The determination of the depth distribution of activity by spectral analysis: an estimate of its sensitivity to count density and resolution

The dependence of spectral depth determination to the number of counts recorded is investigated using 1, 2 and 3 sources of Technetium - 99m along the depth axis. The problems associated with defining a region of interest over the source at unknown depth are evaluated by considering the effects of spills into and out of the region on the depth determination process. It is found that spectral depth determination is very dependent on counts and very sensitive to spills. The use of the method to determine the depth of more than one source is open to question