# Tag Info

4

In MRI, an image is created by using gradient magnetic fields. By adding a gradient magnetic field the magnetic field is different at different positions in the body. The most important term in understanding the use of this is the larmor frequency. This is the frequency with which the hydrogen atoms will precess in a certain magnitude magnetic field and is ...

3

Several reasons why this is not a great idea: 1) signal to noise ratio scales with field strength: 1.5T is considered a reasonable number although it is possible to get diagnostic images in some situations with lower fields. 2) inductance of coil capable of producing such large fields - try computing the energy stored! 3) during ramping of the magnet, you ...

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AdamRedwine's answer also doesn't take into account the fact that the radioactive iodine will be processed by the body and expelled in the urine over the course of a few days. This is what the comment on the increased exposure on the bladder wall is from, referenced by another comment. So I believe (but am not an expert in this area) that the exposure will ...

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It might not actually answer your question, but to throw it into the bowl: There are some advances in MRI using permanent magnets and even conventional electromagnets with static magnetic fields of about 0.5 Tesla. As far as I know one can do imaging with a reasonable resolution with these devices without the need for extensive cooling. They are used for ...

1

If you pump gas along a pipe then pressure drop per unit length of the pipe depends on the diameter of the pipe. The smaller the pipe the harder it is to pump the gas through it. The pressure drop is given by the Darcy-Weisbach equation: $$\Delta P = f_D \frac{\rho v^2}{2} \frac{\ell}{d}$$ though with the complication that the density of the gas depends ...

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It looks to me like they mean J/cm^2 doesn't it - but they may well just be pulling numbers out of the air. To be electromagnetic flux is should be W/cm^2 - but it looks like a dosage is intended. 440J/treatment over 582cm^2 is 0.756J/cm^2 per treatment. But that just means that the little "j" does not mean what we think it does. AFAIK: there is no ...

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I am just guessing on this based on the reference you posted in the comments. Sometimes dB's are referenced to a max level, like with audio at 120dB. In this case they look at the difference between the maximum. In your case, 10,000 is the max, or 40 dB. Based on this scale comparison: I would guess apostilibs to dB is done like this: $dB = 40 - ... 1 The image is 2D not 3D because it's a slice through the object. As for how it's done, suppose you're trying to make a (very low resolution!) image of this object: If you measure the intensity in the horizontal direction you can relate the measured intensities$I_{0,T}$and$I_{1,T}$to the intensities in the four chunks of the object by:$\$\begin{align} ...

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