Commissioning and training with the Respiratory Gating Platform provides validation of the TPS and the proper administration of gated IMRT treatments.
The Respiratory Gating Calibration System is a convenient way to quickly:
|Height||12.7 cm (5 in)|
|Width||30.5 cm (12 in)|
|Length||76.2 cm (30 in)|
|Weight||9.1 kg (20 lbs)|
|Period of Oscillation Control||2 - 6 sec, 0.5 sec increments|
|Accuracy||± 0.2 second when using: |
4 Standard Imaging IMRT Phantom slabs (~34 lbs.)
6 Standard Imaging IMRT Phantom slabs (~51 lbs.)
8 Standard Imaging IMRT Phantom slabs (~68 lbs.)
|Repeatability||± 0.1 second for 4, 6 or 8 Standard Imaging IMRT Phantom slabs|
|Range of Motion Control||5 mm - 40 mm, with 5 mm increments|
|Accuracy and Repeatability||± 0.5 mm|
|Power Requirements||12 VDC @ 1.25 A, power supply included|
|DC Output||Use only Globtek®, Inc power supply model GTM21089-1512-T3|
Below are two respiratory examples; both are only interested in treating the blue hatched region between the two green dashed lines – a typical amplitude-gated-treatment-window. The top example is a simple sinusoidal motion, while the bottom example has a cyclical pattern with added irregular motion.
In either case, the tumor is free to move in any dimension and at any displacement during the inhale/exhale portion of a breath cycle. Regardless of this freedom, the tumor returns to its “home position” during the exhale/inhale transition at the end of each breath. This home position is the gating-treatment-window shown by the green dashed lines. This is a logical point along a breath cycle to treat a tumor because its motion, in three dimensions, is at a minimum and confidence in the tumor position is strongest. This can be confirmed with a fluoroscopy. Whatever motion the tumor experiences outside the gating-treatment-window is irrelevant because the Varian RPM™ camera is always monitoring the belly motion. Only when the belly (and therefore the tumor) is in the correct position, is irradiation applied.
While it is true a 2D or 3D movable platform will more accurately represent the tumor displacement through the entire breath cycle – one is only interested in treating the tumor when it is returning to and immediately leaving the gating-treatment-window. With tumor motion at a minimum and position established within this window, subtle positional hysteresis in tumor motion can be accounted for in PTV planning. A simple 1D motion platform is more than adequate to show that the target has left and returned to the gating-treatment-window. What the tumor does outside of the gating-treatment-window is of no consequence to the respiratory gating treatment planning or validation.
RPM™ is a trademark of Varian Medical Systems.
While the Respiratory Gating Platform is optimized to work best with the Standard Imaging IMRT Dose Verification Phantom, it can also support other phantoms. An optional Respiratory Gating Platform Securing Kit (REF 70150) is available for securing other phantoms to the platform, however a different IMRT phantom may have a weight that will alter the platform’s timing. Timing of the platform with alternate phantoms should be verified to ensure accuracy.
Yes, an optional Respiratory Gating Platform Securing Kit (REF 70150) is available for using most slabs, however this accessory will only secure the platform to the bottom-most slab. We suggest fastening the phantom slabs together around their circumference with tape or other means to ensure they cannot separate while the platform is in motion.