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10

No, cell phone use does not cause cancer. We know it doesn't cause cancer because: There is no plausible mechanism. Animal studies show no effect. Human studies that get non-null results don't show a dose-response. Doing these cell-phone studies with human subjects makes as much sense as doing studies to figure out whether I can cause my neighbors to get ...


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 ...


6

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 ...


5

Lead : 1.65 €/kg, Gold : 35,000€/kg, Uranium (even depleted) : cost unknown, with possible radioactive contamination. So I think it's just a question of cost and practical use. Lead is cheap and available.


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 ...


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

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 ...


3

This wiki article covers most bases. In conclusion, the connection to cancer is unclear from controlled studies. There is some surface heat that can be generated when next to the head, of the order of 2 watts but not clear how bad that is. Sunbathing hatless heats by many more watts (1300/m^2). Cancer of the skin has been connected with the sun due to ...


3

It could due to multi-photon effects. It's already known that cell phones cause changes to brain activity. This was widely reported in the news. For example see "Cell Phone Study: Cell Ups Brain Activity". As of now, this is an unknown effect. So it might be associated with something that causes cancer. (I'm not worrying.)


3

During proton therapy, most of the damage is actually done in the last few mm before the beam stops - at the point called the Bragg Peak Yes, the penetration distance is largely determined by the energy above a few MeV; as the particle slows down, it starts to dump more energy per unit length. Quoting from "The physics of protons for patient treatment" (...


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 ...


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

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

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 ...


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

If you are asking about cancers such as leukemia the general consensus in the scientific and medical communities is that to date there is no evidence of increased risk due to exposure to high voltage powerlines, mobile phones or wifi. The main risks around high voltage power lines are due to high electric field gradients, especially at close vicinity such ...


2

Some practical information first - the charged particle beam passing through the matter suffers from energy (and also angular) straggling. That means that even if an ideally monoenergetic beam is used, there will be always a finite volume with Bragg peak losses. The bigger initial energy, the bigger is the volume. Protons stopping at 40 mm have straggling ...


2

I am a medical physicist working in a Radiation Oncology department. MLCs are used for both 3D and IMRT plans. In fact, very few hospitals have the ability to make/use the lead blocks anymore. The MLCs define the shape of the radiation field. 3D treatment plans are generated with the user (often the MD) defining the MLC shapes for each gantry angle, and ...


2

Let's suppose you have swallowed one of the Po-210 sources from this student kit. Its activity is 3700 Bq (0.1 μCi). Based on the Table 6 in the meta-study [1], it is probably safe to ingest up to 0.02 MBq/kg of the Po-210. This means, that for 80 kg person, it is probably safe to ingest 1.6 MBq of the Po-210, so you "need" to eat approx. 400 of these ...


2

I pulled out my notes from a shielding class and found that the absorption cross section per atom follows a rule: $$\sigma_a\sim\frac{Z^p}{E^3},$$ where $z$ is the atomic number of the absorber atom, $E$ is the energy of the photon, and $p$ is an energy dependent value between 3 and 5. For most x-rays, $p\simeq 4$. While the cross-section per atom does ...


2

Yes, it is essentially just the Coloumb interaction. Sometimes, this will strip electrons from atoms. However, those electrons might have been responsible for a bond in a molecule, so this will have effectively destroyed the molecule. Other mechanisms include having a nucleus recoil from a proton (perhaps imparting enough energy to break a bond), or ...


1

Let me start off with something that should be obvious but I feel the huge need to say it -- I am not trained in the biomedical field and what I put in my answer should not be construed as definitive and ready-for-use in actual patients. I will do my best and present what I think is correct, but I am not a doctor and don't even pretend to play one on TV. ...


1

Sound waves are pressure waves. We measure it as a logarithmic ratio of intensity. Sound intensity is a useful parameter to measure because it's related to the energy incident on a surface which can be easy to measure. Sound intensity is proportional to pressure squared. When calculating decibels we would have to handle that like so: \begin{equation} I = p^2/...


1

Everyone is likely to have a similar pain threshold to electric shocks. If your friend wears leather soled shoes he will conduct static electricity to earth because they offer much less resistance to earth than rubber or plastic soled shoes. Wearing synthetic clothes may cause a similar effect. If he/she has lower resistance than you (by having sweaty ...


1

Percentage Depth Dose Curves (or PDDs) are used to determine how many Monitor Units (MU) a treatment machine needs to give (or how long the machine needs to be on) to deliver a particular dose to a particular depth. The depth at which the PDD curve peaks is referred to as dmax. Treatment machines are often calibrated so that 1MU = 1 cGy at dmax in water. ...


1

The dose that kills a tumor is deliberately aimed at that tumor. If, instead of using a collimated beam, you put a person in a wide beam for radio "therapy", you would be treating their entire body as a tumor and kill them. The dose in RT is computed locally - "this" part of the body (these grams of tissue) absorbed (were exposed to) "this many" Joules of ...


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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