A liver phantom for evaluating camera and scanner performance in clinical practice.

An assessment of the resolution of different cameras and scanners may be made using phantoms which bear no physical resemblance to human antomy. Examples are the “slice” and “grid” types of phantom. In the former, there are areas of increased and diminished radioactive concentration relative to that of background. In the grid types, linear sources may be constructed using polythene tubing and then embedded in a Perspex block, or a series of parallel lead strips separated by a distance equal to their width, may be attached to a Perspex plate and placed over a uniform bath of activity. They will produce a valid comparison between detection systems, but the observed resolution characteristics cannot be precisely related to tumours seen in clinical practice. It is suggested that an anatomically realistic phantom will provide additional useful information and should be used to complement, rather than replace those already mentioned.