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Updated: Jun 5, 2026

X-ray Dose Reduction through Adaptive Exposure in Fluoroscopic Imaging
Published on: September 11, 2011
Extra Z-axis coverage at CT imaging resulting in excess radiation dose: frequency, degree, and contributory factors
Eric A Liao1, Leslie E Quint, Mitchell M Goodsitt
1Department of Radiology, University of Michigan Health System, Ann Arbor, MI 48109-5030, USA.
Objective:
To assess the degree of extra scanning beyond the prescribed anatomic boundaries for thoracic and body computed tomographic (CT) scans and to identify associated factors.
Methods:
For 442 consecutive chest, abdomen, and/or pelvis CT examinations, the length of extra scanning beyond the prescribed anatomic boundaries was determined. Examinations were grouped according to the locations/types of the prescribed boundaries and compared with regard to length of extra scanning.
Results:
Of 442 CT examinations, 438 (99%) included extraneous imaging, showing a mean excess scanning length of 43.2 mm per examination (range, 0-180 mm). Significantly more extraneous imaging was performed when soft tissue or vascular structures defined anatomic boundaries compared to when osseous (P < 0.001) or air/soft tissue interfaces (P < 0.0001) defined the boundaries. The average percent of total scan dose attributable to extra imaging was 8.64% to 10.38%.
Conclusions:
Computed tomographic scanning beyond the prescribed anatomic boundaries occurs commonly, resulting in moderate extra radiation dose.
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