RADIOAUTOGRAPHY 



300 



RADIOAUTOGRAPHY 



This method has been used extensively 

 especially in hospitals where a minimum 

 of equipment was desirable. The 

 method, however, does not always give 

 reproducible results because of 1) un- 

 even penetration of developer through 

 the tissue leaving some areas with latent 

 images in the emulsion beneath un- 

 developed, 2) staining of the emulsion 

 gelatin which obscures histological and 

 radioautographic detail to some extent, 

 and 3) chemical action of the tissue 

 on the emulsion causing in some cases 

 blackening of the emulsion or in other 

 cases insensitization of the emulsion. 

 These possibilities are eliminated in 

 the "coating" methods. It must be 

 emphasized, however, that the prepara- 

 tions obtained by the mounting tech- 

 nique are often more satisfactory under 

 high than under low magnification. 



Several "Dry" Mounting methods 

 have been described (Hoecker, F. E. 

 and Roofe, P. G., Radiology, 1949, 52, 

 856-865; Williams, A. I., Oak Ridge, 

 Tenn., Los Alamos Scientific Labora- 

 tory, AECU, 1950, 930; Gallimore, J., 

 Oak Ridge, Tenn., 1951). These elim- 

 inate the use of large quantities of 

 water on the tissue prior to exposure, 

 thus preventing loss or displacement of 

 water soluble material. The published 

 results indicate that the method is still 

 in the experimental stage. 



3. Coating method: A slide bearing a 

 histological tissue section is covered 

 with either a fluid emulsion or a strip- 

 ping emulsion removed from its backing. 

 The method as used with fluid emulsion 

 is very satisfactory for research pur- 

 poses, because of the possibility of con- 

 trolling the thickness of the emulsion. 

 In "fluid coating": 



1. The sections, stained or unstained, 

 are coated with celloidin as in the 

 contact method. The area on the 

 slide to be coated is outlined with a 

 diamond pencil. 



2. Using a Wratten No. 1 safelight at 

 a distance of three feet, photographic 

 emulsion is prepared for coating, 

 a) The most convenient emulsions 



with which to work are the bulk 

 emulsions, several of which have 

 been kindly given the authors by 

 Ansco Corporation and British 

 Kodak Limited. These emul- 

 sions are scooped directly into 

 a 50 cc. beaker which is placed in 

 a 37°C. water bath. Ansco 

 Radioautographic Emulsion A 

 has a large grain size and a very 

 high sensitivity but gives a poor 

 resolution, while British Kodak 

 NT4 bulk emulsion has a small 

 grain size and medium to high 



sensitivity but gives a good 

 resolution. Unfortunately, none 

 of the bulk emulsions is available 

 on a commercial bais. 



b) The next best possibility is to 

 remove emulsion from photo- 

 graphic plates or films such as 

 Eastman Kodak NH Special 

 Spectroscopic plates or Eastman 

 Kodak "Special" Medium Lan- 

 tern Slide films. Both these 

 emulsions have a medium grain 

 size and sensitivity. The emul- 

 sion is hydrated in distilled water 

 (18-20°C.) for 10 minutes and 

 scraped with a clean edged object 

 (such as a glass slide) into the 

 50 cc. beaker. 



c) "Stripping" emulsions, such as 

 Ilford Special Half Tone Strip- 

 ping Plate, that can be stripped 

 away from a glass or film support 

 have also been used successfully. 

 These may be stripped, hydrated, 

 and melted, or may be treated as 

 above. 



d) Another form in which emulsion 

 is available is the "pellicle" which 

 consists of a fairly thick (250/x) 

 layer of concentrated silver bro- 

 mide grains in a matrix of low 

 gelatin content. Although these 

 pellicles have no support, they 

 must be presoaked in distilled 

 water and dupanol C solution 

 (10 cc of water and 10 cc of 1% 

 dupanol per 1" x 3" pellicle) for 

 24 hours at 18°C. The beaker 

 containing the solution and the 

 hydrated pellicle is then trans- 

 ferred to a 37°C. water bath. 

 Eastman Kodak NTB2 and NTBj 

 pellicles have a small grain size 

 and high sensitivity to /3 radia- 

 tions, NTBs being the more 

 sensitive of the two. 



All these emulsions are ready to be 

 applied after 15 minutes in the water 

 bath. 



To further improve resolution, these 

 emulsions may be diluted with distilled 

 water and dupanol (Gross et al., re- 

 ferred to above). 



3. Using a medicine dropper, two drops 

 of melted emulsion are applied per 

 square inch of slide to be coated. 

 These are spread quickly and evenly 

 with a camel's hair brush (kept at 

 37°C.) over the outlined area and 

 the emulsion is allowed to gel and 

 dry completely on a leveling table 

 at room temperature. 



4. The dry preparations are stored 

 horizontally in light-tight slide boxes 

 (plastic are recommended) which 

 are kept at refrigerated temperatures 



