Patient-Specific dosimetry of 68Ga-PSMA using GATE Monte Carlo code

Purpose: Prostate-specific membrane antigen (PSMA) has been successfully labeled to 68Ga and is used as a tracer in prostate cancer management include identification of suspected primary site, helping in PET based targeted biopsy, staging, recurrence evaluation as well as for radiotherapy planning. The patient-specific dosimetry of this agent can help to more efficiently selection of the amount of 177Lu-PSMA activity for treatment planning. In this study, we aim to calculate and report the S-values of patient underwent PET/CT imaging of 68Ga-PSMA. Method: We include 10 patients who injected 2-5 mCi 68Ga-PSMA and underwent PET/CT imaging. We used PET images as biodistribution of activity and CT images as the structural map. For coregistration and segmentation of organs and tumors, we used 3D slicer. GATE Monte Carlo simulation using GATE was selected as more accurate way for dosimetry calculation. Finally, we converted dose results obtained by GATE to numerical values, and according to MIRD schema; we reported them as S-Value. Results: The absorbed doses are the highest in metastases locations of the patients as well as their tumors. We can see that lymph nodes, prostate, and metastases in bony parts have the greatest amount of S-Value. Also, we observe that the amount of dose is high in the organs that are the normal targets in 68Ga-PSMA imaging (e.g. lacrimal and salivary glands). Conclusion: The results of 68Ga-PSMA patient-specific dosimetry may have a crucial effect of treatment planning using 177Lu-PSMA for the amount of injected activity, treatment management, and obtaining better therapy response.

کلیدواژه ها:

Patient-specific ، dosimetry ، Ga-PSMA ، GATE