James P. Earls MD, Presenter: Research support, General Electric Company Speakers Bureau, General Electric Company

Micah Lindsey, Abstract Co-Author: Nothing to Disclose

Elise L. Berman MD, Abstract Co-Author: Nothing to Disclose

Charlene Andrea Curry MD, Abstract Co-Author: Nothing to Disclose

Bruce Andrew Urban MD, Abstract Co-Author: Nothing to Disclose

Robert Jennings RT, Abstract Co-Author: Nothing to Disclose

Judy L. Lane, Abstract Co-Author: Nothing to Disclose

00030490-DMT et al, Abstract Co-Author: Nothing to Disclose

  Adaptive Statistical Iterative Reconstruction (ASIR) utilizes statistical modeling to reduce image noise and increase the signal to noise ratio of CT exams. This allows for the use of reduced tube current as compared to studies reconstructed with filtered back projection (FBP) algorithms.  The purpose of this study was to directly compare studies performed using ASIR and FBP in the same patient.

We evaluated radiation doses in 2078 consecutive CT examinations performed on two ASIR equipped systems, a 64-row HD750 CT (n=1776) and a 64-row VCT XTe (n=302)(GE Healthcare Chalfont UK). 431 (19.8%) patients had a prior matched FBP reconstructed CT exam in our PACS system available for comparison. ASIR was used on all clinical studies, and FBP was used on all prior exams. Dose reduction was achieved by lower tube current as controlled by increasing the exam CT noise index (NI) over that used for the FBP studies.  Patient and scan parameters and radiation doses were evaluated and compared. Radiation doses were calculated from the reported scan dose-length product (DLP) estimated by the CT system.

The mean DLP of ASIR reconstructed studies was 616 mGy-cm, 36.7% lower than 974 mGy-cm for matched FBP studies (p<.05). All ASIR reconstructed exams were diagnostic. The mean dose of cardiac CTA was 899 and 165 mGy-cm for ASIR retrospective and prospective gated exams, 36 and 33% lower compared with 1410 and 243 mGy-cm for FSP, respectively (p<.05). ASIR exams of the chest, combined abdomen and pelvis, and combined chest abdomen and pelvis had DLPs of 309, 812, and 1021 mGy-cm; 32%, 45%, and 37% lower than FBP exams (p<.05). ASIR scans of the cervical and lumbar spine were 791 and 879 mGy-cm, 41 and 33% lower than FBP exams (<.05). ASIR scans of the brain and sinus were 550 and 129 mGy-cm, 26 and 42% lower than matched FBP studies )(p<.05).

In direct intra-patient comparison, use of ASIR allows for significant dose reduction for the most commonly performed CT exams as compared to FBP. Further evaluation of optimal current reduction, noise index, and amount of ASIR reconstruction is needed.

Adaptive Statistical Iterative Reconstruction is a promising technique that allows for substantial reduction in the dose of the most commonly performed CT exams.

Earls, J, Lindsey, M, Berman, E, Curry, C, Urban, B, Jennings, R, Lane, J, et al, 0, Estimated Radiation Dose of CT Exams Reconstructed Using Adaptive Statistical Iterative Reconstruction Compared with Filter Back Projection: Comparison of Patients with Multiple Exams.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8010927.html