Detecting inflammatory cells in blood vessels

Atherosclerotic plaque typically builds up without symptoms and the search is on to develop early detection devices that will enable physicians to offer treatment before the disease progresses to advanced stages.

Now, in a study involving laboratory rabbits, a device that stimulates, collects and measures light emissions from body tissues has been able to detect the presence of inflammatory cells that are associated with critical atherosclerotic plaques in humans - plaques that are vulnerable to rupture. The study is described in the August 2005 issue of the journal Atherosclerosis.

An experimental time-resolved laser-induced fluorescence spectroscopy (TR-LIFS) device developed by researchers at Cedars-Sinai Medical Center was used to detect the presence of inflammatory cells in the aortas of animals, with results compared to those from pathology studies.

Laser-induced fluorescence spectroscopy is based on the fact that when molecules in cells are stimulated by light, they respond by becoming excited and re-emitting light of varying colours. Laser light focused on tissues is re-emitted in colours that are determined by the properties of the molecules. When these emissions are collected and analysed (fluorescence spectroscopy), they provide information about the molecular and biochemical status of the tissue.

Time resolution adds a greater degree of specificity, measuring not only the wavelength of the emission but the time that molecules remain in the excited state before returning to the ground state. This information is valuable because some emissions overlap on the light spectrum but have different 'decay' characteristics.

The TR-LIFS system consists of a laser, a two-way fibre-optic probe through which the laser light is delivered to the tissue and the fluorescence is collected, a spectrometer, a digital oscilloscope, and a computer workstation that provides user interface, coordination of components and interpretation software.