Photoacoustic Detection and Optical Spectroscopy of HIFU Lesions
During his master’s studies, Mosa Alhamami (now working on a PhD at the University of Toronto) collaborated with Department of Physics professors Michael Kolios and Jahan Tavakkoli on spectroscopic investigations of in vitro tissue that had been treated with high-intensity focused ultrasound (HIFU). Their findings recently appeared in Medical Physics (Mosa was the paper’s lead author).
HIFU uses precision-focused sound waves to heat tumours in order to kill cancer cells. This non-invasive, non-surgical approach is growing in popularity for treating a variety of cancerous tumours, including in the prostate, breast and kidney. It is also deployed in neurosurgery and cosmetic surgery. As Dr. Tavakkoli explains, HIFU’s clinical use “requires a robust and real-time imaging method for detecting HIFU-induced thermal lesions and to monitor treatment.” Currently, however, the standard imaging methods – MRI and ultrasound – are expensive and produce low contrast-resolution between normal and treated tissues.
In an effort to overcome these limitations, scientists have begun examining the potential of photoacoustic (PA) imaging, which provides higher resolution than optical imaging and higher tissue contrast than ultrasound imaging. Working in this field, Mosa designed studies, performed experiments and analyzed data relating to two main dimensions:
· The possibility of PA detection of HIFU-induced thermal lesions in chicken-breast tissues in vitro at 720 and 845 nm laser illuminations
· The optical properties of HIFU-induced thermal lesions compared with untreated tissues (via optical spectroscopy in the 500–900 nm wavelength range)
The results verified the researchers’ hypothesis that PA detection of HIFU-induced thermal lesions is feasible as a consequence of changes in the optical properties of HIFU-treated tissues.
According to Mosa, “Most important of all was our demonstration that the PA method is capable of detecting HIFU-induced tissue coagulation necrosis and its associated alterations in tissue’s molecular and structural compositions. Related to that, the spectroscopic component of the project furthered our understanding of the factors influencing PA signal generation from treated and untreated tissue. These are critical insights on the way to maximizing HIFU’s therapeutic potential.”
This study was funded through an Ontario Research Fund - Research Excellence grant entitled “Focused Ultrasound Devices for Noninvasive Surgery and Drug Delivery”.