How MRI Works - Part 2 - The Spin Echo

How MRI works - Part 2: The Spin Echo.
Part 1 - NMR Basics: • How MRI Works - Part 1...
Part 3 - Fourier Theory and kSpace: • How MRI Works - Part 3...
Part 4 - The Gradient Echo Sequence: • How MRI Works - Part 4...
Slides can be purchased here:
/ powerpoint-slides-how-...
0:00 - Intro
0:26 - What is Boltzmann Magnetization?
4:17 - Recap of the NMR Experiment and NMR Signal
7:04 - Clarification of Spin vs Ensemble Moments
8:42 - NMR Experiment Transmission (Tx) and Reception (Rx)
11:10 - Performing the NMR Experiment
13:07 - Two spins in different fields and T2*
16:09 - Larmor Distributions, Stacked spin dephasing and T2
19:23 - Transverse Magnetization M(t) and Frequency Distributions f(w)
25:00 - Larmor Distributions, Stacked spin dephasing and T2
27:43 - T2 vs T2* decay in Tissue
30:03 - Recap and Intro to the Spin Echo
30:49 - The Spin Echo Experiment
33:18 - Explanation of the Spin Echo
35:04 - Echo phase and Echo Math
37:14 - Conclusion and Exercises
38:11 - Outro
Drinking game: Take a drink every time I say "dramatically/substantially/drastically/ reduced".

[@thepirl903]

Error Correction: 13:30 - The units of gyromagnetic ratio are rad/s/T (I forgot a 'per second' in my slide). Note that the 'MHz/T' unit is fine though.

[@yyyyyyyyyz]

2 years later! I wasn't sure if part 2 would ever be published, but am happy to see it. Thanks for the great explanations!

[@AseveraTv]

the time has come *happy tears*

[@BryanQ95]

This absolute mad man delivers almost 3 years later. Excellent videos btw, I'm excited for part 3!

[@Aphelia.]

Can't wait for the part 3 coming in 2023

[@manuelbonet]

No need to wait that much! It was published 12 days ago

[@finanzasypersonas5060]

This is absolutely awesome. I just started my Ph.D. working with NMR and this information is absolutely worthy. Congratulations!!!

[@alop3933]

The Best, by far, the Best MRI video explanation series on internet. Excellent content.

[@pennypaul4997]

I started watching this series with zero knowledge of MRI physics. A year later during my MSc, man delivers. Great timing and great delivery! The animations are topnotch and the humour makes it even more fun. 🙌🏾

[@HiteshPatel-yb7jc]

Like others I was waiting expectantly for Part II, and now .... for Part III and IV! Aside from the information, we can also admire the production. Thank you.

[@andrewgerry7687]

I feel like these are the only super in-depth and or mathematical based videos worth watching on this platform for MRI physics. What is your background or expertise in? are you a diagnostic medical physicist?

[@jupa7166]

Subscribed "just in case" - yay! Second part of the best mri explanation on youtube! Thank you!

[@nigeriantvc]

This is the Best video lecture i ever watch on KZbin. I have been waiting for this 2nd part for more than a year. Thanks so much for this amazing great job Sir 💪🙌👏

[@ThirdHare]

So true! Animations used are fantastic.

[@ruenjou]

I'm glad I found this video yesterday; no need to wait for 2 years to see them all.

[@lexinwonderland5741]

I am so glad you're making this series-- please, please, PLEASE keep it up!!! I found you thru SoME2, but my primary focus is neuro-focused biochemistry, and getting a math based explanation to how the imaging works is so wonderful!! you've made me significantly more interested in radiology from your three videos alone!

[@91726]

This is hands down the BEST explanation of the spin echo

[@camicanu]

Can't wait for next part coming! This lectures are pure gold

[@AlexM-pu6kb]

A fantastic video series that I wish to see continued! Great explanations and even greater animations that truly make a difference to understand. Most of the videos out here are hard to follow due to lacking animations. This helps immensely and I cannot thank you enough and appreciate the work you put in this. Please do continue, I cannot wait for the next parts! Also, do you - or anyone else here - has a book recommendation for MR-Physics? Looking for one that also explains different sequences like TOF, FLAIR, CEST etc. Thanks!

[@ThirdHare]

Buzzing! I've been waiting two years for this video! Thank you!

[@gutterball10]

Excellent follow-up video.

[@abdallahalhalabi1275]

Best MRI explanation videos, please continue.

[@kerryl565]

Man, I cannot wait for Part 3 - I want to smart right now, haha! I appreciate how time consuming these videos must be to make with all the graphics and animations, and its because of the graphics and animations that make your explanation of the concepts so much more understandable than textbooks or traditional lectures - thank you!

[@RD2564]

Part 2 after 2 2/3 years, woo-hoo!!! Great vids, thanks for your efforts.

[@tinynudges]

This video is wonderful! I would pay for the next two!

[@jacobharris3002]

33:20 This finally made the relationship between the Free Induction Decay, the spin echo and graphs I have from my NMR lab come together for me. Thank you so much for this. I've been struggling to grasp this concept for a while.

[@plusleo1083]

Brilliant lecture. Full respect for your hard work to deliver knowledge to us.

[@ric1703te]

A very comprehensive approach since part I. Feeling thankful for finding the videos - I admire the effort put in them: the graphics and formulas used and explained in an understandable manner. Waiting expectantly for part III.

[@TheGutiserra]

😍😍😍 I thought we would never get a second episode. This is top tier material.

[@makrs30]

You are good. Thanks. Hope you make part 3!

[@SkatinBoy244]

Hell YES! I've been waiting for this video since the first one, astoundingly good explanations. Thank you!!

[@rukminiroyy]

Thank you for this; so happy i finally get what's happening aha please post more, you're doing a lot of us such a service !!!

[@KriptixxEdit]

Can't wait for the next videos to come!

[@felipemonteiro5877]

Yes!!! I've been waiting sooo long for this! Thank you very much for your efforts!

[@daviddoudouable]

Your videos part 1 and 2 are fantastic!!!!!!!!!! Jumping now to the next with delight!!!!!!!

[@anielaadamus9544]

Thank you so much for coming back with Part 2! As someone with zero medical knowledge and minimal physics background I'm finding these super clear and easy to understand! I needed a clear review of NMR principles for borehole logging applications and you videos definitely deliver :) Don't think I'll live long enough to see Part 3 and 4 though... a bit jealous of people who find your videos in the future when all parts are out haha

[@haroldfong8758]

Another great video about MRI

[@Frofelfel]

Wow i cant believe it you finally made it man ! Great

[@mattiterzi]

Most beautiful presentation of mri foundations. Huge congratulations

[@frzarlink]

These videos are awesome! Thank you.

[@harryhht8821]

Awesome visualization

[@guidoenriquelambertucci3542]

YEEEES! I was so waiting for this. THANK YOU

[@gjhufken]

Thanks for the valuable follow-up of part 1 !;-)

[@juang.8799]

Great explanation !! You made this very understandable. Thanks!

[@pigtowndanzee]

Thank you so much for these videos! I cannot even comprehend how much work goes into making them so I really appreciate it. As we all anxiously await the next videos, could you provide a couple of your favorite textbooks/papers/websites/whatever that you reference on this topic?

[@riteshdas5769]

I can already tell the Fourier video is gonna be a banger.

[@shivanisingh7090]

Great explanation!!

[@adammendez3632]

WOW YOU CAME BACK 2yrs of waiting HAHAHA cheers

[@steves8309]

Awesome explanations and great ASMR voice. The second time I watched it, I was asleep in minutes. Great videos!

[@AudioAtmos]

Thanks for doing this! It is the most informative and understandable presentation I have seen.👍

[@brynjarkarlsson8646]

Great stuff, thanks so much, worth the wait. Will recommend to my students.

[@roflawlmao123]

Fantastic!

[@212035720]

Outstanding Video.

[@Xraystocks]

Great work and understanding 👍

[@deepukurian9757]

Great explanations.. Waiting for the next videos

[@walrus4248]

The animation and quality of the narration voice are really excellent!

[@kindnessasgreatasthesea1158]

THANK YOU!

[@xinyanxiang4574]

What a nice video!

[@ceci7637]

Thank you very much 🙏🏻

[@scottdow5171]

I eagerly await your Fourier video!

[@user-dt1be8pb1m]

The best video about RM and SE that I have ever seen. Please, more. Are there more than three videos?

[@wesslesyt3304]

im starting MRI school soon I LOVE THIS STUFF. I await for part 3

[@RayJacobsenJr]

Thank you Thank you! Thank you!!

[@prashantkumar9167]

You did a very noble job sir... Love ❤you

[@engrhscabrera]

Waited for this video like I waited for Infinity War and Endgame.

[@ziyanyang9777]

This series on visual representation is just phenomenal. I wonder how long it take to produce all those 3D animations.

[@federico9472]

A video on Diffusion MRI would be great!

[@MarinatedPasta]

More plz ❤️

[@luc7478]

Thank you a lot

[@user-gr4rr5zj5e]

That's just awesome for a beginner like me!!

[@Gigaswing]

tnx for a great job...may there be a part 3 ?...would be great to see one :)

[@InquilineKea]

HOLY SHIT THIS IS SO GOODC

[@Thepiecat]

When are you getting a Patreon? Top notch quality, thank you for teaching us!

[@cmlon]

you are great!

[@dilshanwelagedara376]

Thanks very much 🤩

[@Mkoivuka]

Next do a short video on the visualization of MRI images in surgical navigation !

[@affanhassan]

Part 3 please!

[@axelknutt5065]

I had an MRI two days ago … I wondered why it was so cold in there. Now I know!

[@vadimtitko7087]

Nice video. Reminds me of 3Blue1Brown.

[@gabrielmorales2366]

Great video! What tool are you using to create the animations? Manim?

[@amianifineug1353]

thank you a lot! Please I want to use Matlab please do you have an idea which model I use in order to write a code in Matlab to study MRI (thank you)

[@daneilpatro2776]

hey thankyou

[@natashamol2961]

Amazing work!!! Best intro to MRI ve seen so far. Thank you so much 😍😍 Will be waiting for continuation 🙏🏻

[@noahoogeweg9562]

How did you make these animations? They are great!

[@1denvco]

Hello. Terrific content, it's been very helpful. I'm studying to take the MRI registry in Sept 2022 and was wondering what resources you are using or planning to use for your gradients, imaging, and pulse sequences video? Just in case it is not uploaded so I can study from there...if that is alright. I greatly appreciate the work you put into your content! TY

[@soleparadise4822]

How’d it go!? I am studying now and want to take the registry by May 2023!

[@amartinezsilberstein]

Part 3 🥺

[@mferraro89]

Do you have any textbook recommendations? I'd like to dive very deep into this and build myself an MRI machine

[@mahealom6076]

Please, give the GRE sequence physics's

[@36_azzamadnan28]

2 years after waiting :)

[@matheusdv3920]

thePIRL: "you shoul watch the first video or you migh get lost in this one" me: beeing already lost by the first part of tge first video haha just kidding, but most of the concepts are challenging to grasp

[@peterphan8991]

"deliver B1 perpendicular to B0 about the which our magnetization will precess" I cannot imagine where B1 placed in . Does it mean the B1 can be placed in any place just need parallel to the transverse, right?

[@alexlo7708]

Looks like the old system TV PAL sync. vector scheme.

[@831zlakin]

For T1 tissue signals, does the pulse of RF, like in the case ofT2 tissue signals with the Spin-Echoes, produce more available signal for imaging? Basically, I am trying to figure out if there is anything analogous to Spin-Echo but for T1 signals. Thank you for your help!

[@thepirl903]

Interesting question. There's no T1 'echo' of sorts like can be done with T2, but you can preserve magnetization from excitation to excitation by taking advantage of 'leftover' transverse magnetization between pulses. There are sequences that produce 'stimulated' echoes (distinct from spin echoes) which exhibit this effect. I think a magnetization preserving sequence such as steady-state free precession (ssfp/bssfp) or a look-locker (e.g., molli) might be close to what you're looking for, but I'm not sure. Hope this helps

[@831zlakin]

@@thepirl903 This does help, thank you!

[@sachinrajpandey5242]

I didn't see the video on gradients, imaging and pulse sequences, if anyone found that then please send me the link. Thank you.

[@paperbag76]

I watched Part 1 and it was great. However, I am stuck at 5:24 of Part 2, when the equation S = Mw first appears (Signal = Boltzmann Magnetization times precession frequency). This seems to come out of nowhere, without a derivation from any of the previous (S) Signal equations from Part 1.

[@nottyboi1349]

You should collaborate with Grant Sanderson!

[@Thepiecat]

Pretty sure he's using the python package that 3blue1brown uses

[@arpita0608]

Can I get the slide?

[@stargazer7644]

My only question is, who learns MRI technology at this level of detail? What course teaches it and who takes it? Is this simply for engineers who design this kind of equipment, or do the people who operate it or interpret the results also learn it?

[@OspreyII]

3 years later

[@kasrapirahesh6938]

Hi, I just don't get how the Radio Frequency signal generated by the RF coil causes the protons to spin in a perpendicular angle to the B0. Can someone explain this a bit (I don't mean the formula, just how does it happen)? Thanks for the great video by the way!

[@gabrielmorales2366]

Short answer: the RF coils are placed in such a way that the magnetic field that they generate (B1) is orthogonal to B0. When the coils are transmitting, the protons will tend to align their precession along the B1 axis. When the coils stop transmitting, the protons will relax again and align along the axis of the main B0 field.

[@msgreymatter4061]

In my (very limited) understanding: It's the magnetic field (creted by the protons' precession) which is orthogonal to B0 (i.e. in xy-plane) - not the individual precession itself. Spins are still either up or down. The 90° are not a literal description of the precession movement, but describe the accumulation of phase-coherent precession movement across multiple spins/protons. So there's a lot of 1H-nuclei (= 1 proton each) throughout the body --> 60-70% of us is made of water... But not all the hydrogen protons start to align to B0, only somewhat under 0.1% of them. And some spin in parallel direction to B0, while others spin anti-prallel to it. But there are slightly more spinning parallel, so we get a signal for the longitudinal magnetization from their cumulated vectors. Now the RF coil hits at the larmor frequency for hydrogen. This will cause *some* of those few parallel-precessing spins to change their direction to anti-parallel. Hence, the longitudinal signal is lost. But because the RF-pulse also brings them into phase coherence, the perfectly aligned precession movement across all of those spins now adds up and creates a measurable signal. And this signal is orthogonal to z, because they precede in the xy-plane (both parallel and anti-parallel spins). But they really have to be phase-coherent (i.e., always at the same position), otherwise the T2-signal gets lost again (like it does once the RF-pulse is switched off).

[@msgreymatter4061]

Corrections most welcome. I am nothing close to an expert on any of this.

[@ronaldpavon3434]

1. a. J/T (magnetic moment) b. Unitless 2. a. 0.02 b. 5.88e3 T c. 0.05 K *This does not look correct, I used the formula but It feel like something is missing 3. a. TB has a greater signal at TE, according to the amount of T2 weighting evaluated at that time. b. TB will still have the greater signal c. The greatest contrast would be achieved at the greater T2 of all tissues, therefore at TE = 40ms 4. TE = 7.699ms **I will do a follow-up later

[@Blueyzachary]

Wait so how did I understand more than half of this when I failed AP calc?

[@ah64Dcoming4U]

you beauty