Patient dosimetry for 90Y selective internal radiation treatment based on 90Y PET imaging

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Until recently, the radiation dose to patients undergoing the Symbol selective internal radiation treatment (SIRT) procedure is determined by applying the partition model to Symbol 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 Symbol SIRT based on Symbol positron emission tomography (PET) imaging. Five Symbol SIRT treatments were retrospectively analyzed. After Symbol SIRT, patients had Symbol PET/CT imaging within 6 hours of the procedure. To obtain the 3D dose distribution of the patients, their respective Symbol PET images were convolved with a Monte Carlo generated voxel dose kernel. The sensitivity of the PET/CT scanner for Symbol 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 Symbol to Symbol. 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 Symbol to Symbol. 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

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