To support better radiation targeting accuracy, the Leeds Teaching Hospitals NHS Trust rolls out cutting-edge technologyLeeds United Kingdom — Monday, October 18, 2010
A 67-year-old female patient with lung cancer presented physicians with a difficult challenge: her tumor was small and it rode up and down with her breathing. During her treatment set up, all doctors saw on their therapy system’s imaging equipment was a blur of motion. Fortunately, Leeds Teaching Hospitals NHS Trust was able to utilize its Symmetry™ motion management software ; new imaging technology from Elekta that enables clear visualization of moving targets.
“For this patient, and many similar lung cancer cases, Symmetry is invaluable,” says her physician, Kevin N. Franks, M.D., Consultant in Clinical Oncology at St. James Institute of Oncology, Leeds Teaching Hospitals NHS Trust. “Our first patient's tumor was just 1.4 cm in size and its range of motion when she breathed was 2.4 cm because it was close to her diaphragm. Treating a small tumor with this kind of motion would normally have excluded her from aggressive treatments such as Stereotactic Body Radiation Therapy [SBRT], particularly if you can’t see it well on imaging studies.”
Symmetry provided sufficient scan quality to isolate the “moving” tumor and the patient—the first at Leeds to benefit from the technique—received five SBRT treatments , which use precise stereotactic targeting and a potent dose designed to achieve control of the tumor.
Symmetry captures tumor position virtually invisible on static imaging
Symmetry is a feature set of Elekta’s X-ray Volume Imaging (XVI) package of software for Image Guided Radiation Therapy (IGRT). The software enables clinicians to add the fourth dimension (i.e. 4D) of motion to enhance image guidance with the patient in the treatment position just before therapy.
Leeds physicians had been able to use their 4D CT scanner to observe the tumor moving with the patient’s breathing. However, they were able to see only an ill-defined blur when they used 3D XVI on their Elekta Synergy® system .
“It’s like trying to take a picture of a fast-moving object using a camera that has a slow shutter speed,” says Jonathan Sykes, Joint Lead Radiotherapy Imaging Physicist at Leeds. “But by taking the 4D CT planning scan—which showed the ‘envelope’ of space within which the tumor was moving—and matching that to 4D Symmetry reconstructions, which show where the tumor is during the breathing cycle, the scan quality was sufficient to localize the tumor.”
After this first localization, three-minute 4D Symmetry scans were repeated three times for each of the five treatment sessions to localize the tumor, a second scan to verify needed patient position corrections and a third scan to ensure proper patient immobilization. Of note, the treatments are delivered while the patient is breathing freely.
“The 4D-XVI scan allowed us to see the tumor clearly and check that the tumor motion had not changed from the planning 4D CT scan. It made the team confident of the tumor localization,” Dr. Franks says. “Without Symmetry, SBRT might still have been possible as the tumor was distant from critical organs, but we would have had to increase the treatment margins around the tumor to account for the increased uncertainty about the tumor’s position. The worst case scenario is not using SBRT and treating her with a conventional technique that is likely less effective.”
Since this first patient, Leeds physicians have used Symmetry in treatments of three additional patients with lung cancer. To download a case study detailing the application of Symmetry at Leeds, visit www.elekta.com/proof .
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