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Laser imaging tracks blood

17 Jun 2002

Blood flow in the brain could be monitored using laser speckle imaging, say US researchers.

Exclusive from Opto & Laser Europe magazine

Andrew Dunn and his colleagues at the NMR Centre of Massachusetts' General Hospital claim that the technique, which provides real-time images of blood flow during neurosurgery, has never before been used on the brain. "Previously this technique has been used to image blood flow in skin and the retina, but with varying degrees of success," said Dunn.

The procedure involves removing part of the skull, leaving the dura - the thin layer between the skull and the brain - intact. This area is then illuminated with a 760 nm, 30 mW diode laser. The scattered light is imaged onto a camera and is then converted into blood flow images.

"Other methods for measuring blood flow in the brain include magnetic resonance and positron-emission imaging, but these have a much lower spatial resolution [about 1 mm, compared with 10 to 25 µm for the speckle technique] and lower temporal resolution [minutes rather than real-time] than our method," commented Dunn. "However, these methods are non-invasive."

The technique could be used for measuring cerebral blood flow during brain surgery. "Since the technique works best with an open-skull preparation, it would be performed during surgery to assess blood flow in different areas of the brain," added Dunn.

According to Dunn, the advantage of using this technique lies in its simplicity: "It was relatively straightforward to implement, although any in vivo imaging technique is challenging."

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