Intravascular fluorescence is a catheter-based

molecular imaging Molecular imaging is a field of medical imaging that focuses on imaging molecules of medical interest within living patients. This is in contrast to conventional methods for obtaining molecular information from preserved tissue samples, such as ...

technique that uses near-infrared

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

to detect artery wall autofluorescence (NIRAF) or fluorescence generated by molecular agents injected intravenously (NIRF) . No commercial systems based on intravascular fluorescence are currently on the market, however, significant steps forwards in intravascular fluorescence imaging technology have been made between 2010-2016. It is typically used to detect functional state of artery wall including some known high-risk features of atherosclerosis (e.g., inflammation). It is usually combined with structural imaging modalities such as

Intravascular ultrasound Intravascular ultrasound (IVUS) or intravascular echocardiography is a medical imaging methodology using a specially designed catheter with a miniaturized ultrasound probe attached to the distal end of the catheter. The proximal end of the cath ...

and/or

Intracoronary optical coherence tomography Intracoronary optical coherence tomography (OCT) (or, more generally, intravascular optical coherence tomography, IVOCT) is an endoscopic-based application of optical coherence tomography. Analogous to intravascular ultrasound, intracoronary OCT ...

, to provide functional information in a morphological context.

Methods

Intravascular fluorescence typically used

laser-induced fluorescence Laser-induced fluorescence (LIF) or laser-stimulated fluorescence (LSF) is a spectroscopic method in which an atom or molecule is excited to a higher energy level by the absorption of laser light followed by spontaneous emission of light. It was f ...

to stimulate fluorescence emission of particular vessel wall and plaque components or previously injected molecular agents (i.e.,

). Fluorescence detection can be obtained by integration over a short period of time of the emitted intensity, life-time (i.e.,

fluorescence-lifetime imaging microscopy Fluorescence-lifetime imaging microscopy or FLIM is an imaging technique based on the differences in the exponential decay rate of the photon emission of a fluorophore from a sample. It can be used as an imaging technique in confocal microscopy, t ...

or FLIM), or by analyzing the spectral shape of emitted fluorescence (

fluorescence spectroscopy Fluorescence spectroscopy (also known as fluorimetry or spectrofluorometry) is a type of electromagnetic spectroscopy that analyzes fluorescence from a sample. It involves using a beam of light, usually ultraviolet light, that excites the electron ...

Near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

light is often used to stimulate fluorescence emission in the case of intravascular applications. Imaging

catheters In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cath ...

contain an

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair. Optical fibers are used most often as a means to ...

to deliver and collect light to and from inner lumen of human body through semi-invasive interventions (e.g.,

percutaneous coronary intervention Percutaneous coronary intervention (PCI) is a non-surgical procedure used to treat narrowing of the coronary arteries of the heart found in coronary artery disease. The process involves combining coronary angioplasty with stenting, which is the ...

in case of coronary arteries).

Applications

Several research studies demonstrated the role of intravascular fluorescence for the diagnosis of vascular diseases. Plaque autofluorescence has been used in a first-in-man study in coronary arteries in combination with

(OCT). Similarly, intravascular

has been used in combination with OCT in a clinical study using an

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...

approved molecular target (i.e.,

indocyanine green Indocyanine green (ICG) is a cyanine dye used in medical diagnostics. It is used for determining cardiac output, hepatic function, liver and gastric blood flow, and for ophthalmic angiography.

) to detect high-risk features of carotid plaques at risk for

stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...

. Molecular agents has been also used to detect specific features, such as stent

fibrin Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerize. The polymerized fibrin, together with platele ...

accumulation to detect unhealed intravascular stent ''in vivo'' at increased risk of

thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...

and enzymatic activity related to artery inflammation.

References

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Methods

Applications

References

See also