6 ms·

For a change, I can contribute something to HN without being out of my depth:) Background: I'm a doctor with 3 years experience in acute medicine. AMA Clearin

by Amarok 7y ago

For a change, I can contribute something to HN without being out of my depth:) Background: I'm a doctor with 3 years experience in acute medicine. AMA Clearing some MRI misconceptions: 1. It's indicated ASAP in specific emergencies and will change how we manage them. For acute ischaemic stroke, it detects patients within the recomended time window for thrombolysis. Simply, it shows the cellular swelling in the brain, gives an estimate of the onset and we decide the risk/benefits of dissolving the clot. Second use, for cauda equina syndrome. Again we're looking for acute CNS tissue damage, this time from spinal chord compression, and the change in management is emergency neurosurgery (good luck getting them out of bed without an MRI) For herpes encephalitis, MRI is debatable because you can start empiric treatment. But I've seen it done. Another misconception for the first use scenario in stroke. The MRI sequences we're interested in only take 1-3min and CT doesn't help us. But in my experience the whole scan takes 2h to organize, so point of care MRI is a game changer. Every minute counts when you're saving brain tissue. And Lower definition with artifacts are acceptable because you're looking for gross changes in a critically unwell patient. Bonus: A report from when I managed my first suspected stroke as a junior doctor. "49yo lady day 1 post op for total knee replacement (elective admission). Commorbidities of hypertension, obesity and osteoarthritis. She was just started on apixaban and gabapentin as per protocol, when I was asked to see her for new onset upper limb bilateral tremor. On examining her I found the symptoms had started 1h ago. She was presenting bilateral upper limb ataxia as well, reflexes were reduced on the left and there was numbness corresponding to C4 dermatome. At this point I was worried about acute stroke whithin the 4h window for thrombolysis. I discussed the case with the acute stroke consultant and examined the patient with him. We requested an MRI brain to assess for acute posterior circulation stroke, because he thought time of onset was unclear (as per WAKE-UP protocol). I acompanied the patient to neuroradiology services. The MRI sequences we were most interested was DWI and FLAIR which only took a few minutes. We quickly scanned through the images noting there were was no DWI-FlAir mismatched high intensity signal areas within the brain parenchyma. This allowed us to rule out acute ischaemic stroke. 6h later the symptoms subsided and I was satisfied they were due to an adverse reaction to gabapentin."

mdorazio 7y ago
It says the clearance includes head scanning, but could this also be used for things like orthopedics? Current MRIs are prohibitively expensive and bulky for all kinds of things outside head trauma that could benefit from tissue imaging.
- Amarok 7y ago
  Oh orthopods, they're a riot in the Uk. They won't have much use for a portable MRI. In trauma all they see is the bony bits where CT and XR are king, anything else is someone else's problem. A true ortho emergency is rare and patients can wait for surgery if neurovascular intact. They do have time guidelines to operate neck of femur fractures (still won't operate out of hours though). But an XR is often enough to proceed . A few caveats I can think of... For fulminant infection like necrotizing fasciitis: straight to OR, open and have a look at the tissues. Joint infections: stick a needle in and await results. Bone infections benefit from MRI but there's no change in management while stabilizing on antibiotics, plenty of time to arrange a scan. Then we move on to elective surgery (planned). MRI with the best available resolution will increase diagnostic specificity and avoid unnecessary operations to labrum's, meniscus, etc. They don't need to be done in hospital and you can shop around. At this point we're looking for problems to fit this solution, poor business model. Not surprisingly, limb only MRI machines haven't been successful.
  - mdorazio 7y ago
    Fair points, but my thinking was more for cases here in the US where insurance may or may not cover an MRI of your choice for something like torn rotator cuff, or where you'll end up paying your full out of pocket maximum for it. Cheaper options in such cases would be welcome.
lijf 7y ago
Being a neuroradiologist (at Karolinska in Stockholm, Sweden) I really love the idea of this and almost can’t wait to start doing comparative studies to find how sensitive it really is. As I see it there are a couple of areas where it could be of tremendous use - first of course the (neuro) intensive care unit, where patients sometimes are to unstable to transport to the MRI, and where every transport is a potential risk for the patient, and where it can be very useful to find out whether they have ischemic lesions in the brainstem (which can be difficult to rule in/out on CT) or extensive diffuse axonal injuries, etc. Another area would be pediatric imaging, where it could be useful as a first imaging, ruling out larger lesions, possibly lessening the need for CT and decreasing radiation exposure, especially in the group approximately 1-4 years, who often need sedation to lie sufficiently still inside the MRI. Although at my institution the physicists have developed a ‘fast MRI’ (70 seconds), that gives reasonable resolution and contrast (T1,T2,T2*,DWI), and which we will try to implement in the group of patients who come to ‘try’ the machine (before deciding whether they need sedation or not). Also, the low field strength, 0.064T vs 1.5T or 3T, would most probably allow us to image patients with implants which are unsafe at normal clinical field strengths of 1.5 or 3T (would have to be verified though). For people interested in low field imaging the group at Athinoula A Martinos Center for Biomedical Imaging at Harvard has a homepage at https://www.nmr.mgh.harvard.edu/lab/lfi https://www.nmr.mgh.harvard.edu/lab/lfi

by Amarok 7y ago

mdorazio 7y ago

It says the clearance includes head scanning, but could this also be used for things like orthopedics? Current MRIs are prohibitively expensive and bulky for all kinds of things outside head trauma that could benefit from tissue imaging.

Amarok 7y ago
Oh orthopods, they're a riot in the Uk. They won't have much use for a portable MRI. In trauma all they see is the bony bits where CT and XR are king, anything else is someone else's problem. A true ortho emergency is rare and patients can wait for surgery if neurovascular intact. They do have time guidelines to operate neck of femur fractures (still won't operate out of hours though). But an XR is often enough to proceed . A few caveats I can think of... For fulminant infection like necrotizing fasciitis: straight to OR, open and have a look at the tissues. Joint infections: stick a needle in and await results. Bone infections benefit from MRI but there's no change in management while stabilizing on antibiotics, plenty of time to arrange a scan. Then we move on to elective surgery (planned). MRI with the best available resolution will increase diagnostic specificity and avoid unnecessary operations to labrum's, meniscus, etc. They don't need to be done in hospital and you can shop around. At this point we're looking for problems to fit this solution, poor business model. Not surprisingly, limb only MRI machines haven't been successful.
- mdorazio 7y ago
  Fair points, but my thinking was more for cases here in the US where insurance may or may not cover an MRI of your choice for something like torn rotator cuff, or where you'll end up paying your full out of pocket maximum for it. Cheaper options in such cases would be welcome.

lijf 7y ago

Being a neuroradiologist (at Karolinska in Stockholm, Sweden) I really love the idea of this and almost can’t wait to start doing comparative studies to find how sensitive it really is. As I see it there are a couple of areas where it could be of tremendous use - first of course the (neuro) intensive care unit, where patients sometimes are to unstable to transport to the MRI, and where every transport is a potential risk for the patient, and where it can be very useful to find out whether they have ischemic lesions in the brainstem (which can be difficult to rule in/out on CT) or extensive diffuse axonal injuries, etc. Another area would be pediatric imaging, where it could be useful as a first imaging, ruling out larger lesions, possibly lessening the need for CT and decreasing radiation exposure, especially in the group approximately 1-4 years, who often need sedation to lie sufficiently still inside the MRI. Although at my institution the physicists have developed a ‘fast MRI’ (70 seconds), that gives reasonable resolution and contrast (T1,T2,T2*,DWI), and which we will try to implement in the group of patients who come to ‘try’ the machine (before deciding whether they need sedation or not). Also, the low field strength, 0.064T vs 1.5T or 3T, would most probably allow us to image patients with implants which are unsafe at normal clinical field strengths of 1.5 or 3T (would have to be verified though). For people interested in low field imaging the group at Athinoula A Martinos Center for Biomedical Imaging at Harvard has a homepage at https://www.nmr.mgh.harvard.edu/lab/lfi https://www.nmr.mgh.harvard.edu/lab/lfi