Half-value layer or HVL definition
Half-value layer or HVL means the thickness of specified material which attenuates the beam of radiation to an extent that the EXPOSURE rate is reduced to one-half of its original value. In this definition, the contribution of scatter radiation, other than that which might be present initially in the beam concerned, is deemed to be excluded.
Half-value layer or HVL means the thickness of specified fourth of the maximum in the intersection. material which attenuates the beam of radiation to an extent that the "mA" means tube current in milliamperes.