Tissue imaging

A novel probe that sports a ring of ultrasound transducers around the tip of a medical catheter can help provide physicians with clearer real-time images of soft tissue.

Duke University biomedical engineers designed and fabricated the ultrasound probe which works like an insect's compound eye, blending images from the 108 miniature transducers which work in cohorts to help produce detailed 3D images.

Catheter-based procedures involve snaking instruments through blood vessels to perform various tasks, such as clearing arteries or placing stents, usually with the guidance of X-ray images.

In a series of proof-of-principle experiments in a water tank using simulated vessels, the engineers used the new ultrasound probe to guide two specific procedures: the placement of a filter within a vessel and the placement of a synthetic ‘patch’ for aortic aneurysms. The scientists plan to begin tests of the new system in animals within the year.

'While we have shown that the new probe can work for two types of procedures, we believe that results will be more far-reaching,' said Stephen W. Smith, director of the Duke University Ultrasound Transducer Group. ‘There are many catheter-based interventional procedures where 3D ultrasound guidance could be used, including heart valve replacements and placement of coils in the brain to prevent stroke. Wherever a catheter can go, the probe can go.'

Currently, when manoeuvring a catheter through a vessel, physicians rely on X-ray images taken from outside the body that are then displayed on a monitor to manipulate their instruments. Often, a contrast agent is injected into the bloodstream to highlight the vessel.

'While the images obtained this way are good, some patients experience adverse reactions to the contrast agent,' said research engineer Edward Light, the designer of the new probe. 'Also, the images gained this way are fleeting. The 3D ultrasound guidance does not use x-ray radiation or contrast agents, and the images are real-time and continuous.'

Another benefit is portability, which is an important issue for patients who are too sick to be transported, since X-rays need to be taken in specially equipped rooms, Light said. The 3D ultrasound machine is on wheels and can be moved easily to a patient’s room.