Can We Perform CT of the Appendix with Less Than 1 mSv? A De-escalating Dose-simulation Study
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To systematically explore the lowest reasonably achievable radiation dose for appendiceal CT using an iterative reconstruction (IR) in young adults.
We prospectively included 30 patients who underwent 2.0-mSv CT for suspected appendicitis. From the helical projection data, 1.5-, 1.0- and 0.5-mSv CTs were generated using a low-dose simulation tool and the knowledge-based IR. We performed step-wise non-inferiority tests sequentially comparing 2.0-mSv CT with each of 1.5-, 1.0- and 0.5-mSv CT, with a predetermined non-inferiority margin of 0.06. The primary end point was the pooled area under the receiver-operating-characteristic curve (AUC) for three abdominal and three non-abdominal radiologists.
For the abdominal radiologists, the non-inferiorities of 1.5-, 1.0- and 0.5-mSv CT to 2.0-mSv CT were sequentially accepted [pooled AUC difference: 2.0 vs. 0.5 mSv, 0.017 (95% CI: -0.016, 0.050)]. For the non-abdominal radiologists, the non-inferiorities of 1.5- and 1.0-mSv CT were accepted; however, the non-inferiority of 0.5-mSv CT could not be proved [pooled AUC difference: 2.0 vs. 1.0 mSv, -0.017 (-0.070, 0.035) and 2.0 vs. 0.5 mSv, 0.045 (-0.071, 0.161)].
The 1.0-mSv appendiceal CT was non-inferior to 2.0-mSv CT in terms of diagnostic performance for both abdominal and non-abdominal radiologists; 0.5-mSv appendiceal CT was non-inferior only for abdominal radiologists.
• For both abdominal and non-abdominal radiologists, 1.0-mSv appendiceal CT could be feasible.
• The 0.5-mSv CT was non-inferior to 2.0-mSv CT only for expert abdominal radiologists.
• Reader experience is an important factor affecting diagnostic impairment by low-dose CT.
KeywordsAppendicitis Prospective studies Tomography, X-ray computed ROC curve Sensitivity and specificity
Area under the receiver-operating-characteristic curve
We thank Kyung Hwa Han in Yonsei University College of Medicine for her advice on sample size calculation.
This research was supported by grants from the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (no. HI16C0451) and SNUBH Research Fund (no. 02-2015-030).
Compliance with ethical standards
The scientific guarantor of this publication is Kyoung Ho Lee.
Conflict of interest
One of the co-authors (Amar C. Dhanantwari) is an employee of Philips. He contributed to imaging processing regarding radiation dose simulation and manuscript editing, but did not interfere with the medical interpretation proposed in this study. Otherwise, there are no conflicts of interest to declare.
Statistics and biometry
One of the authors has significant statistical expertise.
Written informed consent was obtained from all subjects (patients) in this study.
Institutional Review Board approval was obtained.
• diagnostic study
• performed at one institution
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