The most common cause of repeat exposures is positioning error
Key takeaways
- Positioning error leads in the digital reject audits we opened.
- The share varies by site and category grouping: about 49% to 79% where positioning is reported alone.
- Motion ran 5% to 11% and exposure 4.1% to 14% in the audits tabled below.
- Digital rarely needs a repeat for technique alone, but it doesn't fix positioning.
Positioning error. Every digital reject audit we opened found it to be the top reason, ahead of motion and exposure. A 2021 Australian audit reports that almost all relevant digital studies agree.
What do the studies show?
| Study | Setting | Reject rate | Positioning share of rejects | Motion | Exposure |
|---|---|---|---|---|---|
| New Zealand, 2023 | Inpatient and ED department | 7.86% | 79.4% | 5.8% | 5.0% |
| New Zealand, 2023 | Outpatient department | 5.91% | 77.3% | 10.5% | 4.1% |
| Australia, 2020 | Emergency department | 9% | 49%, plus 21% anatomy cut-off | 5% | 5% under, about 0.2% over |
| US, 2009 (CR systems) | University hospital | 4.4% | 56%, with anatomy cut-off | 7% | 13% |
| US, 2009 (CR systems) | Community hospital | 4.9% | 45%, with anatomy cut-off | 11% | 14% |
These numbers don’t compare cleanly. Sites define categories differently, and some fold anatomy cut-off into positioning. Treat them as a pattern, not a rate to memorize.
Why does digital make positioning stand out?
Digital images can be adjusted after acquisition, so almost all retakes for technique selection go away. Poor positioning isn’t fixed that way (Sherer 8th ed., PDF p.572). The Australian audit authors describe the same shift: exposure was the leading reason with conventional imaging, and positioning has been since digital arrived.
An overexposed digital image is still extra dose, even if software hides it. Our kVp vs mAs guide covers when a repeat is justified.
For screen-film, Bushong names improper positioning and poor technique together as the main causes (11th ed., PDF p.610). We found no source for the claim, made on an earlier version of this page, that motion once led.
What does a repeat analysis do?
It sorts rejected images by reason, such as mispositioning, centering, motion and collimation, then shows a department what to retrain. On digital systems, retaken images may not be saved automatically, so a department needs a policy to recover them for review (Sherer, PDF pp.639-640).
Where does this sit on the registry?
ARRT®‘s 2027 outline names repeats in its heading, “Minimizing Patient Exposure and Repeats”, under Radiation Protection. The 2022 heading is “Minimizing Patient Exposure”. Radiation Protection carries 29 of the 200 scored questions today and 25 from March 1, 2027. ARRT doesn’t publish a cause breakdown, so no percentage here is an exam fact.
Read the Radiation Protection guide and the protection chapter, then try the protection practice questions. To work on the cause itself, start with positioning foundations. The Image Production guide has a troubleshooting table.
Frequently asked questions
What is the most common cause of repeat radiographs?
Positioning error. Published digital reject audits found it to be the top reason, at about 49% to 79% of rejects where positioning is reported alone, and 45% to 56% in a US study that merged in anatomy cut-off.
Is motion the most common reason for repeats?
Not in the audits we opened. Motion ran 5.8% to 10.5% of rejects in two New Zealand departments and 7% to 11% at two US hospitals, and 5% in an Australian emergency department.
Why don't exposure errors cause more repeats on digital systems?
Image contrast and brightness can be adjusted after acquisition, so digital removes the need for almost all retakes caused by technique selection. It can't correct a poorly positioned part.
Sources
Found an error? Email [email protected] with the page and the source.
- Bantas G, Sweeney RJ, Mdletshe S. Digital radiography reject analysis: a comparison between two radiology departments in New Zealand. J Med Radiat Sci, 2023;70(2):137-144 Journal
- Atkinson S, Neep M, Starkey D. Reject rate analysis in digital radiography: an Australian emergency imaging department case study. J Med Radiat Sci, 2020;67(1):72-79 Journal
- Foos DH, et al. Digital radiography reject analysis: data collection methodology, results, and recommendations from an in-depth investigation at two hospitals. J Digit Imaging, 2009;22(1):89-98 Journal
- Digital radiography reject analysis of examinations with multiple rejects: an Australian emergency imaging department clinical audit. J Med Radiat Sci, 2021;68(3):245-252 Journal
- ARRT Radiography Examination Content Specifications, 2022 and March 1, 2027, p.1 and p.5 (Minimizing Patient Exposure and Repeats) Official
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