Applied Sciences (Jan 2024)

The Role of Lung Density in the Voxel-Based Dosimetry of <sup>90</sup>Y-TARE Evaluated with the Voxel S-Value (VSV) Method and Fast Monte Carlo Simulation

  • Amedeo Capotosti,
  • Roberto Moretti,
  • Maria Vaccaro,
  • Cintia De Almeida Ribeiro,
  • Lorenzo Placidi,
  • Matteo Nardini,
  • Guenda Meffe,
  • Davide Cusumano,
  • Luca Zagaria,
  • Marina De Risi,
  • Germano Perotti,
  • Lucia Leccisotti,
  • Marco De Spirito,
  • Roberto Iezzi,
  • Luca Indovina

DOI
https://doi.org/10.3390/app14031019
Journal volume & issue
Vol. 14, no. 3
p. 1019

Abstract

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(1) Background: In 90Y-TARE treatments, lung-absorbed doses should be calculated according to the manufacturer’s instructions, using the MIRD-scheme. This scheme is derived from the assumption that 90Y-microspheres deliver the dose in a water-equivalent medium. Since the density of the lungs is quite different from that of the liver, the absorbed dose to the lungs could vary considerably, especially at the liver/lungs interface. The aim of this work is to compare the dosimetric results obtained by two dedicated software packages implementing a water-equivalent dose calculation and a Monte Carlo (MC) simulation, respectively. (2) Methods: An anthropomorphic IEC phantom and a retrospective selection of 24 patients with a diagnosis of HCC were taken into account. In the phantom study, starting from a 90Y-PET/CT acquisition, the liver cavity was manually fixed with a uniform activity concentration on PET series, while the lung compartment was manually expanded on a CT series to simulate a realistic situation in which the liver and lungs are adjacent. These steps were performed by using MIM 90Y SurePlan. Then, a first simulation was carried out with only the liver cavity filled, while a second one was carried out, in which the lung compartment was also manually fixed with a uniform activity concentration corresponding to 10% lung shunt fraction. MIM 90Y SurePlan was used to obtain Voxel S-Value (VSV) approach dose values; instead, Torch was used to obtain MC approach dose values for both the phantom and the patients. (3) Results: In the phantom study, the percentage mean dose differences (∆D%) between VSV and MC in the first and second simulation, respectively were found to be 1.2 and 0.5% (absolute dose variation, ∆D, of 0.7 and 0.3 Gy) for the liver, −56 and 70% (∆D of −0.3 and −16.2 Gy) for the lungs, and −48 and −60% (∆D of −4.3 and −16.5 Gy) for the Liver/Lungs Edge region. The patient study reports similar results with ∆D% between VSV and MC of 7.0%, 4.1% and 6.7% for the whole liver, healthy liver, and tumor, respectively, while the result was −61.2% for the left lung and −61.1% for both the right lung and lungs. (4) Conclusion: Both VSV and MC allowed accurate radiation dose estimation with small differences (50%) were observed for air-equivalent regions in the phantom simulation and the patient study.

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