Radiotherapy

Radiotherapy is one of the principal modalities used in the treatment of cancer using ionizing radiation. It relies heavily on technology, software, and information systems. The collaborative efforts of Medical Physicists and several other health professionals are essential to quality and safety. A coordinated team approach influences the outcome of the treatment.

Radiotherapy has its origins shortly after the discovery of X-rays and radioactivity at the end of the 19th Century. Standardised approaches were developed over the years through scientific discoveries, observations, clinical assessments, trials, and technology advances. The concurrent development of the fields of dosimetry, radiobiology and radiation metrology were also particularly important in making radiotherapy an effective treatment modality for cancer therapy.

External beam radiotherapy (teletherapy) began with superficial and orthovoltage therapy with X-ray and sealed radioactive sources. Megavoltage X-ray therapy matured after the 1950’s with the production of high-energy sealed sources and the development of medical linear accelerators (linacs), which facilitated more effective treatment of deeper lesions. Cobalt-60 units and linacs are now the most widespread beam delivery technologies used for radiotherapy worldwide. Hospital-based light-ion therapy (proton and carbon-ion therapy) has also emerged over the past few decades. This modern technology is already used for patient treatment with more than 100 proton or light-ion therapy facilities currently in operation worldwide.

Brachytherapy using sealed sources began with utilizing Radium-226 at the beginning of the 20th Century. Other radioisotopes, such as Radon-222, Caesium-137, Iridium-192 and Cobalt-60, were subsequently used too. Further isotopes, namely Iodine-125 and Palladium-103, are used for permanent brachytherapy implants. In the last 20-30 years, manual afterloading systems have been superseded by automated afterloading systems that have enabled the use of high-dose-rate Iridium-192, Cobalt-60 and X-ray microsources, and robot-assisted systems for the implantation of Iodine-125 seeds into the prostate. Beta sources such as Strontium-90 and Ruthenium-106 also have specialized applications in cancer treatment.