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| Result: Searchterm 'SAR'
found in 22 messages |
| Result Pages: [1] 2 3 4 5 |
More Results:  Database (62) News Service (34) Resources (14) |
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Clifford Thornton
Thu. 30 Jun.16,
17:48
[Start of:
'Max. SAR per second - Whole Body (Normal, 1st Controlled, 2nd Control)'
0 Reply]
 Category:
Safety
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| Max. SAR per second - Whole Body (Normal, 1st Controlled, 2nd Control) |
Hello fellow imaging technologists & professionals!
I'm involved in the development of a new type of cardiovascular medical device.
This device employs MRI technology/scans to power, guide, and control the medical devices and their active elements.
I conducted some research into the following question, "How much x-ray energy is allowed within a human every sec from a MRI machine?"
With regards to SAR rates, I understand that these are the upper-limits for the various settings for a full-body scan:
Normal setting: Whole body SAR - 2
1st Level Controlled: Whole body SAR - 4
2nd Level Controlled: Whole body SAR - >4
Would you agree with these calculations that I performed, and if not, why? And what would be a better way to calculate this?
For WHOLE BODY SAR:
-SO IF IN NORMAL MODE FOR MRI, THE MAX. ALLOWABLE SAR IS "2" OVER A 6 MIN. PERIOD, THEN
-6 MIN. = 360 SECONDS
-2 / 360 = 0.00555
FOR 1ST LEVEL CONTROLLED:
-SO IF IN 1ST LEVEL CONTROLLED FOR MRI, THE MAX. ALLOWABLE SAR IS "4" OVER A 6 MIN. PERIOD, THEN
-6 MIN. = 360 SECONDS
-4/ 360 = 0.01111
Other questions -- What is the difference between normal setting, 1st conrolled and 2nd controlled?
What is the clinical purpose of these various settings?
Any insights that you would be willing to share in regards to the above would be greatly appreciated!
I was trained and registred as a diagnostic echocardiographer, specializing in cardiovascular ultrasound, therefore I need help with MRI information/specifications. I am now focusing on the medical device field, but this technology/device happens to be highly dependent on MRI technology.
Any help from the group would be greatly appreciated!!
Thanks & regards,
Clifford Thornton
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Jason Gordon
Wed. 13 Apr.16,
14:17
[Start of:
'Est. SAR vs. Peak SAR?'
0 Reply]
Category:
General
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| Est. SAR vs. Peak SAR? |
If an implant is MR Conditional with a manufacturer's recommendation that SAR be kept less than or equal to 2.0W/kg, does that mean that I should be looking at the Est. SAR or the Peak SAR and keeping it under 2.0W/kg?
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I L
Wed. 12 Oct.05,
22:52
[Start of:
'SAR, Magnetic field and exitation frequency'
1 Reply]
Category:
Basics and Physics
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| SAR, Magnetic field and exitation frequency |
Could you give me the relation between the SAR and the exitation frequency for a given magnetic field ?
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abdoulaye sarr
Sat. 28 Sep.19,
09:38
[Reply (24 of 26) to:
'MRI Technologists Jobs in Saudi Arabia'
started by: 'Mosta Mosta'
on Tue. 3 Mar.09]
Category:
Jobs
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| MRI Technologists Jobs in Saudi Arabia |
Hello there
Are you still looking for an MRI technologist?
Im currently working at the University of Washington Medicine and looking for an overseas MRI job.
best regards,
asarr
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Math G
Fri. 30 Jun.17,
21:02
[Reply (10 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 |
I will try an answer to this rather old tread, in case someone stumble upon this like me.
The phenomenon of "coherence" that produce transverse magnetization after a 90 RF pulse cannot be answered by classical mechanics, or any simple model that represents individual protons as precessing magnets in either the parallel/antiparallel direction with regards to the MRI magnetic field.
Rather, it is a phenomenon related to quantum mechanics and the effect of a RF field on a interacting group of particles with spins (not necessarily oriented as parallel/antiparallel, I might add, even under the effect of a magnetic field).
The simplest depiction, as I understand, would be to imagine a group of spins as literally rotating as a whole under the effect of the RF. After a certain time (corresponding to a 90 degree pulse), the net magnetization that was oriented parallel to the MRI magnetic field, is now oriented in the transverse plane, causing transverse magnetization and signal. If you further apply RF, the system will continue to rotate, shifting gradually toward an antiparralel orientation, losing transverse magnetization in the process.
Hope its clearer!
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