Using Ultrasound to Combat Liver Tumors

Ultrasound can do much more than record images from the body. Clinicians now use ultrasound to treat tumors. Powerful, concentrated ultrasound waves are focused in the patient’s body to heat cancer cells to 60 degrees Celsius, destroying them and leaving healthy tissue largely unharmed.

Until now, this ‘focused ultrasound therapy’ has only been approved for a small number of diseases, such as uterine tumors and prostate cancer. In the context of the FUSIMO EU project, MEVIS researchers work to expand the application of the method to other organs, such as the liver, which shift in the abdomen during breathing. Now, two years after the beginning of the project, many promising intermediate results have been attained.

Treating the liver with focused ultrasound presents a major problem: The organ shifts back and forth during breathing. This increases the risk that the ultrasound beam path misses the cancer cells and instead heats the surrounding healthy tissue too strongly. For this reason, researchers have only applied this method for patients under general anesthesia. To treat a tumor with ultrasound, the medical ventilator is paused for a few seconds so that the patient remains absolutely still. However, general anesthesia presents its own risks and strains the patient, negating the largest advantage of focused ultrasound therapy – its non-invasive nature.

To solve this problem, the FUSIMO EU project employs a different strategy. If ultrasound therapy for a moving liver can be simulated with a computer as realistically as possible, the likelihood of using such treatment on the organ without general anesthetic rises greatly. Ultrasound treatment would be either activated only when the tumor crosses the focus or by tracking the moving abscess so that it remains in the beam path. FUSIMO, coordinated by Fraunhofer MEVIS, develops the essential software for this vision.

After two years, the project has reached an important milestone: Experts have produced software with which liver operations using ultrasound can be individually simulated for each patient. Magnetic resonance data build the foundation from which 3D images of a patient’s abdomen are generated with additional information about the breathing movements over the time.

Simulations of ultrasound interventions with FUSIMO software are based upon these data sets. To initiate a simulation, researchers enter the time, location, and strength of the desired ultrasound activation. The software created by Fraunhofer MEVIS to efficiently simulate abdominal temperature links two developments: the calculation of ultrasound diffusion provided by the Israeli firm InSightec Ltd. as well as a model of liver movement during breathing from the Computer Vision Lab at ETH Zurich. The software generates an abdominal ‘temperature map’ that indicates whether a moving tumor has been sufficiently heated and whether the surrounding tissue has been damaged. In case of suboptimal results, the simulation can be repeated with different parameters. In the long term, the software could help clinicians plan operations and monitor therapy outcomes.

At the European Radiologist Congress in Vienna, chief radiologist at La Sapienza University in Rome Carlo Catalano stated, “High-intensity focused ultrasound under MRI guidance has become a frequently applied means of treating non-invasive tumors – for example in the treatment of fibroadenoma of uterus and of bone metastases – but treating tumors in moving organs still represents a major challenge due to several complexities.” In this respect, FUSIMO is an exciting project aimed at developing computer simulations for treating the liver with focused ultrasound.

In cooperation with both the Institute for Medical Science and Technology (IMSaT) at the University of Dundee and La Sapienza University, MEVIS experts will refine the software during the remaining project year and validate it by comparing experimental data with results from the simulation, which is necessary for determining how realistically the software performs. In principle, this procedure could be applied to other abdominal organs that are shifted by breathing and difficult to target with the ultrasound beam path, including stomach, kidneys, and duodenum. In addition, specialists are working on a “medicine taxi”: cancer medication enclosed in a small fat globule and inserted into the circulatory system. Focused ultrasound beams function as keys to open the globules when inside tumors in organs such as the liver. This process raises the efficacy of the medicine and minimizes harmful side effects.

About the FUSIMO project:
FUSIMO stands for “Patient specific modelling and simulation of focused ultrasound in moving organs.” The EU project commenced in 2011 and is funded for three years with 4.7 million euro. Eleven institutions from nine countries are involved. FUSIMO is coordinated by the Fraunhofer Institute for Medical Image Computing MEVIS in Bremen, Germany. The second project review by EU experts will take place on March 21 in Brussels.