October 4, 2012 — Less than three months after beginning clinical use of their Elekta Agility 160-leaf multi-leaf collimator (MLC), physicians at The James Cook University Hospital in Middlesbrough, England, have achieved another benchmark – their first use of Agility to deliver radiation therapy employing Elekta's volumetric modulated arc therapy (VMAT). The ability to accelerate both beam shaping and beam delivery with Agility and VMAT cut 57 seconds off the beam delivery time for the first patient, a 61-year-old male with prostate cancer.
Using twice the number of leaves typical of many standard MLCs, Agility precisely sculpts delivered radiation to the distinctive contours of the tumor, while reducing the risk of exposure to healthy normal tissues. Agility also includes ultra-fast leaf movements – twice as fast as other MLCs commonly used in the industry. Agility complements rapid beam delivery techniques, such as VMAT, in which single or multiple radiation beams sweep in one or more uninterrupted arcs around the patient, reducing treatment times significantly.
On Aug. 8, the patient received his first treatment fraction, a single 200-degree VMAT arc, which took just 83 seconds to deliver. In comparison, a three-field 3-D conformal treatment would have taken 140 seconds (2:20 minutes) to deliver, demonstrating a 40.7 percent reduction in beam delivery time with Agility/VMAT. When factoring in image guidance, the total treatment timesavings with Agility/VMAT was 72 seconds (1:12 minutes).
"This was our first experience with VMAT and it went very well," said Christopher Walker, head of radiotherapy physics at The James Cook University Hospital. "The treatment speed not only reduces the likelihood that the patient will move and that the internal organs will shift position, but it also contributes to faster patient throughput, which is key. With Agility/VMAT we expect to be able to treat five patients per hour."
A new version of Monaco (v 3.20) was used to plan the first Agility/VMAT case. "We used PIVOTAL trial dose constraints, achieving good coverage of the target and optimal sparing of the rectum and bladder," Walker said. "It was a significant improvement over our previous 3-D conformal planning."
The image guidance technology on their Elekta Synergy treatment system also was critical for ensuring accuracy. "We wouldn't have done the treatment without the cone beam CT [computed tomography] on the Synergy system," he added. "Through image guidance we identified movement of the target volume before treatment delivery on the first day, which resulted in us re-planning the patient before subsequent treatments."
With the successful launch of Agility/VMAT at The James Cook University Hospital, clinicians there have begun treating a second prostate patient and a third is on the schedule. "We're now open for business as far as prostate VMAT is concerned," Walker said. "Looking ahead, we will be expanding out to other sites in the body over the next few months."
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For more information: www.elekta.com/agility