A catheter-based intravascular radiation detector of vulnerable plaques

Detection of vulnerable plaques before rupture is important in preventing acute coronary events such as myocardial infarction. Although therapeutic strategies such as percutaneous transluminal coronary angioplasty appear to prevent coronary occlusion and consequently may lead to improved prognosis in these patients, a method of detecting vulnerable plaques has not been established. A nuclear method that uses an intravascular radiation detector (IVRD) with the plaque-avid tracer (18)F-FDG is one of the most promising methods. The catheter-based IVRD consists of a catheter probe (a scintillator and flexible optic fibers), photomultipliers, a controller, and an automatic pullback unit and personal computer. A phantom study demonstrated that this detector was highly sensitive to (18)F and enabled the detection of (18)F point sources. However, details of the detection system in vivo remain unclear.

To evaluate vulnerable plaques in vivo, we investigated a canine femoral artery and coronary artery using this detector system. Our goal was to estimate the ability of this device to navigate through these arteries and to detect (18)F point sources fixed on their adventitia.

In the study using a canine femoral artery, the IVRD could detect the point sources with good repeatability. In the study using an open-chest canine model, the catheter probe could easily be advanced into the left descending coronary artery, and the IVRD could detect target sources attached externally to the coronary artery (7- to 15-mm intervals) with good resolution.

This newly developed catheter-based IVRD was able to detect, with good resolution, the slight radioactivity from (18)F point sources attached to the femoral artery and the coronary adventitia. These results show that catheter-based detection of coronary vulnerable plaques may be feasible.