3D Doppler Ultrasound Could Make Diagnostics Safer

Matt FronheiserDoctoral candidate Matt Fronheiser wants to lift a heavy weight from doctors’ shoulders and cast off the collar around their necks. He’s not campaigning for changes to Medicare or lobbying for reduced hospital shifts, however. He’s focused on the lead vests and collars doctors wear during fluoroscopy procedures to protect themselves from x-ray exposure.Fluoroscopy, which creates a sort of x-ray movie, helps doctors position diagnostic and therapeutic treatment devices inside their patients. This technique is used for many medical procedures, from guiding placement of pacemakers leads to taking biopsies of potentially cancerous tissue. To protect themselves from the x-ray radiation, doctors wear lead vests and a collar that protects their thyroid gland. X-ray exposure is monitored by a dosimeter.

"When a doctor exceeds the maximum allowable ‘dose’ of x-ray exposure, he can’t perform more procedures using fluoroscopy until a specified amount of time passes," said Fronheiser. "There’s a better way to do business that will eliminate this unnecessary radiation exposure for doctors and their patients, and allow them to track their instruments in real time."

Fronheiser is working to combine two existing technologies–— 3-dimensional ultrasound and a cell phone vibrator–— to give doctors another option. "The key for doctors is to be able to precisely monitor where the tip of the medical device is inside the patient," he said.

As part of a larger effort to extend the use of 3D ultrasound, Fronheiser, working with his adviser, biomedical engineering professor Stephen Smith, attaches an off-the-shelf vibrating buzzer used in cell phones to one end a medical device. Vibrations travel along the length of the instrument to the tip that is inserted into the patient. Using 3D ultrasound and color Doppler, Fronheiser tracks the movement of the device and is able to precisely locate the instrument tip.

Fronheiser and Smith recently published a paper in the journal Ultrasonic Imaging detailing their progress. The team has tested the feasibility of using the combination of vibration, 3D ultrasound and color Doppler imaging to track the placement of a pacemaker lead, a Brockenbrough needle for cardiac septal puncture, a cardiac guidewire and radiofrequency ablation needles used for cancer treatments.

Stiff instruments such as the Brockenbrough needle and the ablation needles worked best because the vibrations created a strong signal at the instrument tip. Floppy, thin wires used in the pacemaker lead and cardiac guidewire are much more challenging because the vibrations get muted, making it tougher to detect using color Doppler.

Altering the design of the interventional devices to make them easier to detect is out of the question. To require such changes in order to make the new imaging technique feasible would be expensive and unnecessarily restrictive for industry. So Fronheiser’s plans instead to boost the sensitivity of the 3D ultrasound machine so that it better detects the vibrations emanating from the various devices.

To do that, he has to understand how and where the ultrasound machine actually processes information, and then modify the computer programming and ultrasound system hardware.

"I need to understand how data is produced by the system so that I can improve certain functions or add new functions that don’t currently exist," he said. Programming skills he gained as an undergraduate are serving him well.

"While the rest of our research group works on building new devices, I am delving into the ultrasound machine itself, digesting the technical manuals and frequently talking with the manufacturer and other research groups here at Duke," Fronheiser said.

"Ultimately, we want to track a device from insertion to the end point and be able to predict what signals we should see all through the process," said Fronheiser.

Fronheiser works with a range of physical models to test the imaging technique. He starts by submerging the tip of a device in a tank of water and then imaging it through a sponge. The sponge serves as an artificial tissue–— representing the muscle and organs in an animal or human. Then he moves to animal organs and tissue, and ultimately to testing the technique in animals.

Fronheiser and Smith are confident they can create a system effective enough to be used in clinical settings. Their goal is to get the technique working well in animals within three years–— about the time Fronheiser will finish his doctorate. Even then, getting new technology into actual practice will be a challenge.

As a researcher, constantly reading about the cutting edge of new medical technologies and aware of the advances being made in laboratories, Fronheiser said he is amazed at slowly new techniques move into hospitals. "Doctors are using procedures today that were developed years and years ago," Fronheiser said. "We’ll have to convince them to try something new–— and that it is worth the learning curve to try it," said Fronheiser.

Fronheiser, who graduated with a bachelor in engineering from the Catholic University of America in Washington, D.C., in 2002, majoring in biomedical engineering, said he’s not sure whether he will pursue a career in industry or try to stay in academic research. Right now he says he is just focused on preparing for his preliminary examination.

One of the most educational parts of his doctoral program has been watching medical procedures at the Duke University Medical Center, Fronheiser said. "Our group has watched heart imaging at the echocardiology laboratory – it is so helpful to really see how doctors really work with the equipment," he said. He hopes to watch a full surgery soon.

Fronheiser, originally from Bally, PA, came to Duke’s biomedical engineering graduate program because of the faculty’s strength in medical imaging.