Systematic investigation on the validity of partition model dosimetry for⁹⁰Y radioembolization using Monte Carlo simulation

Abstract

We aimed to investigate the validity of the partition model (PM) in estimating the absorbed doses to liver tumour ([Formula: see text]), normal liver tissue ([Formula: see text]) and lungs ([Formula: see text]), when cross-fire irradiations between these compartments are being considered. MIRD-5 phantom incorporated with various treatment parameters, i.e. tumour involvement (TI), tumour-to-normal liver uptake ratio (T/N) and lung shunting (LS), were simulated using the Geant4 Monte Carlo (MC) toolkit. 10 track histories were generated for each combination of the three parameters to obtain the absorbed dose per activity uptake in each compartment ([Formula: see text], [Formula: see text], and [Formula: see text]). The administered activities, A were estimated using PM, so as to achieve either limiting doses to normal liver, [Formula: see text] or lungs, [Formula: see text] (70 or 30 Gy, respectively). Using these administered activities, the activity uptake in each compartment ([Formula: see text], [Formula: see text], and [Formula: see text]) was estimated and multiplied with the absorbed dose per activity uptake attained using the MC simulations, to obtain the actual dose received by each compartment. PM overestimated [Formula: see text] by 11.7% in all cases, due to the escaped particles from the lungs. [Formula: see text] and [Formula: see text] by MC were largely affected by T/N, which were not considered by PM due to cross-fire exclusion at the tumour-normal liver boundary. These have resulted in the overestimation of [Formula: see text] by up to 8% and underestimation of [Formula: see text] by as high as -78%, by PM. When [Formula: see text] was estimated via PM, the MC simulations showed significantly higher [Formula: see text] for cases with higher T/N, and LS ⩽ 10%. All [Formula: see text] and [Formula: see text] by MC were overestimated by PM, thus [Formula: see text] were never exceeded. PM leads to inaccurate dose estimations due to the exclusion of cross-fire irradiation, i.e. between the tumour and normal liver tissue. Caution should be taken for cases with higher TI and T/N, and lower LS, as they contribute to major underestimation of [Formula: see text]. For [Formula: see text], a different correction factor for dose calculation may be used for improved accuracy.

Utilizing 3D Slicer to incorporate tomographic images into GATE Monte Carlo simulation for personalized dosimetry in yttrium‐90 radioembolization

“…The reason behind these discrepancies could be due to the simplification of PM estimation, where cross-fire irradiations between volumes were not considered. 10 Thus, from the MC simulation,it has been demonstrated that there are presence of beta radiations escaping from the regions where the 90 Y sources are deposited. This is supported by the isodose distribution as shown in Figure 17.…”

“…A minimum of 1.0 × 10 7 histories should be generated in each simulation and repeated three times to ensure a statistical uncertainty of less than 1%. 10,[22][23][24][25][26] This is a common practice with Geant4 (or GATE) simulation, in which uncertainty of less than 1% is considered acceptable, as further reduction on the uncertainty (may be achieved by increasing the number of histories) comes with the cost of increased computational time, and that in most cases, lower uncertainty may not be achievable as MC simulation heavily rely on random events.…”

“…However, this has been proven inaccurate by an earlier study. 10 Further, as the size and distributions of tumor are unique for each patient, the anatomical differences and tissue inhomogeneity should also be taken into consideration. 11 3D Slicer 12 is a free open-source software for image analysis and visualization.…”

Pre- and post-treatment image-based dosimetry in 90Y-microsphere radioembolization using the TOPAS Monte Carlo toolkit

“…In this specific instance, a left-sided tumor included in the 99m Tc-MAA injection was not treated with 90 Y during this session. Overall, these results also demonstrate the necessity of using voxel-based dosimetry instead of compartmental models for 90 Y-microsphere radioembolization as distributions of activity are far from being uniform in liver sub-regions [ 50 ].…”

Biokinetic Model Development of 177Lu-labeled Methylene Diphosphonate as a Radiopharmaceutical Treatment

“…Charged particles resulting from the collapse of these radionuclides possess high energy with a short run-in substance. In this case, there is a sufficient number of α-and β-emitters in the immediate vicinity of tumor cells to ensure their destruction with minimal damage to the surrounding tissues 9,10 An important feature of lutetium's kinetics is that due to its low penetration range into tissues, it is effective in the treatment of small lesions and minimizes the impact of therapeutic doses on remote cells. 177 Lu is a beta-emitting radionuclide with an energy of 0.49 MeV and a half-life of 6.6 days (161 h).…”