Abstract 13410: The Influence of Tube Voltage and Heart Rate on Agatston Calcium Score Measurement Using an in Vitro, a Novel ECG Gated Dual Energy Reconstruction CT Technique
Introduction: Dual energy CT is a novel CT technique with which virtual images were reconstructed at any tube voltage between dual tube voltages and with which calcium composition can be differentiated.
Hypothesis: To evaluate the influence of tube voltage and pulse rate on the accuracy of Agatston calcium scores (ACS) over a wide range of calcification states using an in vitro, dual energy, reconstruction CT technique.
Methods: Mock, calcified blood vessels with maximum CT values of 200, 300 and 400 HU were pulsed at 40-120 beats/min (BPM). Retrospective ECG gated 320 slice CT was performed with a tube voltage of 80 and 135kV. Using volume exposure control to equalise signal to noise ratios, tube current was set at 380mA (80KV) and 100mA (135kV). Images were reconstructed using half (65 BPM) during the most static phase. Using the dual energy reconstruction technique, virtual images were reconstructed at 5kV intervals at a tube voltage of 85-130kV. The ACS, tube voltages and pulse rate were then measured for each calcified vessel.
Results: The ACS for the 200 HU vessel at 40-70 BPM (relative to each static state) was accurate from 80-140kV, but decreased to <50%when the tube voltage was increased to 100kV (120BPM), 105kV (100 and 110BPM), 115kV (90BPM), and 125kV (80BPM). The ACS for the 300HU vessel at 40-70 BPM was only accurate from 80-110kV and decreased to 60-70% when the tube voltage was increased to 95kV (110 and 120BPM), 105kV (100BPM), 115kV (90 and 70BPM), 120kV (50BPM), 125kV (40BPM) and 130kV (60BPM).The ACS for the 400 HU vessel at 40-70 BPM was accurate from 80-125kV (40-100BPM) but decreased to 80% when the tube voltage was increased to 90kV (120BPM) and 105kV (110BPM).
Conclusions: When the tube voltage was low, i.e. 80-90KV, the ACS for 200-400HU vessels was stable at 40-120 BPM, but the ACS, especially with the 200HU vessel, decreased when the tube voltage and pulse rate increased, even though signal to noise ratios were equal.
Author Disclosures: N. Funabashi: None. H. Takaoka: None. J. Ohta: None. R. Irie: None. R. Morimoto: None. Y. Namihira: None. M. Aiba: None. K. Ozawa: None. Y. Masuda: None. Y. Kobayashi: None.
- © 2014 by American Heart Association, Inc.