Radioprotection 2025, 60( 3), 268 – 276 © A. Khallouqi et al., Published by EDP Sciences 2025 https:// doi. org / 10.1051 / radiopro / 2024063
Available online at: www. radioprotection. org
ARTICLE
Comparison of water-equivalent and effective diameter-based size-specific dose estimates in computed tomography pulmonary angiography: implications for radiation dose optimization
A. Khallouqi 1, 2,*, H. Sekkat 1, A. Halimi 1 and O. El Rhazouani 1
1 Hassan 1st University Settat, Laboratory of Health Sciences and Technologies, High Institute of Health Sciences, Settat, Morocco. 2 Department of Radiology Public Hospital, Mediouna, Morocco.
Received: 26 September 2024 / Accepted: 16 December 2024
Abstract – This retrospective study investigates dose estimation in computed tomography pulmonary angiography( CTPA) by analyzing 200 examinations from 96 male and 104 female patients. Two sizespecific dose estimation( SSDE) methods were evaluated: one based on effective diameter( SSDE Deff) and the other on water-equivalent diameter( SSDE Dw). The effective diameter( D eff) was manually measured using the lateral( LAT) and anteroposterior( AP) dimensions, while the water-equivalent diameter( D w) was calculated from the region of interest( ROI) using mean Hounsfield Unit( HU) values and cross-sectional area. SSDE calculations were compared to the conventional CT dose metric, CTDIvol, to assess its underestimation relative to SSDE Dw. The findings revealed a dose underestimation of up to 18 % for CTDIvol compared to SSDE Dw, particularly for patients with larger body habitus. SSDE Deff consistently overestimated the dose by 7.73 % compared to SSDE Dw, as Deff relied only on external dimensions while D w considered tissue attenuation for a more individualized dose assessment. High correlations were observed between lateral diameter( d LAT) and both D eff( R 2 = 0.9175) and Dw( R 2 = 0.7578). However, the systematic overestimation by SSDE Deff emphasizes the importance of clearly specifying the metric used for SSDE, as differences can influence reported doses by 5 – 10 %, affecting clinical dose monitoring and adherence to diagnostic reference levels. This study highlights the limitations of CTDIvol and SSDE Deff compared to SSDE Dw, especially in regions with heterogeneous tissue. The results support the use of individualized radiation dose assessments to improve radiation safety, particularly in CTPA, which has seen increased application during the COVID-19 pandemic.
Keywords: CTPA / radiation dose / size-specific dose estimates / water-equivalent diameter / COVID-19 / Morocco
1 Introduction
Pulmonary embolism( PE) remains a significant global health concern, with particular relevance in regions like Morocco where its prevalence continues to be high. The recent COVID-19 pandemic has further complicated this landscape, as SARS-CoV-2 infection has been associated with an increased incidence of thromboembolic events, including PE. This relationship between COVID-19 and coagulation disorders puts the attention to the critical importance of accurate and timely PE diagnosis, especially in the postpandemic era( Ataalla, 2022; Mouzarou et al., 2022) .
In this context, Computed Tomography Pulmonary Angiography( CTPA) has emerged as a focal diagnostic tool, offering unparalleled accuracy in detecting PE and other
* Corresponding author: a. khallouqi @ uhp. ac. ma thoracic pathologies( Karimizarchi and Chaparian, 2017; Semghouli et al., 2024) . CTPA employs intravenous contrast media to visualize the pulmonary arterial system, enabling the delineation of the main pulmonary artery and its branching network. The technique’ s diagnostic power lies in its ability to reveal filling defects within the pulmonary vasculature, allowing radiologists to identify potentially life-threatening conditions with high precision( Saeedi-Moghadam et al., 2021) .
The COVID-19 pandemic has expanded CTPA’ s role beyond PE diagnosis to include differentiation between COVID-19-related lung changes and other pulmonary complications. However, this increased utilization raises significant concerns regarding cumulative radiation exposure to patients. As CTPA examinations become more frequent, the medical physics community faces a pressing need to optimize radiation dose while keeping the required diagnostic efficacy( Yeung, 2019).
This is an Open Access article distributed under the terms of the Creative Commons Attribution License( https:// creativecommons. org / licenses / by / 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.