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USE OF DSC-MRI IN DIFFERENTIATING BETWEEN TRUE AND PSEUDO-PROGRESSION IN PATIENTS WITH GLIOBLASTOMA Free

INTRODUCTION: MRI is used routinely to assess response to chemo-radiotherapy for glioblastoma (GBM). However, distinguishing between treatment effects and disease progression using published criteria based on contrast-enhancement on T1-weighted images is difficult. The phenomenon of pseudo-progression (psP) mimicking true progression (tP) is well known in this context. Early accurate diagnosis of tP versus psP is essential to optimise treatment strategies and improve outcome. This pilot study aims to evaluate the use of dynamic susceptibility (DSC-) MRI for differentiating between tP and psP by measuring cerebral blood volume (CBV). METHOD: Data were analysed from 5 patients who underwent MRI scans on a Siemens 3T scanner, including DSC-MRI (temporal resolution 2.1 s; injection of 0.1 mmol/kg Gadovist at 6 ml/s) and post-contrast T1-weighted scans at short intervals following surgery and chemo-radiotherapy for GBM. CE marked software (Olea Sphere) was used to obtain CBV maps with correction for T1 effects. Regions of interest were defined to calculate rCBV, the ratio of CBV in the lesion to that in normal contralateral tissue. RESULTS: Maximum rCBV varied widely across patients (mean ± standard deviation: 2.7 ± 2.0). Using a threshold of 1.8 from the literature 2 patients had hypo-perfused lesions suggesting psP and 3 patients had hyper-perfused lesions indicating tP. These findings will be correlated with follow-up scans and clinical data. CONCLUSION: This study confirms feasibility of measuring rCBV in patients undergoing treatment for GBM within a clinical workflow. Follow-up analysis will test the hypothesis that values of rCBV greater than 1.8 are indicative of tP.