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Brent Johnson

Wed. 21 Aug.13,
19:38

[Start of:
'Hitachi Airis II question'
0 Reply]


 
  Category: 
Sequences and Imaging Parameters

 
Hitachi Airis II question
I have a question for a Hitachi Airis II .3T non-upgraded gradients
On T2 FSE sequences especially on thumb sagittal slices. Image quality very poor, grainy. What is ideal bandwidth and TE settings for improving image quality? Also is positioning and angle of slice a factor in image quality. The closer the anatomy is to edge of coil, does that effect image quality.

Thanks Brent
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Isa Toni Toni

Wed. 24 Jul.13,
14:43

[Start of:
'why there is T2* but not T1*'
2 Replies]


 
  Category: 
Sequences and Imaging Parameters

 
why there is T2* but not T1*
often we heared about T2* but not much of T1*. i heard about T1* before correction in T1 mapping, but i guess that is different than T2 and T2* which have diffirent methods to acquire them. any comments on this is much appreciated
 
 

Isa Toni
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geo log

Mon. 15 Jul.13,
14:55

[Reply (1 of 3) to:
'Titanium & MRI Safety'
started by: 'Barry Ng'
on Wed. 10 Jul.13]


 
  Category: 
Safety

 
Titanium & MRI Safety
Titanium is not, NOT under any, ANY circumstances considered MR SAFE. Titanium is MR CONDITIONAL. When the conditions are observed titanium causes no harm to the patient or the MR equipment.
When the conditions are not observed the concerns you voiced may come into effect.
Refer to mrisafety.com
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Barry Ng

Wed. 10 Jul.13,
17:10

[Start of:
'Titanium & MRI Safety'
2 Replies]


 
  Category: 
Safety

 
Titanium & MRI Safety
I am trying to understand why titanium is considered "MRI Safe".

I see three potential problems when considering the MRI safety of a material:

1 - If it is a ferromagnetic material extreme damaging forces will be applied to the material if exposed to a very strong magnetic field. Titanium is not a magnetic material so I do not see this as a problem.

2 - When a relatively large flat conductor (e.g. a titanium plate) is exposed to a changing magnetic field (Faraday's law) eddy currents will be created internally as the result of induced voltages. These eddy currents can be very high and cause resistive heating ("I squared R losses"). I would think these eddy currents would have the potential to cause extreme heating of the titanium. I know from experience this does occur with steel and titanium has a conductivity about the same as steel. Titanium is not magnetic as is steel but induced voltages due not require a ferromagnetic material (.e.g. copper as used in real world generators, etc.).

3 - Induced voltages are created across the length of a conductor as the result of the conductor being exposed to a changing magnetic field ("genrator effect" - Faraday's Law). Again this effect does not require a magnetic material. So why, at best, does this effect not have the potential to be uncomfortable or even very painful to the MRI patient being exposed to a huge changing magnetic field?

Invariably the response to why titanium is safe focuses on the fact that it is not magnetic. I get the deer in the headlight look when I ask about eddy current heating and induced voltages.

Please help me understand why unduced eddy current heating and induce voltages are not a concern.


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Reader Mail

Sun. 19 May.13,
05:18

[Start of:
'hearing protection'
0 Reply]


 
  Category: 
Safety

 
hearing protection
Here's the deal: I am an MRI student doing an internship on a GE 1.5T magnet. I mistakenly scanned a person (shoulder, about 15-20 min) without ear plugs or headphones. She complained to me personally and said that she should have had protection. I agreed. I am considering this a huge deal. Am I overreacting? I obviously know that hearing protection is a basic requirement for scanning and that significant damage can occur to the patient. In the heat of the day, I just got distracted and it slipped my mind. Is this an offense that can result in me getting fired?
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