Researchers in the Department of Biomedical Engineering are developing imaging technologies to help doctors diagnose and treat diseases more effectively.
Researchers in the Department of Biomedical Engineering are developing imaging technologies to help doctors diagnose and treat diseases more effectively.
Professor Stanislav Emelianov and his team have developed contrast agents that will enhance the capabilities of both ultrasound and photoacoustic imaging technologies to detect and characterize cancer and other diseases. Beyond detection, this innovative, disease-specific technology holds promise in its ability to treat cancer as well.
From left to right: Researcher Kim Homan, Professor Stanislav
Emelianov, and graduate student Katie Wilson.
Ultrasound imaging is broadly used in the medical field. From prenatal applications to sports medicine and imaging of soft tissues, ultrasound is a widely available and affordable technology. However, it does have limitations. Generally, ultrasound cannot provide a comprehensive picture of the disease being imaged. To address these limitations, researchers have developed various ultrasound-based complementary imaging approaches, including photoacoustic imaging.
“Ultrasound images can show us whether or not something unusual or abnormal is present,” says Katie Wilson, a doctoral researcher in Dr. Emelianov’s lab. “Photoacoustic images, however, go further and can tell us what a tissue is made up of at the molecular level.”
In essence, photoacoustic imaging can tell doctors if a mass is cancerous by examining characteristics beyond size and shape, such as blood content and levels of blood oxygenation, indicative of the metabolic activity of a tumor. Furthermore, when photoacoustic imaging is combined with targeted contrast agents, the molecular signature of the disease can potentially be imaged, offering even more information to facilitate an accurate diagnosis.
Despite the recent advantages of biomedical photoacoustic imaging, it is not ready for the clinical setting due to challenges with, among others, the need for development of clinically acceptable contrast agents.
Professor Emelianov and his researchers have discovered a breakthrough in contrast agents, the results of which have recently been published in Nature Communications. They have developed contrast agents that generate photoacoustic signals through optically triggered vaporization rather than through the traditional thermal expansion mechanism—this is the first time the vaporization mechanism has been used in biomedical photoacoustic imaging.
These contrast agents are called Photoacoustic nanoDroplets, or PAnDs. They are made up of a perfluorocarbon, protein, and gold nanoparticles—all of which, when combined, produce high-resolution, high-contrast complementary images of tissue.
“PAnDs are a breakthrough technology because they harness a vaporization mechanism for generating a photoacoustic signal that is significantly stronger than thermal expansion and other mechanisms previously exploited in biomedical applications. The strong signal from PAnDs allows us to probe even deeper in tissue than traditional photoacoustic imaging allows,” said Dr. Emelianov.
Studies in tissue-mimicking phantoms and animals suggest that by combining photoacoustic and ultrasound imaging with PAnD contrast agents, physicians may be able to produce comprehensive images that describe what is happening not only anatomically but also physiologically.
“The current project was focused on cancer imaging and characterization but the developed technology can be extended to diagnose and treat other pathologies and diseases,” commented Dr. Kim Homan, co-author of the article and a postdoctoral researcher in Dr. Emelianov’s lab.
One advantage of the use of these unique contrast agents in imaging is that they would allow physicians not only to detect diseases noninvasively but also to characterize diseases. Today, the procedures to detect cancer in tissue involve invasive biopsies. PAnD-augmented ultrasound-guided photoacoustic imaging could eliminate the need for invasive testing. Furthermore, the combination of PAnDs with simultaneous ultrasound and photoacoustic imaging could advance early detection and staging of cancers, including deeply seated breast and prostate tumors.
Another promising aspect is the potential for PAnDs to treat cancer cells. Cancer cells can be specifically eliminated through the use of laser and ultrasound energy combined with image-guided delivery and release of a therapeutic agent. In essence, patients could be diagnosed and treated within the same physician’s visit, which would be a great medical advance when it comes to the treatment of cancer and other diseases that may develop and progress rapidly.
“Once fully developed, PAnDs may enable inexpensive, practical, and reliable personalized health care clinical tools allowing for assessment of an individual patient’s disease and delivery of unique, patient-specific treatment,“ Dr. Emelianov said.
