What type of sources was the Manchester system originally developed for?

The Manchester system, which was established for the dosimetry of brachytherapy, was originally developed for the use of 226Ra sources. This system arose in response to the need for a standardized method of calculating dose distributions for patients undergoing brachytherapy with radium isotopes. 226Ra was historically one of the most commonly used isotopes in this form of treatment due to its suitable half-life and radiation characteristics, which allowed for effective therapeutic applications in cancer treatment. The system provides guidelines for setting up treatment plans and understanding the interactions of radiation with tissue, making it foundational for the principles of brachytherapy that exist today.

The other isotope choices—192Ir, 125I, and 103Pd—are all used in brachytherapy but were not the focus of the initial development of the Manchester system. Each isotope has its own specific characteristics and applications in modern radiation therapy, but they were introduced after the Manchester system, which centered around the principles and calculations associated with 226Ra treatment.