Computer-assisted thyroidal technetium uptake measurement using a short pinhole-to-surface distance

The close pinhole view of the thyroid presents some important measurement problems. Possible errors due to gland, neck and set-up geometry are accentuated due to the effects of the inverse square law, and care is needed to control these. The nonuniform response inherent in the use of the pinhole collimator has a significant effect, but with computer processing this is readily eliminated. ENR subtraction may become difficult in certain circumstances, as insufficient "background areas" may be viewed, but it has been shown that the use of a "universal" (for the particular system) ENR subtraction may give, if anything, more accurate results. With these precautions in use, important errors will be of the same order of magnitude as those involved in more distant views, and may thus be kept within the realms of clinical significance. On the other hand, considerable improvements in both resolution and sensitivity make the use of the closer view an asset to both the research laboratory and the small department involved mainly in routine service work.