Medical imaging: obtaining an accurate view of blood vessels for surgery

Surgical intervention is often inevitable when blood vessels become narrowed, blocked, or damaged. Surgeons use stents and medical balloons to open and widen the arteries, suck out the obstructing clots and use a catheter to examine the vessels. Intraoperative cardiovascular imaging is an essential tool to guide the catheters and instruments during the minimally invasive procedures.

To date, cardiovascular imaging primarily involves the use of radiation: to highlight the blood vessels, patients are perfused with a contrast medium that is picked up by a radiation-based medical imaging technique. This allows surgeons to monitor the vascular structure and check if the stent is placed in the correct position. Depending on the length of the procedure, the patient and the surgical team are exposed to cumulative radiation doses.

These surgical interventions widen blood vessels that have narrowed due to build-up. A stent is inserted to keep the arteries open and ensure improved blood flow. Catheters are also used for aortic valve placement. There are also first attempts to use minimally invasive surgeries to repair various types of aneurysms: implants are inserted to cut off the flow of blood to the aneurysm sac, or to fill in material that closes off the sac and creates a localized, manageable blood clot.

Regardless of the application, it is key to monitor and ensure the precise positioning of the devices. Any error can negatively affect the patient's health. In the worst-case scenario, the catheter could injure the blood vessel or the heart, which requires immediate open surgery.

When surgical procedures require high precision, robotics often comes into play to assist. The University Medical Center Freiburg is one of the first clinics in Europe to use a novel robot that performs cardiac catheterizations. "This unit can operate the catheter over which the examination is done, or wires over which stents and balloons are pushed. The operation is not done directly at the cardiac catheter table, but from outside in the control room," explains Prof. Constantin von zur Mühlen, Chief Medical Director of the Department of Cardiology and Angiology I, in a MEDICA-tradefair.com interview.

Von zur Mühlen maintains the robot is more precise than an expert human surgeon, which benefits the patient. The robot also saves the surgeon from having to wear a heavy radiation protection apron and subsequently reduces the radiation exposure from repeated use of imaging. Both present possible long-term health risks for surgeons.

These days, radiation in imaging is becoming less prevalent thanks to innovative approaches. At the end of 2020, the Helmholtz Zentrum München in Germany and the University of California, Los Angeles introduced a new non-invasive medical imaging modality. It is designed to help visualize various structures including blood vessels in different colors and in real-time resolution.

In a MEDICA-tradefair.com interview, the head of the study Dr. Oliver Bruns explains: "Unlike other medical imaging technologies, our process is very simple. We highlight the tissue with infrared light and then image the resulting fluorescence. We often also inject a contrast agent intravenously to color specific structures we want to analyze."

Radiation-free imaging would be accessible to more patients, including small children as this modality would not add more stress to their tiny bodies. Bruns emphasizes that the technology – which is presently still being evaluated in a pilot study – offers more flexibility than previous techniques: "One promising field of application is intraoperative imaging, which improves surgical accuracy. "Point-of-care" applications at the bedside or in support of specialists are yet another conceivable option."

The use of robotics and AI combined with imaging has the potential to increase surgical precision, save valuable time and subsequently benefit the patient. However, "Robots in cardiology are very new [Editor's note: compared to urology robotic-assisted surgery]," says von zur Mühlen. This still leaves a lot of room for improvement because the technology "still requires personnel and resources, which is always the case with a new technology at the beginning. We have to see how these two factors can be optimized in the near future so that this robotic examination can be used in the routine on patients in a time-saving and resource-saving way," adds von zur Mühlen. Yet this also provides new opportunities.

The remote control of Freiburg's cardiac catheter robot not only reduces the burden on surgeons. In time, this might also facilitate remote patient and surgical monitoring and supervision by specialists in another hospital, for example. It is even conceivable to control the robot remotely, provided there is a fast connection.

Thanks to innovations like these, all signs point to progress when it comes to intraoperative cardiovascular imaging. Once radiation-free imaging modalities are added to the mix, it will drastically expand the applications of intraoperative imaging, since an intervention would no longer involve any physical health risks. Ultimately, the possibilities of these interventions will benefit more patients around the world.