Coronal Directions Research Articles

PubAnatomy 3D: Integrating Medline Exploration with the Allen Mouse Brain Atlas

PubAnatomy 3D: Integrating Medline Exploration with the Allen Mouse Brain Atlas

Evaluation of Interpolation Effects on Upsampling and Accuracy of Cost Functions-Based Optimized Automatic Image Registration

Interpolation has become a default operation in image processing and medical imaging and is one of the important factors in the success of an intensity-based registration method. Interpolation is needed if the fractional unit of motion is not matched and located on the high resolution (HR) grid. The purpose of this work is to present a systematic evaluation of eight standard interpolation techniques (trilinear, nearest neighbor, cubic Lagrangian, quintic Lagrangian, hepatic Lagrangian, windowed Sinc, B-spline 3rd order, and B-spline 4th order) and to compare the effect of cost functions (least squares (LS), normalized mutual information (NMI), normalized cross correlation (NCC), and correlation ratio (CR)) for optimized automatic image registration (OAIR) on 3D spoiled gradient recalled (SPGR) magnetic resonance images (MRI) of the brain acquired using a 3T GE MR scanner. Subsampling was performed in the axial, sagittal, and coronal directions to emulate three low resolution datasets. Afterwards, the low resolution datasets were upsampled using different interpolation methods, and they were then compared to the high resolution data. The mean squared error, peak signal to noise, joint entropy, and cost functions were computed for quantitative assessment of the method. Magnetic resonance image scans and joint histogram were used for qualitative assessment of the method.

A framework for modeling ocular drug transport and flow through the eye using micro-CT

This study uses micro-computed tomography (micro-CT) imaging for assessment of concentration and transport mechanisms of ocular drug surrogates following intravitreal injection. Injections of an iodinated contrast agent were administered to enucleated porcine eyes prior to scanning over 192 min. Image analysis was performed using signal profiles and regions of interest that corresponded to specific iodine concentrations. Diffusion coefficients of the injected iodine solutions were calculated using nonlinear regression analysis with a diffusion model. There was a predominantly diffusive component in the movement of the contrast to the back of the eye in the horizontal (sagittal & coronal) directions, with ultimate retinal fate observed after 120 min. The diffusion coefficients were found to have a mean of 4.87 × 10−4 mm2 s−1 and standard deviation of 8.39 × 10−5 mm2 s−1 for 150 mg ml−1 iodine concentration and 6.13 × 10−4 ± 1.83 × 10−4 mm2 s−1 for 37.5 mg ml−1 concentration. However, it should be noted that these coefficients were time dependent and were found to decay as the diffusion front interacted with the retinal wall. A real-time, accurate, non-invasive method of tracking a bolus and its concentration is achieved using a high spatial resolution and fast scanning speed micro-CT system.

SU-E-J-180: A Characterization of the LAP Aquarius Phantom for External LAP Laser Alignment and MR Geometric Distortion Verification for the use of SRS Patient Simulation.

To explore additional application of the new Aquarius external laser alignment verification Phantom by LAP (Aq-LAP Phantom) examining geometric accuracy of magnetic resonance images (MRI) commonly used for planning intracranial stereotactic radiation surgery (ICSRS) cases. Newly designed external patient alignment lasers were first aligned by the Aq-LAP Phantom at a Siemens Magneton Vario 3T MR unit. The scans were then performed with the T1 Axial 3D MPRAGE protocols with 0.9 mm temporal resolution, which may be used for ICSRS. They also include FLAIR, T2 BLADE and Diffusion Axial TRACE imaging acquisitions with 1 mm temporal resolution. The MRI will be fused to 1 mm cut computerized tomography (CT) images acquired by a Siemens Somatom Sensation Open©. The geometric distortions (GD) were measured against the CT in all axial, sagital, and coronal directions at different levels. MR images of the Aquarius Phantom indicate a distinct similarity between the nonlinear GD along the z-axis crosshair and typical magnetic field gradient nonlinearity. There is linear correlation between MR divergence datasets of distorted crosshairs (p-values from 0.57 to 0.00), and nonlinear correlation between MR divergence datasets of the distorted crosshair with the CT divergence datasets of the cross plane (p-values from 8.45×10̂-4 to 1.38×10̂-46). The margin of error exceeded no more than 0.29 mm. GDs up to about 2 mm are observed at the distal regions of the longitudinal axis in the SRS treatment planning MR images. Using the Aquarius Phantom, one is able to detect GD in ICSRS planning MRI acquisitions, and align the external LAP patient alignment lasers by following the LAP QA. Based on the results, one may recommend using the Aquarius Phantom to determine if margins should be included for SRS treatment planning. The Aquarius Phantom, used for laser alignment and geometric distortion detection, was provided by LAP of America.

Passive movement of human soft palate during respiration: A simulation of 3D fluid/structure interaction

This study reconstructed a three dimensional fluid/structure interaction (FSI) model to investigate the compliance of human soft palate during calm respiration. Magnetic resonance imaging scans of a healthy male subject were obtained for model reconstruction of the upper airway and the soft palate. The fluid domain consists of nasal cavity, nasopharynx and oropharynx. The airflow in upper airway was assumed as laminar and incompressible. The soft palate was assumed as linear elastic. The interface between airway and soft palate was the FSI interface. Sinusoidal variation of velocity magnitude was applied at the oropharynx corresponding to ventilation rate of 7.5L/min. Simulations of fluid model in upper airway, FSI models with palatal Young's modulus of 7539Pa and 3000Pa were carried out for two cycles of respiration. The results showed that the integrated shear forces over the FSI interface were much smaller than integrated pressure forces in all the three directions (axial, coronal and sagittal). The total integrated force in sagittal direction was much smaller than that of coronal and axial directions. The soft palate was almost static during inspiration but moved towards the posterior pharyngeal wall during expiration. In conclusion, the displacement of human soft palate during respiration was mainly driven by air pressure around the surface of the soft palate with minimal contribution of shear stress of the upper airway flow. Despite inspirational negative pressure, expiratory posterior movement of soft palate could be another factor for the induction of airway collapse.

The value of unenhanced multi-detector computed tomography versus three-dimensional ultrasound in evaluating patients with impaired renal function and hematuria

Introduction: Unenhanced computed tomography (CT) is used to detect urinary tract calculi with high accuracy. The development of multi-detector CT (MDCT) allows reconstructions in coronal, sagittal and oblique directions. Objective: To compare MDCT with three-dimensional (3D) ultrasound (US) imaging in evaluating patients with impaired renal function and hematuria. Patients and methods: A total of 55 patients with hematuria and impaired renal function were examined with unenhanced MDCT and 3D US imaging at Al-Fayoum University Hospital between March 2008 and April 2010. Results: The diagnosis on unenhancedMDCTwas urolithiasis in 25 patients, psoas abscess with perinephritis in 2, chronic cystitis in 3, prostatic enlargement in 4, renal mass lesions in 3, vesical masses in 4, renal trauma in 2, adult polycystic kidney disease in 1, renal vein thrombosis in 1 and no specific abnormality in 10 patients. In diagnosing the cause of hematuria, the sensitivity was 82% for CT versus 73% for US. This can be attributed to the high sensitivity of CT (100%) in the diagnosis of urolithiasis, which is a common cause of hematuria. In the diagnosis of other causes of hematuria the sensitivity was 66% for CT versus 77% for US. The combination of MDCT and US increased the sensitivity to 87%. KEYWORDS: Unenhanced multi-detector computed tomography; Three-dimensional ultrasound; Impaired renal function; Hematuria

WE-B-201B-07: Volumetric Density Analysis Using Automated Whole Breast Ultrasound

Purpose: To estimate the volumetric breast density by using the new three-dimensional (3-D) ultrasound technique, automated whole breast ultrasound (ABUS), was proposed in this paper. Method and Materials: In this study, the ABUS and MRI data were obtained from 40 patients. The ABUS images were acquired by the ABUS machine using the 10 MHz linear transducer with width 14.7cm. Although the ABUS can scan the larger area of breast automatically, two to five passes of scanning are necessary to completely scan the whole breast. In this study, two passes are used to cover the whole breast. The volumetric data contain serial 2-D 548×348 slices with 16, 35, and 76 pixels/cm in the transverse, longitudinal, and coronal directions, respectively. Because the overlapping regions should be calculated only once in the density analysis, a vertical line across the nipple to cut the overlapping region in each image. Moreover, the non-breast region below the retromammary fat should not be included in the density analysis. Hence, the lowest horizontal plane was manually selected to cut the non-breast region. After segmenting the breast region, the fuzzy c-mean (FCM) classifier was used to differentiate the fibroglandular and fatty tissues in the ABUS and MRI images. The percent density and fibroglandular tissue volume were compared and correlated in both imaging modalities with the linear regression analysis. Results: The density of 3-D ABUS and MRI images for different BI-RADS categories of images was analyzed and the correlation factor R2 was up to 0.760. The volumes of ABUS and MRI images are also compared and their correlation factor R2 is 0.835. Conclusion: ABUS and MRI have high positive correlation for breast density quantification and both of them could provide the useful breast density information to physicians.

Dose verification of helical tomotherapy intensity modulated radiation therapy planning using 2D-array ion chambers

Purpose:To investigate the clinical usage of dose verification of Helical Tomotherapy plans by using 2D-array ion chambers, and to develop an efficient way to validate the dose delivered for the patients during treatments.Materials and Methods:A pixel-segmented ionisation chamber device, IMRT MatriXX™ and Multicube™ phantom from IBA were used on ten selected Tomotherapy IMRT/IGRT head and neck plans in this study. The combined phantom was set up to measure the dose distribution from coronal and sagittal planes. The setup of phantom was guided for verifying the correction position by pre-treatment Tomotherapy MVCT images. After the irradiation, the measured dose distributions of coronal and sagittal planes were compared with those from calculation by the planning system for cross verification. The results were evaluated by the absolute and relative doses as well as Gamma (γ) function. The feasibility of the different measuring methods was studied for this rotational treatment technique.Results:The dose distributions measured by the MatriXX 2D array were in good agreements with plans calculated by Tomotherapy planning system. The discrepancy between the measured dose and predicted dose in the selected points was within ±3%. In the comparison of the pixel-segmented ionisation chamber versus treatment planning system using the 3 mm/3% γ-function criteria, the mean passing rates of 2 mm dose grid with γ-parameter ≤1 were 97.37% and 96.91%, in two orthogonal planes (coronal and sagittal directions), respectively.Conclusion:MatriXX with Multicube is a new system created for rotational delivery quality assurance (QA) and found to be reliable to measure both absolute dose and relative dose distributions, simultaneously. It achieves the goal of an efficient and accurate dosimetry validation method of the helical delivery pattern for the Helical Tomotherapy IMRT planning.

The description of condyle position in disc displacement with reduction using Cone Beam Computed Tomography 3D radiographic analysis

One of the temporomandibular joint disorders that mostly occurs is disc displacement with reduction. Disc displacement that causes the displacement of condyle position can be evaluated by using radiograph. The Cone Beam Computed Tomography (CBCT-3D) is a radiograph equipment which is able to capture the condyle position from many directions. This research was aimed to see the condyle position in patients with disc displacement with reduction symptoms. This research was conducted to 11 patients with symptoms of disc displacement with reduction and 3 patients without symptoms of disc displacement with reduction as the counterpart. What was conducted to the sample was the radiographic imaging using CBCT-3D radiography, followed by measuring the joint space distance in the sagittal and coronal directions. The result of the research was analyzed using the T-test. Statistically, the result of the test showed a significant difference ( = 0.05) between patients with disc displacement with reduction symptoms and the patients without symptoms, in sagittal and coronal views. The conclusion led to the difference in condyle positions in patients with the disc displacement with reduction and patients without the symptoms which meant there was a condyle position displacement that caused the distance alteration in joint space in sagittal and coronal directions.

SU‐FF‐T‐310: Evaluation of Angular Response of 2D Diode Array Detectors with Buildup Phantom

Purpose: To evaluate the angular response of a 2D diode array with a buildup phantom using simulated volumetric modulated arc therapy (VMAT) beams. Method and Materials: A 2D diode array (MapCHECK™) with a 5‐cm thick buildup phantom (MapPHAN™) was scanned in horizontal and vertical orientations on a Philips Brilliance Big Bore CT scanner. Four treatment plans were generated for the phantom in 4 settings at 2 orientations with 10×10 cm2 open fields or different MLC‐shaped fields. All plans consist of eighteen equally spaced 6MV photon beams. Inhomogeneity corrections were applied to all four treatment plans. Dose deliveries were carried out on a Varian Cl‐iX machine while MapCHECK™ with MapPHAN™ combination was used for measuring the delivered doses with reproduced scanning parameters. The measured doses were compared with the plans using an in‐house evaluation software. A measured arc calibration factor from the setup was determined and applied to the final measurements. Results: The measured isodoses of all four plans show agreement with the plans. A gamma index with a 3% (dose difference, DD) and 3mm (distance‐to‐agreement, DTA) criteria was also used to evaluate comparisons of measured and TP data. Among the four plans in this study, the plan of horizontal position with different MLC‐shaped fields had the highest passing rate and the plan of vertical position with open fields was the worst. This is probably because the calibration is at horizontal position and different MLC shapes could even out some uncertainties due to the limited number of detectors. Conclusions: In this independent study, the angular response of MapCHECK™ with MapPHAN™ for rotational dosimetry has been evaluated in both coronal and sagittal directions. Results from our unique setting demonstrate that with the use of a properly calibrated 2D diode array and a buildup phantom VMAT patient QA is feasible and accurate.

Precision of cortical bone reconstruction based on 3D CT scans

The precision and accuracy of human cortical bone reconstruction using 3D CT scans was evaluated using machined bone segments. Both linear and angular errors were measured. Cadaver adult femoral and tibial cortical bone segments were obtained and machined in six orthogonal planes with a precision milling machine. CT scans were then obtained and the bone segments were reconstructed as digital replicas. Dimensional and angular measurements errors were evaluated for the machined bone segments and the results were compared with known dimensions based on milling machine settings to calculate errors due to scanning and model reconstruction. The model dimensional error in the coronal, sagittal and axial directions had a mean of 0.21 mm, with standard a deviation of 0.12 mm and a maximum error of 0.47 mm. The mean percent error was 0.74% and the maximum percent error was 1.9%. The angular error of models in the coronal, sagittal and axial directions was calculated, yielding a mean of 0.47° with a standard deviation of 0.37° and a maximum of 1.33°. The error in the cross-sectional axial direction had a mean of 0.54 mm with a maximum error of 0.83 mm, depending on the slice interval. The main error source was of the image processing, which was about 70% of the total error. We found that machining cortical bone segments prior to CT scanning is an effective method for accuracy evaluation of CT-based bone reconstruction. This method can provide a reference for assessing the sensitivity, reliability and accuracy of CT-based applications in the study of movement, finite element modeling, and prosthesis construction.

Coronal and apical sealing ability of a new endodontic cement.

This in vitro study aims to evaluate the coronal and apical sealing ability of gutta-percha (GP) root filling used with either mineral trioxide aggregate (MTA), new endodontic cement (NEC) or AH26 as filler/sealers. Forty eight single-rooted extracted teeth were selected, decoronated and then instrumented. Samples were randomly divided into three experimental (n=12) and two control groups (n=6). In group 1, root canals were filled using lateral condensation technique (L); while single cone technique (S) was used for groups 2 and 3. AH26, MTA and NEC were the root canal sealer/fillers in groups 1, 2 and 3, respectively. Samples were immersed in 1% methylene-blue dye and then independently centrifuged apically and coronally. The roots were split longitudinally and linear extent of dye penetration was measured with a stereomicroscope from apical and coronal directions. Data were analyzed using One-way ANOVA and T-test. No statistical differences in mean apical dye penetration between groups LGP/AH26, SGP/MTA and SGP/NEC were found; SGP/NEC group showed significantly less coronal dye penetration (P<0.001). Considering the limitations of this in vitro study, it was concluded that the simple single cone technique with NEC can provide favorable coronal and apical seal.

SU‐GG‐I‐53: The Impact of Scan Angles On the Visibility of Anatomy in On‐Board Digital Tomosynthesis (DTS) Images for Head and Neck Cancer Patients: A Single‐Observer Study

Purpose: To assess the impact of scan angles on the visibility of anatomy in on‐board digital tomosynthesis (DTS) images as a means to optimize this technique. Method and Materials: Head and neck cancer patients undergoing intensity‐modulated radiotherapy (IMRT) were enrolled onto this study. For each session, the patient was positioned using laser marks. On‐board imaging data sets including CBCT scans as reference, and DTS with 20° and 40° scan angles in the coronal or sagittal directions, respectively, were obtained. Visibility of selected anatomic structures (1=much better, 2=slightly better, 3=comparable, 4=slightly worse, 5=much worse) were assessed by a single observer. Wilcoxon Signed Ranks Test was performed to analyze the statistical significance. Results: Image data sets were collected from 30 treatment fractions for 12 patients. Overall, in coronal direction, there was no statistically significant difference in visibility between the DTS scan angles of 20° and 40° for base of tongue and cervical vertebral body (p = 0.083, 0.157, respectively), except for thyroid cartilage (p =0.025). In sagittal direction, only the hyoid was found to have a statistically significant difference in visibility (p = 0.025), while no significant difference was found for the rest of anatomic structures (p = 0.317, 0.157, 0.317 for base of tongue, cervical vertebral body, and epiglottis, respectively). However, when assessments for multiple fractions were averaged, no statistically significant difference was found for all anatomic structures in either coronal or sagittal directions. Conclusion: This single‐observer study shows that visibility of anatomy is roughly equal for the scan angle of 40° than 20° in both coronal and sagittal direction. Due to the limitations of single‐observer study, more definitive conclusion could not be drawn. Further analysis with a multiple‐observer study of more patients is needed to confirm this preliminary result.

MR arthrography in glenohumeral instability

The impact of accurate imaging in the work-up of patients with glenohumeral instability is high. Results of imaging may directly influence the surgeon's strategy to perform an arthroscopic or open treatment for (recurrent) instability. Magnetic resonance (MR) imaging, and MR arthrography in particular, is the optimal technique to detect, localize and characterize injuries of the capsular–labrum complex. Besides T1-weighted sequences with fat suppression in axial, oblique sagittal, and coronal directions, an additional series in abduction and exoroation position is highly advocated.

Method for determination of root curvature radius using cone-beam computed tomography images

This article describes and discusses a method to determine root curvature radius by using cone-beam computed tomography (CBCT). The severity of root canal curvature is essential to select instrument and instrumentation technique. The diagnosis and planning of root canal treatment have traditionally been made based on periapical radiography. However, the higher accuracy of CBCT images to identify anatomic and pathologic alterations compared to panoramic and periapical radiographs has been shown to reduce the incidence of false-negative results. In high-resolution images, the measurement of root curvature radius can be obtained by circumcenter. Based on 3 mathematical points determined with the working tools of Planimp software, it is possible to calculate root curvature radius in both apical and coronal directions. The CBCT-aided method for determination of root curvature radius presented in this article is easy to perform, reproducible and allows a more reliable and predictable endodontic planning, which reflects directly on a more efficacious preparation of curved root canals.

On-Board Patient Positioning for Head-and-Neck IMRT: Comparing Digital Tomosynthesis to Kilovoltage Radiography and Cone-Beam Computed Tomography

High-precision intensity-modulated radiotherapy demands high patient positioning accuracy. On-board digital tomosynthesis (DTS) provides three-dimensional (3D) image guidance for daily positioning with a lower imaging dose, faster acquisition, and more geometric flexibility than 3D cone-beam computed tomography (CBCT). This clinical study evaluated DTS as a daily imaging technique for patient positioning and compared the results with 3D CBCT and two-dimensional (2D) radiography. Head and neck cancer patients undergoing intensity-modulated radiotherapy were studied. For each session, the patient was positioned using laser marks. On-board imaging data sets, including 2D kilovoltage radiographs, DTS, and CBCT, were obtained to measure the daily patient positioning variations. The mean and standard deviations of the positioning variations in the translational and rotational directions were calculated. The positioning differences among 2D radiography, DTS, and CBCT were analyzed. Image data sets were collected from 65 treatment fractions for 10 patients. The systematic patient positioning variation was <0.10 cm and 1.0 degrees one dimensionally. The random variations were 0.27-0.34 cm in the translational and 0.93 degrees -1.99 degrees in the rotational direction. The mean vector isocenter variation was 0.48 cm. DTS with 40 degrees and 20 degrees scan angles in the coronal or sagittal directions yielded the same results for patient positioning. DTS performance was comparable to that of CBCT, with positioning differences of <0.1 cm and 0.5 degrees . The positioning difference between 2D radiography and DTS was approximately 0.1 cm and 0.2 cm in the vertical/longitudinal and lateral directions. Our results have demonstrated that DTS is a comparable 3D imaging technique to CBCT for daily patient positioning of head-and-neck patients as determined by manual registration of bony anatomy.

Improved Geometric Distortion in Coronal Diffusion-weighted and Diffusion Tensor Imaging Using a Whole-brain Isotropic-voxel Acquisition Technique at 3 Tesla

We used a whole-brain, isotropic-voxel acquisition technique to improve the geometric distortion in diffusion-weighted (DWI) and diffusion tensor imaging (DTI) in coronal directions, which is remarkable at high magnetic fields. We performed magnetic resonance imaging of 17 healthy volunteers using a 3T scanner and obtained coronal DWI/DTI as well as coronal images that were reformatted from isotropic volume data acquired by 1.6-mm-thick axial DWI/DTI. We visually evaluated the degree of image distortion and quantitated the findings by co-registration analysis. In-plane geometric distortions in coronal DWI/DTI, particularly at the frontal base and medial temporal lobe, were dramatically diminished when the isotropic-voxel acquisition technique was used. Quantitative measurement revealed a reduction in areas of misregistration, but not their absence, in reformatted coronal images, mainly because of distortion in the anteroposterior direction in the source images. The isotropic-voxel DWI/DTI technique enabled acquisition of coronal images that represented anatomical details accurately with permissible spatial distortion while maintaining spatial resolution, even at 3T.

Evaluation of cartilage repair in the distal femur after autologous chondrocyte transplantation using T2 relaxation time and dGEMRIC

To investigate the potential of combining T2 relaxation time and delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements after autologous chondrocyte transplantation (ACT). T2 and dGEMRIC maps were measured in the sagittal and coronal directions in 12 patients 10-15 months after ACT surgery. Grafts were assessed for bulk full thickness, superficial and deep tissue T2 and dGEMRIC values, and were compared to control cartilage. All ACT grafts showed filling of the repair area to the level of or above the articular surface. Matrix of the grafts lacked the classical laminar structure and appeared more heterogenous on T2 maps than control cartilage. As compared to control cartilage, ACT grafts showed significantly longer T2 values for bulk tissue as well as for the superficial 50% and deep 50% of tissue except for superficial cartilage in the coronal direction. dGEMRIC assessment in the sagittal and coronal directions did not show a significant difference between bulk, superficial or deep tissue as compared to the control cartilage. Superficial and deep ACT tissue did not differ statistically in terms of their T2 or dGEMRIC values. These preliminary results suggest that, according to T2 measurements, ACT repair tissue at 10-15 months differs from normal cartilage and probably lacks the preferential collagen arrangement of normal cartilage, while according to dGEMRIC a varying degree of proteoglycan replenishment takes place. Combining these two quantitative magnetic resonance imaging techniques enables a more comprehensive characterization of cartilage repair than before.

Oscillatory Shear Loading of Bovine Periodontal Ligament— A Methodological Study

This study examined the stress response of bovine periodontal ligament (PDL) under sinusoidal straining. The principle of the test consisted in subjecting transverse tooth, PDL and bone sections of known geometries to controlled oscillatory force application. The samples were secured to the actuator by support plates fabricated using a laser sintering technique to fit their contours to the tooth and the alveolar bone. The actuator was attached to the root slices located in the specimen's center. Hence the machine was able to push or pull the root relative to its surrounding alveolar bone. After determining an optimal distraction amplitude, the samples were cyclically loaded first in ramps and then in sinusoidal oscillations at frequencies ranging from 0.2 to 5 Hz. In the present study the following observations were made: (1) Imaging and the laser sintering technique can be used successfully to fabricate custom-made support plates for cross-sectional root-PDL-bone sections using a laser sintering technique, (2) the load-response curves were symmetric in the apical and the coronal directions, (3) both the stress response versus phase angle and the stress response versus. strain curves tended to "straighten" with increasing frequency, and (4) the phase lag between applied strain and resulting stress was small and did not differ in the intrusive and the extrusive directions. As no mechanical or time-dependent anisotropy was demonstrable in the intrusive and extrusive directions, such results may considerably simplify the development of constitutive laws for the PDL.

Three-dimensional finite element analysis of human temporomandibular joint with and without disc displacement during jaw opening

The aim of this study was to evaluate the differences of stress distribution in the temporomandibular joint (TMJ) disc during jaw opening between the subjects with and without internal derangement of TMJ (TMJ-ID). Three symptom-free volunteers and three symptomatic patients with anterior disc displacement were selected as normal and TMJ-ID subjects, respectively. For each subject, magnetic resonance images (MRI) were taken in the axial, sagittal and coronal directions. Using MRI taken, six three-dimensional finite element models of TMJ were developed. For each subject, the condylar movements during jaw opening were recorded and used as the loading condition for stress analysis. By comparing the calculated disc displacement to the measured one from MRI, the frictional coefficients were μ=0.001 for the normal subjects, but μ=0.01–0.001 for the TMJ-ID subjects. For the normal subjects, relatively high stresses were found at the anterior and lateral portions of the disc throughout jaw opening. In the connective tissues, the stress level was higher in the TMJ-ID than in the normal subjects. It is suggested that the disc displacement induces the change of stress distribution in the disc and the increase of frictional coefficients between articular surfaces, resulting in the secondary tissue damage.