Mark-1 The world’s first whole-body MRI Scanner

Such a fantastic visual description

You do know that this language is historical? The MRI machines we use for modern medical practice would have been known as whole-body scanners because they are capable of scanning the whole body. This isn't about surveying the whole body as matter of course - the language is confusing though, so I understand.

It would be good when trying to determine if there's a build-up of plaque anywhere in a person's arteries and thus at risk of many different cardio-vascular diseases.

They use special dyes injected into arteries to facilitate seeing them. Similar things are done for examining the gastrointestinal tract of those who might have cancers somewhere in it.

You might also want to see if cancers have metastasized to other parts of the body to determine the extent of the disease.

No, oftentimes they will intentionality constrain the scan to a specific area that they’re interested in. This limits the time and cost. However there are pretty consistent scan procedures, eg they might order a “sacral MRI” for lower back issues.

As others have mentioned, full body MRIs may be used for cancer that they’re concerned may have metastasized. The reluctance of people to do this is that it’s kind of “going fishing”. If they spot something weird, they may wind up having to follow up on it even if it’s probably benign. They don’t want you to come back a few years down the road and hold them responsible for not looking into an ambiguous blotch on an MRI that turned out to be cancerous rather than benign. It’s not really scalable.

Someone on here did mention the idea of starting a program of doing full body scans of everybody and then building a database of what things turned out to be an issue to build a better automatic early detection system. It’s an interesting idea.

That being said, having an MRI really sucks. You put on ear protection and have to lay still for dozens of minutes or hours while the machine clicks, beeps, clunks, and buzzes at ear-splitting volumes (hence the ear protection). And since an MRI acts as a huge magnet, you can’t take headphones in with you. There was one or two places I went that had non-metallic ear phones, but this seems to be exception rather than the norm. Contrast means getting an injection partway through. And even if you’ve never had problems with claustrophobia, MRIs can still trigger it (there are open MRIs, but these may compromise on resolution).

So it’s very understandable that a reasonable amount of effort is made to minimize MRI time.

It can be when tracking the spread of tumours if a cancer has metastasised. This is anecdotal evidence based on a couple of friends who underwent cancer treatment.

It's not common in the sense that any significant %age of people have it done, but it's not unusual and there are numerous private medical screening facilities that do it for a fee. I had one done two years ago as part of a full body medical and plan to do so every two years or so in order to detect changes over the years (I was willing to take the risk of things being discovered during the first scan).

There are genetic conditions which can cause problems with any artery in your body, and you really want to know if anything's likely to go pop, anywhere. When you go for a full-body scan for this they're not going fishing, they're looking for something specific being wrong in a whole-body system.