M. Osteaux

A method for myelin fiber orientation mapping using diffusion-weighted MR images

In the past, the anisotropic diffusion of water molecules in white matter in the brain has been correlated to the basic symmetry of the myelin fibers: water diffuses more readily along the fiber direction than perpendicular to it. As a consequence, diffusion sensitized magnetic resonance imaging can be expected to be useful for studying the fiber orientation. In this work, we present a method for exploiting this type of information to map the fiber orientations in the image plane. It makes use of three diffusion-weighted images with sensitizing gradients along x, y and u, an axis at 45 degrees with respect to x and y. The orientation information contained in these images is summarized in a single image representing the angle between the fiber direction and a fixed axis, making use of a cyclic color scale. The method is evaluated using computer simulations for a variety of diffusion weighting strengths and signal-to-noise ratios, tested on a phantom and illustrated on an in vivo example. An extension to the determination of the fiber orientation in three dimensions is also described.

Popliteal cysts in children: prevalence, appearance and associated findings at MR imaging

Objective. The purpose of this study was to determine the prevalence of Bakers cysts on MR images in a paediatric orthopaedic population, to investigate the association of Bakers cyst with joint fluid and joint disorders in children, and to compare the MR appearance of Bakers cysts in children with that previously reported in adults. Materials and methods. Reports from 393 MR studies of the knee performed in children aged from 1 to 17 years were retrospectively reviewed for the presence of a Bakers cyst, joint effusion, meniscal tear, anterior cruciate ligament tear, or any other joint disorder. Results. A Bakers cyst was identified in 6.3 % (25/393) of patients. The MR images and clinical charts of patients with a Bakers cyst were reviewed. None of the 25 patients with a Bakers cyst had an associated anterior cruciate ligament tear or meniscal tear. Two patients had osteochondritis dissecans and two others had synovial disease (infection and juvenile rheumatoid arthritis). Joint fluid was demonstrated in 16 % (4/25) of patients with a Bakers cyst. There was no statistically significant association between presence of a Bakers cyst and presence of joint fluid. Conclusions. Bakers cyst is less prevalent in a paediatric orthopaedic population than in an adult population. In children, it seems that Bakers cyst is seldom associated with joint fluid, meniscal tear, or anterior cruciate ligament tear. On MR images, a communication between the Bakers cyst and the joint was not demonstrated in any of the patients. In addition, the presence of debris and cyst leakage was not observed.

Medial meniscocapsular separation: MR imaging criteria and diagnostic pitfalls.

Various magnetic resonance imaging (MRI) signs can be used in the diagnosis of medial meniscocapsular separation. A thorough knowledge of the normal anatomy of the medial meniscocapsular junction is essential to understand these signs. MRI signs used in the diagnosis of meniscocapsular separation include meniscal displacement relative to the tibia, meniscal corner tear, perimeniscal fluid, irregular meniscal outline, meniscofemoral and meniscotibial extension tears, and interposition of contrast medium between the meniscus and the MCL. Potential causes of false positive diagnosis of meniscocapsular separation include MCL bursitis, meniscal cyst, MCL tear, joint effusion, and perimeniscal fat.

Fat fraction of lumbar bone marrow using in vivo proton nuclear magnetic resonance spectroscopy

Localized proton spectra of the human lumbar vertebral body were recorded in vivo at 1.5 T, using the STEAM (stimulated echo acquisition mode) pulse sequence. Thirty-seven patients (18 men, 19 women) were examined, ranging in age from 21 to 68 years (mean = 40, SD = 13). The fat fraction of the bone marrow was calculated from the areas of the fat and water peaks in the spectrum. The results demonstrate that, in the course of aging, there is a systematic increase in measured fat percentage of about 7% per decade of age. No sex difference could be established on the basis of our results.

Reducing inter-observer variation in thyroid volume calculation using a new formula and technique

OBJECTIVE Ultrasound (US) measurement of thyroid volume is used in diagnosis and follow-up of patients with thyroid disease. We assessed a new formula and technique for thyroid volume calculation, based on an automatically continuous trace transverse surface area (aTSA) calculation, to ascertain where this technique could reduce inter-observer variation. METHODS Three observers with a different level of US expertise, using a 12-5 MHz linear transducer, examined 25 volunteers. Inter-observer variations were calculated for diameter measurements and for the thyroid lobe volume calculations using the single factor ANOVA method. RESULTS Using the new technique and formula, no statistically significant differences existed, in contradistinction to using the classical formula for an ellipsoid (P=0.02). CONCLUSION When thyroid volume measurements are required, we recommend using a new method of thyroid volume calculation based on the use of an automatically calculated continuous trace aTSA measurement to avoid significant inter-observer variation in calculation of thyroid lobe volumes.

Inverted Meckel's diverticulum as a leading point for ileoileal intussusception in an adult: case report

Intussusception due to an inverted Meckels diverticulum is considered a rare occurrence. We present a case of a 37-year-old male with anemia and melena due to an inverted Meckels diverticulum at the base of an ileoileal intussusception. To our knowledge, this is the first case in which small bowel enema, computed tomography, and magnetic resonance imaging showed the pathology.

Deconvolution of dynamic contrast-enhanced MRI data by linear inversion: Choice of the regularization parameter

Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast‐enhanced MRI. Two robust methods for the selection of the truncation threshold on a pixel‐by‐pixel basis—generalized cross validation (GCV) and the L‐curve criterion (LCC)—were optimized and compared to paradigms in the literature. The methods lead to improvements in the estimate of the residue function and of its maximum and converge properly with SNR. The oscillations typically observed in the solution vanish entirely and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1–2 min in calculation time and isolated instabilities in the image. It is argued that the latter problem may be resolved by optimization. Simulated results for GCV and LCC are equivalent in terms of performance, but GCV is faster. Magn Reson Med 52:209–213, 2004.

MR imaging of meniscal cysts: evaluation of location and extension using a three-layer approach.

PURPOSE To analyze the extension of medial and lateral meniscal cysts relative to the capuloligamentous planes of the knee. MATERIALS AND METHODS The MR images of 32 patients with meniscal cysts were reviewed. The location and extension of the meniscal cysts with reference to the capsule and ligaments were recorded. RESULTS Most medial meniscal cysts were located posteromedially. Posteromedial meniscal cysts usually penetrated the capsule and were located between layer I and the fused layers II+III. From this site some extended anteriorly and then became located superficial to the superficial MCL. The location of lateral meniscal cysts was more varied. Anteriorly the cysts were located deep to the iliotibial band, whereas posterolateral cysts were located deep to the lateral collateral ligament. CONCLUSION Although the site of capsular penetration of meniscal cysts is determined by the location of meniscal tears, the possible pathways of extension appear to be determined by the capsuloligamentous planes of the knee.

Rib fractures induced by coughing: An unusual cause of acute chest pain

We report three patients with stress fractures of the ribs induced by coughing. Standard radiographs of the chest and ribs did not reveal evidence of rib fractures in any of the patients. Bone scintigraphy, performed 1 to 2 weeks after initial onset of symptoms, showed a focal area of increased uptake along the chest wall in all cases. Thin section angulated helical CT directly visualized the subtle rib fractures. Initial diagnosis of a cough-induced fracture of the rib may be difficult because of the associated underlying disorder, and unnecessary examinations are commonly performed. Identification of a cough-induced fracture of the rib using helical CT may be clinically important to avoid unnecessary concern and additional examinations.

Can bone marrow edema be seen on STIR images of the ankle and foot after 1 week of running

PURPOSE To evaluate whether initiation of running in sedentary individuals would lead to bone marrow edema on MR images, within the time span of 1 week. MATERIALS AND METHODS The feet of 10 healthy volunteers were imaged by MR imaging before and after running during 30 min a day for 1 week. The images were evaluated by consensus of 2 musculoskeletal radiologists who graded the presence of bone marrow edema on a 4-point scale. Edema scores and number of bones involved before and after running were compared statistically. RESULTS Edema was present on the baseline images in 3 subjects. After running edema showed an increase or was present in 5 subjects. The changes after running were statistically significant. Bones involved were the talus, calcaneus, navicular bone, cuboid bone, and 5th metatarsal. CONCLUSION Edema patterns can be seen in the feet of asymptomatic individuals. During initiation of running an increase of edema or development of new edema areas can be seen.