In an effort to improve real-time surgical visualization and reduce potential patient discomfort and injury, Johns Hopkins researchers have verified the accuracy and applicability of a minimally invasive live medical imaging method in a new study.
Published last week in Biomedical Optics Express, the researchers’ findings demonstrate that photoacoustic imaging via flexible array transducers is not only viable in surgical applications, but has the potential to surpass prior real-time imaging techniques in terms of image quality and target estimation accuracy, says principal investigator Muyinatu A. Lediju Bell, John C. Malone Associate Professor of Electrical and Computer Engineering in the Whiting School of Engineering.
Real-time medical imaging allows surgeons to get a better picture of how their tools and instruments are interacting with a patient’s internal structures during complicated operations. Fluoroscopy, or real-time X-ray imaging, can provide live surgical guidance but may expose patients to excessive X-ray radiation, potentially causing negative health outcomes. A safer alternative is photoacoustic imaging, in which the minimal heat resulting from the discharge of a pulsed laser creates ultrasonic waves that are picked up by a specialized sensor called a “transducer” and reconstructed into an image that surgeons can use for real-time guidance.
Conventional transducers, attached to the tips of surgical instruments for visualization purposes, are typically rigid, making them ideal for use on flat surfaces—but the human body is rarely that accommodating. To attain useful image quality, the transducers must be pressed into uneven tissues, which can cause organ distortion, patient discomfort, and risk of further injury.
In contrast, flexible array transducers adapt to the surfaces they touch without compressing biological tissue. Through a series of imaging experiments on phantoms, or dummy organs, and an ex vivo bovine liver, Bell and her team have demonstrated the viability of flexible array transducers in a surgical setting—and additionally determined that when photoacoustic imaging is combined with a traditional ultrasound, the resulting images provide more detail than can be achieved in either technique on its own.
Although rigid transducers currently have superior image quality due to their predictability in terms of signal processing, Bell is confident in the future of flexible arrays.
“Flexible arrays have the potential for even greater imaging capability because they can bend and contort in multiple shapes and don’t require the same level of increased compression to achieve the same image quality on irregular surfaces,” she explains.
The researchers plan to use their findings to expand the range of possibilities for photoacoustic guidance; for example, a flexible array wrapped around a patient’s arm may enable the photoacoustic imaging of their veins for better IV placement, Bell says.
She and her team will soon investigate the design of customized flexible arrays for specific procedures, organs, and body parts.
“We ultimately want to create an imaging method that a patient can ‘wear’ for the duration of a surgical or interventional procedure,” says Bell.
This work was funded by Bell’s National Science Foundation CAREER and Smart and Connected Health Awards. Her research team also included former electrical and computer engineering PhD student Alycen Wiacek, current PhD students Jiaxin Zhang and Ziwei Feng, and Kai Ding, an associate professor of radiation oncology and molecular radiation sciences at the School of Medicine.