Cardiovascular disease is currently the leading cause of mortality worldwide. Digital subtraction angiography (DSA) is widely used to enhance the visibility of small vessels and vasculature obscurred by overlying bone and lung fields by subtracting a mask and contrast image. However, motion between these mask and contrast images can introduce artifacts that can render a study non-diagnostic. This makes DSA particularly unsuccessful for cardiac imaging. A method called dual-energy, or energy subtraction angiography (ESA), was proposed in the past as an alternative for vascular imaging, however it was not pursued because experimental results suggested that image quality was deemed as poor and inferior to DSA. Image quality for angiography comes down to iodine signal and noise. In this paper we investigate the fundamental iodine signal and noise analysis of ESA and compare it to DSA. Method: We developed a polyenergetic and monoenergetic theoretical model for iodine signal and noise for both ESA and DSA. We validated our polyenergetic model by experiment where ESA and DSA images of a vascular phantom were acquired using an x-ray system with a flat panel CsI Xmaru1215CF-MPTM (Rayence Co., Ltd., Republic of Korea) detector. For ESA low and high applied tube voltages of 50 kV and 120 kV (2.5 mmCu), respectively, and for DSA the applied tube voltage was 80 kV. Iodine signal-to-noise ratio (SNR) per entrance exposure was calculated for each iodine concentration for both ESA and DSA. Results: Our measured iodine SNR agreed well with theoretical calculations. Iodine SNR for ESA was relatively higher than DSA for low iodine mass loadings, and as iodine mass loading increases iodine SNR decreases. Conclusions: We have developed a model for iodine SNR for both DSA and ESA. Our model was validated with experiment and showed excellent agreement. We have shown that there is potential for obtaining iodine-specific images using ESA that are similar to DSA.

Date Published: 18 March 2015
PDF: 14 pages
Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 941219 (18 March 2015); doi: 10.1117/12.2082724

Published in SPIE Proceedings Vol. 9412:
Medical Imaging 2015: Physics of Medical Imaging
Christoph Hoeschen; Despina Kontos, Editor(s)