Dynamic contrast-enhanced magnetic resonance imaging in radiotherapeutic efficacy in the head and neck tumors

The purpose to this study is to identify correlations between pathology and dynamic contrast-enhanced magnetic resonance imaging (MRI) and to assess the utility of this technique in the evaluation of radiation response for head and neck cancer. MRI was prospectively performed after radiotherapy in 27 patients with various head and neck tumors. After bolus injection of contrast material, a dynamic study was performed using a spoiled gradient–recalled imaging sequence. The maximum slope of increase (MSI) on the time-intensity curve was displayed as a color-coded image. The ratio of MSI (MSIR) was obtained for tumor and normal muscles. Pathological specimens were obtained after MRI in all cases. Histological grading of irradiation changes was classified into 5 grades (0–4). Correlations between MSIR and histological grade were examined. Histologically, 18 tumors were classified as grade 2 (presence of viable tumor cells), 4 were grade 3 (nonviable tumor cells), and 5 were grade 4 (no tumor cells). Although the mean ± SD of MSIR in patients with histological grade 2 or 3 was 7.4 ± 7.9, MSIR in patients with grade 4 was 1.8 ± 0.73, representing a significant difference ( P < .05). Every patient with grade 4 displayed an MSIR of 2.5 or less, although 5 of 22 patients with grade 2 or 3 had an MSIR of 2.5 or less. MSI quantitatively reflects response to radiotherapy for head and neck cancer. Color-coded MSI display is feasible for depicting permeability changes after radiotherapy.