Dosimetric evaluation of the low-dose radiotherapy (LD-RT) technique for the treatment of SAR-Cov-2 pneumonia

Low-dose radiotherapy (LD-RT) acts on the cells that participate in the inflammatory response, producing an anti-inflammatory effect. SARS-Cov-2 pneumonia develops a systemic inflammatory response at the pulmonary level with a syndrome of cytokine release, mainly IL-1, IL-6 and TNF-alpha. Currently, various in vitro, experimental in vivo and clinical studies have demonstrated the efficacy of LD-RT by reducing clinical inflammatory parameters with doses ranging from 0.5 to 1.5 Gy, with an increase in the expression of anti-inflammatory cytokines such as TGF-β1. The LD-RT technique proposed for the radiotherapy service of the Central Military Hospital for the treatment of SAR-Cov-2 pneumonia, consists of the total irradiation of the lung tissue at a single radiation dose of 1.0 Gy. The objective of this research work is to dosimetric ally evaluate this unconventional treatment technique prior to clinical implementation in order to guarantee adequate irradiation of target volumes; The irradiation was carried out in a Theratronics Co-60 teletherapy equipment, model T780C, with an Alderson RANDO anthropomorphic mannequin, which has a density equivalent to lung tissue, for the measurement of radiation dose a radiochromic dye film detector (EBT3) was used, distributing the film inserts inside the mannequin, likewise the modeling and validation of the equipment was carried out of Co-60 in the XIO planning system version 5.0. The treatment technique used for the implementation of this clinical protocol was a standard isocentric technique of two fields, an anterior and a posterior field, for the evaluation of the dose distribution in the target volumes, the dosimetric parameters were considered as the average dose. , the minimum dose (D min), the maximum dose (D max) and the homogeneity index (HI) in the target volumes, comparing the measurements obtained with the prescription dose and the dose calculated by the planning system. (author)