Pace Martina, Bonanno Elisa, Borzì Giuseppina Rita, Cavalli Nina, D'Anna Alessia, Gueli Anna Maria, Stella Giuseppe, Zirone Lucia, Marino Camelo
Medical Physics Department, Humanitas Istituto Clinico Catanese, Misterbianco, CT, Italy.
Department of Physics and Astronomy E. Majorana, University of Catania, Catania, Italy.
Phys Med. 2023 Aug;112:102627. doi: 10.1016/j.ejmp.2023.102627. Epub 2023 Jun 20.
This study aims to compare two methods for the organ dose evaluation in computed tomography (CT) in the head- and thorax regions: an experimental method, using radiochromic films, and a computational one, using a commercial software.
Gafchromic® XR-QA2 and EBT-3 were characterized in terms of energetic, angular, and irradiation configurations dependence. Two free-in-air irradiation calibration configurations were employed using a CT scanner: with the sensitive surface of the film orthogonal (OC) and parallel (PC) to the beam axis. Different dose-response curves were obtained by varying the irradiation configurations and the beam quality (BQ). Subsequently, films were irradiated within an anthropomorphic phantom using CT-thorax and -head protocols, and the organ dose values obtained were compared with those provided by the commercial software.
At different configurations, an unchanged dose response was achieved with EBT-3, while a dose response of 15% was obtained with XR-QA2. By varying BQ, XR-QA2 showed a different response below 10%, while EBT-3 showed a variation below 5% for dose values >20 mGy. For films irradiation angle equal to 90°, the normalized to 0° relative response was 41% for the XR-QA2 model and 83% for the EBT-3 one. Organ dose values obtained with EBT-3 for both configurations and with XR-QA2 for OC were in agreement with the DW values, showing percentage discrepancies of less than 25%.
The obtained results showed the potential of EBT-3 in CT patient dosimetry since the lower angular dependence, compared to XR-QA2, compensates for low sensitivity in the diagnostic dose range.
本研究旨在比较头部和胸部计算机断层扫描（CT）中两种器官剂量评估方法：一种是使用放射变色胶片的实验方法，另一种是使用商业软件的计算方法。
对Gafchromic® XR-QA2和EBT-3在能量、角度和照射配置依赖性方面进行了表征。使用CT扫描仪采用两种空气自由照射校准配置：胶片敏感表面与光束轴正交（OC）和平行（PC）。通过改变照射配置和光束质量（BQ）获得不同的剂量响应曲线。随后，使用CT胸部和头部协议在人体模型内对胶片进行照射，并将获得的器官剂量值与商业软件提供的值进行比较。
在不同配置下，EBT-3实现了不变的剂量响应，而XR-QA2获得了15%的剂量响应。通过改变BQ，XR-QA2在低于10%时显示出不同的响应，而对于剂量值>20 mGy，EBT-3显示出低于5%的变化。对于胶片照射角度等于90°，XR-QA2模型相对于0°的归一化相对响应为41%，EBT-3为83%。两种配置下使用EBT-3以及OC配置下使用XR-QA2获得的器官剂量值与DW值一致，百分比差异小于25%。
所得结果表明EBT-3在CT患者剂量测定中的潜力，因为与XR-QA2相比，较低的角度依赖性补偿了诊断剂量范围内的低灵敏度。
