| (II) The indicated technique factors shall be accurate
to within manufacturer's specifications. If these specifications are
not available from the manufacturer, the factors shall be accurate
to within ±10% of the indicated setting.
(iii) Beam limitation.
(I) The beam limiting device (collimator) shall restrict
the useful beam to the area of clinical interest.
(II) A method shall be provided to visually define
the center (cross-hair centering) of the x-ray field to within a 2
mm diameter.
(III) A method shall be provided to accurately indicate
the distance to within 2 mm.
(IV) The delineator wires shall be accurate with the
indicated setting within 2 mm.
(V) The x-ray field shall be congruent with the light
field within 2 mm.
(iv) Timers. Means shall be provided to terminate the
exposure at a preset time interval, a preset product of current and
time, a preset number of pulses, or a preset radiation exposure to
the image receptor. In addition, it shall not be possible to make
an exposure when the timer is set to a "zero" or "off" position if
either position is provided and a visual and/or audible signal shall
indicate when an exposure has been terminated.
(v) AEC. When an AEC is provided, an indication shall
be made on the control panel when this mode of operation is selected.
(vi) Timer reproducibility. When all technique factors
are held constant, including control panel selections associated with
AEC systems, the coefficient of variation of exposure interval for
both manual and AEC systems shall not exceed 0.05. This requirement
applies to clinically used techniques.
(vii) Exposure reproducibility. When all technique
factors are held constant, including control panel selections associated
with AEC systems, the coefficient of variation of exposure for both
manual and AEC systems shall not exceed 0.05. This requirement applies
to clinically used techniques.
(viii) Linearity.
Attached Graphic
(C) Additional requirements for radiation therapy simulators
utilizing fluoroscopic capabilities.
(i) X-ray production in the fluoroscopic mode shall
be controlled by a device that requires continuous pressure by the
fluoroscopist for the entire time of the exposure (continuous pressure
type switch).
(ii) During fluoroscopy and cinefluorography, the kV
and the mA shall be continuously indicated at the control panel and/or
the fluoroscopist's position.
(iii) The SSD shall not be less than the 20 cm for
image-intensified fluoroscopes used for examinations as specified
in the registrant's operating and safety procedures. The written operating
and safety procedures shall provide precautionary measures to be adhered
to during the use of this device. The procedures shall provide information
on the means to restore the unit to a 30 cm SSD when the unit is returned
to general service.
(iv) Fluoroscopic timers shall meet the following requirements.
(I) Means shall be provided to preset the cumulative
on-time of the fluoroscopic x-ray tube. The maximum cumulative time
of the timing device shall not exceed 5 minutes without resetting.
(II) A signal audible to the fluoroscopist shall indicate
the completion of any preset cumulative on-time. Such signal shall
continue to sound while x-rays are produced until the timing device
is reset. In lieu of such signal, the timer shall terminate the beam
after the preset cumulative on-time is completed.
(v) The exposure foot switch shall be permanently mounted
in the control booth to ensure that the operator cannot enter the
simulator room while the fluoroscope is activated.
(vi) Simulators shall duplicate the geometric conditions
of the radiation therapy equipment plan and therefore measurements
regarding geometric conditions shall be performed in accordance with
subsection (h)(3)(C)(iii)(I) of this section.
(vii) If the treatment-planning system is different
from the treatment-delivery system, the accuracy of electronic transfer
of the treatment-delivery parameters to the treatment-delivery unit
shall be verified at the treatment location.
(D) Additional requirements for radiation therapy simulators
utilizing CT capabilities. CT simulators producing digital images
only are exempt from the requirements of this subparagraph and paragraph
(h)(4)(A)(i), (viii), and (ix) of this subsection.
(i) Equipment requirements.
(I) Tomographic systems shall meet the following requirements.
(-a-) For any single tomogram system, means shall be
provided to permit visual determination of the tomographic plane or
a reference plane offset from the tomographic plane.
(-b-) For any multiple tomogram system, means shall
be provided to permit visual determination of the tomographic plane
or a reference plane offset from the tomographic plane.
(-c-) If a device using a light source is used to satisfy
the requirements of item (-a-) or (-b-) of this subclause, the light
source shall provide illumination levels sufficient to permit visual
determination of the location of the tomographic plane or reference
plane under ambient light conditions of up to 500 lux.
(II) The CT x-ray system shall be designed such that
the CT conditions of operation to be used during a scan or a scan
sequence are indicated prior to the initiation of a scan or a scan
sequence. On equipment having all or some of these conditions of operation
at fixed values, this requirement may be met by permanent markings.
Indication of CT conditions shall be visible from any position from
which scan initiation is possible.
(III) The x-ray control and gantry shall provide visual
indication whenever x rays are produced and, if applicable, whether
the shutter is open or closed.
(IV) Means shall be provided to require operator initiation
of each individual scan or series of scans.
(V) All emergency buttons/switches shall be clearly
labeled as to their functions.
(VI) Termination of exposure shall be as follows.
(-a-) Means shall be provided to terminate the x-ray
exposure automatically by either de-energizing the x-ray source or
shuttering the x-ray beam in the event of equipment failure affecting
data collection. Such termination shall occur within an interval that
limits the total scan time to no more than 110% of its preset value
through the use of either a backup timer or devices that monitor equipment
function.
(-b-) A signal visible to the operator shall indicate
when the x-ray exposure has been terminated through the means required
by item (-a-) of this subclause.
(-c-) The operator shall be able to terminate the x-ray
exposure at any time during a scan or series of scans under CT x-ray
system control, of greater than 0.5 second duration. Termination of
the x-ray exposure shall necessitate resetting of the CT conditions
of operation prior to initiation of another scan.
(VII) CT x-ray systems containing a gantry manufactured
after September 3, 1985, shall meet the following requirements.
(-a-) The total error in the indicated location of
the tomographic plane or reference plane shall not exceed 5 mm.
(-b-) If the x-ray production period is less than 0.5
second, the indication of x-ray production shall be actuated for at
least 0.5 second. Indicators at or near the gantry shall be discernible
from any point external to the patient opening where insertion of
any part of the human body into the primary beam is possible.
(-c-) The deviation of indicated scan increment versus
actual increment shall not exceed ±1 mm with any mass from
0 to 100 kilograms (kg) resting on the support device. The patient
support device shall be incremented from a typical starting position
to the maximum incremented distance or 30 cm, whichever is less, and
then returned to the starting position. Measurement of actual versus
indicated scan increment can be taken anywhere along this travel.
(ii) Facility design requirements.
(I) Provision shall be made for two-way aural communication
between the patient and the operator at the control panel.
(II) Windows, mirrors, closed-circuit television, or
an equivalent shall be provided to permit continuous observation of
the patient during irradiation and shall be so located that the operator
can observe the patient from the console.
(-a-) Should the viewing system described in subclause
(II) of this clause fail or be inoperative, treatment shall not be
performed with the unit until the system is restored.
(-b-) In a facility that has a primary viewing system
by electronic means and an alternate viewing system, should both viewing
systems described in subclause (II) of this clause fail or be inoperative,
treatment shall not be performed with the unit until 1 of the systems
is restored.
Cont'd... |
