Numerical comparison of attenuation and hardening properties
of phantom (lucite, soft tissue, water) and hardware (aluminium and steel)
materials with those of lead has been carried out. Results show that the
shieldings that are affordable by lead attenuation equivalent thicknesses (LAE)
and lead hardening equivalent thicknesses (LHE) are not strictly equivalent to
those affordable by thickness of substitutes (phantom materials, aluminium and
steel) when there are differences in attenuation and hardening properties. Even
though beams through LAE that are not ‘exact’ have equal exposure values, the
half value layers are higher than those through thickness of lead substitutes.
Example calculations show that the use of lead thickness (LAE) that are not
‘exact’ to account for the shielding afforded by the thickness of patient
(water phantom) produce lesser reduction of primary radiation level in the area
marked for shielding. The ‘exact’ LAE that will reduce primary radiation level
equally as the patient and radiographic table may be higher by close to 20 % or
more of that which is not ‘exact’.
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