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Evaluating the Impact of Iterative Reconstruction for Three Major CT Vendors

Z Yang

J Chen1, Z Yang1*, E Samei2, O Christianson2, A Dima3, J Filliben3, A Peskin4, G Saiprasad5, E Siegel1, (1) University of Maryland School of Medicine, Baltimore, MD,(2) Duke University Medical Center, Durham, NC, (3) National Institute of Standards and Technology, Gaithersburg, MD, (4) National Institute of Standards and Technology, Boulder, CO, (5) University of Maryland Baltimore County, Baltimore, MD,

SU-C-217BCD-2 Sunday 1:30:00 PM - 2:15:00 PM Room: 217BCD

Various vendors have promoted iterative reconstruction as an effective way to reduce CT radiation dose while maintaining image quality. The purpose of our exhibit is to demonstrate the effectiveness of various vendor reconstruction approaches on image quality based on a multi-institutional study utilizing the ACR phantom as a source of quantitative analysis.

CT scans of the ACR CT QA phantom were acquired using three CT scanners (A: GE Discovery CT750 HD, B: Philips iCT, and C: Siemens FLASH). Images acquired at seven dose levels ranging from 1 to 20 mGy were reconstructed using both FBP and IR. The data acquisition was randomized and duplicated five times to reduce the effect of systematic variations.

The images were reconstructed utilizing the kernel of reconstruction recommended by each manufacturer for abdominal CT studies utilizing both filtered back projection and the vendor's iterative reconstruction techniques. The phantom images were quantitatively evaluated for a number of parameters that determined spatial and contrast resolution as well as signal to noise levels. The data were entered into a spreadsheet and subsequently into a statistical package for analysis.

The success of iterative reconstruction varied substantially among the three vendors for the low dose CT protocols but did have a positive impact on image quality. The positive impact of iterative reconstruction was greatest for the lowest dose studies. The specific differences will be discussed in detail.

In addition to subjective evaluation of image quality which can be affected by many parameters, it is also important to determine the impact of the newly developed CT iterative reconstruction algorithms in a quantitative manner utilizing phantoms. Our study suggests that the quantitative improvements in spatial resolution are modest. However, improvements in contrast to noise ratio are in the neighborhood of 35 to 58% depending on the exact implementation.

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