Robert Gene Paden, Presenter: Nothing to Disclose

William Pavlicek PhD, Abstract Co-Author: Nothing to Disclose

Mary Beth Peter MS, Abstract Co-Author: Nothing to Disclose

Thomas Frederick Boltz BS, Abstract Co-Author: Nothing to Disclose

Kyung-Kook Park MS, Abstract Co-Author: Nothing to Disclose

David A. Langan PhD, Abstract Co-Author: Employee, General Electric Company

To evaluate the ability of ASIR to provide equivalent Head and Body image quality at one-half the radiation dose of conventional CT with filtered back projection (FBP).

American College of Radiology (ACR) Phantom scans were performed on a Lightspeed VCT and a Lightspeed CT500 HD (General Electric, Waukesha, WI). Standard helical adult abdomen and adult axial head protocols with measured CTDI values of 25 mGy and 66 mGy were acquired on both scanners. On the CT500 HD, mA was reduced by 50% to create images at 12.5 mGy and 33 mGy for abdomen and head protocols, roughly one-half the dose of current protocols. FBP was used to reconstruct images on all data sets. ASIR processing was applied to the second data set acquired at one-half mA. Images appropriate for accreditation submission were qualitatively evaluated using ACR criteria. Quantitative measurement of image signal-to-noise (SNR) was performed on FBP- reconstructed images, and one-half dose ASIR-reconstructed images.

CT scans with one-half dose reconstructed with 30% ASIR demonstrated a standard deviation increase of 4%. SNR (module 1 acrylic insert) calculated: 28.3/21.8/26.8 for helical abdomen scan at 25 mGy FBP, 12.5 mGy FBP, and 12.5 mGy 30% ASIR. The full dose FBP and half dose ASIR images were judged as equivalent using accreditation criteria. CT number, water vs. kVp, and uniformity were all appropriate values. For low contrast detail, 30% ASIR images were qualitatively graded to be passing for a head protocol acquired at 33 mGy, and a 12.5 mGy abdomen protocol. For high contrast resolution, 30% ASIR images passed ACR criteria for a 12.5 mGy abdomen protocol. Reduced mA scans were processed with 100% show a 70% decrease in standard deviation. SNR calculated: 24.2/16.1/89.0 for axial scan at 66 mGy FBP, 33 mGy FBP, and 33 mGy 100% ASIR.  

ASIR reduced radiation dose (50%) without loss of image quality in phantom images as compared to FBP. Dose reductions of one-half for all standard head and body protocols appear quite reasonable when reconstructed with ASIR.

ASIR has the potential for dramatic lowering of patient and population dose for every x-ray computed tomography examination – head and body.

Paden, R, Pavlicek, W, Peter, M, Boltz, T, Park, K, Langan, D, Adaptive Statistical Iterative Reconstruction (ASIR) for CT Dose Reduction of Head and Body Examinations: A Phantom Study.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6017211.html