[wmkn]

All manufacturers do this indeed. The “good” data is in the private fields that can only be read by the manufacturer’s proprietary software. The fields that are open for everyone usually have a lower quality version of the actual data. The latter is usually good enough for a small preview, but not good enough for proper diagnostic usage.

[mattkrause]

What sort of machines were you using?

My experience with research MRI/CT scanners is that the actual image data is usually where it's supposed to be.

[wmkn]

This was an ultrasound machine. Philips would first have you import the data in their own QLab software and from there export a copy (which misses some of the data from the private fields). With GE reading the data was completely impossible.