J Greffier1, F Macri2, A Larbi2, A Fernandez2, F Pereira2, C Mekkaoui3, J-P Beregi2. 1. EA 2415, Department of Radiology, Nîmes University Hospital, boulevard Professeur-Robert-Debré, 30029 Nîmes cedex, France. Electronic address: joel.greffier@chu-nimes.fr. 2. EA 2415, Department of Radiology, Nîmes University Hospital, boulevard Professeur-Robert-Debré, 30029 Nîmes cedex, France. 3. EA 2415, Department of Radiology, Nîmes University Hospital, boulevard Professeur-Robert-Debré, 30029 Nîmes cedex, France; Martinos Centre for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, United States of America.
Abstract
OBJECTIVES: To evaluate the distortion of circular structures induced by the increased image noise related to dose reduction and to assess the effect of iterative reconstruction (IR). METHODS: MDCT acquisitions were performed with 120 kVp for 200/100/60/40/20mAs with 100%/50%/30%/20%/10% of dose. Raw data were reconstructed by filtered back projection (FBP) and with two IR strengths. Image quality indices referred to water and acrylic were measured on a quality image phantom. Areas, perimeters, circularity were measured on the circular inserts of 4.8, 7.9 and 11.1mm on a morphological phantom. RESULTS: Dose reduction resulted in increased image noise and in decreased signal to noise ratio and contrast to noise ratio. IR improved these indices for the same dose without affecting the signal (number CT) and spatial resolution (modulation transfer function). The values of area, perimeter and circularity were altered compared to the actual value and the inserts were visually deformed with the dose reduction. IR improved these three parameters. Image quality indices, areas, perimeters and circularity of inserts were similar between the acquisition at 100% of the dose in FBP, 50% in strength-3 and 30% in strength-5 with different curves of noise power spectrum. CONCLUSION: IR associated to 70% of dose reduction modifies the images smooth (NPS) but maintains adequate image quality indices without causing distortions of circular structures.
OBJECTIVES: To evaluate the distortion of circular structures induced by the increased image noise related to dose reduction and to assess the effect of iterative reconstruction (IR). METHODS: MDCT acquisitions were performed with 120 kVp for 200/100/60/40/20mAs with 100%/50%/30%/20%/10% of dose. Raw data were reconstructed by filtered back projection (FBP) and with two IR strengths. Image quality indices referred to water and acrylic were measured on a quality image phantom. Areas, perimeters, circularity were measured on the circular inserts of 4.8, 7.9 and 11.1mm on a morphological phantom. RESULTS: Dose reduction resulted in increased image noise and in decreased signal to noise ratio and contrast to noise ratio. IR improved these indices for the same dose without affecting the signal (number CT) and spatial resolution (modulation transfer function). The values of area, perimeter and circularity were altered compared to the actual value and the inserts were visually deformed with the dose reduction. IR improved these three parameters. Image quality indices, areas, perimeters and circularity of inserts were similar between the acquisition at 100% of the dose in FBP, 50% in strength-3 and 30% in strength-5 with different curves of noise power spectrum. CONCLUSION: IR associated to 70% of dose reduction modifies the images smooth (NPS) but maintains adequate image quality indices without causing distortions of circular structures.
Authors: Martin H Goodenberger; Nicolaus A Wagner-Bartak; Shiva Gupta; Xinming Liu; Ramon Q Yap; Jia Sun; Eric P Tamm; Corey T Jensen Journal: J Comput Assist Tomogr Date: 2018 Mar/Apr Impact factor: 1.826
Authors: Ji Eun Lee; Seo-Youn Choi; Jeong Ah Hwang; Sanghyeok Lim; Min Hee Lee; Boem Ha Yi; Jang Gyu Cha Journal: Medicine (Baltimore) Date: 2021-05-14 Impact factor: 1.889