISCO is a promising variable-spatiotemporal-resolution imaging sequence for capturing the dynamics of rapidly enhancing tumors as well as structural features postcontrast. A near 1-mm isotropic spatial resolution was achieved with postcontrast static phase images in 120 s and dynamic phase images acquired in 9 s per phase.
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Johnson CP, Polley TW, Glockner JF, Young PM, Riederer SJ. Buildup of image quality in view-shared time-resolved 3D CE-MRA. Magn Reson Med 2012; 70:348-57. [PMID: 22936574 DOI: 10.1002/mrm.24466] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/17/2012] [Accepted: 07/30/2012] [Indexed: 11/09/2022]
Abstract
Time-resolved three-dimensional contrast-enhanced MR angiography often relies on view sharing of peripheral k-space data to enable acquisition of angiograms with both high spatial resolution and a rapid frame rate. It is typically assumed that k-space will be fully sampled during passage of the contrast bolus arterial phase. However, this is not the case when view sharing is incomplete, for example, at the leading edge of an enhancing vessel or if acquisition time is limited as in fluoroscopic tracking for multistation bolus chase MR angiography. Incomplete view sharing will degrade image quality, for example, by reducing vessel signal and sharpness and increasing undersampling artifacts. In this work, the evolution of angiogram quality with view sharing is quantitatively assessed in phantom experiments and in vivo contrast-enhanced MR angiography calf studies. It is demonstrated that there are multiple sets of sequence parameters that can yield a target image update time, but the choice of parameters can profoundly affect how image quality evolves with view sharing. A fundamental tradeoff between vessel signal and sharpness and its relationship to the sequence temporal footprint is investigated and discussed.
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Affiliation(s)
- Casey P Johnson
- MR Research Laboratory and Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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Mostardi PM, Young PM, McKusick MA, Riederer SJ. High temporal and spatial resolution imaging of peripheral vascular malformations. J Magn Reson Imaging 2012; 36:933-42. [PMID: 22674646 DOI: 10.1002/jmri.23714] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Accepted: 04/30/2012] [Indexed: 11/12/2022] Open
Abstract
PURPOSE To assess the performance of a recently developed 3D time-resolved CE-MRA technique, Cartesian Acquisition with Projection-Reconstruction-like sampling (CAPR), for accurate characterization and treatment planning of vascular malformations of the periphery. MATERIALS AND METHODS Twelve patient studies were performed (eight female, four male; average age, 33 years). The protocol consisted of three-dimensional (3D) time-resolved CE-MRA followed by a single late phase T1-weighted acquisition. Vascular malformations were imaged in the forearm, hand, thigh, and foot. Imaging evaluation was performed for accurate characterization of lesion type, identification of feeding and draining vessels, involvement with surrounding tissue, overall quality for diagnosis and treatment planning, and correlation with conventional angiography. RESULTS Time-resolved CE-MRA allowed for characterization of malformation flow and type. Feeding and draining vessels were identified in all cases. Overall quality for diagnosis and treatment planning was 3.58/4.0, and correlation with conventional angiography was scored as 3.89/4.0. CONCLUSION The CAPR time series has been shown to portray the temporal dynamics and structure of vascular malformations as well as the normal vasculature with high quality. CAPR time-resolved imaging is able to accurately characterize high and low flow lesions, allowing for pretreatment lesion assessment and treatment planning. Delayed imaging is important to capture complete filling of very slow flow vascular malformations.
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Saranathan M, Rettmann DW, Hargreaves BA, Clarke SE, Vasanawala SS. DIfferential Subsampling with Cartesian Ordering (DISCO): a high spatio-temporal resolution Dixon imaging sequence for multiphasic contrast enhanced abdominal imaging. J Magn Reson Imaging 2012; 35:1484-92. [PMID: 22334505 DOI: 10.1002/jmri.23602] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 01/09/2012] [Indexed: 01/03/2023] Open
Abstract
PURPOSE To develop and evaluate a multiphasic contrast-enhanced MRI method called DIfferential Sub-sampling with Cartesian Ordering (DISCO) for abdominal imaging. MATERIALS AND METHODS A three-dimensional, variable density pseudo-random k-space segmentation scheme was developed and combined with a Dixon-based fat-water separation algorithm to generate high temporal resolution images with robust fat suppression and without compromise in spatial resolution or coverage. With institutional review board approval and informed consent, 11 consecutive patients referred for abdominal MRI at 3 Tesla (T) were imaged with both DISCO and a routine clinical three-dimensional SPGR-Dixon (LAVA FLEX) sequence. All images were graded by two radiologists using quality of fat suppression, severity of artifacts, and overall image quality as scoring criteria. For assessment of arterial phase capture efficiency, the number of temporal phases with angiographic phase and hepatic arterial phase was recorded. RESULTS There were no significant differences in quality of fat suppression, artifact severity or overall image quality between DISCO and LAVA FLEX images (P > 0.05, Wilcoxon signed rank test). The angiographic and arterial phases were captured in all 11 patients scanned using the DISCO acquisition (mean number of phases were two and three, respectively). CONCLUSION DISCO effectively captures the fast dynamics of abdominal pathology such as hyperenhancing hepatic lesions with a high spatio-temporal resolution. Typically, 1.1 × 1.5 × 3 mm spatial resolution over 60 slices was achieved with a temporal resolution of 4-5 s.
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Abstract
In the study of carotid arteries, modern techniques of imaging allow to analyze various alterations beyond simple luminal narrowing, including the morphology of atherosclerotic plaques, the arterial wall and the surrounding structures. By using CTA and MRI it is possible to obtain three-dimensional rendering of anatomic structures with excellent detail for treatment planning. This paper will detail the role of various imaging methods for the assessment of carotid artery pathology with emphasis on the detection, analysis and characterization of carotid atherosclerosis.
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Dick EA, Burnett C, Anstee A, Hamady M, Black D, Gedroyc WMW. Time-resolved imaging of contrast kinetics three-dimensional (3D) magnetic resonance venography in patients with pelvic congestion syndrome. Br J Radiol 2011; 83:882-7. [PMID: 20846985 DOI: 10.1259/bjr/82417499] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The purpose of this study was to assess the role of magnetic resonance venography (MRV) with time-resolved imaging of contrast kinetics (TRICKS) in dynamically evaluating ovarian vein dilation, reflux and direction of flow in patients with suspected pelvic congestion syndrome (PCS). The hypotheses tested were: (i) That conspicuity scores of the ovarian veins across three raters was greater using TRICKS MRV compared with T2W or T(2)* imaging; (ii) That three key MR variables (ovarian vein diameter, timing and grade of reflux) correlated across all raters. We carried out a retrospective study of 13 patients undergoing T2W and TRICKS MRI and pelvic sonography (n = 4) or catheter venography (n = 5). Three observers rated conspicuity, vessel diameter, timing and grade of ovarian vein reflux for T(2)/T2*W and TRICKS MRI. The mean left ovarian diameter for all patients with reflux was 7.9 mm (range 2.2-12 mm). There was high inter-observer agreement for ovarian vein diameter for both sequences. TRICKS showed significantly greater conspicuity than T(2)/T2*W imaging (TRICKS: T(2)/T2* mean (SD) = 7.80 (3.20):5.50 (1.97), F (1,12) = 5.80, p < 0.05). TRICKS MRV demonstrated high inter-observer correlation for timing and grade of reflux (r (36) = 0.77,0.71,0.79, p < 0.01). TRICKS MRA/V was significantly degraded by breathing artefact in two patients. We conclude that TRICKS MRV accurately and dynamically demonstrates ovarian vein reflux in patients with PCS but requires quiet respiration. TRICKS MRV has better image conspicuity than T(2)/T2*W imaging and sufficient temporal resolution to distinguish between Grade I, II and III reflux.
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Affiliation(s)
- E A Dick
- Department of Radiology and Vascular Surgery, Imperial College NHS Trust, St Mary's Hospital, Praed St, London W2 1NY, UK.
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Prieto C, Uribe S, Razavi R, Atkinson D, Schaeffter T. 3D undersampled golden‐radial phase encoding for DCE‐MRA using inherently regularized iterative SENSE. Magn Reson Med 2010; 64:514-26. [DOI: 10.1002/mrm.22446] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Claudia Prieto
- King's College London, Division of Imaging Sciences, NIHR Biomedical Research Centre at Guy's & St Thomas' Foundation Trust London, United Kingdom
| | - Sergio Uribe
- King's College London, Division of Imaging Sciences, NIHR Biomedical Research Centre at Guy's & St Thomas' Foundation Trust London, United Kingdom
- Pontificia Universidad Católica de Chile, Radiology Department, School of Medicine, Center for Biomedical Imaging, Santiago, Chile
| | - Reza Razavi
- King's College London, Division of Imaging Sciences, NIHR Biomedical Research Centre at Guy's & St Thomas' Foundation Trust London, United Kingdom
| | - David Atkinson
- Centre for Medical Image Computing, University College London, London, United Kingdom
| | - Tobias Schaeffter
- King's College London, Division of Imaging Sciences, NIHR Biomedical Research Centre at Guy's & St Thomas' Foundation Trust London, United Kingdom
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Riederer SJ, Haider CR, Borisch EA. Time-of-arrival mapping at three-dimensional time-resolved contrast-enhanced MR angiography. Radiology 2009; 253:532-42. [PMID: 19789236 DOI: 10.1148/radiol.2532082322] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study was HIPAA compliant and institutional review board approved, and informed consent was obtained from all volunteers. The authors describe a method for generating a time-of-arrival (TOA) map of intravenously administered contrast material, as observed in a time series of three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiograms. The method may enable visualization and interpretation, on one 3D image, of the temporal enhancement patterns that occur in the vasculature. Colorization of TOA values may further aid interpretation. The quality of the results depends not only on the adequacy of the frame rate, spatial resolution, and signal-to-noise ratio of the MR image acquisition method but also on the accuracy and clarity with which the leading edge of the contrast material bolus is depicted. The criteria for optimizing these parameters are described. The TOA mapping technique is demonstrated by using vascular studies of the hands, brain, and lower leg regions.
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Affiliation(s)
- Stephen J Riederer
- Magnetic Resonance Laboratory, Mayo Clinic, 200 First St SW, Opus 2-133, Rochester, MN 55905, USA.
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Boubertakh R, Prieto C, Batchelor PG, Uribe S, Atkinson D, Eggers H, Sørensen TS, Hansen MS, Razavi RS, Schaeffter T. Whole-heart imaging using undersampled radial phase encoding (RPE) and iterative sensitivity encoding (SENSE) reconstruction. Magn Reson Med 2009; 62:1331-7. [PMID: 19780159 DOI: 10.1002/mrm.22102] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- R Boubertakh
- King's College London, British Heart Foundation (BHF) Centre, Division of Imaging Sciences, National Institute for Health Research (NIHR) Biomedical Research Centre at Guy's & St Thomas' National Health Service (NHS) Foundation Trust, London, UK
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16
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Ozturk-Isik E, Chen AP, Crane JC, Bian W, Xu D, Han ET, Chang SM, Vigneron DB, Nelson SJ. 3D sensitivity encoded ellipsoidal MR spectroscopic imaging of gliomas at 3T. Magn Reson Imaging 2009; 27:1249-57. [PMID: 19766422 DOI: 10.1016/j.mri.2009.05.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 04/04/2009] [Accepted: 05/07/2009] [Indexed: 11/18/2022]
Abstract
PURPOSE The goal of this study was to implement time efficient data acquisition and reconstruction methods for 3D magnetic resonance spectroscopic imaging (MRSI) of gliomas at a field strength of 3T using parallel imaging techniques. METHODS The point spread functions, signal to noise ratio (SNR), spatial resolution, metabolite intensity distributions and Cho:NAA ratio of 3D ellipsoidal, 3D sensitivity encoding (SENSE) and 3D combined ellipsoidal and SENSE (e-SENSE) k-space sampling schemes were compared with conventional k-space data acquisition methods. RESULTS The 3D SENSE and e-SENSE methods resulted in similar spectral patterns as the conventional MRSI methods. The Cho:NAA ratios were highly correlated (P<.05 for SENSE and P<.001 for e-SENSE) with the ellipsoidal method and all methods exhibited significantly different spectral patterns in tumor regions compared to normal appearing white matter. The geometry factors ranged between 1.2 and 1.3 for both the SENSE and e-SENSE spectra. When corrected for these factors and for differences in data acquisition times, the empirical SNRs were similar to values expected based upon theoretical grounds. The effective spatial resolution of the SENSE spectra was estimated to be same as the corresponding fully sampled k-space data, while the spectra acquired with ellipsoidal and e-SENSE k-space samplings were estimated to have a 2.36-2.47-fold loss in spatial resolution due to the differences in their point spread functions. CONCLUSION The 3D SENSE method retained the same spatial resolution as full k-space sampling but with a 4-fold reduction in scan time and an acquisition time of 9.28 min. The 3D e-SENSE method had a similar spatial resolution as the corresponding ellipsoidal sampling with a scan time of 4:36 min. Both parallel imaging methods provided clinically interpretable spectra with volumetric coverage and adequate SNR for evaluating Cho, Cr and NAA.
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Affiliation(s)
- Esin Ozturk-Isik
- Margaret Hart Surbeck Laboratory of Advanced Imaging, Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA 94158, USA.
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Mostardi PM, Haider CR, Rossman PJ, Borisch EA, Riederer SJ. Controlled experimental study depicting moving objects in view-shared time-resolved 3D MRA. Magn Reson Med 2009; 62:85-95. [PMID: 19319897 DOI: 10.1002/mrm.21993] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Various methods have been used for time-resolved contrast-enhanced magnetic resonance angiography (CE-MRA), many involving view sharing. However, the extent to which the resultant image time series represents the actual dynamic behavior of the contrast bolus is not always clear. Although numerical simulations can be used to estimate performance, an experimental study can allow more realistic characterization. The purpose of this work was to use a computer-controlled motion phantom for study of the temporal fidelity of three-dimensional (3D) time-resolved sequences in depicting a contrast bolus. It is hypothesized that the view order of the acquisition and the selection of views in the reconstruction can affect the positional accuracy and sharpness of the leading edge of the bolus and artifactual signal preceding the edge. Phantom studies were performed using dilute gadolinium-filled vials that were moved along tabletop tracks by a computer-controlled motor. Several view orders were tested using view-sharing and Cartesian sampling. Compactness of measuring the k-space center, consistency of view ordering within each reconstruction frame, and sampling the k-space center near the end of the temporal footprint were shown to be important in accurate portrayal of the leading edge of the bolus. A number of findings were confirmed in an in vivo CE-MRA study.
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Abstract
PURPOSE OF REVIEW Bacterial vaginosis is a common condition that recurs frequently, adversely affecting women's lives, and is associated with complications including increased risk of sexually transmitted infections, HIV, and adverse pregnancy outcome. RECENT FINDINGS New molecular techniques have increased our understanding of the numerous bacteria associated with bacterial vaginosis, and a biofilm containing mostly Gardnerella and Atopobium vaginae, which can persist after treatment has been described. Suppressive treatment with metronidazole gel can suppress recurrence. Physiological approaches such as acidification and probiotics have been investigated with variable results. SUMMARY Advances in our understanding of the pathogenesis of bacterial vaginosis allow the opportunity to improve treatments to prevent recurrence, which may require a combination of modalities. We must find ways to help affected women and reduce the complications associated with bacterial vaginosis.
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Menke J, Helms G, Larsen J. Viewing the effective k-space coverage of MR images: phantom experiments with fast Fourier transform. Magn Reson Imaging 2009; 28:87-94. [PMID: 19553053 DOI: 10.1016/j.mri.2009.05.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 03/23/2009] [Accepted: 05/10/2009] [Indexed: 11/29/2022]
Abstract
The purpose of this experimental study was to evaluate whether the effective k-space coverage of MR images can in principle be viewed after multidimensional Fourier transform back to k-space. A water-soaked sponge phantom providing homogeneous k-space pattern was imaged with different standard MR sequences, utilizing elliptic acquisitions, partial-Fourier acquisitions and elliptic filtering as imaging examples. The resulting MR images were Fourier-transformed to the spatial frequency domain (the k-space) to visualize their effective k-space coverage. These frequency domain images are named "backtransformed k-space images." For a quantitative assessment, the sponge phantom was imaged with three-dimensional partial-Fourier sequences while varying the partial acquisition parameters in slice and phase direction. By linear regression analysis, the k-space coverage as expected from the sequence menu parameters was compared to the effective k-space coverage as observed in the backtransformed k-space images. The k-space coverage of elliptic and partial-Fourier acquisitions became visible in the backtransformed k-space images, as well as the effect of elliptic filtering. The expected and the observed k-space coverage showed a highly significant correlation (r=.99, P<.001). In conclusion, the effective k-space coverage of MR images becomes visible when Fourier-transforming MR images of a sponge phantom back to k-space. This method could be used for several purposes including sequence parameter optimization, basic imaging research, and to enhance a visual understanding of k-space, especially in three-dimensional MR imaging.
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Affiliation(s)
- Jan Menke
- Department of Diagnostic Radiology, University Hospital, Goettingen, Germany.
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20
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Du J. Contrast-enhanced MR angiography using time resolved interleaved projection sampling with three-dimensional cartesian phase and slice encoding (TRIPPS). Magn Reson Med 2009; 61:918-24. [DOI: 10.1002/mrm.21805] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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21
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Haider CR, Hu HH, Campeau NG, Huston J, Riederer SJ. 3D high temporal and spatial resolution contrast-enhanced MR angiography of the whole brain. Magn Reson Med 2009; 60:749-60. [PMID: 18727101 DOI: 10.1002/mrm.21675] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Sensitivity encoding (SENSE) and partial Fourier techniques have been shown to reduce the acquisition time and provide high diagnostic quality images. However, for time-resolved acquisitions there is a need for both high temporal and spatial resolution. View sharing can be used to provide an increased frame rate but at the cost of acquiring spatial frequencies over a duration longer than a frame time. In this work we hypothesize that a CArtesian Projection Reconstruction-like (CAPR) technique in combination with 2D SENSE, partial Fourier, and view sharing can provide 1-2 mm isotropic resolution with sufficient temporal resolution to distinguish intracranial arterial and venous phases of contrast passage in whole-brain angiography. In doing so, the parameter of "temporal footprint" is introduced as a descriptor for characterizing and comparing time-resolved view-shared pulse sequences. It is further hypothesized that short temporal footprint sequences have higher temporal fidelity than similar sequences with longer temporal footprints. The tradeoff of temporal footprint and temporal acceleration is presented and characterized in numerical simulations. Results from 11 whole-brain contrast-enhanced MR angiography studies with the new method with SENSE acceleration factors R = 4 and 5.3 are shown to provide images of comparable or higher diagnostic quality than the unaccelerated reference.
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Affiliation(s)
- Clifton R Haider
- MR Research Laboratory, Mayo Clinic, Rochester, Minnesota 55905, USA
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Diagnostic Cerebral Angiography: Archaic and Complication-Prone or Here to Stay for Another 80 Years? AJR Am J Roentgenol 2008; 190:1435-7. [DOI: 10.2214/ajr.07.3522] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Hnatiuk B, Emery DJ, Wilman AH. Effects of doubling and tripling the spatial resolution in standard 3D contrast-enhanced magnetic resonance angiography of carotid artery disease. J Magn Reson Imaging 2008; 27:71-7. [PMID: 18050355 DOI: 10.1002/jmri.21225] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
PURPOSE To determine whether three-dimensional (3D) contrast-enhanced MR angiography (CE-MRA) of carotid artery disease may be more effective when performed at double or triple the spatial resolution of the present common clinical standard at 1.5T. MATERIALS AND METHODS A total of 110 consecutive patients with suspected carotid artery disease were imaged with elliptical centric 3D CE-MRA. The total acquisition time was increased from the standard clinical protocol of 21 seconds up to 60 seconds in 10-second steps, with corresponding voxel volume reductions from 0.95 mm(3) down to 0.35 mm(3). Quantitative and blinded qualitative measurements were then performed to determine the preferred imaging time. RESULTS In patients with significant stenosis, the 40-second acquisition with 0.53-mm(3) voxels produced significantly sharper images of the carotid bifurcation than the 21-second standard using 0.95-mm(3) voxels, but did not have a significant effect in patients without disease. CONCLUSION In patients with carotid artery stenosis, decreasing the voxel volume to 0.5 mm(3) by increasing the scan time from 21 to 40 seconds resulted in sharper depiction of the carotid stenosis. Further decreases in voxel volume, by extending the acquisition time further, did not improve the vessel depiction due to both signal-to-noise ratio (SNR) and sharpness losses.
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Affiliation(s)
- Brad Hnatiuk
- Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada
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Imade G, Sagay A, Egah D, Onwuliri V, Grigg M, Egbodo C, Thacher T, Potts M, Short R. Prevalence of HIV and other sexually transmissible infections in relation to lemon or lime juice douching among female sex workers in Jos, Nigeria. Sex Health 2008; 5:55-60. [DOI: 10.1071/sh07047] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Accepted: 12/19/2007] [Indexed: 11/23/2022]
Abstract
Background: The rates of sexually transmissible infections (STI), including HIV, are high among female sex workers (FSW) in Nigeria and the use of various local vaginal cleansing agents to prevent infection is a common practice. The present study was aimed at determining whether any association exists between current lime or lemon douching and the prevalence of STI and HIV infections among FSW in Jos, Nigeria. Methods: Consenting FSW who were users of lemon or lime (UL) or non-users (NUL) were recruited for the study between May and September 2006. A structured questionnaire was administered by trained counsellors. Pre-HIV test counselling was done. Participant’s blood samples were tested for HIV and syphilis. Genital examination was done and high vaginal and endocervical samples were collected. The samples obtained were processed for STI using standard laboratory procedures. FSW found with treatable STI received free drugs. HIV results were disclosed after post-test counselling and positive FSW were referred to a HIV/AIDS facility for care, support and antiretroviral therapy. Results: A total of 398 FSW (86 UL and 312 NUL) participated in the study. Their mean age was 27.6 ± 7.0 years (range 16–63 years). HIV prevalence was high for both UL and NUL: 48.8 and 48.2%, respectively (odds ratio 1.0; 95% confidence interval 0.6–1.2, P = 0.9427). The rates of bacterial vaginosis were not significantly higher in UL (UL 55.8%, NUL 44.0%, odds ratio 1.59, 95% confidence interval 0.96–2.65, P = 0.06). There were no associations between the use of citrus douching and other STI. Conclusion: There were no significant associations between the prevalence of STI and HIV and lime or lemon juice usage.
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Madhuranthakam AJ, Hu HH, Kruger DG, Riederer SJ. Numerical equilibration of signal intensity and spatial resolution in time-resolved continuously moving table imaging. Magn Reson Med 2006; 55:694-9. [PMID: 16450354 DOI: 10.1002/mrm.20800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Time-resolved continuously moving table imaging techniques have been previously developed to observe a dynamically changing phenomenon over an extended field-of-view. The acquisition involves differential k-space sampling and view sharing. Since the table is continuously moving during data acquisition, the k-space for any longitudinal position is sampled only sparsely for the first reconstruction timeframe and is progressively more fully sampled for subsequent frames. Consequently, the signal intensity increases and the lateral spatial resolution improves from frame to frame even for static materials, which can mask true dynamically changing phenomena. This work provides a description of this effect and a means for signal correction in the early reconstruction frames, thus permitting any residual variation in signal intensity to be primarily attributed to true dynamic processes. The method is tested experimentally on a static phantom and in a peripheral vascular study designed to observe the leading edge of the contrast bolus.
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Affiliation(s)
- Ananth J Madhuranthakam
- MR Research Lab and Dept. of Radiology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA
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Madhuranthakam AJ, Hu HH, Kruger DG, Glockner JF, Riederer SJ. Contrast-enhanced MR Angiography of the Peripheral Vasculature with a Continuously Moving Table and Modified Elliptical Centric Acquisition. Radiology 2006; 240:222-9. [PMID: 16793981 DOI: 10.1148/radiol.2401050772] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
This study was approved by the institutional review board and was HIPAA compliant. All subjects provided written informed consent, and subject confidentiality was protected. The purpose of this study was to prospectively evaluate the feasibility of integrating a modified elliptical centric (EC) acquisition with a continuously moving table technique to acquire high-spatial-resolution contrast material-enhanced magnetic resonance (MR) angiograms of the peripheral vasculature. Incorporation of two-dimensional homodyne reconstruction modified the EC view order, allowing improved spatial resolution per unit time while retaining the advantage of venous suppression intrinsic to the EC technique. Spatial resolution was dynamically improved when the table reached the distal-most station. The modified view order provided improved spatial resolution in phantom examinations compared with that in standard examinations. Peripheral MR angiograms were generated in a group of 13 volunteers (eight women; five men; age range, 51-72 years; mean age, 58.5 years +/- 7.9 [standard deviation]) at 1.5 T. Four arterial regions were evaluated on a five-point scale (scores ranged from 0 to 4; a score of 4 was considered excellent); venous suppression was also evaluated. The mean arterial scores exceeded 3.0 for all regions. There was no venous signal or only superficial venous signal in 10 of the 13 cases.
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Affiliation(s)
- Ananth J Madhuranthakam
- MR Research Laboratory and Department of Radiology, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905, USA
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Hu HH, Madhuranthakam AJ, Kruger DG, Glockner JF, Riederer SJ. Combination of 2D sensitivity encoding and 2D partial fourier techniques for improved acceleration in 3D contrast-enhanced MR angiography. Magn Reson Med 2006; 55:16-22. [PMID: 16342155 PMCID: PMC2733782 DOI: 10.1002/mrm.20742] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Sensitivity encoding (SENSE) and partial Fourier (PF) techniques both reduce MRI acquisition time. Two-dimensional SENSE uses coil sensitivities to unfold aliasing in the phase/slice-encoding plane. One-dimensional PF and homodyne reconstruction are routinely applied in the frequency/phase-encoding plane to compensate for nonsampled k-space of the presumed real magnetization. Recently, a modified 3D elliptical centric acquisition was proposed to facilitate 2D-PF and homodyne reconstruction on an undersampled phase/slice-encoding plane. In this work we hypothesized that this 2D-PF technique can be combined with 2D-SENSE to achieve a greater acceleration factor than what each method can provide separately. Reconstruction of data whereby SENSE and PF are applied along the same axes is described. Contrast-enhanced MR angiography (CE-MRA) results from experiments using four receiver coils in phantom and volunteer studies are shown. In 11 volunteer studies, the SENSE-PF-homodyne technique using sevenfold acceleration (4x SENSE, 1.7x PF) consistently provided high-diagnostic-quality images with near 1-mm isotropic resolution in acquisition times of <20 s.
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Affiliation(s)
| | | | | | | | - Stephen J. Riederer
- Correspondence to: Stephen J. Riederer, Ph.D., Magnetic Resonance Laboratory, Mayo Clinic College of Medicine, 200 1st Street S.W., Rochester, MN 55905. E-mail:
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