# Tagged Questions

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### What is the best order of learning mathematics before start Monte Carlo Methods for Physics simulation? [closed]

I doing medical physics masters and hope to start my research in Monte Carlo methods to simulate some particle interaction and hence to calculate some unknown physical quantities ( Stopping power and ...
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### Stopping power of charged particles in matter

So I have this diagram of how the stopping power of muons changes with energy: Depending on energy different equations are used to describe the stopping power variation. Now, currently I'm reading ...
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### Are all radioisotopes equally dangerous? [closed]

I'm currently writing an issues investigation on the radioisotope plutonium-239. It's difficult to talk about the dangers of the radioisotope itself, since information on the internet is mixed. ...
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### Bremsstrahlung in body tissue

As far as I know, the intensity of the produced radiation from bremsstrahlung is proportional to: $$I \propto \frac{Z^2}{m^2},$$ where $Z$ is the atomic number, and $m$ is the mass of the particle. ...
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I was wondering. When particles enter a medium it has a finite range until it reaches the Bragg Peak where it deposits most of its energy. Now, heavier ions means less lateral broadening of the beam ...
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### DNA breaks with particles or photons (Radiation therapy)

When protons (or other particles) or photons are used in radiation therapy to treat cancer patients, the main effect is for it to make DNA breaks that hopefully will make the cancer cell die ...
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### Use of slices in CT scans

When carrying out a CAT scan, why are pictures of slices of the respective part taken? Why can't one take the frontal area of the part of the body, and rotate the ring of detectors and X ray source? ...
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### X-ray shielding

X-ray shielding, why is lead used to shield us when taking X-ray images? As far as I remember (but can't find it on wikipedia ... ), the deflection on (high energy) photons increases the more heavier ...
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### Cesium-137 From Fukushima Meltdown

I've been reading up on the Fukushima nuclear meltdown and its effects it had on the environment. The iodine-131 initially released from the incident decayed after 8 days, but other isotopes such as ...
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### What is the physical intuition behind the Bragg peak?

The wikipedia page says: Energy lost by charged particles is inversely proportional to the square of their velocity, which explains the peak occurring just before the particle comes to a ...
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### Safety of Polonium Isotope source

I saw a YouTube video by a guy demonstrating Geiger Counter use and one of his radioactive test sources was a disk with Polonium. He casually mentioned that this was the poison used to kill that ...
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### Determining intake pressure of a cannula returning blood to an ECMO circuit

What are we trying to figure out: We want to know if it is possible to determine the pressure of the inlet for the catheter that returns deoxygenated blood to the ECMO system to help prevent ...
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### Why are pressure/potential differences across a barrier measured from inside to outside?

I don't know if I'm asking clearly, but I'm a Medical Student who is trying to intuitively understand pressure differences and electrochemical gradient (across a semipermeable membrane) differences. ...
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### What is sound intensity?

In my medical physics book it says that Intensity is 1/2 a2/pc=a2/2z Where a is the amplitude, p medium of density, c velocity of that wave and offcourse Z is the impedance. When I google it it just ...
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### ECG depolarization potential

On page 12 of 'ECG Interpretation: From Pathophysiology to Clinical Application' there is a diagram showing the potential difference between the terminals of different leads of an ECG machine when a ...
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### Law of refelction for electron-metal interactions?

I was reading 'Webb's Physics of Medical Imaging' which had a diagram very similar to the following in it: The interaction not the electrons with the anode creates x-rays. This diagram indicates ...
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### How to convert the number of X-rays to one of the radiation dose units?

So I have been struggling while trying to wrap my head around how radiation dose from X-rays work. I understand how to calculate how many X-rays would come from an X-ray tube given some settings. I ...
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### What would be the dose rate of 109 grams of uranium per day/year?

I know that with a Pancake probe that can read alpha you can get up to 30K CPM on a small plate. I ordered a 6" red plate off ebay and measured outside the box when it came in. It registered around ...
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### 3D-CRT vs. IMRT in Radiotherapy

I'm having some trouble truly understanding the difference between these two. As far as I know, the 3D-CRT is just beams from different angles, where you can modulate the beam intensity by lead ...
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### Factors affecting pain of static electricity shock

Referring to How to avoid getting shocked by static electricity?, someone I knew suffered much pain from static electric shocks when touching door knobs or car doors where I didn't feel anything doing ...
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### Understanding percentage dose-depth curves

I just have a little question regarding dose-depth curves. When you look at them, you have on the y-axis the dose, and on the x-axis the depth into your material. What I'm not sure of is how I ...
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### Dose-depth curve of photons vs. protons

The dose-depth curve of protons and photons can be seen in the image below: Now, what I've heard is, that in some cases, proton therapy is advantageous compared to photons, and of course the other ...
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### Lethal dose of Gy's (Grays)

The unit Gray has the dimensions $\text{J/kg}$. I've read, that a dose of about 3-5 Gy's could kill a person within a few weeks - or at least that's usually the case. But I'm not really understanding ...
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### Possible dangers of power lines radiation, wi-fi and gsm technology [closed]

I'd like to know more about the topic mentioned in the title. I have 3 questions. I'd be happy to hear your thoughts on any of those. So if high voltage power lines can cause harm to a human in some ...
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### How does the Darma - Smart Cushion work? Explanation of the new fiber loop ring-down spectroscopy

How does the Darma - Smart cushion monitor your sitting position and obtain the breathing rate, body movements, and BCG (Ballistocardiography) signals? The creators say that they accomplish this by ...
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### Airway resistance greatest in tertiary bronchi

As the title reads, why is airway resistance greatest in tertiary bronchi? Primary and secondary bronchi have a lower surface area than tertiary bronchi so what makes resistance greatest at this ...
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### What is the difference between primary and volume currents in electromagnetism?

What is the basic difference between the two currents and how each is contributing to the magnetic field at source and the surface?
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### Difference between conventional spiral/helix CT and multi-slice spiral CT

I'm currently learning about CT scanners, and come across conventional spiral/helix CT, and then multi-slice spiral CT. What I can get out of it is, that the multi-slice scanner have a lot more ...
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### Copper coils for nMRI

Given the lack of financial efficacy in the medical industry, I was wondering if nuclear magnetic resonance imaging would be possible with a copper/silver coil if the use is short 10 second imaging ...
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### How specifically does an MRI machine build an image from received radio waves

Unlike the excellent Wikipedia page on ultrasound imaging, the one on MRI only explains the principle theory behind MRI - that oscillating strong magnetic fields cause water molecules to emit ...
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### Visual Fields testing: Decibels of sensitivity - meaning

Automated Visual Field test measures the patient light sensitivity in decibels. Questions: If one point has sensitivity of 30 decibels and another point has sensitivity of 27 decibels does it mean ...
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### Medical/Physics Question - Cut Off Finger Preservation

This question might require some knowledge of medical/tissue, but physicists seem to know everything, so figured I've give it a shot here ;) When people put cut off fingers they are told to put the ...
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### What does (simple) $j/cm^2$ represent AND how does this result $6.959j/cm^2$? [closed]

According to the image shown below, this specific Laser Hair Treatment device claims that it has a concentration of $6.959 j/cm^2$. So far by research I have found that it needs around \$6\mbox{ to }7 ...
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### How mirror equation can explain farsightedness correction?

I have a friend who has just show me his medical prescription for hyperopia (farsightedness) correction and he needs glasses with 4,25 diopters for that, which seemed to be weird for me because I had ...
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### Is there a name for a quantity that represents (volumetric) flow per unit of mass?

In a lot of medical literature about blood flow in the brain, researchers denote the amount of volumetric blood flow that passes through a certain amount of brain tissue as "cerebral blood flow". ...
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### How do you calculate the equivalent absorbed radiation dose from activity, type of emission, and the energy of the emission?

I have a sample of U-238 of which my Geiger counter detects beta activity at 700 events per second. Based on the counter's efficiency of 98.6% for U-238, the activity would be about 710 becquerels, I ...
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### How is it possible for an Ultrasound device to correctly interpret a negative density change in tissue?

I understand the principles of Ultrasound Imaging, and the mathematics behind sonar velocity, impedance, and reflection. I also understand that an Ultrasound device recieves an echo produced by ...
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### Is metabolic rate the amount of heat given off?

The Basal Metabolic Rate is intuitively expressed as "the amount of energy you consume just sitting around." In some places it seems to be equated with the amount of heat that you give off. Is this ...
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### Why (infra-)red light is not used in diagnostics?

I noticed that human body conducts red visible light quite well. A hand placed over a powerful red lamp seems to be semi-transparent while over any other color it does not. Possibly the light ...
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### Nanorobots. What stops us from producing them yet?

If we can already predicts accuratelly motion on molecular levels, what stops us from developing small robots to, for instance, navigate through our blood vessels looking for cancerous cells and ...
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### Could cell-phone radiation cause cancer?

It is very crucial that I ask whether it could and not whether it does. I do not mean to be the least controversial. To my surprise, having read "Physics for Future Presidents" by Richard Muller last ...
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### How does fluoroscopy (x-ray) imaging work in practice?

I know the basics, that by measuring how much x-ray signal reaches each 'pixel' on the receiver we can measure how much has been absorbed. But this gives only a single channel of information, e.g a ...
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### Proton therapy in cancer treatment

Why are protons used in cancer therapy ? Is there any advantages compared to classics X-rays treatment or electron treatment ?