It all depends on whether what's needed is a quantitative assessment of backpressure, or just a qualitative one.

I've seen a number of ways in which below-knee prostheses are fitted, as that's what I have worn for the past 40 years, but it's always in the realm of "art/black-magic" as far as I can tell, as the experience and skill of the prosthetist is a major factor in the outcome. I've discussed this with one or two of these guys, and they seem to feel it's really important to know where the hard regions are, and where the transition regions are, and even which areas are predominantly soft and therefore moveable tissue. That soft tissue, BTW, often contains water which, when the device is worn, can be worked out, thereby affecting the security of the fit. That fit affects the precision with which one can control and rely on the footfall while walking. As the fluid in the stump is reduced by activity, the fit suffers, unless there's really good registration between the socket and the hard portions of the stump.

After several decades, the hard areas on my own stump are just skin covering bone. Shortly after amputation, that's not the case, though some prominent hard areas are already well defined. As the amputee ages post-op, the muscle can atrophy, becoming reduced in volume and more "flabby", making its location critical as opposed to those hard areas, as excessive movement can easily cause blistering.

I'm not sure how much useful information can be extracted from MRI or ultrasound records, particularly in view of the fact that incremental swelling occurs, at least in my case, as soon as the prosthesis is removed. This increases as time passes. I know it sometimes helps with fit if the amputee wraps the stump in an "ACE" bandage as the fit procedure progresses. Investigation of what quantitative information and qualitative information can be extracted from those examinations, but I do wonder how the data can be interpreted without involving specialized medical personnel.

Cost is a factor, after all, as some of us pay for some of our own prosthetic work.

I'm still aghast at the amount the MRI costs here in the U.S. That's probably not because of the hardware, but because of the specialized personnel required to interpret the resulting images.

RE