Section R12-1-905. Medical Particle Accelerator Equipment, Facility and Shielding, and Spot Checks

A.      Equipment

1.        Leakage radiation

a.         X-ray leakage radiation from  the source housing assembly shall not exceed 0.1 percent of the maxi- mum dose equivalent rate of the unattenuated useful beam.

b.        Neutron leakage radiation from the source housing assembly shall not exceed 0.5 percent of the maxi- mum dose equivalent rate of the unattenuated useful beam.

c.         Leakage radiation measurements made at any point

1  meter  from  the  path  of  the  charged  particle between its point of origin and the target, window or

scattering foil shall meet the requirements of subsec- tion (A)(1)(a) and (b) when computed as a percent- age of the dose rate equivalent of the unattenuated useful beam measured at 1 meter from the virtual source. Leakage radiation measurements at each point shall be averaged over an area up to but not exceeding 100 square centimeters (15.5 square inches).

d.        The registrant shall maintain, for inspection by the Agency, records that show leakage radiation mea- surements for the life of the operation.

2.        Beam limiting devices (not to include blocks or wedges). Adjustable or interchangeable beam limiting devices shall be provided and shall transmit no more than 2 per- cent of the useful beam for the portion of the useful beam that is to be attenuated by the beam limiting device. The neutron component of the useful beam shall not be included in this requirement. Measurements shall be averaged over an area up to but not exceeding 100 square centimeters (15.5 square inches) at the normal treatment distance.

3.        Filters. The following requirements apply to systems that use a system of wedge filters, interchangeable field flat- tening filters, or interchangeable beam scattering filters:

a.         Irradiation shall not be possible until a selection of a filter has been made at the treatment control panel;

b.        An interlock system shall be provided to prevent irradiation if the filter selected is not in the correct position;

c.         An indication of the wedge filter orientation with respect to the treatment field shall be provided at the control panel, by direct observation, or by electronic means, when wedge filters are used;

d.        A display shall be provided at the treatment control panel showing the filter or filters in use;

e.         Each filter that is removable from the system shall be clearly identified as to that filter’s material of construction, thickness, and the nominal wedge angle for wedge filters, or a record tracing these fac- tors for each filter shall be maintained at the system console; and

f.         An interlock shall be provided to prevent irradiation if any filter selection operation carried out in the treatment room does not agree with the filter selec- tion operation carried out at the treatment control panel.

4.        Beam monitor. Equipment installed after the effective date of this Section shall be provided with at least one radiation detector in the radiation head. This detector shall be incorporated into a primary system so that all of the following criteria are met:

a.         Each primary system shall have a detector that is a transmission detector and a full beam detector and that is placed on the patient side of any fixed added filters other than a wedge filter;

b.        The detectors shall be removable only with tools and shall be interlocked to prevent incorrect positioning;

c.         Each detector shall be capable of independently monitoring and controlling the useful beam;

d.        Each detector shall form part of a dose-monitoring system from which the absorbed dose can be calcu- lated at a reference point in the treatment volume;

e.         Each dose monitoring system shall have a legible display at the treatment control panel that:

i.         Maintains a reading until intentionally reset to zero;

ii.        Has only one scale and no scale multiplying factors in replacement equipment; and

iii.      Utilizes a design such that increasing dose is displayed by increasing numbers and is designed so that, in the event of an overdosage of radiation, the absorbed dose may be accu- rately determined under all nominal conditions of use or foreseeable failures;

f.         In the event of power failure, the dose monitoring information required in subsection (A)(4) displayed at the control panel at the time of failure shall be retrievable in at least one system; and

g.        Selection and display of dose monitor units;

i.         Irradiation shall not be possible until a selection of dose monitor units has been made at the treatment control panel.

ii.        Each primary system shall terminate irradiation when the preselected number of dose monitor units has been detected by the system.

iii.      Each secondary system shall terminate irradia- tion when 110 percent of the preselected num- ber of dose monitor units has been detected by the system.

iv.       It shall be possible to interrupt irradiation and equipment movements at any time from the operator’s position at the treatment control panel. Following an  interruption, it shall be possible to restart irradiation by operator action without any reselection of operating conditions. If any change is made of a preselected value during an interruption the equipment shall go to termination condition.

v.        It shall be possible to terminate irradiation and equipment movements, or go from an interrup- tion condition to termination conditions at any time from the operator’s position at the treat- ment control panel.

5.        Beam monitoring system. All accelerator systems shall be provided with a beam monitoring system in the radia- tion head capable of monitoring and terminating irradia- tion.

a.         Each beam monitoring system shall have a display at the treatment control panel that registers the accu- mulated monitor units.

b.        The beam monitoring system shall terminate irradia- tion if the preselected number of monitor units has been detected by the system.

c.         For units with a secondary beam monitoring system, the primary beam monitoring system shall terminate irradiation if the preselected number of monitor units has been detected. The secondary beam moni- toring system shall terminate irradiation if the pri- mary system fails.

d.        In the event of a power failure, the display informa- tion required in  subsection (A)(5)(a) shall be retained in at least one system following the power failure.

e.         An interlock device shall prevent irradiation if any beam monitoring system is inoperable.

f.         For purposes of this rule:

i.         “Beam monitoring system” means a system of devices that will monitor the useful beam during irradiation and will terminate irradiation if a preselected number of monitor units is accumulated.

ii.        “Monitor unit” means a unit response from the beam monitoring system from which the absorbed dose can be calculated.

6.        Treatment beam mode selection. In equipment capable of both x-ray and electron therapy:

a.         Irradiation shall not be possible until a selection of radiation type is made at the treatment control panel;

b.        An interlock system shall be provided to prevent irradiation if any selected operations carried out in the treatment room do not agree with the selected operations indicated at the treatment control panel;

c.         An interlock system shall be available and in operat- ing condition on a therapy machine, and shall be used to prevent unwanted x-ray or electron irradia- tion when preparing for, or performing radiation therapy procedures. The interlock system need not be available for use, if the therapy machine is only used to make an image of an inanimate object; and

d.        The radiation type selected shall be displayed at the treatment control panel before and during irradia- tion.

7.        Treatment beam energy selection. Equipment capable of generating radiation beams of different energies shall meet all of the following requirements:

a.         Irradiation shall not be possible until a selection of energy is made at the treatment control panel;

b.        An interlock system shall be provided to ensure that the equipment can emit only the energy of radiation that is selected;

c.         An interlock system shall be provided to prevent irradiation if any selected operations carried out in the treatment room do not agree with the selected operations indicated at the treatment control panel; and

d.        The energy selected shall be displayed at the treat- ment control panel before and during irradiation.

8.        Selection of stationary or moving beam therapy. Equip- ment capable of both stationary and moving beam ther- apy modes shall meet all of the following requirements:

a.         Irradiation shall not be possible until a selection of stationary beam therapy or moving beam therapy is made at the treatment control panel;

b.        An interlock system shall be provided to ensure that the equipment can operate only in the mode that is selected;

c.         An interlock system shall be provided to prevent irradiation if any selected operations carried out in the treatment room do not agree with the selected operations indicated at the treatment control panel;

d.        An interlock system shall be provided to terminate irradiation if the movement stops during moving beam therapy;

e.         Moving beam therapy shall be so controlled that the required relationship between the number of dose monitor units and movement is obtained; and

f.         The mode of operation shall be displayed at the treatment control panel.

9.        Focal spot location and beam orientation. The registrant shall determine, or obtain from the manufacturer, the location in reference to an accessible point on the radia- tion head of all of the following:

a.         The x-ray target or the virtual source of x-rays,

b.        The electron window or the scattering foil, and

c.         All possible orientations of the useful beam.

10.     System checking facilities. Capabilities shall be provided for checking of all safety interlock systems.

B.       Facility and shielding requirements.

1.        In addition to protective barriers sufficient to ensure com- pliance with R12-1-907, all of the following design requirements apply:

a.         Except for entrance doors or beam interceptors, all the required barriers shall be fixed barriers;

b.        The treatment control panel shall be located outside the treatment room;

c.         Windows, mirrors, operable closed-circuit televi- sion, or other equivalent viewing systems shall be provided to permit continuous observation of the patient during irradiation and shall be so located that the operator may observe the patient from the treat- ment control panel;

d.        Provision shall be made for two-way oral communi- cation between the patient and the operator at the treatment control panel;

e.         Each point of entry into the treatment room shall be provided with warning lights that will indicate when the useful beam is “on” in a readily observable posi- tion outside of the room; and

f.         Interlocks shall be provided and shall result in all entrance doors being closed before treatment can be initiated or continued. If the radiation beam is inter- rupted by any door opening, it shall be possible to restore the machine to operation only by closing the door and reinitiating exposure by manual action at the control panel.

2.        An authorized medical physicist, trained and experienced in the principles of radiation protection, shall perform a radiation protection survey on all installations before human use and after any change in an installation that might produce a radiation hazard. The authorized medical physicist shall provide the survey results in writing to the individual in charge of the installation and transmit a copy of the survey results to the Agency.

3.        Calibrations.

a.         Calibration of the therapy system, including radia- tion output calibration, shall be performed before placing new installations into operation for the pur- pose of irradiation of patients. Subsequent calibra- tions shall be made at intervals not to exceed 12 months, and after any change that may cause the cal- ibration of the therapy system to change.

b.        Calibration of the radiation output of the therapy beam shall be performed with an instrument that has been calibrated using a method that is traceable to the National Institute of Standards and Technology (NIST), within the preceding two years.

c.         Calibration of a particle accelerator shall be per- formed by, or under the supervision of an authorized medical physicist who meets the qualification requirements specified in R12-1-711, and a copy of the calibration report shall be maintained by the reg- istrant for inspection by the Agency.

d.        Calibration of the therapy beam shall include, but not necessarily be limited to, all of the following determinations:

i.         Verification that the equipment is operating within the design specifications concerning the light localizer, the side light and back pointer alignment with the isocenter, when applicable, variation in the axis of rotation for the table, gantry and jaw system, and beam flatness and symmetry at specific depths;

ii.        The exposure rate or dose rate in air or at vari- ous depths of water for the range of field sizes used for each effective energy, and for each treatment distance used for radiation therapy;

iii.      The congruence between the radiation field and the field defined by the localizing device;

iv.       The uniformity of the radiation field and its dependency upon the direction of the useful beam; and

v.        The calibration determinations above shall be provided in sufficient detail, to allow the absorbed dose to tissue in the useful beam to be calculated to within plus or minus 5 percent.

e.         Records of calibrations shall be maintained for three years following the date the calibration was per- formed.

f.         A copy of the current calibration report shall be available in the therapy facility for use by the opera- tor, and the report shall contain the following infor- mation:

i.         The action taken by the authorized medical physicist performing the calibration if it indi- cates a change has occurred since the last cali- bration,

ii.        A listing of the persons informed of the change in calibration results, and

iii.      A statement as to the effect the change in cali- bration has had on the therapy doses prior to the current calibration finding.

C.      Spot checks.

1.        The spot check procedures shall be in writing and shall have been developed by an authorized medical physicist trained and experienced in performing calibrations.

2.        The measurements taken during spot checks shall demon- strate the degree of consistency of the operating charac- teristics which can affect the radiation output of the system or the radiation dose delivered to a patient during a therapy procedure.

3.        The written spot check procedure shall indicate the fre- quency at which tests or measurements are to be per- formed, not to exceed monthly.

4.        The spot check procedure shall note conditions that require recalibration of the therapy system before further human irradiation.

5.        Records of spot checks shall be maintained and available for inspection by the Agency for three years following the spot check measurements. Records of spot checks not performed by an authorized medical physicist shall be signed by an authorized medical physicist within 15 days of the spot check.

D.      Operating procedures.

1.        Only the patient shall be in the treatment room during irradiation.

2.        If a patient must be held in position during treatment only, mechanical supporting or restraining devices shall be used for this purpose.

Historical Note

Adopted effective June 30, 1977 (Supp. 77-3). Repealed

effective August 8, 1986 (Supp. 86-4). New Section made by final rulemaking at 7 A.A.R. 2584, effective June 8, 2001 (Supp. 01-2). Amended by final rulemaking at 9

A.A.R. 4302, effective November 14, 2003 (Supp. 03-3). Amended by final rulemaking at 10 A.A.R. 4458, effec- tive December 4, 2004 (Supp. 04-4). Amended by final rulemaking at 15 A.A.R. 1023, effective August 1, 2009

(Supp. 09-2).