Post-RT Head and Neck DCE-MRI: Association Between Mandibular Dose and v_e

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a functional imaging modality that can quantify tissue permeability and blood flow. Due to vasculature changes resulting from radiation therapy (RT), DCE-MRI quantitative parameters should be significantly different in regions receiving a high radiation dose compared to regions receiving a low radiation dose. This study sought to determine whether a significant difference exists in post-head-and-neck-cancer (HNC)-RT DCE-MRI quantitative parameters (K^trans and v_e) between regions of the mandible receiving a high radiation dose and regions of the mandible receiving a low radiation dose.

DCE-MRI was acquired from HNC subjects post-RT. The DCE-MRI quantitative parameters K^trans and v_e were obtained through Tofts model fitting. Four mandible sections (left ramus, left body, right ramus, and right body) were delineated on subject mandible contours. Two Friedman tests comparing the mean K^trans and v_e in low-dose (≤60 Gy) areas of the four mandible regions were computed. If the Friedman test determined that a significant difference for a parameter between mandible regions exists, post hoc Wilcoxon signed-rank tests were completed comparing the four mandible regions. If the Friedman test determined that there was no significant difference between mandible regions, a Wilcoxon signed-rank test was used to determine whether a significant difference exists in the parameter between high-dose (>60 Gy) and low-dose (≤60 Gy) mandible regions.

48 HNC subjects were included in the analysis. The Friedman tests showed no significant difference in v_e means between mandible regions (χ(3)2 = 1.63, p = 0.44) and a significant difference in K^trans means between mandible regions (χ(3)2 = 10.29, p = 0.005). Post hoc testing between K^trans mandible regions found that the left body and right body differed significantly from the left ramus and right ramus. The Wilcoxon signed-rank test comparing the mean v_e between high- and low-dose mandible regions found a significant difference (W = 214, p = 0.00013).

no inherent difference in the DCE-MRI quantitative parameter v_e was observed within subject mandibles, but a significant difference was observed between v_e means in high- and low-radiation-dose mandible regions. These results provide evidence of the utility of DCE-MRI to monitor mandible vasculature changes resulting from head and neck cancer radiation therapy. Monitoring post-HNC-RT mandible vasculature changes is important to initiate earlier toxicity management and ultimately improve HNC survivors' quality of life.