The RGS Vertex360 was designed to assure the safety of both the patient undergoing treatment and the staff operating in the vicinity of the machine. Selected safety features include:
- Treatment time is accurate to less than 1 second.
- A secondary redundant timer compares the treatment time continuously to the primary timer. In case of a discrepancy, radiation is turned off. The preset irradiation time is displayed on the control console. During irradiation, the remaining treatment time is updated in real-time.
- The switching time from radiation “on” to radiation “off” or vise versa, via the beam plugs, is less than 3 seconds.
Treatment Area & Access
- Only the top portion of a patient’s head (above the base of skull) can fit in the space inside the rotating collimator.
- A hemispherical plastic cap can be mounted on the stereotactic frame support to shield the patient from the moving collimator.
- When the treatment room door is open, the front shield doors cannot be opened by any command or keys.
- Radiation plugs, patient treatment table, and the front radiation-shielding door can also be manually operated.
- All service engineers must be certified and licensed to perform any service.
- Radiation cannot be started when the treatment time is zero.
- Radiation cannot be turned on if the treatment time is greater than 1 hour.
- Radiation cannot be turned on, and radiation will be turned off automatically if already on, under the following situations:
- Treatment table is not in the treatment position, as detected by two redundant limit switches
- Treatment table has moved from the treatment position
- The two timers do not agree within one second
- The rotation of the collimator and the source unit is not in synchrony
- Treatment room is open or opened accidentally during operation
- There is no physical key present to start the radiation; the key must be in the “on” position
- Radiation blocking plugs are implemented to turn beams “on” and “off” at the collimator body. Transient radiation exposures during patient entry into the treatment space and exit from the treatment space are less than 0.5% of the target dose.
- The dose rate at the isocenter when the radiation sources are aligned at the “beam off” position is less than 2% of the treatment dose rate.
Software & Visuals
- A video system allows the patient to be monitored at all the times. An audio system is available so the patient can communicate with the operator.
- UL and CE certified video monitors are used at the console to meet electromagnetic requirements.
- The patient prescription is transferred to the treatment unit via a disk or local network from the treatment planning system. The treatment prescription is displayed and confirmed with a hard copy by the operator before a treatment can be started.
- The control software is stored in a PROM. Each time the power to the system is turned on, a self-test is performed to ensure the functionality of all mechanical parts and sensors. If there is an inconsistency, the unit will not operate.
- The operator can close the front shielding door from the treatment console or inside the treatment room.
- The front shielding door can only be opened in the treatment mode and closed when the treatment table is fully retracted.
- Dual stainless steel source enclosures are used. The source unit, collimator and the back shielding are designed to not separate in common natural disasters such as fires and earthquakes.
- Monthly QA measurements include measuring the radiation dose rate in the treatment space when the sources are in shut position.
- Radiation leakage outside the unit is less than NCRP-33 specified values. An in-room radiation monitor is also installed.
- The maximum radiation leakage when not treating a patient, measured 5 cm from the surface is less than 20 µSv per hour. The dose rate outside of the shielding doors during treatment is less than 2 µSv per minute.
- Qualified medical physicists must design the room shielding. A treatment door switch is used as one of the interlocks. If the door is opened during treatment, the treatment will be interrupted, the patient will be withdrawn from the treatment space, and the front shielding door will be closed automatically.
Power Supply & Motors
- The gamma-ray treatment unit is equipped with an UPS system. If power is interrupted, the backup power can sustain at least 30 minutes of operation, ensuring a treatment can be completed if already started. The status of the UPS system is monitored in real-time.
- A treatment cannot be started if the UPS system is faulty. Enough battery power is always reserved for shutting off the primary radiation beams, withdrawing the couch, and closing the front shielding door.
- All power or signal lines from the control console to the treatment unit are limited to less than 30V DC.
- In the case of loss of main power, there is a backup power system that can ensure at least 30 minutes of treatment time, shut off the radiation and retrieve the patient from the treatment space.
- The status of the backup power source is monitored in real-time when the system is turned on. If the backup power source has insufficient power reserve, a treatment procedure cannot be started.
- The power to the control console (except the monitors) is limited to less than 30 VDC. The power cabinet does not require operator/user intervention. Qualified service engineers perform the service to the power cabinet.
- All motors are 24VDC master-slave motors, with torque sufficient for performing its intended operation. The torque of the motors is limited to prevent mechanical failures.
- Each motor drive and control unit has separate current limiting devices.
Interruption & Manual Operation
- The system features an interrupt button on the control console to suspend radiation and all movements. An interrupted treatment can be re-started by the operator on the control console or the remaining treatment time and setting can be saved in the control unit and resumed at a later time.
- There is an a emergency button on the control console which terminates the treatment, saves the untreated portion, withdraws the patient from the treatment space and turns the power off.