Abstract
Until recently, the radiation dose to patients undergoing the 90Y selective internal radiation treatment (SIRT) procedure is determined by applying the partition model to 99mTc MAA pretreatment scan. There can be great uncertainty in radiation dose calculated from this approach and we presented a method to compute the 3D dose distributions resulting from 90Y SIRT based on 90Y positron emission tomography (PET) imaging. Five 90Y SIRT treatments were retrospectively analyzed. After 90Y SIRT, patients had 90Y PET/CT imaging within 6 hours of the procedure. To obtain the 3D dose distribution of the patients, their respective 90Y PET images were convolved with a Monte Carlo generated voxel dose kernel. The sensitivity of the PET/CT scanner for 90Y was determined through phantom studies. The 3D dose distributions were then presented in DICOM RT dose format. By applying the linear quadratic model to the dose data, we derived the biologically effective dose and dose equivalent to 2 Gy/fraction delivery, taking into account the spatial and temporal dose rate variations specific for SIRT. Based on this data, we intend to infer tumor control probability and risk of radiation induced liver injury from SIRT by comparison with established dose limits. For the five cases, the mean dose to target ranged from 51.7 ± 28.6Gy to 163 ± 53.7 Gy. Due to the inhomogeneous nature of the dose distribution, the GTVs were not covered adequately, leading to very low values of tumor control probability. The mean dose to the normal liver ranged from 21.4 ± 30.7 to 36.7 ± 25.9 Gy. According to QUANTEC recommendation, a patient with primary liver cancer and a patient with metastatic liver cancer has more than 5% risk of radiotherapy‐induced liver disease (RILD).PACS number: 87.53.Bn
Highlights
Selective Internal Radiation Treatment (SIRT) is the delivery of radiation treatment via intrahepatic arterial administration of 90Y microspheres. 90Y SIRT is an emerging modality in the management of patients with inoperable primary and metastatic liver cancer
The radiation dose for the SIRT procedure was estimated by the partition method based on pretreatment 99mTc MAA diagnostic angiogram.[2,3] there are great uncertainties associated with this approach
We presented a method of patient dosimetry for the SIRT procedure based on 90Y positron emission tomography (PET)/CT imaging which is practicable in a clinical setting. 90Y PET is a reliable method for the assessment of SIR-Sphere distribution with superior image quality compared to 90Y Bremstrahlung scan
Summary
Selective Internal Radiation Treatment (SIRT) is the delivery of radiation treatment via intrahepatic arterial administration of 90Y microspheres. 90Y SIRT is an emerging modality in the management of patients with inoperable primary and metastatic liver cancer. 90Y SIRT is an emerging modality in the management of patients with inoperable primary and metastatic liver cancer. It is based on the unique pattern of hepatic blood flow by which the majority of the tumor blood supply is derived from the hepatic artery, whereas hepatic parenchymal blood flow largely comes from the portal vein. The spatial and temporal variations of dose rate will have different radiobiological effect on the tumor and normal tissues. The partition method assumes a uniform distribution of 90Y microsphere, disregarding the spatial and temporal variation of the dose and dose rate. The radiobiological effects specific to SIRT are ignored, and the partition method is at best a simplified picture for the patient dosimetry. The radiobiological effects specific to SIRT are ignored, and the partition method is at best a simplified picture for the patient dosimetry. 90Y has an internal pair production component with a branching ratio of 31.87 ± 0.47 × 10-6.(4)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
