Iterative reconstruction in image space (IRIS) and lesion detection in abdominal CT

Sameer Tipnis; Ashok Ramachandra; Walter Huda; Andrew Hardie; Joseph Schoepf; Philip Costello; Thomas Flohr; Martin Sedlmair

doi:10.1117/12.843787

22 March 2010 Iterative reconstruction in image space (IRIS) and lesion detection in abdominal CT

Sameer Tipnis, Ashok Ramachandra, Walter Huda, Andrew Hardie, Joseph Schoepf, Philip Costello, Thomas Flohr, Martin Sedlmair

Author Affiliations +

Proceedings Volume 7622, Medical Imaging 2010: Physics of Medical Imaging; 76222K (2010) https://doi.org/10.1117/12.843787
Event: SPIE Medical Imaging, 2010, San Diego, California, United States

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.

Citation Download Citation

Sameer Tipnis, Ashok Ramachandra, Walter Huda, Andrew Hardie, Joseph Schoepf, Philip Costello, Thomas Flohr, and Martin Sedlmair "Iterative reconstruction in image space (IRIS) and lesion detection in abdominal CT", Proc. SPIE 7622, Medical Imaging 2010: Physics of Medical Imaging, 76222K (22 March 2010); https://doi.org/10.1117/12.843787

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