2D 1H sLASER Long-TE and 3D 31P Chemical Shift Imaging at 3 T for Monitoring Fasting-Induced Changes in Brain Tumor Tissue

BackgroundEmerging evidence suggests that fasting could play a key role in cancer treatment. Its metabolic effects on gliomas require further investigation. PurposeTo design a multi-voxel H-1/P-31 MR-spectroscopic imaging (MRSI) protocol for noninvasive metabolic monitoring of cerebral, fasting-induced changes on an individual patient/tumor level, and to assess its technical reliability/reproducibility. Study TypeProspective. PopulationMRS phantom. Twenty-two patients (mean age = 61, 6 female) with suspected WHO grade II-IV glioma examined before and after 72-hour-fasting prior to biopsy/resection. Field Strength/Sequence3-T, H-1 decoupled 3D 31P MRSI, 2D H-1 sLASER MRSI at an echo time of 144 msec, 2D H-1 MRSI (as water reference), T1-weighted, T1-weighted contrast-enhanced, T2-weighted, and FLAIR. sLASER and PRESS sequences were used for phantom measurements. AssessmentPhantom measurements and spectral simulations were performed with various echo-times for protocol optimization. In vivo spectral analyses were conducted using LCModel and AMARES, obtaining quality/fitting parameters (linewidth, signal-to-noise-ratio, and uncertainty measures of fitting) and metabolite intensities. The volume of glioma sub-regions was calculated and correlated with MRS findings. Ex-vivo spectra of necrotic tumor tissues were obtained using high-resolution magic-angle spinning (HR-MAS) technique. Statistical TestsWilcoxon signed-rank test, Bland-Altman plots, and coefficient of variation were used for repeatability analysis of quality/fitting parameters and metabolite concentrations. Spearman rho correlation for the concentration of ketone bodies with volumes of glioma sub-regions was determined. A P-value <0.05 was considered statistically significant. Results H-1 and P-31 repeatability measures were highly consistent between the two sessions. beta-hydroxybutyrate and acetoacetate were detectable (fitting-uncertainty <50%) in glioma sub-regions of all patients who completed the 72-hour-fasting cycle. beta-hydroxybutyrate accumulation was significantly correlated with the necrotic/non-enhancing tumor core volume (rho = 0.81) and validated using ex-vivo H-1 HR-MAS. Data ConclusionWe propose a comprehensive MRS protocol that may be used for monitoring cerebral, fasting-induced changes in patients with glioma. Evidence Level1 Technical EfficacyStage 4