Monte Carlo dosimetry for ¹⁰³Pd, ¹²⁵I, and ¹³¹Cs ocular brachytherapy with various plaque models using an eye phantom

Abstract

The combined effects of ocular and plaque media on dose are significant and vary with plaque model and radionuclide, suggesting the importance of model-based dose calculations employing accurate ocular and plaque media and geometries for eye plaque brachytherapy.

Advanced Collapsed cone Engine dose calculations in tissue media for COMS eye plaques loaded with I‐125 seeds

“…More accurate dose calculations within the eye reporting dose to medium may also result in more accurate correlation between prescribed dose and tumor control rate, and between doses to critical structures and toxicity rates, and thereby could improve the consistency of multi‐institutional dose prescription. The use of a model‐based dose calculation algorithm, such as ACE, would also allow for volumetric based planning, which represents an important step forward for ocular brachytherapy, as also discussed by Lesperance et al…”

“…Replacing water with a homogenized eye material or lens material was found to cause dose decreases in the eye region of ~2%–3% and ~7%–9%, respectively, by Thomson et al, whereas using a realistic eye model containing a number of structures and materials resulted in larger differences in dose throughout the eye as reported by Lesperance et al: up to 10% within a choroidal melanoma and up to 14% within the lens . These differences were also radionuclide (photon energy) and plaque model/design dependent . Differences in scattering conditions due to large air interfaces can also cause significant dose differences, typically resulting in dose overestimation when using the TG‐43 formalism.…”

“…To validate the implementation of this model in MCNP6, the materials and densities used by Lesperance et al were replicated and the total dose was calculated using the source strength required to deliver 85 Gy at the tumor apex for a completely homogeneous water scenario (D TG‐43sim as described in Lesperance et al) in 100 hr, based on the value simulated for for the model 6711 source and accounting for source decay. Mean doses within the various structures in the eye (tumor, lens, vitreous, and sclera) as well as doses at points of interest (POI) (tumor apex, center of the lens, optic disk, fovea, and near and far sclera/retina on the CAX; given by the 1–4 voxels that make up the POI as some are located at a vertex or between two voxels) were compared to the values given in table in Lesperance et al for the I‐125 seed.…”

Gold nanoparticle‐based brachytherapy enhancement in choroidal melanoma using a full Monte Carlo model of the human eye

“…As has been emphasized in the previous report, the geometry and characteristic of this simulated eye globe have been determined in a manner that the dimension and specification of main parts of the human eye could be in conformity with the medical data 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 . The chemical compositions and densities of different components of the eyeball tissues which were used in these simulations are given in Table 2.…”

Effect of elemental compositions on Monte Carlo dose calculations in proton therapy of eye tumors

“…Nowadays, enucleation has been supplanted by radiotherapy 35 as the standard method of care for patients with uveal melanoma. External beam radiotherapy with heavy charged particles [2][3][4] and eye plaque brachytherapy [5][6][7] are two modalities of radiation therapy employed frequently for treating such tumors. 40 The main goal in choosing the most appropriate method for therapy is achievement of high radiation dose deposition in the tumor while sparing the surrounding healthy tissue as much as possible.…”