MIT Builds Laser-based System For Non-contact

Recently, researchers at MIT's Lincoln Laboratory and collaborators at Massachusetts General Hospital's (MGH) Center for Ultrasound Research and Translation (CURT) have developed a new type of medical imaging device: non-contact laser ultrasound (NCLUS).
This laser-based ultrasound system is said to provide images of internal body features such as organs, fat, muscles, tendons and blood vessels. The system can also measure bone strength and potentially track different stages of disease.

"Our patented skin-safe laser system concept is designed to transform medical ultrasound by overcoming the limitations of traditional contact probes," explains principal investigator Robert Haupt, a senior staff member in Lincoln Laboratory's Active Optical Systems Group.
Robert Haupt and Senior Staff Member Charles Wynn are co-inventors of the technology, and Matthew Stowe, deputy group leader, is responsible for technical leadership and oversight of the NCLUS program. rajan Gurjar is the system integrator leader, and Jamie Shaw, Bert Green, Brian Boitnott (now at Stanford University), and Jake Jacobsen collaborated on optical and mechanical engineering and system construction.
While state-of-the-art medical ultrasound systems can distinguish tissue features within a few millimeters, this technology has some limitations. Non-contact laser ultrasound (NCLUS), on the other hand, may reduce the need for sonographers and decrease operator variability by fully automating the ultrasound image acquisition process. Laser positioning can be accurately reproduced, thus eliminating the variability of repeated measurements. Because the measurement is non-contact, there is no localized tissue compaction or image feature distortion associated with it. In addition, similar to MRI and CT, non-contact laser ultrasound (NCLUS) utilizes skin markers to provide a fixed frame of reference function to reproduce and compare repeated scans over time. To support this tracking function, the lab team developed software to process ultrasound images and detect any changes between images.
Non-contact laser ultrasound (NCLUS) requires neither manual pressurization nor coupling gel (which is required for contact probes), so it is also well suited for patients who have painful or sensitive body parts, are in a fragile state, or are at risk of infection. This technology allows imaging of burn or trauma patients, patients with direct openings to deep tissue during surgery, premature infants requiring intensive care, patients with neck and spinal injuries, and patients with remote infectious diseases.
Using a pulsed laser, light energy is transmitted through the air to the surface of the skin, where the light is rapidly absorbed once it enters the skin. The light pulse causes instantaneous localized heating and rapidly deforms the skin through a thermoelastic process, which in turn generates ultrasound waves that act as an ultrasound source-.
The light pulse generates sufficient ultrasound power at a frequency comparable to actual medical ultrasound without causing any pain to the skin. The research team patented the choice of optical carrier wavelengths, and the photoacoustic process is designed to produce a consistent source of ultrasound, independent of skin color or tissue roughness.
Ultrasound echoes returning from within the tissue appear as localized vibrations on the skin surface, which are measured by a highly sensitive, dedicated laser Doppler vibrometer.