MRI scanners can only barely do quantitative evaluations... between different scanners, and different scanning protocols, your body may look quite a bit differe

MRI scanners can only barely do quantitative evaluations... between different scanners, and different scanning protocols, your body may look quite a bit different and it is hard to know exactly how much variability to attribute to inter-scanner differences. There are whole studies done to try and quantify this, and it requires sending "human phantoms"- test subjects- around to different scanners, which requires you to physically take one subject around to several scanners operated by different people and stick them in there for a while. It's really involved.