Methods of decreasing the fog density level in an autoradiographically intensified image were investigated. The methods included a more proportional conversion of silver to silver sulfide, decreasing the amount of fog silver in the original image, and minimizing the formation of fog in the original image. Thirty percent exposures of an aluminum 11 step wedge and a lead resolution target were made using Kodak film type XG-1. The underexposed films were either developed in the Kodak RP X-Omat processor or manually developed. All the films were radioactivated in an alkaline solution of sulfur-35 thiourea for 30 minutes. The activated films were exposed to Kodak film type NMC in a radiographic cassette for a specified period of time. The resulting autoradiographs were developed in the X-Omat processor. A more proportional conversion of silver to radioactive silver sulfide was obtained by increasing the amount of nonradioactive thiourea in the activating solution. The addition of 0.0014 g. of nonradioactive thiourea resulted in a 70% decrease in the fog density of the autoradiograph and a 40% increase in gamma, but at the expense of a 40% decrease in ASA speed. The use of potassium ferricyanide as an oxidizing agent during the radioactivation resulted in increased fog density, while the use of hydrogen peroxide as an oxidizing agent produced little or no effect on the intensification. Manually developing the underexposed image for a shorter period of time (1 min. instead of 3 min.) resulted in decreased fog from a density of 1.31 to 0.58 and increased contrast from 1.2 to 2.2, while the ASA speed remained unchanged in the intensified image. A fixed-out film which was treated in the photographic subtractive reducer prior to activation did not produce any intensified image; thereby, indicating that sulfur-35 thiourea does not react with the gelatin.

Library of Congress Subject Headings

Autoradiography--Films; Images, Photographic; Photography--Developing and developers

Publication Date


Document Type


Department, Program, or Center

School of Photographic Arts and Sciences (CIAS)


Owunwanne, Azuwuike


Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in December 2013.

Physical copy available from RIT's Wallace Library at TR283 .W49


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