Role of diffusion-weighted magnetic resonance imaging in differentiation between the viable and necrotic parts of head and neck tumors

Abstract

Differentiation between the viable and necrotic parts of a tumor is essential for accurate biopsy results and for treatment planning. To determine the role of diffusion-weighted magnetic resonance (MR) imaging in differentiation between the viable and necrotic parts of head and neck tumors. Thirty patients with malignant head and neck tumors underwent postcontrast MR imaging. Diffusion MR imaging was done on a 1.5T unit using multislice single-shot echo-planar imaging. Diffusion-weighted MR images were acquired with a diffusion-weighted factor b of 0, 500, and 1000 s/mm(2), and an apparent diffusion coefficient (ADC) map was reconstructed. The ADC value was measured within the enhanced and nonenhanced part of the tumor, and the mean ADC values were calculated. The ADC value was correlated with biopsy results. The mean ADC value of a viable part of the tumor was 1.17+/-0.33 x 10(-3) mm(2)/s, and of the necrotic parts of the tumor 2.11+/-0.05 x 10(-3) mm(2)/s. The difference in the ADC value between the viable and necrotic parts of the head and neck tumors was statistically significant (P<0.001). Sensitivity, specificity, and accuracy of the ADC value were 92.9%, 93%, and 94.6%, respectively. Creation of an ADC map is an excellent method for differentiation between the viable and necrotic parts of head and neck tumors. Thus, the ADC map can be used to select the best biopsy site and to detect tumor viability in post-treatment follow-up of patients after radiation therapy.