A. A
registrant shall prevent leakage radiation from the diagnostic source assembly
measured at a distance of 1 meter in any direction from the source assembly
from exceeding 25.8 µC/ kg (100 milliroentgens) in one hour when the
x-ray tube is operated at its leakage technique factors. The Department shall
determine compliance by obtaining measurements averaged over an area of 100
square centimeters (15.5 square inches) with no linear dimension greater than
20 centimeters (7.9 inches).
B. The
registrant shall prevent radiation emitted by a component other than the
diagnostic source assembly from exceeding 516 nC/kg (2 milliroentgens) in one
hour at 5 centimeters from any accessible surface of the component when it is
operated in an assembled x-ray system under any conditions for which it was
designed. The Department shall determine compliance by obtaining measurements
averaged over an area of 100 square centimeters (15.5 square inches) with no
linear dimension greater than 20 centimeters (7.9 inches).
C. Beam quality.
1. The registrant shall prevent the useful
beam half-value layer (HVL) for diagnostic x-ray given x-ray tube potential
from falling below the values shown in Table I. If it is necessary to determine
the HVL at an x-ray tube potential that is not listed in Table I, the
registrant shall use linear interpolation or extrapolation to make the
determination.
|
Table I
|
|
Design operating range (kilovolts peak)
|
Measured potential (kilovolts peak)
|
HVL (millimeters of aluminum) Dental Intraoral
Units manufactured after December 1, 1980
|
Medical X-ray Units manufactured before June 10,
2006 and Dental Intraoral Units manufactured on or before December 1,
1980
|
Medical X-ray Units manufactured on or after June
10, 2006
|
|
Below 51
|
30
|
1.5
|
0.3
|
0.3
|
|
40
|
1.5
|
0.4
|
0.4
|
|
50
|
1.5
|
0.5
|
0.5
|
|
51 to 70
|
51
|
1.5
|
1.2
|
1.3
|
|
60
|
1.5
|
1.3
|
1.5
|
|
70
|
1.5
|
1.5
|
1.8
|
|
Above 70
|
71
|
2.1
|
2.1
|
2.5
|
|
80
|
2.3
|
2.3
|
2.9
|
|
90
|
2.5
|
2.5
|
3.2
|
|
100
|
2.7
|
2.7
|
3.6
|
|
110
|
3.0
|
3.0
|
3.9
|
|
120
|
3.2
|
3.2
|
4.3
|
|
130
|
3.5
|
3.5
|
4.7
|
|
140
|
3.8
|
3.8
|
5.0
|
|
150
|
4.1
|
4.1
|
5.4
|
2.
If the registrant demonstrates that the aluminum equivalent of the total
filtration in the primary beam is not less than that shown in Table II, the
registrant is considered to have met the criteria in subsection (C)(1).
Table II - Filtration Required vs. Operating
Voltage
|
Operating Voltage (kVp)
|
Total Filtration (inherent plus added)
(millimeters aluminum equivalent)
|
|
Below 51
|
0.5 millimeters
|
|
51 - 70
|
1.5 millimeters
|
|
Above 70
|
2.5 millimeters
|
3.
The registrant shall use beryllium window tubes that have a minimum of 0.5
millimeters aluminum equivalent filtration permanently mounted in the useful
beam.
4. For capacitor energy
storage equipment, the Department shall determine compliance with the maximum
quantity of charge per exposure.
5.
When determining the minimum aluminum equivalent filtration, the registrant
shall include the filtration contributed by all materials that are always
present between the focal spot of the tube and the patient (for example, a
tabletop when the tube is mounted "under the table" and inherent filtration of
the tube).
D. Multiple
tubes. If two or more radiographic tubes are controlled by one exposure switch,
the operator shall clearly indicate which tube or tubes have been selected
before initiation of the exposure, activating one light on the x-ray control
panel and a second light at or near the tube housing assembly each indicating
the tube or tubes that have been selected.
E. Mechanical support of tube head. The
registrant shall adjust the tube housing assembly supports so that the tube
housing assembly will remain stable during an exposure, unless the tube housing
movement is a designed function of the x-ray system.
F. Exposure reproducibility. The coefficient
of variation shall not exceed 0.10 when all technique factors are held
constant. This requirement is satisfied if the value of the average exposure
(E) is greater than or equal to five times the difference between the maximum
exposure (Emax) and minimum exposure (Emin) when four exposures are made at
identical technique factors, [E=>5(Emax - Emin)].
G. Accuracy deviation. A registrant shall not
use an x-ray machine if the measured technique factors for kVp and time
duration are not within the limits specified by the manufacturer In the absence
of the manufacturer's specifications, a registrant shall not use an x-ray
machine if the measured kVp is not within 10 percent of the indicated kVp value
and the measured time duration is not within 20 percent of the indicated
time.
