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A key problem with high-res MRI in a living organism is the scan time. Even fast acquisition techniques like EPI require around 50 milliseconds per slice. But i
by scythe 4y ago
A key problem with high-res MRI in a living organism is the scan time. Even fast acquisition techniques like EPI require around 50 milliseconds per slice. But if you want good resolution and contrast you're doing a spin echo which takes quite a bit longer. At some point you run into motion blur caused by the mere involuntary contraction of blood vessels, and that's before you consider the difficulty with patient compliance to the directive: "hold still".
- azalemeth 4y agoIndeed. To say nothing of gating acquisitions to breathing, head motion, eye cicadas, glymphatic flow, etc. The highest resolution MR images I have (yet) obtained were ~20 µm^3 voxels on ex vivo (human) tissue samples fixed in agar with Gd3+ as a dopant, scanned at 12 T on a preclinical scanner. The coupled vibration of the gradient set causing blurring in the image domain at the extremities of the FOV was the limiting factor. I recall I did a partial Fourier acquisition – as ultimately we were limited by both T2* and vibration – and ended up trying to do POCS on a 4096^3 dataset and just needing tons and tons of ram to do it over something useful, like a weekend. Happy memories.
- cperciva 4y agoIf you want to scan the entire organism, sure. But higher resolution MRI can also mean "scan a smaller part, with good detail, in the same amount of time". I could imagine this being useful for e.g. getting a high resolution image of a tumour after conventional imaging was used to locate it.