Investigation Of Cerebral Tumoral And Peritumoral Vascularization With MRI

Glioma is the most frequent primary brain tumor in adults. Tumoral vascularization by means of the mechanism of angiogenesis not only correlates closely to tumoral growth, but also has been proven as a new approach to cancer treatment using recent developed anti-angiogenic agents. Modern magnetic resonance imaging (MRI) is able to noninvasively investigate the tumoral vascularization in vivo. It plays a more important role in diagnostic and treatment of glioma as well as in the estimation of new drugs created for tumoral medications, including anti-angiogenic therapy. This thesis consists two parts:PartⅠ:OBJECTIVE: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. MATERIALS 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 with gadolinium first-pass technique. 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 St. Anne Hospital classification and followed-up clinically by means of MRI until their death or for a minimum of 5 years. Patients were also classified in gradeⅡand gradeⅢ-Ⅳ, according to the World Health Organisation (WHO) classification, and were analyzed with the same methods. Age, sex, treatment, tumor grade, contrast agent uptake, and rCBV were tested using survival curves with Kaplan-Meier 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 (ⅡversusⅢ-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 St. Anne Hospital classification, which separate the IIB from the IIA.PartⅡ:OBJECTIVE:To identify pathophysiological mechanisms associated with impaired peritumoral BOLD signal. MATERIALS AND METHODS: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), mean transit time (MTT), and time to peak (TTP) were estimated. In a lcm3 region-of-interest centered on maximal T-value in SMI contralateral to movements, interhemispheric asymmetry was evaluated using interhemispheric ratios for BOLD and perfusion parameters. RESULTS:During motor tasks contralateral to the tumor, ipsitumoral sensorimotor activations were decreased in HGG and meningiomas, correlated to the distance between the tumor and SMI. Whereas CBV was decreased in ipsitumoral SMI for HGG, it remained normal in meningiomas. Changes in basal perfusion could not explain motor activation impairment in SMI. 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. CONCLUSION:The map of BOLD response to carbogen inhalation could be able to better interpret the alterations of SM1 activation in patients with brain tumor.These two studies indicated that MRI techniques in testing and evaluation of tumoral vascularisation have a good application prospect.