Introducing MRI: Introduction to NMR - Nuclear Magnetism (3 of 56)
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- čas přidán 22. 07. 2024
- www.einstein.yu.edu - The third chapter of Dr. Michael Lipton's MRI course covers introduction to NMR - Nuclear Magnetism. 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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• The number of spins in each energy level can be predicted by
the Boltzmann distribution (Table 3.1 ).
• In thermal equilibrium, at any moment there are a greater
the proportion of spins with their magnetic moments aligned with
the field than against it. This excess aligned with B 0 produces a
the net magnetic effect called the NMV that aligns with the main
magnetic field
Confusing word: "aligned". There are all aligned, but anti-parallel beats parallel in an extern field B.
I had the impression that under external magnetic field slightly more protons are arranged parallel than antiparallel to the direction of field,that is more protons are in low energy state and hence align parallel
lol india
20:20 he has it backward, the net magnetization at equilibrium is along the Z axis Bo.
Yeah, I also think so. It should be along the B
Dr. Lipton mentions notes and book at 5:42. Does anyone know what book he is referring to? Or any sources for the notes??
In precence of external magnetic field the NMV along itself along the external magnetic field. It the other way around in what you said
5:46 Does anybody know the booklet or notes they are referring to?
Forces are balanced in both parallel and anti parallel orientation of the magnetic dipoles. However the potential energy is higher in the anti parallel state such That even a slight deflection in the presence of the ext magnetic field wud lead them to align in the lowest energy state I.e parallel
For everyone in doubt about the statement of parallel vs antiparallel alignment, go to Chapter 5 and look in the comment section, Dr Lipton has answered this himself.
Which book are you referring to?
@@Angela-pg6wn I think he is referring to the numbering of the video. Since this is 3, it is chapter 3. He says we need to go to chapter 5. so, video 5.
hellium3 does in fact have a spin of 1/2 and is used in MR
#weekend4
thank you Dr. Lipton
20.40... NMV parallel to the B0 not opposite
4:55 NOT equal, should say EVEN.
11:34 It should be MAGNETIC MOMENT not magnetic field, MM is a vector located at the prnton, mf is a field with vectors all over the space.
20:07 Same mistake, the total MGNETIC MOMENT is PARAREL ( not ANTi) to the applied strong external magnetic field.
Carca Peru wht difference between magnetic moment and magnetic field please
What is dipole moment and momentum
god thanks dude
Please can someone give me the notes which he recommended
This is excellent
Is there somewhere that Dr. Lipton has answered questions that are brought up in reference to his videos? I am just beginning an MRI program so have only a small amount of knowledge on the subject. But, it was my understanding that, when placed in an external magnetic field the Net Magnetic Vector should align parallel, not anti-parallel, to that external field. That there are more spins that are influenced by the field than spins that are strong enough to resist it and not turn parallel.
Hi there, I had the same question after the video, then I started reading his book and there he says that once exposed to the MF, some spins are alligned parallel and some antiparallel, but by antiparallel he means "parallel but pointing in an opposite direction" . It's confusing. Have you found any other information?
this is really good, thank you!
I understand that the magnetisation vector is not actually created by the movement of charge in the nucleus and what we see in textbooks is an easy representation of what happens but, can someone please explain to me (or send me some references) what really creates the magnetisation and its orientation? I dug deep into my old quantum mechanics books but wasn't able to find a satisfactory explanation.
In a nutshell, positive electron spin around the proton creates a moving electrical charge, which in turn induces magnetic force.
en.wikipedia.org/wiki/Nuclear_magnetic_resonance#Spin_behavior_in_a_magnetic_field
I agree with @Carca Peru it should be more magnetic moment in parallel to the main external magnetic field.
Please let me know if I'm understanding it correctly. The NMV is aligned anti-parallel to B0 until B1 comes in and flip it parallel the B0 then we watch the FID?
I think the confusion is between the words parallel and antiparallel. In his examples, parallel and anti parallel are both in the z plane (B0, longitudinal), but pointing in opposite directions (ie, z+ and z-). With the RF pulse, the protons are flipped orthogonally (transverse, B1).
In reality, when a magnet is brought to another magnet, naturally they will change their direction in a manner so that opposite poles are closer too each other.
Then why in an externally applied magnetic field, some protons go parallel, some anti-parallel? I mean, why not all the protons are arranged in a manner that will bring opposite charges closer?
Ratio of parallel/antiparallel goverened by boltzmann distribution N+/N-=exp(energy difference/ kbT ), where kbt is boltmann constant * temperature in Kelvin
According to boltzmann distribution, room temperature (300K) difference of parallel and anti parallel is on the order of 0.5 ppm (0.5 more parallel than anti parallel per million spins) at 1.5T.
Thermal collisions equalize high and low energy states.
Same question
4:55 except deuterium
Why the net magnetic vector is antiparallel to external magnetic field? I have alwsys been taught it is parallel. Plz forgive me my English.
You're right and he's wrong ...because actually parallel state correspond to low energy and antiparallel to the heigh one. So the net vector has to be parallel (low energy) in stable state to move then to high energy(anti parallel) when we excite it . Sorry for my English too.
I see that in most countries they work 8
hours a day or 40 hours a week, in my country is 6 hours a day or 30 hours a week, and you can work 12 hours a day but then you have more rest days.
My question is why do they work 40 hours in a week?
They try to do it in our country too, the reason is newer devices have less radiation.
And then someone is released from work because of radiation, we cannot give blood because we are in the radiation zone, etc.
very slow
Several months later and my understanding is still the same. Net magnetic vector is parallel not anti parallel. Either I don’t understand this correctly or Dr. Lipton has confused what appears to be a very simple concept???? Makes me wonder what else he has confused in his videos?