Modeling and dose calculations of a pure beta emitting 32P coated stent for intracoronary brachytherapy by Monte Carlo code

Recently, different investigators have studied the possibility of radiation therapy in restenosis prevention and have shown promising results. In this study a unique radioactive source for intra vascular brachytherapy [IVBT] was investigated. The two-dimensional dose distribution in water for a 32P IVBT stent has been calculated. The pure beta emitter source 32P has been coated on Palmaz-Schatz stent. The dosimetric parameters required by the AAPM TG-60 formalism are discussed and calculated. The dose distribution of the activated stent was determined by Version 4C of the [MCNP] Monte Carlo radiation transport code in water and it was verified by TG-60 experimental results. Dosimetric parameters such as anisotropy function, F[r, theta], and the radial dose function, gL[r], around the Palmaz-Schatz stent at distances from 0.18 to 0.9 cm have been calculated. The Palmaz-Schatz stent with 3.5 mm external diameter and 14 mm length is coated with a thin layer of 32P. The Monte Carlo calculated dose rate at the reference point is found to be 17.85 Gy. The results were compared with previously published paper for an actual same source. The difference between these two data sets is in acceptable range. There were almost little differences [less than 0.05%] in values among them. The dosimetry parameters such as, geometry function, G[r, theta], anisotropy function, F[r, theta] and radial dose function, g[r], were determined according to TG-60 protocols and listed in tabular format. High dose variants were visible near the 32P stent surface, but these values decreased with depth in vessel layers rapidly. There are an acceptable agreement between the calculated data in this study and other published data for the same source. However, the observed differences between the calculated and measured values could be explained by the measurement uncertainty and the geometry modeling during the simulations

Tratamento de lesão de tronco da artéria coronária esquerda após radioterapia do tórax / Treatment of left main coronary artery lesion after late thoracic radiotherapy

A prevenção de complicações cardiovasculares tardias após radioterapia (RT) para tratamento de um tumor maligno é um desafio. Relatamos o caso de um jovem paciente com linfoma de Hodgkin submetido a tratamento com RT que desenvolveu doença cardíaca isquêmica no seguimento, embora não apresentasse fatores de risco cardiovasculares. Concluímos que pacientes submetidos a RT que apresentam dor torácica deveriam ser criteriosamente avaliados em relação à doença arterial coronariana.

Prevention of late cardiovascular complications after radiation therapy (RT) for treatment of a malignant tumor is challenging. We report the case of a young male patient with Hodgkin's lymphoma treated with RT, who developed ischemic heart disease during follow-up, although he had no cardiovascular risk factors. We conclude that patients undergoing RT who experience chest pain should be fully investigated for coronary artery disease.