Skin Toleration Doses in Roentgen Units and Their Relation to the Quality of Radiation

SINCE the roentgen unit has been adopted as the international unit in roentgen therapy, an earnest endeavor must be made by our Society to induce all roentgenologists of this country to use the unit in their work. Editors of medical journals can do their share in furthering this desirable development by requiring all authors to express data on treatment work in this reproducible unit. A number of problems arise in that connection, problems which have been investigated and discussed before but are far from being solved. Quality of Roentgen Rays Last year, two of us (1) presented before this Society the results of investigations dealing with the comparison of a number of methods to define the quality of roentgen rays. To repeat it once more, quality measurements are necessary because most of our ionization chambers show a dependence on the wave length. While it is also true that transformers with mechanical rectifiers produce different qualities of roentgen rays even if they are running at the same setting as controlled by a kilovolt meter alone, it must be stated that the spectral energy distribution of roentgen-ray beams emitted by different Coolidge tubes running at the same potential as measured by a sphere gap is approximately the same.2 This is particularly true if filtered radiation is used, because then the different thickness is an important factor in superficial therapy with unfiltered radiation has been demonstrated by Wucherpfennig (2). Several years ago, Glocker (3) published ample data showing that potential and filter do determine the quality of roentgen rays if the potential is measured correctly. The agreement in quality among different machines is better in the case of valve tube rectification than in apparatus with mechanical rectifiers. If, therefore, in the paper mentioned before (1), different installations were found to have about the same quality of radiation under identical operating conditions, this is really not so surprising if analyzed properly. It also does not render quality measurements superfluous because it is often simpler to define quality by ionization measurements. That it must be possible practically to produce roentgen-ray beams of the same quality by different apparatus in different localities may be deduced from the paper by Meyer and Glasser (4), who compare, in Table III of their article, the output of seventy machines. In each instance the quality is characterized by the potential, the tube current, and filter only.