Evaluation of overexposure risk when there is a space between the subject and the couch in computed tomography: a phantom study

Yuta Fujiwara; Yoshiki Kamihoriuchi; Fumie Higuchi; Shinichi Nakayama; Yutako Ohyama; Tomoko Sasaki; Shinsaku Watanabe; Takanori Masuda

doi:10.1007/s12194-024-00804-y

Evaluation of overexposure risk when there is a space between the subject and the couch in computed tomography: a phantom study

Radiol Phys Technol. 2024 Apr 26. doi: 10.1007/s12194-024-00804-y. Online ahead of print.

Authors

Yuta Fujiwara¹, Yoshiki Kamihoriuchi², Fumie Higuchi², Shinichi Nakayama², Yutako Ohyama², Tomoko Sasaki², Shinsaku Watanabe², Takanori Masuda³

Affiliations

¹ Division of Clinical Radiology Service, Okayama Central Hospital, 6-3, Ishimakitamachi, Kitaku, Okayama, 700-0017, Japan. y_fujiwara_gishi@yahoo.co.jp.
² Division of Clinical Radiology Service, Okayama Central Hospital, 6-3, Ishimakitamachi, Kitaku, Okayama, 700-0017, Japan.
³ Department of Radiological Technology, Faculty of Health Science and Technology, Kawasaki University of Medical Welfare, Matsushima, Kurashiki, Okayama, 288701-0193, Japan.

PMID: 38668938
DOI: 10.1007/s12194-024-00804-y

Abstract

The purpose of this study was to investigate the risk of overexposure associated with automatic tube current modulation (ATCM) and automatic couch height positioning compensation mechanism (AHC) in computed tomography (CT) systems, particularly in scenarios involving a gap between the subject and the couch. Results revealed that when AHC was enabled, CT dose index volume (CTDI_vol) increased by approximately 10% at 2.5 cm, 20% at 5.0 cm, and 40% at 10.0 cm gaps compared to close contact conditions. While the AHC function ensures consistent exposure doses and image quality regardless of subject positioning relative to the CT gantry isocenter, the study highlights a potential risk of overexposure when a gap exists between the subject and the couch. These findings offer valuable insights for optimizing CT imaging protocols and underscore the importance of carefully considering subject positioning in clinical practice.

Keywords: Automatic couch height compensation mechanism (AHC); Automatic tube current modulation (ATCM); Computed tomography (CT); Exposure dose.