rCBV and ADC based grading of gliomas with glimpse into radiogenomics

Purpose. The present study was carried out to study the role of relative cerebral blood volume (rCBV), apparent diffusion coefficient (ADC) and MR spectroscopy in grading gliomas to help the surgeon plan the approach and extent of surgery as well as judge the need for any adjuvant radio/chemotherapy. Methods. 65 patients with glioma were prospectively studied with MRI. Basic MR sequences (T1W, T2W, T2W/FLAIR) were followed by diffusion-weighted (DW) imaging with b value of 1000 (minimum ADC values used for analysis). Then the patients were administered Gadobenate Dimeglumine/ Meglumine Gadoterate in a dose of 0.1mmol/kg at a rate of 4ml/sec after which 20ml of saline was flushed at a rate of 4ml/sec and  T2*W/FFE dynamic images were acquired; dynamics showing maximum fall in the intensity were used for creating rCBV and rCBF maps and calculating rCBV. Single voxel spectroscopy (SVC) was done using the PRESS sequence with intermediate TE of 144ms. NAA/Cr, Cho/Cr, Cho/NAA, Cho+Cr/NAA and NAA/Crn ratios (NAA from the tumour, Crn from the normal side) were calculated. Results. Grade I gliomas showed minimum ADC>0.84x10-3mm2/s and maximum rCBV<1.9ml/100gm, grade II gliomas showed min ADC 0.75-0.84x10-3mm2/s and max rCBV of 1.9-2.6ml/100gm, grade III had min ADC of 0.70-0.75x10-3mm2/s and max rCBV of 2.7-3.0ml/100gm, while grade IV tumors showed min ADC<0.70x10-3mm2/s and max rCBV>3.0ml/100gm. rCBV values were better than ADC values in differentiating grade I from II and grade II from III. The ADC values were better than rCBV values in differentiating grade III from grade IV. Conclusions. Both minimum ADC and maximum rCBV within the tumour were significant but these parameters within peritumoral oedema were not significant in grading gliomas. Though lipid and lactate (especially lipid) peaks were found more frequently in higher-grade tumours, various spectroscopy parameters were not significant in grading gliomas. Preoperative grading of gliomas with the help of advanced MR parameters like ADC and rCBV can help the surgeon plan the approach and extent of surgery as well as judge the need for any adjuvant radio/chemotherapy. Advancing radio-genomic and radiomic technologies can supplement the current radiologic methods of diagnosis and prognosis. &nbsp