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| Result: Searchterm 'Amplitude'
found in 3 messages |
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Donna Nusser
Tue. 18 Aug.09,
19:17
[Start of:
'MRI registry equations'
20 Replies]
 Category:
Basics and Physics
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| MRI registry equations |
I'm studying for the registry with the help of the MIC registry review program. I think my mind has turned to mush. I can not figure out the answer to this question or find an equation to help me. Is there anyone out there who can help?!!
"In an ideal 1.0T magnet with perfect homogeneity, if a proton experiences a magnetic field of 1.006T and is positioned 0.5 meter along the positive z-direction and centered along the x and y directions, the z-gradient amplitude is________mT/m."
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Jennifer Jackson
Fri. 21 Jul.06,
04:44
[Reply (1 of 2) to:
'Phase encoding'
started by: 'guillaume bierry'
on Fri. 7 Jul.06]
Category:
General
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| Phase encoding |
Wow this is a long subject, First you have to under stand how the 3 main gradients are used. (slice select, Freq, then phase)
So you are use 1 of the gradients for your phase encoding. You need to fill the k-space which depends on you matrix. Lets assume you are using 256 (phase). In order to fill K-space you have to have 256 aquistions of the signal. Meaning for each picture (or slice) the signal must be acquire(sampled) 256 times each at a differnt amplitude to put it in a different Line of k-space.
Example- If you are performing a SE(spin echo) you have 1 TR period and 1 TE period (TE=is when the signal is sampled) so you will have to do the TR period 256 times to fill K-space with diffent amplitudes.
There is alot more that I left out. If this did not answer your question let me know
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Rud Spring
Fri. 7 Apr.06,
21:02
[Reply (1 of 2) to:
'Slew Rate'
started by: 'Reader Mail '
on Sun. 2 Apr.06]
Category:
Sequences and Imaging Parameters
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| Slew Rate |
It's about how fast the gradient coil reaches the amplitude. It's the steepness of the curve. The time it takes to reach this amplitude is often referred to as "rise time".
At certain high slew rates the gradient switching is so fast that peripheral nerves get stimulated. A warning may be given like "possible peripheral nerve stimulation". It's not really dangerous, but you can feel your muscles contract a little. Some people are more sensitive to it than others.
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