Three-Dimensional MRI of the Musculoskeletal System

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1 Musculoskeletal Imaging Review Naraghi and White 3D MRI of the Musculoskeletal System Musculoskeletal Imaging Review FOCUS ON: li Naraghi 1 Lawrence M. White Naraghi, White LM Keywords: 3D MRI, articular cartilage, isotropic imaging, joint derangement, MRI, musculoskeletal DOI: /JR Received pril 18, 2012; accepted after revision May 17, oth authors: Joint Department of Medical Imaging, Mount Sinai Hospital, University of Toronto, 600 University ve, Toronto, ON M5G 1X5, Canada. ddress correspondence to L. M. White (lwhite@mtsinai.on.ca). WE This is a Web exclusive article. JR 2012; 199:W283 W X/12/1993 W283 merican Roentgen Ray Society Three-Dimensional MRI of the Musculoskeletal System OJECTIVE. The purposes of this review are to describe commonly available 3D MRI techniques and to discuss the literature to date regarding the utility of such techniques in the assessment of internal derangement of joints. CONCLUSION. Long acquisition and postprocessing times and limited contrast characteristics have generally prohibited routine use of 3D MRI in clinical practice. However, technical advances, including higher-field-strength MRI systems, high performance gradients, high-resolution multichannel coils, and pulse sequences with shorter acquisition times, have made feasible 3D isotropic MRI with reasonable acquisition times. W ith its excellent soft-tissue contrast and multiplanar capabilities, MRI has become well established as a fundamental modality for assessment of musculoskeletal abnormalities. Until recently, however, in routine clinical practice modern CT has had an advantage over MRI in its capability of high-quality isotropic 3D acquisition and multiplanar reformatting [1, 2]. lthough it is true that 3D MRI pulse sequences have been incorporated into routine MRI protocols at many institutions for a number of years, the clinical application has been typically limited to cartilage imaging and imaging of the wrist. Furthermore, many of the older pulse sequences did not involve acquisition of truly isotropic datasets, resulting in lower quality of multiplanar reformats. dvantages of 3D isotropic acquisitions include improved through-plane spatial resolution and the ability to generate high-quality reformats to yield multiplanar images from the original acquisition dataset [3]. The improved through-plane resolution reduces partial volume artifacts as a result of the thin contiguous slices, potentially enhancing the ability to detect more-subtle injuries, which may be overlooked with standard MRI (Fig. 1). Furthermore, many anatomic structures in the musculoskeletal system are obliquely oriented to the standard anatomic orthogonal imaging planes, and dedicated oblique acquisitions have been recommended by some authors [4 7] as necessary adjuncts to routine triplanar imaging protocols to improve diag- nostic assessment of joint abnormalities. Use of 3D isotropic pulse sequences allows generation of multiple high-quality postprocessing reformats from an original isotropic data acquisition along any user-defined imaging plane (Fig. 2) without the time penalty of direct oblique acquisitions. dditional postprocessing techniques allow the modification of through-plane slice thickness, which allows user-defined improvements in image signal intensity with increases in reformatted image slab thickness and associated increases in image voxel dimensions. ecause of these potential advantages, isotropic 3D sequences may be used in theory to either supplement 2D fast spin-echo (FSE) pulse sequences or reduce the number of sequences performed in routine clinical MRI owing to the ability to perform postacquisition multiplanar reformatting. lthough it has been possible to acquire 3D MR images for a number of years, the long acquisition and postprocessing times have traditionally been prohibitive for incorporation of these pulse sequences into clinical practice [8, 9]. number of technologic advances, however, have made 3D MRI in routine practice a reality. These advances include higher-fieldstrength MRI systems, high performance gradients, high-resolution dedicated multichannel coils, and pulse sequences with shorter acquisition times. s a result, the ability to acquire high-resolution isotropic datasets in a reasonable time has been realized. The result has been improvement in the quality of reformations in comparison with many early 3D MRI JR:199, September 2012 W283

2 Naraghi and White acquisitions which commonly relied on nonisotropic acquisitions to facilitate imaging with appropriate signal to noise in clinically feasible acquisition times. In addition, postprocessing times, which were often in excess of 20 minutes [9], have decreased substantially owing to improved workstation processing speeds, postprocessing software, and semiautomated reformation. This review describes the more commonly available 3D MRI techniques and discusses the literature regarding the utility of these techniques in assessment of internal derangement of joints. Three-Dimensional MRI Pulse Sequences variety of 3D MRI pulse sequences have been studied and used in clinical practice. These include both gradient-echo and FSE 3D acquisition sequences (Table 1). Gradient-Echo 3D Pulse Sequences Of the 3D gradient-echo pulse sequences, T1-weighted spoiled gradient-recalled echo (SPGR) (Fig. 3) and FLSH sequences have been the 3D volumetric acquisitions most commonly used, particularly for assessment of articular cartilage [10 15]. Potential disadvantages of these gradient-echo 3D imaging techniques include relatively long acquisition times and inherent sensitivity to intravoxel dephasing and susceptibility artifacts, which may be problematic in imaging of postoperative patients. These pulse sequences are typically obtained with fat suppression or water excitation to reduce chemical-shift artifact between water and fat at water-fat tissue interfaces and to increase the dynamic contrast range of the resultant images. water excitation based imaging technique, such as that commonly used with FLSH acquisitions, allows selective excitation of non fat-bound protons without the need for a spectral fatsuppression pulse and with the advantage of reducing inherent image acquisition times. Other 3D gradient-echo MRI techniques include dual-echo steady state (DESS), multiecho data image combination (MEDIC) [16 18] (Fig. 4), and steady-state free precession (SSFP) [19, 20], such as true fast imaging with steady-state precession (true FISP) [21 23] and vastly undersampled isotropic projection (VIPR)-SSFP [24]. These techniques yield images with high-signal-intensity joint fluid and associated arthrographic effects for detection of surface-based morphologic cartilage abnormalities in comparison with the characteristic lowsignal-intensity joint fluid on images obtained with SPGR pulse sequences. Reeder et al. [25] described an SSFP acquisition with multipoint fat-water separation MRI technique. The resultant fat-water separation with such imaging acquisitions is relatively immune to magnetic field inhomogeneities, and the imaging time is considerably shorter than with SPGR pulse sequences. However, potential disadvantages of SSFP pulse sequences are increased sensitivity to susceptibility artifacts and magic angle phenomena [26]. Despite these developments and modifications, gradient-echo imaging of musculoskeletal tissues displays image contrast characteristics different from those of the FSE pulse sequences commonly used in assessment of joints. This difference may limit their adoption in clinical practice as a viable replacement for standard 2D FSE pulse sequences. Three-Dimensional Fast Spin-Echo Pulse Sequences In an attempt to more closely match the image contrast characteristics of routinely used TLE 1: Three-Dimensional MRI Pulse Sequences Commonly Used in the Musculoskeletal System FSE pulse sequences, investigators have studied 3D FSE pulse sequences that entail parallel imaging, long echo trains, and large turbo factors to reduce 3D FSE imaging time [27, 28]. The similarities in contrast characteristics to more routinely used FSE sequences would theoretically make these pulse sequences a more attractive option than gradient-echo 3D pulse sequences. Such 3D FSE pulse sequences include sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) [29 31] (Figs. 1D 1F) and extended echo-train acquisition (XET) and FSE-Cube acquisition [32 36]. Image contrast weighting with such acquisition techniques can be adjusted according to the refocusing flip angles used to yield T1, intermediate, and T2 weighting with or without fat suppression [35]. The addition of fat suppression to XET or FSE-Cube imaging does not prolong the acquisition time [35]. Friedrich et al. [37] performed quantitative and qualitative assessment of musculoskeletal tissues with several 3D MRI sequences at 3 T, including true FISP, FLSH, and SPCE. They also investigated individually weighted DESS, which combined FISP images with reversed fast imaging with steady-state precession (PSIF) images. The signal-to-noise ratio (SNR) observed for cartilage was highest for SPCE followed by DESS, FLSH, and true FISP. With regard to the cartilage-to-fluid contrast-to-noise ratio (CNR), optimization of which is critical in the evaluation of articular cartilage, FLSH had a substantially lower CNR than DESS, true FISP, and SPCE. The authors also noted that SPCE and FLSH acquisitions were least sensitive to artifacts, true FISP being particularly susceptible to artifacts. In another investigation [35], cartilage had a high SNR on XET images, although Vendor bbreviation Sequence Fluid Signal Intensity GE Healthcare Siemens Healthcare Philips Healthcare Spoiled gradient echo Low SPGR FLSH T1 fast-field echo Coherent gradient echo High GRSS GRE Fast-field echo Steady-state free precession High SSFP PSIF T2 fast-field echo alanced steady-state free precession High FIEST, VIPR-SSFP True FISP alance fast-field echo Driven equilibrium High DEFT Dual-echo in steady state High DESS 3D fast spin echo Variable (dependent on refocusing flip angle) Cube, XET SPCE Note SPGR = spoiled gradient-recalled echo, GRSS = gradient-recalled acquisition in steady state, GRE = gradient-recalled echo, SSFP = steady-state free precession, PSIF = reverse fast imaging with steady-state free precession, FIEST = fast imaging employing steady state, VIPR = vastly undersampled isotropic projection, FISP = fast imaging with steady-state precession, DEFT = driven equilibrium Fourier transform, DESS = dual-echo in steady state, XET = extended echo-train acquisition, SPCE = sampling perfection with application-optimized contrast with different flip-angle evolutions. 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3 3D MRI of the Musculoskeletal System the cartilage-to-fluid CNR was lower than that observed with intermediate-weighted 2D FSE sequences. Three-Dimensional Pulse Sequences in ssessment of rticular Cartilage Three-Dimensional MRI in ssessment of Knee Cartilage Three-dimensional pulse sequences have been most extensively investigated in the assessment of the articular cartilage of the knee. Much of the early work in this area was concentrated on fat-suppressed 3D T1-weighted SPGR and FLSH sequences. Early studies showed the superior sensitivity of fat-suppressed 3D SPGR sequences for detection of articular cartilage defects (Fig. 3) of the knee (75 93%) in comparison with standard 2D sequences (29 53%) [11, 13, 38]. However, some of these studies were performed with a combination of spin-echo T2-weighted, T1- weighted, and gradient-echo sequences as part of the routine 2D evaluation of the knee, and these techniques have largely been abandoned in favor of FSE pulse sequences for evaluation of articular cartilage [11, 38, 39]. Comparing 3D water-excitation FLSH, which has an acquisition time of 5 minutes, and proton density fat-suppressed MRI of the knee, Mohr [40] found poorer sensitivity, accuracy, and negative and positive predictive values for the 3D FLSH sequence. disadvantage of SPGR and FLSH sequences is that the images show uniform high signal intensity throughout hyaline cartilage and therefore may not show intrasubstance cartilage lesions without articular surface morphologic changes and associated articular surface contour defects. Ruehm et al. [18] compared a 3D DESS acquisition with a 2D T2-weighted FSE sequence in assessment of the articular cartilage of the patella. They found that fewer partial-thickness cartilage lesions were depicted with the 3D DESS sequences. However, in many of these early studies, isotropic voxels were not used in the 3D imaging performed, which may have improved accuracy in the assessment of cartilage surface changes by minimizing volume-averaging effects of thicker-slice 2D or anisotropic 3D acquisitions. Kijowski et al. [41] evaluated, with arthroscopic correlation, a 5-minute 3D iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEL) SPGR sequence in addition to routine T2- and intermediate-weighted FSE sequences in imaging of the knees of 75 patients. They found that the addition of IDEL SPGR resulted in a significant increase in specificity for cartilage lesions and an increase in the proportion of cartilage lesions correctly graded in comparison with arthroscopy. They attributed these results to the decreased slice thickness of the 3D sequences, which allowed greater confidence for characterization of normal cartilage. s would be expected, there was no significant difference for larger full-thickness grade 3 lesions, because the thinner slice thickness would have no significant advantage for detection of larger lesions. In comparison with use of FSE sequences, use of IDEL SPGR exhibited a trend toward lower sensitivity for detection of grade 1 cartilage lesions, likely due to the magnetic transfer contrast and fluid-sensitive nature of the FSE sequences, enabling better detection of the increased intrasubstance water content in the abnormal articular cartilage. In the same study the IDEL gradientrecalled acquisition in steady state (GRSS) sequence was evaluated in another 75 patients, also with arthroscopic correlation, and was associated with greater improvement in diagnostic performance, particularly for superficial partial thickness defects. This finding was thought to be related to the higher contrast between cartilage and highsignal-intensity fluid on IDEL GRSS images as opposed to low-signal-intensity fluid observed on IDEL SPGR images [42]. Using a 3D water-excitation true FISP sequence with an acquisition time of 3 minutes at 1.5 T, Duc et al. [23] found the diagnostic performance for detection of chondral lesions of the knee was comparable to that of other pulse sequences, including intermediateweighted fat-suppressed and 3D water-excitation DESS and 3D fat-suppressed FLSH sequences. The authors found no diagnostic advantage of assessment of cartilage defects with thin-section true FISP in comparison with 2D intermediate-weighted fat-suppressed spin-echo or thick-section true FISP image sets. This result may be attributable to the benefits of increased SNR afforded by the thicker-section imaging datasets. In addition, use of fat-suppressed intermediate-weighted or fast STIR sequences may increase lesion conspicuity by better showing subchondral marrow abnormalities in comparison with the gradient-echo acquisitions. In a separate study [22], the same authors found comparable accuracy for detection of chondral lesions using isotropic ( mm) 3D water excitation true FISP in comparison with their routine imaging protocol. Kijowski et al. [26] evaluated VIPR-SSFP at 1.5 T in comparison with their routine triplanar FSE knee protocol for imaging of 95 patients. The imaging time for the VIPR-SS- FP pulse sequence was 5 minutes with a voxel size of mm. The VIPR- SSFP pulse sequence had an overall higher specificity but lower sensitivity for detection of cartilage defects. The authors postulated that the reduced sensitivity observed was due to the mixed T2- and T1-weighted contrast evident on VIPR-SSFP images and the absence of magnetization transfer contrast benefits in the characterization of cartilage abnormalities inherent to FSE acquisitions. In contrast, in comparison with imaging with routine 2D FSE sequences, use of 3D FSE-Cube at 3 T with an acquisition time of 5 minutes and voxel size of mm was associated with an increase in sensitivity and a decrease in specificity for detection of knee cartilage defects in 100 patients [33]. lthough the increased sensitivity of 3D FSE imaging is likely related to reduction of partial volume artifacts (Fig. 5), the decreased specificity was thought to be secondary to image blurring due to the use of markedly extended echo-train lengths with 3D FSE-Cube acquisitions. Ristow et al. [36], comparing 3D XET (voxel size, ; imaging time, 6 minutes) with their standard FSE pulse sequences at 3 T, had similar results: an increase in sensitivity and decreased specificity for cartilage lesions of the knee. The 2D images again had better image quality with reduced image blurring in comparison with the 3D acquired images. Three-Dimensional MRI in ssessment of Cartilage of Other Joints Studies of 3D MRI techniques in the evaluation of cartilage lesions of joints other than the knee have been limited. Imaging of the articular cartilage of the hip and ankle can be challenging owing to the general thinness of the articular cartilage in comparison with that of the knee [43] and the greater degree of curvature of the articular surfaces. In theory, the improved through-plane resolution and multiplanar reformats of 3D sequences may be advantageous for evaluation of articular cartilage of these joints. Comparing sagittal T1-weighted and sagittal 3D DESS sequences for MR arthrography on a 1.5-T system, Knuesel et al. [16] found one of the readers had decreased sensitivity and accuracy for chondral abnormalities in interpretation of 3D DESS images. The investigators also JR:199, September 2012 W285

4 Naraghi and White found overall lower interobserver reliability of 3D DESS imaging. They noted that subchondral changes, which may alert the observer to overlying chondral abnormalities, were better identified on T1-weighted images, and this may partly account for the better sensitivity of T1-weighted imaging. Lesion conspicuity was significantly improved with the 3D DESS sequence, however. Evaluating ankles of healthy volunteers at 3 T, Welsch et al. [44] found significantly increased measurements of cartilage thickness on isotropic (0.3 mm) 3D true FISP images, with an acquisition time of 10 minutes, than on proton density weighted fat-suppressed images. The techniques had similar reproducibility. To our knowledge, however, there have been no reports on the utility of this technique in evaluating chondral lesions. a-ssalamah et al. [45] compared a fat-suppressed 3D multishot echo-planar sequence and a 3D fat-suppressed spoiled gradientecho sequence for evaluation of ankle chondral defects. They found a lower CNR between cartilage and fluid for the echo-planar imaging sequence compared with the gradient-echo sequence, but they observed no significant differences between the two sequences in terms of image quality, artifacts, and lesion conspicuity. Global ssessment of Internal Derangement of Joints on 3D MR Images Three-Dimensional MRI ssessment of Internal Derangement of the Knee s with cartilage imaging, the utility of 3D MRI acquisitions for the overall evaluation of joints has been most commonly addressed in MRI of the knee (Figs. 6 and 7). Three-dimensional FSE sequences such as fat-suppressed 3D FSE-Cube and 3D- XET have been studied in imaging of the knee [33, 36] and have the potential advantage of providing intermediate-weighted contrast, which is the most commonly used contrast in routine clinical MRI of the knee. s in the imaging assessment of articular cartilage with FSE-Cube and XET acquisitions, blurring can be a problem with such sequences, particularly in assessment of menisci. In the detection of meniscal tears or ligamentous injuries, however, there were no significant differences between the FSE-based 3D images interpreted alone and those interpreted in combination with routine 2D FSE images [33, 36]. Decreasing echo-train length or increasing bandwidth can address the problem of geometric blurring, although these strategies have a penalty in terms of acquisition time and SNR. Investigators have noted [36] that low-contrast structures and lesions are better visualized on 2D FSE images and that there was significant improvement in detection of bone marrow edema on 2D FSE fat-suppressed pulse images in comparison with fat-suppressed 3D XET images. Jung et al. [46] compared 2D intermediate-weighted FSE pulse sequences in three planes with an isotropic 3D intermediate-weighted FSE pulse sequence with an acquisition time of 10 minutes and voxel size of mm in global assessment of the knee at 3 T. The 3D and 2D images were evaluated separately. The authors found no significant difference between the two techniques in evaluation of meniscal or ligamentous tears. However, fat suppression was not used as a component of any of the sequences studied, and articular cartilage was not assessed. Three-dimensional VIPR-SSFP has also been studied in the evaluation of meniscal and ligamentous injuries of the knee [26]. No significant difference in diagnostic accuracy for evaluation of tears of the medial meniscus and cruciate ligaments was observed when VIPR-SSFP images were interpreted alone and in combination with 2D FSE pulse sequences. However, assessment of 3D VIPR- SSFP imaging in isolation showed lower sensitivity and accuracy for lateral meniscal tears and a lower sensitivity for bone marrow edema, which may limit the utility of such 3D sequences in entirely replacing standard imaging sequences. Duc et al. [22] evaluated 3D true FISP images separately from their routine MRI protocol for imaging of the knee and found comparable results for evaluation of meniscal tears and tears of the anterior cruciate ligament. Interestingly, however, in that study bone marrow edema lesions were equally well depicted with both imaging protocols. Three-Dimensional MRI ssessment of Internal Derangement of Other Joints Three-dimensional imaging has been evaluated for MRI assessment of the shoulder. MR arthrography has been found to be a highly accurate technique in assessment of labroligamentous injuries [47, 48], and studies of the diagnostic utility of 3D MRI techniques have been principally assessed in the setting of MR arthrographic examination of the shoulder joint (Figs. 8 10). Jung et al. [46] evaluated 2D and 3D pulse sequences for 3-T MR arthrography of 100 patients who underwent subsequent arthroscopic surgery and found no significant differences in the assessment of superior labral anteroposterior lesions and anterior and posterior labral tears. Those authors used a 3D fast gradient-echo sequence with fat suppression with an isotropic voxel size of 0.6 mm and an image acquisition time of 5 minutes 30 seconds. Magee [49] similarly compared conventional 2D triplanar T1-weighted pulse sequences with isotropic (0.4 mm) fast spoiled gradient-echo fat-suppressed images of 100 patients undergoing MR arthrography. The imaging time for the 3D sequence was less than 3 minutes. Subsequent reference standard arthroscopic correlation was obtained for 67 patients. In that study, isotropic 3D images evaluated alone were not significantly different from conventional fat-suppressed T1-weighted images for identification of rotator cuff tears and labral tears. Lee et al. [50] also compared 3D fat-suppressed gradient-recalled echo imaging with standard T1- weighted fat-suppressed imaging for MR arthrography of 31 patients who subsequently underwent arthroscopy. They found an overall increased sensitivity for detection of labral tears using the 3D sequence, particularly for detection of posterior labral tears, with no significant differences observed in the detection of superior labral tears. Oh et al. [51] compared isotropic indirect MR arthrography performed with a fat-suppressed 3D fast gradient-echo technique with conventional MR arthrography of 36 patients performed with a 3-T system. They found no significant difference between the two techniques for detection of labral or rotator cuff lesions. The imaging time for the 3D sequence used in that investigation was less than 6 minutes. Reported experience with 3D techniques for global assessment of other joints is limited and consists mainly of assessment of technical features of acquisition sequences. Threedimensional gradient-echo pulse sequences have been used for a long time for assessment of the intrinsic ligaments of the wrist [52 59]. To our knowledge there have been no studies in which the diagnostic performance of 3D gradient-echo pulse sequences has been compared with that of 2D FSE pulse sequences. However, an analysis of the MRI literature showed an increase in accuracy in detection of full-thickness tears of the triangular fibrocartilage complex and the scapholunate and lunotriquetral ligaments with protocols that entail a high-resolution 3D gradient-echo pulse sequence in contrast to those using only 2D W286 JR:199, September 2012

5 3D MRI of the Musculoskeletal System FSE pulse sequences [60]. Many of these older studies were not performed with isotropic datasets. Three-dimensional sequences are advantageous for assessment of wrist ligaments given the small size of the ligamentous structures [61]. Saupe et al. [62] evaluated visualization of ligamentous structures at 1.5 T and 3 T using 2D FSE and 3D fast-field echo (FFE) pulse sequences. They found statistically significant improvement in the visibility of the triangular fibrocartilage complex and intrinsic ligaments at 3 T in comparison with 1.5 T when using 2D pulse sequences but not when using the 3D FFE pulse sequence. They attributed the lack of improvement of visualization of the ligamentous structures with 3D FFE at 3 T to increased susceptibility artifacts at the higher magnetic field strength. More recently Shahabpour et al. [63] found the normal extrinsic wrist ligaments using a 3D DESS pulse sequence at 1.5 T. Stevens et al. [64, 65] evaluated the 3D FSE-Cube sequence for imaging of the ankles and wrists of healthy volunteers at 3 T and 1.5 T. In the ankle, SNRs for cartilage and fluid were higher for FSE- Cube than for 2D FSE sequences, but fluidcartilage CNRs were similar for both sequences. s expected with this extended echo-train length FSE technique, blurring was significantly greater for FSE-Cube than for 2D FSE acquisitions. In the wrist, no significant differences in SNR were observed between the two acquisition techniques, and blurring was noted to vary according to the plane of acquisition in the 3D FSE-Cube sequence, being less pronounced on coronal acquisitions and more marked on axial acquisitions. Conclusion Technical advances in MRI hardware and pulse sequence development have made clinical 3D MRI of joints in a reasonable acquisition time a reality. Different pulse sequences have their own particular advantages and disadvantages and provide varying contrast between tissues. Of particular interest in applying 3D techniques to MRI of joint derangement is whether isotropic 3D imaging is sufficiently accurate to replace 2D FSE imaging and whether the time penalty of adding 3D sequences to the routine protocol is justified in the global assessment of joints. The literature to date supporting the use of 3D isotropic MRI as a viable replacement of standard 2D pulse sequences is at best limited. In our clinical practice, we have found that the use of a higher-strength magnetic field and multichannel coils results in a sufficiently better SNR to allow reduction in the number of signals averaged. Together with techniques such as parallel imaging, these adjustments allow a substantial reduction in imaging time for routine 2D protocols. These strategies allow the addition of a high-resolution isotropic ( mm) 3D pulse sequence, often performed in less than 5 minutes, without a significant overall time penalty. 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7 3D MRI of the Musculoskeletal System 1997; 79: nostic performance statistics. Clin Radiol 2001; 56: Yoshioka H, urns JE. Magnetic resonance imaging of triangular fibrocartilage. J Magn Reson Imaging 2012; 35: Saupe N, Prussmann KP, Luechinger R, osiger P, Marincek, Weishaupt D. MR imaging of the wrist: comparison between 1.5- and 3-T MR imaging preliminary experience. Radiology 2005; 234: Shahabpour M, De Maeseneer M, Pouders C, et al. MR imaging of normal extrinsic wrist ligaments using thin slices with clinical and surgical correlation. Eur J Radiol 2011; 77: Stevens KJ, usse RF, Han E, et al. nkle: isotropic MR imaging with 3D-FSE-cube initial experience in healthy volunteers. Radiology 2008; 249: Stevens KJ, Wallace CG, Chen W, Rosenberg JK, Gold GE. Imaging of the wrist at 1.5 Tesla using isotropic three-dimensional fast spin echo cube. J Magn Reson Imaging 2011; 33: Scheck RJ, Romagnolo, Hierner R, Pfluger T, Wilhelm K, Hahn K. The carpal ligaments in MR arthrography of the wrist: correlation with standard MRI and wrist arthroscopy. J Magn Reson Imaging 1999; 9: Maizlin ZV, rown J, Clement JJ, et al. MR arthrography of the wrist: controversies and concepts. Hand (N Y) 2009; 4: Hobby JL, Tom D, earcroft PW, Dixon K. Magnetic resonance imaging of the wrist: diag- Fig year-old man referred for MR imaging assessment of possible medial meniscal tear., Sagittal fast spin-echo T2-weighted MR image (TR/TE, 3200/40; echo-train length, 12; matrix, ; FOV, cm; slice thickness, 3.5 mm; slice gap, 0) through intercondylar aspect of medial femoral condyle obtained with 3-T MRI platform shows slight questionable irregularity of hyaline articular cartilage with small focal region of intracartilaginous fluid possibly reflective of small cartilage fissure with intrasubstance joint fluid (arrow)., Fat-suppressed 3D isotropic intermediateweighted sampling perfection with applicationoptimized contrast with different flip-angle evolutions (SPCE) MR image (TR/TE, 1200/47; matrix, ; voxel thickness, 0.6 mm) corresponding to clearly shows moderate-sized flap tear of delaminated articular cartilage with undermining by joint fluid (arrow) not evident in owing to volume effects. Fig year-old woman with prior knee injury and symptoms of possible derangement. and, Reformatted sagittal oblique () and coronal oblique () images obtained from postprocessing of fat-suppressed intermediate-weighted isotropic 3D sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) acquisition (imaging voxel dimensions, mm) along long axis of anterior cruciate ligament (CL) clearly illustrate distinct components of anteromedial (white arrow) and posterolateral (black arrow) bundles of normal CL. JR:199, September 2012 W289

8 Naraghi and White Fig year-old man with history of prior anterior cruciate ligament reconstruction 5 years earlier. and, Coronal 3D fat-suppressed T1-weighted spoiled gradient recalled-echo MR image (TR/TE, 44/4; matrix, ; slice thickness, 1.5 mm; FOV, cm) () and corresponding coronal intermediate-weighted fast spin-echo image (TR/TE, 4600/30; echo-train length, 7; matrix, ; FOV, cm; slice thickness, 4 mm; gap, 0) () show focal partial-thickness cartilage lesion along inner aspect of medial femoral condyle (arrow). Fig year-old man with history of ongoing volar wrist pain after injury 1 year earlier. and, Contiguous coronal fast spin-echo T2- weighted fat-suppressed MR images (TR/TE, 3660/77; echo-train length, 10; matrix, ; FOV, cm; slice thickness, 3.0 mm; interslice gap, 0.3 mm) through volar aspect of wrist show multilobulated ganglion cyst (arrow, ) originating from radial aspect of carpus. C E, Contiguous 3D multiecho data image combination images (TR/TE, 32/17; echo-train length, 3; matrix, ; FOV, cm; voxel thickness, 0.4 mm) corresponding to and clearly show ganglion cyst originates from and dissects through fibers of extrinsic radiocapitate ligament along palmar aspect of carpus (arrow). C D E W290 JR:199, September 2012

9 3D MRI of the Musculoskeletal System Fig year-old boy with right knee pain. and, Sagittal fat-suppressed intermediateweighted isotropic 3D sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) acquisition (TR/TE, 1200/22; echo-train length, 32; voxel dimensions, mm; matrix, ; FOV, cm) () and corresponding sagittal fat-suppressed fast spinecho T2-weighted image (TR/TE, 3100/54; echo-train length, 6; matrix, ; FOV, cm; slice thickness, 3.5 mm; interslice gap, 0.3 mm) () show evidence of osteochondritis desiccans of lateral femoral trochlea (arrows). Osteochondral lesion interface with underlying bone and adjacent cartilage is clearer in, likely owing to thin slice thickness and lack of volume average effects likely responsible for ill definition of lesion in. C Fig year-old woman with history of remote injury and reconstruction of anterior cruciate ligament presenting with symptoms of anterior knee pain., xial fast spin-echo fat-suppressed intermediate-weighted MR image (TR/TE, 2800/40; echo-train length, 5; matrix, ; FOV, cm; slice thickness, 3.5 mm; slice gap, 0) through femoral trochlea shows central focal osseous hypertrophy in lower femoral trochlear sulcus (arrow) and suspected overlying cartilage loss, which is ill-defined owing to volume averaging of true axial slice through oblique surface of trochlea., Radial oblique reformatted image perpendicular to trochlear articular surface clearly shows central defect of articular cartilage (arrowheads) with associated central button osteophyte (arrow). C, Radial reformatted image obtained from axial 3D isotropic fat-suppressed intermediate-weighted sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) MR image (TR/TE, 1200/25; matrix, ; voxel thickness, 0.6 mm). Line indicated by arrow is orientation of. JR:199, September 2012 W291

10 Naraghi and White Fig year-old man with symptoms of lateral knee pain referred for MR evaluation of possible medial meniscal tear., Coronal intermediate-weighted fast spin-echo MR image (TR/TE, 4600/30; echo-train length, 7; matrix, ; FOV, cm; slice thickness, 4 mm; gap, 0) shows focal cartilage signal abnormality along lateral tibial articular surface (arrow) and corresponding flap tear of cartilage on corresponding surface of lateral femoral condyle (arrowhead)., Coronal oblique reformat obtained from axial 3D isotropic fat-suppressed intermediate-weighted sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) acquisition (TR/TE, 1200/25; matrix, ; voxel thickness, 0.6 mm) nicely depicts cartilage lesions (arrow and arrowhead) with improved resolution of defect margins due to thin slice thickness (0.6 mm) of reformatted dataset. Fig year-old man with history of recurrent left shoulder instability. and, xial T1-weighted fat-suppressed isotropic 3D sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) MR image (TR/TE, 550/11; echo-train length, 22; voxel dimensions, mm; matrix, ; FOV, 16 cm) () and corresponding axial fat-suppressed fast spin-echo T1-weighted image (TR/TE, 520/10; echo-train length, 4; matrix, ; FOV, cm; slice thickness, 4 mm; slice gap, 0) () through inferior glenoid and inferior glenoid labrum acquired as part of MR arthrographic study of shoulder. SPCE image () shows clearly defined cleft and fissure of inferior glenoid labrum (arrow) that is not depicted in, likely owing to volume averaging effects. No cleft was seen on adjacent slices on 2D FSE images. Fig year-old man with history of acute onset shoulder pain after weightlifting injury., Coronal T1-weighted fat-suppressed fast spinecho MR image (TR/TE, 685/9; echo-train length, 3; matrix, ; FOV, cm; slice thickness, 4 mm; gap, 0) obtained as part of MR arthrogram of right shoulder shows superior labral anteroposterior (SLP) tear extending through biceps anchor (arrow)., Coronal oblique reformatted image obtained from axial 3D isotropic fat-suppressed sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) acquisition dataset (TR/TE, 1200/25; matrix, ; voxel thickness, 0.6 mm) corresponding to similarly depicts SLP tear (arrow). ssociated tear of anterior inferior labrum (arrowhead) is evident. W292 JR:199, September 2012

11 3D MRI of the Musculoskeletal System Fig year-old woman with history of anterior shoulder instability., Sagittal intermediate-weighted fast spin-echo MR image (TR/TE, 2000/34; echo-train length, 5; matrix, ; FOV, cm; slice thickness, 4 mm; gap, 0) shows ankart lesion (arrow) with slight blunting of anterior inferior osseous glenoid (arrowheads)., Reformatted sagittal oblique image obtained from axial 3D isotropic fat-suppressed T1-weighted sampling perfection with application-optimized contrast with different flip-angle evolutions (SPCE) acquisition dataset (TR/TE, 1200/25; matrix, ; voxel thickness, 0.6 mm) corresponding to similarly clearly depicts fibrocartilaginous (arrow) and osseous ankart lesions. rrowheads indicate anterior inferior osseous glenoid. JR:199, September 2012 W293