Radioprotection 2025, 60( 3), 277 – 284 © M. Jabari, Published by EDP Sciences 2025 https:// doi. org / 10.1051 / radiopro / 2025005
Available online at: www. radioprotection. org
ARTICLE
Size-dependent dose estimation applied to 177 Lu and 90 Y-DOTATATE using ICRP Phantoms
M. Jabari * Department of Radiology Technology, Faculty of Allied Medical Sciences, Birjand University of Medical Sciences, Birjand, Iran. Received: 3 April 2024 / Accepted: 31 January 2025
Abstract – 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 selfabsorptions and target organs were statistically ower for 177 Lu-DOTATATE compared to 90 Y-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 177 Lu-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 177 Lu-DOTATATE and 90 Y-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.
Keywords: Internal dosimetry / Phantom / Monte Carlo
1 Introduction
Peptide receptor radionuclide therapy( PRRT) is an important class of systemic treatment of patients with unrespectable or metastasized neuro-endocrine tumors( NETs). Radiolabeled somatostatin analogs such 177 Lu-DOTATATE( DOTA is 1,4,7,10-tetraazadodecane-N, N _, N _, N _-tetraacetic acid) and 90 Y-DOTATATE are most successful in detecting, imaging and therapy of tumors expressing somatostatin receptors( Mittra, 2018; Delpassand et al., 2014). Localization of these radiopharmaceuticals after ligand binding makes them a favorable target for therapy( Sandström et al., 2018; Lassmann et al., 2021). Radiolabeled peptides are excreted mainly via the kidneys and are partly reabsorbed in the proximal tubular cells. Therefore retention and excretion of these molecules from urine pathway may cause toxicity due to highbsorbed dose to critical organs such as kidney, liver and bladder. This toxicity precludes the use of higher doses, thus limiting the efficacy of therapy.
* Corresponding author: masoudjabari @ yahoo. com
Internal dosimetry is an outstanding procedure in nuclear medicine to optimize both diagnostic and therapeutic procedures( Carneiro et al., 2015; Potter, 2024) and the resulting dose to the patient( Bertho and Bourguignon, 2024). Pre-estimation of absorbed dose in critical target organs can be performed by atlas-based simulations using advanced anthropomorphic phantoms and Monte Carlo codes( Panta, et al. 2012). The ICRP developed reference computational phantoms in mesh format to provide anatomically more realistic representations of the human body. These advanced phantoms define numerous source and target regions with different size( mass and height) providing more similarity to real conditions. Furthermore, the results obtained from dosimetry simulations may help to extract approximate values of absorbed dose in different organs and optimize the selection of radionuclide. 90 Y and 177 Lu are two commonly used radionuclides in
therapy of neuro-endocrine tumors( Seregni et al., 2014; Zemczak et al., 2021). Based on the previous literature, 177 Lu and 90 Y have low and high energy beta particles, respectively. According to the range of beta particles emitted from each of these two radionuclides, they are widely used for treating
This is an Open Access article distributed under the terms of the Creative Commons Attribution License( https:// creativecommons. org / licenses / by / 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.