A Profile Counter and its Calibration

Abstract

The distribution of radioactive iodine and other radioiso-tipes along the length of the body can be examined rapidly and quantitatively under reproducible conditions by a method suitable for repeated examinations on patients. The radioactivity of separate organs or sites of isotope concentration may be determined to within 10% accuracy by a simple calibration method. Calibration depends upon (a) the position of the source relative to the counter, (b) the size of the source, (c) scattering and absorption of radiation by body tissues. Allowance can be made for these by recording the change in counting rate as a counter is moved past the position of the source, and from the values of the height and width of the resultant peak in the "profile" curve plotting counting rate against counter position.