New laser scanner to provide 3D view inside tumours

December 16th, 2007 - 11:34 am ICT by admin  

London, Dec 16 (ANI): Scientists have developed a new laser scanner that can give 3D view of the deformed blood vessels inside tumours.

This scanner could prove beneficial to doctors in determining the boundary between cancerous and healthy tissue during surgery.

A novel form of non-invasive imaging called photoacoustic tomography is used by the scanner. A laser light to “twang” cells is utilized so that they emit an ultrasound wave, which is then detected and used to form a 3D image.

The present day ultrasound scanners capture images by aiming high-frequency sound waves at the body. These waves are reflected whenever the density of tissue changes, for example at the boundary between muscle and bone. The echoes that result then used to create a picture.

However, these scanners can be useful in capturing images of high-contrast subjects like antenatal scans, but gives rise to only low-contrast images of the inside of a tumor, as the density of blood vessels is similar to that of the surrounding tissue.

The high-resolution photoacoustic tomography scanner offers a solution for this problem. It has been developed by Paul Beard and colleagues at University College London, UK.

Very short pulses of non-harmful near-infrared laser light are thrown at the tumor. When this light is absorbed by tissue, the cells get heated up and expand a little, creating an ultrasound wave that can be detected by a sensor.

The intensity of the ultrasound wave depends on how well the tissue absorbs the near-infrared radiation. This results in high-contrast images of blood vessels because haemoglobin is very absorbent at these wavelengths.

“It’s very scalable,” NewScientist.com quoted Beard, as saying.

He added: “Our scanner is best suited to providing high-resolutions images at a short range, but the technique could be used to image tumours a few centimetres into the breast.”

The researchers also created a new ultrasound sensor so as to convert the reflected ultrasound into a high-resolution 3D image.

It comprised of a thin layer of a polymer sandwiched between two reflective layers. The outer layers only reflect certain wavelengths of light and the laser light used to penetrate a patient’s tissue shines straight through all three layers.

The polymer layer then picked up the acoustic signal generated using the infrared.

“This work demonstrates progress,” said Hao Zhang, an expert on medical imaging at Washington University in St Louis, US.

He added: “In my opinion, it is important for more precise quantitative measurements.”

However, Zhang points out two potential problems. At the moment it takes a relatively long time to capture the image, while the laser scans each reflective surface. In addition, the sensor is flat making it difficult to scan images over curved parts of the body.

However, Jeremy Skepper, a physiologist at the University of Cambridge in the UK said that the ability to image blood vessels at this resolution is very striking.

“It’s less expensive and more portable than other solutions,” he says. “It’s a powerful additional tool to the ones we already have, he said.

Skepper also suggested that the device could prove to be highly portable in future owing to advances in laser diode technology. (ANI)

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