[Digital thoracic radiology: devices, image processing, limits]. / Radiographie thoracique numérisée: appareillages, traitements d'images, limites.

In a first part, the different techniques of digital thoracic radiography are described. Since computed radiography with phosphore plates are the most commercialized it is more emphasized. But the other detectors are also described, as the drum coated with selenium and the direct digital radiography with selenium detectors. The other detectors are also studied in particular indirect flat panels detectors and the system with four high resolution CCD cameras. In a second step the most important image processing are discussed: the gradation curves, the unsharp mask processing, the system MUSICA, the dynamic range compression or reduction, the soustraction with dual energy. In the last part the advantages and the drawbacks of computed thoracic radiography are emphasized. The most important are the almost constant good quality of the pictures and the possibilities of image processing.

Use of magnetic resonance imaging for noninvasive characterization and follow-up of an experimental injury to normal mouse muscles.

A magnetic resonance imaging protocol was tested in a cardiotoxin-induced myonecrosis of hindlimb muscles of three normal mice to assess the usefulness of data provided by longitudinal follow-up of a few individuals. Magnetic resonance imaging examinations were performed sequentially at 4 T between days 1 and 11 post-injury. Axial T1-weighted images after injection of a paramagnetic contrast agent were used to determine the volume of lesions from regions of increased signal intensity. T2 measurements were performed from a single-slice ten-echo acquisition centered upon the largest section of lesion. Early after injury, a very large T2 increase was observed. As recovery proceeded, T2 values progressively decreased toward normal values. Similarly, the volumes of lesions decreased to virtually zero by days 10-11. The evolution of these indices followed the same time scheme observed in histological studies. The use of a volume probe allowed accurate measurement of T2 values, and the acquisition of volumetric data. Such magnetic resonance imaging follow-up should help gather valuable information using few animals.

Muscular transverse relaxation time measurement by magnetic resonance imaging at 4 Tesla in normal and dystrophic dy/dy and dy(2j)/dy(2j) mice.

Muscular transverse relaxation times values were measured in vivo in normal mice (strain C57BL6/J, n=14) and in murine models of human congenital muscular dystrophy (dy/dy, n=9; dy(2j)/dy(2j), n=8). A single-slice multi-echo sequence was used. Gastrocnemius/soleus complex, thigh and buttock muscles were studied. Muscular transverse relaxation times values were compared between different muscle groups in each type of animal and between animal groups. Differences were observed between normal and dy(2j)/dy(2j) mice from 3 to 12 weeks of age, and between normal and dy/dy mice at 6 weeks. In specific age ranges, the values of muscular transverse relaxation times in two dystrophic models are different from those in normal mice, and could thus be used as an index of modifications in dystrophic muscle to evaluate therapies.

[Techniques to improve the accuracy of CT-guided abdominal biopsy]. / Techniques permettant d'améliorer la rentabilité des ponctions abdominales sous scanner.

STUDY AIM: The aim of this paper is to present an overview of the various technical progresses made in the field of CT-guided abdominal biopsies. Recent improvements allowed to markedly increase the efficiency of biopsies and to decrease the number of complications. The main innovations concern the guidance technique itself with the availability of ultra-fast CT systems, the development of automated biopsy systems, which allow to improve the size and quality of tissue samples and numerous technical tricks, allowing an easier access to target lesions, either in patient positioning or in displacement of anatomical structures. A better management of tissue samples favored by a close collaboration with pathologists is also mandatory. The last section of the paper is an overview of the rare complications of CT-guided biopsies.

[Role of MRI in the diagnosis of breast diseases]. / Place de l'IRM dans le diagnostic des affections mammaires.

UNLABELLED: ADVANTAGES AND LIMITATIONS: Magnetic resonance imaging of the breast is probably the most sensitive method for detecting or ruling out breast disease. It is however not as specific as expected. TECHNIQUE: All examinations are performed with and without gadolinium intravenous administration, excepted in the case of silicone implant reconstruction mammoplasty. Dynamic contrast-enhanced MRI sequences are necessary with a permanent balance between temporal resolution, spatial resolution, and signal. MRI of the breast is not indicated as a routine examination in a screening program, neither to improve the specificity of infra-clinic lesions, nor in simply dense breasts without any known risk factor or in circumscribed masses. INDICATIONS: MRI is best used to improved the sensitivity of mammography and sonography in selected patients. The selected indications are: evaluation of the volume and extension of breast lesions evaluation of the therapeutic response after chemotherapy, and detection or exclusion of the local recurrence in patients with breast conservation therapy. PERSPECTIVES: The future indications and perspectives of MRI include interventional breast radiology (MRI-guided core biopsy), and thermocoagulation therapy. It may be interesting for the evaluation of patients with contrast enhanced MRI lesions with normal mammography and sonography, and also in woman with a genetically defined high breast cancer risk.

Closed ruptures of the flexor digitorum tendons: MRI evaluation.

OBJECTIVE: To assess the MRI findings in cases of closed rupture of the flexor digitorum tendons (FDT). PATIENTS AND DESIGN: Ten patients with a clinical suspicion of rupture of FDT underwent MRI before surgery. None of the patients presented a skin injury. Fingers were imaged using axial T1-weighted SE sequences, three-dimensional GE images, and curved reconstructions. RESULTS: Twelve FDT had surgical confirmation of rupture. Flexor digitorum profundus (FDP) and flexor pollicis longus (FPL) tendons were more frequently ruptured (n=8) than flexor digitorum superficialis (FDS) tendons (n=4). MR images accurately depicted the level of the rupture. The gap between the tendon ends (mean 45 mm, range 21-70 mm) was assessed best with curved reconstructions and was well correlated with the surgical findings. The proximal end mainly retracted into the palm or the carpal tunnel (n=8), and less frequently into the digital canal (n=4). In two cases, the proximal end curled up in the palm, clinically simulating a rupture of a lumbrical muscle in one case. MRI also showed the appearance of the adjacent tendons. CONCLUSION: MRI accurately depicted the level of rupture and the gap between the tendon ends, which assisted the surgical choice between suture, graft or tendon transfer.

Computed radiography.

In several medical centers computed radiography has almost completely replaced the use of conventional screen-film systems for general radiography. The aim of this paper is to explain the basic principles of the four most frequently numerical detectors used in the world, with emphasis on the phosphor plates, which are the most frequently used both in hospitals and by practitioners. The other two systems are based on a receptor with selenium. The fourth uses charged coupled device (CCD) detectors. The most important principles of digital processing are then described with concentration on unsharp mask filtering. In the future computed radiography will replace standard radiology and will create a system in medicine using the power of computers to archive--with more efficiency and less space--patient medical data. The transmission of data to workstations and the processing of this data is the topic of a new field in medicine.