Introduction: Using computed tomography (CT) and treatment planning systems (TPS) in radiotherapy, due to the difference in photon beam energy on CT and linear accelerator, it is necessary to convert Hounsfield units (HU) to relative electron density (RED) values. The aim of this dosimetric study was to determine whether there is a significant effect of potential in the CT tube, field of view size (FOV), and phantom dimensions on the CT conversion curve CT-RED. The second aim is whether there are significant differences between the CT-RED obtained by the Computerized Imaging Reference Systems (CIRS) Thorax 002LFC phantom and the “reference” curve in the TPS, obtained by the CIRS 062M pelvis phantom, at the same CT conditions.Methods: Heterogeneous CIRS 062M and CIRS Thorax 002LFC phantoms were used, which anatomically and dimensionally represent the human pelvis, head, and thorax, with a set of known RED inserts. They were scanned on a CT LightSpeed GE simulator and obtained CT-RED.Results: The high voltage in the CT tube had a significant effect on the HU (t = 10.72, p < 0.001) for RED values >1.1, while FOV as a parameter did not show statistical significance for the 062M pelvis phantom. Comparing the slopes (062M pelvis and head) of the CT-RED for RED ≥ 1.1, the obtained value is t = 1.404 (p = 0.163). In the case of a 062M pelvis and a 002LFC phantom, we have seen a difference in RED values (for the same HU value) of 5 % in the RED region ≥ 1.1 (bone).Conclusion: Patients should be imaged on a CT simulator only at the potential of the CT tube on which the conversion curve was recorded. The influence of the FOV and scanned phantom dimensions is not statistically significant on the appearance of the calibration curve (RED ≥ 1.1).
Background/Aim. The aim of the study was investigating the significant difference in: a) the dosimetric calculation of the radiotherapy treatment planning system (TPS) in relation to the values obtained by measuring on the linear accelerator (Linac), b) the accuracy of the dosimetric calculation between the calculating algorithms Analytical Anisotropic Algorithm (AAA) and AcurosXB in various tissues and photon beam energies. Methods. For End-to-End test we used the heterogeneous phantom CIRS Thorax002LFC, which anatomically represents the human torso with set of inserts known relative electron density (RED) for obtaining a CT calibration curve, comparable to the "reference" CIRS 062M phantom. For the AAA and AcurosXB algorithms and for 6 MV and 16 MV photon beams in the TPS Varian Eclipse 13.6, four 3D conformal (3DCRT), and one intensity modulated (IMRT) and volumetric modulated arc (VMAT) radiotherapy plans were made. Measurements of the absolute dose in the Thorax phantom, by PTW-Semiflex ionization chamber, were carried out on three Varian-DHX Linacs. Results. The difference between "reference" and measured CT conversion curves in the bone area is 3 %. For 476 phantom measurements, the difference between measured and TPS calculated dose of (3-6) %, we had in 30 (6.3 %) cases. According to regression analysis, the standardized Beta coefficient for relative errors, 6 MV vs 16 MV, was 0.337 (33.7 %, p < 0.001). Mean relative errors for AAA vs AcurosXB, using Mann-Whitney test, for bones were 1.56 % and 2.64 % (p = 0.004). Conclusion. The End-to-End test on Thorax002LFC phantom proved the accuracy of TPS dose calculation in relation to the one delivered to the patient by Linac. There is a significant difference for photon energies relative errors (higher values are obtained for 16 MV vs 6 MV). A statistically significant minor relative error in AAA vs. AcurosXB was found for the bone.
Background/Aim: For patients with left sided breast cancer, a major concern is the dose of radiation delivered to the heart,because of increased risk of exposure and consequently increased risk of major coronary events and side effects. In order to reduce the dose to the heart during breast irradiation, Deep inspiration breath hold (DIBH) technique was implemented in our institution. Aim of this retrospective study was to compare dosimetric parameters of the DIBH on the: heart, left anterior descending artery (LAD) and ipsilateral lung (IL), compared with free breathing (FB) technique. Methods: Twenty patients who underwent radiotherapy with DIBH at our institution were retrospectively analysed. Two computed tomography (CT) scans were acquired for each patient, FB-CT and DIBH-CT. Plans consisted of two opposed tangential segmented beams and one direct beam with small dose contribution. Doses to the heart, LAD, and IL were assessed. Results: Dosimetric comparison between FB and DIBH for mean dose to the heart was 5.17 Gy vs. 3.68 Gy (p<0.0001), and the mean percentage of the volume receiving 25 Gy was 4.63% vs. 0.85% (p<0.0001), respectively. Mean dose for LAD was 26.09 Gy vs. 11.89 Gy (p=0.00014). Mean percentage of the volume receiving 20 Gy for the IL was 15.16% vs. 13.26% (p=0.0007) for FB and DIBH, respectively. Conclusion: Implementation of DIBH technique in radiotherapy treatment of patients with left sided breast cancer statistically significant reduces the dose delivered to the surrounding organs at risk (OAR), particularly to the heart and LAD, with optimal target coverage.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.