Abstract
To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.
Highlights
Cardiac computed tomography angiography (CTA) is an established non-invasive method to evaluate the coronary arteries [1] with a high negative predictive value to exclude significant coronary artery disease [2]
There was no significant difference in the CT number among the 5 tissue ROIs for both FBP50 % and AIDR50 %, (20.5 ± 9.0 vs. 18.3 ± 9.2, p \ 0.0001)
Image noise of AIDR50 % was lower than the filtered back projection (FBP) group within the aorta (31.2 ± 8.0 vs. 36.8 ± 12.7, p \ 0.0001), fat (20.1 ± 5.7 vs. 21.3 ± 7.4, p = 0.01), muscle (20.8 ± 5.6 vs. 22.2 ± 7.7, p = 0.004) and liver (27.9 ± 6.3 vs. 34.3 ± 10.4, p \ 0.0001)
Summary
Cardiac computed tomography angiography (CTA) is an established non-invasive method to evaluate the coronary arteries [1] with a high negative predictive value to exclude significant coronary artery disease [2]. Iterative reconstruction has been applied to 320 9 0.5 mm detector row cardiac CT with a reduction of image noise [17, 18]. These studies did not suggest a specific reduction of patient radiation exposure. An assessment of the benefits and potential tradeoffs of applying iterative reconstruction for clinical coronary CTA imaging be estimated, without repeating clinical scanning, by mathematically adding CT noise to the sinogram data to simulate reductions in tube current. The purpose of this study is to test the hypothesis that the AIDR3D reconstruction will (a) reduce the magnitude of noise as measured by clinical regions of interest and (b) maintain image quality for clinical coronary CTA images reconstructed with a simulated 50 % reduction in tube current
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