Really nice presentation! Thank you a lot especially for the good examples and visalizations. I found it very helpful to see what happens in the spatial space when the k-space is blacked out at different degrees! All the best
MRI signal is the xy component of the magnetization. The magnitude is the length of the xy component, while the phase is the direction of the xy component. Let's take gray matter and CSF as an example. When you apply an excitation RF and wait the same amount of time (TE) to acquire the signals, CSF will have a higher signal magnitude than GM because of slower T2 relaxation. However, the directions of the magnetization (phase) of GM and CSF should be the same because the spins were tipped to the same direction by the same RF and have the same angular velocity due to same B0. So, ideally, you should observe intensity variation in magnitude but not in phase. However, there are always imperfections, including B0 offset, inaccuracy of readout time, susceptibility, etc..., which cause the intensity variation in phase. Some MR technologies create intensity variation in phase on purpose, such as phase contrast MRA which allows flowing spins accumulate phases by applying a bipolar gradients along the direction of the flow. This is an interesting topic, and hope my response is helpful for you.
@@chenyangzhao247 thank you for your answer. I have many questions in image reconstruction that well be very nice if u can answer me :) 1- why an FFT shift needs to be carried out on k-space before and after the iFFT is applied. What is the purpose of the FFT shift? 2- Where are low-frequency components located in k-space? 3-What happens if you only apply the FFT shift before, but not after performing the iFFT on the k-space
By far the most clear explanation I've seen. Wonderful animations. Thanks!!
You explained it very clearly and it really helped me a lot.Thank you!
Absolutely incredible explanation. Thank you!
This was the best explanation I have seen. Great work!
Really nice presentation! Thank you a lot especially for the good examples and visalizations. I found it very helpful to see what happens in the spatial space when the k-space is blacked out at different degrees! All the best
Really nice video. Thank you very much! I love this summation-fragment: 6:29.
Simple explanation for a complex topic, thanks
THANK you so much for your great presentation
Very helpful video!! thank you for sharing
great video ... many thanks
Thank you for the excellent video lecture. I have shared it with my students.
Thank you for this excellent explanation! Great!
defintely the best presentaiton I've ever seem in this topic. The visualizations are super clear and easy to grasp. Thank you so much
Wonderful explanation! Thanks!
Great explanation
masterfully related. a true teacher. thank you.
Brilliant explanation, thanks!
Thanks
Very helpful, thank you!
Good explanation!
Thank you! This is really great and helpful.
fantastic!
Thanks for this vedio!
thank you.
Can you elaborate on why the phase does not show the same intensity variation as the magnitude
MRI signal is the xy component of the magnetization. The magnitude is the length of the xy component, while the phase is the direction of the xy component. Let's take gray matter and CSF as an example. When you apply an excitation RF and wait the same amount of time (TE) to acquire the signals, CSF will have a higher signal magnitude than GM because of slower T2 relaxation. However, the directions of the magnetization (phase) of GM and CSF should be the same because the spins were tipped to the same direction by the same RF and have the same angular velocity due to same B0. So, ideally, you should observe intensity variation in magnitude but not in phase. However, there are always imperfections, including B0 offset, inaccuracy of readout time, susceptibility, etc..., which cause the intensity variation in phase. Some MR technologies create intensity variation in phase on purpose, such as phase contrast MRA which allows flowing spins accumulate phases by applying a bipolar gradients along the direction of the flow. This is an interesting topic, and hope my response is helpful for you.
@@chenyangzhao247 thank you for your answer.
I have many questions in image reconstruction
that well be very nice if u can answer me :)
1- why an FFT shift needs to be carried out on k-space before and after the iFFT is applied. What is the purpose of the FFT shift?
2- Where are low-frequency components located in k-space?
3-What happens if you only apply the FFT shift before, but not after performing the iFFT on the k-space
Is there anyone working on k space and codings ???
Thanks really good video
hell yeah
这个口音比老外的好懂多了
ok video, audio sucks. Has reverb or echo in it that makes it harder to understand. Sounds like it went through a low pass filter.