Preparation of Radioautographs of Thyroid Tumors for Study at High Magnification

Abstract

One of the methods of studying iodine uptake of thyroid tumors is to make radioautographs of thin sections of the tissue. The usual procedure (1–4) is to place the tissue section, mounted on a microscope slide, against a photographic emulsion for a suitable time in the dark. After the radiation exposure, the two plates are separated. The photographic image is developed, the tissue section is prepared for histologic examination, and the two are compared. In most instances the autographs give clear evidence as to whether the tissue has accumulated radioiodine and, if so, in what general region. The plate containing the autograph may be superimposed on the tissue preparation to permit further localization of the radioiodine. With this method, the exact location of the radioiodine is difficult to determine, as at higher magnifications the alignment of the two preparations becomes arbitrary and the outlines of the denser areas of the autograph are not distinct. It is apparent that closer contact between the tissue and the photographic plate is to be desired; also, that a more objective alignment of the tissue and autograph would be obtained if the two did not have to be separated after the radiation exposure had been made. It occurred to us that, as one of the standard procedures in microtechnic is to float paraffin sections onto the microscope slide, it would be worth while to try such a method of mounting tissue directly on a photographic plate. It seemed probable that the tissue would adhere to the photographic emulsion and would permit passage of the photographic chemicals as well as those used in the histologic technic. At the time that preparations for this experiment were under way, a method of attacking this problem was published by Belanger and Leblond (5). This consists of removing the emulsion from an unexposed lantern slide and spreading it over the tissue section. After proper exposure to the radioactive material contained in the tissue, the emulsion is developed and fixed. The preparation is then subjected to the usual histologic staining procedures. This method permits close contact between the tissue and the photographic plate. Also, the histologic preparation and the autograph are automatically superimposed. This method seemed to offer a solution of the problems outlined above, so it was tried along with the usual technic. The results were better than with the older method, but several objectionable features developed. The transposed emulsion varied in thickness, developed a heavy “fog,” softened easily, and tended to lift away from the tissue section. The emulsion became heavily stained, and study at high magnification was difficult. No doubt some of the faults were due to inexperience and could have been eliminated in time. It seemed advisable, however, to try mounting the tissue directly on a photographic plate. This method has been found to be satisfactory, and results are much better than those previously obtained.