Expanding Reality — Augmented Reality Guidance for Tumor Ablations
By Kathy Hardy
Radiology Today
Vol. 21 No. 8 P. 22

Tumor ablation involves inserting a thin, needlelike probe through the skin to a targeted location—mapped out with CT, ultrasound, or MRI images—to treat a mass that could measure as little as 1 inch in size. To make the situation more challenging, the mass may be round or oblong. Any enhancement of that reality, such as augmenting image guidance, could bring a clearer focus for interventional radiologists performing this method of cancer treatment. In the case of image-guided tumor ablation, 3D augmented reality (AR) can make the human anatomy, with its obstacle course of organs and vessels, more clearly visible.

AR involves the enhancement of real-world environments by computer-generated perceptual information. This is not to be confused with virtual reality, in which the user’s perception of reality is based on information that doesn’t physically exist.

“In tumor ablation, augmented reality can potentially improve the visualization and perception of the tumor and surrounding structures, helping to improve the treating physician’s confidence and, ultimately, make the procedure even faster, safer, and more effective,” says Gaurav Gadodia, MD, a radiology resident at the Cleveland Clinic.

Researchers with the Cleveland Clinic recently presented data from a research abstract that showed the feasibility of using AR guidance with electromagnetically tracked tools to deliver targeted liver cancer treatments more effectively. This is the first clinical use of this kind of AR guidance for this purpose. Those involved in the study believe holograms and 3D technology can improve visualization and guidance for everyone involved in the treatment of patients with liver or other abdominal soft tissue tumors.

“As interventional radiologists, we take it for granted that we look at 2D images, are able to convert them to 3D images in our heads, and perform the procedure on patients in three dimensions,” says Charles Martin III, MD, FSIR, an interventional radiologist at Cleveland Clinic and the senior author and lead investigator of the institutional review board–approved study. “It’s a difficult skill acquired over time that we hope to make more efficient and safer. While working in the lab, we thought it would be good to try to bring augmented reality into the ablation process, allowing for an improved view in multiple dimensions of important structures to avoid and better visualization of the tumor and the ablation zone.”

Gadodia, the study’s lead author, sees AR as providing a better cognitive understanding of the anatomy for the purposes of improving image guidance capabilities.

“Tumor ablation is an important procedure, and it is essential for the probe or probes to be in the ideal location within the tumor for adequate treatment,” Gadodia says. “While conventional image guidance like ultrasound and CT is safe, effective, and remains the gold standard of care, there is a risk of not fully appreciating the anatomy, including the tumor morphology and nearby organs, which can increase the risk of recurrence and complications.”

Study Premise
Martin says the idea for enhancing procedural image guidance came from a working relationship with other clinicians involved with a multidisciplinary clinic and tumor board. “One of the most important steps in ablation is in the preprocedural assessment,” he says. “Every patient and every procedure is unique, and we hope to leverage this technology to assist physicians in providing the best possible outcomes for their patients, regardless of modality.”

In the initial abstract from this pilot study, AR was used for procedural planning and guidance in the percutaneous thermal ablation of solid liver tumors in five patients. For safety reasons associated with the evaluation of novel technology, standard-of-care imaging, including ultrasound, was used for primary clinical decision making and probe guidance, with direct comparison with holographic guidance.

The process begins with preprocedural imaging, including multiphase CT, to record anatomic landmarks and/or coordinate markers placed on a patient’s body. These imaging data are added to a software application that allows for segmentation of the tumor and nearby structures within the marked coordinate space. The segmented anatomical information is then fed into a proprietary AR application, which utilizes Microsoft’s HoloLens technology—an AR headset with transparent lenses—to project a hologram of the patient’s anatomy, electromagnetically tracked instruments such as needles, and live ultrasound imaging directly onto the patient during the procedure. The hologram is registered to the coordinate markers intraprocedurally to ensure accurate location of the relevant anatomy.

Following ablation, images and video from postprocedural sonography, cone beam CT, multidetector row CT, and HoloLens recordings were evaluated. In each case, intraprocedural holographic guidance was in agreement with the standard imaging guidance. Postprocedural imaging showed adequate tumor ablation. In addition, no patients experienced recurrence at the three-month follow-up. Overall, the study authors anecdotally observed that the speed of tumor localization was faster with holographic guidance and their confidence to optimize probe placement and subsequent ablation, along with avoidance of critical structures, was improved over standard imaging guidance.

“This system allows us to locate and treat tumors confidently and more effectively,” Martin says. “This technique can be used intraprocedurally to check the accuracy and quality of the treatment as well as preprocedurally to engage with the patient in their own care. We can change 2D images into holograms of a patient’s distinct anatomy so that both the physician and the patient get a better understanding of the tumor and treatment.”

Additional Applications
Gadodia says the incorporation of any new technology comes with an impact on workflow. While there have been some minor challenges, adding the AR platform to the procedure does not appear to significantly impact the process.

“Our initial study focus was about the usability of the system,” he says. “With any new procedure or technology, there’s the matter of finding the best workflow for the process. Things like having the right materials, correctly positioning required tools, and ideal positioning of the patient are all factors to be considered.”

Another familiar challenge with many percutaneous procedures is how to manage respiratory motion during the procedure. While enhanced image guidance can provide a clear pathway, movement caused by patient breathing remains a challenge during a process that has minimal room for errors and is an avenue for continued innovation.

Gadodia says that the initial abstract was for evaluation of the AR platform in liver tumor ablation, but the researchers have since expanded their assessment and have performed ablations of not only the liver, but also other abdominal soft tissue tumors in more than 10 patients.

“We feel this could be applied in many areas, really anywhere ablation is used,” Martin says. “Notably, the most common cancers treated by ablation are lung cancer, liver cancer, and kidney/renal cancer. Other cancers could also be treated, depending on accessibility and size of tumor. In truth, the hope is that this could be used in any percutaneous procedure or in many other areas, including endovascular procedures or even to assist in surgery. I can even see this being used for any needle-based biopsies. We haven’t found any limitations yet.”

Beyond its use during treatments, interventional radiologists also see value in using this tool for treatment planning purposes as well as improving patient engagement and understanding of the condition and treatment. Realistic images presented at tumor boards can help the multidisciplinary group, even patients and their families, better understand medical conditions, determine a proper course of action, and measure whether treatment has been effective.

Researchers also found benefits to augmented images beyond their initial use during the ablation procedure. “We’re excited to see that, post procedure, we can model ablations out to see the entire area of treatment,” Martin says. “This helps to confirm that you reached and treated the tumor. It gives you additional peace of mind.”

Ongoing Research
As in many areas of medicine, studies such as this are impacted by the continued presence of COVID-19 throughout the country. Researchers are having difficulty securing participants, who are typically hesitant to expose themselves to a clinical environment, for studies. However, especially with the advent and continued implementation of safety measures, some patients, including those with cancer, can and should continue to seek care in hospitals.

“While the momentum of our study slowed in the early months of the pandemic, we have since been fortunate to be able to continue treating our cancer patients safely, including with tumor ablation and, as a result, augmented reality,” Martin says.

The researchers say that further proof-of-concept and data collection are part of the next phase of the study. Gadodia sees quantification of AR’s clinical usability and potential benefits as a key to optimizing the platform and building confidence among interventional radiologists.

“We need to quantify whether augmented reality for tumor ablation is really helping and, if so, how exactly does it help?” Gadodia says. “These are the factors we will be measuring in the next phase of this study.”

In the short term, Martin says the team will continue to look at logistics and efficiency but are also considering applications across different platforms and in treatment locations outside the IR suite.

“Now, we have a better understanding of applying the technology to the patient and locating the real center of the tumor,” he says. “With further study, we can truly quantify the benefits of augmented reality and its applicability in other areas of patient treatment.”

— Kathy Hardy is a freelance writer based in Phoenixville, Pennsylvania. She is a frequent contributor to Radiology Today.