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Early detection of high-risk coronary atherosclerosis remains an unmet clinical challenge. We have
previously demonstrated a near-infrared fluorescence catheter system for two-dimensional intravascular
detection of fluorescence molecular probes [1]. In this work we improve the system performance by
introducing a novel high resolution sensor. The main challenge of the intravascular sensor is to provide a
highly focused spot at an application relevant distance on one hand and a highly efficient collection of
emitted light on the other.
We suggest employing a double cladding optical fiber (DCF) in combination with focusing optics to
provide a sensor with both highly focused excitation light and highly efficient fluorescent light collection.
The excitation laser is coupled into the single mode core of DCF and guided through a focusing element
and a right angle prism. The resulting side-fired beam exhibits a small spot diameter (50 μm) throughout a
distance of up to 2 mm from the sensor. This is the distance of interest for intravascular coronary imaging
application, determined by an average human coronary artery diameter. At the blood vessel wall, an
activatable fluorescence molecular probe is excited in the diseased lesions. Next light of slightly shifted
wavelength emits only in the places of the inflammations, associated with dangerous plaques [2]. The
emitted light is collected by the cladding of the DCF, with a large collection angle (NA=0.4). The doublecladding
acts as multimodal fiber and guides the collected light to the photo detection elements. The
sensor automatically rotates and pulled-back, while each scanned point is mapped according to the
amount of detected fluorescent emission. The resulting map of fluorescence activity helps to associate the
atherosclerotic plaques with the inflammation process. The presented detection system is a valuable tool
in the intravascular plaque detection and can help to differentiate the atherosclerotic plaques based on
their biological activity, identify the ones that prone to rupture and therefore require more medical
attention.
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