title: Transluminal attenuation-gradient coronary CT angiography on a 320-MDCT volume scanner: Effect of scan timing, coronary artery stenosis, and cardiac output using a contrast medium flow phantom.
abstract: OBJECTIVE
  Transluminal-attenuation-gradient (TAG) may reflect patient characteristics and physiological parameters. Furthermore, TAG may be affected by factors such as the CT scanner speed, scanning method, scan timing after contrast-medium (CM) injection, and the injection methods. The purpose of our study was to investigate quantitative TAG at different scan timing points after CM injection for coronary CT angiography.
  
  
  METHODS
  Using a CM flow phantom and two types of connecting tube mimicking 0% and 70% coronary artery stenosis, we performed 320-detector volume scanning. The heart rate was set at 60bpm and cardiac-output (CO) at 2.0 and 4.0 l/min, respectively. The acquisition time repeated at 0.5-s intervals for 40 and 25s at a CO of 2.0- and 4.0 l/min. We measured the CT number on the same slice level, calculated the time-density-curve (TDC) and the TAG at each time point.
  
  
  RESULTS
  At COs of 2.0 and 4.0 l/min at 0% stenosis, TAG exhibited smaller variations (-3.02 to +0.55HU/cm at 2.0 l/min, -2.63 to +0.43HU/cm at 4.0 l/min) than at 70% stenosis at each time point along the TDC. Compared with a CO at 2.0 l/min with 70% stenosis, the TAG curve for a CO at 4.0 l/min gradually changed with time (-6.64 to +1.18HU/cm at 2.0 l/min vs. -3.46 to +2.75HU/cm at 4.0 l/min).
  
  
  CONCLUSIONS
  The TAG value was affected by scan timing after CM injection and by CO although the size of the connecting tube with and without stenosis was identical.
authors: Department of Medical Physics, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan. Electronic address: funama@kumamoto-u.ac.jp.
authors: Yoshinori
authors: Y
authors: Funama
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Daisuke
authors: D
authors: Utsunomiya
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Seitaro
authors: S
authors: Oda
authors: Department of Radiology, Kumamoto University Hospital, Kumamoto, Japan.
authors: Toshiaki
authors: T
authors: Shimonobo
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Takeshi
authors: T
authors: Nakaura
authors: Department of Civil and Environmental Engineering, Graduate School of Science and Technology, Kumamoto University, Japan.
authors: Toshifumi
authors: T
authors: Mukunoki
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Masafumi
authors: M
authors: Kidoh
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Hideaki
authors: H
authors: Yuki
authors: Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors: Yasuyuki
authors: Y
authors: Yamashita
mesh_terms: D002302:Cardiac Output; D000072226:Computed Tomography Angiography / Q000295:instrumentation*; D003287:Contrast Media; D017023:Coronary Angiography / Q000295:instrumentation*; D023921:Coronary Stenosis / Q000000981:diagnostic imaging*; D007091:Image Processing, Computer-Assisted; D061330:Multidetector Computed Tomography / Q000295:instrumentation*; D019047:Phantoms, Imaging; D013997:Time Factors
chemical_list: D003287:Contrast Media
keywords: 320-Detector volume scanner; Contrast medium flow phantom; Coronary computed tomography angiography; Scan timing; Transluminal attenuation gradient