Dosimetría tridimensional por Monte Carlo del tratamiento tópico con 188Re de carcinoma de células escamosas y basales

Abstract

Basal and squamous cell carcinoma is currently treated mainly by surgery. In search of non-invasive treatments, topical treatment with 188Re has been developed and has shown satisfactory results. However, there are currently only two-dimensional descriptions of the spatial distribution of absorbed dose (D) in the target region, which limits the information regarding D to surrounding healthy tissue. Therefore, the aim of the present work was to determine with the Monte Carlo technique the three-dimensional distribution of D in the topical treatment with 188Re of squamous and basal cell carcinoma. Methodology. The simulation scenario consisted of a cream containing re-188 uniformly distributed, a mylar plastic sheet, and a voxel type phantom representing the skin with a volume of 2 X 2 X 0:1 cm3 the voxel size was 100 ¹m per side. The isodose surfaces, as well as the curves in the sagittal and transverse sections were analyzed to describe the distribution of D. Results and Conclusion. The spatial distribution patterns of D were shown. The irradiation times necessary for different activities to impart a dose of 50 Gy in the depth range of 250 - 750 ¹m were determined. The Homogeneity Index reveals how homogeneity decreases as depth increases. Using the therapeutic configuration described in this work, which is the one used in clinical practice, it is concluded that it is possible to give treatment at depths of 250-650 ¹m without exceeding the recommended absorbed dose limit for the epidermis, which is exceeded if the prescribed dose is reached at a depth of 750 ¹m. The topical brachytherapy with 188Re for the treatment of squamous and basal cell cancer is economical, safe, effective, practical and painless, which as a plus after treatment presents excellent cosmetic results.