Yasuhiro Kawahara

Fast spin-echo MR of the articular cartilage in the osteoarthrotic knee : Correlation of MR and arthroscopic findings

Purpose: the objective was to assess the efficacy of fast spin-echo (FSE) imaging in the detection of articular cartilage abnormality in osteoarthrosis of the knee Material and Methods: We studied 356 articular surfaces in 73 knees that had been examined by both MR imaging and arthroscopy. the MR images were obtained with FSE imaging (TR/TE 4200/100) on a 0.5 T unit. the surface abnormalities of the articular cartilage that were detected by MR imaging were compared with the arthroscopic findings Results: the overall sensitivity and specificity of MR in detecting chondral abnormalities were 60.5% (158/261) and 93.7% (89/95) respectively. MR imaging was more sensitive to the higher grade lesions: 31.8% (34/107) in grade 1; 72.4% (71/98) in grade 2; 93.5% (43/46) in grade 3; and 100% (10/10) in grade 4. the MR and arthroscopic grades were the same in 46.9% (167/356), and differed by no more than 1 grade in 90.2% (321/356) and 2 grades in 99.2% (353/356). the correlation between arthroscopic and MR grading scores was highly significant with a correlation coefficient of 0.705 (p<0.0001) Conclusion: FSE sequence was less sensitive to mild cartilage abnormality but useful in detecting moderate to severe abnormality and in evaluating the degree of articular cartilage abnormality

Gadolinium-enhanced MR imaging of the wrist in rheumatoid arthritis : value of fat suppression pulse sequences

Abstract Objective. To determine the usefulness of fat-suppressed gadolinium (Gd)-enhanced MR imaging of the wrist in patients with rheumatoid arthritis (RA). Design and patients. Fat-suppressed Gd-enhanced T1-weighted spin-echo (SE) images were obtained and compared with other standard techniques in 38 wrists of 27 patients (22–77 years) with RA. Scoring based on the degree of synovial enhancement of each joint was developed and the total scores (J-score) were correlated with radiographic stage, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and symptomatic change in the follow-up study. Results. Synovial proliferations showed marked enhancement in all the wrists. In addition, contrast enhancement in the bone marrow and tenosynovium was seen in 36 and eight wrists respectively. Fat-suppressed Gd-enhanced T1-weighted images demonstrated these abnormalities better than other techniques. The J-scores correlated well with values of CRP (P=0.0034), but not with radiographic stages and ESR. Conclusion. Fat-suppressed Gd-enhanced T1-weighted SE images can clearly demonstrate most of the essential lesions in RA including the proliferative synovium, bone erosion, bone marrow inflammatory change, and tenosynovitis. Scoring based on the extent of Gd-enhancement of synovium can be useful in the assessment of the inflammatory status.

MR Assessment of Movement and Morphologic Change in the Menisci during Knee Flexion

Purpose: To examine movement and morphologic alteration in the menisci during knee flexion. Material and Methods: Twenty healthy knees were imaged at 0°, 45°, and 90° of passive non-weight-bearing flexion in the sagittal plane with MR. In each meniscus, posterior movement distance during knee flexion and the ratio of anteroposterior (a.p.) diameter at flexion to that at extension were calculated. Results: Each meniscus moved posteriorly during knee flexion. Movement was greater in the anterior horn than in the posterior horn, and greater in the medial meniscus than in the lateral meniscus (p<0.05). the a.p. diameter of each meniscus was reduced at flexion (p<0.05). Conclusion: Knee flexion normally leads to posterior movement and shortening of the a.p. diameter of the menisci, which may be related to the positioning and curvature of femoral condyles at the femorotibial contact point at knee flexion.

MR assessment of meniscal movement during knee flexion: correlation with the severity of cartilage abnormality in the femorotibial joint.

Purpose The purpose of this study was to assess the degree of meniscal movement during knee flexion on MR images and to correlate it with the severity of cartilage damage in the femorotibial joint. Method Sagittal MR images were obtained at extension and 45° of flexion in 35 knees. A shortening ratio in the distance between the anterior and posterior horns at 0–45° of knee flexion was calculated in each meniscus and was correlated with the degree of cartilage abnormality in the femorotibial joint. Results The shortening ratio of the meniscus was reduced in knees with cartilage abnormality in the femorotibial joint. The shortening ratio of the medial meniscus was inversely correlated with the degree of cartilage abnormality in the medial femoral condyle and with that in the medial tibial plateau. Conclusion Restricted shortening ratio of the meniscus may be related to cartilage damage in the femorotibial joint.

Subchondral insufficiency fracture of the femoral head: Magnetic Resonance Imaging findings correlated with micro-computed tomography and histopathology

We described magnetic resonance (MR) imaging findings of subchondral insufficiency fracture of the femoral head without collapse in which micro-computed tomography (CT) and histopathologic studies were performed. Magnetic resonance imaging showed a subchondral low-signal intensity band, which corresponded to the fracture callus. Diffuse bone marrow edema with contrast enhancement effect was seen in both the proximal and distal segments of the low-signal intensity band. These features are distinct from those of avascular necrosis.

Bone mineral and other bone components in vertebrae evaluated by QCT and MRI.

To evaluate the usefulness of assessing bone components using magnetic resonance imaging (MRI), the contributions of bone components, including mineral, fat and collagen, to bone mineral density (BMD) and T1 relaxation time (T1) were studied using phantoms. Excised human vertebrae were also evaluated by quantitative computed tomography (QCT) and MRI. T1 was shortened with increasing quantities of fat and collagen. In water, T1 was significantly affected by bone density, while in oil, T1 became slightly longer as bone density increased. The presence of fat and collagen caused under- and overestimations of BMD, respectively. There was good correlation between T1 and BMD in osteoporotic vertebrae and the vertebrae with long T1 showed an increased content of hematopoietic marrow and/or abnormally increased bone mineral. It was concluded that the experimental data showed that MRI can contribute to the assessment of bone quality.

The Ulnar Nerve at Elbow Extension and Flexion: Assessment of Position and Signal Intensity on MR Images.

Purpose To assess the position and signal intensity of the ulnar nerve at elbow extension and flexion by using magnetic resonance imaging. Materials and Methods Institutional review board approval and written informed consent were obtained. Transverse T2-weighted images were obtained perpendicular to the upper arm in 100 healthy elbows of 50 volunteers (23 men, 27 women; age range, 21-57 years) and nine elbows with ulnar neuropathy (five men, four women; age range, 24-59 years) with extension and 130° of flexion. Ulnar nerve position was classified into three types: no dislocation, subluxation, or dislocation. One-way analysis of variance, paired t tests, Student t tests, and multiple regression analysis were used to analyze correlations between ulnar nerve movement angle during flexion and age, sex, presence of the anconeus epitrochlearis muscle, and ulnar neuropathy and to compare the contrast-to-noise ratio of nerve to muscle between extension and flexion. Results Nerve positions in healthy elbows were as follows: All had no dislocation at extension, and at flexion, 51 of 100 elbows (51.0%) had no dislocation, 30 of 100 elbows (30.0%) had subluxation, and 19 of 100 elbows (19.0%) had dislocation. Nerve movement angle was smaller in elbows with the anconeus epitrochlearis muscle than in those without the muscle (P = .045, .015). Presence of the muscle was the only significant factor associated with nerve movement angle (P = .047, .013). Only dominant elbows with nerve movement angle of less than 15° and nondominant elbows with nerve movement angle of less than 10° showed contrast-to-noise ratio increase at flexion (P = .021-.030). Conclusion Ulnar nerve movement during flexion was apparent in approximately half of healthy elbows and was similar between healthy elbows and elbows with ulnar neuropathy. Nerve signal intensity increased during flexion only in elbows without apparent nerve movement. (©) RSNA, 2016 Online supplemental material is available for this article.