[Test-Equipment] Radioactive Tube Stamp

[J. Forster]

CAT or CT (Computed Tomography) refers to the computational techniques
whereby the image is reconstructed from various imaging techniques,
including:

MRI - which uses a high magnetic field with superimposed static gradient
fields and HF RF excitation pulses. Gadolinium is used as a contrast
medium. No radioactivity involved.

CT or CAT "scan" - Is actually shorthand for a set of X-Rays taken from
many angles and computationally assembled into 3-D images. Contrast agents
include Iodine compounds, either drunk or given IV. They are not
radioactive.

Gamma scans - Again the image is built up by CT, but the image is created
with a "gamma camera", an array of scintillator crystals and small
photomultiplier tubes and a massive lead "collimator". Lenses don't work
on gamma rays. The gammas are emitted by a radioisotope, such as Thallium,
given IV. This is radioactive. (further, if the heart is being imaged, the
detector output is time sliced, with the time slots synced to an EKG so a
movie can be made of the heart's pumping action.

-John

==============




>   The precise quotation is: "The contrast  medium used in MRI, generally
> gadolinium <http://www.wisegeek.com/what-is-gadolinium.htm>, ".  One may
> also wish to include that this is YOUR area of expertise as a
> professional.
>
> It is ONLY one of the possible dyes used.  In the same reference,
> <http://www.wisegeek.com/what-is-an-mri-with-contrast.htm>, it also
> speaks to the use of Iodine Dyes.
>
> "Rehr MRI", is but ONE specific type.  It is *PRIMARILY* used in cardiac
> MRIs.  It is not "a major" MRI use in the numbers of MRIs conducted.
>
> The most "usual" use of radioactive IV Contrast solutions has been in
> CAT or CT scans.  This does not however exclude the entire realm of the
> "types" of MRIs that are done.
>
> Personally, I *much* prefer to use ASK.COM in lieu of Google.  The
> results are shorter and more to the real point when one uses the
> "proper" search criteria.
>
> On 7/4/2010 2:03 PM, Roger Rehr wrote:
>> Note to all:
>>
>> MRI does NOT use a 'radioactive contrast IV solution'.  Gadolinium
>> compounds are used, and have been since the 1980s, and they are NOT
>> radioactive.
>>
>> If you google 'Rehr MRI' you will get a few references that give more
>> info.
>>
>> 73,
>>
>> Roger Rehr
>> W3SZ
>>
>> On Jul 4, 2010, at 1:37 PM, J. Forster wrote:
>>
>>> Correct. The MRI actually uses the same principles as a YIG
>>> oscillator or
>>> YIG filter, which was originally called NMR (Nuclear Magnetic
>>> Resonance).
>>> Edward Purcell at Harvard got the Nobel Prize for discovering it.
>>>
>>> NMR was originally used for chemical analysis with a magnetic field
>>> and
>>> swept HF excitation.
>>>
>>> MRI is the same technology, but introduces a gradient into the
>>> magnetic
>>> field and lots of computing to develop 3-D images.
>>>
>>> Happy Fourth,
>>>
>>> -John
>>>
>>> ================
>>>
>>>
>>> [snip]
>>>> The reference to MRIs and radioactive issues is the RADIOACTIVE
>>>> CONTRAST
>>>> IV SOLUTION.  It is NOT the MRI itself.
>>> [snip]
>>>> Have a happy 4th!
>>>>
>>>> Bob - N0DGN
>>>
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>
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