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Proceedings Paper

Iterative reconstruction in image space (IRIS) and lesion detection in abdominal CT
Author(s): Sameer Tipnis; Ashok Ramachandra; Walter Huda; Andrew Hardie; Joseph Schoepf; Philip Costello; Thomas Flohr; Martin Sedlmair
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Paper Abstract

The purpose of this study was to compare lesion detection in images reconstructed using standard filtered back projection (FBP) with those reconstructed using a new CT reconstruction algorithm called Iterative Reconstruction in Image Space (IRIS). Detection performance was experimentally measured using a 2- AFC software package that computes the lesion intensity corresponding to a detection accuracy of 92% (i.e., I92%). Abdominal images were acquired on a Siemens Somaton Definition Flash CT scanner and reconstructed at four slice thickness values ranging from 1.5 mm to 10 mm. Detection of three lesion sizes was investigated, whose diameters ranged from 5 mm to 10 mm. AFC experiments were performed using FBP and IRIS reconstructed images that were presented to observers in a random manner. For any lesion in a given image, we obtained an Enhancement Factor (EF) defined as the I92% using FBP divided by the corresponding I92% using IRIS. In 9 out of 12 paired results, EF values were significantly greater than 1.0, and in the remaining three cases, EF values were approximately 1.0. EF was independent of CT image slice thickness, with an average value of 1.17 ± 0.12. Values of EF increased with decreasing lesion size, and were about 20% greater for 5 mm lesions than 10 mm lesions. The results of this pilot study show that IRIS improved lesion detection compared to conventional FBP, with an average increase in signal to noise ratio of 17%. For the smallest lesions, improvements in signal to noise ratio approached 30%. Our results suggest that radiation dose reductions of one third might be achievable for abdominal imaging without any loss in signal to noise ratio.

Paper Details

Date Published: 22 March 2010
PDF: 12 pages
Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76222K (22 March 2010); doi: 10.1117/12.843787
Show Author Affiliations
Sameer Tipnis, Medical Univ. of South Carolina (United States)
Ashok Ramachandra, Medical Univ. of South Carolina (United States)
Walter Huda, Medical Univ. of South Carolina (United States)
Andrew Hardie, Medical Univ. of South Carolina (United States)
Joseph Schoepf, Medical Univ. of South Carolina (United States)
Philip Costello, Medical Univ. of South Carolina (United States)
Thomas Flohr, Siemens Medical Solutions GmbH (Germany)
Martin Sedlmair, Siemens Medical Solutions GmbH (Germany)


Published in SPIE Proceedings Vol. 7622:
Medical Imaging 2010: Physics of Medical Imaging
Ehsan Samei; Norbert J. Pelc, Editor(s)

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