磁共振WATS技术在颞下颌关节三维有限元建模中的应用价值

目的　探讨磁共振WATS技术在颞下颌关节三维有限元建模中的应用价值。方法　利用超薄层磁共振T1W 3DWATS成像技术对模型进行数据采样 ,采用Matlab大型科学计算软件及Ansys三维有限元专用软件建立颞下颌关节模型。结果　建立出的模型形态理想 ,髁突、关节盘及关节结节等与活体解剖TMJ具有良好的相似性 ,尤其对关节盘的位置形态模拟较精确。结论　磁共振WATS技术在显示关节软骨上有独特优势 ,利用该成像技术建立TMJ三维有限元模型比以往其它成像技术更精确 ,为进行TMJ生物力学分析奠定了良好基础     

颞下颌关节滑膜软骨瘤病的MRI表现

目的:探讨和描述颞下颌关节(TMJ)滑膜软骨瘤病的MRI表现特点。材料和方法:回顾性观察和分析13例经手术病理证实的TMJ区滑膜软骨瘤病的MRI表现。所有病例均在术前行闭口矢状面和冠状面PDWI、开口矢状面T_2WI检查。结果:所有滑膜软骨瘤病均发生于TMJ上腔。病变的MRI表现:关节上腔异常积液(13例,100%);关节囊明显扩张(11例,84.6%);关节腔内有多发软骨样小体的形成(11例,84.6%);关节囊或滑膜组织增厚(8例,61.5%)和颞骨关节面骨质破坏(4例,30.8%)。MRI未显示病变有下颌髁突侵蚀、关节囊外软组织侵犯、大脑颞叶脑膜和脑实质侵犯。结论:颞下颌关节滑膜软骨瘤病的MRI表现具有一定特点,主要表现为关节上腔异常积液,伴关节囊扩张、多发软骨样结节小体形成和滑膜组织增厚。     

下颌髁突脱位骨折后颞下颌关节软组织改变的MRI表现

目的 分析下颌髁突脱位骨折后颞下颌关节(TMJ)软组织改变的MRI表现.方法 应用矢状面和冠状面质子密度加权成像(PDWI)和T2WI连续检查103侧(77例)患有下颌髁突脱位骨折的颞下颌关节(TMJ).结果 MRI上,103侧髁突脱位骨折后的TMJ异常表现有:(1)髁突骨折断片向前下(102侧,99.0%)和前(1侧,10%)脱位;(2)关节盘移位(100侧,97.1%),其中矢状面MRI显示关节盘随脱位的髁突向前下移位者99侧,向前移位者1侧;(3)关节腔积液(103侧,100%);(4)关节盘后区信号异常(91侧,88.3%);(5)关节盘下后附着异常(89侧,86.4%);(6)关节囊异常(89侧,86.4%);(7)关节盘上后附着异常(37侧,35.9%);(8)关节盘变形(8侧,7.8%);(9)关节盘撕裂(8侧,7.8%);(10)颞骨关节窝骨折(4侧,3.9%).结论矢状面MRI上,多数下颌髁突脱位骨折以TMJ关节盘随脱位的髁突向前下移位,并伴有关节腔积液为特点.     

Temporomandibular joint and 3.0 T pseudodynamic magnetic resonance imaging. Part 1: evaluation of condylar and disc dysfunction

Objectives

This study describes an improved method for examining and diagnosing temporomandibular joint (TMJ) dynamics by 3.0 T pseudodynamic MRI.

Methods

Clinical observation and conventional static MRI of volunteers (one without and eight with TMJ arthrosis) were followed by 3.0 T pseudodynamic MRI in positions ranging from the mouth closed to mouth fully opened. Condylar head (Cd), articular disc anterior border (Da) and articular disc posterior border (Dp) were digitized on sagittal images to determine trajectory and velocity patterns.

Results

Patients were divided into three groups based on the presence or absence of dysfunction: Group 1, no dysfunction on the right or left side of the TMJ; Group 2, dysfunction on the right or left side of the TMJ; and Group 3, dysfunction on both the right and left sides of the TMJs. In 75% of patients (12 of 16 joints), pseudodynamic TMJ analysis was useful for determining a functional abnormality. Using a points system based on three trajectory and seven velocity patterns, discs with adhesion and perforation had significantly fewer points than discs with anterior displacement (with and without reduction) and discs with no abnormality (P = 0.019 < 0.05).

Conclusions

Trajectory and velocity patterns based on 3.0 T pseudodynamic MRI identified the affected side and determined the extent of morbidity in the Cd as well as the Da and Dp. The typical abnormal movement pattern of discs with anterior displacement (with and without reduction) and pathological structural changes of the articular disc (such as adhesion and perforation) could be identified.     

MRI evaluation of morpho-structural alterations of the retrodiscal tissue in condylo-meniscal incoordination of the TMJ: usefulness of individualised T2-weighted TSE sequences

PURPOSE: To assess and evaluate morpho-structural alterations of the retrodiscal tissue of the temporomandibular joint (TMJ) that may be seen in chronic trauma of the condylo-meniscal incoordination through magnetic resonance (MR), using T2-weighted TSE sequences. MATERIALS AND METHODS: The study included 40 patients, 6 male and 34 female, age range 12-66 years, mean age 28.5 years. According to the Wilkes classification, TMJs of patients were graded as follows: 10 grade 1 TMJs; 28 grade 2, 16 grade 3, and 26 grade 4. Scans were obtained with a 1.5 T MRI unit, and a dedicated surface coil, using T2-weighted TSE sequences (TR 3000-3500, TE 90-100), 2 acquisitions, 256x256 matrix, 3-mm section thickness, with a 0-mm interval, and 2'30" duration for a single acquisition. Scans were obtained both during opening and during closure of the mouth, on 3 planes: sagittal oblique, perpendicular to the condylar long axis; coronal oblique, perpendicular to the anteroposterior axis of the discs; and axial, perpendicular to coronal scans. Parameters used were the following: presence or absence of retrodiscal fibrosis; morphology of the retrodiscal fibrosis in scans taken during mouth opening in the four grades of the Wilkes classification; dimensions of the retrodiscal fibrosis in scans taken during mouth opening, in the four grades of the Wilkes classification, in an anteroposterior direction, measuring the longest distance on parasagittal planes on a horizontal line touching the outer edge of the disc and the most-distal point of fibrosis, and in a vertical direction, measuring the distance between the highest and lowest points of fibrosis; signal intensity features within the fibrotic area. RESULTS: In all TMJs analysed, it was possible to confirm the presence of retrodiscal tissue fibrosis, which was more or less evident according to the grading of the dysfunction/disease, to the extent of mouth opening, and to displacement with or without reduction of the articular disc. In grade 1 TMJs, fibrosis looked like a truncated cone; in grade 2, fibrosis looked like a cone; in grade 3, it was either shaped like a mushroom placed horizontally, with the stalk towards the disc, or else ribbon-shaped; in grade 4, it had an inhomogeneous, irregular ribbon shape. CONCLUSIONS: MR studies of TMJ dysfunction through T2-weighted TSE sequences allowed us to evidence in all cases the sclerotic alterations of the retrodiscal tissue, and to assess their form and dimensions. Furthermore, it was possible to evidence both the pathognomonic features of retrodiscal tissue fibrosis resembling a mushroom, and the characteristic brace-shape the upper and lower layers take on during mouth opening in TMJs with a disc displacement with reduction.     

Temporomandibular joint and 3.0 T pseudodynamic magnetic resonance imaging. Part 2: evaluation of articular disc obscurity

Objectives

This study examined the relationship between temporomandibular joint (TMJ) dysfunctions and obscurity grades of interpreted anterior and posterior borders of the articular disc (Da and Dp, respectively) by 3.0 T pseudodynamic MRI.

Methods

Da and Dp were classified into seven obscurity grades, and the Dp contour was classified into three types. The grades, types and TMJ function were compared by 3.0 T pseudodynamic MRI.

Results

Unobscured Da images at condylar positions posterior to the articular eminence were associated with normal TMJ function (P = 0.046 < 0.05). Unobscured Dp images at condylar positions anterior to the articular eminence were associated with normal TMJ function (P = 0.033 < 0.05). In addition, unobscured Dp images following flap insertion were associated with normal TMJ function (P = 0.043 < 0.05). There was no statistical relationship between Dp contour types and TMJ movement, but any change observed in the Dp contour during mouth opening was associated with abnormal TMJ function (P = 0.040 < 0.05).

Conclusions

Grading of Da and Dp obscurity based on how well the areas were defined in the images, identifying the condylar positions in relation to the glenoid fossa and articular eminences, and observing the changes in Dp contour types were useful for diagnosing TMJ abnormalities.     

Is the morphology of the articular eminence of the temporomandibular joint a predisposing factor for disc displacement?

OBJECTIVES: To test the hypothesis that the morphology of the articular eminence of the TMJ is a predisposing factor for disc displacement. METHODS: MR images of 220 TM joints in 151 patients were studied: 47 joints had no disk displacement (NDD), 81 joints disc displacement with reduction (DDWR) and 92 joints disc displacement without reduction (DDWOR). The shape of the articular eminence of the TMJ was classified into four types, box, sigmoid, flattened and deformed. The prevalence of the box and flattened forms in the three groups of joints was compared. RESULTS: There was no statistically significant difference in the prevalence of the box form between the joints with NDD, DDWR, and DDWOR. On the other hand, the prevalence of the flattened-type was statistically lower in the joints with DDWR (goodness test of fit for chi 2, P < 0.05). CONCLUSIONS: It appears that disc displacement is less likely to be found in joints with a shallow articular eminence.     

An optimized fast protocol for magnetic resonance imaging of the temporomandibular joint

OBJECTIVES: To provide a fast protocol for MR imaging of the TMJ with high contrast resolution of both soft tissue and joint fluid. METHODS: A fast turbo-spin echo (TSE) pulse sequence was developed. The new technique was compared with T1W conventional spin echo (CSE) and T2W TSE sequences in imaging 57 TMJs in 50 patients. Disc location and contour and bone delineation were assessed on three images of each TMJ by one observer. Presence and location of intra-articular fluid were evaluated on both standard T2W and new TSE images. Image quality was scored on a 3 point-scale by one observer. RESULTS: The net image acquisition time for one plane was 2 min with the new TSE sequence compared with approximately 5-10 min for T1W and 4 min for T2W. The new sequence provided equivalent diagnostic information to a combination of T1W CSE for disc position and contour and bone contour and T2W TSE sequence for joint fluid. CONCLUSIONS: The examination time for MRI of the TMJ can be considerably reduced with the new fast TSE pulse sequence without compromising image quality.     

Development of contrast-enhanced virtual MR cholangioscopy: a feasibility study

The purpose of this study was to examine the feasibility of contrast-enhanced virtual MR cholangioscopy (CE VMRC). Intraluminal views of the extrahepatic biliary tree were generated in ten patients undergoing abdominal MRI post mangafodipir trisodium administration employing coronal 2.5-mm 3D fast low-angle shot (FLASH) images (TR 6.8 ms, TE 2.3 ms, matrix 195 x 512) with fat saturation and a commercially available software. Contrast-enhanced VMRC was compared with single-shot turbo spin-echo T2-weighted MR cholangiography (T2 MRC) in terms of ductal visualization and artifact presence, utilizing a five-point grading scale. Four anatomic segments were evaluated: the intra- and extra-pancreatic segment of the common bile duct (CBD), and the cystic duct and the area of hepatic duct bifurcation. Both CE VMRC and T2 MRC depicted 38 of 40 segments. There were no significant differences between CE VMRC and T2 MRC in ranking ductal segments visualization ( p=0.27). The high contrast between intraluminal fluid and extraluminal tissues facilitated the generation of endoscopic views. Contrast-enhanced virtual MR cholangioscopy is a feasible technique providing endoscopic views of the CBD. Initial results show correlation of CE VMRC with projectional MR cholangiography.     

Optimizing MR signal contrast of the temporomandibular joint disk

Purpose:

To use a tissue specific algorithm to numerically optimize UTE sequence parameters to maximize contrast within temporomandibular joint (TMJ) donor tissue.

Materials and Methods:

A TMJ specimen tissue block was sectioned in a true sagittal plane and imaged at 3 Tesla (T) using UTE pulse sequences with dual echo subtraction. The MR tissue properties (PD, T₂, T₂*, and T₁) were measured and subsequently used to calculate the optimum sequences parameters (repetition time [TR], echo time [TE], and θ).

Results:

It was found that the main contrast available in the TMJ could be obtained from T₂ (or T₂*) contrast. With the first echo time fixed at 8 μs and using TR = 200 ms, the optimum parameters were found to be: θ ≈ 60°, and TE2 ≈ 15 ms, when the second echo is acquired using a gradient echo and θ ≈ 120°, and TE2 ≈ 15 ms, when the second echo is acquired using a spin echo.

Conclusion:

Our results show that MR signal contrast can be optimized between tissues in a systematic manner. The MR contrast within the TMJ was successfully optimized with facile delineation between disc and soft tissues. J. Magn. Reson. Imaging 2011;. © 2011 Wiley Periodicals, Inc.     

Three-dimensional segmentation of MR images of the head using probability and connectivity

We describe a three-dimensional (3D) segmentation method that comprises (a) user interactive identification of tissue classes; (b) calculation of a probability distribution for each tissue; (c) creation of a feature map of the most probable tissues; (d) 3D segmentation of the magnetic resonance (MR) data; (e) smoothing of the segmented data; (f) extraction of surfaces of interest with connectivity; (g) generation of surfaces; and (h) rendering of multiple surfaces to plan surgery. Patients with normal head anatomy and with abnormalities such as multiple sclerosis lesions and brain tumors were scanned with a 1.5 T MR system using a two echo contiguous (interleaved), multislice pulse sequence that provides both proton density and T2-weighted contrast. After the user identified the tissues, the 3D data were automatically segmented into background, facial tissue, brain matter, CSF, and lesions. Surfaces of the face, brain, lateral ventricles, tumors, and multiple sclerosis lesions are displayed using color coding and gradient shading. Color improves the visualization of segmented tissues, while gradient shading enhances the perception of depth. Manipulation of the 3D model on a workstation aids surgical planning. Sulci and gyri stand out, thus aiding functional mapping of the brain surface.     

MR imaging of the temporomandibular joint: a validation experiment in vitro

RATIONALE AND OBJECTIVES: The authors compared magnetic resonance (MR) image quality obtained from 3- and 1-mm-thick sections in the depiction of the temporomandibular joint (TMJ) and its adjacent structures. MATERIALS AND METHODS: Eight TMJ specimens from four adult cadaver heads were depicted with MR imaging. Both 3- and 1-mm-thick sections were generated. One oral and maxillofacial radiologist, who was blinded to section thickness, evaluated the anatomic details of the images. Subsequently, the joints were surgically explored by two oral and maxillofacial surgeons, and the physical findings were recorded. RESULTS: Some statistically significant differences were found between the physical findings and the 3-mm-thick section images, while no significant differences were found with the 1-mm-thick sections. CONCLUSION: The TMJ and its adjacent structures were better depicted by thinner MR images.     

MRI of the inner ear: comparison of axial T2-weighted, three-dimensional turbo spin-echo images, maximum-intensity projections, and volume rendering

RATIONALE AND OBJECTIVES: To compare the ability of axial T2-weighted, three-dimensional, turbo spin-echo (3D TSE) images, targeted maximum-intensity projections (MIPs), and 3D volume reconstructions to depict anatomic details of the labyrinth. METHODS: In 24 volunteers, 3D TSE images were obtained. MIPs and 3D volume reconstructions were performed from the acquired data. All images were evaluated by three radiologists independently regarding the visualization of the different anatomic structures. RESULTS: In the axial slices, most anatomic details were visible in comparison with observations by the other modalities. The 2.5 windings of the cochlea were best depicted on the MIPs. Volume reconstructions rendered excellent spatial information regarding the vestibule and semicircular canals and were the only technique that demonstrated all three ampullae in all cases. CONCLUSIONS: Axial TSE images, MIPs, and 3D volume reconstructions are complementary modalities that provide different information. Our results suggest that improved diagnostic information can be obtained by applying these volume visualization reconstruction techniques.     

Preoperative 3T MR imaging of rectal cancer: local staging accuracy using a two-dimensional and three-dimensional T2-weighted turbo spin echo sequence

PURPOSE: The purpose of our study was to evaluate the image quality and diagnostic performance of two-dimensional (D) turbo spin echo (TSE) and 3D T2-weighted TSE MR imaging in local staging of rectal cancer at 3T. MATERIALS AND METHODS: 3T phased-array MR imaging was performed in 36 consecutive patients with biopsy-proven rectal cancer. High-resolution 2D TSE images in three planes and 3D TSE images of the rectum were obtained. Two independent observers performed an image quality assessment using eight image quality characteristics. All 2D and 3D datasets were evaluated separately. MR images were prospectively evaluated by two experienced radiologists in consensus with regard to local disease. Total mesorectal excision was used as the standard of reference. The sensitivity, specificity, positive and negative predictive value, and overall accuracy were calculated. Areas under the receiver operating characteristic (ROC) curve (AUC) were determined. RESULTS: Twenty-two patients who underwent a total mesorectal excision were enrolled in this study. Significantly more motion artifacts were present with 3D TSE imaging (P=0.04). The overall sensitivity, specificity, and accuracy of muscularis propria invasion in rectal cancer using 2D T2-weighted images were 100%, 66%, and 95%, respectively. There was a statistical significant greater AUC using 2D T2-weighted images compared to 3D T2-weighted MR images (P=0.04). The ROC curves describing the results of the interpretation of 2D and 3D T2-weighted datasets regarding perirectal tissue invasion showed no statistical significant difference (P=0.41). CONCLUSIONS: In this study, high local staging accuracies with 3T 2D T2-weighted MR imaging were demonstrated. 3D T2-weighted MR imaging cannot replace 2D MR imaging for local staging of rectal cancer. However, 3D MR imaging can be used for visualization of the complex pelvic anatomy for treatment planning purposes.     

Cortical lesions in multiple sclerosis: combined postmortem MR imaging and histopathology

BACKGROUND AND PURPOSE: Cortical lesions constitute a substantial part of the total lesion load in multiple sclerosis (MS) brain. They have been related to neuropsychological deficits, epilepsy, and depression. However, the proportion of purely cortical lesions visible on MR images is unknown. The aim of this study was to determine the proportion of intracortical and mixed gray matter (GM)-white matter (WM) lesions that can be visualized with postmortem MR imaging. METHODS: We studied 49 brain samples from nine cases of chronic MS. Tissue sections were matched to dual-echo T2-weighted spin-echo (T2SE) MR images. MS lesions were identified by means of myelin basic protein immunostaining, and lesions were classified as intracortical, mixed GM-WM, deep GM, or WM. Investigators blinded to the histopathologic results scored postmortem T2SE and 3D fluid-attenuated inversion recovery (FLAIR) images. RESULTS: Immunohistochemistry confirmed 70 WM, eight deep GM, 27 mixed GM-WM, and 63 purely cortical lesions. T2SE images depicted only 3% of the intracortical lesions, and 3D FLAIR imaging showed 5%. Mixed GM-WM lesions were most frequently detectable on T2SE and 3D FLAIR images (22% and 41%, respectively). T2SE imaging showed 13% of deep GM lesions versus 38% on 3D FLAIR. T2SE images depicted 63% of the WM lesions, whereas 3D FLAIR images depicted 71%. Even after side-by-side review of the MR imaging and histopathologic results, many of the intracortical lesions could not be identified retrospectively. CONCLUSION: In contrast to WM lesions and mixed GM-WM lesions, intracortical lesions remain largely undetected with current MR imaging resolution.     

Patellar articular cartilage lesions: in vitro MR imaging evaluation after placement in gadopentetate dimeglumine solution

PURPOSE: To evaluate T1-weighted magnetic resonance (MR) imaging after diffusion of gadopentetate dimeglumine for visualization of articular cartilage lesions. MATERIALS AND METHODS: MR imaging was performed in eight human cadaveric patella specimens immediately and 4 hours after placement into a vessel filled with gadopentetate dimeglumine solution (2.5 mmol/L). T1-weighted spin-echo and inversion-recovery turbo spin-echo MR sequences with nulled cartilage signal (inversion time of 300 msec) were used. In a total of 128 articular cartilage areas, MR imaging findings were compared with macroscopic and histopathologic findings. Pathologic evaluation was performed by one musculoskeletal pathologist. With knowledge of pathologic observations, MR images were analyzed by one musculoskeletal radiologist with regard to intrinsic signal intensity characteristics and surface abnormalities of articular cartilage. RESULTS: Histopathologic findings demonstrated 67 areas of normal articular cartilage and 66 cartilage lesions (grade 1, n = 19; grade 2, n = 15; grade 3, n = 26; grade 4, n = 6). All grade 3 and 4 lesions could be identified on MR images obtained immediately after submersion and after 4 hours. Ninety-four percent of grade 1 and 2 lesions were identified as areas of predominantly decreased contrast enhancement on delayed MR images obtained with both sequences. MR images obtained immediately after submersion demonstrated abnormal signal intensity in only 9% and 12% of grade 1 and 2 lesions, respectively. CONCLUSION: T1-weighted MR images obtained in vitro after gadopentetate dimeglumine diffusion allow demonstration of articular cartilage surface lesions and early stages of cartilage degradation.     

Quantification of white matter and gray matter volumes from three-dimensional magnetic resonance volume studies using fuzzy classifiers

We accurately measured white matter (WM) and gray matter (GM) from three-dimensional (3D) volume studies, using a fuzzy classification technique. The new segmentation method is a modification of a recently published method developed for T1 parametric images. 3D MR images were transformed into pseudo forms of T1 parametric images and segmented into WM and GM voxel fraction images with a set of standardized fuzzy classifiers. This segmentation method was validated with synthesized 3D MR images as phantoms. These phantoms were developed from cryosectioned human brain images located in the superior, middle, and inferior regions of the cerebrum. Phantom volume measurements revealed that, generally, the difference between measured and actual volumes was less than 3% for 1.5-mm simulated brain slices. The average cerebral GM/WM ratio calculated from 3D MR studies in four subjects was 1.77, which compared favorably with the estimate of 1.67 derived from anatomical data. Results indicate that this is an accurate and rapid method for quantifying WM and GM from T1-weighted 3D volume studies.     

MR imaging in carotid artery atherosclerosis plaque characterization.

AIM: To evaluate the potential role of carotid artery atherosclerosis plaque magnetic resonance (MR) microimaging as magnetic resonance imaging (MRI) marker, ex vivo MR images were acquired at optimized parameters on 9.4T Bruker animal imager for occluded tissue resected by carotid endarterectomy (CEA) and corresponding histopathological analysis was made. METHODS AND MATERIALS: For imaging, CEA tissues of size 2-6 cm long and 0.5-1.5 cm wide, were transferred to 15 ml co-polymer laboratory culture tubes containing either 10% formalin in phosphate buffered saline (PBS) or in 50% glycerol in PBS. Imaging protocol was set at TE=30 ms, TR=1.5 s, matrix size=265 x 512, NEX=128, slice thickness=1 mm and in-plane resolution=0.1 mm for total sample size 2.5 cm. Soon after imaging done, carotid artery tissues were cut into 5-mm segments and processed for histological section for successive 5-micrometer slices. To compare morphology of 5 mum thin CEA section with that of 1 mm MR slices, registration was obtained between histologic sections and MR slices. Contrast and magnetic resonance relaxation characteristics were analyzed. RESULTS: Total carotid artery area computed by MR imaging was correlated with areas determined from histologic sections (r(2)=0.989, p=0.0001). For the lumen area, the correlation between MR images and histologic area was (r(2)=0.942, p=0.0001). Relaxation times and T(2) parametric images of different plaque components were determinant for contrast resolution. Scan parameters were optimized for fibrous cap and atheroma. Scan parameters were characteristic for comparison at 1.5T and 9.4T MR imagers. CONCLUSION: The observed correlation validated MR microimaging to assess morphological features of carotid artery plaques and contrast resolution highlighted the potential of in vivo MR imaging as non-invasive MRI marker to monitor carotid artery plaque morphometry and plaque composition.     

Web-based calibration of observers using MRI of the temporomandibular joint

Objectives

Research diagnostic criteria for temporomandibular disorders (RDC/TMDs) were proposed in 1992 with the aim of standardizing and testing methods for diagnosing TMDs. RDC/TMDs have so far been lacking standardized methods for imaging and criteria for imaging diagnosis of disorders of the temporomandibular joint (TMJ). Criteria for disorders of the TMJ have recently been proposed for MRI. The aim of this study was to publish MR images of the TMJ on the web and to test the agreement of five observers using the criteria.

Methods

20 cases of MRI of the TMJ were published on the web together with the criteria. The MR images were taken in closed and open mouth positions, and sagittal and coronal views. Five observers diagnosed disc position, disc shape, joint effusion and loose calcified bodies in the TMJ.

Results

In all cases except one, three or more observers agreed upon the diagnosis. All agreed on whether a loose calcified body was present or not. The second best agreement was obtained for disc position in the sagittal view, where all observers agreed in 16 of the 20 cases. For disc position in the coronal view and the evaluation of the disc shape, observer agreement was lower.

Conclusion

Criteria were useful in order to standardize and simplify evaluation and thereby probably increase the diagnostic outcome among different observers for MRI of the TMJ. We recommend that the criteria be used internationally to facilitate comparisons between different studies.     

Dermal grafts of the temporomandibular joint: postoperative appearance on MR images

Complications may follow meniscectomy and placement of an allogenic implant in temporomandibular joint (TMJ) dysfunction. To characterize the anatomy of autogenous dermal grafts for repair and repositioning of the meniscus, the authors performed T1-weighted magnetic resonance (MR) imaging of 20 TMJs in 10 patients 6-23 months after surgery that was considered successful. MR imaging did not enable detection of the dermal grafts. Comparison of preoperative and postoperative MR images revealed little, if any, change in meniscal position. MR images of 20 menisci revealed anterior displacement (n = 11), normal position (n = 4), focal areas of increased signal intensity (n = 4), fragmentation (n = 2), and suboptimal visualization (n = 5). MR images of 20 condyles revealed normal features (n = 11), erosions (n = 2), early avascular necrosis (AVN) or subchondral cysts (n = 2), AVN (n = 3), an osteophyte (n = 1), and loss of bone (n = 2). One TMJ demonstrated increased soft tissue in the bilaminar zone.