title: Assessment of temporal resolution of multi-detector row computed tomography in helical acquisition mode using the impulse method.
abstract: The purpose of this study was to propose a method for assessing the temporal resolution (TR) of multi-detector row computed tomography (CT) (MDCT) in the helical acquisition mode using temporal impulse signals generated by a metal ball passing through the acquisition plane. An 11-mm diameter metal ball was shot along the central axis at approximately 5 m/s during a helical acquisition, and the temporal sensitivity profile (TSP) was measured from the streak image intensities in the reconstructed helical CT images. To assess the validity, we compared the measured and theoretical TSPs for the 4-channel modes of two MDCT systems. A 64-channel MDCT system was used to compare TSPs and image quality of a motion phantom for the pitch factors P of 0.6, 0.8, 1.0 and 1.2 with a rotation time R of 0.5 s, and for two R/P combinations of 0.5/1.2 and 0.33/0.8. Moreover, the temporal transfer functions (TFs) were calculated from the obtained TSPs. The measured and theoretical TSPs showed perfect agreement. The TSP narrowed with an increase in the pitch factor. The image sharpness of the 0.33/0.8 combination was inferior to that of the 0.5/1.2 combination, despite their almost identical full width at tenth maximum values. The temporal TFs quantitatively confirmed these differences. The TSP results demonstrated that the TR in the helical acquisition mode significantly depended on the pitch factor as well as the rotation time, and the pitch factor and reconstruction algorithm affected the TSP shape.
authors.affiliation: Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan. Electronic address: ichikawa@mhs.mp.kanazawa-u.ac.jp.
authors.forename: Katsuhiro
authors.initials: K
authors.lastname: Ichikawa
authors.affiliation: Department of Medical Technology, Nakatsugawa Municipal General Hospital, 1522-1 Komanba, Nakatsugawa, Gifu 508-0011, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Hara
authors.affiliation: Department of Diagnostic Radiology, Shizuoka Cancer Centre, 1007 Shimonagakubo, Nagaizumi, Sunto, Shizuoka 411-8777, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Urikura
authors.affiliation: Department of Diagnostic Radiology, Kanazawa University Hospital, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8641, Japan; Graduate School of Medical Science, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 920-0942, Japan.
authors.forename: Tadanori
authors.initials: T
authors.lastname: Takata
authors.affiliation: Department of Radiology, Nagoya City University Hospital, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya, Aichi 467-0001, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ohashi
mesh_terms: D006801:Humans; D009038:Motion; D061330:Multidetector Computed Tomography / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D013997:Time Factors
keywords: Computed tomography; Impulse signal; Temporal resolution; Temporal sensitivity profile