Evaluation of the Repeatability and Reproducibility of Radiomic Features of Non-Irradiated Organs Utilizing Fan-Beam KVCT

Purpose: Although radiation oncologists obtain non-contrast computed tomography (CT) images every treatment, their quality is often insufficient for radiomic analyses for monitoring response over treatment. Newer imaging utilizing fan-beam KVCT have higher-quality imaging, creating opportunities for radiomic analysis over the course of treatment. To best utilize the high-quality scans for radiomic analyses of cancerous tissue, radiomic features that remain consistent through treatment in normal organs must first be identified. Stable features can be used for normalization to calculate radiomic features in tumors, enabling monitoring of response during treatment and early adaptation if required.

Methods/Materials: A total of five patients were scanned using the RefleXion X1 throughout treatment. CT scans used standardized acquisition parameters for all treatments to minimize variation. Images were acquired using “Body/Medium Dose/Slow Couch” parameters. The regions of interest (ROIs) for each organ were automatically segmented using an auto-segmentation system. CTs and structure files were imported into an Image Biomarker Standardization Initiative (IBSI) compliant radiomic software package (LifeX) to extract radiomic features. Four non-irradiated organs were used to analyze repeatability of normal tissues: Liver, Spleen, Heart, and Spinal Cord. The intraclass correlation coefficient (ICC) using a 2-way mixed-effects model was used to measure repeatability while concordance correlation coefficient (CCC) was used to measure reproducibility.

Results: Cutoff values were applied to the average ICC across patients and average CCC across both patients and fractions. 40 features were identified with a cutoff value of 0.8, accounting for 82% of the original features. Using a cutoff value of 0.9 the subset of stable features were further reduced to 29, representing 59% of the original features.

Conclusions: A subset of radiomic features extracted remained stable throughout treatment. Thus, radiomic analyses of cancerous tissue using fan-beam KVCT over the course of treatment would be feasible as an ongoing assessment of response during treatment for personalized adaptive approaches.