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Questions tagged [medical-physics]

A field of applied physics dealing with the application of physics to diagnosis and treatment of diseases.

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64 views

Are 5G signals dangerous? [duplicate]

Ive been seeing a lot lately on the dangers of 5g and exposure to the internet and mobile signals but I dont understand why they are considered harmful when the 5g frequency band will be around 25 Ghz....
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5answers
44 views

Harm from gamma radiation compared to beta radiation

why is a small dose of gamma radiation less harmful than a small dose of beta radiation? even though gamma radiation is more penetrating. This is a question I was wanting to know and had difficulty ...
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2answers
61 views

Why is radiation dangerous? [closed]

From Wikipedia: Exposure to radiation causes damage to living tissue; high doses result in Acute radiation syndrome (ARS), with skin burns, hair loss, internal organ failure and death, while any ...
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1answer
78 views

How can sunlight cause skin cancer? [closed]

If the atmosphere absorbs the UV wavelengths, then what’s left is visible, IR and maybe a really small amount of UV that transmits it’s way to earth. IR and visible are non ionising, so is it the case ...
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3answers
3k views

How much radiation do nuclear physics experiments expose researchers to nowadays?

I am curious about how much radiation do experimental nuclear physics researchers/students suffer in nowadays research environment. I know this may be a dumb question, but I have can found answer ...
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2answers
2k views

Why use gamma over alpha radiation?

In radiotherapy, the goal is to kill as many cancer cells in a localised area without killing normal cells right? So what possible reason would there be to use gamma irradiation over alpha irradiation?...
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3answers
602 views

Why use ultrasound for medical imaging? [closed]

What advantage does ultrasound have over sound between 20-20000Hz that it is used in medical imaging over sound in that frequency range?
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1answer
28 views

How does an magnetic resonance guided focused ultrasound (MRgFUS) machine work?

As a medical application, magnetic resonance guided focused ultrasound (MRgFUS), is new I the treatment of some parkinsonian diseases, prostate cancer, none problems, and more. However, I am not sure ...
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1answer
224 views

X-ray imaging - why does bone show up as white?

I'm looking at why bone shows up white on a radiograph. The only explanation I seem to get is the bone is dense and 'absorbs more x-rays'. This is all ok, but it still doesn't seem to explain why ...
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0answers
19 views

Frequency domain theory for absorption and scattering tomography

TL, DR: in the theory absorption and scattering tomography it is possible to obtain a formula for the field in a detector point once it is known the position of the source and the inhomogeneities of ...
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1answer
194 views

Electric potentials around the heart. What and How does the EKG measure?

Recently I've been having trouble understanding how(and even what) the EKG measures and have not been able to find a satisfactory response. The health science forums haven't been much help and I ...
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1answer
32 views

Factor that effect resolution in CT and PET

What factors effect the resolution if CT images and PET images? For CT I have come across a few, in terms of Ray width Dector aperture focal spot Which are common for most x-ray based scan as I ...
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1answer
22 views

Averaging speed of ultrasound between two differnt boundaires

Why is the speed of ultrasound average between two different boundires? As I understand in ultrasound the speed of sound is an average speed of $1540ms^{-1}$ to calculate time intervals into ...
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2answers
69 views

Spatial frequency and high contrast imaging

I am having a issue with a question with regards to how spatial frequency and high contrast are related. Explain how high contrast resolution of an imaging system may be expressed in terms of a ...
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1answer
40 views

Number of cycles in ultrasound pulse

Why in clinical ultrasound is there 2-4 cycles per pulse? I cant seem to find a reason why, this is happening Has it to do with the piezoelectric not being instantaneously stopped when an ...
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1answer
61 views

Compton scattering and X-ray Imaging

Is there any importance to having Compton scattering in x-ray imaging. I ask this because most books that I have read talk about reducing the effect through anti-scatter grids, as Compton scattering ...
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1answer
23 views

Photomulitplyer Tubes and NaI(TI) crystals in Gamma Camera, Energy and spatial resolution

I am trying to understand how the PM tubes and NaI(TI) crystals are used for the energy and spatial resolution. I understand the principle behind how the crystals and PMT work, but very confused to ...
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2answers
63 views

Changin the optical depth (axial resoltuion) on an Optical Cohernce Tomagrpahy system

So the axial resolution in a OCT system is given by: $$I_c=\frac{4ln2}{\pi}\frac{\lambda^2}{\Delta \lambda}$$ My question what would you do to say increase the axial resolution, and how would it ...
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1answer
27 views

Adjusting dose rate, Image quality, X-ray Flurocopy

When adjusting the dose rate, in this procedure from either film or detector the image quality would become poor due to less photons being transmitted via the x-ray tube. How many ways with respect ...
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1answer
101 views

CT scan advantages and disadvanatges Vs General Radiology

So recently I have been looking at how CT scans work and the disadvantage and advantages they have compare to general radiology techniques, but this has brought up some questions. My question refers ...
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2answers
359 views

Fluoroscopy vs. fluorography

What is the difference between these two techniques? So far I understand that in Fluoroscopy, it uses a continuous stream of x-rays, where as Fluorography it uses a pulse, but what other differences ...
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1answer
42 views

Beam Hardening in computed tomography

My question is, why in CT do they reduce the beam hardening effect with high KV? The reason I am asking this is, that beam hardening is when say an x-ray passes through a patient and the low energy ...
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0answers
28 views

Bremsstrahlung Radiation and it interaction with the nucleus

Recently I have been reading up on Bremsstrahlung Radiation, and how it is generate in diagnostic x-rays. So as I understand as the electron is fired at a target, which in diagnostic x-rays is ...
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3answers
81 views

What is the relationship between the amount of radioactive substance and the harm it does to the body?

This is probably a very simple question, but I wonder how the amount of radioactive substance is related to the radiation it emits and therefore the harm it does to the body. If I held 0.1g of barium-...
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1answer
128 views

Accurate measurement of total lung capacity / vital capacity

I'm currently working on a practical problem: How to measure your total lung capacity and/or your vital capacity accurately. Any suggestions or experience? One of the methods that can be found with a ...
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1answer
84 views

Why has it taken so long for people to talk about using Far-UVC light for disinfecting?

If you don't know what I am referring to you can see this simple TED talk https://www.youtube.com/watch?v=YATYsgi3e5A. There are also many articles online about it. After watching that TED talk, all ...
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2answers
524 views

Is my tritium keychain emitting significant amounts of radiation?

I recently purchased a tritium keychain, composed of a small glass vial of tritium gas partially enclosed in a stainless steel fob. Here are the Amazon links so you can see a specific example: Link ...
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1answer
35 views

Effective strength of prescription glasses for arbitrary angle

I am trying to understand the optics of prescription glasses. Prescriptions have a spherical and a cylindrical (with associated axis) component specified in dioptres which are roughly additive. For ...
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1answer
379 views

If you are near radioactive waves but they don't pass through your body can you still get cancer? [closed]

If intense gamma rays are flying in the opposite direction from me will they still affect me? I wouldn't think they could, yet people can get cancer from being near radioactive materials. Is it ...
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2answers
110 views

Doppler effect of sound waves in blood

When the sound waves that are produced by a ultrasound machine reflect there happens an increase into the frequency of the sounds. Why is that so? I think it should be the other way around because the ...
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0answers
26 views

Is it possible to make a not penetrate all layers of a matter (a human tissue for example), but interact with it at a certain point?

Given a block of matter, for example human tissue, is it possible to cut inside the block without damaging anything else? Going by what I was taught at school, light has many properties by which it ...
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2answers
86 views

Out of all the medical imaging radionuclides, why is technetium-99m the most common?

There are medical tracers like Xe-133, I-131 etc.(what are some other ones?), but why is Tc-99m the most common (most suitable)?
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1answer
278 views

X-ray emission spectrum modelling of a tungsten target anode at 40 kVp

I have an X-ray tube which has the voltage potential from $4kV$ to $60kV$ and the target material is Tungsten $(W, Z=74)$. The emission spectrum provided by the manufacturer is given below: The ...
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1answer
1k views

How may sound waves behave inside the human body?

in Vibroacoustic Therapy (VAT) sound is transferred to skin surface via transducers that are in direct contact with the skin. This means no energy loss to surrounding air. We are mostly using ...
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1answer
209 views

Which is the most toxic isotope of plutonium and what makes it toxic? [closed]

Some sources say plutonium is one of the most toxic substances known, while this challenge from Bernard Cohen to Ralph Nader challenges the toxicity. I heard that only one of its isotopes is toxic, I ...
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2answers
501 views

In MRI why don't metals in the body get ripped out?

Why doesn't the strong magnetic field cause iron in the blood to at least pool to the surface of the body.
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1answer
36 views

What accuracy atmospheric reading is needed when calculating dose in Radion onchology?

When determining the dose in radiation delivery systems used in radiation Oncology, the atmosphere attenuates radiation from the source before it hits the target. The dose is calculated using, among ...
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1answer
203 views

Health issues concerning December 27, 2004 gamma ray burst [closed]

Did the 12-27-2004 gamma ray burst cause any illness affects upon life on earth? Do we know what hemisphere of the earth or portions of the earths surface received the highest radiation? What was the ...
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1answer
347 views

What's the role of quantum mechanics in the radiotherapy for tumor and why the proton radiotherapy is much more expensive than photon radiotherapy?

I am wondering the role quantum mechanics plays in the process of radiotherapy, such as by photon, or by proton. In particular, I am curious about why the proton radiotherapy is much more expensive ...
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3answers
180 views

How are photons told apart by a PET scanner?

From what I've read, a radiopharmaceutical, such as FDG, enters a body and emits positrons that annihilate with electrons, emitting two equal gamma rays in opposite directions. Diametrically opposite ...
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4answers
143 views

Radiation and cancer

We were doing a radiation experiment, in my physics class. Obviously, all of the students why crying in fear of getting cancer. The brief explanation given by my teacher, as to how radiation exposure ...
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1answer
131 views

Finding the combined uncertainty of weighted measurements

I am currently doing some simple simulations of radiation dose from several treatment fields. I am looking at the dose within a certain voxel of a patient receiving radiation therapy, being treated ...
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1answer
248 views

Use of the different magnetic fields in MRI [closed]

Hi I was wondering if somebody could highlight the purpose of a) The uniform magnetic field in the MRI scanner b) The non-uniform magnetic field in the MRI scanner Thanks
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3answers
3k views

What causes 'quantum mottle'?

In medical imaging quantum mottle is described as the "random variation of photons incident on a radiation detector" (Huda,2010). But according to (Rangayyan,2004) is a distinct feature (specifically ...
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1answer
41 views

Is Electroencephalography mapping possible?

EEG measures voltage fluctuations resulting from ionic current within the neurons of the brain. Would it theoretically be possible to draw a 3D model of the brain using these signals if a sufficient ...
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1answer
273 views

Definition of contrast-to-noise ratio?

I have been looking at definitions of the contrast-to-noise ratio. As indicated in numerous sources (e.g. here (page 12)), the contrast to noise ratio between two signals $A$ and $B$ is: $$ CNR=\frac{...
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2answers
159 views

Reverse MRI (MRI scalpel)

Are there any systems, which exploit any sort of "reverse" MRI technique? We can create magnetic field so that it has required value only in desired location (say, cancer tumor) and then pass ...
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4answers
7k views

How radioactive is uranium?

Look at this video: People face uranium directly. Does this mean the radioactivity of uranium is very weak? Because its half-life is very long? Personally, I would never dare to touch any ...
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0answers
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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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1answer
708 views

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 ...