Author: Jiahao Chen, Yunwen Huang, Yidong Yang, Shanshan Zhang, Ning Zhao, Cheng Zheng 👨🔬
Affiliation: Department of Life Sciences and Medicine, University of Science and Technology of China, Department of Engineering and Applied Physics, University of Science and Technology of China, University of Science and Technology of China 🌍
Purpose: To develop a molecular image-guided radiotherapy technique for accurate and effective radiation treatment using quantitative fluorescence molecular tomography (FMT).
Methods: X-ray cone beam computed tomography (CBCT) and FMT were integrated on the image guided SMall Animal Arc Radiation Treatment platform (iSMAART). For the tumor model, 1x106 HCT116 cells were labeled with fluorescent protein mCherry and inoculated into the bilateral abdomen to develop subcutaneous colorectal tumors. CBCT was first performed to obtain the animal anatomy and to generate a 3D mesh for the FMT reconstruction. The fluorescence projections were then captured every 30° rotation and used in the FMT reconstruction. The tumor contoured in the CBCT was used as the ground truth to validate the gross tumor volume (GTV) reconstructed by FMT. The FMT planning target volume (PTV) for radiation guidance was determined by an expansion of the GTV reconstructed by FMT to account for the tumor location and volume uncertainty.
Results: FMT can reconstruct the subcutaneous tumors in vivo with a localization accuracy less than 1.00mm. A significant correlation was found between the tumor volumes reconstructed by FMT and manually contoured in CBCT (R2=0.89, P<0.0001). There was also a significant correlation in the tumor diameters between FMT and CBCT (R2=0.75, P<0.0001). A 0.90mm margin expansion was determined to increase the tumor coverage rate from 77.1% to 99.4%.
Conclusion: The dual-modality CBCT/FMT system is able to accurately detect and quantify the tumor volume. With the quantitative molecular imaging capability, FMT can provide a useful tool for image guidance and treatment response evaluation in case CBCT cannot delineate the tumor due to its lack of soft tissue contrast.