Fluke Biomedical 76-414 - Manual (Page 12)

Nuclear Associates 76-414-4150
Operators Manual
2-6
more than 110 percent of its preset value through the use of either a backup timer or devices which
monitor equipment function. A visible signal shall indicate when the x-ray exposure has been
terminated through these means and manual resetting of the CT conditions of operation shall be
required prior to the initiation of another scan.
(ii) Means shall be provided so that the operator can terminate the x-ray exposure at any time
during a scan, or series of scans under x-ray system control, of greater than one-half second
duration. Termination of the x-ray exposure shall necessitate resetting of the CT conditions of
operation prior to the initiation of another scan.
G. Tomographic Plane Indication and Alignment
1) 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.
2) For any multiple tomogram system, means shall be provided to permit visual determination of the
location of a reference plane. The relationship of the reference plane to the planes of the
tomograms shall be provided to the user in addition to other information provided according to
§1020.30(h). This reference plane can be offset from the location of the tomographic planes.
3) The distance between the indicated location of the tomographic plane or reference plane and its
actual location may not exceed 5 millimeters.
4) For any offset alignment system, the manufacturer shall provide specific instructions with respect to
the use of this system for patient positioning, in addition to other information provided according to
§1020.30(h).
5) If a mechanism using a light source is used to satisfy the requirements of paragraphs (g) (1) and (2)
of this section, the light source shall allow visual determination of the location of the tomographic
plane or reference plane under ambient light conditions of up to 500 lux.
H. Beam-On and Shutter Status Indicators
1) Means shall be provided on the control and on or near the housing of the scanning mechanism to
provide visual indication when and only when x rays are produced and, if applicable, whether the
shutter is open or closed. If the x-ray production period is less than one-half second, the indication
of x-ray production shall be actuated for one-half second. Indicators at or near the housing of the
scanning mechanism 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.
2) For systems that allow high voltage to be applied to the x-ray tube continuously and that control the
emission of x rays with a shutter, the radiation emitted may not exceed 100 milliroentgens (2.58 x
10
-5 coulomb/kilogram) in 1 hour at any point 5 centimeters outside the external surface of the
housing of the scanning mechanism when the shutter is closed. Compliance shall be determined by
measurements averaged over an area of 100 square centimeters with no linear dimensions greater
than 20 centimeters.
I. Scan Increment Accuracy
The deviation of indicated scan increment from actual scan increment may not exceed 1 millimeter.
Compliance shall be measured as follows: The determination of the deviation of indicated versus actual
scan increment shall be based on measurements taken with a mass 100 kilograms or less, on the patient
support device. The patient support device shall be incremented from a typical starting position to the
maximum incrementation distance or 30 centimeters, whichever is less, and then returned to the starting
position. Measurement of actual versus indicated scan increment may be taken anywhere along this
travel.