INNOVATION
Elekta’s sixth generation digital linac control system tailor-made for VMAT delivery
E
lekta VMAT has enabled customers to treat patients rapidly using dynamic arcs that can be completed in two minutes. However, in treatments that require numerous and varied changes in dose rate as the arc traverses, the gantry speed can change greatly, thereby extending the treatment time. This is caused by only having a few discrete dose rate settings.
“Over the course of an arc, multiple dose rate changes cause the gantry to slow down and speed up as the linac control system ensures that the correct dose is being given,” says Alison
“With Integrity, we will save a lot of time in Elekta VMAT cases. With the CVDR (continuously variable dose rate) linac feature, we have calculated a time-savings of one to two minutes per patient or a treatment time reduction of 25-30 percent. One to two minutes might not seem like much but if you have 25 patients on the schedule you gain almost half an hour.” Henrik Jensen, Ph.D. physicist at Odense University Hospital
“Integrity speeds up the whole process. We are achieving Elekta VMAT treatment times of between two and five minutes for most indications which is directly attributable to the continuous dose rate feature. Integrity also enables faster control of the MLC. Together, Integrity seems to shave 30 percent off of the treatment time.” Frank Lohr, M.D., vice chairman of University Medical Center, Mannheim (Germany)
58 nhe
Metcalfe, delivery solutions product manager. “Rather than a smooth sweep, the gantry motion can be jerky which in turn slows down the treatment delivery time.”
Integrity’s new continuously variable dose rate moves treatment delivery away from binned doses to fine resolution changes in the dose rate delivery. By moving to a smoother delivery technique, higher doses are maintained with the result of smoother patient flow and improved patient throughput. With this latest advance, efficiency of VMAT delivery is further enhanced.
MLC interdigitation enables creation of target islands Integrity™
from Elekta offers the
users the ability to interdigitate leaves giving users the option to treat multiple targets in one field. This is available in systems equipped with the Elekta MLCi2 treatment head.
Interdigitation enables clinicians to plan target islands, as leaves on opposing MLC banks are able to interdigitate or slide past one another. Interdigitation is an effective way to treat brain metastases while limiting the dose to surrounding tissues.
Similarly, many head and neck targets will benefit from interdigitation through the creation of dose islands that shield critical structures such as the parotid, optic nerve and spinal cord.
Safety confidence
Integrity employs three tiers of safety for absolute confidence in the delivery of radiation dose.
·
The first tier verifies the prescription when it is received from an external system like MOSAIQ®
.
Integrity is a smart control that checks all the linear accelerator parameters are deliverable and that they
are set correctly according to the prescription. This intelligent control will reject untreatable plans before the patient gets on the table or a QA procedure starts.
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The second tier checks and controls the MLC leaves and the dose delivery on a regular basis, within milliseconds of each other, to ensure that real-time adjustments are made to keep the prescription on track and precise.
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Overseeing all of this is the third tier, Guardian, which supervises and checks that all the systems are operating correctly. It does this by constantly monitoring and verifying control points throughout treatment, including MLC and gantry parameters. If a discrepancy occurs, Guardian will stop the treatment. No other linear accelerator control system offers these layered, fail-safe technologies.
Nov/Dec 10
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