The Effect of Dose Reduction on Overall Image Quality in Clinical Chest Tomosynthesis

Abstract

Rationale and Objectives: To evaluate the effect of reduction in effective dose on the reproduction of anatomical structures in chest tomosynthesis (CTS). Materials and Methods: Twenty-four CTS examinations acquired at exposure settings resulting in an effective dose of 0.12 mSv for an average sized patient were included in the study. The examinations underwent simulated dose reduction to dose levels corresponding to 32%, 50%, and 70% of the original dose using a previously described and validated method. The image quality was evaluated by five thoracic radiologists who rated the fulfillment of specified image quality criteria in a visual grading study. The ratings for each image quality criterion in the dose-reduced images were compared to the corresponding ratings for the full-dose examinations using visual grading characteristics (VGC) analysis. The area under the resulting VGC curve (AUC VGC) provides a measure of the difference between the ratings, where an AUC VGC of 0.5 indicates no difference. Results: The dose reductions resulted in inferior reproduction of structures compared to the original dose level (AUC VGC <0.5). Structures in the central region of the lung obtained the lowest AUC VGC for each dose level whereas the reproduction of structures in the parenchyma was least affected by the dose reduction. Conclusion: Although previous studies have shown that dose reduction in CTS is possible without affecting the performance of certain clinical tasks, the reproduction of normal anatomical structures is significantly degraded even at small reductions. It is therefore important to consider the clinical purpose of the CTS examinations before deciding on a permanent dose reduction.