Radioprotection 60-3 | Page 81

M. Jabari: Radioprotection 2025, 60( 3), 277 – 284 281

Table 5. S-values( mGy / MBq. s) for 177 Lu-DOTATATE & 90 Y-DOTATATE for BMI 28.4 of male ICRP phantom Source organs

Bladder

Kidney

Spleen

Liver

Target organs

Table 6. S-values( mGy / MBq. s) for 177 Lu-DOTATATE & 90 Y-DOTATATE for BMI 29.3 of male ICRP phantom Source organs

Target organs

organs according MIRD formalism and 90 Y-DOTATATE and 177 Lu-DOTATATE biodistribution( Alnaaimi et al., 2021).

They showed that for both target and self-absorption, S-values are notably reduced when 90 Y-DOTATATE is substituted by 177 Lu-DOTATATE. Their results are in agreement with the

trend of our results. Having effective half-life of 177 Lu and 90 Y, rough estimation of absorbed dose( in Gy) in target organs can be provided for physicians and this also help them to decide how much of activity should be injected according to the patient’ s BMI( Veress et al., 2010) and the therapeutic or imaging objectives. Ahmadzadehfar et al. emphasized that DOTATATE-based radiopharmaceuticals is a molecular target with diagnostic and therapeutic agent simultaneously( Ahmadzadehfar et al., 2015), and reported that clinical study with 177 Lu-DOTATATE has demonstrated very effective results and was well tolerated. This point comes to more attention in our study when deciding for assessment of absorbed dose ratio for Lu-177 therapy � as a promising new therapeutic agent. The results for different BMIs, demonstrate that using 177 Lu-DOTATATE has less hazards compared to 90 Y-DOTATATE. Because 177 Lu-DOTATATE can detect

lesions even more precisely, its lower S-values in target organs pose another reason for bias towards 90 Y-DOTATATE. The major drawback of the current study is the lack of simulation with real patient’ s data. There are subtle variations between biodistribution of different derivatives of DOTA- TATE-based ligands. The small differences between various derivatives of DOTATAE-based agents cannot be assessed in phantom studies. This will be of more focus in our future work on real patients. For instance, there is a slight difference