Inversion Recovery Pulse Sequences MRI | STIR and FLAIR | MRI Physics Course #19
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- Опубликовано: 26 сен 2023
- High yield radiology physics past paper questions with video answers
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Having reviewed spin echo and gradient echo pulse sequences, let's turn our attention to inversion recovery pulse sequences. Inversion recovery sequences serve to null signal coming from tissues with a predetermined T1 relaxation constant.
A 180 degree radiofrequency pulse the net magnetisation vector into the antiparallel longitudinal plane. Once the RF pulse is switched off the spins will regain longitudinal magnetisation at different rates (depending on the T1 of the tissue). At certain intervals specific tissue will have a net zero longitudinal magnetisation. If a 90 degree radiofrequency pulse is applied at this interval (time of inversion) there will be no signal in the transverse plane from that particular tissue.
This is the basis for signal suppression in inversion recovery pulse sequences.
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Not sure if the question banks are for you?
If you're here, you're likely studying for a radiology physics exam. I've spent the last few months collating past papers from multiple different countries selecting the most commonly asked questions. You'll be surprised how often questions repeat themselves!
The types of questions asked in FRCR, RANZCR AIT, ARRT, FC Rad Diag (SA), ABR qualifying Core Physics and MICR part 1 are surprisingly similar and the key concepts remain the same throughout. I've taken the most high-yield questions and answered them in video format so that I can take you through why certain answers are correct and others are not.
Happy studying,
Michael
#radiology #radres #FOAMrad #FOAMed
Incredible video. Thank you very much.
Thank you so much for the excellent lectures! Can you also cover spin lock, T1rho relaxation, and adiabatic concepts?
Fantastic content! Thank you from Sweden!
Thanks @isasacic2917! Love knowing where everyone is from 🥰
These lectures are so concise and easy to understand. Thank you.
This makes me so happy! Thank you. I’m really trying to make it as simple as possible. Glad it’s been helpful 🙂
Great, Amazing talk. Thank you very much..
So glad you enjoyed it!
Thanks Michael 👏
شكرا للشرح
Bravo!
I've been trying to understand the mechanism of action surrounding the null point in the IR sequence. And I've been trying to reconcile the quantum mechanic principle of basically having no way to know where something is in space, with the magnetic vector that can be predicted due to accumulation of many protons in their predicted state. It's helped me realize that the transverse magnetic vector is a result of the stimulated coherent precession, and that without stimulation from the RF pulse, there is no coherence. Which means T1 recovery, by nature, isn't coherent recovery, so the magnetic vector doesn't "swing back" through the transverse plane. So my question is, if my previous statements are correct and apply, is the null point essentially the quantum mechanical point in time where we have no way of predicting where the spins are, because they are, in that moment, not influenced by any external forces? And thus there is a net zero magnetic vector? Or is there a magnetic vector that still exists but no component of it exists in the longitudinal plane? Thanks in advance for your time with my questions!
Amazing lectures through and through! I might be mistaken here, but at the 9:00 mark, didn't you mean to mention longitudinal instead of transverse?
One of thae important topics 🙏
Thank you sir always great explanation ❤
Thanks for your support 🤗
Thankyou❤❤
Thank you!
Thank you for watching 😀
Superb lecture, thanks a lot 🎉
Cheers Fazal 👍🏼🙏🏻
@@radiologytutorials ❤️
Thankyou micheal sir
There is one small mistake at around 9 min you said when we apply 90 RF pulse we are going to loose all trans mag but we lost long mag.
Thank you for your amazing videos. I don't understand one thing though - for the STIR and FLAIR sequences you have images with TR at 90. Shouldn't the new repetition start with 180 again?
180 is just an extra inversion pulse we're using.
90 degree is the excitation RF pulse, therefore the TR is counted only from 1 excitation pulse to the next, not 1 inversion pulse to next
Please release MRI question banks
Thankyou 🎉🎉
You’re welcome 😊
Honourable sir Need Computed tomography physics lectures also. Thanks in Advance Sir
Hi @mohsinshehzad4031- I'm working on finishing the MRI series at the moment, but hopefully CT is not too far behind!
12:32 I´ve got a question:
In order to get the 180° flip angle (,so minus 100% the initial longitudinal magnetization), don´t we pretty much push all the spins to a spin down state? Wouldn´t that mean that we can´t go any further than 180° from that point? I mean, flipping a certain tissue from 180° back into the transverse plain would basically mean that we push that tissue further from 180°, 270° around. But in order to do that, we´d need to excite more than all of the spins which is obviously impossible. Only way I can think of is that we excite the tissue in such a manner that we push the spins of the tissue in question out of the spin down phase by starting a pulse that would be absorbed by spin down atoms, but in order to conserve the energy they´d have to give up energy (which will probably result in heating up the surrounding body parts). So, we excite spin down state atoms further and as far as I know, that is impossible (other wise , fat sat wouldn´t work). How can we flip spins from 180° back into the transverse plane?
I mean it´s being done so there must be a way to do that, but I don´t really understand how bc from my current physical perspective that should be impossible bc of the aforementioned reasons...
Mister, Are u still there? Have u had the answers yet?
@@vohuynhminhtuanvng Still here, still no idea
...
No rhyme intended
@@yrusb do you have any means for communication such as facebook or telegram?? We have the same interest in principle of MRI, this makes me delighted
@@yrusb In my point of view, Disparity between Spin up and spin down state will determine the amount of signal that could be caught by Receiver coil. The 180° pulse will push all this spin (residual amount of the subtraction between spin-up and spin-down) into the negative -z axis. Simarily, the 90° pulse will cause the equality between this two state. This also lead me stuck deeply into another problem. The pulse that further than 180° will cause more change of amount of each state or else.
@@vohuynhminhtuanvng Hey sorry for answering so late, I had a million things going on in the past few weeks but things will hopefully be a little bit calmer for now
If you still want to, we can exchange e-mail addresses first and then we can exchange phone numbers and communicate via signal or find another mean to communicate 😊I just don´t want to post my phone number in public
(Just to avoid confusion as for when I´m actually online and since you´re probably from the US - I´m from Germany and hence probably in another time zone)
Thankyou❤❤