Quantitative Proton MR Spectroscopy as a Biomarker of Tumor Necrosis in the Rabbit VX2 Liver Tumor

Abstract

Purpose To compare metabolic magnetic resonance (MR) imaging findings (ie, quantification of tumor choline concentration) with percentage of necrosis on pathologic examination in rabbits bearing VX2 liver tumors. Materials and Methods VX2 tumors were implanted in the livers of 16 rabbits. MR imaging was performed with a 1.5-T MR scanner and extremity coil, and a hydrogen-1 ( 1H) proton MR spectroscopy ( 1H MRS) imaging protocol was used. Rabbits were euthanized immediately after imaging, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. Choline concentration was calculated and was compared with the percentage of tumor necrosis on pathologic examination. Results Mean tumor size at pathologic examination was 16 mm (range, 12–22 mm). Mean percentage of necrosis at pathologic examination was 22% (range, 4%–44%). Choline concentration showed a relatively high inverse correlation with percentage of necrosis on pathologic examination, with an r value of 0.78 ( P < .002). Conclusions Choline concentration showed a relatively high inverse correlation with tumor necrosis on pathologic examination. Therefore, 1H MRS may be useful to assess tumor necrosis.