Quantitative characteristics of radiation-induced lung damage in oncological patients during radiotherapy based on RCT data

Abstract

Objective. Comparison of the magnitude of the change in the density of lung tissue and the volume of these changes after radiation therapy over time based on the data obtained using the new method of quantitative analysis developed by us and with the usual visual assessment of the CT data.Materials and methods. We used the data of dynamic observation of 90 patients who underwent RT for the tumors of thoracic localization during the period from 2014 to 2021 at the Federal Institution “Russian Scientific Center of Roentgenoradiology”. These patients had CT examinations performed before and after RT. Control CT studies were performed 1–237 days after RT (mean control interval 96 ± 64.3 days). A total of 238 CT studies of these patients were analyzed, with an average number of RCT studies per patient of 2.6. Among the selected patients, there were 36 (40%) men and 54 (60%) women aged 23 to 86 years (the average age was 51.9 ± 15.6 years).Results. Radiation damage in the lungs using the method of quantitative analysis of CT data is detected starting from the value of ΔHU = 20 and volume from 3.2% for the early period (15–35 days) after the end of treatment. Starting from 15–25 to 50 days after the end of RT, quantitative analysis reveals primary changes in the lung tissue, incl. and undetectable visually (from 20 to 80 HU), and to suggest further dynamics of these changes depending on the characteristics of the performed RT. From 50 to 80 days – reveals the real volume of radiation pulmonitis by taking into account the changes invisible during visual analysis in the lung tissue irradiated at a dose of 20 Gy to 30 Gy. From 80 to 120 days – allows you to assess the presence and dynamics of changes in the lung tissue with the threshold radiation dose in the lung tissue 30–35 Gy. From 120 onwards, quantitative analysis of CT data, as well as visual assessment, reveals damage in areas of the lungs with the dose of more than 30–35 Gy, which is caused by post-radiation pneumofibrosis. On the basis of the obtained quantitative data on radiation lung damage, the mathematical regularities of the development of this process were calculated, taking into account the time and dose factors.Conclusions. Quantitative assessment of changes in lung density according to CT data in dynamics, carried out using the technique developed by us, is a radiomic indicator of their radiation damage during therapeutic irradiation in cancer patients, which, in combination with the presented mathematical model, can be used for diagnostic purposes to quantify the severity and predicting the dynamics of radiation damage to the lungs in general, as well as identifying individual radiosensitivity.The results obtained can be presented not only in the form of graphs, but also in the form of color maps with preservation of anatomical landmarks, which is convenient for use in clinical practice to support medical decision-making on patient management.