System information

6) Select positions on the surface of an
imaginary sphere of 1 meter radius with
its-center located at the focal spot.
Include points at a height equal to
the plane including the tube housing
and the collimator junction.
7) Measure the leakage radiation at the
selected positions.
8) Correct any data which could not be
collected at 1 meter,
The average reading over 100 square centimeters at 1
meter should not exceed 100 mR in one hour, normalized to
the maximum current for continuous operation at
the
maximum (or the maximum allowable) tube potential. No
linear dimension of the 100 square cm area should be
greater than 20 cm (Reference #l).
IV-3. In-room Scattered Radiation Measurement
In room stray and
scattered
radiation level
measurements are often necessary for routine fluoroscopic
systems or special procedure
suites. Measurements around
stationary radiographic systems and portable x-ray units
may also be necessary
to assure that the non-radiation
workers are not subjected to
excessive amounts of
radiation.
The technique factor requirements are similar to
those employed in leakage radiation level measurements. A
water, plastic, or pressed wood scattering phantom should
be placed in the primary beam. It should be approximately
30 cm x 30 cm x 25 cm (width x length x thickness) to
simulate an average adult abdomen.
Suitable sizes should
be employed to simulate other parts of the body, eg. 15 cm
x 19 cm x 15 cm for an adult head. Aluminum or Copper are
unacceptable as scattering materials.
The equipment should be arranged to simulate the
clinical situation.
Measurements should be made at the
fluoroscopist's, angiographer's, radiographer's, and other
ancillary personnel's locations.
(Reference #16). The actual thickness of shielding
To assess the total
scattered radiation delivered to each point of interest,
the measured exposures should
be scaled to a weekly
exposure using appropriate workload information.
IV-4. Protective Barrier/Shielding Assessment
Shielding provided by room barriers must be adequate
to reduce radiation levels to personnel, patients, and the
general public to meet the guidelines established by NCRP
Report No. 39, "Basic Radiation Protection Criteria"
required is a function of the following:
(a) Type of material in the barrier,
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