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1answer
55 views

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 ...
1
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1answer
29 views

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 ...
1
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2answers
82 views

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 ...
2
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1answer
42 views

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 ...
0
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1answer
11 views

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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1answer
23 views

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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0answers
15 views

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 ...
0
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0answers
27 views

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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0answers
36 views

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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2answers
123 views

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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1answer
159 views

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 ...
0
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1answer
63 views

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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2answers
95 views

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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0answers
23 views

speed of sound and ultrasound machine

How can you determine the speed of sound of a liquid using a medical ultrasound probe? I am unable to get a hold of a hydrophone. Is it possible to determine C using a or m mode?
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2answers
391 views

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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2answers
426 views

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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1answer
178 views

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 ...
2
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0answers
87 views

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 ...
2
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3answers
157 views

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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0answers
34 views

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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0answers
506 views

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 ...
2
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2answers
95 views

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 ...
7
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2answers
438 views

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 ...
0
votes
1answer
290 views

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 ...
2
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0answers
75 views

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 ...
0
votes
1answer
108 views

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 ...
1
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1answer
557 views

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 ...
2
votes
1answer
65 views

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". ...
1
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1answer
3k views

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 ...
6
votes
1answer
307 views

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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2answers
1k views

Equivalences for mCi doses and Rads?

What would be the magnitude of radiation received for a 50mCi dose of radioiodine I-31 as compared to say RADS? I read that it might be on the order of about 35 RADS. Does this make sense?
2
votes
2answers
246 views

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 ...
3
votes
1answer
152 views

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 ...
4
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3answers
1k views

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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2answers
1k views

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 ...
9
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1answer
207 views

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 ?