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Lea Alhilali, MD

@teachplaygrub

Mar 25 • 11 tweets • 4 min read • Read on X

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1/How low can you go??

All the hype nowadays is about high field MRI, but what about low field??

Read on for this month’s @theAJNR SCANtastic for what to know about what may be the next biggest thing in MRI!

ajnr.org/content/47/3/7…

2/The growing strength is for larger & larger field strengths for higher & higher resolution

So why would we possible go backwards to lower field strength?

Turns out there are some advantages.

3/Low field strength magnets are much for flexible

They can be put in non-traditional settings (clinics) & can also possibly be moved to the bedside

It is truly POC MRI!

But how does it perform?

4/For infarcts, it tends to see the forest instead of the trees.

It is very good at detecting large infarcts & performs equivalently to normal field strengths

5/However, it can miss smaller infarcts or they can be much more difficult to see

But, with the advent of deep learning AI algorithms, the image quality can be enhanced to lower the risk of missing small findings

6/The question is: how good does the quality HAVE to be?

Yes, we may love amazing 3T images, but often, we don’t need that degree of image quality or detail to make the correct diagnosis.

Lower field strengths can suffice.

7/It’s like food.

Would you like a Michelin starred meal? Yes.

Do you really need it? No. Regular food is good enough to suffice.

8/And low field MRIs have a big advantage when it comes to susceptibility artifact

Larger field strengths are more sensitive to susceptibility—which can obscure pathology.

It’s just like how larger ears are more sensitive to noise—it’s not always a good thing!

9/You can see here how lower field strengths actually make the canal MORE visible than on higher field strength bc there is less susceptibility artifact from the patient’s hardware.

10/In this months @theAJNR, Rao et al. found low-field MRI was 92% sensitive & 86% specific for detecting infarcts in ventilated ICU patients

And it changed management in nearly 40%

11/Hopefully now you know that good things can often come in small field strengths!!

But this only scratches the surface!

Follow @theAJNR & check out the article for yourself:

ajnr.org/content/47/3/7…

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More from @teachplaygrub

Lea Alhilali, MD

@teachplaygrub

Jan 27

1/The hardest thread yet! Are you up for the challenge?

How stroke perfusion imaging works!

Ever wonder why it’s Tmax & not Tmin?

Here’s what to know from @theAJNR SCANtastic!

ajnr.org/content/47/1/28

@TheAJNR 2/Perfusion imaging is based on one principle: When you inject CT or MR intravenous contrast, the contrast flows w/blood & so contrast can be a surrogate marker for blood.

This is key, b/c we can track contrast—it changes CT density or MR signal so we can see where it goes.

@TheAJNR 3/So if we can track how contrast gets to the tissue (by changes in CT density or MR signal), then we can approximate how BLOOD is getting to the tissue.

And how much blood is getting to the tissue is what perfusion imaging is all about.

Read 19 tweets

Lea Alhilali, MD

@teachplaygrub

Jan 19

1/Do you get a Broca’s aphasia trying remember the location of Broca's area?

Does trying to remember inferior frontal gyrus anatomy leave you speechless?

Don't be at a loss for words when it comes to Broca's area

Here’s a 🧵to help you remember the anatomy of this key region!

2/Anatomy of the inferior frontal gyrus (IFG) is best seen on the sagittal images, where it looks like the McDonald’s arches.

So, to find this area on MR, I open the sagittal images & scroll until I see the arches. When it comes to this method of finding the IFG, i’m lovin it.

3/Inferior frontal gyrus also looks like a sideways 3, if you prefer. This 3 is helpful bc the inferior frontal gyrus has 3 parts—called pars

Read 13 tweets

Lea Alhilali, MD

@teachplaygrub

Dec 5, 2025

1/They say form follows function!

Brain MRI anatomy is best understood in terms of both form & function.

Here’s a short thread to help you to remember important functional brain anatomy--so you truly can clinically correlate!

2/Let’s start at the top. At the vertex is the superior frontal gyrus. This is easy to remember, bc it’s at the top—and being at the top is superior. It’s like the superior king at the top of the vertex.

3/It is also easy to recognize on imaging. It looks like a big thumb pointing straight up out of the brain. I always look for that thumbs up when I am looking for the superior frontal gyrus (SFG)

Read 12 tweets

Lea Alhilali, MD

@teachplaygrub

Dec 1, 2025

1/To call it or not to call it? That is the question!

Do you feel a bit wacky & wobbly when it comes to calling normal pressure hydrocephalus on imaging?

You don’t want to overcall it, but you don’t want to miss it either!

Let me help you out w/a thread about imaging in NPH!

2/First, you must understand the pathophysiology of “idiopathic” or iNPH.

It was first described in 1965—but, of the original six in the 1965 cohort, 4 were found to have underlying causes for hydrocephalus.

This begs the question—when do you stop looking & call it idiopathic?

3/Thus, some don’t believe true idiopathic NPH exists.

After all, it’s a syndrome defined essentially only by response to a treatment w/o ever a placebo-controlled trial.

However, most believe iNPH does exist--but its underlying etiology is controversial. Several theories exist

Read 19 tweets

Lea Alhilali, MD

@teachplaygrub

Nov 21, 2025

1/Time to go with the flow!

Hoping no one notices you don’t know the anatomy of internal carotid (ICA)?

Do you say “carotid siphon” & hope no one asks for more detail?

Here’s a thread to help you siphon off some information about ICA anatomy!

2/ICA is like a staircase—winding up through important anatomic regions like a staircase winding up to each floor Lobby is the neck.

First floor is skullbase/carotid canal. Next it stops at the cavernous sinus, before finally reaching the rooftop balcony of the intradural space.

3/ICA is divided into numbered segments based on landmarks that denote transitions on its way up the floors.

C1 is in the lobby or neck.

You can remember this b/c the number 1 looks elongated & straight like a neck.

Read 10 tweets

Lea Alhilali, MD

@teachplaygrub

Nov 4, 2025

1/The 90s called & wants its carotid imaging back!

It’s been 30 years--are you still on NASCET?

Feeling vulnerable about plaque vulnerability?

This month’s @theAJNR SCANtastic has what you need to know about carotid plaque

ajnr.org/content/46/10/…

2/Everyone knows the NASCET criteria:

If the patient is symptomatic & the greatest stenosis from the plaque is >70% of the diameter of normal distal lumen, patient will likely benefit from carotid endarterectomy

But that doesn’t mean the remaining patients are just fine!

3/Yes, carotid plaques resulting in high-grade stenosis are high risk

But assuming that stenosis is the only mechanism by which a carotid plaque is high risk is like assuming that the only way to kill someone is by strangulation.

Read 13 tweets

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