Atsushi Urikura1, Takanori Hara2, Katsuhiro Ichikawa3, Eiji Nishimaru4, Takashi Hoshino5, Tsukasa Yoshida6, Yoshihiro Nakaya7. 1. Department of Diagnostic Radiology, Shizuoka Cancer Centre, 1007 Shimonagakubo, Nagaizumi, Sunto, Shizuoka 411-8777, Japan. Electronic address: at.urikura@scchr.jp. 2. Department of Medical Technology, Nakatsugawa Municipal General Hospital, 1522-1 Komanba, Nakatsugawa, Gifu 508-0011, Japan. Electronic address: hara_tnk2@ybb.ne.jp. 3. Division of Health Sciences, Kanazawa University Graduate of Medical Sciences, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan. Electronic address: ichikawa@mhs.mp.kanazawa-u.ac.jp. 4. Department of Radiology, Hiroshima University Hospital, 1-2-3, Kasumi, Minami-ku, Hiroshima 734-8551, Japan. Electronic address: eiji2403@tk9.so-net.ne.jp. 5. Department of Radiology, Ishinkai Yao General Hospital, 1-41 Numa, Yao, Osaka 581-0036, Japan. Electronic address: hoshi0311@hera.eonet.ne.jp. 6. Department of Diagnostic Radiology, Shizuoka Cancer Centre, 1007 Shimonagakubo, Nagaizumi, Sunto, Shizuoka 411-8777, Japan. Electronic address: ts.yoshida@scchr.jp. 7. Department of Diagnostic Radiology, Shizuoka Cancer Centre, 1007 Shimonagakubo, Nagaizumi, Sunto, Shizuoka 411-8777, Japan. Electronic address: y.nakaya@scchr.jp.
Abstract
OBJECTIVE: This study aims to assess low-contrast image quality using a low-contrast object specific contrast-to-noise ratio (CNRLO) analysis for iterative reconstruction (IR) computed tomography (CT) images. METHODS: A phantom composed of low-contrast rods placed in a uniform material was used in this study. Images were reconstructed using filtered back projection (FBP) and IR (Adaptive Iterative Dose Reduction 3D). Scans were performed at six dose levels: 1.0, 1.8, 3.1, 4.6, 7.1 and 13.3mGy. Objective image quality was assessed by comparing CNRLO with CNR using a human observer test. RESULTS: Compared with FBP, IR yielded increased CNR at the same dose levels. The results of CNRLO and observer tests showed similarities or only marginal differences between FBP and IR at the same dose levels. The coefficient of determination for CNRLO was significantly better (R(2)=0.86) than that of CNR (R(2)=0.47). CONCLUSION: For IR, CNRLO could potentially serve as an objective index reflective of a human observer assessment. The results of CNRLO test indicated that the IR algorithm was not superior to FBP in terms of low-contrast detectability at the same radiation doses.
OBJECTIVE: This study aims to assess low-contrast image quality using a low-contrast object specific contrast-to-noise ratio (CNRLO) analysis for iterative reconstruction (IR) computed tomography (CT) images. METHODS: A phantom composed of low-contrast rods placed in a uniform material was used in this study. Images were reconstructed using filtered back projection (FBP) and IR (Adaptive Iterative Dose Reduction 3D). Scans were performed at six dose levels: 1.0, 1.8, 3.1, 4.6, 7.1 and 13.3mGy. Objective image quality was assessed by comparing CNRLO with CNR using a human observer test. RESULTS: Compared with FBP, IR yielded increased CNR at the same dose levels. The results of CNRLO and observer tests showed similarities or only marginal differences between FBP and IR at the same dose levels. The coefficient of determination for CNRLO was significantly better (R(2)=0.86) than that of CNR (R(2)=0.47). CONCLUSION: For IR, CNRLO could potentially serve as an objective index reflective of a human observer assessment. The results of CNRLO test indicated that the IR algorithm was not superior to FBP in terms of low-contrast detectability at the same radiation doses.