Last night I was reading some fascinating history of the first full-body MRI scanner and noticed that it's fundamentally different from modern scanners in one particular way: the static B field is vertical, while all the modern machines I've seen pictures of strongly suggest a static B field parallel to the patient's axis.

Is there a reason why most modern machines orient their static field along the patient's axis and not through their frontal plane - was that first scanner's vertical field a non-fatal "mistake"?

Are there implications for image quality depending on which slice is selected, or is there a limitation on which slices can be selected? Are axial slices (which I imagine to be what modern machines optimize for) perhaps more commonly useful than frontal slices?

Edit: I don't know why this was migrated without conferring with me. This question is about the application of these scanners, i.e. what medical diagnostic reasons are there to prefer one slice orientation over another. Clearly engineering issues impose constraints on what medical professionals can do, and I'm interested in those too, but I want this to be primarily about what these machines do (specifically with humans in the B field) rather than about how they achieve that.

  • $\begingroup$ I doubt if even radiologists can answer this. It's more of an engineering question than a medical question. $\endgroup$ – Carey Gregory Apr 5 '18 at 0:35
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    $\begingroup$ The only thing I can contribute is that axial slices are the most standard view for reviewing CT and MRI imaging. $\endgroup$ – DoctorWhom Apr 5 '18 at 1:48

An MRI needs a really strong static magnetic field for contrast on the image.. You can achieve such a strong field with a lot of coil windings, and passing a current through those coils. In modern devices the coils are also kept in a superconductive state to decrease losses: http://mriquestions.com/types-of-magnets.html

The closed bore layout is just the most cost-effective way to attain that high magnetic field. If we put it sideways we can easily add a moving table so the patient can just lay there. A vertical coil layout wouldn't be too comfortable for the patient.


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