A New Integrating Dosemeter for X-ray Therapy

For some years the two principal integrating dosemeters used for deep therapy have been the Mekapion and the Hammer. These have a similar design structurally, each comprising a thimble-type ionization chamber which is attached to the instrument head, and which may be placed on the skin of the patient as desired for treatment. Electrical connections from the head to the dial of the instrument serve to operate this latter, which indicates the total dose received. The two dosemeters differ in that the Mekapion incorporates an electrometer valve in the instrument head to operate a relay when a certain charge has been dissipated in the chamber; the Hammer uses an electrostatic relay connected to the central electrode of the chamber which likewise operates the recording mechanism when the charge has dropped to a certain value. Both these instruments have proved themselves capable of reliable working over long periods. An alternative system is therefore put forward only after careful consideration of two factors...