Current through Register Vol. 54, No. 44, November 2, 2024
(a) When
the tube is operated at its leakage technique factors, the leakage radiation
may not exceed:
(1) One hundred milliroentgens
(25.8µC/kg) per hour at 5 centimeters from the surface of the tube
housing assembly for contact therapy systems.
(2) One roentgen (.258 mC/kg) per hour at 1
meter from the source for 0-150 kVp systems manufactured or installed prior to
December 19, 1987.
(3) One hundred
milliroentgens (25.8µC/kg) per hour at 1 meter from the source for 0-150
kVp systems manufactured on or after December 19, 1987.
(4) One roentgen (.258 mC/kg) per hour at 1
meter from the source for 151 to 500 kVp systems.
(5) One-tenth percent of the exposure rate of
the useful beam 1 meter from the source for 501 to 999 kVp systems at 1 meter
from the source.
(b)
Fixed diaphragms or cones used for limiting the useful beam must provide at
least the same protection as required by the tube housing assembly.
(c) Beam limiting devices may, for the
portion of the useful beam blocked by these devices, transmit not more than 5%
of the original X-ray beam intensity at the maximum voltage and maximum
treatment filter. This requirement does not apply to auxiliary blocks or
materials placed in the useful beam to shape the useful beam to the individual
patient.
(d) The filter system
shall be designed so that:
(1) Filters cannot
be accidentally displaced from the useful beam at any possible tube
orientation.
(2) The radiation at 5
centimeters from the filter insertion slot opening does not exceed 30 roentgens
(7.74 mC/kg) per hour under operating conditions.
(3) A filter is marked as to its material of
construction and its thickness. For wedge filters, the wedge factor and wedge
angle shall appear on the wedge or wedge tray.
(4) On equipment purchased after January 1,
1971, a filter indication system shall be used on therapy machines using
changeable filters. The system must indicate from the control panel the
presence or absence of a filter and be designed to permit easy recognition of
an added filter in place.
(5) An
X-ray system equipped with a beryllium or other low-filtration window shall be
clearly labeled as such upon the tube housing assembly and at the control
panel.
(e) The tube
housing assembly shall be immobilized during stationary treatments.
(f) The tube housing assembly shall be so
marked that it is possible to determine the location of the focal spot to
within 5 millimeters, and the marking shall be readily accessible for use
during calibration procedures.
(g)
Contact therapy tube housing assemblies shall have a removable shield of at
least .5 millimeter lead equivalency at 100 kVp that can be positioned over the
entire useful beam exit port during periods when the beam is not in
use.
(h) Systems of greater than
150 kVp manufactured after December 19, 1987, must have a beam monitor system
which meets the following requirements:
(1)
Not allow irradiation until a preselected value of exposure has been made at
the treatment control panel.
(2)
Independently terminate irradiation when the preselected exposure has been
reached.
(3) Be designed so that,
in the event of a system malfunction or electrical power failure or other
interruption, the dose administered to a patient prior to the interruption can
be accurately determined.
(4) Have
a control panel display which maintains the reading until intentionally reset
to zero.
(5) Have a control panel
display which does not have scale multiplying factors and utilizes a design so
that increasing dose is displayed by increasing numbers.
(i) The following apply to timers on the
equipment:
(1) A timer shall be provided which
has a display at the control panel. The timer must be graduated in minutes and
fractions of minutes. The timer must have a preset time selector and an elapsed
time indicator.
(2) The timer must
be a cumulative timer which activates with the radiation and retains its
reading after irradiation is interrupted or terminated. After irradiation is
terminated and before irradiation can be reinitiated, it shall be necessary to
reset the timer to zero.
(3) The
timer must terminate irradiation when a preselected time has elapsed if a dose
monitoring system present has not previously terminated irradiation.
(4) The timer must permit accurate presetting
and determination of exposure time as short as 1 second.
(5) The timer may not permit an exposure if
set at zero.
(6) The timer may not
activate until the shutter is opened when patient irradiation is controlled by
a shutter mechanism.
(j)
The control panel, in addition to the displays required in this section, must
have:
(1) An indication of power
status.
(2) An indication of X-ray
production.
(3) The means of
indicating X-ray tube current and voltage.
(4) The means of terminating an
exposure.
(k) When a
control panel may energize more than one X-ray tube, the following requirements
shall be met:
(1) It must be possible to
activate only one X-ray tube at one time.
(2) There must be an indication at the
control panel identifying which X-ray tube is energized.
(3) There must be an indication at the tube
housing assembly when that tube is energized.
(l) There must be a means of determining the
SSD to within 5 millimeters.
(m)
Unless it is possible to bring the X-ray output to the prescribed exposure
parameters within 5 seconds, the entire useful beam shall be automatically
attenuated by a shutter having a lead equivalency not less than that of the
tube housing assembly.
(1) After the unit is
at operating parameters, the shutter shall be controlled electrically by the
operator from the control panel.
(2) An indication of shutter position must
appear at the control panel.
(n) Electronic brachytherapy devices are
exempt from the requirements in subsections (k)-(m).
The provisions of this §221.71 issued and amended under
sections 301 and 302 of the Radiation Protection Act (35 P.S.
§§
7110.301 and
7110.302); and section 1920-A
of The Administrative Code of 1929 (71 P.S. §
510-20); and the Radon Certification Act
(63
P.S. §§ 2001-2014).
This section cited in 25 Pa. Code §
216.1 (relating to purpose and
scope); and 25 Pa. Code §
216.3 (relating to
exemptions).
