[Stress fractures]. / Les fractures de contrainte.

In 1892, J. Wolff, an orthopedic surgeon, stated that the internal architecture and shape of a bone were related to the direction of stresses placed upon it. Conventional radiographs and MRI can demonstrate the adaptability of bones to stresses. Imaging also demonstrates that this adaptability has limitations, and that excessive stress may lead to fracture.

[Vertebroplasty: 10 years clinical and radiological follow-up]. / Vertébroplastie: évaluation clinique et radiologique à plus de dix ans.

OBJECTIVES: Ten years follow-up of the first patients treated with percutaneous vertebroplasty. PATIENT AND METHODS: Eighteen patients were retrospectively reviewed having undergone vertebroplasty in our centre between 1989 and 1998. Eight were treated for angioma, eight for osteoporotic compression and two followed for myeloma. They all underwent clinical and radiological evaluation in 2007 (standard X-rays, CT scan and MRI). These examinations were compared to prior baseline pre- and post-therapeutic images. RESULTS: Radiological characteristic of cement remained unchanged in the long term and there was no modification of anatomical structures in contact with it. Even if the distribution of cement was asymmetrical there was no fracture of the treated vertebras at distance. Degenerative changes of discs facing the vertebroplasty were not more pronounced than for distant discs. We found no significant signal or density anomaly of disc in contact direct with cement. 38.8 % of the patients presented new fractures (n=30). Seventy percent of the fractures were multiple and contiguous. In the long term, all patients reported improvement of pain after the procedure. CONCLUSION: In our series, we found a good stability of treatment over time. This study shows the long-term safety of percutaneous acrylic vertebroplasty, in particular harmlessness of cement for bone and discs in contact.

[MR breast screening in patients with genetic mutation]. / Dépistage du cancer du sein par IRM chez les femmes porteuses d'une mutation génétique.

PURPOSE: To compare screening breast MRI with conventional screening techniques in high-risk patients with genetic mutation. MATERIALS AND METHODS: Prospective study of 85 patients (mean age of 43 years) with genetic mutation and screening > or = 2 years (mean of 2.7 years, 231 screening examinations). BI-RADS lesions 3-5 were biopsied; isolated BI-RADS 3 lesions on MRI were followed. Results from both techniques were compared. The number of short interval follow-up examinations and biopsy results were reviewed. RESULTS: Eight cancers were diagnosed (3 in situ, 5 invasive carcinomas including an interval cancer, mean size of 14 mm). The sensitivity values for mammography, US and MRI were 12.5%, 50% and 95%, and specificity values were 98.7%, 97.3% and 94.8% respectively. Nineteen short interval follow-up MRI examinations were performed (19%): 14% of patients at initial screening and 5% and 6% at the the second and third screenings. Thirty-two biopsies were performed in 17 patients, including 18 after MRI (PPV of cytology: 30%, and biopsy: 58%). CONCLUSION: Our results confirm the value of MRI for screening of high-risk patients with genetic mutation.

Volumic patient-specific reconstruction of muscular system based on a reduced dataset of medical images.

Three-dimensional mechanical modelling of muscles is essential for various biomechanical applications and clinical evaluation, but it requires a tedious manual processing of numerous images. A muscle reconstruction method is presented based on a reduced set of images to generate an approximate parametric object from basic dimensions of muscle contours. A regular volumic mesh is constructed based on this parametric object. The approximate object and the corresponding mesh are deformed to fit the exact muscles contours yielding patient-specific geometry. Evaluation was performed by comparison of geometry to that obtained by contouring all computed tomography (CT) slices, and by quantification of the mesh quality criteria. Muscle fatty infiltration was estimated using a threshold between fat and muscle. Volumic fat index (VFI) of a muscle was computed using first all the complete CT scan slices containing the muscle (VFI(ref)) and a second time only the slices used for reconstruction (VFI(recons)). Mean volume error estimation was 2.6% and hexahedron meshes fulfilled quality criteria. VFI(recons) respect the individual variation of fat content.

[Soft tissue tumors and pseudotumors of the foot and ankle]. / Tumeurs et pseudo-tumeurs des tissus mous de la région pied-cheville.

Soft tissue masses around the foot and ankle are frequent. While benign lesions are two times more frequent than malignant lesions, the latter still represent one third of all lesions. The main purpose of this article is to propose a systematic approach to the differential diagnosis of soft tissue tumors of the foot and ankle based on a combination of 5 elements: clinical history and physical examination, top 10 most frequent diagnoses, patient age, lesion location, and MRI features of the mass. Selected soft tissue tumors will be described and illustrated with emphasis on these 5 elements.