Katharine Grant PhD, Presenter: Employee, Siemens AG

Kelly G Han MD, Abstract Co-Author: Speakers Bureau, Siemens AG

Jana L. Lindberg RT(R), Abstract Co-Author: Nothing to Disclose

Martin Ulrich Sedlmair MS, Abstract Co-Author: Employee, Siemens AG

Thomas G. Flohr PhD, Abstract Co-Author: Employee, Siemens AG

John R. Lesser MD, Abstract Co-Author: Speakers Bureau, Siemens AG Research grant, Siemens AG

Pediatric patients are at highest risk for long term effects of radiation exposure. Low dose imaging techniques can result in reduced image quality, due to increased image noise. The purpose of this study is to evaluate a new iterative reconstruction prototype in pediatric cardiac CT image sets to determine the effect on noise and image quality; and to assess the possibility for further prospective dose reduction to the pediatric patient population.

55 pediatric image sets (age: 1 day to 18 years) obtained on a 128 slice Dual Source CT system (Definition Flash, Siemens) were evaluated. For each data set, images were reconstructed at a slice thickness of 0.6 mm, both with (I36 kernel) and without (B36 kernel) the iterative reconstruction algorithm – Sinogram Affirmed Iterative Reconstruction (SAFIRE, Siemens AG). Quantitative image quality (contrast, noise, contrast/noise ratio, signal/noise ratio) and qualitative image quality were determined for both the original and the iterative reconstruction data sets, which were then compared. Data was analyzed as median and range, and reconstruction techniques were compared using the Wilcoxon Signed Ranks Test.

The contrast level did not differ between reconstruction techniques, but there was a 35% decrease in noise in the SAFIRE reconstructed images. Additionally, there was a median contrast/noise ratio increase of 51% with a 53% increase in signal to noise ratio for the SAFIRE images when compared to the original dataset reconstruction. The differences in noise, contrast to noise ratio, signal to noise ratio were all statistically significant (p value < .001). Image noise and noise texture were significantly improved (p < 0.001). Diagnostic confidence was excellent, and similar with both reconstruction algorithms (p = 1) and image sharpness was unaffected (p <= 0.3125).

The assessed iterative reconstruction algorithm significantly reduces image noise in low dose pediatric CT datasets and improves the qualitative assessment of noise and noise texture, without affecting diagnostic confidence.

The use of this iterative reconstruction algorithm may allow for a significant prospective dose reduction to the pediatric patient population in the future without subsequent loss of image quality.

Grant, K, Han, K, Lindberg, J, Sedlmair, M, Flohr, T, Lesser, J, Assessment of an Iterative Reconstruction Algorithm in Low Dose Pediatric Cardiac CT.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11009349.html