We have lots of accuracy thresholds associated with all aspects of the patient’s treatment pathway.
For instance, we have accuracy thresholds for all the different parts of the machine that we test. They are generally of the order of 1-2 %.
Then we also have rules about the accuracy to which we create the treatment plans, generally it’s also a couple of %, and we incorporate any uncertainties associated with outlining the tumour, setting up the patient on the bed of the treatment machine etc.
We keep trying to improve the accuracy with which we treat, for instance through image guided radiotherapy, where you can ‘see’ what you treat, and by making immobilisation techniques better, so the patient doesn’t move much while being treated.