Intravascular near-infrared fluorescence catheter with ultrasound guidance and blood attenuation correction

Abstract

Abstract. Intravascular near-infrared fluorescence (NIRF) imaging offers a new approach for characterizing atherosclerotic plaque, but random catheter positioning within the vessel lumen results in variable light attenuation and can yield inaccurate measurements. We hypothesized that NIRF measurements could be corrected for variable light attenuation through blood by tracking the location of the NIRF catheter with intravascular ultrasound (IVUS). In this study, a combined NIRF-IVUS catheter was designed to acquire coregistered NIRF and IVUS data, an automated image processing algorithm was developed to measure catheter-to-vessel wall distances, and depth-dependent attenuation of the fluorescent signal was corrected by an analytical light propagation model. Performance of the catheter sensing distance correction method was evaluated in coronary artery phantoms and ex vivo arteries. The correction method produced NIRF estimates of fluorophore concentrations, in coronary artery phantoms, with an average root mean square error of 17.5%. In addition, the correction method resulted in a statistically significant improvement in correlation between spatially resolved NIRF measurements and known fluorophore spatial distributions in ex vivo arteries (from r ¼ 0.24 to 0.69, p < 0.01, n ¼ 6). This work demonstrates that catheter-to-vessel wall distances, measured from IVUS images, can be employed to compensate for inaccuracies caused by variable intravascular NIRF sensing distances.

Development of a Photoacoustic, Ultrasound and Fluorescence Imaging Catheter for the Study of Atherosclerotic Plaque

“…Previous multimodal catheters reported frame rates of less than 10 images/second in fluorescence imaging with a larger catheter than us [22]- [24]. Our scanning system and catheter allowed colocalized acquisitions of fluorescence and ultrasound at a frame rate of 30 images/second.…”

“…Images were aligned with IVUS acquired with a different catheter, which complicated experimental acquisitions. Catheters combining IVUS and fluorescence imaging were also designed, but they remain relatively large in size [22]- [24].…”

Fluorescence Lifetime Imaging and Intravascular Ultrasound: Co-Registration Study Using Ex Vivo Human Coronaries

“…For that reason there is a need to correct the acquired NIRS data before any assessment can be made [35]. This issue is also present in the case of the NIRF imaging, where attempts to correct for the distance dependence have been reported by various researchers [22], [36]. …”

“…Multimodal intravascular imaging catheters, which perform the co-registration at hardware level, have been developed for other applications, i.e., NIRF/IVUS [36] Such hardware adaptation is essential as the combined cardiac and breathing motion will make the guide-wire based co-registration impractical. This will only require a minor modification to the proposed co-registration methodology: the detection of an image feature will be replaced with a predefined angular delay between the two modalities, and the co-registration process will proceed as described in this paper.…”

Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy

“…Conventional grayscale IVUS is, however, limited with regards to the analysis of plaque composition [9], whereas emerging molecular imaging technologies, such as fluorescence imaging, have been developed to overcome these limitations. Multimodality imaging systems, such as the dual-modality IVUS/near-infrared fluorescence (NIRF) imaging catheter previously engineered by our group and others [10,11,12,13], were designed for integrated microstructural and molecular plaque imaging, thus enabling a more detailed plaque characterization. The use of molecular probes in conjunction with fluorescence imaging has been shown to provide complementary information with regards to plaque activity and inflammation [14,15,16,17,18,19].…”