Collimator Technology and Advancements

The single-hole collimator limits the field of view of a scintillation probe to a single organ. The sensitivity for counting is approximately equal over the entire field of view. The most common use of this collimator is for iodine uptake measurements of the thyroid. An example of this "flat-field collimator" is shown (Fig. I). The sensitivity profile at the working distance illustrates the relatively constant sensitivity over the field of view. The working distance, D, from the scintillation detector is a compromise. The working distance must be sufficiently large so that variations in organ depth (using the inverse square law) do not significantly affect the count measurement, while maintaining enough sensitivity for detection (also determined by the inverse square law). A complete treatment of these trade-offs has been described ( 1 ). For most probes, the working distance will be 20-30 em