Korean J Radiol.  2014 Apr;15(2):195-204. 10.3348/kjr.2014.15.2.195.

Adaptive Iterative Dose Reduction Algorithm in CT: Effect on Image Quality Compared with Filtered Back Projection in Body Phantoms of Different Sizes

• Kim M
• Lee JM
• Yoon JH
• Son H
• Choi JW
• Han JK
• Choi BI

• KMID: 1705573
• DOI: http://doi.org/10.3348/kjr.2014.15.2.195

Abstract

OBJECTIVE
To evaluate the impact of the adaptive iterative dose reduction (AIDR) three-dimensional (3D) algorithm in CT on noise reduction and the image quality compared to the filtered back projection (FBP) algorithm and to compare the effectiveness of AIDR 3D on noise reduction according to the body habitus using phantoms with different sizes.
MATERIALS AND METHODS
Three different-sized phantoms with diameters of 24 cm, 30 cm, and 40 cm were built up using the American College of Radiology CT accreditation phantom and layers of pork belly fat. Each phantom was scanned eight times using different mAs. Images were reconstructed using the FBP and three different strengths of the AIDR 3D. The image noise, the contrast-to-noise ratio (CNR) and the signal-to-noise ratio (SNR) of the phantom were assessed. Two radiologists assessed the image quality of the 4 image sets in consensus. The effectiveness of AIDR 3D on noise reduction compared with FBP were also compared according to the phantom sizes.
RESULTS
Adaptive iterative dose reduction 3D significantly reduced the image noise compared with FBP and enhanced the SNR and CNR (p < 0.05) with improved image quality (p < 0.05). When a stronger reconstruction algorithm was used, greater increase of SNR and CNR as well as noise reduction was achieved (p < 0.05). The noise reduction effect of AIDR 3D was significantly greater in the 40-cm phantom than in the 24-cm or 30-cm phantoms (p < 0.05).
CONCLUSION
The AIDR 3D algorithm is effective to reduce the image noise as well as to improve the image-quality parameters compared by FBP algorithm, and its effectiveness may increase as the phantom size increases.

Keyword

Adaptive iterative dose reduction; CT, phantom study; Body sizes

MeSH Terms

*Algorithms
Animals
Body Size
Image Processing, Computer-Assisted/*methods
*Phantoms, Imaging/standards
Radiation Dosage
Signal-To-Noise Ratio
Subcutaneous Fat, Abdominal/*radiography
Swine
Tomography, X-Ray Computed/*methods

Figure

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  Fig. 1 Images of three phantoms with different thicknesses of subcutaneous fat: 24-cm-diameter phantom (left); 30-cm-diameter phantom (middle); and 40-cm-diameter phantom (right).

• 

  Fig. 2 Region of interest circles drawn for quantitative analysis of phantom study on CT image of 40-cm phantom reconstructed with filtered back projection at tube current time product of 200 mAs.

• 

  Fig. 3 CT image of module 1 of 40-cm phantom reconstructed with adaptive iterative dose reduction three-dimensional standard mode at tube current time product of 180 mAs, showing alignment line (arrows).

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  Fig. 4 CT images of 40-cm phantom scanned with tube current time product of 180 mAs reconstructed with filtered back projection (A), adaptive iterative dose reduction three-dimensional mild (B), standard (C), and strong modes (D).

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