1、NEMA Standards PublicationNational Electrical Manufacturers AssociationNEMA RT 1-2014Gating InterfaceNEMA RT 1-2014 GATING INTERFACE Published by National Electrical Manufacturers Association 1300 North 17th Street, Suite 900 Rosslyn, Virginia 22209 www.nema.org Copyright 2014 by the National Electr
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12、s document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement. RT 1-2014 Page i 2014 National Electrical Manufacturers Association TABLE OF CONTENTS Page Foreword ii Member Company List . iii History iv Section 1 OVERVIEW . 1 1.1 SCOPE 1 1.2
13、 Rationale 1 1.3 References 2 1.3.1 Normative References . 2 1.3.2 Other References 3 1.4 Definitions 3 1.5 Abbreviations . 4 Section 2 GATING INTERFACE . 5 2.1 Concept . 5 2.2 Interface Description 5 2.3 Electrical Signal specifications 6 2.3.1 Connector Pin-out 6 2.3.2 GATING INTERLOCK and BEAM HO
14、LD . 7 2.3.3 RS-422. 9 2.3.4 Cabling. 9 2.3.5 Isolation . 9 2.4 RS-422 Protocol 9 2.4.1 Message Packet Format 9 2.4.2 Data Frequency . 10 2.4.3 Typical Scenario 10 2.4.4 Pre-Beam Check . 12 2.4.5 Signal Cross-Check . 14 2.4.6 BEAM HOLD Verification 14 2.4.7 Plan Verification . 15 2.4.8 Message Packe
15、ts 15 2.4.9 16-Bit CRC Structure . 19 2.5 Gating Timing 19 2.6 Error Handling and Recovery 19 2.6.1 TDD Error Logging 19 2.6.2 PPMS FAIL-SAFE Protection . 20 2.7 Participation in Inapplicable Plans . 20 Section 3 VALIDATION TESTING 21 Section 4 SPECIFICATIONS, INSTALLATIONS AND ACCEPTANCE 22 Section
16、 5 SAFETY AND ESSENTIAL PERFORMANCE . 23 5.1 Interfaces . 23 5.2 Basic Operation . 23 5.3 Essential Performance 23 5.4 Additional Essential Performance Requirements 24 5.5 Essential Performance (QA) 25 APPENDIX A: CRC Algorithm 26 RT 1-2014 Page ii 2014 National Electrical Manufacturers Association
17、Foreword This standard provides a detailed description of the gating interface between Radiation Therapy Treatment Delivery Devices (TDD), commonly called linear accelerators (a.k.a. “linac”) or other particle therapy accelerators and Patient Position Monitoring Systems (PPMS). This standard is inte
18、nded as an interface between TDD and PPMS systems requiring beam gating capability. This standard provides key technical information to developers who wish to connect a TDD to a PPMS. This standard is intended to be used by medical device manufacturers in the design and manufacture of radiation ther
19、apy equipment. This standard was developed by the Radiation Therapy (RT) Section of the Medical Imaging a mechanism that shall not allow an unsafe state to be reached. GATING INTERFACE Signal that allows a gating device to temporarily hold beam generation. INTERLOCK Signal that allows a gating devic
20、e to terminate beam generation. Note that assertion of the Interlock requires operator action to acknowledge the Interlock, and then to resume treatment when the Interlock is cleared at the source. INTERRUPT IRRADIATION A signal issued by the PPMS to the TDD that interrupts irradiation, requiring us
21、er interaction to restart the irradiation. Note: There will be only 1 of these interfaces, and the TDD vendor will decide (and document) the effect of this interface being asserted. RS-422 Differential pair serial communication medium used to transfer information packets between the PPMS and TDD. TE
22、RMINATE IRRADIATION A signal issued by the PPMS to the TDD that prevents irradiation from starting, or immediately terminates the irradiation. Note: There will be only 1 of these interfaces, and the TDD vendor will decide (and document) the effect of this interface being asserted. RT 1-2014 Page 4 2
23、014 National Electrical Manufacturers Association 1.5 ABBREVIATIONS Abbreviation Meaning PPMS Patient Position Monitoring System TDD Treatment Delivery Device RT 1-2014 Page 5 2014 National Electrical Manufacturers Association Section 2 GATING INTERFACE 2.1 CONCEPT The purpose of the GATING INTERFAC
24、E (Figure 1: System Overview) is to provide the TDD and PPMS with the ability to: 1. Hold and restart the treatment beam without operator interaction in response to target motion within the patient or in response to patient position status. 2. Turn the beam off in response to an error condition or p
25、atient status out-of-tolerance condition. This is in line with the IHE-RO Discrete Positioning and Delivery Workflow Profile. This profile requires the Treatment Session Manager to inform both the TDD and the PPMS whether the current treatment session is intended to involve gating of the TDD by the
26、PPMS. The method for specifying gating within a treatment session is within the Motion Synchronization Sequence (300A,0410) in the DICOM-RT RT Patient Setup Module. P P M SB e a m s t a t u sT D D s t a t u s M UB e a m H o l dG a t i n g I n t e r l o c kT D D d a t a :C o n t r o l d a t a :T D DF
27、igure 1: System Overview Two paths of control exist which provide the PPMS with the ability to change the TDD Beam Generation state. Each of these paths is implemented as a hardware signal between the PPMS and TDD. The first control mechanism is the beam gating connection, also known as BEAM HOLD. T
28、his allows the PPMS to temporarily hold the beam without causing a BEAM OFF. The second control mechanism provided is the Gating INTERLOCK. This allows the PPMS to request BEAM TERMINATION (“beam off” the machine, IEC Termination 60601-2-1), or BEAM PREVENTION, if it detects an error. 2.2 INTERFACE
29、DESCRIPTION 1. The TDD shall provide at least one RS-422 serial interface configured for 57.6 kbaud 8-N-1 (8 data bits, no parity, 1 stop bit). The TDD optionally reports the accumulated dose in the RT 1-2014 Page 6 2014 National Electrical Manufacturers Association MU Data serial message sent to th
30、e PPMS. The TDD vendor shall specify the number of PPMS devices which may be concurrently connected and the number of PPMS devices which may be simultaneously involved with treatment delivery. 2. The RS-422 serial communication is a master (TDD)/slave (PPMS) protocol. The TDD sends a dose message to
31、 the PPMS; the TDD expects an acknowledgement from the PPMS. Details regarding the protocol are presented later in this document. 3. The PPMS shall interface to the TDD Gating signal for BEAM HOLD control. 4. The PPMS shall interface to the TDD Gating INTERLOCK signal for BEAM TERMINATION control. 5
32、. The Gating INTERLOCK is the primary mechanism for the PPMS to issue BEAM TERMINATION requests. 6. The PPMS and TDD may transfer any non-real time status (i.e. Patient Information, etc.) in DICOM or other applicable standard in a separate interface. The GATING INTERFACE does not have the capability
33、 or responsibility to transfer patient identifying information. 2.3 ELECTRICAL SIGNAL SPECIFICATIONS This section details the electrical signal specifications of the GATING INTERFACE. 2.3.1 Connector Pin-out The GATING INTERFACE connector shall be a D Sub HD 26 female connector on the TDD side. The
34、connector consolidates RS-422, external INTERLOCK, and external GATING INTERFACEs. Figure 2: Connector Pin-Out RT 1-2014 Page 7 2014 National Electrical Manufacturers Association Pin assignments for all 26 pins. Any pin designated as N/C (not connected) should not be connected to any signals. Pin Na
35、me Comment 1 External Gating Input From PPMS to TDD (BEAM HOLD signal) 2 N/C 3 N/C 4 N/C 5 N/C 6 N/C 7 N/C 8 N/C 9 N/C (Blocked) BlockedThis pin must be removed from the gating devices cable, preventing other 26-pin D-type connectors from being inadvertently being connected to the GATING INTERFACE 1
36、0 External INTERLOCK Input From PPMS to TDD (BEAM TERMINATE signal) 11 N/C 12 N/C 13 N/C 14 N/C 15 N/C 16 N/C 17 N/C 18 VREF_SOURCE +12VDC from TDD to PPMS 19 ISO_GND Equivalent to pin 26 20 N/C 21 RS422_TX+ From TDD to PPMS 22 RS422_TX- From TDD to PPMS 23 RS422_RX+ From PPMS to TDD 24 RS422_RX- Fr
37、om PPMS to TDD 25 N/C 26 ISO_GND Equivalent to pin 19 2.3.2 GATING INTERLOCK and BEAM HOLD O s cO p t o - C o u p l e r s o r O t h e r I s o l a t i o nP i n 1 8P i n 1 0G a t i n g I n t e r l o c kP i n 1B e a m H o l dG a t i n g I n t e r l o c kB e a m H o l dP i n 1 9 o r 2 6( o p t i o n a l
38、 )P P M ST D D+ 1 2 V D CFigure 3: Gating and BEAM HOLD Lines RT 1-2014 Page 8 2014 National Electrical Manufacturers Association 1. The TDD shall provide a current loop supply voltage of +12VDC 5% to the PPMS. 2. The PPMS shall loop back the +12VDC to the port with no more than a 2V voltage drop. 3
39、. Up to 1 kHz switching shall be supported by the INTERLOCK and BEAM HOLD inputs. This does not require that the TDD or PPMS be able to change states at this frequency. This applies to the GATING INTERFACE only. 4. In the TDD and the PPMS a relay such as an electromechanical switch or opto-isolator
40、is recommended for both the Gating INTERLOCK and the BEAM HOLD relays. See Section 2.3.5 for full isolation requirements. 5. The relay should have a resistance when closed of less than 100 ohms. 6. The relay should have a resistance when open of greater than 100 kilo ohms. 7. The relay should have a
41、 stray capacitance when open of less than 100 pF. 8. The relay should withstand transient voltages up to 40 volts and sustained voltages of 15 volts. 9. The relay should withstand transient currents up to 50 mA and sustained currents of 15mA. 2.3.2.1 Gating INTERLOCK The Gating INTERLOCK interface h
42、as the following requirements: 1. Pin 10 is the INTERLOCK input from the PPMS. The PPMS shall connect +12V (pin 18) to pin 10 to release the INTERLOCK, and open this connection to assert the INTERLOCK. 2. The PPMS shall assert the Gating INTERLOCK in the event the PPMS requests BEAM PREVENTION or ab
43、normal BEAM TERMINATION; that is, the PPMS shall open the Gating INTERLOCK circuit. 3. The PPMS shall employ a means of completing the Gating INTERLOCK circuit path when not in use. 4. Pins 19 or 26 can be used for the analog ground reference. 5. The safe state for the Gating INTERLOCK signal should
44、 be normally Open (Asserted). The PPMS should assert the Gating INTERLOCK when a fault is detected or power is not present or lost. 2.3.2.2 BEAM HOLD The BEAM HOLD Interface has the following requirements: 1. Pin 1 is the BEAM HOLD input from the PPMS. The PPMS shall connect +12V (pin 18) to pin 1 t
45、o remove the BEAM HOLD, and open this connection to assert BEAM HOLD. 2. The PPMS shall assert the BEAM HOLD signal in the event the PPMS requires the beam to be held (i.e. no radiation); that is, the PPMS shall open the external BEAM HOLD circuit. 3. When the PPMS is not participating in a treatmen
46、t the BEAM HOLD Signal shall be ignored; however, the PPMS can INTERRUPT IRRADIATION by sending an NAK, or by asserting the Gating INTERLOCK a. Note: The PPMS must still register to the TDD when not in use b. This is not to exclude the possibility of disabling the GATING INTERFACE 4. Pins 19 or 26 m
47、ay be used for the analog ground reference. 5. The safe state for the BEAM HOLD signal should be normally Open (Asserted). The PPMS should assert BEAM HOLD (as well as assert the Gating INTERLOCK) when a fault is detected or power is not present or lost. 6. BEAM HOLD should be closed unless a BEAM H
48、OLD is requested and should only be closed after the Gating INTERLOCK is closed to allow for system redundancy. RT 1-2014 Page 9 2014 National Electrical Manufacturers Association 2.3.3 RS-422 An RS-422 serial communication link running at 57.6 Kbaud 8-N-1 (8 data bits, no parity, 1 stop bit) is use
49、d as the data communication medium between the TDD and the PPMS. This differential pair serial communication type was chosen for cable noise immunity and cable length considerations. The PPMS should have its ground signal connected to Pins 19 or 26 for the analog ground reference. 2.3.4 Cabling The PPMS vendor is required to provide the cable that connects from the TDD to the PPMS. The cable shall be shielded. The RS-422 transmit and receive pairs shall be twisted pair. The shielding shall be grounded connected to the chassis ground by joining the shielding to the cabl
