Reduced radiation exposure for face transplant surgical planning computed tomography angiography

Abstract

Objective: To test the hypothesis that wide area detector face transplant surgical planning CT angiograms with simulated lower radiation dose and iterative reconstruction (AIDR3D) are comparable in image quality to those with standard tube current and filtered back projection (FBP) reconstruction.

Materials and methods: The sinograms from 320-detector row CT angiography of four clinical candidates for face transplantation were processed utilizing standard FBP, FBP with simulated 75, 62, and 50% tube current, and AIDR3D with corresponding dose reduction. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured at muscle, fat, artery, and vein. Image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale.

Results: Compared to FBP, the median SNR and CNR for AIDR3D images were higher at all sites for all 4 different tube currents. The AIDR3D with simulated 50% tube current achieved comparable SNR and CNR to FBP with standard dose (median muscle SNR: 5.77 vs. 6.23; fat SNR: 6.40 vs. 5.75; artery SNR: 43.8 vs. 45.0; vein SNR: 54.9 vs. 55.7; artery CNR: 38.1 vs. 38.6; vein CNR: 49.0 vs. 48.7; all p-values >0.19). The interobserver agreement in the image quality score was good (weighted κ = 0.7). The overall score and the scores for smaller arteries were significantly lower when FBP with 50% dose reduction was used. The AIDR3D reconstruction images with 4 different simulated doses achieved a mean score ranging from 3.68 to 3.82 that were comparable to the scores from images reconstructed using FBP with original dose (3.68-3.77).

Conclusions: Simulated radiation dose reduction applied to clinical CT angiography for face transplant planning suggests that AIDR3D allows for a 50% reduction in radiation dose, as compared to FBP, while preserving image quality.

Conflict of interest statement

Competing Interests: The authors have read the journal's policy and have the following conflicts. Dr. Rybicki has research agreements with Toshiba Medical Systems Corporation that are unrelated to this project. Mr. Schultz is an employee of Toshiba Medical Systems Corporation. There are no patents and no products in development to declare. This research was conducted using standard medical imaging devices from Toshiba. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1. Boxplots of signal-to-noise ratio (SNR) for each reconstruction.

A- Muscle. B- Fat. C- Artery. D- Vein.

Figure 2. Boxplots of contrast-to-noise ratio (CNR) of each reconstruction.

A- Artery. B- Vein.

Figure 3. Representative images with FBP and AIDR3D reconstructions.

Image noise increases on images reconstructed using FBP with original tube current (A, D) and simulated 50% dose reduction (B, E), especially around the metal in the mandible (A, B), while images reconstructed using AIDR3D with simulated 50% dose reduction (C, F) achieve reduced artifacts and noise. The right lingual artery (D–F) is poorly delineated in the image with FBP and simulated 50% dose reduction (E).

Figure 4. Representative images with FBP and AIDR3D reconstructions.

The branch of the left facial artery (arrow) is clearly depicted on the image reconstructed using AIDR3D with simulated 50% dose reduction (C), while it is obscured on the image reconstructed using FBP with original dose (A) and is hard to detect on the image using FBP with simulated 50% dose reduction (B) due to streak artifacts.