3627 - Optimization of Whole-Body Dose Calculation and Personalized Organ Shielding for TBI Using uTPS and 2m PET-CT Technology
Presenter(s)
W. Gong1, S. Qin2, and G. Gan2; 1Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Soochow, China, 2Department of Radiation Oncology, The First Affiliated Hospital of Soochow University, Suzhou, China
Purpose/Objective(s): This study aims to address the challenges in overall dose calculation for patients receiving total-body irradiation (TBI) prior to hematopoietic stem cell transplantation, utilizing the uTPS system in combination with 2m ultra-long axial PET-CT technology to achieve precise dose distribution visualization and personalized organ shielding.
Materials/Methods: Before treatment, the patient undergoes two CT scans using different protocols: head-first (HFS) and feet-first (FFS), ensuring a minimum overlap of 10 cm. The uTPS image registration algorithm detects key marker points in the overlap for pre-registration, followed by rigid registration, which stitches the two CT datasets to generate whole-body CT images. These images are then imported into uTPS, where a dose calculation algorithm determines the dose distribution. The system automatically contours lead shielding to protect organs at risk. The integration of 2m PET-CT data further enhances dose calculation accuracy by providing metabolic images from PET and anatomical images from CT, enabling more precise tumor and organ localization. The dose distribution is optimized to meet prescription requirements, and information on shielding design—including shape, thickness, and location—is generated.
Results: The combination of the uRT-linac 506c and 2m ultra-long axial PET-CT proved to be a powerful tool in achieving accurate registration and seamless stitching of whole-body CT images. The integration of 2m PET-CT significantly enhanced organ localization and metabolic data precision, enabling a more accurate assessment of tumor and organ metabolic activity. This improvement directly contributed to the precise planning of dose distribution, with accuracy maintained within 5% in accordance with TBI treatment prescriptions. The superior metabolic imaging capabilities of 2m PET-CT were crucial in identifying high-risk areas for personalized shielding. As a result, tailored lead shielding for critical organs, such as the lungs, ovaries, and testes, was effectively designed and incorporated into the treatment plan, ensuring optimal organ protection.
Conclusion: Traditional TBI treatment in our institution relies on solid water point dose measurements, which are limited in fully assessing dose distribution, especially beyond the measurement points. To address this, the uTPS system with the ultra-long SSD convolution dose algorithm enables accurate modeling of clinical treatment machines and support structures. The integration of 2m PET-CT provides high-resolution metabolic imaging, improving tumor localization and dose distribution accuracy. Additionally, image registration and stitching overcome the scan length limitations of simulation CT scanners, enabling complete whole-body images. Compared to fixed-size lead shields in traditional TBI treatments, personalized shielding based on uTPS and 2m PET-CT offers enhanced protection and treatment precision.