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

Maral Mirzai,Carin Meltzer,Jenny Vikgren,Rauni Rossi Norrlund,Bengt Gottfridsson,Åse Johnsson,Magnus Båth,Angelica Svalkvist

doi:10.1016/j.acra.2020.05.041

Maral Mirzai, Carin Meltzer + Show 6 more

Open Access

https://doi.org/10.1016/j.acra.2020.05.041

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Abstract

To evaluate the effect of reduction in effective dose on the reproduction of anatomical structures in chest tomosynthesis (CTS). 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 (AUCVGC) provides a measure of the difference between the ratings, where an AUCVGC of 0.5 indicates no difference. The dose reductions resulted in inferior reproduction of structures compared to the original dose level (AUCVGC <0.5). Structures in the central region of the lung obtained the lowest AUCVGC for each dose level whereas the reproduction of structures in the parenchyma was least affected by the dose reduction. 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.

Highlights

Materials and Methods: Twenty-four chest tomosynthesis (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 dose reductions resulted in inferior reproduction of structures compared to the original dose level (AUCVGC
It is important to consider the clinical purpose of the CTS examinations before deciding on a permanent dose reduction

Summary

Introduction

The increased diagnostic information in tomosynthesis has shown to improve both sensitivity and specificity for the detection of pulmonary nodules, resulting in higher diagnostic accuracy than CXR [5,9]. As the radiation dose to patients from a CTS examination is slightly higher than from a CXR examination, several studies have investigated the performance of CTS at lower dose levels (10À14). Another study, based on clinical CTS images, used simulated dose reduction to assess nodule detectability at various dose levels. The effect of dose reduction on other important clinical tasks, such as nodule size measurements, has been assessed with results showing that precision and accuracy of nodule size measurements are unaffected when reducing the dose to 50% of the original dose [13]. The purpose of the present study was to evaluate to what extent a reduction in effective dose affects the reproduction of important anatomical structures in CTS images

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