Sarabjeet Singh MD, Presenter: Nothing to Disclose

Sarvenaz Pourjabbar MD, Abstract Co-Author: Nothing to Disclose

Ranish Deedar Ali Khawaja MBBS, MD, Abstract Co-Author: Nothing to Disclose

Atul Padole MD, Abstract Co-Author: Nothing to Disclose

Garry Choy MD, MS, Abstract Co-Author: Nothing to Disclose

Mannudeep K. S. Kalra MD, Abstract Co-Author: Faculty, General Electric Company

Mischa Woisetschlager MD, PhD, Abstract Co-Author: Nothing to Disclose

Nils Dahlstrom MD, PhD, Abstract Co-Author: Nothing to Disclose

Anders Persson MD, PhD, Abstract Co-Author: Nothing to Disclose

Assessment of the effect of Sinogram Affirmed iterative reconstruction (Safire) and Filtered Back Projection (FBP) technique on abdominal CT examination acquired at 200 mAs, 100 mAs, and 50 mAs.

24 patients (mean age 64 ± 14 years, M:F 10 :14) gave informed consent for an IRB approved prospective study for additional research images through the abdomen on 128 slice MDCT (Siemens Flash) at 100 mAs and 50 mAs over a scan length of 10 cm using combined modulation technique. Images through entire abdomen were acquired at 200 mAs. The 50 and 100 mAs datasets were each reconstructed with FBP and four settings of Safire (S1, S2, S3, S4). The FBP 200 mAs images were compared side-by-side with FBP and Safire images from 50 and 100 mAs. The number and location of lesions, lesion size, lesion conspicuity, visibility of small structures were assessed by two experienced abdominal radiologists. The diagnostic acceptability was recorded on a four point scale (1= fully acceptable, 4= unacceptable). Objective noise and HU values were measured in liver and the descending aorta. The noise power spectrum was analyzed for FBP and different Safire settings.

A total of 43 lesions were detected on both FBP and Safire images. Minor blocky or pixilated appearance of 50 and 100 mAs images was noted at S3 and S4 Safire settings. No significant artifacts were noted on S1 and S2 Safire images. Image noise was suboptimal in FBP 100 and 50 mAs images, whereas noise was acceptable with S1, S2 and S3 and better than average on S4 setting. Safire could render 100 mAs images as fully acceptable for diagnostic confidence but 50 mAs Safire images were deemed to have lower diagnostic confidence compared to 200 mAs. As compared to 50 mAs FBP, objective noise was lower by 22.8% (22.9/29.7) on S1, 35% (19.3/29.7) on S2, 44.3% on S3 (16.7/29.3) and 54.8% (13.4/29.7) on S4 (p<0.001). Noise power spectrum analysis showed that Safire retains the noise power spectral signature similar to FBP, in spite of progressive noise reduction with higher iteration settings

Safire enabled reconstruction provides diagnostically acceptable abdominal CT images acquired at 100 mAs (50% reduced dose) but 50 mAs Safire images are not completely diagnostically acceptable despite reduced image noise

Radiation dose reduction down to 100 mAs is achievable with Safire enabled abdominal CT examinations

Singh, S, Pourjabbar, S, Khawaja, R, Padole, A, Choy, G, Kalra, M, Woisetschlager, M, Dahlstrom, N, Persson, A, Prospectively Acquired Low Doses in Abdominal CT and Role of Sinogram Affirmed Iterative REconstruction (Safire).  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13044421.html