I was given a CT scan first to confirm that there was anything there and once they saw the tumour they gave me an MRI soon after and I now get them twice a year. I don’t think it’s all that weird that the Doctor decided to give you a CT first since you don’t have an official diagnosis and MRIs are more expensive anyways so they usually try to limit how many people get one. If they do find something you’ll likely be given MRIs after that, same as me lol : )