Lasers and ultrasound combine for safe, detailed imaging modality

Researchers at the California Institute of Technology have developed a new photoacoustic imaging technique that uses lasers to created detailed ultrasonographic images in live animals, according to findings published in Nature Biomedical Engineering.

The method, called single impulse panoramic photoacoustic computed tomography (SIP-PACT), can produce complete internal scans with enough spatiotemporal resolution to visualize active organs, circulating cancer cells, and brain function.

While MRI and PET technologies can produce detailed images of the body, this new photoacoustic tomography modality uses harmless laser pulses and ultrasound waves. This allows for detailed long scans that offers the ability to study real-time biologic processes for extended periods.

“Photoacoustic imaging is clearly the safest and most economical approach for longer term real-time imaging of live small animals,” explained Behrouz Shabestari, PhD, Director of the NIBIB Program in Optical Imaging and Spectroscopy at Caltech. “The group continues to develop innovative technologies to improve light-based imaging to enhance the system for eventual use in humans.”

The laser light pulses can penetrate up to several inches to reach the target tissue. The slight increase in heat from the laser pulses result in the emission of ultrasound waves. The sound waves are then captured and turned into images. The ultrasound waves travel easily through the surrounding tissue without the scattering that would normally blur the signal, so the images are extremely sharp.

“[SIP-PACT] allows us to capture structural, functional, cellular, and molecular small-animal whole-body images with unprecedented speed and quality,” said Lihong Wang, PhD, Departments of Medical and Electrical Engineering at Caltech, and lead author of the study. “Essentially, harmless laser pulses strike tissues—similar to tapping a drum to create vibrations that we then detect as ultrasound wave images.”

Dr. Wang stated SIP-PACT can monitor live animals during long periods of time, which allows for monitoring of the effects of experimental drugs without the possibility of radiation overdose associated with CT scans.

The team has used SIP-PACT to track a wide range of biologic processes, such as whole body and brain cross section scans in real time, and tracking of circulating tumor cells in the blood vessels of the mouse brain.

The group is enthusiastic about the capabilities of this system, and they are planning to eventually moving to more clinically relevant applications.

The work was supported by the National Institute of Biomedical Imaging and Bioengineering, with additional funding from the National Cancer Institute and the National Institute of Neurological Disorders and Stroke.

To read more about this study, click here.