Estimation of size-specific dose estimate (SSDE) of CT scans using an effective diameter electron density

• Published in: European journal of radiology 2024-03, Vol.172, p.111311-111311, Article 111311
• Main Authors: Almuqbil, Khuloud, Abuhaimed, Abdullah, Abanomy, Ahmed, Alashban, Yazeed, Alhawas, Abdulrahman, Martin, Colin J
• Format: Article
• Language: English
• Subjects: Effective diameter (Deff); Electron Density Effective Diameter; Size-specific dose estimate (SSDE); The lateral (LAT) and anterior-posterior (AP) dimensions; Volume Computed Tomography Dose Index (CTDIvol); Water equivalent diameter (Dw)
• ISSN: 0720-048X; 1872-7727
• DOI: 10.1016/j.ejrad.2024.111311

•The Deffρe method was proposed to overcome the challenges of using the water equivalent diameter (Dw) method used for SSDE.•The Deffρe method is based on correcting effective diameter (Deff) with electron densities of tissues of a scan area.•Results of the Deffρe method showed to be promise for the chest protocols, but was less accurate for other body protocols.•The Deff method was poorer for the chest protocols, but gave good assessments for other body protocols.•Correction of both dimensions, lateral (LAT) and anterior-posterior (AP), did not improve the accuracy of the Deffρe method. An assessment of the effective diameter of a patient’s body using electron densities of tissues inside the scan area (Deffρe) was proposed to overcome challenges associated with the estimation of water-equivalent diameter (Dw), which is used for size-specific dose estimate (SSDE). The aims of this study were to (1) investigate the Deffρe method in two different forms using a wide range of patient sizes and scanning protocols, and (2) compare between four methods used to estimate the patient size for SSDE. Under IRB approval, a total of 350 patients of varying sizes have been collected retrospectively from the Hospital. The Dw values were assessed over six different CT body protocols: (1) chest with contrast media, (2) chest High-Resolution Computed Tomography (HRCT) without contrast media, (3) abdomen-pelvis with contrast media, (4) abdomen-pelvis without contrast media, (5) chest-abdomen-pelvis with contrast media, and (6) pelvis without contrast media. A MATLAB-based code was developed in-house to assess the size of each patient using the conventional effective diameter method (Deff), Deffρe by correcting either both the lateral (LAT) and anterior-posterior (AP) dimensions (Deff,LAT+APρe) or LAT only (Deff,LATρe), and Dw at the mid-CT slice of the patient images. The results of Deff,LAT+APρe and Deff,LATρe provided a better estimation for the chest protocols with the averages of absolute percentage difference (PD) values in the range of 3 – 7 % for all patient sizes as compared to the Dw method, whereas the averages of PD values for the Deff method were 9 – 15 %. However, Deff gave a better estimation for Dw values for the other body protocols, with differences of 2 – 4 %, which were lower than those obtained with the Deff,LAT+APρe and Deff,LATρe methods. For the chest protocols, statistically significant differences were found between Deff and the other methods, but the