Magnetic Resonance - Technology Information Portal Welcome to MRI Technology
Info
  Sheets

Out-
      side
 

Next big thing in MRI will be :
AI 
remote operator 
personalized protocols 
helium-free 
molecular MRI 
portable MRI 




 
MRI Forum
'In Phase'
SEARCH FORUM FOR   
 
Result: Searchterm 'In Phase' found in 6 messages
Result Pages: [1] 2 
More Results: Database  (25)  News Service  (25)  Resources  (10)  
Forum Overview
 bottom
Desiree Dupuy

Sat. 3 Dec.16,
22:14

[Reply (2 of 3) to:
'Muscle shading in 3T Images'
started by: 'Travis Conley'
on Thu. 21 Oct.10]


 
  Category: 
Applications and Examinations

 
Muscle shading in 3T Images
Try running a B1 Map followed by Calibration. Set RF Drive mode to Optimized. This is supposed to optimize for your Patient. Supposed to reduce dielectric effect/shading for Lumbar and Abdomen.
You can find under GE Additional Abdomen Sequences.

Or you can run Ideal with Dixon technique. Turn on IN phase will give you T1 FS & IN Phase is you plane T1. I believe this takes care of the artifact.
 View the whole thread
shahrokh Rad

Sat. 4 Oct.14,
13:44

[Reply (9 of 12) to:
'90 excitation pulse vs 180 inversion pulse'
started by: 'Bjorn Redfors'
on Sat. 27 Jun.09]


 
  Category: 
Basics and Physics

 
90 excitation pulse vs 180 inversion pulse
All of the responds are misleading.
what is the correct answer??????
why does the 90 excitation pulse result in phase coherence while the 180 pulse won't.
 View the whole thread
Oliver Lyttelton

Mon. 1 Mar.10,
13:39

[Reply (8 of 12) to:
'90 excitation pulse vs 180 inversion pulse'
started by: 'Bjorn Redfors'
on Sat. 27 Jun.09]


 
  Category: 
Basics and Physics

 
90 excitation pulse vs 180 inversion pulse
Okay, so this thread is answering close to a question I had, which is how to conceptually understand what happens with alpha>90 degrees excitation pulses.
I can imagine spinning tops, precessing at the Larmor frequency, I can imagine that as you apply the excitation pulse which is always in the transverse plane to the main magnet, you start to pull the tops further away from the B0 axis and bring them into coherence so like lots of little lighthouses they are all bright/dark in phase with each other. I can imagine a 90 degree pulse bring the spins completely into the transverse plane. I can imagine them relaxing, dephasing quickly and then slowly reducing their angle of precession back up towards initial state close to direction B0.

But what I can't understand in my (rather newtonian) model, is what happens as you continue to excite beyond the 90 degree transverse plane. I sort of get that somehow the spins continue to rotate in some (weird) dimension, and that they have to come back through that (weird) dimension first before returning from 90 degrees back to the relaxed state. But what happens in "weird" dimension is beyond my conceptual model. Can someone extend my model for me, preferrably without signal equations?

tar muchly,

Oliver
 View the whole thread
Pim vanOoij

Fri. 27 Feb.09,
15:27

[Start of:
'PCA aliasing problem'
2 Replies]


 
  Category: 
Artifacts

 
PCA aliasing problem
Hi everyone,

Has anybody who reads this ever encountered aliasing in phase contrast measurements in pixels where velocity did not exceed Venc? If so, could this be due to signal leakage of surrounding vessels? Thanks for your help!

Pim
 View the whole threadReply to this thread
(login or register first)
Sam Shelly

Sun. 2 Nov.08,
23:02

[Reply (2 of 3) to:
'Regarding recovery and decay [basic phycisc]'
started by: 'harry sanders'
on Sat. 7 Jun.08]


 
  Category: 
Basics and Physics

 
Regarding recovery and decay [basic phycisc]
Right on.

Recovery and delay are two separate physical processes like the last guy said. It had me stumped for a while when I was studying as well. But read carefully and think hard about it...

T1 recovery is the return of net magnetization into alignment with b0.

T2 decay is a totally different process and is, as the previous person said, simply loss of net magnetization in the transverse plain due to dephasing. The more electrons that are precessing in phase in the transverse plane, the stronger the NMV is in that plane. And, hence forth, when the RF pulse terminates, the influence of b0 gradually dephases the electrons in the transverse plane. As they dephase, the transverse NMV decreases accordingly, until the next pulse hits, rephasing the electrons and starting the process all over.

Hope that helps. MRI physics is hairy and boring at times. Load up on expressos to stay awake and stick with it, because studying MRI physics can be like taking a bottle of sleeping pills.
 View the whole thread

Result Pages : [1] 2 
 top
 
Share This Page
FacebookTwitterLinkedIn

MR-TIP    
Community   
User
Pass
Forgot your UserID/Password ?    



Look
      Ups






MR-TIP.com uses cookies! By browsing MR-TIP.com, you agree to our use of cookies.

Magnetic Resonance - Technology Information Portal
Member of SoftWays' Medical Imaging Group - MR-TIP • Radiology-TIP • Medical-Ultrasound-Imaging • 
Copyright © 2003 - 2024 SoftWays. All rights reserved. [ 22 December 2024]
Terms of Use | Privacy Policy | Advertising
 [last update: 2024-02-26 03:41:00]