Approximately 70% of acute coronary artery disease is caused by unstable (vulnerable) plaques with an inflammation of the overlying cap and high lipid content. A rupturing of inflamed cap of plaque results in propagation of the thrombus into the lumen, blockage of the artery and acute ischemic syndrome or sudden death. Morphological imaging, such as angiography or intravascular ultrasound, can identify coronary plaque but cannot determine its inflammation status. Uptake of radiotracer 18F-FDG in vulnerable plaque is higher than in normal plaque, blood or tissue. This mechanism could be used to detect a vulnerable plaque. However, positron emission tomography (PET) cannot detect the FDG-labeled plaques because of respiratory and heart motions, small size and low activity of the plaque (notice that two thirds of acute ischemic syndromes result from a rupturing of relatively small and less stenotic plaques). Plaques can be detected using a miniature particle (positron) detector inserted into the artery. We propose a new detector concept for in-vivo intracoronary imaging of plaque. The detector consists of a storage phosphor tip bound to the end of an intravascular catheter. It can be inserted into an artery, absorb the 18F-FDG positrons from the plaque, withdrawn from the artery and readout. The length and diameter of the storage phosphor tip are variable, depending on the length and diameter of the artery into which the tip is inserted. Preliminary experiments and Monte Carlo simulations show that the sensitivity and spatial resolution of the proposed system are sufficient to detect vulnerable plaques of 1-2 mm size and 16-32 nCi activities in the arteries with 2-3 mm diameter for a 1 minute exposure time.
Specific aims of the proposal are: (1) development of an intravascular imaging system based on storage phosphor; (2) evaluation of the system performance using coronary artery and plaque phantoms; (3) investigation of the hypothesis that coronary plaques can be detected and quantified using the intravascular imaging system with storage phosphor tip in a swine animal model; (4) design of a clinically applicable prototype for intra-coronary imaging. The proposed technique will allow determination of whether or not the coronary artery plaque is vulnerable. If plaque is vulnerable, then acute ischemic syndrome can be anticipated and treatment becomes necessary. If plaque is not vulnerable, then the patient may not have a problem, but the status of the plaque could be verified periodically. Additionally, the proposed technique will allow studying the key characteristics of the vulnerable plaques, and gaining both basic knowledge and methodologies for in-vivo imaging-based investigations of the plaques that are largely unavailable at the present time. ? ? ?
|Shikhaliev, Polad M; Petrek, Peter; Matthews 2nd, Kenneth L et al. (2010) Intravascular imaging with a storage phosphor detector. Phys Med Biol 55:2841-61|