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| Result: Searchterm 'Echo'
found in 43 messages |
| Result Pages: 1 2 [3] 4 5 6 7 8 9 |
More Results:  Database (305) News Service (7) Resources (10) |
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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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John Smith
Wed. 11 Nov.15,
22:14
[Start of:
'Faster pulse sequences'
0 Reply]
Category:
General
|
| Faster pulse sequences |
Hi,
I have been learning about faster MRI sequences and have two questions
1) With "Fast (Turbo) gradient echo", in which we apply a spoiler gradient, do we not eventually end up with no longitudinal magnetization because TR is always shorter than T1? Hence shouldn't we eventually get no signal at all?
2) in SSFP (Steady-state free precession) we can apply an RF pulse of 90 degrees (in which T1>>T2) to get heart-blood contrast. How is this any different to a standard spin-echo sequence in terms of timing?
Thank you
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aaron yonts`
Thu. 19 Sep.13,
07:56
[Reply (1 of 3) to:
'why there is T2* but not T1*'
started by: 'Isa Toni Toni'
on Wed. 24 Jul.13]
Category:
Sequences and Imaging Parameters
|
| why there is T2* but not T1* |
i may just be giving general info but a t2* is aquired from a gradient echo compared to a t2 with a spin echo. according to mri in practice a t2* can help show some things a normal t2 would not, such as ms plaques in a cervical spine
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Reader Mail
Wed. 1 Jun.11,
14:14
[Start of:
'Dixon technique'
1 Reply]
Category:
Sequences and Imaging Parameters
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| Dixon technique |
I have been searching the web for information regarding a "double-echo two-excitation pulse sequence encoding fat and water signals for a phase-sensitive three-point Dixon type analysis". Does anyone know what pulse sequence(s) this is referring to, or a publication that might be helpful???
Thanks
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Elise Gough
Mon. 7 Mar.11,
16:54
[Reply (7 of 8) to:
'6-1.5T MAGNETS, DIFFERING GRADIENTS'
started by: 'Elise Gough'
on Wed. 23 Feb.11]
Category:
Applications and Examinations
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| 6-1.5T MAGNETS, DIFFERING GRADIENTS |
Thank you for your logical advice. Just spoke with GE apps. "No amount of messing with MR parameters can compensate for weak gradients. Increased gradient strength=decreased echo spacing=less blurring". Coincidently, my DO just emailed me asking what the gradient strength is on the magnet the RADs are complaining about.Just MAYBE they'll upgrade it. I need to visit our sites.The only way I have to check other sites' parameters is importing exams from PACS to my modality console. Tedious, but telling. Again, thankyou for all the help.
Elise Gough RT(R)(CT)(MR)
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