NIMG-19. T1- AND T2-RELAXOMETRY FOR TISSUE CELL DENSITY QUANTIFICATION IN GLIOMA IMAGING: EXPLORATORY STUDY VIA 11C-METHIONINE PET AND VALIDATION VIA STEREOTACTIC TISSUE SAMPLING

• Published in: Neuro-oncology (Charlottesville, Va.) Vol. 21; no. Supplement_6; p. vi165
• Main Authors: Kinoshita, Manabu, Uchikoshi, Masato, Tateishi, Souichiro, Miyazaki, Shohei, Sakai, Mio, Ozaki, Tomohiko, Asai, Katsunori, Fujita, Yuya, Matsuhashi, Takahiro, Kanemura, Yonehiro, Shimosegawa, Eku, Hatazawa, Jun, Nakatsuka, Shinichi, Kishima, Haruhiko, Nakanishi, Katsuyuki
• Format: Journal Article
• Language: English
• Published: US Oxford University Press 11.11.2019
• Subjects: Neuro-Imaging
• ISSN: 1522-8517; 1523-5866
• DOI: 10.1093/neuonc/noz175.691

Abstract Visualization of non-contrast-enhancing tumor lesions in glioma is one of the most crucial yet challenging issues for patients with this pathology. This study examined the hypothesis that quantitative T1- and T2-relaxometry could reflect glioma tumor load within the brain and could further be used for visualizing non-enhancing heavily tumor-loaded areas. Participants comprised patients with low- or high-grade glioma. Correlation between T1- or T2-relaxation time and 11C-methionine uptake as measured by positron emission tomography (Cohort-1) was investigated followed by comparing T1- or T2-relaxation time with tumor cell density as measured by stereotactic image-guided tissue sampling in a different cohort (Cohort-2). T1-relaxometry was achieved by converting Magnetization Prepared Rapid Gradient Echo (MP2RAGE) images and T2-relaxometry by multi-echo T2-weighted images via Bayesian inference modeling. T1-relaxation time >2000 ms but < 3200 ms or T2-relaxation time >115 ms but < 265 ms were indicative of high 11C-methionine uptake. Stereotactic tissue sampling study confirmed that tissue cell densities obtained from locations with a T1-relaxation time of 2000–3200 ms or a T2-relaxation time of 125–225 ms were significantly higher than those obtained from other locations (p < 0.001 and p = 0.03, respectively). Synthetic tumor load images were successfully reconstructed using T1- and T2-relaxation mapping. T1- and T2-relaxation times both correlated well with tumor cell density in glioma tissues. The ideal ranges for identifying high tumor load tissues were 2000–3200 ms for T1-relaxation time and 115–220 ms for T2-relaxation both measured at 3.0 T.