XPost: sci.electronics.design
From: bill.sloman@ieee.org
On 21/02/2026 3:46 am, john larkin wrote:
> On Fri, 20 Feb 2026 18:32:18 +1100, Bill Sloman
> wrote:
>
>> On 20/02/2026 3:54 am, john larkin wrote:
>>> On Thu, 19 Feb 2026 14:13:06 +0100, nospam@de-ster.demon.nl (J. J.
>>> Lodder) wrote:
>>>
>>>> Bill Sloman wrote:
>>>>
>>>>> On 19/02/2026 9:56 pm, J. J. Lodder wrote:
>>>>>> Bill Sloman wrote:
>>>>>>
>>>>>>> On 19/02/2026 7:49 am, Ross Finlayson wrote:
>>>>>>>> On 02/18/2026 12:43 PM, Python wrote:
>>>>>>>>> Le 18/02/2026 à 20:13, Ross Finlayson a écrit :
>>>>>>>>> ..
>>>>>>>>>> and, you know, magnetic monopoles, is widely employed
>>>>>>>>>> in medical imaging and the like.
>>>>>>>>>
>>>>>>>>> No.
>>>>>>>>
>>>>>>>> Resonance imaging (NMR) is a thoroughly different mechanism
>>>>>>>> than Roentgen rays.
>>>>>>>
>>>>>>> But as the name implies, it's nuclei of the atoms involved that exhibit
>>>>>>> the resonance. It's a remarkably low energy effect, and you need
>>>>>>> remarkably high magnetic fields to get it to give you a detectable
signal.
>>>>>>
>>>>>> Nevertheless, it is easily demonstrated in the kitchen
>>>>>> with some simple electronics.
>>>>>
>>>>> Sort of.
>>>>>
>>>>> https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
>>>>>
>>>>> There are lots of different ways to exploit nuclear magnetic resonance.
>>>>> The earth's magnetic field is high enough to let you devise experiments
>>>>> that can demonstrate the effect on a kitchen table.
>>>>
>>>> Nothing 'sort of'.
>>>> You -can- easily demonstrate the effect on the kitchen table.
>>>> (at audio frequencies) Wikipedia is right here.
>>>>
>>>> Jan
>>>
>>> NMR was a fairly popular analytical chemistry business for a while. We
>>> made pulsed-field gradient coil drivers and temperature controllers
>>> for Varian.
>>>
>>> But superconductive magnets and liquid helium are expensive, and other
>>> techniques took over. It was common to visit a lab that had a giant
>>> magnet in the corner, warm and collecting dust. A similar mass spec
>>> technique, FTMS, died for the same reason... too expensive.
>>>
>>> Agilent bought Varian to get their medical stuff but immediately
>>> killed the NMR operation. I think Bruker still does NMR.
>>>
>>> Hospitals prefer cat scans to MRIs these days. Cat scans are much
>>> cheaper.
>>
>> But not as good. When I had a ruptured intervertebral disk back in 1988,
>> I paid extra to get an MRI scan and my clinician was blown away by the
>> higher resolution it offered - it was about twice as good as he saw in
>> X-ray based CAT scans. He got my okay to use it for teaching purposes.
>>
>> And it didn't raise my risk of getting cancer at all.
>
> I had a head injury and volunteered for a long-term study, which
> involved periodic MRIs. I guess I've had 15. They are slow and boring.
> The gradient coils are very noisy.
My father complained about that too. I knew why the gradient coils were
making their noise, so it didn't worry me.
> https://www.dropbox.com/scl/fi/yte89c83s03fghphb7thh/Brain_1.j
g?rlkey=tb71ahj2lp3zabw88ws6reofx&raw=1
>
> A cat scan takes about a minute.
Getting through the whole procedure takes a lot longer than that. My
local hospital is only a ten minute walk away, but the hospital insists
on keeping me sitting around for about an hour during even the fastest
procedures. They seem to need to keep the patients intimidated. Or at
least acting as if they are intimidated.
--
Bill Sloman, Sydney
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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