Light and sound could lead the way to improved medical imaging

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The detection and treatment of tumors, diseased blood vessels and other soft-tissue conditions could be significantly improved, due to an imaging system called photoacoustic tomography being developed that uses both light and sound. The prototype system has been developed by medical physics and bioengineering experts at the University College London (UCL), with funding from the Engineering and Physical Sciences Research Council (EPSRC). Shortly the prototype will be tested in clinical applications, with routine deployment in the healthcare sector envisaged within five years, according to EPSRC researchers.

“This new system offers the prospect of safe, non-invasive medical imaging of unprecedented quality,” said Paul Beard, PhD, who leads UCL’s Photoacoustic Imaging Group. “It also has the potential to be an extremely versatile, relatively inexpensive and even a portable imaging option.”

Beard said the system uses extremely short pulses of low-energy laser light to stimulate the emission of ultrasonic acoustic waves from the tissue area being examined, which are then converted into high-resolution 3D images of tissue structure.

This method can be used to reveal disease in types of tissue that are more difficult to image using techniques based on x-rays or conventional ultrasound, Beard said. “For example, the new system is better at imaging small blood vessels, which may not be picked up at all using ultrasound. This is important in the detection of tumors, which are characterized by an increased density of blood vessels growing into the tissue.”

The technique will help doctors diagnose, monitor and treat a wide range of soft-tissue conditions more effectively, he added. By appropriate selection of the wavelength of the laser pulses, the light can be controlled to penetrate up to depths of several centimeters. The technique therefore has important potential for the better imaging of conditions that go deep into human tissue, such as breast tumors, and for contributing to the diagnosis and treatment of vascular disease.

The prototype instrument, however, has been specifically designed to image very small blood vessels (with diameters measured in tens or hundreds of microns) that are relatively close to the surface. Beard said that information generated about the distribution and density of these microvessels can in turn provide valuable data about skin tumors, vascular lesions, burns, other soft tissue damage, and even how well an area of tissue has responded to plastic surgery following an operation.