. Journal of radiology . The results have beenpublished in the Dessauer charts. Thesecharts consider all possibilities such asdifferent focal skin distances, differentsizes of the fields, and different hard-nesses. If both geometrical facts aregiven, for example 50 cm. focal skindistance, 20 cm. port of entry, thehardness has to be known also, eitheras the total absorption coefficient y,,or as the deep quotient. Then we knowwhat charts have to be used. Knowl-edge of the kilovoltage is not sufficient,as I have demonstrated before. In Ger-many the kilovoltage is measured verydifferently, therefo
. Journal of radiology . The results have beenpublished in the Dessauer charts. Thesecharts consider all possibilities such asdifferent focal skin distances, differentsizes of the fields, and different hard-nesses. If both geometrical facts aregiven, for example 50 cm. focal skindistance, 20 cm. port of entry, thehardness has to be known also, eitheras the total absorption coefficient y,,or as the deep quotient. Then we knowwhat charts have to be used. Knowl-edge of the kilovoltage is not sufficient,as I have demonstrated before. In Ger-many the kilovoltage is measured verydifferently, therefore quite great dif-ferences arise. The best way is eitherto measure the deep quotient by acorrect iontoquantimeter under wellknown conditions and to select the Des-sauer charts with these values, or tomeasure the \x by an electroscope. Using the Dessauer charts we areable to find the distribution in the depth,even if we combine three or four fieldsfor every desired point in the interiorand on the surface. Some examples. 480 THE PRACTICAL DOSAGE OF X-RAYS—BACH EM may show you the results of differentmethods of treatment (Figs. 8-11). By such figures and by special in-vestigations we can find what are thebest and most economic conditions forpractical treatment and what amountof radiation in each case is sent to eachpoint. The last method, to define andto find the necessary three factors, andthen to use the given exact measure- ments may be called the indirectmethod. You see, gentlemen, how it is pos-sible today to give a correct I have explained to you in thisshort paper is not a certain method thatI would like to recommend to you—it is very indifferent which method youuse. The chief factors are- to give anexact physical skin dose, a dose which always remains the same, or which isalways known, and to know the in-tensity, which is given at importantpoints in the depth. Only when thephysical dosage is given correctly inthis manner is the comparison with thebiologica
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