Objective: The objective of this study was to evaluate whether the average apparent diffusion coefficient (ADC) or the minimum ADC is more useful for evaluating the chemotherapeutic response of osteosarcoma.
Materials and methods: Twenty-two patients with osteosarcoma were examined in this study. Diffusion-weighted (DW) and magnetic resonance (MR) images were performed for all patients before and after chemotherapy. The pre- and post-chemotherapy values were obtained both in the average and minimum ADC. The pre-chemotherapy values of the average ADC and minimum ADC respectively were compared with the post-chemotherapy values. In addition, the ADC ratios ([ADC(post) - ADC(pre)] / ADC(pre)) were calculated using the average ADC and the minimum ADC. Twenty-two patients with osteosarcomas were divided into two groups, those with a good response to chemotherapy (> or = 90% tumor necrosis, n = 7) and those with a poor response (< 90% tumor necrosis, n = 15). The average ADC ratio and the minimum ADC ratio of the two groups were compared.
Results: With both the average ADC and the minimum ADC, post-chemotherapy values were significantly higher than pre-chemotherapy values (P < 0.05). The patients with a good response had a significantly higher minimum ADC ratio than those with a poor response (1.01 + or - 0.22 and 0.55 + or - 0.29 respectively, P < 0.05). However, with regard to the average ADC ratio, no significant difference was observed between the two groups (0.66 + or - 0.18 and 0.46 + or - 0.31 respectively, P = 0.19).
Conclusion: The minimum ADC is useful for evaluating the chemotherapeutic response of osteosarcoma.