Washington Administrative Code › Title 246 - Health, Department of › RADIATION › Chapter 246-225 - Radiation protection - X rays in the healing arts › Section 246-225-130 - X-ray and electron therapy systems with energies of one MeV and above

Current through Register Vol. 24-14, July 15, 2024
Chapter 246-229 WAC except WAC 246-229-100(3) and (4) shall
				  apply to medical facilities using therapy systems with energies 1 MeV and
				  above.
(1)
Definitions.
In addition to the definitions provided in WAC
				246-225-010, the following
				definitions shall be applicable to this section.
(a) "Applicator" means a structure which
				indicates the extent of the treatment field at a given distance from the
				nominal source and which may or may not incorporate an additional beam-limiting
				device.
(b) "Beam scattering foil"
				means a device which scatters and flattens a beam of electrons.
(c) "Central axis of the beam" means a line
				passing through the origin of the source and the center of the plane figure
				formed by the edge of the secondary collimating jaws when in a symmetric
				mode.
(d) "Dose monitoring system"
				means a system of devices for the detection and display of quantities of
				radiation.
(e) "Dose monitor unit"
				means a unit from which the absorbed dose can be calculated.
(f) "Existing equipment" means therapy
				systems subject to this section which were manufactured on or before the
				effective date of these regulations.
(g) "Field flattening device" means an
				absorber used to homogenize the dose rate over the area of a useful beam of
				X-rays.
(h) "Field size" means the
				dimensions of an area in a plane perpendicular to the specified direction of
				the beam of incident radiation at a maximum dose depth. Determine dimensions by
				fifty percent decrement lines.
(i)
				"Gantry" means that part of the system supporting and allowing possible
				movements of the radiation head.
(j) "Interruption of irradiation" means the
				stopping of irradiation with the possibility of continuing irradiation without
				resetting of the operating conditions at the control panel.
(k) "Isocenter" means a fixed point in space
				located at the intersection of the rotation axes of the principal movements of
				the therapy system.
(l) "Moving
				beam therapy" means radiation therapy with relative displacement of the useful
				beam and the patient during irradiation.
(m) "New equipment" means systems subject to
				this section which were manufactured after effective date of these
				regulations.
(n) "Nominal source"
				means a point from which radiation originates.
(o) "Normal treatment distance" means the
				distance between the virtual source and a reference point on the central axis
				of the beam. The reference is located at a position on the central axis at a
				specified distance from the nominal source.
(p) "Patient" means an individual subjected
				to examination and treatment.
(q)
				"Phantom" means a volume of material behaving in a manner similar to tissue
				with respect to the attenuation and scattering of radiation.
(r) "Primary dose monitoring system" means a
				system which will monitor the quantity of radiation produced during irradiation
				and which will terminate irradiation when a preselected number of dose monitor
				units have been acquired.
(s)
				"Radiation treatment prescription" means the absorbed dose which is intended to
				be delivered to the treatment volume.
(t) "Radiation head" means the structure from
				which the useful beam emerges.
(u)
				"Redundant dose monitoring combination" means a combination of two dose
				monitoring systems in which both systems are arranged to terminate irradiation
				in accordance with a preselected number of dose monitor units.
(v) "Secondary dose monitoring system" means
				a system which will terminate irradiation in the event of failure of the
				primary system.
(w) "Shadow tray"
				means a device attached to the radiation head to support auxiliary beam
				limiting material.
(x) "Stationary
				beam therapy" means radiation therapy without relative displacement of the
				useful beam and the patient during irradiation.
(y) "Target" means that part of a radiation
				source which intercepts a beam of accelerated particles with subsequent
				emission of other radiation.
(z)
				"Termination of irradiation" means the stopping of irradiation in a fashion
				which will not permit continuance of irradiation without the resetting of
				operating conditions at the control panel.
(aa) "Treatment field" means the
				cross-sectional area of the patient's tissue which is to be
				irradiated.
(bb) "Treatment volume"
				means that portion of the patient's body which is to be irradiated.