Introducing MRI: Introduction to NMR - Spin Angular Momentum and Precession (4 of 56)
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- เผยแพร่เมื่อ 22 ก.ย. 2014
- www.einstein.yu.edu - The fourth chapter of Dr. Michael Lipton's MRI course covers introduction to NMR - Spin Angular Momentum and Precession. Dr. Lipton is associate professor radiology at Albert Einstein College of Medicine and associate director of its Gruss Magnetic Resonance Research Center.
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Thanks to this channel I wish I could be one day a better radiologist...and now that I'm a radiologist in formation, it's working perfectly! Thank you!
Thank you so much Albert. I started following the video series and its been so helpful
Your explanations are so elegant man. I'm actually enjoying this. update: I'm hooked. brilliant
we cannot directly measure the NMV because it is too tiny and also because it is in the same direction as that of B0. Dr Lipton has stated that NMV is antiparallel to B0 but actually it is parallel to it. A very simple, funny example is given in the "MRI Physics Made Easy" book on page 15.
Thankyou for the save, I was here to get a recap and almost go a confusion till I found your comment.
For those confused about parallel and anti parallel alignment. Most text book aren't necessarily telling you the whole, or indeed any, truth!! Read this paper, it explains well: 'Is Quantum Mechanics necessary for understanding
Magnetic Resonance'? LARS G. HANSON
Thanks for this, very insightful and just what I needed.
When the head of the vector is precessing around in a circle what is holding the tail in a fixed location? I would expect the mid point of the vector to be fixed in space and both the head and tail to precess around in circles.
The protons align parallel to the direction of the external magnetic field more than anti-parallel due to the fact that anti-parallel alignment needs more energy? Isn't that the case. I'm a bit confused.
hariharan ramesh yes, you're right
If that were the case the net would be parallel to the externally applied magnetic field but it's not
Watch this: 19:08
Thank you for such an understandable presentation🤍🤍🤍
Sir you are simply fabulous
I couldn't agree more with you. Really fine explanation!
Day 1 Chapter 4 done
Thanks prof for magnificent information and explanation for these basics
i want to clearviy that is the NMV orianted with the B or anti B?.
is there anti parallel more than parallel protons or not?
mimu mimu The way I understood, most of the protons' magnetic fields are antiparallel to the externally applied magnetic field, causing the net magnetization vector (NMV) of the protons to be antiparallel to the externally applied magnetic field.
Ben Swain the way i've understood every other resource on mri, is that this is wrong. NMV aligns WITH/PARALLEL to external field. This is because low energy states simply do not have the energy to oppose the external field, and since there are more of them in low energy states - they align WITH. I HATE it when I find conflicting information like this.
***** youre right, more protons are WITH/Parallel
I am in the exact same position you were two years ago! Reading Farr's it specifically states more protons spin up (WITH the external field) than against because it is less energy to do so. Is this just a mistake in this video? Two years down the line can anyone clarify..?!
Oh wait, it's been answered by the man himself on the next video!
So is each proton already a magnet before it begins to precess or does it produce a magnetic field by being a moving charged particle?
Yes and Yes! In this case, the effect is due to the intrinsic spin of the proton. When placed in a magnetic field, it will start to precess because of the torque on it from the external magnetic field.
Recomend us best MRI book professor
How come that no one was capable of answering his questions although some of them being radiology residents?
How can anyone dislike this video ?
Perhaps because he got something very fundamental incorrect and it is confusing people.
@ 4:50 WARNING: Larmor-frequency (in rad/sec) = precession-frequency (in Hz.) x 2.pi. So ONLY the precession-frequency tells you the number of revolutions per second around the static B-field; not the famous Larmor-frequency! The Larmor-frequency is an ANGULAR frequency. Confusing use of terminology by dr. Lipton.
so Larmor-frequency (angular frequency) still tells you the number of revolutions per second though, just have to divide the larmor-frequency by 2pi, right? I get what you're saying tho
@@daviddavies7871 Yes, you got it ;-)
Why TF is required.
Why Rf required.
To get a transverse component of the M-vector by means of resonance.
too slow
TH-cam has an option to increase the speed. I listen it in 2.0
The speed for those who have English as a first language is slow, but it’s perfect for the others like me. I am from Brazil and we speak Portuguese. Increasing the speed at the video settings is a good solution for the English speakers.