The greatest video series I've ever seen. Your animations and eloquent explanations are out of this world! If you happen to make a follow-up, I'd love to see discussions of fMRI and BOLD analysis, since these are my areas of application. Cheers!
I don't quite understand how flip angles beyond 180° could work. If the flip angle just shows how many spins are flipped to another energy state then after 90° (equilibrium) and 180° (surplus in the antiparallell direction) how could the system then change to even higher energy states? Just larger longitudinal magnetization in the -180° direction? Also if the b1 is pointing perpendicular to b0 and M aligns 90° to that in the transverse plane, how would it then suddenly spin futher to 180°?
I attempted the questions kindly correct me if I'm wrong. Pinging @thepirl903 1.a) Bolzmann units-J*T^-1*m^-3. b)Polarization units- non(it's essentially a ratio) 2. a)B0=5873T b)T=0.05108K (looks wrong but works I guess) 3.a) Sample B b) Sample B(though the question is somewhat contradictory) c) T2=13.458ms (if working with MoA=0.7MoB) 4.TE=7.699ms 5. a)S(t)=0.5488mV b)S(t)=0.1530mV c)tau1=20ms tau2=60s d)S(t)1=0.4493mV S(t)2=0.2019mV 6. 13 echoes? Just finished the tetralogy, great insight. Watching for a second time being more keen on the math. Keep up the good work!
This is incredible. I study pure and applied mathematics but also enjoy physics and any other field that studies a complex system. This video and explanation is so well done. Thank you.
You are a legend! I just started my new job as an MRI data analyst, and I absolutely love your videos-they're amazing! I’m currently creating an onboarding document for future employees and students in our group, and your videos will be at the top of the list for everyone to learn MRI easily. Thank you, thank you so much for creating such awesome content!
Would it be correct to say that M(x,y) is, in reality, a function of time due to the ensuing transverse magnetization relaxation process? How does this alter the formulation of the fourier transform application?
Indeed M(x,y) is a complex function of time. Our model for the GRE here assumes that M(x,y) is static. This of course isn't true, but on the time scale of a readout, these effects can generally be safely ignored if the readout is quick and T2* is long (not always the case, but fair for most biologic tissues). Similar to taking a photograph, we find a balance between our subject's motion (analogous to T2* decay) and the camera shutter speed (analogous to readout time) to reproduce the best 'snapshot' of M(x,y). Hope that helps
I studied electrical engineering and am now doing a phd in RF analog electronics. The 3rd and 4th videos of this series give an idea of some of the math I encountered in my studies. Before encountering this video I wasn't aware of the connection between MRI and RF technology. I'll have to check out some research on the transmitter and receiver section of MRIs.
Could you please clarify whether or not the net magnetization vector should be visualized as a precessing vector @1:35? My understanding of NMR is that this is NOT true (because all of the x-y components of the magnetic moments of all individual nuclei effectively cancel out)...and if there is no net magnetic moment in the x-y plane, then all of the net magnetism is directed along the z-axis, which means the torque from the perspective of the net magnetic moment vector is 0 (i.e. no precession about the z-axis). However, you seem to suggest that this is the case with your language: "collectively, the quadrillion of spins in space sum to a nuclear magnetization vector M..." and then you provide a picture of this presumed net magnetization vector M (purple arrow) and depict it as precessing. Isn't this incorrect?
You make a good point! I should've made it clearer in the video, but when the M and B vector animation appears it is immediately following excitation, not in equilibrium. You are certainly correct that in equilibrium, M would be stationary pointing in the z direction and no precession would be apparent. An rf pulse (which I didn't show) is necessary to tip M away from B and see precession. Thanks for this observation; comments like this are helpful so I can see where gaps exist in my presentation! Cheers
I am a postgraduate Physics Student and I had some troubles with the textbook explanations and this really made my day. You made it look so easy, it's incredible. Thanks.
That pile of quantum physics, mathematics and who-knows-how-many-other-fields is so insanely cool, it made me freakin' smile... Thanks a lot for doing such a huge work! It is especially valuable, because primary audience here is very narrow and there kinda no stimulus other than authors own interest and respect for beauty of subject!
To better understand the Spin-Echo technique in MRI, you can watch the following videos which provide visual explanations of the process: 1. [Fast Spin Echo - Spaces Animation](ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-RI-YtEBcHkc.html) - This video offers an animation that helps visualize the fast spin-echo process in MRI. 2. [How MRI Works - Part 2 - The Spin Echo](ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-M7yh0To6Wbs.html) - This video explains the spin-echo sequence, detailing the 90° and 180° RF pulses and how they work to create the MRI image. These videos will help you see how the protons in the body are manipulated by the MRI machine to produce detailed images through the spin-echo sequence.
Such a complex topic understood by Phd students, this is one of the best presentation explaining the maths relating to quantum mechanics. As a radio communication technician has extended further knowledge into the atomic world. Subscribed and liked.
Excellent presentstion! Thank you fir insughtful dilligence. Pleasexdo axsegemnt in the elecyronics and relsted base software to collect and cinvert the raw dataxand cinvert to image data. Details of ADC sample frequency, how RF frequencies are shifted (mixers), RF PA, LNA and related filters. And maybe post a biography on yourself.
19:35 But the omegas arent the same for all atoms otherwise they wouldnt dephase so a rotating frame is just the average omega0 and the linewidth of the omega spec is just giving the decay time of the frequency that is still omega0. So to even think about a rotating frame is still making sense?
38:15 Note: The Nyquist frequency is as stated in 52:45 is half of the Sampling frequency \omega_s. Thus the total frequency space will vary between (- \omega_s/2) to (+ \omega_s/2). Where \omega_s = Sampling Frequency.
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
Best videos. Have watched this video 6 times by now. I am starting to get it. The maths part between 30-45 minutes needs some work from me to fully get.
I am here because my son is in MRI ! At a university. So, to understand his passion . I'm learning from these videos. The language and understanding of MRI. Thank you . 🎉
