Tiny Medical Sensors Boost Procedure Success in a Big Way

Minimally invasive medical procedures have many advantages over open surgery. Medical sensors provide surgeons with necessary feedback, improving outcomes and reducing the risk to patients.

Minimally invasive medical procedures have many advantages over open surgery, such as less damage to the body, less pain, fewer complications, less time in the hospital, and quicker overall recovery. Thanks to advances in technology, minimally invasive procedures have replaced many types of more invasive procedures. One of these advances is the use of medical sensors that provide feedback to the surgeon for better control, improving outcomes and reducing risk.

“We have a couple of sensor types that we provide for these minimally invasive procedures. However, how they exactly look very much depends on the type of operation or the type of procedure that is done,” said Marc Schillgalies, senior director, engineering for TE Sensors Group, TE Connectivity. The two main sensor types for these procedures are pressure sensors and temperature sensors. These incredibly small sensors measure 1 French (1FR), equal to 0.33 millimeters, according to the French scale (also known as the French gauge or Charrière system, used to measure the outer diameter of catheters).

TE Connectivity’s IntraSense Series of 1-French disposable catheter tip pressure sensors with attached wires for signal transmission is designed for use in minimally invasive devices.

Pressure and temperature sensors

Pressure sensors are fed through a blood vessel, or in some cases a series of blood vessels, on the tip of a catheter, to measure pressure in a variety of situations. They measure intracranial pressure in someone who has brain swelling resulting from a head trauma. They are used for monitoring blood pressure at the site of a procedure to determine if a blood vessel has been punctured, so the leakage can be addressed. A form of ablation (a procedure for removing tissue) uses a small, inflated balloon inserted into the blood vessel and requires pressure sensors to determine when this little balloon is inflated enough.

Temperature sensors provide important information during procedures, like ablation, that require heat. The heat is created in different ways: with laser light, with a kind of hot plate, or with an RF-induced microwave process. “Usually, you want to use heat to burn off the top surface. So, on the one hand, you want enough heat for the procedure to be successful and, on the other hand, you don’t want to create so much heat that you damage the tissue underneath, which needs to be able to regenerate. And for that, you need feedback. You cannot see, so the only thing that you can do is measure the temperature on that surface,” said Schillgalies. 

Currently in the works: PMUT and force sensors

Due to the small size of the blood vessels, there isn’t currently enough room to have a camera with the sensor. Outside imaging, such as an X-ray or computed tomography (CT) scan is often used in conjunction with these procedures. Nevertheless, the feedback from the sensors is vital.

“We are working on a sensor technology that helps with navigation, that uses ultrasound to ‘see’ the distance to the next blood vessel or to indicate if there’s a fork coming up,” said Schillgalies. He explained that these sensors, called PMUTs (piezoelectric micromachined ultrasonic transducers), are like the parking sensors in a vehicle. They signal if the person doing the procedure is coming close to a problem area or to the wall of the blood vessel.

Also currently in development are force sensors. “Some surgery tools are like little tweezers that take a tissue sample, for example. You want to make sure that you can control the force with which you clamp down. Sometimes you need to close a vessel for some time to limit the blood flow, but you don’t want to damage it. It’s easy to put too much mechanical force on it, so you need some sort of feedback that tells you, okay, this is now too much, and you can adjust,” Schillgalies said. As with the other sensors, it must be small enough to be as minimally invasive as possible and it needs to be sensitive to very small changes.

Other aspects in development are sensors that can stay in the body for an extended time, up to 28 days. Every time the sensor is removed, it becomes a potential source of infection or other problems, so being able to leave it in for longer periods is beneficial.

Designing sensors for minimally invasive procedures

In addition to being small enough, the sensors need to be very fast so that corrections can happen quickly. They also must be designed for the environment inside the body. Some need to be able to survive internally for an extended period. This necessitates the exclusion of any materials that can cause a negative reaction. Designers and engineers must rely on tests of biocompatibility or use materials that have been certified for this purpose.

Another important consideration is sterilization. Sensors that are reusable, must be able to withstand cleaning processes. “Often, it’s basically a combination of heat and high pressure that elevates the temperature high enough to kill any virus or bacteria on the material. First, you need to have packaging that doesn’t let any water in, that’s maybe fully potted, for example. And secondly, if you go way beyond 100 °C, this can cause the organic materials, like the adhesives, to have problems, so they need to be designed for this high temperature,” said Schillgalies. “Often, radiation is used for sterilization, but the downside is that it usually fries all the electronics. We have that problem in the blood pressure application. We are designing a product that is reusable for five or ten procedures where usually you would use disposables. In this case, we actually prepare the product with shielding layers to protect the electronics. There are also special electronic components that our partners produce that have the ability to withstand radiation, a bit similar to what goes into satellites.”

Schillgalies acknowledged that developing medical sensors involves pushing the boundaries where there are no solutions yet. “It’s not like we receive a request that says, I want exactly this. It’s really a partnership that we need to have with our customers to understand together how to solve the medical problem. It’s not how to solve a technical issue on how to sense things, it’s really how to solve the medical problem and what best solution forward is there. And that that’s quite exciting.”

Visit the Preferred Supplier page for TE Connectivity to learn more about the company and its products.

Like this article? Check out our other Miniaturization and Sensors articles, our Medical Market Page, and our 2024 Article Archives. 

Subscribe to our weekly e-newsletters, follow us on LinkedIn, Twitter, and Facebook, and check out our eBook archives for more applicable, expert-informed connectivity content.

• 

  CCA: A High-Tech Solution for Advanced Air Combat Operations

• 

  Energy in Motion: E-Mobility and the Future of Intelligent Power

• 

  MIL-STD-1553: The Global Standard for Military and Aerospace Data Buses

• 

  Quality Connectors for Consumer Product Design