Size-dependent dose estimation applied to

Purpose: Radiolabeled peptide has attracted growing interests for neuroendocrine cancer therapy. We aim to calculate S-values of Lu-177, nd Y-90 in different size of International commission of radiation protection (ICRP) male and female phantoms for pre-estimation of absorbed dose in critical target organs using Monte Carlo simulation to see the extent of difference. Materials and methods: We employed the most advanced hybrid ICRP phantom and used its different male MIs to resemble reality. Six different size of ICRP malephantoms were generated. GATE code was used to perform dosimetry calculations. Spline, bladder, kidneys, and liver were chosen as the source organs and the S- values were calculated in interested target organs for twenty different body mass indexes (BMIs). Results: The S-values in both self-absorptions and target organs were statistically ower for 177Lu-DOTATATE compared to 90Y-DOTATATE. The highest difference between the absorption in kidneys is for BMI of 24.3. The highest S-value in bladder from bladder is 0.01 mGy/MBq.s in BMI of 34.4 for 177Lu-DOTATATE, whereas it is 0.0049 mGy/MBq.s in BMIs of 34.4 for 90Y-DOTATATE. It was found that dose per unit cumulated activity had a tendency to decrease with BMI. Conclusion: Variability in 177Lu-DOTATATE and 90Y-DOTATATE dosimetry across morphometrically different patients are important in optimizing therapy protocols and research studies. Using size-dependent phantoms for dosimetry, more accurate dose estimations per cumulated activity relative to standard reference dosimetry are obtained. To prevent excessive dosage to patients, it is important to consider the relationship between body size and dose.