Pediatric MDCT: Towards Assessing the Diagnostic Influence of Dose Reduction on the Detection of Small Lung Nodules

Li, Xiang; Samei, Ehsan; DeLong, David M.; Jones, Robert P.; Gaca, Ana Maria; Hollingsworth, Caroline L.; Maxfield, Charles M.; Colsher, James G.; Frush, Donald P.

doi:10.1016/j.acra.2009.01.028

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Volume 16, Issue 7 , Pages 872-880, July 2009

Pediatric MDCT:

Towards Assessing the Diagnostic Influence of Dose Reduction on the Detection of Small Lung Nodules

Medical Physics Graduate Program (X.L. E.S., J.G.C., D.P.F.), Duke Advanced Imaging Laboratories, Department of Radiology (X.L., E.S.), the Departments of Physics and Biomedical Engineering (E.S.), the Department of Biostatistics and Bioinformatics (D.M.D.), the School of Medicine (R.P.J.), and the Division of Pediatric Radiology, Department of Radiology (A.M.G., C.L.H., C.M.M., D.P.F.), Duke University, 2424 Erwin Road, Suite 302, Durham, NC 27705; and GE Healthcare, Waukesha, WI (J.G.C.). This work is partially funded by GE Healthcare (Waukesha, WI)

Received 30 September 2008; accepted 24 January 2009. published online 27 April 2009.

Rationale and Objectives

The purpose of this study was to evaluate the effect of reduced tube current (dose) on lung nodule detection in pediatric multidetector array computed tomography (MDCT).

Materials and Methods

The study included normal clinical chest MDCT images of 13 patients (aged 1–7 years) scanned at tube currents of 70 to 180 mA. Calibrated noise addition software was used to simulate cases as they would have been acquired at 70 mA (the lowest original tube current), 35 mA (50% reduction), and 17.5 mA (75% reduction). Using a validated nodule simulation technique, small lung nodules of 3 to 5 mm in diameter were inserted into the cases, which were then randomized and rated independently by three experienced pediatric radiologists for nodule presence on a continuous scale ranging from zero (definitely absent) to 100 (definitely present). The observer data were analyzed to assess the influence of dose on detection accuracy using the Dorfman-Berbaum-Mets method for multiobserver, multitreatment receiver-operating characteristic (ROC) analysis and the Williams trend test.

Results

The areas under the ROC curves were 0.95, 0.91, and 0.92 at 70, 35, and 17.5 mA, respectively, with standard errors of 0.02 and interobserver variability of 0.02. The Dorfman-Berbaum-Mets method and the Williams trend test yielded P values for the effect of dose of .09 and .05, respectively.

Conclusion

Tube current (dose) has a weak effect on the detection accuracy of small lung nodules in pediatric MDCT. The effect on detection accuracy of a 75% dose reduction was comparable to interobserver variability, suggesting a potential for dose reduction.

Key Words: Pediatric, MDCT, dose reduction, nodule simulation, noise simulation, receiver-operating characteristic, observer study