Directional dose equivalent

ICRU sphere

The operational dose quantity directional dose equivalent (H'(d,Ω)) is defined as the equivalent dose at point P at a depth of d mm in the ICRU sphere (see Figure). The corresponding unit is sievert (Sv).

The radiation field in point P of the ICRU sphere is extended, but - contrary to H*(d) - not aligned. The equivalent dose will, therefore, depend on the direction from which the radiation comes. From the definitions, it follows that H*(d) = H'(d,0°).

One distinguishes H'(10,Ω) for penetrating radiation, H'(3,Ω) for the lens of the eye, and H'(0.07,Ω) for the skin.

Directional dose equivalent

Related quantities