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| Result: Searchterm 'Power'
found in 18 messages |
| Result Pages: [1] 2 3 4 |
More Results:  Database (102) News Service (80) Resources (12) |
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Don Monterez
Mon. 27 Sep.04,
01:44
[Start of:
'Power Injector'
1 Reply]
 Category:
Equipment
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| Power Injector |
Hi,
we look for an easy to handle, service friendly and cheap power injector for MRA. Can someone recommend us one. Any good experience?
Thanks Don
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Eduardo Mendes
Tue. 19 Jul.16,
12:59
[Start of:
'Need to quench a scanner now'
2 Replies]
Category:
General
|
| Need to quench a scanner now |
HellornrnI have on old Oxford 4.7 T scanner that has been working since 2011. Unfortunately these last few days we could not transfer He in. Although our He liquefier is completely full and the transfer line is connect to the magnet, no He is transferred. The transfer line has been made vacuo efficient two months ago and should be ok. rnrnIt seems that we need to quench the magnet. We don't have any external power supply to connect to the magnet and retrieve the current. rnrnWhat can we do? Is there any safety measures? Can we leave the magnet as it is? Should we evacuate the building? Should we isolate the area? rnrnThank you ever so much for your time and help. rnrnI have contacted Oxford several times but they didn't return my emails. rnrnMany thanksrnrnEdrnrn
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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
|
| 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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Gopal Agarwal
Sat. 23 Feb.13,
02:54
[Start of:
'Looking to buy MRI...Siemens Essenza OR GE HDxT ??'
0 Reply]
Category:
Devices, Scanner, Machines
|
| Looking to buy MRI...Siemens Essenza OR GE HDxT ?? |
Hi Folks,
I own a medical center in India and planning to buy a MRI machine. With my budget of INR 35M (USD 700K) I can either get a NEW 16 channel Siemens Essenza or USED gold seal 16-channel GE HDxT.
Can anyone please suggest which one to buy. Essenza looks good as footprint is small and power consumption is low, but FOV is small. Any help will be appreciated.
-Gopal
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Steven Ford
Tue. 31 Jan.12,
08:19
[Reply (1 of 2) to:
'RF shimming'
started by: 'Reader Mail'
on Thu. 1 Oct.09]
Category:
Basics and Physics
|
| RF shimming |
For Magnetic fields, the overall field is adjusted to push it up a little bit in one spot and push it down a little bit in another area. The goal is to create a field that's perfectly homogenous.
The RF field created by the transmit coil likewise must be as homogenous as possible, so that the flip angle is constant throughout the imaging volume. In the past, designers have solved this problem by building coils such as the 'birdcage' style that would create a very even amount of energy inside. This is one reason why the transmit coils tend to be large.
With the advent of 3 Tesla and stronger magnets, the RF resonant frequency also rises. RF energy absorbed in the patient rises with the higher frequencies also, and another problem raises its head: it's a lot harder to make a very homogenous RF field. Even if you are scanning phantoms, the inside tends to be subject to different energy than the edges.
But in the human body, there are all sorts of irregular lumps and bumps that absorb RF differently, further complicating matters.
Now, on modern scanners it's possible to perform a magnetic field shim with the patient actually in the magnet in order to compensate for minute changes in the magnet from one exam to another. For super-high field magnets, an RF shim is also a handy thing to do.
If you have a Multi element RF transmit coil (regular phased array coils are just for receiving) you can run a program which selectively turns up the power in some elements so that the overall signal received is maximized. That's an RF shim.
Steven Ford
Professional Imaging Services, Inc.
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