@solesky margins, in the context of radiation therapy for prostate cancer, refer to the area of normal tissue surrounding the prostate that is also targeted by the radiation beams. This is done to ensure that any microscopic cancer cells that might have spread just beyond the prostate are effectively treated.

The size of the margin is carefully determined based on several factors, such as the size and location of the tumor, the stage of the cancer, and the potential for microscopic disease. The goal is to maximize the effectiveness of the treatment while minimizing damage to nearby healthy tissues, such as the bladder or rectum.

I had the MRIdian linac with built in mri. My margins were 2 mm while most other non mri radiation machines use 3-5 mm so more healthy tissue is exposed. I have not heard what the margins are for the elekta unity machine.