C Pasteris

Impaired fMRI Activation in Patients with Primary Brain Tumors

To characterize peritumoral BOLD contrast disorders, 25 patients referred for resection of primary frontal or parietal neoplasms (low-grade glioma (LGG) (n=8); high-grade glioma (HGG) (n=7); meningioma (n=10)) without macroscopic tumoral infiltration of the primary sensorimotor cortex (SM1) were examined preoperatively using BOLD fMRI during simple motor tasks. Overall cerebral BOLD signal was estimated using vasoreactivity to carbogen inhalation. Using bolus of gadolinium, cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were estimated. In a 1cm(3) region-of-interest centered on maximal T-value in SM1 contralateral to movements, interhemispheric asymmetry was evaluated using interhemispheric ratios for BOLD and perfusion parameters. During motor tasks contralateral to the tumor, ipsitumoral sensorimotor activations were decreased in HGG and meningiomas, correlated to the distance between the tumor and SM1. Whereas CBV was decreased in ipsitumoral SM1 for HGG, it remained normal in meningiomas. Changes in basal perfusion could not explain motor activation impairment in SM1. Decreased interhemispheric ratio of the BOLD response to carbogen was the best predictor to model the asymmetry of motor activation (R=0.51). Moreover, 94.9+/-4.9% of all motor activations overlapped significant BOLD response to carbogen inhalation.

Perfusion-sensitive MRI of pilocytic astrocytomas: initial results

PurposeTo present the imaging and perfusion data obtained in nine patients with pilocytic astrocytomas (PA) and to discuss the original functional issues of this technique.MethodNine patients with pathologically proven PA underwent conventional and perfusion MR imaging. Various areas of relative cerebral blood volume (rCBV) within the tumors were obtained. The maximum rCBV ratios were identified and considered as representative of the tumor. The results were compared with the pathological findings.ResultsIn all patients, rCBV was <1.5 (mean 1) and the signal intensity curve overshot the baseline.ConclusionPA tend to have low rCBV values and a first-pass curve that crosses the baseline. These characteristics may be explained by the histological profile of the tumoral vascularity and are of relevance in the identification of these rare tumors.

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.

Spectroscopie 1H, perfusion, diffusion: quelle place pour ces techniques lors du diagnostic et du suivi des principales tumeurs cérébrales sus-tentorielles de l'adulte ?

Resume Introduction En quelques annees, l’IRM a evolue d’une exploration morphologique vers une exploration metabolique et fonctionnelle. Etat des connaissances L’IRM est la pierre angulaire du bilan des tumeurs cerebrales. Elle a un role lors du bilan initial et permet souvent une bonne caracterisation tissulaire du processus lesionnel. Toutefois, elle ne suffit pas a differencier abces, gliome malin et metastase unique, a apprecier le grade histologique des gliomes, a definir les limites tumorales, a caracteriser les tumeurs meningees. Elle a un role lors du suivi pour controler le geste operatoire, apprecier la reponse au traitement, rechercher des signes de recidive. Neanmoins, l’interpretation ne repose que sur des donnees volumetriques qui peuvent etre prises en defaut. Perspectives La spectroscopie 1 H, la diffusion et la perfusion, techniques disponibles sur la plupart des appareils cliniques apportent des informations complementaires sur le metabolisme et la vascularisation des tumeurs. Elles permettent une meilleure caracterisation tissulaire et une meilleure comprehension des modifications post-therapeutiques. Actuellement, aux donnees morphologiques du bilan IRM d’une tumeur cerebrale doivent s’ajouter des informations metaboliques et fonctionnelles.

Neurological imaging of brain damages after radiotherapy and/or chimiotherapy

Radiotherapy and chemotherapy may induce neurological toxicities with different appearances on CT and MRI scans. While optimized radiotherapy techniques have reduced some complications, new unwanted effects have occurred on account of therapeutic protocols involving the simultaneous use of radiotherapy and chemotherapy. Advances in radio-surgery, innovative anti-angiogenic therapies, as well as prolonged patient survival have led to the emergence of new deleterious side effects. In this report, we describe the early, semi-delayed, and late encephalic complications, while specifying how to identify the morphological lesions depending on the therapeutic protocol.