Introducing MRI: The Spin Echo (15 of 56)

[@30dthomas30]

The speaker is a fantastic educator. Dr. Lipton truly has a gift for distilling complicated content into more easily digestible doses.

[@QuantumWithAnna]

Yeah his presentation is brilliant and his grasp of physics is spot on.

[@thomasboisson5429]

The MRI speech is dephasing with the video. Relaxation?

[@RudradeepMukherjee]

Why do we need to keep the RF pulse for twice as long? Even with one RF pulse with spins at 90% from the longitudinal, the signal with (higher precession frequency) will phase-in and phase-out with the other signal. RF applied for twice as long creates a kind of mirror-image of the former scenario. (Sorry for not being strict and technical with words.)

[@mickeysingh7443]

Did you get the answer may be the 180degree pulse aligns them because coherence is mainly produced by energy the more time we give B1 more put energy into system to align the incoherence produced by sucusceptibility (this is the only reason I could give to myself in order to digest it ,don't worry it's quantum physics we will never understand just admire from a safe distance)

[@Thefuture_robloxyoutuber.]

I think at 13:58 should be "what you need to do is measure both T2* and T2 and compute the difference. The discussion is how to measure T2'.

[@h.q.1736]

In gradient echo image why don’t we use even a shorter TE to get a better contrast And thank you very much for the great lectures

[@HaopengHan]

Since there can be variations of Larmor frequency among spins, which lead to different precession velocity, how can they end up in the same transverse plan at the same time after the 90-degree pulse? The dephasing should be always there, rignt?

[@deliaacsinte4092]

It's because the RF pulse doesn't only have ONE frequency, it has an array of multiple frequencies (called bandwidth), so that every spin with a frequency in that array gets to resonate; everybody's a winner. :)

[@huibread5604]

Why there is decrease in amplitude in Spin Echo? In other words, why the transverse magnetization is not the same amplitude as that after 90 degree RF?

[@HaopengHan]

I think that is because when you apply the 180-degree pulse, there is already some relaxation, both longitudinal and transverse. The second pulse flips over what's there including the Mz.

[@josheii]

You cannot grow higher than T2 curve.

[@maryamali8847]

Anyone describe the process shortly plz

[@abdovitamins6331]

شاهدي ڤيديوهات المهندس عمرو الغراب شارح دروس الرنين بالعربية أكثر من رائعة ، وصدقيني مش هتندمي بدل العك ده ، الرابط اهو kzbin.info/www/bejne/emKsdHeha8-eidk

[@AaBb-xh9ds]

I have couple of questions First I understand why spins or protons dephase because protons are alike charge and they rebel each others is that only reason why they dephase And what it have to do with giving more amount of energy so the spins stick with each others Second one why he said 90 degree than 180 degree why not 270 degrees is that not 270 degress Also one last question which is more important How two spins with different frequencies be inphase and why they behave this way after giving em 180 degree pulse they become inphase why they behave this way please someone explain im pay 100 dollars for my questions answered

[@rubenvandenbroek9689]

to answer your last question: You need the spins to dephase a bit. That's why you apply the 90 degrees RF pulse, wait a bit and then apply the 180 degrees. If you would apply 270 straight away, the spins would not be able to dephase. Applying 270 without waiting is essentially the same as just a 90 degrees RF pulse, only with a negative sign. the ''wait a bit'' part is essential, that's the Echo time.

[@clydez1234]

Okay this was not good.. these are going downhill lol poor explanation