Lighting the way to safer heart procedures

April 17, 2020

In the first study of its kind, Johns Hopkins researchers provide evidence that an alternative imaging technique could someday replace current methods that require potentially harmful radiation.

The findings, published in the April issue of IEEE Transactions in Medical Imaging, detail success in a heart procedure but can potentially be applied to any procedure that uses a catheter, such as in vitro fertilization, or surgeries using the da Vinci robot, where clinicians need a clearer view of large vessels.

"This is the first time anyone has shown that photoacoustic imaging can be performed in a live animal heart with anatomy and size similar to that of humans. The results are highly promising for future iterations of this technology," says Muyinatu Bell, assistant professor of electrical and computer engineering at The Johns Hopkins University, director of the Photoacoustic & Ultrasonic Systems Engineering (PULSE) Lab, and the study's senior author.

Bell's team of PULSE Lab members and cardiologist collaborators tested the technology during a cardiac intervention, a procedure in which a long, thin tube called a catheter is inserted into a vein or artery, then threaded up to the heart to diagnose and treat various heart diseases such as abnormal heartbeats. Doctors currently most commonly use a technique called fluoroscopy, a sort of x-ray movie, that can only show the shadow of where the catheter tip is and doesn't provide detailed information about depth. Additionally, Bell adds, this current visualization technology requires ionizing radiation, which can be harmful to both the patient and the doctor.

Photoacoustic imaging, simply explained, is the use of light and sound to produce images. When energy from a pulsed laser lights up an area in the body, that light is absorbed by photoabsorbers within the tissue, such as the protein that carries oxygen in blood (hemoglobin), which results in a small temperature rise. This increase in temperature creates rapid heat expansion, which generates a sound wave. The sound wave can then be received by an ultrasound probe and reconstructed into an image.

Past studies of photoacoustic imaging mostly looked at its use outside of the body, such as for dermatology procedures, and few have tried using such imaging with a laser light placed internally. Bell's team wanted to explore how photoacoustic imaging could be used to reduce radiation exposure by testing a new robotic system to automatically track the photoacoustic signal.

For this study, Bell's team first placed an optical fiber inside a catheter's hollow core, with one end of the fiber connected to a laser to transmit light; this way, the optical fiber's visualization coincided with the visualization of the catheter tip.

Bell's team then performed cardiac catherization on two pigs under anesthesia and used fluoroscopy to initially map the catheter's path on its way to the heart.

Bell's team also successfully used robotic technology to hold the ultrasound probe and maintain constant visualization the photoacoustic signal, receiving image feedback every few millimeters.

Finally, the team looked at the pig's cardiac tissue after the procedures and found no laser-related damage. While the team needs to perform more experiments to determine whether the robotic photoacoustic imaging system can be miniaturized and used to navigate more complicated pathways, as well as perform clinical trials to definitively prove safety, they say these findings are a promising step forward.

"We envision that ultimately, this technology will be a complete system that serves the four-fold purpose of guiding cardiologists towards the heart, determining their precise locations within the body, confirming contact of catheter tips with heart tissue and concluding whether damaged hearts have been repaired during cardiac radiofrequency ablation procedures," says Bell.
-end-
Other authors on this study include Michelle Graham, Fabrizio Assis, Derek Allman, Alycen Wiacek, Eduardo Gonzalez, Mardava Gubbi, Jinxin Dong, Huayu Hou, Sarah Beck and Jonathan Chrispin, all of Johns Hopkins.

Johns Hopkins University

Related Medical Imaging Articles from Brightsurf:

Improved medical imaging improves cancer staging
Prof. TIAN Chao's group improved the imaging quality and 3D construction of the photoacoustic imaging, and applied them to in vivo sentinel lymph node imaging.

AI techniques in medical imaging may lead to incorrect diagnoses
Machine learning and AI are highly unstable in medical image reconstruction, and may lead to false positives and false negatives, a new study suggests.

Tiny devices promise new horizon for security screening and medical imaging
Miniature devices that could be developed into safe, high-resolution imaging technology, with uses such as helping doctors identify potentially deadly cancers and treat them early, have been created in research involving the University of Strathclyde.

Advanced medical imaging combined with genomic analysis could help treat cancer patients
Melding the genetic and cellular analysis of tumors with how they appear in medical images could give physicians new insights into how to best treat patients, especially those with brain cancer, according to a new study led by TGen.

Low doses of radiation used in medical imaging lead to mutations in cell cultures
Common medical imaging procedures use low doses of radiation that are believed to be safe.

Use of medical imaging
This observational study looked at patterns of use for computed tomography (CT), magnetic resonance imaging (MRI), ultrasound and nuclear medicine imaging in the United States and in Ontario, Canada, from 2000 to 2016.

Medical imaging rates continue to rise despite push to reduce their use
The rates of use of CT, MRI and other scans have continued to increase in both the US and Ontario, Canada, according to a new study of more than 135 million imaging exams conducted by researchers at UC Davis, UC San Francisco and Kaiser Permanente.

Two-in-one contrast agent for medical imaging
Magnetic resonance imaging (MRI) visualizes internal body structures, often with the help of contrast agents to enhance sensitivity.

Medical imaging rates during pregnancy
Researchers looked at rates of medical imaging (CT, MRI, conventional x-rays, angiography, fluoroscopy and nuclear medicine) during pregnancy in this observational study that included nearly 3.5 million pregnant women in the United States and Canada from 1996 to 2016.

Scientists discover new method for developing tracers used for medical imaging
University of North Carolina researchers discovered a method for creating radioactive tracers to better track pharmaceuticals in the body as well as image diseases, such as cancer, and other medical conditions.

Read More: Medical Imaging News and Medical Imaging Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.