Quantitative proton MR spectroscopy as a biomarker of tumor necrosis in the rabbit VX2 liver tumor

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, 1222 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.