A Machine has been built in the Hammersmith Hospital Physics Department to relieve the tedium of routine isotope scanning by hand. An automatic scanner was needed which had to be cheap, within the capabilities of our limited work-shop, and using as much standard equipment as possible. It was felt that it would be desirable for the machine to give not only the pictorial distribution of radioactivity localised in part of the body, but also the same information as a hand-operated scan, i.e. the count-rate at any point and lines of equal count-rate or isocount lines. The principle of the so-called “scintiscanner” is familiar (e.g. Bolliger and Poretti, 1956); a pictorial distribution is built up from a series of black marks on paper—a single mark being made for a selected total number of pulses received. At higher count-rates the dots are closer together than at lower count-rates and the eye is capable of picking out the areas of higher count-rate as areas of greater density of dots (Fig. 8). In order to obtain the actual count-rate at a point one must either count up the dots per unit area or take a separate reading over any point with the detecting counter connected to a normal scaler or ratemeter. It is possible, but rather impracticable, to draw isocount lines on these pictures. A commercial “scintiscanner” is expensive to buy, but one could be built for considerably less.
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Mallard et al. (1959) studied this question.