F. Bing

Intérêt de l’imagerie de perfusion dans l’étude des astrocytomes pilocytiques et des hémangioblastomes : étude préliminaire

PURPOSE Pilocytic astrocytomas (PA) and hemangioblastomas (HB) can present the same morphological characteristics on conventional MRI sequences, most usually in the form of a cerebellar cystic mass with a mural nodule that strongly enhances on post-contrast T1 images. We discuss here the value of perfusion MRI in the differentiation of these two tumors, the diagnoses of which have already been histopathologically established. METHOD Eleven patients with PA and eight with HB underwent first-pass perfusion MRI. The maximum relative cerebral blood volume (rCBV(max)), defined as the ratio between the CBV(max) in tumor tissue and the CBV in healthy, contralateral white matter, is considered to be indicative of the type of tumor. RESULTS The difference between the rCBV(max) of PA (rCBV(max)=1.19+/-0.71, range 0.6-3.27) compared with that of HB (rCBV(max)=9.37+/-2.37, range 5.38-13) was significant (P<0.001). The first-pass curve crossed the baseline, corresponding to vascular permeability problems in both PA and HB. CONCLUSION The first-pass method of perfusion MRI is a quick and useful way to differentiate between PA and HB.

Prognostic value of perfusion MR imaging in patients with oligodendroglioma: A survival study

OBJECTIVE The purpose of this study was to evaluate retrospectively whether cerebral blood volume measurement based on pretreatment perfusion MRI is a prognostic biomarker for survival in patients with oligodendroglioma or mixed oligoastrocytoma. PATIENTS AND METHODS Between 1998 and 2004, 54 patients (23 females and 31 males), aged 21-73 years, with oligodendroglioma (or mixed tumour) were examined prior to beginning treatment with dynamic susceptibility-weighted contrast (DSC) perfusion MRI during gadolinium first-pass. The relative cerebral blood volume (rCBV) was calculated by dividing the measurement within the tumour by the measurement of the normal-appearing contralateral region. Patients were classified in two groups, grade A and grade B, according to the Saint-Anne Hospital classification and followed-up clinically and by means of MRI until their death or for a minimum of 5 years. Patients were also classified in grade II and grade III-IV, according to the World Health Organisation (WHO) classification, and were analysed with the same methods. Age, sex, treatment, tumour grade, contrast agent uptake, and rCBV were tested using survival curves with Kaplan-Meiers method, and their differences were analysed using the log-rank test. RESULTS In this population, median survival was 3 years. A rCBV threshold value of 2.2 was validated as a prognostic factor, for survival in these patients with oligodendrogliomas. Age, sex, contrast uptake, and maximum rCBV were found to be prognostic factors in univariate analysis. Multivariate analysis revealed that tumour grade (grade A/grade B), rCBV, age, and sex were prognostic factors independent of the other factors. The tumour grade according to the WHO classification (II versus III-IV) was also detected as an independent prognostic factor. CONCLUSION Pretreatment rCBV measured by DSC perfusion MRI was found to be a prognostic factor for survival in patients with oligodendroglioma or mixed tumour, by using the Saint-Anne Hospital classification, which separate the IIB from the IIA.

NR-WP-8 Pathologie du sinus caverneux

Objectifs pedagogiques Connaitre les elements vasculo-nerveux constituant la loge caverneuse ainsi que ses rapports anatomiques. Savoir explorer en IRM et TDM les sinus caverneux. Connaitre les principales anomalies pouvant se developper dans les sinus caverneux ou pouvant les envahir par contiguite. Messages a retenir La pathologie de la loge caverneuse est dominee par les extensions intracaverneuses des adenomes hypophysaires, les meningiomes et les lesions vasculaires. La thrombophlebite du sinus caverneux complique une infection sinu-sienne. Les tumeurs pouvant egalement envhir la loge caverneuse sont les chordomes, les chondromes et les cancers sphenoidaux et du cavum. Dans un contexte traumatique, la pathologie est dominee par la fistule carotido-caverneuse.

Pathologie tumorale des meninges intracraniennes

Objectifs Connaitre les aspects en imagerie des differentes lesions meningiomateuses. Connaitre l’apport des nouvelles sequences en IRM dans l’exploration d’une masse tumorale meningee. Connaitre les principaux diagnostics des lesions arachnoido-durales diffuses et arachnoido-piales. Messages a retenir Le meningiome presente divers sous-types anato-mopathologiques expliquant ses differences de comportement en IRM. Le meningiome peut etre agressif par son grade histologique et par sa capacite a envahir les tissus adjacents (structures vasculaires, extension foraminale...). La carcinomatose leptomeningee correspond a une dissemination arach-noido-piale des cellules tumorales. Elle est a distinguer des autres atteintes arachnoido-piales et des lesions diffuses arachnoido-durales, dominees par l’hypertension intracrânienne. Resume La pathologie tumorale meningee est largement dominee par le meningiome, dont le comportement en IRM est fonction du sous-type anatomopathologique. L’IRM a pour but de rechercher des signes d’agressivite ou un envahissement local. Les lesions pseudo-meningiomateuses sont rares, parfois non differenciables d’un meningiome. Les techniques de diffusion, perfusion et spectrometrie permettent de proposer des diagnostics differentiels. La carcinose leptomeningee peut etre primitive (melanose) ou secondaire. Les cellules tumorales peuvent egalement envahir les pachymeninges par une dissemination hematogene ou a partir d’une tumeur de la base du crâne qu’il faut rechercher. La localisation, le type de rehaussement et la semiologie IRM permettent de proposer des diagnostics differentiels.