In the Manchester system, the treatment plane for a single implant is positioned at what distance from the source plane?

In the Manchester system, the treatment plane for a single implant is positioned at a distance of 5 mm from the source plane. This standard distance is critical in ensuring the dosimetric accuracy necessary for effective treatment delivery. The specification of 5 mm is based on the physics of brachytherapy, where the dose delivered is determined by factors such as the source strength, the geometry of the implant, and the tissue characteristics surrounding the sources. By standardizing the treatment plane at this distance, dosimetrists can ensure that the planned dose will conform closely to the tumor volume while minimizing exposure to surrounding healthy tissues. This is important for optimizing treatment outcomes and minimizing side effects.