# Tag Info

## Hot answers tagged medical-physics

8

The goal of such a treatment is to induce damages in the cells of the tumor by mean of ionizing radiation. These radiations can be X-rays (photons), electron, proton or things like carbon ions. The problem is: if you try to irradiate a tumor, you first have to go through normal tissues and the risk is to damage them also. Photons will transfer energy ...

4

A remark up front: I am not a specialist on ultrasound. However, I am a Geophysicist and we use more or less the same principle to image the Earth's interior, just a very different frequency range compared to your problem at hand; in exploration seismics typically 5-100Hz compared to frequencies in the Megahertz range for ultrasound imaging. A transducer ...

4

I think the real answer is that when it comes to nanorobots, the materials we're using readily oxidise. Put them out of a vaccum and they're toast the instant they come into contact with the atomosphere. Biology manages to deal with this by using a different material set, and encapsulating everything pretty well so that the environment doesn't damage cell ...

3

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 ...

2

There is no direct conversion for what you are asking. Curies are a measure of activity equal to $3.7 \cdot 10^7$ decays per second. Rad are a measure of absorbed dose equal to 1 Joule per kilogram. In order to determine how much radiation is received, you need to know things like the amount of time of exposure, distance between source and target, ...

2

Just to try some numbers. If you eat 2000 cal/day thats 4200 * 2000 = 8.4MJoules, with 86,400 seconds/day that's = 100Watts average so about what a person generates in heat

2

The word "specific" (as in specific gravity or specific heat capacity) means per unit mass, so you could call it "specific flow" or "specific volumetric flow".

2

Your description of the basal metabolic rate is spot on, and it is indeed equated with the amount of heat you give off. The way to look at this is yesterday I weighed 60kg and today I weigh 60kg, but in between I've consumed about 2,500 calories. That energy must have gone somewhere. Since I'm the same today as I was yesterday there's no net energy change ...

2

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} ...

2

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 ...

1

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 ...

1

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

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 ...

1

I'm not sure the assumptions of your question are true. For example, in this picture, both the bones and the metal ring appear black. Can you link to examples of the white bones/black metal x-ray images you describe? There are ways to obtain contrast with x-rays that do not rely on absorption, such as scattering. However, I think most medical x-rays are ...

Only top voted, non community-wiki answers of a minimum length are eligible