M. Rodallec

Diagnostic Imaging of Solitary Tumors of the Spine: What to Do and Say

Metastatic disease, myeloma, and lymphoma are the most common malignant spinal tumors. Hemangioma is the most common benign tumor of the spine. Other primary osseous lesions of the spine are more unusual but may exhibit characteristic imaging features that can help the radiologist develop a differential diagnosis. Radiologic evaluation of a patient who presents with osseous vertebral lesions often includes radiography, computed tomography (CT), and magnetic resonance (MR) imaging. Because of the complex anatomy of the vertebrae, CT is more useful than conventional radiography for evaluating lesion location and analyzing bone destruction and condensation. The diagnosis of spinal tumors is based on patient age, topographic features of the tumor, and lesion pattern as seen at CT and MR imaging. A systematic approach is useful for recognizing tumors of the spine with characteristic features such as bone island, osteoid osteoma, osteochondroma, chondrosarcoma, vertebral angioma, and aneurysmal bone cyst. In the remaining cases, the differential diagnosis may include other primary spinal tumors, vertebral metastases and major nontumoral lesions simulating a vertebral tumor, Paget disease, spondylitis, echinococcal infection, and aseptic osteitis. In many cases, vertebral biopsy is warranted to guide treatment.

Craniocervical Arterial Dissection: Spectrum of Imaging Findings and Differential Diagnosis

Craniocervical artery dissection is a potentially disabling yet probably underrecognized condition that often occurs in young and middle-aged adults. Accurate and prompt diagnosis of this condition is crucial because timely and appropriate therapy can significantly reduce the risk of stroke and long-term sequelae. Because of the great diversity in the clinical features of craniocervical artery dissection, imaging plays a primary role in its diagnosis. The increased diagnosis of this disorder in the past two decades can be attributed to an increased awareness of the clinical manifestations of internal carotid artery and vertebral artery dissection and to use of noninvasive diagnostic imaging techniques. To achieve an accurate diagnosis of craniocervical artery dissection, it is important to be familiar with its pathologic features (intimal tear, intramural hematoma, and dissecting aneurysm); the spectrum of imaging findings at color duplex ultrasonography, computed tomographic angiography, magnetic resonance (MR) imaging with MR angiography, and conventional angiography; and potential pitfalls in image interpretation.

Virtual Monochromatic Spectral Imaging with Fast Kilovoltage Switching: Reduction of Metal Artifacts at CT

With arthroplasty being increasingly used to relieve joint pain, imaging of patients with metal implants can represent a significant part of the clinical work load in the radiologists daily practice. Computed tomography (CT) plays an important role in the postoperative evaluation of patients who are suspected of having metal prosthesis-related problems such as aseptic loosening, bone resorption or osteolysis, infection, dislocation, metal hardware failure, or periprosthetic bone fracture. Despite advances in detector technology and computer software, artifacts from metal implants can seriously degrade the quality of CT images, sometimes to the point of making them diagnostically unusable. Several factors may help reduce the number and severity of artifacts at multidetector CT, including decreasing the detector collimation and pitch, increasing the kilovolt peak and tube charge, and using appropriate reconstruction algorithms and section thickness. More recently, dual-energy CT has been proposed as a means of reducing beam-hardening artifacts. The use of dual-energy CT scanners allows the synthesis of virtual monochromatic spectral (VMS) images. Monochromatic images depict how the imaged object would look if the x-ray source produced x-ray photons at only a single energy level. For this reason, VMS imaging is expected to provide improved image quality by reducing beam-hardening artifacts.

Séquences IRM « SWAN, SWI et VenoBOLD » exploitant le phénomène de susceptibilité magnétique : principes techniques et applications cliniques

Susceptibility-weighted MR sequences, T2 star weighted angiography (SWAN, General Electric), Susceptibility weighted imaging (SWI, Siemens) and venous blood oxygen level dependant (VenoBOLD, Philips) are 3D spoiled gradient-echo sequence that provide a high sensitivity for the detection of blood degradation products, calcifications, and iron deposits. For all these sequences, an appropriate echo time allows for the visualization of susceptibility differences between adjacent tissues. However, each of these sequences presents a specific technical background. The purpose of this review was to describe 1/the technical aspects of SWAN, VenoBOLD and SWI sequences, 2/the differences observed in term of contrast within the images, 3/the key imaging findings in neuroimaging using susceptibility-weighted MR sequences.

Diffusion-weighted MR imaging and pathologic findings in adult cerebellar medulloblastoma.

UNLABELLED OBJECTIVES, MATERIALS AND METHODS: The authors present the diffusion-weighted MR imaging and pathologic findings in two adult patients with cerebellar medulloblastoma. RESULTS Both presented with a vermian mass of the posterior fossa with low signal on SE T1 weighted images, and moderate enhancement of the mass after gadolinium injection. The tumors were of high intensity on diffusion-weighted images with low ADC value. The ADC values (x10(-3) mm2/s) were respectively 0.60 +/- 0.06 and 0.59+/-0.11 (tumor), and 0.65 +/- 0.04 and 0.67 +/- 0.07 (cerebellar white matter). Tumors were highly cellular and composed of densely packed small round cells with hyperchromatic nuclei and scanty cytoplasm. CONCLUSION diffusion-weighted MR imaging may be useful for the diagnosis of cerebellar medulloblastoma, due to their high cellularity and high nuclear-to-cytoplasmic ratio.

RevueSéquences IRM « SWAN, SWI et VenoBOLD » exploitant le phénomène de susceptibilité magnétique : principes techniques et applications cliniquesSusceptibility weighted magnetic resonance sequences “SWAN, SWI and VenoBOLD”: Technical aspects and clinical applications

Susceptibility-weighted MR sequences, T2 star weighted angiography (SWAN, General Electric), Susceptibility weighted imaging (SWI, Siemens) and venous blood oxygen level dependant (VenoBOLD, Philips) are 3D spoiled gradient-echo sequence that provide a high sensitivity for the detection of blood degradation products, calcifications, and iron deposits. For all these sequences, an appropriate echo time allows for the visualization of susceptibility differences between adjacent tissues. However, each of these sequences presents a specific technical background. The purpose of this review was to describe 1/the technical aspects of SWAN, VenoBOLD and SWI sequences, 2/the differences observed in term of contrast within the images, 3/the key imaging findings in neuroimaging using susceptibility-weighted MR sequences.

Helical CT of Pancreatic endocrine tumors

Pancreatic endocrine tumors are rare neoplasms. It is important to distinguish them from the more common ductal adenocarcinoma of the pancreas because they are slowly progressive and specific treatments are available. The CT findings of pancreatic endocrine tumors usually vary according to the functioning or nonfunctioning status. In this article, the authors illustrate typical and atypical CT findings of pancreatic endocrine tumors with radiopathologic correlations and give examples of other pancreatic conditions mimicking pancreatic endocrine tumors.

Optimization of Bacterial Diagnosis Yield after Needle Aspiration in Immunocompetent Adults with Brain Abscesses

OBJECTIVE Brain abscesses (BA) are life threatening, even in immunocompetent patients, in part because microbiological diagnosis is often lacking and management is empirical. Recent epidemiological changes make it all the more important to have a precise microbiological diagnosis. Our purpose was to evaluate the efficacy of a strategy aimed at obtaining a microbiological diagnosis in immunocompetent patients presenting with suspected BAs. METHODS We conducted a cohort study including all consecutive patients suspected of having BAs according to clinical, biological, and radiological findings. Severely immunocompromised patients were excluded. Aspiration was performed free-hand in patients with superficial abscesses (<1 cm depth from the cortical surface) and under stereotactic guidance in patients with deep-seated abscesses. Microbiological diagnosis was optimized, using the best aerobic and anaerobic growth conditions, blood culture bottles inoculated in the operating room, and molecular biology techniques if necessary. Antibiotic treatment was adapted according to the findings. RESULTS Twenty-six patients were suspected of having BAs during the study period. Twenty-four patients benefited from aspiration (stereotactic puncture in 3 cases), which was safe, confirmed the diagnosis of BAs, and yielded microbiological diagnosis in all cases, even in those patients who had previously received antibiotics (n = 8; 33%). In 10 patients (42%), microbiological results led to a different choice in antibiotic therapy than the recommended empirical regimen. CONCLUSION Microbiological diagnosis can be obtained in all cases of BA. This is achieved by the conjunction of rapid needle aspiration and the optimization of microbiological diagnosis resulting from fast management of the surgical specimen, good anaerobic culture conditions, and the use of blood culture bottles and molecular biology techniques when appropriate. Moreover, it is of clinical and therapeutic interest when BAs are suspected in immunocompetent patients.

Cranial nerve involvement in infratentorial progressive multifocal leukoencephalopathy

Neurology® 2012;79:104–105

Coupes axiales à l ′étage mésencéphalique : les coupes neuroradiologiques: Première partie: anatomie et atteintes mésencéphaliques primitives

Resume Toute exploration cerebrale en TDM et IRM comprend des coupes axiales passant par le mesencephale dont la forme de cœur caracteristique est facilement reconnaissable. A cet etage, une grande variete de structures anatomiques est visible dont l′atteinte peut etre responsable de symptomes varies. L′etude de ces coupes permet egalement de reconnaitre les signes d′hypertension intra-crânienne et d′apprecier la gravite de pathologies sus et sous-tentorielles pour adapter la prise en charge therapeutique.