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History of radiotherapy – a short introduction

Radiotherapy has its origins in the aftermath of the discovery of x-rays in 1895 and of radioactivity in 1896. Through scientific discoveries, trial and error, and technology advances, standardised approaches in external beam radiotherapy and brachytherapy were developed. Also, the development of the fields of radiobiology and radiation metrology was particularly important in making radiotherapy an effective treatment modality for cancer therapy.

External beam radiotherapy began with superficial and orthovoltage therapy with x-ray tubes and teletherapy with sealed radioactive sources. St Bartholomew’s Hospital pushed the limits of technology with the 1 MV x-ray tube in the 1940’s. Megavoltage therapy matured in the 1950’s with the development of the Cobalt-60 machine along with the medical linear accelerator. The betatron and microtron have also been used in radiotherapy. Hospital-based particle therapy arrived in 1989 and there are currently 57 particle therapy facilities worldwide in operation.

Brachytherapy using sealed sources began with Radium-226 (1901), and then followed brachytherapy with Radon-222 seeds, Caesium-137, Iridium-192 and Cobalt-60 sources, while other isotopes including Iodine-125 and Gold-198 have proved effective. Brachytherapy with beta sources such as Strontium-90 and Ruthenium-106 has niche uses. Various manual loading systems have been superseded by modern high-dose-rate Iridium-192 and Cobalt-60 afterloader systems and automated systems for delivery of Iodine-125 seeds to the prostate.