An automatic isodose recorder.

An instrument has been devised which is capable of plotting automatically and without approximation, the dose distribution in radiation fields of any configuration, gradient or polarity. The plotting technique is believed to be novel and in one scan of the field any reasonable number of curves may be plotted, the information being presented on graph paper as dots which are subsequently joined to form isodose curves. The positioning accuracy is better than ± 0·5 mm, while the reproducibility of the servo-balancing system is better than ± ½ per cent.