Every test of that type was 3 weeks with me. The scan needs to be analysed and the report produced, and needs to go into the weekly MDT meeting where it's discussed to decide on next actions, and then a letter needs to go out inviting you to an appointment. Each of those takes a week.
I did knock a week off this for the bone scan report by getting the CNS to make me an appointment in advance, a couple of hours after the MDT where it would have been discussed.
This is all pre-COVID - might be longer now.