Design, construction and validation of a multimodal intravascular diagnostic catheter combining IVUS and fluorescence lifetime spectroscopy detection channels

We report the development and validation of an intravascular rotary catheter that enables bi-modal interrogation of arterial pathologies based on fast-frame time-resolved fluorescence spectroscopy (TRFS) and intravascular ultrasound (IVUS). The catheter is based on a parallel design that allows for independent rotation of the ultrasonic and optical channels within an 8 Fr outer diameter catheter sheath and integrates a low volume flushing channel for blood removal in the optical pathways. In current configuration, the two channels consist of a) a standard 8 Fr IVUS catheter with single element transducer (15 MHz) and b) a side-viewing UV-grade silica/silica fiber optic (400 μm core). The catheter is terminated by a small (0.82 mm internal diameter) polyimide tube to keep the fiber stable within the sheath. To clear the field of view from blood, a saline solution can be flushed in a sheath channel, concentric with the fiber optic, through the tube and in a radial opening aligned with the fiber's optical beam. The flushing function was optimized with a computational fluid dynamics (CFD) model pursued in a parallel study. The ability of the catheter to operate in intraluminal setting in blood flow, the effect of probe-to-tissue distance on optical signal and ability to generate co-registered TRFS and IVUS data were demonstrated in blood vessel phantoms. Current results demonstrate the feasibility of the described catheter for parallel interrogation of vessel walls based on TRFS and IVUS and to generate robust TRFS data. These results facilitate further development of a bi-modal TRFS-IVUS technique for intravascular diagnosis of atherosclerotic cardiovascular diseases including vulnerable plaques.