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Detection of Simulated Nodules on Clinical Radiographs: Dose Reduction at Digital Posteroanterior Chest Radiography¹

¹ From the Departments of Radiology (L.J.M.K., W.J.H.V., J.P.A.v.D., J.G.) and Medical Statistics (B.J.A.M.), C2S, Leiden University Medical Center, Albinusdreef 2, 2333 ZA Leiden, the Netherlands. From the 2005 RSNA Annual Meeting. Received August 8, 2005; revision requested October 17; revision received November 14; accepted December 12; final version accepted February 3, 2006. Address correspondence to L.J.M.K. (e-mail: l.j.m.kroft{at}lumc.nl).

Purpose: To determine to what extent dose reduction results in decreased detection of simulated nodules on patient digital posteroanterior (PA) chest radiographs.

Materials and Methods: Raw data from 20 clinical digital PA chest images that were reported as having normal findings and that were obtained with a slot-scan charge-coupled device system were used. For research protocol that concerns data with patient identities concealed, institutional review board approval is not required. One hundred twenty nodules varying in size and signal intensity were digitally simulated and added to the chest images. Hard copies were printed to represent a 100% dose and, by adding noise, to represent simulated patient doses of 50%, 25%, and 12%. Four radiologists reviewed images. Each lesion was registered as "detected" or "not detected." A semiparametric logistic regression model was used for statistical analysis.

Results: The decrease in radiation dose from 100% to 50%, 25%, or 12% had no effect on lesion detection in the lungs. The decrease in radiation dose had an effect on lesion detection in the mediastinum, as probabilities deteriorated from the 100% dose to the 50%, 25%, and 12% dose with each step. Probabilities of smaller detection rates when compared with that of the reference category (100% dose) were 0.97 (95% confidence interval [CI]: –0.86, 0.012) for the 50% dose, 1 (CI: –0.59, –0.61) for the 25% dose, and 1 (CI: –2.41, –1.22) for the 12% dose. CIs for the effects were on the log(odds). Detection probability decreased with smaller and lower signal intensity lesions.

Conclusion: At clinical digital radiography, dose reduction resulted in decreased observer detection of simulated nodules in the mediastinum but not in the lungs.

© RSNA, 2006

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				L J M Kroft, W J H Veldkamp, B J A Mertens, J-P A van Delft, and J Geleijns Dose reduction in digital chest radiography and perceived image quality Br. J. Radiol., December 1, 2007; 80(960): 984 - 988. [Abstract] [Full Text] [PDF]