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Acad Radiol. 2017 Jul;24(7):876-890. doi: 10.1016/j.acra.2016.12.017. Epub 2017 Mar 2.

Estimation of Observer Performance for Reduced Radiation Dose Levels in CT: Eliminating Reduced Dose Levels That Are Too Low Is the First Step.

Author information

1
Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. Electronic address: fletcher.joel@mayo.edu.
2
Department of Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905.
3
Department of Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
4
Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota.
5
Biostatistics Consulting, LLC, Kensington, Maryland.

Abstract

RATIONALE AND OBJECTIVES:

This study aims to estimate observer performance for a range of dose levels for common computed tomography (CT) examinations (detection of liver metastases or pulmonary nodules, and cause of neurologic deficit) to prioritize noninferior dose levels for further analysis.

MATERIALS AND METHODS:

Using CT data from 131 examinations (abdominal CT, 44; chest CT, 44; head CT, 43), CT images corresponding to 4%-100% of the routine clinical dose were reconstructed with filtered back projection or iterative reconstruction. Radiologists evaluated CT images, marking specified targets, providing confidence scores, and grading image quality. Noninferiority was assessed using reference standards, reader agreement rules, and jackknife alternative free-response receiver operating characteristic figures of merit. Reader agreement required that a majority of readers at lower dose identify target lesions seen by the majority of readers at routine dose.

RESULTS:

Reader agreement identified dose levels lower than 50% and 4% to have inadequate performance for detection of hepatic metastases and pulmonary nodules, respectively, but could not exclude any low dose levels for head CT. Estimated differences in jackknife alternative free-response receiver operating characteristic figures of merit between routine and lower dose configurations found that only the lowest dose configurations tested (ie, 30%, 4%, and 10% of routine dose levels for abdominal, chest, and head CT examinations, respectively) did not meet criteria for noninferiority. At lower doses, subjective image quality declined before observer performance. Iterative reconstruction was only beneficial when filtered back projection did not result in noninferior performance.

CONCLUSION:

Opportunity exists for substantial radiation dose reduction using existing CT technology for common diagnostic tasks.

KEYWORDS:

CT; iterative reconstruction; observer performance; radiation dose; radiation dose reduction

PMID:
28262519
PMCID:
PMC6481673
DOI:
10.1016/j.acra.2016.12.017
[Indexed for MEDLINE]
Free PMC Article

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