YY/T 1711-2020Gating interface used in radiation therapy (English PDF)

3.1 Beam hold

The state in which the system is ready to quickly resume beaming on but has not been beaming on.

NOTE 1: Beam hold and interrupt irradiation (the equipment changes to the beam-off state) are not the same.

NOTE 2: Beam hold is a sub-state of the irradiation state, and its purpose is to quickly transform into the expected therapeutic irradiation state.

NOTE 3: It is usually used in gating, IMRT, etc.

3.2 Beam off

The radiation source is completely shielded and in a safe protective position. [GB 9706.17-2009, Definition of 2.101]

3.3 Beam termination/terminate irradiation

The signal that is transmitted from the PPMS (Patient Position Monitoring System) to the TDD (Treatment Delivery Device) to prohibit the start of irradiation or to immediately terminate irradiation.

NOTE: TDD in this standard mainly includes medical electron accelerators, light ion therapy systems, gamma ray beam stereotactic radiotherapy systems, cobalt 60 remote machines, and other equipment;

PPMS mainly includes optical surface, X-ray transmission, abdominal pressure, magnetic field signals, ultrasound imaging, magnetic resonance imaging, and other position monitoring systems.

3.4 Gating interface

The purpose of the gating interface is to enable TDD and PPMS to have the following capabilities:

a) Perform beam hold or "beam termination/terminate of irradiation" according to the movement of the target area in the patient's body or the position of the patient without operator intervention.

b) Switch off the beam in case of error or patient status exceeding deviation limits.

NOTE: PPMS can change the beam generation state of TDD through two control methods. Both require hard wiring between PPMS and TDD. The first type is beam gating connection, which is beam hold. It allows the PPMS to temporarily maintain the beam without triggering the beam off. The second type is gating interlocking. It allows the PPMS to require beam termination (i.e., beam off in GB 9706.5-2008) or prohibit beam-on when an error is detected.

3.5 Interlock

A setting that prevents a device from starting or continuing operation under unspecified conditions.

NOTE: A signal that causes the gating device to terminate the beam. Note that when an interlock occurs, the operator is required to take action to confirm the interlock and then resume the treatment after the interlock is cleared. [IEC/TR 60788:2004]

3.6 Interrupt irradiation

The PPMS sends the signal for interrupt irradiation to TDD, and the restart of irradiation requires user intervention.

4.4 Gating time

The TDD manufacturer should provide the minimum value of the beam hold time and other restrictions, and the PPMS manufacturer should provide the corresponding configuration.

4.5 Error handling and recovery

4.5.1 TDD error log

If the gating interlock causes abnormal beam termination, TDD shall record it in the event log.

4.5.2 PPMS fail-safe protection

When the PPMS requests abnormal beam termination or the system is in a fault state, the PPMS shall be required to:

a) Trigger external gating interlock. Whenever the gating interlock is triggered, TDD shall implement beam off.

b) Trigger an external beam hold signal to complete beam gating (if applicable).

c) Provide status checking of the communication mechanism (if applicable).

TDD will implement beam off (or interrupt irradiation) after receiving the PPMS error states.

PPMS manufacturers shall design logging and inspection capabilities in their products to effectively analyze potential gating interface errors or failures (if applicable).

4.6 Basic operation and basic performance

The interface design between TDD and PPMS can include but is not limited to the following functions:

a) The gating interface shall not interfere with the operator's initialization of treatment or imaging procedures.

b) With the help of a gating interface, PPMS allows beam hold and "beam termination/terminate irradiation" without additional operator intervention.

c) Gating interfaces shall not prohibit the use of therapeutic irradiation and imaging equipment without the functionality of the PPMS monitoring equipment.

d) If provided, the two interfaces "beam hold" and "beam termination/terminate irradiation" shall be independent of each other.

e) If provided, before irradiation, TDD shall check to ensure that the functions of beam hold and "beam termination/terminate irradiation" are correct.

f) Before irradiation, the PPMS shall check to ensure that it can operate the signal of the beam hold. This inspection shall be performed before the PPMS releases the "beam termination/terminate irradiation" interlock.

g) Before irradiation begins, the PPMS shall perform an end-to-end beam hold and "beam termination/terminate irradiation" signal check by actually activating the (open circuit or "fail-safe") switch and receiving a confirmation signal from the TDD, and then it can release the "beam termination/terminate irradiation" interlock.

h) If the PPMS cannot work properly, the "beam termination/terminate irradiation" interlock for fail-safe shall inhibit beam start by default. Any apparent PPMS error shall inhibit the activation of the treatment beam.

i) If the PPMS can receive and respond to beam irradiation information (beam hold state or MU of the beam-on), it shall be expected that, after the beam hold request is sent, the PPMS can trigger the beam termination interlock when it notices that the TDD has not switched to the beam hold state, or MU is still increasing.

j) Both PPMS and TDD shall have continuous interface checks. If TDD detects that the PPMS does not respond to messages within the expected time period, TDD should terminate beam-on within a specified time period. If the PPMS detects a situation that affects the operation of the gating interface, the PPMS shall trigger the "beam termination/terminate irradiation" interlock within the specified time period.

k) If the action of the gating interface exceeds the stated performance limits (for example, the "maximum beam hold period" stated in the accompanying documents provided by the TDD manufacturer is exceeded), the TDD shall be allowed to terminate the beam.

NOTE: The beam termination mentioned here can be a complete beam termination (resulting in an incomplete beam-on) or switching to a paused irradiation state that requires user intervention to resume beam-on.

l) If the PPMS has triggered the "beam termination" interlock and detects that the beam is still in progress (that is, the beam termination signal does not work), the PPMS shall give an alarm signal of this failure mode to alert the operator.