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Muehler MR, Vigen K, Hernando D, Zhu A, Colgan TJ, Reeder SB. Reproducibility of liver R2* quantification for liver iron quantification from cardiac R2* acquisitions. Abdom Radiol (NY) 2021; 46:4200-4209. [PMID: 33982186 PMCID: PMC8346410 DOI: 10.1007/s00261-021-03099-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 04/14/2021] [Accepted: 04/21/2021] [Indexed: 01/19/2023]
Abstract
OBJECTIVES To evaluate the reproducibility of liver R2* measurements between a 2D cardiac ECG-gated and a 3D breath-hold liver CSE-MRI acquisition for liver iron quantification. METHODS A total of 54 1.5 T MRI exams from 51 subjects (18 women, 36 men, age 35.2 ± 21.8) were included. These included two sub-studies with 23 clinical MRI exams from 19 patients identified retrospectively, 24 participants with known or suspected iron overload, and 7 healthy volunteers acquired prospectively. The 2D cardiac and the 3D liver R2* maps were acquired in the same exam. Either acquisitions were reconstructed using a complex R2* algorithm that accounts for the presence of fat and residual phase errors due to eddy currents. Data were analyzed using colocalized ROIs in the liver. RESULTS Linear regression analysis demonstrated high Pearson's correlation and Lin's concordance coefficient for the overall study and both sub-studies. Bland-Altman analysis also showed good agreement, except for a slight increase of the mean R2* value above ~ 400 s-1. The Kolmogorow-Smirnow test revealed a non-normal distribution for (R2* 3D-R2* 2D) values from 0 to 600 s-1 in contrast to the 0-200 s-1 and 0-400 s-1 subpopulations. Linear regression analysis showed no relevant differences other than the intercept, likely due to only 7 measurements above 400 s-1. CONCLUSIONS The results demonstrate that R2*-measurements in the liver are feasible using 2D cardiac R2* maps compared to 3D liver R2* maps as the reference. Liver R2* may be underestimated for R2* > 400 s-1 using the 2D cardiac R2* mapping method.
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Affiliation(s)
- M R Muehler
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA.
- Department of Radiology and Neuroradiology, University Greifswald, Greifswald, Germany.
| | - K Vigen
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Medical Physics, University of Wisconsin, Madison, WI, USA
| | - D Hernando
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI, USA
- Department of Medical Physics, University of Wisconsin, Madison, WI, USA
- Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI, USA
| | - A Zhu
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI, USA
| | - T J Colgan
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA
| | - S B Reeder
- Department of Radiology, Wisconsin Institutes of Medical Research, University of Wisconsin, Room 2478, 1111 Highland Avenue, Madison, WI, 53705, USA
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI, USA
- Department of Medical Physics, University of Wisconsin, Madison, WI, USA
- Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI, USA
- Department of Medicine, University of Wisconsin, Madison, WI, USA
- Department of Emergency Medicine, University of Wisconsin, Madison, WI, USA
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Muehler MR, Rendell VR, Bergmann LL, Winslow ER, Reeder SB. Ferumoxytol-enhanced MR imaging for differentiating intrapancreatic splenules from other tumors. Abdom Radiol (NY) 2021; 46:2003-2013. [PMID: 33377995 PMCID: PMC8131292 DOI: 10.1007/s00261-020-02883-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 11/19/2020] [Accepted: 11/25/2020] [Indexed: 12/21/2022]
Abstract
Objectives Ferumoxytol is an ultra-small superparamagnetic iron oxide (USPIO) agent that is taken up by splenic tissue. This study describes our initial institutional experience of ferumoxytol-enhanced MRI (feMRI) for differentiating intrapancreatic splenules (IPS) from other pancreatic lesions. Methods In this retrospective study, patients with computed tomographic imaging that identified small enhancing lesions in the tail of the pancreas subsequently underwent feMRI for further characterization. The feMRI protocol included T2-weighted (T2w) imaging with and without fat suppression (FS), R2* mapping, diffusion-weighted imaging (DWI), and T1-weighted (T1w) imaging with FS, prior to contrast injection. Immediately after slow intravenous infusion with 3 mg/kg body weight ferumoxytol, T1w was repeated. Delayed imaging with all sequences were obtained 24–72 h after ferumoxytol administration. Results Seven patients underwent feMRI. In two patients, the pancreatic lesions were presumed as pancreatic neuroendocrine tumor (PNET) from feMRI and in the remaining 5 IPS. One of the two patients with PNET was symptomatic for NET. In another symptomatic patient with pathologically proven duodenal NET and suspected PNET, the pancreatic lesion was proven to be an IPS on feMRI. IPS demonstrated strong negative enhancement in feMRI on T2w and increased R2* values consistent with splenic tissue, while the presumed PNETs did not enhance. T2w FS was helpful on the pre-contrast images to identify IPS, while R2* did on post-contrast images. Neither DWI nor T1w contributed to differentiating PNETs from IPS. Conclusions This study demonstrates the potential utility of feMRI as a helpful adjunct diagnostic tool for differentiating IPS from other pancreatic lesions. Further studies in larger patient cohorts are needed.
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Affiliation(s)
- M R Muehler
- Department of Radiology, University of Wisconsin, Madison, WI, USA.
- Department of Radiology and Neuroradiology, University Greifswald, Greifswald, Germany.
| | - V R Rendell
- Department of Surgery, University of Wisconsin, Madison, WI, USA
| | - L L Bergmann
- Department of Radiology, University of Texas Southwestern, Dallas, TX, USA
| | - E R Winslow
- Medstar Georgetown Transplant Institute, Medstar Georgetown University Hospital, Washington, DC, USA
| | - S B Reeder
- Department of Radiology, University of Wisconsin, Madison, WI, USA
- Department of Biomedical Engineering, University of Wisconsin, Madison, WI, USA
- Department Medical Physics, University of Wisconsin, Madison, WI, USA
- Department of Medicine, University of Wisconsin, Madison, WI, USA
- Department of Emergency Medicine, University of Wisconsin, Madison, WI, USA
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Kinner S, Schubert TB, Bruce RJ, Rebsamen SL, Diamond CA, Reeder SB, Rowley HA. Deep Brain Nuclei T1 Shortening after Gadobenate Dimeglumine in Children: Influence of Radiation and Chemotherapy. AJNR Am J Neuroradiol 2017; 39:24-30. [PMID: 29146718 DOI: 10.3174/ajnr.a5453] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 08/22/2017] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Intrinsic T1-hyperintense signal has recently been reported in the deep gray nuclei on brain MR imaging after multiple doses of gadolinium-based contrast agents. Most reports have included adult patients and excluded those undergoing radiation or chemotherapy. We investigated whether T1 shortening is also observed in children and tried to determine whether radiochemotherapy is a risk factor for this phenomenon. MATERIALS AND METHODS In this single-center retrospective study, we reviewed clinical charts and images of all patients 18 years of age or younger with ≥4 gadobenate dimeglumine-enhanced MRIs for 6 years. Seventy-six children (mean age, 9.3 years; 60 unconfounded by treatment, 16 with radiochemotherapy) met the selection criteria (>4 MR imaging examinations; mean, 8). T1 signal intensity ratios for the dentate to pons and globus pallidus to thalamus were calculated and correlated with number of injections, time interval, and therapy. RESULTS Among the 60 children without radiochemotherapy, only 2 had elevated T1 signal intensity ratios (n = 20 and 16 injections). Twelve of the 16 children with radiochemotherapy showed elevated signal intensity ratios. Statistical analysis demonstrated a significant signal intensity ratio change for the number of injections (P < .001) and amount of gadolinium (P = .008), but not for the interscan time interval (P = .35). There was a significant difference in the average signal intensity ratio change between those with and without radiochemotherapy (P < .001). Chart review revealed no new neurologic deficits in any patients, related to their underlying conditions and prior surgeries. CONCLUSIONS Compared with published adult series, children show a similar pattern of T1 hyperintense signal changes of the dentate and globus pallidus after multiple gadobenate dimeglumine injections. The T1 signal changes in children may have a later onset but are accelerated by radiochemotherapy.
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Affiliation(s)
- S Kinner
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.) .,Department of Diagnostic and Interventional Radiology and Neuroradiology (S.K.), University Hospital Essen, Essen, Germany
| | - T B Schubert
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.).,Clinic of Radiology and Nuclear Medicine (T.B.S.), Basel University Hospital, Basel, Switzerland
| | - R J Bruce
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.)
| | - S L Rebsamen
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.)
| | | | - S B Reeder
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.).,Medical Physics (S.B.R.).,Emergency Medicine (S.B.R.).,Biomedical Engineering (S.B.R.).,Medicine (S.B.R.), University of Wisconsin-Madison, Madison, Wisconsin
| | - H A Rowley
- From the Departments of Radiology (S.K., T.B.S., R.J.B., S.L.R., S.B.R., H.A.R.)
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Frydrychowicz A, Roldan-Alzate A, Winslow E, Consigny D, Campo CA, Motosugi U, Johnson KM, Wieben O, Reeder SB. Comparison of radial 4D Flow-MRI with perivascular ultrasound to quantify blood flow in the abdomen and introduction of a porcine model of pre-hepatic portal hypertension. Eur Radiol 2017; 27:5316-5324. [PMID: 28656461 DOI: 10.1007/s00330-017-4862-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 03/22/2017] [Accepted: 04/20/2017] [Indexed: 02/07/2023]
Abstract
OBJECTIVES Objectives of this study were to compare radial time-resolved phase contrast magnetic resonance imaging (4D Flow-MRI) with perivascular ultrasound (pvUS) and to explore a porcine model of acute pre-hepatic portal hypertension (PHTN). METHODS Abdominal 4D Flow-MRI and pvUS in portal and splenic vein, hepatic and both renal arteries were performed in 13 pigs of approximately 60 kg. In six pigs, measurements were repeated after partial portal vein (PV) ligature. Inter- and intra-reader comparisons and statistical analysis including Bland-Altman (BA) comparison, paired Student's t tests and linear regression were performed. RESULTS PvUS and 4D Flow-MRI measurements agreed well; flow before partial PV ligature was 322 ± 30 ml/min in pvUS and 297 ± 27 ml/min in MRI (p = 0.294), and average BA difference was 25 ml/min [-322; 372]. Inter- and intra-reader results differed very little, revealed excellent correlation (R 2 = 0.98 and 0.99, respectively) and resulted in BA differences of -5 ml/min [-161; 150] and -2 ml/min [-28; 25], respectively. After PV ligature, PV flow decreased from 356 ± 50 to 298 ± 61 ml/min (p = 0.02), and hepatic arterial flow increased from 277 ± 36 to 331 ± 65 ml/min (p = n.s.). CONCLUSION The successful in vivo comparison of radial 4D Flow-MRI to perivascular ultrasound revealed good agreement of abdominal blood flow although with considerable spread of results. A model of pre-hepatic PHTN was successfully introduced and acute responses monitored. KEY POINTS • Radial 4D Flow-MRI in the abdomen was successfully compared to perivascular ultrasound. • Inter- and intra-reader testing demonstrated excellent reproducibility of upper abdominal 4D Flow-MRI. • A porcine model of acute pre-hepatic portal hypertension was successfully introduced. • 4D Flow-MRI successfully monitored acute changes in a model of portal hypertension.
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Affiliation(s)
- A Frydrychowicz
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA.
- Clinic for Radiology and Nuclear Medicine, University Hospital Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23562, Lübeck, Germany.
- University of Lübeck, Lübeck, Germany.
| | - A Roldan-Alzate
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
- Department of Mechanical Engineering, University of Wisconsin, Madison, USA
| | - E Winslow
- Department of Surgery, University of Wisconsin, Madison, USA
| | - D Consigny
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
| | - C A Campo
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
| | - U Motosugi
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
| | - K M Johnson
- Department of Medical Physics, University of Wisconsin, Madison, USA
| | - O Wieben
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
- Department of Medical Physics, University of Wisconsin, Madison, USA
| | - S B Reeder
- Department of Radiology, School of Medicine and Public Health, E3/366 Clinical Science Center, University of Wisconsin - Madison, 600 Highland Avenue, Madison, WI, 53792-3252, USA
- Department of Medical Physics, University of Wisconsin, Madison, USA
- Department of Biomedical Engineering, University of Wisconsin, Madison, USA
- Department of Medicine, University of Wisconsin, Madison, USA
- Department of Emergency Medicine, University of Wisconsin, Madison, USA
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Bley TA, François CJ, Schiebler ML, Wieben O, Takei N, Brittain JH, Del Rio AM, Grist TM, Reeder SB. Non-contrast-enhanced MRA of renal artery stenosis: validation against DSA in a porcine model. Eur Radiol 2015; 26:547-55. [DOI: 10.1007/s00330-015-3833-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2015] [Revised: 04/12/2015] [Accepted: 04/28/2015] [Indexed: 12/29/2022]
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Bannas P, Schiebler M, Motosugi U, Francois C, Reeder SB, Nagle S. MRA der Pulmonalarterien: Differenzierung zwischen Gibbs Artefakt und Lungenembolie. ROFO-FORTSCHR RONTG 2014. [DOI: 10.1055/s-0034-1372904] [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: 10/25/2022]
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Kramer H, Kliewer MA, Pickhardt PJ, Hernando D, Chen GH, Reiser MF, Reeder SB. Genauigkeit der Leber-Fettquantifizierung mittels CT, MRT und Ultraschall: ein prospektiver Vergleich zur MR Spektroskopie. ROFO-FORTSCHR RONTG 2014. [DOI: 10.1055/s-0034-1372835] [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: 10/25/2022]
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Schrauben EM, Johnson KM, Huston J, Del Rio AM, Reeder SB, Field A, Wieben O. Reproducibility of cerebrospinal venous blood flow and vessel anatomy with the use of phase contrast-vastly undersampled isotropic projection reconstruction and contrast-enhanced MRA. AJNR Am J Neuroradiol 2013; 35:999-1006. [PMID: 24287088 DOI: 10.3174/ajnr.a3779] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND AND PURPOSE The chronic cerebrospinal venous insufficiency hypothesis raises interest in cerebrospinal venous blood flow imaging, which is more complex and less established than in arteries. For accurate assessment of venous flow in chronic cerebrospinal venous insufficiency diagnosis and research, we must account for physiologic changes in flow patterns. This study examines day-to-day flow variability in cerebrospinal veins by use of 4D MR flow and contrast-enhanced MRA under typical, uncontrolled conditions in healthy individuals. MATERIALS AND METHODS Ten healthy volunteers were scanned in a test-retest fashion by use of a 4D flow MR imaging technique and contrast-enhanced MRA. Flow parameters obtained from phase contrast-vastly undersampled isotropic projection reconstruction and contrast-enhanced MRA scoring measurements in the head, neck, and chest veins were analyzed for internal consistency and interscan reproducibility. RESULTS Internal consistency was satisfied at the torcular herophili, with an input-output difference of 2.2%. Percentages of variations in flow were 20.3%, internal jugular vein; 20.4%, azygos vein; 6.8%, transverse sinus; and 5.1%, common carotid artery. Retrograde flow was found in the lower internal jugular vein (4.8%) and azygos vein (7.2%). Contrast-enhanced MRA interscan κ values for the internal jugular vein (left: 0.474, right: 0.366) and azygos vein (-0.053) showed poor interscan agreement. CONCLUSIONS Phase contrast-vastly undersampled isotropic projection reconstruction blood flow measurements are reliable and highly reproducible in intracranial veins and in the common carotid artery but not in veins of the neck (internal jugular vein) and chest (azygos vein) because of normal physiologic variation. Retrograde flow normally may be observed in the lower internal jugular vein and azygos vein. Low interrater agreement in contrast-enhanced MRA scans was observed. These findings have important implications for imaging diagnosis and experimental research of chronic cerebrospinal venous insufficiency.
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Affiliation(s)
- E M Schrauben
- From the Departments of Medical Physics (E.M.S., K.M.J., A.M.d.R., S.B.R., O.W.)
| | - K M Johnson
- From the Departments of Medical Physics (E.M.S., K.M.J., A.M.d.R., S.B.R., O.W.)
| | - J Huston
- Radiology (J.H., S.B.R., A.F., O.W.), University of Wisconsin, Madison, Wisconsin
| | - A M Del Rio
- From the Departments of Medical Physics (E.M.S., K.M.J., A.M.d.R., S.B.R., O.W.)
| | - S B Reeder
- From the Departments of Medical Physics (E.M.S., K.M.J., A.M.d.R., S.B.R., O.W.)Radiology (J.H., S.B.R., A.F., O.W.), University of Wisconsin, Madison, Wisconsin
| | - A Field
- Radiology (J.H., S.B.R., A.F., O.W.), University of Wisconsin, Madison, Wisconsin
| | - O Wieben
- From the Departments of Medical Physics (E.M.S., K.M.J., A.M.d.R., S.B.R., O.W.)Radiology (J.H., S.B.R., A.F., O.W.), University of Wisconsin, Madison, Wisconsin
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Kramer H, Corcos AR, Hernando D, Berry JF, Schiebler ML, Reeder SB. Effekt von molekularem Sauerstoff auf Relaxationszeiten bei klinischen Feldstärken. ROFO-FORTSCHR RONTG 2013. [DOI: 10.1055/s-0033-1346217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Kühn JP, Hernando D, Reeder SB, Hosten N. Stellenwert der Multispektralen Fettkorrektur für eine akkurate Bestimmung von Lebereisen und Leberfett in Chemical Shift Gradienten-Echo-Sequenzen. ROFO-FORTSCHR RONTG 2012. [DOI: 10.1055/s-0032-1311351] [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: 10/28/2022]
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Hernando D, Hines CDG, Yu H, Reeder SB. Addressing phase errors in fat-water imaging using a mixed magnitude/complex fitting method. Magn Reson Med 2012; 67:638-44. [PMID: 21713978 PMCID: PMC3525711 DOI: 10.1002/mrm.23044] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [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: 02/12/2011] [Revised: 04/20/2011] [Accepted: 05/21/2011] [Indexed: 11/12/2022]
Abstract
Accurate, noninvasive measurements of liver fat content are needed for the early diagnosis and quantitative staging of nonalcoholic fatty liver disease. Chemical shift-based fat quantification methods acquire images at multiple echo times using a multiecho spoiled gradient echo sequence, and provide fat fraction measurements through postprocessing. However, phase errors, such as those caused by eddy currents, can adversely affect fat quantification. These phase errors are typically most significant at the first echo of the echo train, and introduce bias in complex-based fat quantification techniques. These errors can be overcome using a magnitude-based technique (where the phase of all echoes is discarded), but at the cost of significantly degraded signal-to-noise ratio, particularly for certain choices of echo time combinations. In this work, we develop a reconstruction method that overcomes these phase errors without the signal-to-noise ratio penalty incurred by magnitude fitting. This method discards the phase of the first echo (which is often corrupted) while maintaining the phase of the remaining echoes (where phase is unaltered). We test the proposed method on 104 patient liver datasets (from 52 patients, each scanned twice), where the fat fraction measurements are compared to coregistered spectroscopy measurements. We demonstrate that mixed fitting is able to provide accurate fat fraction measurements with high signal-to-noise ratio and low bias over a wide choice of echo combinations.
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Affiliation(s)
- D Hernando
- Department of Radiology, University of Wisconsin, Madison, Wisconsin 53705, USA.
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Frydrychowicz A, Landgraf BR, Niespodzany E, Verma RW, Roldán-Alzate A, Johnson KM, Wieben O, Reeder SB. Four-dimensional velocity mapping of the hepatic and splanchnic vasculature with radial sampling at 3 tesla: a feasibility study in portal hypertension. J Magn Reson Imaging 2011; 34:577-84. [PMID: 21751287 DOI: 10.1002/jmri.22712] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2011] [Accepted: 06/07/2011] [Indexed: 12/26/2022] Open
Abstract
PURPOSE To demonstrate the feasibility of PC-VIPR (Phase Contrast Vastly undersampled Imaging with Projection Reconstruction) for the depiction and hemodynamic analysis of hepatic and splanchnic vessels in patients with portal hypertension. MATERIALS AND METHODS Twenty-four cirrhotic patients (55.9 ± 10.4 years) were scanned using 5-point PC-VIPR for high spatial resolution imaging with large volume coverage at 3 Tesla (T) using a 32-channel body coil. Vessel segmentation and hemodynamic visualization included color-coded three-dimensional (3D) streamlines and particle traces. Segmentation quality was compared with contrast-enhanced multi-phase liver imaging. Flow pattern analysis was performed in consensus of three readers. The MELD score was calculated to estimate disease severity and was correlated to image quality. RESULTS Good to excellent visualization quality was achieved in 23/24 cases. All arterial vessels and 144/168 vessels of the portal venous (PV) circulation were unambiguously identified. No correlation with the MELD score was found. Eight of 148 vessels of the PV circulation demonstrated reverse (hepatofugal) flow. Hepatofugal flow in small tributaries to PV flow were present in three cases despite hepatopetal flow in the PV. CONCLUSION This feasibility study demonstrates the feasibility of PC-VIPR for simultaneous morphological and hemodynamic assessment of the hepatic and splanchnic vasculature in cirrhosis and portal hypertension. Future studies with quantitative analyses are warranted.
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Affiliation(s)
- A Frydrychowicz
- Department of Radiology, University of Wisconsin-Madison, Wisconsin 53729, USA.
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Bley T, Chase P, Reeder SB, Francois CJ, Shinki K, Tefera G, Ranallo F, Grist T, Pozniak M. Volumetrisches Nativ-CT zur Detektion von Endoleaks nach EVAR der infrarenalen Aorta. ROFO-FORTSCHR RONTG 2011. [DOI: 10.1055/s-0031-1279183] [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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Frydrychowicz A, Nagle SK, D'Souza S, Reeder SB. Hochauflösende hepatobiliäre MR-Bildgebung bei 3T: Flipwinkel-Optimierung und direkter Vergleich von 0.05mmol/kg Gadoxetsäure (Primovist) und 0.1mmol/kg Gadobenate Dimeglumine (MultiHance). ROFO-FORTSCHR RONTG 2011. [DOI: 10.1055/s-0031-1279286] [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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Frydrychowicz A, Landgraf B, Niespodzany E, Verma RW, Roldan A, Wieben O, Reeder SB. 4D Flussmessung und Visualisierung der Leber- und Oberbauchgefäße mittels PC-VIPR. ROFO-FORTSCHR RONTG 2011. [DOI: 10.1055/s-0031-1279184] [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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Wintersperger BJ, Bauner K, Reeder SB, Dietrich O, Sprung KC, Reiser MF, Schoenberg SO. Accelerated Cardiac CINE MR Imaging on Multi-Channel 3 Tesla: Comparison of Signal Parameters and Volumetric Accuracy to 1.5 Tesla. ROFO-FORTSCHR RONTG 2006. [DOI: 10.1055/s-2005-931832] [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: 10/19/2022]
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Wintersperger BJ, Bauner K, Reeder SB, Dietrich O, Sprung KC, Reiser MF, Schoenberg SO. Accelerated Cardiac CINE MR Imaging on Multi-Channel 3 Tesla: Comparison of Signal Parameters and Volumetric Accuracy to 1.5 Tesla. ROFO-FORTSCHR RONTG 2006. [DOI: 10.1055/s-2006-931863] [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: 10/27/2022]
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18
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Wintersperger BJ, Bauner KU, Reeder SB, Sprung KC, Dietrich O, Theisen D, Greiser A, Reiser M, Schoenberg SO. CINE MRT mit paralleler Bildgebung bei 3 Tesla: Signal Parameter und volumetrische Genauigkeit im Vergleich zu 1,5 Tesla. ROFO-FORTSCHR RONTG 2006. [DOI: 10.1055/s-2006-940658] [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: 10/20/2022]
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19
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Kornaat PR, Reeder SB, Koo S, Brittain JH, Yu H, Andriacchi TP, Gold GE. MR imaging of articular cartilage at 1.5T and 3.0T: comparison of SPGR and SSFP sequences. Osteoarthritis Cartilage 2005; 13:338-44. [PMID: 15780647 DOI: 10.1016/j.joca.2004.12.008] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2004] [Accepted: 12/24/2004] [Indexed: 02/02/2023]
Abstract
OBJECTIVE To compare articular cartilage signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and thickness measurements on a 1.5 T and a 3.0 T magnetic resonance (MR) scanner using three-dimensional spoiled gradient recalled echo (3D-SPGR) and two 3D steady-state free precession (SSFP) sequences. METHODS Both knees of five volunteers were scanned at 1.5 T and at 3.0 T using a transmit-receive quadrature extremity coil. Each examination consisted of a sagittal 3D-SPGR sequence, a sagittal fat suppressed 3D-SSFP (FS-SSFP) sequence, and a sagittal Dixon 3D-SSFP sequence. For quantitative analysis, we compared cartilage SNR and CNR efficiencies, as well as average cartilage thickness measurements. RESULTS For 3D-SPGR, cartilage SNR efficiencies at 3.0 T increased compared to those at 1.5 T by a factor of 1.83 (range: 1.40-2.09). In comparison to 3D-SPGR, the SNR efficiency of FS-SSFP increased by a factor of 2.13 (range: 1.81-2.39) and for Dixon SSFP by a factor of 2.39 (range: 1.95-2.99). For 3D-SPGR, CNR efficiencies between cartilage and its surrounding tissue increased compared to those at 1.5 T by a factor of 2.12 (range: 1.75-2.47), for FS-SSFP by a factor 2.11 (range: 1.58-2.80) and for Dixon SSFP by a factor 2.39 (range 2.09-2.83). Average cartilage thicknesses of load bearing regions were not different at both field strengths or between sequences (P>0.05). Mean average cartilage thickness measured in all knees was 2.28 mm. CONCLUSION Articular cartilage imaging of the knee on a 3.0 T MR scanner shows increased SNR and CNR efficiencies compared to a 1.5 T scanner, where SSFP-based techniques show the highest increase in SNR and CNR efficiency. There was no difference between average cartilage thickness measurements performed at the 1.5 T and 3.0 T scanners or between the three different sequences.
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Affiliation(s)
- P R Kornaat
- Department of Radiology, Stanford University, Stanford, CA, USA.
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20
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Abstract
OBJECTIVE Treatment of iatrogenic femoral artery pseudoaneurysms with thrombin injection has been reported as an efficacious and safe procedure. The major risk of this procedure is distal limb ischemia from thrombosis, resulting from thrombin escape. The cumulative average dose of thrombin reported in the literature is approximately 1100 U per patient. Minimizing the thrombin dose may reduce the risks of the procedure. This study reports our experience with low-dose thrombin injection for the treatment of pseudoaneurysms. MATERIALS AND METHODS Twenty-three patients with 26 postcatheterization femoral pseudoaneurysms were administered thrombin injection with color-flow Doppler sonographic guidance. Pseudoaneurysm volume ranged from 1 to 41 cm(3) with an average of 6.7 cm(3) and a median of 4 cm(3). Two patients received therapeutic doses of IV heparin for anticoagulation. When possible, the neck of the pseudoaneurysm was occluded during the injection to promote stagnation and prevent thrombin leakage. Sonographic follow-up was routinely performed after 24 hr. RESULTS An average dose of 192 U of thrombin was used (range, 50-450 U), and time to coagulation ranged from 10 to 60 sec. All 26 pseudoaneurysms were successfully thrombosed, although one required repeated treatment because of recanalization noted at 1-day follow-up. There were no complications. CONCLUSION Doses of thrombin at an average of fivefold lower than previously reported were effective in the treatment of 26 iatrogenic femoral pseudoaneurysms, even in the presence of anticoagulation. This experience shows that a much smaller dose of a potentially dangerous medication can achieve the same efficacy as previously used higher doses.
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Affiliation(s)
- S B Reeder
- Department of Radiology, Stanford University, 300 Pasteur Ave., Stanford, CA 94305, USA
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21
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Abstract
Important advances in rapid magnetic resonance (MR) imaging technology and its application to cardiovascular imaging have been made during the past decade. High-field-strength clinical magnets, high-performance gradient hardware, and ultrafast pulse sequence technology are rapidly making the vision of a comprehensive "one-stop shop" cardiac MR imaging examination a reality. This examination is poised to have a significant effect on the management of coronary artery disease by means of assessment of wall motion with tagging and pharmacologic stress testing, evaluation of the coronary microvasculature with perfusion imaging, and direct visualization of the coronary arteries with MR coronary angiography. This article reviews current state-of-the-art pulse sequence technology and its application to the evaluation of ischemic heart disease by means of MR tagging with dobutamine stress testing, MR perfusion imaging, and MR coronary angiography. Cutting edge areas of research in coil design and exciting new areas of metabolic and oxygen level-dependent imaging are also explored.
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Affiliation(s)
- S B Reeder
- Department of Radiology, Rm H1306, Stanford University, 300 Pasteur Dr, Stanford, CA 94304, USA.
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22
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Abstract
Cardiac magnetic resonance imaging is a rapidly emerging field that has seen tremendous advances in the past decade. Central to the development of effective imaging strategies has been the advent of high-performance gradient hardware and the exploitation of their speed characteristics through specialized pulse sequences well suited for cardiac imaging. These advances have facilitated unprecedented acquisition times that now approach echocardiographic frame rates, while maintaining excellent image quality. This article provides a detailed overview of advanced pulse sequence technology and approaches currently taken to maximize speed performance and image quality. In particular, segmented K-space techniques that include single-echo and multiecho spoiled gradient-echo imaging as well as steady-state free precession imaging are discussed. Finally, spiral and fast spin-echo techniques are explored. Examples of common applications of these pulse sequences are presented.
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Affiliation(s)
- S B Reeder
- Department of Radiology, Stanford University, California, USA
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23
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Reeder SB, Holmes AA, McVeigh ER, Forder JR. Simultaneous noninvasive determination of regional myocardial perfusion and oxygen content in rabbits: toward direct measurement of myocardial oxygen consumption at MR imaging. Radiology 1999; 212:739-47. [PMID: 10478241 PMCID: PMC2041908 DOI: 10.1148/radiology.212.3.r99se27739] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine whether myocardial arterial perfusion and oxygen concentration can be quantified simultaneously from the same images by using spin labeling and the blood oxygenation level-dependent (BOLD) effect with fast spin-echo (SE) imaging. MATERIALS AND METHODS A T2-weighted fast SE pulse sequence was written to image isolated, arrested, blood-perfused rabbit hearts (n = 6) at 4.7 T. Perfusion images with intensity in units of milliliters per minute per gram that covered the entire left ventricle with 0.39 x 0.39 x 3.00-mm resolution were obtained in less than 15 minutes with a 32-fold reduction in imaging time from that of a previous study. Estimates of oxygen concentration were made from the same images acquired for calculation of perfusion images. RESULTS Estimates of regional myocardial oxygen content could be made from the perfusion images; this demonstrated the feasibility of three-dimensional calculation of regional oxygen consumption, which requires concomitant measurement of both oxygen content and flow. Fast SE imaging was shown to be as sensitive to hemoglobin desaturation as standard SE imaging. Perfusion abnormalities and oxygen deficits were easily identified and verified qualitatively with gadopentetate dimeglumine on both perfusion and BOLD images obtained after coronary arterial ligation. CONCLUSION T2-weighted fast SE imaging combined with perfusion-sensitive spin labeling can be used to measure myocardial arterial perfusion and oxygen concentration. This provides the groundwork for calculation of regional myocardial oxygen consumption.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Md., USA
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24
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Abstract
Interleaved echo-planar imaging (EPI) is susceptible to significant ghosting artifacts, resulting primarily from system time delays that cause data matrix misregistration. Most EPI applications rely on "reference scans" to measure delays, and post-processing algorithms are used to correct these errors. Unfortunately, delay estimates made with most reference scan techniques are object dependent, since they are biased by magnetic field inhomogeneities and chemical shift. The current work describes the effects of field inhomogeneities and their influence on system time delay estimation. Subsequently, a new, object-independent "balanced" reference method using two readout echo trains is proposed for time delay measurements.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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25
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Abstract
To investigate the effects of water exchange on quantification of perfusion, data were acquired in isolated hearts (n = 11) and used to develop a model of exchange. Myocardial T1 was measured 3 times/sec during step changes in concentration of intravascular (polylysine-gadolinium-diethylene-triamine-pentaacetic acid) and extracellular (gadoteridol) agents. For the intravascular agent, the change in 1/T1 (deltaR1) was lower than predicted by fast exchange (2.7+/-0.5 vs. 7.8 sec(-1), respectively), and suggested an intra-extravascular exchange rate of 3 Hz. For the extracellular agent, contrast kinetics were similar to those of similarly sized molecules (wash-in time constant 38+/-5 sec), and the data suggested fast interstitial-cellular exchange. Modeling showed that perfusion is underestimated for both agents if exchange is ignored, although the relationships of measured to actual perfusion were monotonic. We conclude that myocardial water exchange strongly affects first-pass enhancement but that ignoring the effects of exchange may still provide reasonable estimates of regional perfusion differences.
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Affiliation(s)
- R M Judd
- Feinberg Cardiovascular Research Institute, Northwestern University Medical School, Chicago, Illinois 60611-3008, USA.
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26
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Abstract
Cardiac magnetic resonance imaging requires high temporal resolution to resolve motion and contrast uptake with low total scan times to avoid breathing artifacts. While spoiled gradient echo (SPGR) imaging is robust and reproducible, it is relatively inefficient and requires long breath-holds to acquire high time resolution movies of the heart. Echo planar imaging (EPI) is highly efficient with excellent signal-to-noise ratio (SNR) behavior; however, it is particularly difficult to use in the heart because of its sensitivity to chemical shift, susceptibility, and motion. EPI may also require reference scans, which are used to measure hardware delays and phase offsets that cause ghosting artifacts; these reference scans are more difficult and less reliable in the heart. Consequently, a hybrid EPI/SPGR sequence is proposed for application to rapid cardiac imaging. A detailed optimization of SNR and echo train length for multi-echo sequences is presented. It is shown that significant reductions in total scan time are possible while maintaining good image quality. This will allow complete motion sampling of the entire heart in one to three breath-holds, necessary for MR cardiac dobutamine stress testing. Improved speed performance also permits sampling of three to six slices every heartbeat for bolus injection perfusion studies.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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27
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Abstract
Interleaved echo-planar imaging (EPI) is an ultrafast imaging technique important for applications that require high time resolution or short total acquisition times. Unfortunately, EPI is prone to significant ghosting artifacts, resulting primarily from system time delays that cause data matrix misregistration. In this work, it is shown mathematically and experimentally that system time delays are orientation dependent, resulting from anisotropic physical gradient delays. This analysis characterizes the behavior of time delays in oblique coordinates, and a new ghosting artifact caused by anisotropic delays is described. "Compensation blips" are proposed for time delay correction. These blips are shown to remove the effects of anisotropic gradient delays, eliminating the need for repeated reference scans and postprocessing corrections. Examples of phantom and in vivo images are shown.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, John Hopkins University School of Medicine, Baltimore, Maryland 21287-0845, USA
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28
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Rochitte CE, Lima JA, Bluemke DA, Reeder SB, McVeigh ER, Furuta T, Becker LC, Melin JA. Magnitude and time course of microvascular obstruction and tissue injury after acute myocardial infarction. Circulation 1998; 98:1006-14. [PMID: 9737521 DOI: 10.1161/01.cir.98.10.1006] [Citation(s) in RCA: 362] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Microvascular obstruction within an area of myocardial infarction indicates worse functional recovery and a higher risk of postinfarction complications. After prolonged coronary occlusion, contrast-enhanced MRI identifies myocardial infarction as a hyperenhanced region containing a hypoenhanced core. Because the time course of microvascular obstruction after infarction/reperfusion is unknown, we examined whether microvascular obstruction reaches its full extent shortly after reperfusion or shows significant progression over the following 2 days. METHODS AND RESULTS Seven dogs underwent 90-minute balloon occlusion of the left anterior descending coronary artery (LAD) followed by reflow. Gadolinium-DTPA-enhanced MRI performed at 2, 6, and 48 hours after reperfusion was compared with radioactive microsphere blood flow (MBF) measurements and myocardial staining to define microvascular obstruction (thioflavin S) and infarct size (triphenyltetrazolium chloride, TTC). The MRI hypoenhanced region increased 3-fold during 48 hours after reperfusion (3.2+/-1.8%, 6.7+/-4.4%, and 9.9+/-3.2% of left ventricular mass at 2, 6, and 48 hours, respectively, P<0.03) and correlated well with microvascular obstruction (MBF <50% of remote region, r=0.99 and thioflavin S, r=0.93). MRI hyperenhancement also increased (21.7+/-4.0%, 24.3+/-4.6%, and 28.8+/-5.1% at 2, 6, and 48 hours, P<0.006) and correlated well with infarct size by TTC (r=0.92). The microvascular obstruction/infarct size ratio increased from 13.0+/-4.8% to 22.6+/-8.9% and to 30.4+/-4.2% over 48 hours (P=0.024). CONCLUSION The extent of microvascular obstruction and the infarct size increase significantly over the first 48 hours after myocardial infarction. These results are consistent with progressive microvascular and myocardial injury well beyond coronary occlusion and reflow.
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Affiliation(s)
- C E Rochitte
- Department of Medicine, Johns Hopkins University, Baltimore, MD, USA
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29
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Hsu EW, Reeder SB, MacFall JR. Single-shot, variable flip-angle slice-selective excitation with four gradient-modulated adiabatic half-passage segments. Magn Reson Med 1998; 40:334-40. [PMID: 9702716 DOI: 10.1002/mrm.1910400220] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Adiabatic pulses, although useful in generating uniform spin nutation in the presence of inhomogeneous B1 fields, are limited for NMR imaging applications due to the lack of slice-selective excitation capability. Selective excitation techniques using gradient modulation have been introduced; however, present methods require either a minimum of two excitations or eight adiabatic segments. Here, a scheme is presented that allows single-shot, arbitrary flip-angle, and slice-selective excitation with only four adiabatic half-passage segments. The technique is demonstrated via computer simulation and experimental tests on a phantom. Furthermore, issues associated with the implementation of these gradient-modulated adiabatic pulses are discussed.
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Affiliation(s)
- E W Hsu
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA.
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30
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Abstract
Cardiac echo-planar imaging suffers invariably from regions of severe distortion and T*2 decay in the myocardium. The purpose of this work was to perform local measurements of T*2 and field inhomogeneities in the myocardium and to identify the sources of focal signal loss and distortion. Field inhomogeneity maps and T*2 were measured in five normal volunteers in short-axis slices spanning from base to apex. It was found that T*2 ranged from 26 ms (SD = 7 ms, n = 5) to 41 ms (SD = 11 ms, n = 5) over most of the heart, and peak-to-peak field inhomogeneity differences were 71 Hz (SD = 14 Hz, n = 5). In all hearts, regions of severe signal loss were consistently adjacent to the posterior vein of the left ventricle; T*2 in these regions was 12 ms (SD = 2 ms, n = 5), and the difference in resonance frequency with the surrounding myocardium was 70-100 Hz. These effects may be caused by increased magnetic susceptibility from deoxygenated blood in these veins.
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Affiliation(s)
- S B Reeder
- Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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31
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Abstract
A mathematical analysis of ghosting artifacts often seen in interleaved echo-planar images (EPI) is presented. These artifacts result from phase and amplitude discontinuities between lines of k-space in the phase-encoding direction, and timing misregistrations from system filter delays. Phase offsets and time delays are often measured using "reference" scans, to reduce ghosting through postprocessing. From the expressions describing ghosting artifacts, criteria were established for reducing ghosting to acceptable levels. Subsequently, the signal-to-noise ratio (SNR) requirements for estimation of time delays and phase offsets, determined from reference scans, was evaluated to establish the effect of estimation error on artifact reduction for interleaved EPI. Artifacts resulting from these effects can be reduced to very low levels when appropriate reference scan estimation is used. This has important implications for functional MRI (fMRI) and applications involving small changes in signal intensity.
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Affiliation(s)
- S B Reeder
- Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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32
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Kim RJ, Lima JA, Chen EL, Reeder SB, Klocke FJ, Zerhouni EA, Judd RM. Fast 23Na magnetic resonance imaging of acute reperfused myocardial infarction. Potential to assess myocardial viability. Circulation 1997; 95:1877-85. [PMID: 9107176 DOI: 10.1161/01.cir.95.7.1877] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The ability of the myocyte to maintain an ionic concentration gradient is perhaps the best indication of myocardial viability. We studied the relationship of 23Na MRI intensity to viability and explored the potential of fast-imaging techniques to reduce 23Na imaging times in rabbits and dogs. METHODS AND RESULTS Eighteen rabbits underwent in situ coronary artery occlusion and reperfusion. The hearts were then either imaged following isolation and perfusion with cardioplegic solution (n = 6), imaged in vivo (n = 6), or analyzed for 23Na content and relaxation times (n = 12). Normal rabbits (n = 6) and dogs (n = 4) were imaged to examine the effect of animal size on 23Na image quality. 23Na imaging times were 7, 11, and 4 minutes for isolated rabbits, in vivo rabbits, and in vivo dogs, respectively. Infarcted, reperfused regions, identified by triphenyltetrazolium chloride staining, showed a significant elevation in 23Na image intensity compared with viable regions (isolated, 42 +/- 5%, P < .02; in vivo, 95 +/- 6%, P < .001), consistent with increased tissue sodium content. Similarly, 23Na MR spectroscopy showed that [Na+] was higher in nonviable than viable myocardium (isolated, 99 +/- 4 versus 61 +/- 2 mmol/L; in vivo, 91 +/- 2 versus 38 +/- 1 mmol/L; P < .001 for both). Image signal-to-noise ratios were higher in dogs than rabbits despite shorter imaging times, primarily due to larger voxels. CONCLUSIONS Following acute infarction with reperfusion, a regional increase in 23Na MR image intensity is associated with nonviable myocardium. Fast gradient-echo imaging techniques reduce 23Na imaging times to a few minutes, suggesting that 23Na MR imaging has the potential to become a useful experimental and clinical tool.
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Affiliation(s)
- R J Kim
- Johns Hopkins Medical Institutions (R.J.K., J.A.C.L., S.B.R., E.A.Z.), Baltimore, Md, USA
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Rehwald WG, Reeder SB, McVeigh ER, Judd RM. Techniques for high-speed cardiac magnetic resonance imaging in rats and rabbits. Magn Reson Med 1997; 37:124-30. [PMID: 8978641 PMCID: PMC2396294 DOI: 10.1002/mrm.1910370118] [Citation(s) in RCA: 12] [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] [Subscribe] [Scholar Register] [Received: 12/26/1995] [Accepted: 07/17/1996] [Indexed: 02/03/2023]
Abstract
Progress in research on hypertension, heart failure, aging, post-infarct remodeling, and the molecular basis of cardiovascular diseases in general has been greatly facilitated in recent years by the development of specialized small-mammal models by selective breeding and/or genetic alteration. Routine noninvasive evaluation of cardiac function and perfusion in these animals models, however, is difficult using existing methods. In principle, MRI can be used for this purpose, but in practice this is difficult because of problems related to RF coils, cardiac gating, and imaging pulse sequences. In this article, solutions to these problems are described that have allowed us to use MRI to routinely image the hearts of rats and rabbits. Specifically described are four RF coils, cardiac gating schemes, and an imaging pulse sequence specially designed for cardiac imaging in these animals on a 4.7 T Omega chemical-shift imaging (CSI) spectrometer. These techniques can be used to obtain, within 2 min, eight double-oblique short-axis images of the rat at different cardiac phases with 200 x 400 microm in-plane resolution and a slice thickness of 2 mm. Moreover, myocardial tissue tagging can be performed with tag thicknesses and separations comparable to those used routinely in humans. The technical information is presented in sufficient detail to allow researchers at other sites to reproduce the results. This information should facilitate the use of MRI for the noninvasive examination of cardiac function and perfusion, which can be combined with other established techniques for the study of cardiovascular disease in specialized animal models.
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Affiliation(s)
- W G Rehwald
- Department of Radiology, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
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Abstract
PURPOSE To quantitate myocardial arterial perfusion with a noninvasive magnetic resonance (MR) imaging technique that exploits the geometry of coronary vessel anatomy. MATERIALS AND METHODS MR imaging was performed with a spin-labeling method in six arrested rabbit hearts at 4.7 T. Selective inversion of magnetization in the short-axis imaging section along with all myocardium apical to that section produces signal enhancement from arterial perfusion. A linescan protocol was used for validation of flow enhancement. Flow was quantitated from two images and validated with spin-echo (SE) imaging. Regional perfusion defects were created by means of coronary artery ligation and delineated with gadolinium-enhanced imaging. RESULTS Linescan estimates of T1 obtained at physiologic flows agreed with model predictions. Flow-induced signal enhancement measured on SE images also agreed with expected values. Finally, perfusion abnormalities created by means of coronary artery ligation were detected. CONCLUSION This spin-labeling method provides quantitative estimates of myocardial arterial perfusion in this model and may hold promise for clinical applications.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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35
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Abstract
An MR line scan protocol has been used to measure relaxation parameters (T1 and T2) in isolated, blood perfused rabbit hearts at various blood oxygenations. Hearts were retrogradely perfused at 37 degrees C with a cardioplegic solution (modified St. Thomas' solution) containing sheep red blood cells and adenosine (1 mM) to maximally vasodilate the coronary vascular bed. Arresting the hearts eliminated motion complications and minimized arteriovenous oxygenation differences. The authors have found that under conditions of stable flow, there is a strong correlation between T2 in myocardial septa and hemoglobin (Hb) saturation, while tissue T1 is virtually independent of blood oxygenation. These effects are believed to be due to the paramagnetic agent deoxyhemoglobin.
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Affiliation(s)
- M K Atalay
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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36
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Abstract
A T1-weighted imaging pulse sequence for contrast-based studies of myocardial perfusion is presented and evaluated in phantoms and in vivo. The sequence is similar to spoiled gradient-recalled echo sequences except that nonselective preparatory RF pulses drive magnetization to steady state prior to image acquisition. Steady state is thus obtained in both tissue and blood resulting in a stable, homogeneous, and dark pre-contrast baseline. Tip angles and timings are chosen so that pixel intensity approximates a linear relation to 1/T1. The dynamic range of signal response to contrast agent concentration is greater than that of an inversion-recovery fast low angle shot sequence. The sequence proposed should be useful for myocardial perfusion studies.
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Affiliation(s)
- R M Judd
- Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
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37
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Abstract
The effect of gradient system performance on segmented k-space gradient echo imaging is presented. Three cases were investigated. First, an ideal system that has infinite slew rates and unlimited maximum gradient strengths was considered. Second, a "high speed" imaging system (2.3 (G/cm), 23 (G/cm)/ms) was considered. These two cases were compared with a "conventional" imaging system (1(G/cm), 1.67 (G/cm)/ms). It was found that substantial increases in SNR can be achieved (approximately 45%) by using high speed versus a conventional gradient system, for a TR of 6 ms. For trapezoidal gradient waveforms, there exists an optimum maximum gradient strength for a given slew rate, and any increase in gradient strength above this optimum will not be utilized by an optimized sequence. These studies have shown that increasing TR without decreasing the bandwidth is not a good way to increase SNR for constant scan time.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering and Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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38
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Abstract
Contrast between tagged and nontagged myocardium was investigated using rapid gradient echo segmented k-space CINE MRI. The transient behavior of magnetization was measured in stationary and moving phantoms using gradient recalled acquisition in steady-state GRASS and spoiled GRASS (SPGR) sequences with TR approximately 7 ms and TE approximately 2.5 ms. Bloch equation simulations were used to compute theoretical results. Understanding the transient behavior of magnetization is important because tags only persist in the myocardium during the nonequilibrium transition to steady state. The transition to steady state for both SPGR and GRASS is reproducible after one heartbeat, and including unprocessed data from the first heartbeat leads to image artifacts. In a moving phantom, simulations and experimental results showed that GRASS and SPGR are essentially equivalent. Tag-tissue contrast in SPGR was very sensitive to imaging tip angle. The optimum tip angle for the scanning parameters used in this study was 11 degrees.
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Affiliation(s)
- S B Reeder
- Department of Biomedical Engineering, Hopkins University School of Medicine, Baltimore, Maryland 21205
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39
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Abstract
PURPOSE To validate cine magnetic resonance (MR) image tagging measurements of a deforming object by means of a precise photographic method. MATERIALS AND METHODS A piece of silicone rubber that acted as a phantom was stretched in a cyclical fashion inside a plastic clamp driven by a respirator pump. Deformation as a function of time was measured with a rapid gradient-echo cine tagging sequence and with sequential stroboscopic photographs. Deformations from 1.0 to 1.2 (0% to 20% stretch) in the readout direction were measured over a 7-cm region of the phantom, which had a maximum standard error of +/- 0.001 with photography and a maximum standard error of +/- 0.003 with MR imaging. RESULTS The deformation versus time values measured with MR imaging had a standard error of 0.002 about a straight line fit to the photographic deformation versus time data. These results demonstrate that the MR imaging deformation estimates were accurate and precise. CONCLUSION The validated tagging method can now be used to evaluate MR imaging motion estimation techniques.
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Affiliation(s)
- C C Moore
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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