LEEDS, England, Nov. 22, 2011 /PRNewswire/ -- Setting the pace in the United Kingdom for lung SBRT treatments, clinicians at the St. James's University Hospital are becoming increasingly adept in managing respiratory motion and accurately targeting mobile lung tumors, a difficult task before the introduction of advanced technology. For many of the more than 200 patients treated, St. James's doctors have used Elekta's Symmetry™ solution, 4D image guidance technology that enables clear visualization of moving targets.
"For certain patients with lung tumors that move a large amount during breathing, Symmetry 4D cone beam CT [CBCT] has been incredibly useful," says John Lilley, physicist at St. James's, part of The Leeds Teaching Hospitals NHS Trust.
"The standard 3D volume imaging system (3D CBCT) on our Elekta Synergy® treatment machine is great for imaging targets that remain still, but moving objects – become blurred," he explains. "However, by taking the 4D CT planning scan – which shows the 'envelope' of space within which the tumor is moving – and matching that to 4D Symmetry reconstructions, which show the tumor's position during the breathing cycle, we can more easily localize moving tumors."
Symmetry goes from part-time to full-time
Previously, St. James's clinicians had been using the capabilities of Symmetry only in three specific instances: 1) cases in which considerable tumor motion was observed in the planning 4D CT scan, 2) if the 3D CBCT images did not provide clear tumor visualization or 3) if the planning 4D CT did not resolve the tumor sufficiently, requiring clinicians to use Symmetry to check tumor motion. Recently, though, they have incorporated Symmetry for all lung cancer cases two days before the patient officially begins treatment ("Day 0"), according to Kevin N. Franks, M.D., Consultant in Clinical Oncology at St. James's.
"We're doing it for all patients now to verify that the 4D planning CT scan truly represents the tumor's motion and to assess whether 4D CBCT is superior for matches for any patient," he says. "In addition, for patients whose planning 4DCT was sub-optimal we use 4D CBCT to clarify tumor motion earlier in the planning process and adjust the ITV margins if required."
For many patients, after the Day 0 scan, no further Symmetry scans are required if doctors determine that the extent of tumor motion is minimal, the use of Symmetry for every treatment session is unnecessary. However, for patients with mobile tumors, typically smaller tumors and/or those close to the diaphragm, Symmetry scans are repeated up to three times for each of the five SBRT treatment sessions. The first scan is to localize the tumor, the second to verify needed patient position corrections and a third to ensure proper patient immobilization. Notably, the treatments are delivered while the patient is breathing freely.
"For tumors with significant motion, particularly small tumors, it had been very difficult to match up with the 4D planning CT using 3D CBCT on the treatment system," Dr. Franks recalls. "Symmetry has been invaluable for this group of patients."
Advanced registration tool further protects critical structures
St. James's clinicians also have been using Intuity™, suite of advanced image guidance tools. Intuity provides the capability to ensure that not only is the tumor's position accurately accounted for, but also the position of nearby critical structures.
"The dual registration capability of Intuity enables us to set tolerances for organs-at-risk to avoid putting critical structures in the radiation beam's path," Dr. Franks says. "We had been using it in an offline way, but next month we will incorporate Intuity dual registration in a prospective, online way with Symmetry. In this way, we can work out tolerances so that when we go to the treatment it will be quicker and more streamlined."
Symmetry and Intuity are feature sets of version 4.5 of Elekta's X-ray Volume Imaging (XVI) software solution for Image Guided Radiation Therapy (IGRT). To learn more, visit www.elekta.com/symmetry and www.elekta.com/intuity.
Approval of indications may vary between different countries. Additional regulatory clearances may be required in some markets.
Elekta is a human care company pioneering significant innovations and clinical solutions for treating cancer and brain disorders. The company develops sophisticated, state-of-the-art tools and treatment planning systems for radiation therapy, radiosurgery and brachytherapy, as well as workflow enhancing software systems across the spectrum of cancer care. Stretching the boundaries of science and technology, providing intelligent and resource-efficient solutions that offer confidence to both healthcare providers and patients, Elekta aims to improve, prolong and even save patient lives.
Today, Elekta solutions in oncology and neurosurgery are used in over 6,000 hospitals worldwide. Elekta employs around 3,300 employees globally. The corporate headquarters is located in Stockholm, Sweden, and the company is listed on the Nordic Exchange under the ticker EKTAb. Website: www.elekta.com.
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