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News Americas

3-D image of an abdominal aortic aneurysm in different colors according to the respective diameter. (Image: Dr. Claude Kauffmann, University of Montreal Hospital Research Centre)
0 Comments Oct 29, 2015 | News Americas

Novel method to treat aortic aneurysms uses modern imaging technologies

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MONTREAL, Canada: Researchers at the University of Montreal Hospital Research Centre and the university's Department of Radiology, Radiation Oncology and Nuclear Medicine have developed a novel treatment approach for patients with abdominal aortic aneurysms. The researchers’ new method, using 3-D models and virtual reality simulations, addresses the issue of problematic visualization of the area needing treatment.

For 25 years, Dr. Gilles Soulez, a researcher at the University of Montreal Hospital Research Centre and a professor at the university's Department of Radiology, Radiation Oncology and Nuclear Medicine, has been involved in developing medical imaging technologies to prevent complications of, operate on, and monitor patients with abdominal aortic aneurysms. The main problem has been the ability to properly visualize the area to be treated. "Remarkable advances in imagery have improved surgery and helped to develop less invasive interventions. But the images are still far from being perfect. We want to develop new software to maximize the use of images generated with current ultrasound, scanning, and magnetic resonance imaging (MRI) technologies to ultimately provide more personalized treatments," he explained.

The abdominal aorta is a large blood vessel that begins at the heart and travels down to the abdomen, distributing blood throughout the body. Abdominal aortic aneurysms are enlarged areas shaped like a small balloon that are caused by the weakening of the vessel wall. Linked to atherosclerosis risk factors such as hypertension and smoking, the disease is the 13th most common cause of death in North America. It especially affects men. "If you have a ruptured aneurism, you have a one in two chance of dying," Soulez stated.

Currently, a simple abdominal ultrasound or measurement of the aorta with a scanner can detect patients at risk of aneurysm rupture. Beyond 5 cm for women and 5.5 cm for men, surgery is usually recommended. However, as operations are not completely without risk, researchers are aiming to refine screening to provide the most appropriate treatments for patients who really need surgery.

In order to avoid rupturing the small balloon formed by the abdominal aortic aneurysm, two treatment options exist: open surgery to replace the diseased section or endovascular grafting, in which a catheter is inserted in the groin to deliver a stent graft through the blood vessels to the aneurysm. This option is less invasive, but in some patients the morphology of the aneurysm is not suited to this kind of treatment. Using scanner images, Soulez's research provides 3-D models of all components of the aneurysm, including the light, thrombus or clot, wall and calcification. "The grid is used to establish growth profiles of the aneurysm. We are now working to create simulations to better predict the risk of rupture, adding biomechanical properties such as tissue elasticity and connectivity at each pixel of the grid," he explained.

According to Soulez, simulations will help in the operating room too. Currently, the operation is performed using static images taken by a scanner before the procedure. The procedure itself is done under fluoroscopy by injecting dye into the vessels to be treated. "The image produced by X-ray shows the dye in the vessels and the stent being inserted, but not the wall. This approach requires a lot of dye, which can be toxic for the patient if used in excessive amounts," the radiologist said.

With its new approach, Soulez's laboratory has been able to combine all of the available data. "We superimpose the images, and this helps to visualize the area to be treated. But in reality, the tools we introduce into the body during the procedure deform the organs. We are testing at the University of Montreal Hospital Research Centre and in Halifax right now a new approach that uses a computer to automatically recognize the tools introduced into the body and correct the deformities they cause," he said. "We hope this simulation operation model will improve the accuracy of the procedure."

Soulez's research in interventional radiology also aims to ensure that the stent graft fits well and does not leak, as a leak could cause an aneurysm rupture. Therefore, following the stent graft operation, patients have an annual scan. A new ultrasound technology called elastography, which was developed in collaboration with Dr. Guy Cloutier, also of the University of Montreal Hospital Research Centre, holds the potential to both identify leaks effectively and evaluate healing of the aneurysm. Moreover, Soulez and his team are developing new biomaterials, such as bioactive stents and a gel to inject around the implant to prevent or stop leaks, to improve the possibilities of endovascular repair further.

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