• Imaging Science in Dentistry
• /
• 제31권4호
• /
• pp.185-192
• /
• 2001

Purpose: To evaluate the condylar movement at maximal mouth opening on MRI in patients with internal derangement. Materials and Methods: MR images and transcranial views for 102 TMJ s in 51 patients were taken in closed and maximal opening positions, and the amount of condylar movement was analyzed quantitatively and qualitatively. Results: For MR images, the mean condylar movements were 9.4 mm horizontally, 4.6 mm vertically and 10.9 mm totally, while those for transcranial views were 12.5 mm, 4.6 mm, and 13.7 mm respectively. The condyle moved forward beyond the summit of the articular eminence in 41 TMJs (40.2%) for MR images and 56 TMJs (54.9%) for transcranial views. Conclusion: The horizontal and total condylar movements were smaller in MR images than in transcranial views.

• 한국통신학회논문지
• /
• 제22권11호
• /
• pp.2425-2431
• /
• 1997

자기 공명 영상의 사용이 빈번해 짐에 따라 환자의 해부학적인 정확한 정보와 이를 빠르고 효과적으로 진단하는데 유용한 자동 영상 세그멘테이션 방법이 요구되고 있다. 본 논문에서는 오류 역전파 알고리즘으로 학습한 신경망을 이용하여 뇌의 자기 공명 영상을 자동적으로 세그멘테이션하는 방법을 제안한다. 특정 환자의 자기 공명 영상을 분할하여 학습시킨 신경망은 다른 환자의 자기 공명 영상도 자동적으로 세그멘테이션하여 뇌의 윤곽을 뚜렷하게 나타내었다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.719-722
• /
• 2003

This paper describes a novel experiment that measures the skin movement of a hand based on MR (magnetic resonance) images in conjunction with surface modeling techniques. The proposed approach consists of 3 phases: (1) MR scanning of a hand with surface makers, (2) 3D reconstruction from the MR images. and (3) registration of the 3D models. The results of registration are used to trace the skin movement with respect to underlying bone motions by measuring the positions of the surface markers.

• Imaging Science in Dentistry
• /
• 제44권1호
• /
• pp.43-52
• /
• 2014

Purpose: This study was designed to evaluate whether magnetic resonance imaging (MRI) is appropriate for detecting early changes in the mandibular bone marrow and pulp tissue of rats after high-dose irradiation. Materials and Methods: The right mandibles of Sprague-Dawley rats were irradiated with 10 Gy (Group 1, n=5) and 20 Gy (Group 2, n=5). Five non-irradiated animals were used as controls. The MR images of rat mandibles were obtained before irradiation and once a week until week 4 after irradiation. From the MR images, the signal intensity (SI) of the mandibular bone marrow and pulp tissue of the incisor was interpreted. The MR images were compared with the histopathologic findings. Results: The SI of the mandibular bone marrow had decreased on T2-weighted MR images. There was little difference between Groups 1 and 2. The SI of the irradiated groups appeared to be lower than that of the control group. The histopathologic findings showed that the trabecular bone in the irradiated group had increased. The SI of the irradiated pulp tissue had decreased on T2-weighted MR images. However, the SI of the MR images in Group 2 was high in the atrophic pulp of the incisor apex at week 2 after irradiation. Conclusion: These patterns seen on MRI in rat bone marrow and pulp tissue were consistent with histopathologic findings. They may be useful to assess radiogenic sclerotic changes in rat mandibular bone marrow.

• 한국임상수의학회지
• /
• 제37권6호
• /
• pp.317-323
• /
• 2020

The aims of this study were to describe the appearance and size of the normal canine prostate using magnetic resonance (MR) imaging and to calculate the apparent diffusion coefficient (ADC) values. MR images were obtained from seven intact male beagle dogs using a 1.5 T MR unit. The sequences included pre- and post-contrast T1- and T2-weighted imaging with and without fat saturation. The signal intensity of the prostate was compared with the adjacent musculature, fat, and urine in the urinary bladder. We recorded the mean prostatic length, width, and height and the length of the sixth lumbar vertebral body (L6). In addition, the prostatic length (rL), width (rW), and height (rH) ratios to L6 were calculated. Diffusion-weighted images of the prostate were obtained and ADC values were calculated. The prostate was bilobed and oval-shaped, homogenous on T1-weighted images, and heterogeneous with radiating lines on T2-weighted images. Post-contrast T1-weighted sequences showed contrast enhancement of the central and radiating striations. The prostatic capsule was clearly identified on post-contrast T1-weighted images with fat saturation. The ADC values were 1.72-2.04 × 10-3mm2/sec (mean, 1.88 × 10-3mm2/sec). Knowledge of the normal appearance of the prostate on MR images is essential to assess prostatic diseases in dogs.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.429-431
• /
• 2002

Metabolic analysis of biological tissues, the interventional radiology in MRT (Magnetic Resonance Treatment) and for clinical diagnoses, representation of 4-Dimensional (4D) structural information (x,y,z,t) of biological tissues is required. This paper discusses image representation techniques for those 4D MR Images. We have proposed an image reconstruction method for ultra-fast 3D MRI. It is based on image interpolation and prediction of un-acquired pictorial data in both of the real and the k-space (the acquisition domain in MRI). A 4D MR image is reconstructed from only two 3D MR images and acquired a few echo signals that are optimized by prediction of the tissue motion. This prediction can be done by the phase of acquired echo signal is proportioned to the tissue motion. On the other hand, reconstructed 4D MR images are represented as a 3D-movie by using computer graphics techniques. Rendered tissue surfaces and/or ROIs are displayed on a CRT monitor. It is represented in an arbitrary plane and/or rendered surface with their motion. As examples of the proposed representation techniques, the finger and the lung motion of healthy volunteers are demonstrated.

• Imaging Science in Dentistry
• /
• 제33권2호
• /
• pp.107-112
• /
• 2003

Purpose : To determine the relationship between clinical symptoms and magnetic resoncance (MR) images in patients presenting with temoporomandibular joint (TMJ) disorders. Materials and Methods: This study was based on 172 joints in 86 patients presenting with TMJ disorders. Joint pain and sound during jaw opening and closing movements were recorded, and the possible relationship between disc positions and bony changes of the condylar head and the articular fossa in MR images in the oblique sagittal planes were examined. Data were analyzed by Chi-square test. Results : There was no statistically significant relationship between clinical symptoms and MR images in the patients with TMJ disorders. Conclusion: In the patient with TMJ disorders, joint pain and sound could not be specific clinical symptoms that are related with MR image findings, and asymptomatic joints did not necessarily imply that the joints are normal according to MR image findings.

• 대한의용생체공학회:의공학회지
• /
• 제20권1호
• /
• pp.69-73
• /
• 1999

본 논문에서는 자기공명영상의 외부윤곽을 검출하기 위한 Snakes에 근거한 알고리즘을 제안하였다. 첫 번째 자기공명영상에서 물체의 외부윤곽을 수동으로 검출하고, 이를 다음 자기공명영상의 외부윤곽을 검출하기 위한 초기 제어점으로 사용하였다. 나머지 자기공명영상의 외부윤곽을 자동으로 검출하기 위하여 이웃한 영상간의 상관성을 이용한 에너지항을 Greedy Snakes알고리즘에 추가하였다. 제안한 알고리즘의 정확도를 평가하기 위해 BMD 측정방법을 사용하였으며, 제안된 알고리즘의 결과가 Greedy 알고리즘의 결과에 비해 높은 BMD 값을 얻음으로써 수동검출한 외부윤곽과 더욱 유사한 결과를 구할 수 있었다.

• 한국의학물리학회:학술대회논문집
• /
• 한국의학물리학회 2002년도 Proceedings
• /
• pp.322-323
• /
• 2002

Partial volume averaging effect of PET data influences on the accuracy of quantitative measurements of regional brain metabolism because spatial resolution of PET is limited. The purpose of this study was to evaluate the accuracy of partial volume correction carried out on $^{18}$ F-PET images using Hoffman brain phantom. $^{18}$ F-PET Hoffman phantom images were co-registered to MR slices of the same phantom. All the MR slices of the phantom were then segmented to be binary images. Each of these binary images was convolved in 2 dimensions with the spatial resolution of the PET. The original PET images were then divided by the smoothed binary images in slice-by-slice, voxel-by-voxel basis resulting in larger PET image volume in size. This enlarged partial volume corrected PET image volume was multiplied by original binary image volume to exclude extracortical region. The evaluation of partial volume corrected PET image volume was performed by region of interests (ROI) analysis applying ROIs, which were drawn on cortical regions of the original MR image slices, to corrected and original PET image volume. From the ROI analysis, range of regional mean values increases of partial volume corrected PET images was 4 to 14%, and average increase for all the ROIs was about 10% in this phantom study. Hoffman brain phantom study was useful for the objective evaluation of the partial volume correction method. This MR-based correction method would be applicable to patients in the. quantitative analysis of FDG-PET studies.

• 치과방사선
• /
• 제23권1호
• /
• pp.7-14
• /
• 1993

The Internal derangement of temporomandibular joint disc was evaluated by using magnetic resonance imaging and arthrogram in 5 patients having reciprocal clicking or locking and in 5 normal subjects. Parasagittal multisections on both closed and open mouth were serially obtained by using a 1.5 Tesla MR system and surface coil with CSMEMP, MPGR. MR images obtained were analized by correlating with images of arthrograms. The obtained results were as follows: 1. Displaced meniscus was clearly delineated as dark structure on MR images other than on arthrograms of closed mouth view of patient having clicking or locking. 2. The deltoid white images of synovial fluid were identified in the glenoid fossa and on the posterior surface of condyle on open mouth view and partly depicted on closed mouth view, of parasagittal sections by MPGR. 3. The greyish image of joint fluid was identified on the posterior surface of condyle on the open mouth view of parasagittal sections by CSMEMP. 4. The structural relationship among condyle, meniscus, and fluid showed the variety of images on each parasagitta1 view.