Reproducibility of total choline/water ratios in mouse U87MG xenograft tumors by ¹H‐MRS

Abstract

Purpose: To evaluate the reproducibility of the measurement of the total choline-to-water ratio, and the effect of repositioning the subject between scans, using 1 H-magnetic resonance spectroscopy in a mouse U87MG xenograft model. Materials and Methods:In vivo single-voxel MR spectra at 7T from xenograft tumors were obtained using both a water-suppressed and a nonwater-suppressed pointresolved spectroscopy (PRESS) sequence. Reproducibility of the total choline/water ratio was evaluated under the conditions of immediate rescan with no change in position of the animal or voxel, immediate reposition, and reposition after 1 or 7 days.Results: Total choline-to-water ratios in U87MG tumor xenografts averaged %0.018 across all of the groups. The average percent difference between the two scans in each condition was always less than %3.0%, and the coefficient of variation was always less than %12%. Bias was unrelated to the testing condition and relatively negligible in magnitude (<3%). Due to heteroscedasticity in the ratios, the limits of agreement were calculated after log transformation of the data and ranged from %12% when animals were maintained in the same position and immediately rescanned to %52% when the two scans were 7 days apart. Conclusion:The total choline-to-water ratio provides a reproducible measure of choline-containing metabolites in subcutaneous U87MG xenograft tumors in mice.

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“…Other metabolites that are also studied include creatine, inositol, and glucose, N‐acetylaspartate and alanine . Zhu et al reported a correlation in the reduction in peak values of Cho with tumor regression …”