Cereal Chem 68:339-343   |  VIEW ARTICLE

Effect of Image Resolution on Insect Detection in Wheat Radiographs.

P. M. Keagy and T. F. Schatzki. Copyright 1991 by the American Association of Cereal Chemists, Inc. 

Wheat kernels were exposed for three days to adults of three insect species (Sitophilus zeamais Motschulsky [maize weevil], Rhyzopertha dominica (F.) [lesser grain borer], and Sitotroga cerealella (Oliv.) [Angoumois grain moth]); the kernels were incubated and X-rayed to produce contact films at three- to four-day intervals. The objective was to develop specifications for automated grain-inspection systems and evaluate the effectiveness of current radiographic methods. X-ray images of infested and uninfested kernels were presented to four trained subjects as original films and digitized video images at four magnifications corresponding to 32.8, 65.6, 131.2, and 262.4 micrometers of film per pixel. Insect detection was a sigmoidal function of insect age. The age required for 50% detection varied linearly with log pixel size (micrometer of film per pixel). Visual detection from the original films was similar to that from the 65.6 micrometer/pixel resolution. Ages for equivalent detection increased from the maize weevil to the Angoumois grain moth to the less grain borer, reflecting the rate of maturation of the indivdual species. Development of any automated image-acquisition system equivalent to visual inspection will depend on the availability of an X-ray sensor that is 65 micrometers or smaller.