Skin Dose from Tc-99m -Reply

[Roger Fenner <rfenner@mail.state.tn.us>]

The Health Physics and Radiological  Health Handbook has two sets of
values for Dose Conversion Factors for Selected Radionuclides on Skin -
Table 13.12.2:

     0.0030 Sv/y per Bq/cm sq. @ a depth of 3-5 mg/cm sq. and 0.0021
Sv/y per Bq/cm sq. @ a depth of 5-10 mg/cm sq. - WITH AIR
REFLECTION, and;

     0.0023 Sv/y per Bq/cm sq. @ a depth of 3-5 mg/cm sq. and 0.0017
Sv/y per Bq/cm sq. @ a depth of 5-10 mg/cm sq. - WITHOUT AIR
REFLECTION. 

     A footnote says that: Upper (i.e. with air reflection) and lower (i.e.
without air reflection) bounds for normalized doses are given for three of
depth in skin. The upper bound corresponds to an inclusion for
atmospheric reflection of electrons to the skin.  The factors 422.1 and
197.8 convert to units to rad/h per uCi/cm sq. and MeV/gs per Bq/cm sq.,
respectivly.  The dose factor reflects initial dose rate and does not
account for radioactive decay.  The dose factor is averaged over the
indicated depth.

For Tc-99m there were no values for depths of 30-50 mg/cm sq. so I
didn't indicate them.