[Diffusion-weighted MR imaging of the breast]. / Diffusion en IRM mammaire.

Diffusion-weighted imaging is helpful to further characterize lesions that remain indeterminate after morphological and dynamic MR evaluation. Suspicious lesions are hyperintense on diffusion-weighted images with corresponding low ADC values, indicating restricted diffusion and hypercellularity. Benign lesions and tumors responding to treatment usually have no diffusion restriction. ADC maps are useful for T2W hyperintense lesions that could mask the presence of restricted diffusion. Image fusion is sometimes needed to accurately localize enhancing lesions on ADC maps. For indeterminate lesions, a hypocellular appearance suggests a lower ACR category whereas the presence of restricted diffusion suggests a higher category.

[CT and MRI imaging in tumoral angiogenesis]. / Imagerie TDM et IRM de l'angiogenèse tumorale.

Angiogenesis is the process of activating dormant endothelial cells to form new vessels, after stimulation and it is essential in tumor growth. In many types of cancer, angiogenesis results from the activation of oncogenes that stimulate the production of Vascular Endothelial Growth Factor (VEGF). However, these newly formed vessels have a great number of abnormalities: increased density of fragile and hyper-permeable microvessels, arterial-venous shunts, caliber abnormalities and flow instabilities susceptible to flow direction inversion according to interstitial pressure. Anti-angiogenic treatments inhibit VEGF activity, perceived as structural and functional normalization of the microvascular pattern, such as reduced density of microvessels and restored morphology of the remaining ones. Conventional imaging techniques are not sensible to these changes, at best they show tumor size stabilization, hence the need of new techniques. Microvascularization imaging can be achieved by detecting functional disturbances to blood flow and not by showing the microvasculature per se. These techniques are based in quantifying the enhancement in tumor due to the passage of contrast agent after injection or protons labeled by a magnetic field. Through these measurements, one can derive interstitial and blood volumes as well as the tissue perfusion and capillary wall permeability. Microvascular imaging has greatly benefited from the improvements seen in CT and MRI equipment allowing large volume coverage with high spatial and temporal resolutions as from the evolutions in the methods to calculate, present and compare maps of the microcirculation and it's heterogeneity. However, software to analyze microvascularization are still rare, limiting the technique's application and validation in large scale. Nevertheless, imaging of the microcirculation is useful throughout the care of the oncological patient: it can reinforce the suspicious nature of a lesion, suggest anti-angiogenic treatment efficacy in hypervascular lesions, and show early treatment response before morphological changes as in RECIST criteria.

[Imaging and PET-CT of adult and childhood lymphoma]. / Imagerie radiologique et TEP scanner des lymphomes de l'adulte et de l'enfant.

Malignant lymphomas are lymphoproliferative disorders arising in both lymphoid tissue and non-lymphoid organ systems. Treatment rarely is surgical, and currently relies on a combination of chemotherapy and radiation therapy. The role of imaging is to determine the spread of the disease, to identify targets and to assess therapeutic response. Imaging techniques mainly use morphological criteria, and may underestimate infiltrative disease, as observed in bones. The frequent presence of residual masses after treatment usually prevents classification of patients as complete response. Over time, positron emission tomography (PET) with F18-fluorodeoxyglucose (FDG) has become a prominent part of the workup at diagnosis and during follow-up. Recently, PET has been integrated in the revised response criteria for malignant lymphoma.

[Computed tomographic atlas of benign asbestos related pathology]. / Atlas iconographique tomodensitométrique des pathologies bénignes de l'amiante.

The demonstration by computed tomography of abnormalities related to asbestos is essential for the recognition of industrial disease, the compensation of which has considerable economic consequences. The use of compute tomography, the most reliable technique for the detection of pleuro-parenchymatous abnormalities related to asbestos exposure, has increased considerably in France since the publication of the results of a consensus conference in Paris in 1999. Since that time, developments in technology have noticeably modified the protocols of investigation and increased the sensitivity of the detection of pleural and interstitial parenchymatous abnormalities and of nodules. The technical recommendations and those for the interpretation of pleural and parenchymatous abnormalities need to be well known. They are presented in the form of an atlas that gives detailed criteria for asbestosis, pleural plaques and pleural fibrosis. The diagnosis of pleural plaques depends on the combination of clear limits at the pleural and pulmonary interface, typical topography and multiple, bilateral localization. In the context of asbestos exposure the plaques are characteristic of this exposure, unlike diffuse pleural thickening, crow's feet images, parenchymatous bands and entrapped atalectasis. The writing of the radiological report would be most appropriate on this basis.

[Risks associated with MRI: safety rules, incidents, and accidents]. / Risque IRM: règles de sécurité, incidents et accidents.

It is now accepted that MR imaging does not present any biological risk for humans, even in cases of repeated exposure. However, several of the MR components (magnetic field, gradients, RF pulses, electrodes...) may cause some inconveniences to patients, most of them being reversible. However, severe accidents have been reported. Even though screening of patients for MR imaging eligibility is performed to identify patients with contra-indications to MRI, the lack of vigilance or the ignorance of certain basic safety requirements could lead to serious adverse effects, including death. The goal of this article is to review the various accidents reported with MRI, to explain their mechanism, and to describe means of prevention.

[Diagnosis of a malignant lymph node]. / Le diagnostic d'un ganglion tumoral.

There are several imaging techniques, each with advantages and limitations. Standard or computed radiography is always useful. CT diagnosis of an enlarged lymph node is easy but it is very difficult to conclude about its reactive or metastatic nature: subtle signs can help. MRI has similar pitfalls but sometimes it may be possible to identify fibrotic scarred nodes. US with Doppler can evaluate the abnormal angioarchitecture of a metastatic lymph node. Sentinel lymph nodes are easily identified by nuclear medicine. CT-PET provides morphologic and metabolic information which increases the diagnostic accuracy. Imaging work-up strategies for selected malignancies are discussed.

Evaluation of bone mineral density and fat-lean distribution in patients with multiple myeloma in sustained remission.

To study the usefulness of bone mineral density (BMD) in the follow-up of myeloma (MM) patients, BMD was evaluated in 44 MM patients in sustained remission for at least 2 years (35.4 +/- 10.5 months) after high-dose or conventional chemotherapy in a retrospective study. Patients never received bisphosphonates before or during the follow-up. Patients underwent lumbar spine (LS) BMD and a whole body (WB) BMD testing before therapy and at least once in the remission period. At baseline, mean LS BMD was 0.863 +/- 0.026 g/cm2, mean lumbar Z-score was -1.45 SD. LS BMD significantly increased from baseline by 5 +/- 1.8%, 9.3 +/- 1.7%, and 14 +/- 1.9% at 1, 2, and 3 years, respectively. The percentage of patients with a T-score below 2.5 SD decreased from 39% at baseline to 18.5% at 3 years. Compared with baseline, WB BMD decreased by -2.8 +/- 0.5%, -2.6 +/- 0.7%, and -1.7 +/- 0.6% at 1, 2, and 3 years, respectively. Mean percentage change of the fat compartment increased from baseline by +28.4 +/- 7.1% at the trunk, and +17.1 +/- 5% in peripheral areas at 3 years. In conclusion, in MM patients in remission after chemotherapy, LS BMD progressively increased after a mean follow-up of 3 years. These patients never received bisphosphonates, so this increase was related to the anti-myeloma treatment. The major effect on BMD was observed at the LS, which is primarily composed of trabecular bone containing the bone marrow. Interestingly, a drastic increase of the fat content was also observed. These results underlined that BMD and fat-lean evaluation could be of interest in the follow-up of MM patients.

Imaging of MALT lymphomas.

The broad category of non-Hodgkin's lymphoma includes a large variety of different diseases including indolent as well as aggressive lymphomas. Mucosa-associated lymphoid tissue (MALT) lymphoma arises in the extranodal mucosal lymphoid tissue and has only been recognised as a distinct entity in recent years. It affects one or several extranodal structures such as the stomach, the lung, the eye and salivary glands. The lymphoma is generally of low grade and has indolent course. The aim of this article is to exemplify the most common radiological patterns of MALT lymphoma.

[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.

Extranodal Hodgkin disease: spectrum of disease.

Extranodal lesions in Hodgkin disease may develop and spread to virtually any organ system, simulating other neoplastic or infectious diseases. It is important to determine whether extranodal involvement represents a primary manifestation or dissemination of systemic disease, which has a poorer prognosis. Computed tomography (CT) is the preferred modality, although ultrasonography and magnetic resonance (MR) imaging may also be helpful. CT is superior to conventional radiography in assessing chest disease, although MR imaging is more sensitive than CT in detecting chest wall involvement. CT is preferred for evaluating hepatic lymphoma and has proved particularly valuable in diagnosing gastric lymphoma and detecting renal or perirenal masses. CT and MR imaging are equally effective in detecting brain Hodgkin disease; however, the latter is superior in the detection of extracerebral tumor deposits in the subdural or epidural space. MR imaging is also preferred for evaluating meningeal and spinal cord involvement. Both MR imaging and CT allow excellent assessment of bone texture and accurate analysis of tumoral bone invasion, but MR imaging is superior in demonstrating bone marrow infiltration, and CT is superior in delineating the extent of cortical bone destruction. In the future, metabolic positron emission tomography may provide more information about extranodal lymphoma than do the current imaging modalities.

Image-guided core-needle biopsy in patients with suspected or recurrent lymphomas.

BACKGROUND: It is now commonly admitted that the diagnosis of recurrence of lymphoma can be assessed by image-guided needle biopsy (IGNB). However, the means of obtaining tissue for the original diagnosis of lymphoma is often surgery. The aim of this study was to compare the accuracy of IGNB at the time of diagnosis and at the time of recurrence or progression. METHODS: The authors performed 212 IGNBs on 194 patients who eventually had a diagnosis of lymphoma. One hundred three IGNBs were obtained at original diagnosis and 109 at recurrence or progression. Large-cutting core-biopsy needles, ranging in size from 20 gauge to 14 gauge, were used. Immunohistochemistry studies were performed in all lymphoma cases. RESULTS: A diagnosis of lymphoma with subtyping was obtained in 88% of all cases, in 85% at initial diagnosis, and in 89% at follow-up. Therapy was initiated on the basis of IGNB in 93% of all cases, in 91% at initial diagnosis, and in 94% at follow-up. Benign complications occurred in 7.5% of cases and did not require specific treatment. IGNB was equally effective for making a specific diagnosis of lymphoma and initiating therapy at the time of original diagnosis and at follow-up. CONCLUSIONS: The authors recommend that IGNB be performed as the initial procedure for the diagnosis of lymphoma in the absence of peripheral lymph nodes, either at presentation or at recurrence.

Diagnostic imaging of choroid plexus disease.

Disorders of the choroid plexus, a central nervous system structure, are rare, but can pose diagnostic difficulties. The purpose of this review is to illustrate the computed tomography and magnetic resonance imaging findings of a wide spectrum of lesions that affect the choroid plexus. The areas covered include (1) neoplasms (papilloma, leukaemia, meningioma, lymphoma and metastases); (2) infections (bacterial, fungal and viral); (3) cysts; (4) haemorrhage; (5) congenital abnormalities (Sturge-Weber syndrome, Klippel-Trenaunay-Weber syndrome and vascular malformations); and (6) non-infectious inflammatory disorders (xanthogranulomas, inflammatory pseudotumour, neurosarcoidosis, rheumatoid nodule and villous hypertrophy). Few of the patterns of choroid plexus involvement are specific for a particular pathological process. Guermazi, A. (2000) Clinical Radiology 55, 503-516.