Well, those machines are quite big, but the hole where the person fits is not so large. How would one fit a really fat person inside one of those? I mean, the person could probably suffocate or get one of his/her fat rolls caught on the machine. Is there an extra large CT scan machine?
I’ve seen warning signs on xray and CT machines. I think the limit was 300 or 350lbs? I remember thinking how embarrassing it would be to get rejected for a scan. I hate that confined feeling going into that CT tube.
The technician didn’t pull out a scale and check my weight. I guess they may ask someone very obese what they weigh.
There are “open CT” and “open MRI” machines now. I’ve seen ones that wrap around over top the patient and are open on the sides, or ones open mostly on one side but not another.
Ok, I found something rather amuzing/disturbing: http://www.dailymail.co.uk/health/article-2086306/Obese-patients-Zoo-scanners-used-large-fit-hospital-ones.html
There’s no such thing as open CT. The collimators have to travel in a circle around the patient, but there isn’t a tunnel like in an MRI, just a big donut shaped box.
Different models have different weight limits. And even on the same machine, different types of scans will have different weight limits, for instance a fatter person could get a head scan but maybe not a pelvis scan because they would need to be cantilevered out over open space to get their mid-section into the aperture.
The open-type machines can be useful for the claustrophobic as well as the obese. My mother was supposed to have a scan (can’t remember if it was a CT or an MRI scan) and she was really nervous about it. So they doped her up on Valium and even then my father had to sit in the room holding her hand the entire time.
I was scheduled to have an open-view MRI when I was almost 400 lbs. The technician put a plate on my chest and started to “force” my body into the machine. While open on the sides, it was still a fixed height from the table to the top of the machine. As soon as I started feeling the compression on my chest, I instantly had a panic attack and had to be removed.
While the insurance company wasn’t happy, they agreed to find a larger machine which I fit into without incident. Different manufacturers have different styles and sizes so with a little research, even the morbidly obese should be able to have the test.
A standard CT will hold around 400 lbs. Some can hold more. If the patient is too heavy for the machine, they don’t get the scan. Even if they are just below the weight limit, there are problems. Image quality is poor, and if their body touches the scanner torus, there’s a lot of artifact. They may wind up getting the scan, but the study may not help with diagnosis.
MRI machines also have weight limits, and often the patient will not fit inside the narrow bore of a standard MRI. Open MRIs have image quality compromises as well.
If the patient is too fat to fit in the scanner then…they don’t get a CT. At my last hospital the weight limit for CTs was 350 lbs. At my current hospital the table is much stronger and there isn’t a stated weight limit so the limiting factor is circumference. So anyone can get a CT head but an extremely obese patient might not be able to get a CT chest or abdomen. In which case you go to plan B, whatever it is. An alternate (suboptimal) form of imaging, admission for observation and serial exams, try convincing the surgeon to take them to the OR without imaging, etc.
I had an MRI in an ordinary machine about 15 years ago when I was close to 300 lbs, and it was uncomfortable fitting into the machine. The tube compressed me. If you think having the tube so close to you makes you claustrophobic, just try a tube that doesn’t fit around you without squeezing.
I can see why they’d resist getting larger machines. The regular machines cost about a million dollars per tesla, last I heard. Teslas are a measure of how intense the magnetic field is, and the best neodymium-iron-boron permanent magnets develop an intensity of a touch over one tesla on their pole faces, enough to dimple water (which is weakly repelled by magnetic fields). Getting that intense a field in a space big enough to put an ordinary person into costs one million bucks. Bigger people drive the price way up.