Locating a "hot spot" in the lungs when using an array of four HPGe detectors

Considerable errors in the activity determination in lungs can be induced for the case of a "hot spot". Modern lung counter systems use several HPGe detectors, and the count rate ratios of the detectors can be used to locate the "hot spot" and apply correction algorithms. Some criteria for location determination of a point source in the lungs were investigated, and it is shown that an average error of up to about 10% can be achieved.