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Arrhythmogenic Right Ventricular Dysplasia: Ex Vivo and in Vivo Fat Detection with Black-Blood MR Imaging¹

¹ From the Russell H. Morgan Dept of Radiology and Radiological Sciences (E.C., D.A.B.); Dept of Medicine, Div of Cardiology (H.T., K.N., J.R., H.C, J.A.C.L.); and Dept of Pathology (E.R.R), Johns Hopkins Univ School of Medicine, 600 N Wolfe St, MRI-143 Nelson Basement, Baltimore, MD 21287. Received May 19, 2003; revision requested July 31; revision received Oct 17; accepted Nov 25. The Johns Hopkins ARVD program is funded by a private grant from the Bogle Foundation. This study was supported in part by NIH research grant no. 1 UO1 HL65594–01A1. E.C. was supported by a research grant from the Fundación Ramón Areces, Madrid, Spain. Address correspondence to D.A.B (e-mail: dbluemke@jhmi.edu).

View larger version (88K): [in a new window]   Figure 1. Resolution insert for visual assessment of high spatial resolution. Each pair of hole arrays consists of upper left and lower right hole arrays with four rows of four holes each for assessment of resolution from right to left and top to bottom. Spacing between holes is 1.1, 1.0, and 0.9 mm from left to right. Images obtained with different protocols and a 5-mm section thickness are shown. A, High-spatial-resolution SE MR image (300/14, 14-cm FOV, 512 x 256 matrix) shows good resolution of all three hole diameters in the upper left and lower right arrays. B, ECG-gated SE MR image (one R-R/14, two signals acquired, 28-cm FOV, 256 x 192 matrix) shows well-resolved holes in all sizes along the frequency-encoding (anterior-posterior) direction but none along the phase-encoding (right-left) direction. C-E, Double inversion-recovery fast SE MR images with an ETL of 32, 28-cm FOV, and different TRs of double R-R (C) and single R-R (D and E, matrix sizes of 256 x 256 and 384 x 256, respectively). Along the frequency-encoding direction, the limiting spatial resolution was 1.0 mm for C and D and 0.9 mm for E because of increased resolution. Along the phase-encoding direction, all three fast SE images show limiting spatial resolution of 1.1 mm.

View larger version (112K): [in a new window]   Figure 2a. (a) Gross pathologic slice through RV free wall of cadaveric heart specimen obtained from 35-year-old woman who died suddenly. There is extensive fatty infiltration (arrows) from epicardium to endocardium along most of the RV free wall. (b) High-spatial-resolution SE MR image (300/14, 14-cm FOV, 512 x 256 matrix, 3-mm section thickness) obtained with a view equivalent to in vivo transverse plane shows extensive replacement of RV myocardium with fat (arrowheads) beyond original epicardial border. Calibration bar equals 4 cm. (c) Higher-magnification MR image demonstrates sheets of myocytes within hyperintense fingerlike infiltrating fat (arrowheads). (d) Light micrograph of same area as in c shows large amounts of fatty infiltration reaching the endocardium and fibrous tissue, which is characteristic of ARVD. In addition, there are spared myocytes (arrowheads) along original epicardial border. Note that endocardial border cannot be differentiated from trabeculae on the MR image, while it is clearly defined in the histologic slice. (Masson trichrome stain; original magnification, x5.5.)

View larger version (143K): [in a new window]   Figure 2b. (a) Gross pathologic slice through RV free wall of cadaveric heart specimen obtained from 35-year-old woman who died suddenly. There is extensive fatty infiltration (arrows) from epicardium to endocardium along most of the RV free wall. (b) High-spatial-resolution SE MR image (300/14, 14-cm FOV, 512 x 256 matrix, 3-mm section thickness) obtained with a view equivalent to in vivo transverse plane shows extensive replacement of RV myocardium with fat (arrowheads) beyond original epicardial border. Calibration bar equals 4 cm. (c) Higher-magnification MR image demonstrates sheets of myocytes within hyperintense fingerlike infiltrating fat (arrowheads). (d) Light micrograph of same area as in c shows large amounts of fatty infiltration reaching the endocardium and fibrous tissue, which is characteristic of ARVD. In addition, there are spared myocytes (arrowheads) along original epicardial border. Note that endocardial border cannot be differentiated from trabeculae on the MR image, while it is clearly defined in the histologic slice. (Masson trichrome stain; original magnification, x5.5.)

View larger version (117K): [in a new window]   Figure 2c. (a) Gross pathologic slice through RV free wall of cadaveric heart specimen obtained from 35-year-old woman who died suddenly. There is extensive fatty infiltration (arrows) from epicardium to endocardium along most of the RV free wall. (b) High-spatial-resolution SE MR image (300/14, 14-cm FOV, 512 x 256 matrix, 3-mm section thickness) obtained with a view equivalent to in vivo transverse plane shows extensive replacement of RV myocardium with fat (arrowheads) beyond original epicardial border. Calibration bar equals 4 cm. (c) Higher-magnification MR image demonstrates sheets of myocytes within hyperintense fingerlike infiltrating fat (arrowheads). (d) Light micrograph of same area as in c shows large amounts of fatty infiltration reaching the endocardium and fibrous tissue, which is characteristic of ARVD. In addition, there are spared myocytes (arrowheads) along original epicardial border. Note that endocardial border cannot be differentiated from trabeculae on the MR image, while it is clearly defined in the histologic slice. (Masson trichrome stain; original magnification, x5.5.)

View larger version (144K): [in a new window]   Figure 2d. (a) Gross pathologic slice through RV free wall of cadaveric heart specimen obtained from 35-year-old woman who died suddenly. There is extensive fatty infiltration (arrows) from epicardium to endocardium along most of the RV free wall. (b) High-spatial-resolution SE MR image (300/14, 14-cm FOV, 512 x 256 matrix, 3-mm section thickness) obtained with a view equivalent to in vivo transverse plane shows extensive replacement of RV myocardium with fat (arrowheads) beyond original epicardial border. Calibration bar equals 4 cm. (c) Higher-magnification MR image demonstrates sheets of myocytes within hyperintense fingerlike infiltrating fat (arrowheads). (d) Light micrograph of same area as in c shows large amounts of fatty infiltration reaching the endocardium and fibrous tissue, which is characteristic of ARVD. In addition, there are spared myocytes (arrowheads) along original epicardial border. Note that endocardial border cannot be differentiated from trabeculae on the MR image, while it is clearly defined in the histologic slice. (Masson trichrome stain; original magnification, x5.5.)

View larger version (109K): [in a new window]   Figure 3. Two RV sections from an 18-year-old woman who died suddenly while at rest. A, Gross pathologic specimen shows diffuse fatty infiltration (arrows) along RV myocardium. B, MR image obtained with a view equivalent to in vivo transverse plane with same SE sequence as that used in Figure 1 shows ill-defined hyperintensity that corresponds to fatty infiltration within RV myocardium (arrows) and preserved epicardial border (arrowheads). C, Higher-magnification MR image and, D, histologic specimen demonstrate predominantly fatty infiltration (arrows) along perforating branches of coronary arteries. This pattern is not specific for ARVD. In another slice obtained from same specimen (E-H), however, there is characteristic fatty infiltration pattern of ARVD. E, Transillumination of gross specimen shows paucity of myocardium deficiency in RV free wall secondary to fatty infiltration (arrows on E-H) with vanishing border of epicardial fat-myocardium interface (arrowheads on E-H). This correlates well with SE MR images (F, G) and histologic findings (H). (Masson trichrome stain; original magnification, x5.5.)

View larger version (29K): [in a new window]   Figure 4a. Graphs of CNR for fat signal intensity in RV free wall of cadaveric specimens with ARVD. (a) Values obtained with gated SE MR imaging are compared with those obtained with double inversion-recovery fast SE (DIR-FSE) MR imaging with TRs of single and double R-R intervals and a matrix of 256 x 256 pixels or 384 x 256 pixels for higher spatial resolution (DIR-FSE_HR). Absolute CNR values of gated SE images are more than double those obtained with fast SE imaging, although the SD is much higher than that on all fast SE images. As a constant, CNR values increase with larger section thickness with exception of high-spatial-resolution fast SE images (not a significant difference). (b) Results of spectrally selected fat suppression. Overall, absolute CNR values are between threefold (double R-R) and sixfold (single R-R) higher on MR images obtained with fat suppression than on those without. * = P < .05; ** = P > .05.

View larger version (37K): [in a new window]   Figure 4b. Graphs of CNR for fat signal intensity in RV free wall of cadaveric specimens with ARVD. (a) Values obtained with gated SE MR imaging are compared with those obtained with double inversion-recovery fast SE (DIR-FSE) MR imaging with TRs of single and double R-R intervals and a matrix of 256 x 256 pixels or 384 x 256 pixels for higher spatial resolution (DIR-FSE_HR). Absolute CNR values of gated SE images are more than double those obtained with fast SE imaging, although the SD is much higher than that on all fast SE images. As a constant, CNR values increase with larger section thickness with exception of high-spatial-resolution fast SE images (not a significant difference). (b) Results of spectrally selected fat suppression. Overall, absolute CNR values are between threefold (double R-R) and sixfold (single R-R) higher on MR images obtained with fat suppression than on those without. * = P < .05; ** = P > .05.

View larger version (106K): [in a new window]   Figure 5. Effect of ETL and section thickness on edge blurring for same specimen as in Figure 3. All images have 5-mm section thickness and were obtained with a view equivalent to the in vivo transverse plane. A, High-spatial-resolution SE MR image (14-cm FOV, 512 x 256 matrix). B, ECG-gated SE MR image with spatial resolution used clinically (28-cm FOV, 256 x 192 matrix). Note substantial loss in fat depiction on gated SE image. C-F, Double inversion-recovery fast SE (DIR-FSE) MR images (double R-R/30; increasing ETL of 12, 16, 24, and 32 for C, D, E, and F, respectively) show increasing edge blurring with loss in resolution of fatty changes. G-N, Fast SE (one R-R/5) MR images with identical ETL and matrix of 256 x 256 (G-J) and increased matrix of 384 x 256 along the frequency-encoding direction (K-N). Increased blurring is caused by shorter TE and slightly increased resolution of fatty changes with increased matrix size (arrowheads).

View larger version (113K): [in a new window]   Figure 6. Effect of fat suppression on depiction of intramyocardial fatty foci, same as in Figure 3, E. A, Transverse SE image (300/14, 14-cm FOV, 512 x 256 matrix) shows extensive intramyocardial fatty infiltration. In the middle and right third of the image, this is a nearly transmural fingerlike pattern of hyperintensity that extends from the epicardium toward the endocardium. As a consequence, there is an ill-defined and almost lost epicardial fat-myocardium interface. B, Same area imaged with gated SE MR imaging (single R-R/14, 28-cm FOV, 256 x 192 matrix) again shows barely resolved intramyocardial fatty changes. C-F, Double inversion-recovery fast SE (DIR-FSE) images (double R-R/30) with increasing ETLs (12, 16, 24, and 32, respectively) provide better depiction of fatty changes than that on gated SE images despite increasing loss of contrast with longer ETLs. G-J, Images obtained with the same fast SE sequence with addition of fat suppression show high contrast between preserved RV myocardium and infiltrated areas despite adverse effects of increasing ETL. Note that clinically, only ETLs of 32 or 24 are reasonably achievable within constraint of breath-hold imaging. All sections were obtained with 5-mm section thickness.

View larger version (67K): [in a new window]   Figure 7a. Clinical application of optimized MR pulse sequence. (a) MR image in a 45-year-old woman with histologically proved ARVD. Transverse double inversion-recovery fast SE image (double R-R/30, ETL of 32) shows hyperintensity within RV free wall (subtricuspid and midwall regions, arrows) beyond original epicardial border (arrowheads), which corresponds to fatty infiltration. (b) Similar findings are observed for a 35-year-old woman with a diagnosis of ARVD based on standard criteria. Again, on the transverse image there is extensive fatty infiltration of the RV myocardium along the free wall (arrows) beyond the original epicardial border (arrowheads).

View larger version (83K): [in a new window]   Figure 7b. Clinical application of optimized MR pulse sequence. (a) MR image in a 45-year-old woman with histologically proved ARVD. Transverse double inversion-recovery fast SE image (double R-R/30, ETL of 32) shows hyperintensity within RV free wall (subtricuspid and midwall regions, arrows) beyond original epicardial border (arrowheads), which corresponds to fatty infiltration. (b) Similar findings are observed for a 35-year-old woman with a diagnosis of ARVD based on standard criteria. Again, on the transverse image there is extensive fatty infiltration of the RV myocardium along the free wall (arrows) beyond the original epicardial border (arrowheads).

View larger version (170K): [in a new window]   Figure 8. Clinical example of fat suppression use. Transverse double inversion-recovery fast SE MR images obtained in a 46-year-old woman with a diagnosis of ARVD. A-C, Images obtained without fat suppression. D-F, Images obtained with spectrally selected fat suppression. Images correspond to RV outflow tract (A, B) and two different levels of RV free wall (C-F). There is extensive intramural fatty infiltration (arrows) along entire free wall and RV outflow tract, which is better delineated from remaining myocardium and trabeculae on fat-suppressed images. Original endocardial border can be seen as a hypointense line (arrowheads) on all sections.