Ultra-low-dose CT vs. chest X-ray in non-traumatic emergency department patients - a prospective randomised crossover cohort trial.

Background: Ultra-low-dose CT (ULDCT) examinations of the chest at only twice the radiation dose of a chest X-ray (CXR) now offer a valuable imaging alternative to CXR. This trial prospectively compares ULDCT and CXR for the detection rate of diagnoses and their clinical relevance in a low-prevalence cohort of non-traumatic emergency department patients.
Methods: In this prospective crossover cohort trial, 294 non-traumatic emergency department patients with a clinically indicated CXR were included between May 2nd and November 26th of 2019 (www.clinicaltrials.gov: NCT03922516). All participants received both CXR and ULDCT, and were randomized into two arms with inverse reporting order. The detection rate of CXR was calculated from 'arm CXR' (n = 147; CXR first), and of ULDCT from 'arm ULDCT' (n = 147; ULDCT first). Additional information reported by the second exam in each arm was documented. From all available clinical and imaging data, expert radiologists and emergency physicians built a compound reference standard, including radiologically undetectable diagnoses, and assigned each finding to one of five clinical relevance categories for the respective patient.
Findings: Detection rates for main diagnoses by CXR and ULDCT (mean effective dose: 0.22 mSv) were 9.1% (CI [5.2, 15.5]; 11/121) and 20.1% (CI [14.2, 27.7]; 27/134; P  = 0.016), respectively. As an additional imaging modality, ULDCT added 9.1% (CI [5.2, 15.5]; 11/121) of main diagnoses to prior CXRs, whereas CXRs did not add a single main diagnosis (0/134; P  < 0.001). Notably, ULDCT also offered higher detection rates than CXR for all other clinical relevance categories, including findings clinically irrelevant for the respective emergency department visit with 78.5% (CI [74.0, 82.5]; 278/354) vs. 16.2% (CI [12.7, 20.3]; 58/359) as a primary modality and 68.2% (CI [63.3, 72.8]; 245/359) vs. 2.5% (CI [1.3, 4.7]; 9/354) as an additional imaging modality.
Interpretation: In non-traumatic emergency department patients, ULDCT of the chest offered more than twice the detection rate for main diagnoses compared to CXR.
Funding: The Department of Biomedical Imaging and Image-guided Therapy of Medical University of Vienna received funding from Siemens Healthineers (Erlangen, Germany) to employ two research assistants for one year.
Competing Interests: The Department of Biomedical Imaging and Image-guided Therapy of Medical University of Vienna has grants and contracts with more than 100 partners (organizational, academic, industry), all through official contracts with the Medical University of Vienna. Among these was funding from Siemens Healthineers (Erlangen, Germany) to employ two research assistants for one year for this study as well as grants independent of this study. CW was employed as research assistant by Medical University of Vienna for one year, enabled by funding from Siemens Healthineers and furthermore reports support for congress fees, travel and accommodation costs, unrelated to this study, by Medical University of Vienna. DT reports consulting fees from Roche and Siemens Healthineers, support for attending meetings and/or travel from Siemens Healthineers and participation on the DSM board, all unrelated to this study. HP reports honoraria as a speaker from AstraZeneca, BMS, Boehringer Ingelheim, Janssen, MSD, Novartis, Roche, Sanofi, Siemens Healthcare and Takeda as well as participation on the advisory board of AstraZeneca, Boehringer Ingelheim, Janssen, MSD and Sanofi, all unrelated to this study. MS reports support for congress fees, travel and accommodation costs, unrelated to this study, by Medical University of Vienna. RES reports honoraria as an educational speaker from Siemens Healthineers and a pending patent developed with Siemens Healthineers, all unrelated to this study. PA reports honoraria as a speaker from Siemens Healthineers, unrelated to this study. WB reports unpaid participation on the editorial board of Medical Physics and Zeitschrift fuer Medizinische Physik, both unrelated to this study. CH reports unpaid participation on the Photon Counting CT advisory board of Siemens Healthineers as well as stock ownership of Hologic until 2021, all unrelated to this study. HR was the PI of grants to the Medical University of Vienna from Siemens Healthineers until June 2018 and is still scientifically involved in several studies concerning these grants, but did not and does not receive remuneration nor is he part of the contracts; HR further reports honoraria as a clinical speaker from Siemens Healthineers until December 2019 and unpaid participation on the editorial board of European Radiology. The other authors declare no further competing interests.
(© 2023 The Author(s).)