| Cardiac arrest caused by the rupture of atherosclerotic plaques is one of the main causes of death in the western world. Intravascular near-infrared fluorescence (iNIRF) imaging can be used to detect plaques at high risk of rupture, utilizing a catheter that delivers laser light to excite fluorochromes specific to molecules produced by inflammation and other biological processes associated with plaque formation. One significant feature of iNIRF imaging is its capability to image through blood. However, because of the absorption and scattering of photons caused by red blood cells, fluorescence intensity detected through blood is dependent on the distance between the fluorescent source and the detector, thus preventing quantitative imaging. Moreover, the scattering of photons through blood causes the imaging resolution to degrade as a function of distance, in addition to the blur introduced by the imaging system's point spread function. Here we consider two hybrid approaches whereby structural information of the imaged vessel, acquired from co-registered intravascular ultrasound (IVUS), is employed to correct for variations in the distance between fiber-tip and vessel wall and to improve the imaging resolution.;In the first approach, we developed an attenuation correction algorithm that utilizes a light attenuation model derived experimentally and modeled through Monte Carlo simulations, in order to correct the fluorescence intensity for its dependence on source-detector distance. In the second approach, a distance-dependent image deconvolution/attenuation correction scheme incorporated the blurring introduced by photon propagation through blood into a generalized point spread function in order to compensate for the effect of scattering on the imaging resolution, while at the same time correcting the fluorescence intensity. Both approaches used distance readings obtained from intravascular ultrasound. The resulting algorithms improve the quantification of fluorescence data, enabling a more accurate assessment of the disease and facilitating the detection of high-risk plaques. |
