The RGS Orbiter and its unique design represent a significant departure from previous radiosurgery devices. The rotating capabilities of the C-arm gantry and the linear movements of the treatment table allow for full 360° radiation reach and tumor targeting. The RGS Orbiter treats small and mid-sized lesions of the head, neck and spine with pinpoint precision and accuracy.
The treatment head houses 42 cobalt-60 sources arranged in a single line over a circular segment of ± 25°, as seen from the isocenter around the patient’s length axis when the table is in the home position. Initial source activity is 6,000 Ci ± 10%.
|Initial source activity||6000 Ci ± 10%|
|Total number of sources||42|
|Individual source activity||142.85 Ci|
|Dose rate||Max 3 vGy/min|
|Penumbra||≤ 10 mm|
|Collimator sizes||6 x 6, 8 x 8, 14 x 14, 14 x 20, 14 x 40, 14 x 60 mm|
|Sources distribution range||50 degrees|
|Isocenter height to the ground||900 mm|
|Dose & mechanical isocenter overlapping accuracy||≤ 0.5 mm|
The RGS Orbiter system is comprised of the following components:
Gantry, treatment table and treatment head with source and source block
Contains the source unit, changeable collimating mechanisms, treatment table and shielding structure. There are six groups of collimators: 6 x 6 mm, 8 x 8 mm, 14 x 14 mm, 14 x 20 mm, 14 x 20 mm and 14 x 60 mm.
The source block also serves as the primary collimator; it is motor driven and moves in a linear fashion. The maximum travel distance is 92 mm. It takes two seconds to shut the source completely off. In an emergency situation, the source can be shut off in less than one second. The beam can be shut off while changing the collimators or when the machine is not in use.
The secondary collimators of varying sizes are approximately 7–8 kg each and are easily changed by a single person. The collimator is engaged into the treatment head and locked. When a collimator change is needed, the unit is unlocked and the collimator is easily removed. When changing the collimators, the sources are blocked and the max dose leakage at the surface of treatment head is less than 100 µGy/h.
The control system integrates the user interface, electrical hardware and control software.
Radiation Protection and Operation Safety System
Includes video system, intercom system, radiation alarm system, interlocks and control panel.
Stereotactic Localization System
Contains localizer frames for imaging modalities and the head and body frames for the treatment table. The headframe is affixed to the patient’s head during the CT/MRI and radiosurgery procedures.
The CT and MRI frames contain coordinate markers, which are visible on the CT and MRI images. Using the fixed marker locations on the images and delineating the target and normal structures on the images, the head’s anatomical geometry is defined in a coordinate system. When the head frame is mounted on the headframe ring, the entire fixation system can be rotated and shifted as delineated in the coordinate system to place the target at the focal point of the γ-ray beams.