Objective Diagnostic reference levels (DRLs) are essential for optimizing radiation dose in CT examinations. However, current DRLs may not reflect the performance of CT scanners or the background of individual facilities, potentially leading to misleading dose indicators. Furthermore, the factors that influence DRLs remain unclear. This study aims to investigate how facility characteristics and CT scanner performance affect DRLs. Materials and methods A dose survey was conducted in 2023 targeting 982 medical facilities in Tokyo. Data were collected from 100 facilities and 176 CT scanners, focusing on adult patients (50–70 kg) undergoing common CT protocols. CTDIvol and DLP were analyzed, and the 75th percentile was defined as the Tokyo-DRL. Factors potentially influencing DRLs, including the presence of radiologists, certified CT technologists, hospital size, CT scanner specifications, and image reconstruction methods, were systematically evaluated. Results The Tokyo-DRLs were lower than Japan’s 2020 DRLs across all protocols, likely reflecting advancements in CT technology and staff expertise. Radiation doses were lower in facilities with radiologists and certified CT technologists, more hospital beds, wider scan beam widths, and use of iterative reconstruction or deep learning-based reconstruction. For dual-energy CT, DRLs were established only for the pulmonary artery with contrast due to limited data. Multivariate analysis revealed key dose-influencing factors such as tube current modulation and scan sequence in the head, and beam width in trunk scanning. Conclusion Facility characteristics and scanner performance significantly impact radiation dose. Periodic, detailed surveys are necessary to update DRLs in line with evolving technologies and clinical practice. Key Points <Emphasis Type="BoldItalic">Question</Emphasis> How do facility characteristics and CT scanner performance influence diagnostic reference levels in clinical CT examinations? <Emphasis Type="BoldItalic">Findings</Emphasis> Radiation doses in CT examinations varied significantly depending on facility size, staff expertise, scanner specifications, and image reconstruction methods. <Emphasis Type="BoldItalic">Clinical relevance</Emphasis> Identification of facility and scanner characteristics enables more effective radiation dose optimization, enhancing patient safety without compromising diagnostic quality in CT imaging. Graphical Abstract

Establishment of CT diagnostic reference levels (DRLs) in Tokyo

期刊论文
发表日期：

2025年12月8日

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Hideyuki Sato,
Masanori Sugaya,
Kazufumi Ishida,
Yuichi Nakai,
Koichi Sugisawa,
Yosuke Kogure

摘要

Objective

Diagnostic reference levels (DRLs) are essential for optimizing radiation dose in CT examinations. However, current DRLs may not reflect the performance of CT scanners or the background of individual facilities, potentially leading to misleading dose indicators. Furthermore, the factors that influence DRLs remain unclear. This study aims to investigate how facility characteristics and CT scanner performance affect DRLs.

Materials and methods

A dose survey was conducted in 2023 targeting 982 medical facilities in Tokyo. Data were collected from 100 facilities and 176 CT scanners, focusing on adult patients (50–70 kg) undergoing common CT protocols. CTDIvol and DLP were analyzed, and the 75th percentile was defined as the Tokyo-DRL. Factors potentially influencing DRLs, including the presence of radiologists, certified CT technologists, hospital size, CT scanner specifications, and image reconstruction methods, were systematically evaluated.

Results

The Tokyo-DRLs were lower than Japan’s 2020 DRLs across all protocols, likely reflecting advancements in CT technology and staff expertise. Radiation doses were lower in facilities with radiologists and certified CT technologists, more hospital beds, wider scan beam widths, and use of iterative reconstruction or deep learning-based reconstruction. For dual-energy CT, DRLs were established only for the pulmonary artery with contrast due to limited data. Multivariate analysis revealed key dose-influencing factors such as tube current modulation and scan sequence in the head, and beam width in trunk scanning.

Conclusion

Facility characteristics and scanner performance significantly impact radiation dose. Periodic, detailed surveys are necessary to update DRLs in line with evolving technologies and clinical practice.

Key Points

Question How do facility characteristics and CT scanner performance influence diagnostic reference levels in clinical CT examinations?

Findings Radiation doses in CT examinations varied significantly depending on facility size, staff expertise, scanner specifications, and image reconstruction methods.

Clinical relevance Identification of facility and scanner characteristics enables more effective radiation dose optimization, enhancing patient safety without compromising diagnostic quality in CT imaging.

Graphical Abstract