TH‐C‐217BCD‐02: Ultrasound Texture Analysis of Radiation‐Induced Parotid‐Gland Injury in Post‐Radiotherapy Head‐And‐Neck Patients: Feasibility Study

Abstract

Purpose: Xerostomia (dry mouth), resulting from radiation damage to the parotid glands, is one of the most common and distressing side effects of head‐and‐neck cancer radiotherapy. We have developed a family of sonographic texture features to evaluate the morphologic and microstructural integrity of the parotid glands, and investigate the feasibility of quantitative evaluation of radiotherapy‐induced parotid‐gland injury. Methods: In this pilot study, 12 post‐radiotherapy head‐and‐neck cancer patients and 7 healthy volunteers were enrolled. Each participant underwent one ultrasound study, and longitudinal (vertical) ultrasound scans were performed of the bilateral parotids. The averaged follow‐up time for the post‐radiotherapy patients was 17.2 months and the median radiation dose was 32.3 Gy. Eight grey level co‐occurrence matrix (GLCM) features were derived from the B‐mode images. The associated parameters for texture features can be summarized as follows: 1. Inverse differential moment (IDM): local homogeneity; 2. Contrast: difference of gray‐scale through continuous pixels of the image; 3. Angular second moment (ASM): homogenous texture; 4. Entropy: disorder of the image. 5. Variance: heterogeneity; 6. Correlation: linear relationship between the gray‐scale of pixel pairs; 7. Cluster shade and 8. Cluster prominence: the perceptual concepts of uniformity and proximity. Results: Significant differences (p<0.05) were observed in 8 sonographic features, between normal and irradiated parotid glands. IDM value decreased from 7.88±1.14E‐2 (normal) to 6.93±1.54E‐2 (irradiated); Contrast value increased from 3.41±1.11E+2 to 8.45±3.46E+2; ASM value decreased from 6.06±1.72E‐4 to 3.02±0.87E‐4; Entropy value increased from 7.66±0.34 to 8.47±0.23; Variance value increased from 2.84±1.01E+2 to 9.30±3.53E+2; Correlation value decreased from 1.35±0.45E‐3 to 6.22±2.09E‐4; Cluster shade value increased from 1.20±1.24E+4 to 1.51±1.27E+5; Cluster prominence value increased from 3.11±2.50E+6 to 3.74±3.11E+7. Conclusions: This work has demonstrated the feasibility of ultrasonic texture evaluations of the parotid glands, and the sonographic features may serve as imaging signatures to assess radiation‐induced parotid damage.