Prediction of tumor radiation absorbed dose in radionuclide therapy based on the mean standardized uptake value from PET imaging

Accurate estimation of tumor absorbed dose is essential for effective disease control in radionuclide therapy, but routine dosimetry is often limited by the need for multiple posttherapy imaging acquisitions. This study aimed to develop a simplified method to predict tumor absorbed doses in radionuclide therapy using pretherapy PET standardized uptake value (SUV) measurements. Tumor absorbed doses were estimated using the medical internal radiation dose formalism, PET SUV _mean , and radionuclide physical and effective half-lives, assuming comparable tumor uptake between diagnostic and therapeutic radiopharmaceuticals. A mathematical equation was derived to facilitate tumor dose estimation. For representative clinically administered activities, tumor absorbed doses per unit SUV _mean were 1.84 ± 0.22, 1.07 ± 0.13, 0.58 ± 0.07, and 0.10 ± 0.01 Gy for the ⁶⁸ Ga/ ⁹⁰ Y, ¹²⁴ I/ ¹³¹ I, 68Ga/ ¹⁷⁷ Lu, and ⁶⁸ Ga/ ²²⁵ Ac theranostic pairs, respectively. Tumor absorbed dose estimation showed a strong dependence on SUV _mean and effective half-life, with good agreement between estimated values and previously reported dosimetric results. Although this simplified model does not replace full patient-specific dosimetry, it may provide a practical approach for pretherapy dose prediction. Further studies are required to validate and refine the proposed model.