EMC - Radiologie最新文献

Benign bronchopulmonary tumours are uncommon but various. In 1999, the World Health Organisation proposed a new classification of these tumours, based on histological criteria and tumour location. New imaging methods improve morphologic (High resolution multislice CT, MRI) and dynamic (18 FDG PET, contrast-enhanced CT and MRI) evaluation of pulmonary nodules. Some benign pulmonary tumours (such as lipomas, and the harmatoma which is the most frequent) show enough specific findings to avoid invasive diagnostic procedures. However, radiological findings of other benign tumours are non specific. Moreover, small nodules and malignant tumours acting like benign lesions (carcinoid tumours, adenocarcinomas) are hardly classifiable. In all these cases, histological analysis is needed. Even if needle aspiration or percutaneous biopsy is negative, diagnostic should be completed by surgical resection.

Unusual breast lesions are a diagnostic challenge. These lesions include systemic diseases, benign tumours, primary or metastatic malignant tumours. Lymphadenopathy is the most common finding associated to collagen disease. Diabetic mastopathy results in a very hard mass, with US aspect of a hypoechoic mass, attenuating, while imposing for a malignant tumour. The fibromatosis can also simulate a primitive cancer (irregular dense mass in mammography, hypoechoic and attenuating in sonography). The giant cells tumour generally results in a regular, heterogeneous mass. The phyllodes touch the young woman; they are characterized by a benign mass type, round, increasing size rapidly. Medullar carcinoma is important to diagnose because of its best forecast. It carries out a round or oval mass, with regular shapes. The histological diagnosis is difficult. The lymphoma appears as one or more well circumscribed masses, not calcified. Mammary metastases produce regular, not very dense masses or a diffuse cutaneous thickening. The radiologist must familiarize himself with these aspects in order to avoid the traps diagnoses and to allow an early and appropriate management.

Imaging of normal and pathologic trachea at the thoracic and cervical levels is described extensively. Beside congenital abnormalities discovered in adulthood, acquired tracheal abnormalities are artificially divided in two subgroups. One group consists of diffuse abnormalities, with all but one diseases associated with a diffuse narrowing of the tracheal lumen. The other group comprises focal abnormalities that lead to tracheal stenoses of various lengths, with a postintubation stenosis as probably the most frequent cause, followed by tumours. The main modality for tracheal imaging is now multidetector-row spiral CT. This technique allows for faster volume coverage and higher spatial and temporal resolution. The improved spatial resolution impacts on both axial images and all reconstructions techniques that have become indispensable for interpretation of a vertical structure such as the trachea. Chest X-ray is no longer the frontline imaging technique. MRI has not yet reached all its potential as compared to CT.

Paget's disease is a frequent disorder, characterized by an accelerated bone remodelling. Initial focal bone resorption and the subsequent increased bone formation may mimic several bone disorders, in particular those of neoplastic origin such as the “ivory vertebrae”. In the vast majority of cases, Paget's disease can be diagnosed radiologically, on the basis of typical spectrum of changes, combined changes in bone shape (hyperplasia and enlargement, plastic deformations), in bone density (initial osteolysis, and subsequent osteosclerosis) and in bone structure: a typical thickening with increased porosity of the cortical bone, combined with hypertrophy of the trabecular bone, resulting in the so-called “cortico-trabecular dedifferenciation”. The characteristic distribution of these changes (which may involve one or several bones, either partially or totally, but never the whole skeleton) is an additional hallmark of Paget's disease. In case of uncertainty, MRI is the most appropriate complementary investigation to confirm the diagnosis by demonstrating the characteristic pagetic bone content: persistence of an almost normal fatty marrow signal, intricated with focal signal changes due to hyperostosis (increased mineral bone mass) and with limited amounts of fibro-vascular tissue. Finally, MRI is the preferential tool for early detection of the most fearsome complication of Paget's disease: the malignant transformation that induces the development of abnormal tissue, both inside and around the pagetic bone.

Cross sectional imaging for the diagnosis of Crohn's disease has benefited from recent technological advances regarding multi-detector computed tomography and rapid imaging with MRI. Both CT and MRI are useful for early diagnosis and characterization of the wall and peritoneal diseases. Multi-detector CT can show the diseases with multiplanar reconstruction, and MRI with rapid sequences is recommended for the imaging of recto-anal complications. CT and MRI may now be included in the evaluation of a patient with Crohn's disease, along with conventional imaging and endoscopy.

Atelectasis is one of the most commonly encountered abnormalities in chest radiology. The presence of such abnormality must be considered on the basis of a standard face chest X-ray, eventually helped by a lateral view. These disorders of ventilation may be related to a decrease (atelectasis or collapse) or an increase (air trapping) of the lung volume. In this article, following a brief review of the different radiological techniques and radio anatomy of lung segmentation, we describe the pathophysiology, mechanisms and radiological signs of ventilation disorders. We underline the essential role of CT scanning and the recently highlighted potentialities of multiplan reconstruction.

The duodenum is the first part of the small bowel. It extends from the pylore to the duodeno-jejunal flexure. The duodenum is divided into four parts. Endoscopy is usually the first-line imaging technique used in case of suspected duodenal abnormalities. Barium examination with double contrast technique has a good sensitivity for detailed evaluation of mucosal lesions and bowel wall. Ultrasonography and computed tomography may sometimes detect duodenal lesions previously unsuspected. Magnetic resonance imaging may also appreciate the duodenum. As the duodenum is located around the pancreatic head, cross section imaging is frequently used to evaluate simultaneously these two structures.

Neurodegenerative disorders are a group of diseases which all induce a progressive dysfunction of the central nervous system. Until recently, neuro imaging played only a marginal part in their diagnosis, and was mostly useful for the follow-up of some disorders. However, in the last score years, the ability of MRI to differentiate normal from pathological brain ageing has steadily improved. Three dimensional acquisitions and multi planar reconstructions enable precise volumetric measurements of individual brain regions. They are used to classify dementias and focal degenerative brain disorders. More recently, functional MRI methods (such as functional MRI, diffusion imaging and diffusion tensor imaging) and metabolic analyses (such as PET, SPECT and MR spectroscopy) provide insights on the physiopathology of these diseases. These methods are still mostly used in research settings but will progressively play an increasing part in the clinical management of these patients.

The knee joint consists of different structures that may be evaluated separately by Magnetic Resonance Imaging. This is a non invasive way to assess cruciate ligaments and menisci. Stabilization of the posteromedial corner of the knee is ensured by the deep crural fascia and the medial collateral ligament, the joint capsule and the meniscopatellar ligament. The most important stabilizing structures of the posterolateral corner of the knee are the lateral collateral ligament, the popliteal muscle and tendon, and the bicipital tendon. Structures enforcing the anterior articular capsule are the patellar tendon and the retinaculum patellae.