Effect of radiation dose level on the detectability of pulmonary nodules in chest tomosynthesis
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To investigate the detectability of pulmonary nodules in chest tomosynthesis at reduced radiation dose levels.
Eighty-six patients were included in the study and were examined with tomosynthesis and computed tomography (CT). Artificial noise was added to simulate that the tomosynthesis images were acquired at dose levels corresponding to 12, 32, and 70 % of the default setting effective dose (0.12 mSv). Three observers (with >20, >20 and three years of experience) read the tomosynthesis cases for presence of nodules in a free-response receiver operating characteristics (FROC) study. CT served as reference. Differences between dose levels were calculated using the jack-knife alternative FROC (JAFROC) figure of merit (FOM).
The JAFROC FOM was 0.45, 0.54, 0.55, and 0.54 for the 12, 32, 70, and 100 % dose levels, respectively. The differences in FOM between the 12 % dose level and the 32, 70, and 100 % dose levels were 0.087 (p = 0.006), 0.099 (p = 0.003), and 0.093 (p = 0.004), respectively. Between higher dose levels, no significant differences were found.
A substantial reduction from the default setting dose in chest tomosynthesis may be possible. In the present study, no statistically significant difference in detectability of pulmonary nodules was found when reducing the radiation dose to 32 %.
• A substantial radiation dose reduction in chest tomosynthesis may be possible.
• Pulmonary nodule detectability remained unchanged at 32 % of the effective dose.
• Tomosynthesis might be performed at the dose of a lateral chest radiograph.
KeywordsThoracic radiography Tomosynthesis Adults Solitary pulmonary nodule Radiation dosage
Jack-knife alternative free-response receiver operating characteristics
Lesion localisation fraction
Non-lesion localisation fraction
The scientific guarantor of this publication is Magnus Båth. The authors of this manuscript declare relationships with the following companies: Jenny Vikgren and Marianne Boijsen declare financial activities not related to the present article as speakers for GE (2013). Other relationships: None declared. The remaining authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article. This study has received funding by grants from the Swedish Research Council [2011/488, 2013-3477], the Swedish Radiation Safety Authority [2008/2232, 2009/1689, 2010/4363, 2012/2021, 2013/2982], the King Gustav V Jubilee Clinic Cancer Research Foundation, the Swedish Federal Government under the LUA/ALF agreement [ALFGBG-136281] and the Health & Medical Care Committee of the Region Västra Götaland [VGFOUREG-12046, VGFOUREG-27551, VGFOUREG-81341]. Institutional Review Board approval was obtained. Written informed consent was obtained from all subjects (patients) in this study. Some study subjects or cohorts have been previously reported in Svalkvist et al. “Evaluation of an improved method of simulating lung nodules in chest tomosynthesis”. Acta Radiol. 2012;53:874–84. Five of the 86 patients included in the present study have previously been included in the study by Svalkvist et al. In that study, simulated nodules were inserted into the images and the appearance of them was thereby altered. The inclusion of them in the present study was therefore considered justified. Methodology: prospective, experimental, performed at one institution.
The authors would like to acknowledge Dev P Chakraborty, Department of Radiology, University of Pittsburgh, PA, for consulting regarding the JAFROC analysis and Christina Söderman, Department of Radiation Physics, Sahlgrenska Academy at University of Gothenburg, Sweden, for assistance in controlling the detection study.
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