title: A radiotherapy dose integrator for 300 kVp x-rays.
abstract: Radiation dose given to patients undergoing radiotherapy by 300 kVp X-rays is detected by a thimble ionization chamber placed at the skin surface. Current from the chamber is amplified by a varactor amplifier, whose output is scaled by a calibration potentiometer before being converted into a frequency. This frequency is reduced by digital transistor-transistor logic (TTL) divider circuitry so that one rad of dose yields one pulse. The total dose is then accumulated by displaying TTL counters. The required dose is fed to the unit by a keyboard, and displayed. When the radiation dose given is equal to the dose that has been preset, then the X-ray exposure is automatically stopped. The salient features of the design are: failsafe operation, excellent reliability, minimal maintenance and simplicity, due to the use of modular and TTL circuitry. There is also a circuit in corporated in the design which checks the dose rate for continuity during an exposure.
mesh_terms: D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy; D014964:X-Ray Therapy / Q000295:instrumentation