Dosage tables for Röntgen therapy / by Friedrich Voltz ; translated from the second German edition.

  • Voltz, Friedrich, 1891-1938.
Date:
1928
Catalogue details

Licence: In copyright

Credit: Dosage tables for Röntgen therapy / by Friedrich Voltz ; translated from the second German edition. Source: Wellcome Collection.

    34/136 (page 22)
    does not depend upon the size of the incidence-field alone, but also upon the distance of the focus from the surface. The practical dose, or P.D., may be defined as that dose which is delivered when the depth, field of incidence, focal distance, and quality of radiation are all optional. It is the effective physical dose. The practical dose, P.D., like the percentage deep dose, P.D.D., or the effective dose, E.D., is expressed as a p)er- centage of the quantity of radiation present at the surface at the given focal distance: P.D. .(i6) If Dq = ioo%, the P.D. will be x% of Dg. WTien the focal distance from the surface is 23 cm. and the depth is 10 cm., the practical dose, P.D., and the effective dose, E.D., are the same. When the focal distance from the surface is 23 cm. and the field of incidence is 6 x 8 cm., the practical dose, P.D., at a depth of 10 cm. is the same as the percentage deep dose, P.D.D. The size of the practical dose, P.D., is determined by the same three factors as the dosage quotient: i. spreading, ii. absorption, iii. scattering. (i) The practical dose, P.D., given a constant overlying stratum and a constant quality of radiations, will be larger and, hence, better the greater the distance of the source of the rays from the absorbent body, for the difference between their density at the surface and at the given depth will be accordingly reduced. (ii) The practical dose, P.D., given a constant overlying stratum and a constant focal distance from the surface, will be larger the less the absorption in the overlj’ing stratum; that is, the greater the penetrating power of the rays. (iii) The practical dose, P.D., given a constant overlying