Yasuhiro Imai MS, Presenter: Employee, General Electric Company

Ryosuke Fujimoto MS, Abstract Co-Author: Employee, General Electric Company

Darin R. Okerlund MS, Abstract Co-Author: Employee, General Electric Company

Jiang Hsieh PhD, Abstract Co-Author: Employee, General Electric Company

Hiroshi Yamaguchi, Abstract Co-Author: Nothing to Disclose

Toshiyuki Takahashi, Abstract Co-Author: Nothing to Disclose

Current ECG gated helical scanning requires smaller helical pitch like 0.2:1 than normal helical, then X-ray exposure dose becomes relatively high. The purpose of this study was to propose a novel ECG triggered high-pitch helical scanning (ETHH) method, and to evaluate its performance.

The fastest possible table travel speed (175mm/sec) has an ability to scan whole heart area within 1sec. That is one-beat in case of about under 70bpm. Under 70bpm heart rate (HR), mid-diastole cardiac phase is less motion from previous clinical studies. The idea of this ETHH minimized motion effect in order to set scan window to mid-diastole cardiac phase using the fastest table travel speed with ECG triggering. We developed X-ray exposure and table control sequence with monitoring ECG wave data, and it started helical scanning with optimum cardiac phase set by inputs of scan range, mid-diastole scan position and mid-diastole cardiac phase. We measured its scanning start as an ECG triggering accuracy, and evaluated image quality of ETHH using the cardiac pulsating phantom with changing HR. We applied clinical chest (lung) routine and coronary screening exams for its evaluations, and also, CT Dose Index (CTDI) was measured.

ECG triggered X-ray exposure and table control accuracy was within10msec for 20 times repeated measurements. The cardiac pulsating phantom was scanned by ETHH using 175mm/sec table travel speed.with 40, 50, 60 and 70bpm. Image qualities of 40, 50 and 60bpm cases were good without motion artifact, however 70bpm case brought little motion artifact. Motion-free lung and coronary images demonstrated in clinical applications, and CTDI of ETHH was same in lung scanning and was reduced more than 80% in coronary scanning compared with ECG gated helical method.

Motion-free CT scanning was realized by the experimental system using ETHH method with one-beat under 60bpm. ETHH has potential in motion-free lung, thoracic aorta and coronary screening with low dose, and to minimize amount of contrast material.

The proposed method provides motion-free chest CT imaging, and has a potential to apply to extremely low dose coronary CT screening including calcium scoring.

Imai, Y, Fujimoto, R, Okerlund, D, Hsieh, J, Yamaguchi, H, Takahashi, T, Potential of ECG-triggered High-Pitch Helical CT Scanning within One Heart Beat.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6019719.html