Purpose: To investigate the value of in vivo proton (H) magnetic resonance spectroscopy (MRS) in longitudinally monitoring the treatment response of malignant musculoskeletal tumors under chemotherapy.
Materials and methods: Twenty-three studies in 3 patients with bone and soft-tissue tumors (2 lymphomas and 1 alveolar soft part sarcoma) were included in the study. The dynamic contrast-enhanced magnetic resonance (MR) imaging and single-voxel proton MRS with 135 milliseconds of echo time were carried out using a whole-body 1.5-T scanner and a surface coil. The volume of interest within the lesion was positioned on the area of early enhancement according to the finding of the first dynamic contrast-enhanced MR imaging with subtraction. The choline and water intensities were measured at the peak areas at 3.2 and 4.5 ppm. The choline-water ratios were calculated as well. Statistical analysis was performed by using Kruskal-Wallis 1-way analysis of variance test ().(Table is included in full-text article.)
Results: The changes observed on the dynamic contrast-enhanced MR images and tumor size after chemotherapy fell into 2 clearly distinct patterns: subsequent partial response (patients 1 and 2) and progressive disease (patient 3). The choline concentration, choline-volume ratio, and choline-water ratio in the first 2 patients were reduced substantially to zero in the follow-up MRS. In the remaining patient, the choline, choline-volume ratio, and choline-water ratio remained high in the follow-up MRS. The water concentration and water-volume ratio between the 3 patients showed significant statistical differences (Kruskal-Wallis test, P = 0.004 and 0.039).
Conclusion: In vivo proton MRS is technically feasible for the evaluation of musculoskeletal tumors. Choline can be detected in malignant bone and soft-tissue tumors, and the early metabolite changes after chemotherapy can also be identified in the in vivo proton MRS by using a standard clinical-use 1.5-T MR scanner and a surface coil. The decline of choline after treatment in malignant bone and soft-tissue tumors correlates with the response of the dynamic contrast MR images and the tumor size. The information provided with MR imaging and proton MRS may improve the diagnostic specificity of MR examination in the follow-up of tumor treatment.