RADIUM DOSAGE 83 



is applied slowly, it is to be expected that recuperation will be more 

 effective than when the same amount is applied over a shorter period 

 of time. If the destructive radiation is applied to normal cells and 

 diseased cells alike, and the recuperative process of the normal cell is 

 faster than that of the abnormal cell, then the division of a proposed 

 dose into small doses with sufficient time intervals to allow the normal 

 cells to recuperate completely will make it possible to produce regression 

 of the abnormal cells without marked permanent damage to the normal 

 structure. 



The data available seem to point to the conclusion that normal tissue 

 recuperates faster from exposure to soft x-rays than to hard x-rays and 

 that tissue recuperates definitely with less rapidity from the destructive 

 effects of gamma rays. 



Radium Dosage 



It is highly desirable to have a common unit of dosage in radium and 

 roentgen therapy. Recent attempts to do this have been made by 

 Gray [1936], Mayneord and Roberts [1936], and Failla and Marinelli 

 [1937]. 



To construct a standard gamma-ray ionization chamber somewhat 

 after the specifications laid down by the definition for the roentgen has 

 led to complications. Secondary electrons, due to gamma-ray absorp- 

 tion, have very long paths in air, a fact which makes it necessary to use 

 a large chamber. If the chamber is made large enough for the electron 

 paths other difficulties are introduced that have not been completely 

 solved. 



An indirect method of measuring gamma-ray intensities using small 

 thimble-type ionization chambers, though unsatisfactory, appears to 

 avoid some of the difficulties. The procedure is usually as follows: 

 The small chamber is calibrated in terms of the standard air chamber in 

 roentgens. It is then exposed to gamma radiation, and the calibrated 

 roentgen scale is compared with the ionization produced by the gamma 

 radiation in milligram-hours. The results thus obtained vary more 

 than 13 per cent among seven independent investigations. Failla and 

 Marinelli [1937] who reviewed these results concluded that the ionization 

 dose and the roentgen dose do not bear the same relation to each other 

 when the quality of the radiation varies over any considerable range. 

 Further complications result from the fact that the ionization dose and 

 the roentgen dose do not bear the same relation to each other even in 

 the gamma-ray region, since the roentgen applies to a beam of radiation 

 in which the scattered energy does not contribute to the ionization of 



