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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Use of Anger logic for sub anode size spatial resolution using pixelated scintillation crystals

Anger logic is widely used as a centroiding formula to spatially locate the scintillation event in multi-anode PMTs (MA-PMT). For pixelated scintillation crystals with pixel sizes smaller than single ...
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Find CT with SliceLocation tag

I'm sorry for the mistakes I did in my previous post, I will not mention, in this one, specific software. I just need to access to a whole body CT dataset with a specific tag, "SliceLocation"...
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Does an X-Ray tube have an electric field inside of it? [closed]

I searched the question on the web, but could not a satisfactory answer. Anyway, the question is as follows: The X-Ray tube consists of an anode, which essentially accelerates the electrons, and a ...
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Standard deviation in matRad

I'm new to matRad and I just tried to do some simulations. For example, I loaded TG119.mat and runned a photons simulation with default parameters: The graph I obtain from this simulation it's the ...
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6 answers
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In radiotherapy, why do normal tissiue or organ cells not die of radiation?

In radiotherapy, why don't normal tissiue cells or organ cells in the way of incoming radiation die, but tumours die instead?
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3 answers
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Difference between X-ray device and linac

What is the difference between an x-ray device and a linac (for medical purposes)? In case both have to produce photons. Linac: source X-ray device: source As far as I see the major difference is, ...
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Difference between an electromagnetic calorimeter and a pet-detector

Is there a conceptual-technical difference between an electromagnetic calorimeter and a pet-detector? Surprisingly I couldn't find a better/rough concept of an Ecal but ultimately it consists of a lot ...
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Flow rate of Venturimeter $v=\sqrt{\left(\frac{2\left(P_{1}-P_{2}\right)}{\rho}\right)}\left[\left(\frac{A}{a}\right)^{2}-1\right]^{-\frac{1}{2}}$

How to derive $$v=\sqrt{\left(\frac{2\left(P_{1}-P_{2}\right)}{\rho}\right)}\left[\left(\frac{A}{a}\right)^{2}-1\right]^{-\frac{1}{2}}~?$$ I came across it while studying fluids mechanics in medicine ...
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Scattered radiation factor for diagnostic

I need the confirmation, is it if we put survey meter at 270 degree, does the reading of scattered radiation is same with 90 degree. In my opinion, the reading would be same as the distance is still ...
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Dynamic Small Airways Collapse - Understanding the physics of the pressure drop from alveolus to mouth in human lungs

EDIT: I think I have thought of a much better phrasing of my question using the middle diagram below. a) If intrapleural pressure is >0 does airway collapse always occur? b) In a hypothetical ...
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2 answers
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Which among alpha, beta and gamma emitters is most dangerous for human body?

Lets say we have three candies: One with alpha emitter in it, one with beta emitter in it and one with gamma emitter in it. All have similar activities. You must eat one, put one in your pocket and ...
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1 answer
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Can photons release electrons? Can neutrons decay into heavier particles?

I'm studying the classification of radiation in 'Radiation Physics for Medical Physicists' by Ervin B. Podgorsak. At some point in the explanation of the two-step process of ionization for indirectly ...
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A book for single-photon emission computed tomography (SPECT) physicality

I am a graduate student, and I research the radiation detector which is similar to SPECT geometry. So I need a book to understand the physics inside the SPECT. Could you recommend books that describe ...
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Average geometric efficiency in Positron Emission Tomography

While researching for my thesis I am using the book "Physics in Nuclear Medicine" by Simon R. Cherry, James A. Sorenson and Michael E. Phelps. In Chapter 18.8 they talk about the average ...
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Why does MRI (Magnetic Resonance Imaging) have high contrast and spatial resolution albeit having lower frequency and higher wavelength?

So we've been discussing this in the classroom and I really can't say if my answer to this question is correct since there could be various answers to this. I know that to have a high-resolution image,...
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1 answer
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Can the recoil to the nucleus induced due to radioactive decay be enough to break inter-molecular bonds?

let's say I have radioactive labelled molecule such as ${}^{99m}Tc$--Methyl diphosphonate ${}^{99m}Tc$ undergoes gamma decay and emits a photon of 140 KeV. Said molecule also forms a bond inside bones,...
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In ultrasound, why doesn't the reflected sound gets reflected again on its way back?

Consider the diagram below illustrating how A-scans work, why doesn't some of the reflected sound on its way back at the red circle interface reflect again (thereby reducing the signal intensity ...
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Why decreases the pressure inside hollow organ, as volume is removed?

I would like to explain in physical terms, why the pressure in the uterus falls, if volume (amniotic fluid) is removed. So far as I understand, p in spheres is inversely proportional to the radius, ...
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How do single-pixel cameras work?

To obtain images using a single-pixel camera we need a Digital Micromirror Device (DMD) because single-pixel cameras only possess a single detector (article). From my understanding, a single-pixel ...
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2 votes
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What is the physics behind why incorrect cuff size for measuring blood pressure manually or automatically lead to inaccurate results?

The biophysics behind measuring systolic and diastolic blood pressure manually with a cuff and stethoscope is that Determine the approximate pressure it takes for the cuff to occlude the brachial ...
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2 votes
1 answer
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Why is Polonium-210 more lethal than other radioisotopes? [closed]

So it takes a single microgram or less of pure Polonium-210 to be lethal. Which according to basically all sources makes it the most toxic material or at the very least the most toxic element. But why ...
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1 answer
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Why is long-term radioactive material so bad?

So i'm currently researching nuclear power and nuclear energy as it is a topic that has always interested me, but when researching nuclear fission waste, and hearing about waste that has a half life ...
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1 answer
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Bremsstrahlung radaition of a Proton

I often hear Bremsstrahlung being discussed in relation to electrons, for example, x-ray generation. Although I was reading a review on Proton Therapy and when discussing the influence of the various ...
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1 vote
1 answer
211 views

Energy dependence on bragg peak width

If you look at this plot of proton Bragg peak at different energies. You can see that the Bragg peak shifts right (which makes sense) but also the height and I think the width of the brag peak is ...
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1 answer
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Is $200 \,\text{J}$ enough for heart defibrillation? [closed]

In some movie I saw that defibrillation was done on a patient by emitting $200 \,\text{J}$ electric impulse onto heart region. I couldn't in noway imagine is this quantity big or small, so I've tried ...
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-2 votes
3 answers
331 views

Has anyone tried to find the wavelength to the Corona virus cell? [closed]

I have seen websites and videos that show how cancer cells can be destroyed using sound resonance oscillation. So has anyone heard of anyone who is in the field of sound resonance trying to capture ...
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High pressure cryonics

In this link, it is suggested to use high-pressure cryonics to freeze living cells, tissues or small organism as opposed to various and potentially toxic anti-freeze agent. The core idea is that over ...
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How does ultrasound imaging localize points in the $x$-$y$ plane?

Lots of sources describe how ultrasound imaging uses the time differences between wave emission and reception to calculate distances to points in the body. This makes sense for how localization works ...
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Refraction or reflection in dermoscopy?

I was reading a dermoscopy textbook, and I came across the following statement: Why do most moles just look brown? The stratum corneum reflects light, reducing the ability to see detail of ...
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-1 votes
1 answer
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Effect of bluetooth headphones on health [closed]

There was an article on the internet assuming that there's a high chance that bluetooth headphones cause a lot of mental and physical damages to our body. They explained it in a pretty neat way if I ...
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1 vote
1 answer
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Radioactive Tracer - calculate fraction that decay before excretion

I was reading about the use of Technetium-99m as a radioactive tracer, how it decays via gamma emission but is also excreted by the body. Assuming the body handles Tc-99 and Tc-99m the same, some will ...
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1 vote
2 answers
660 views

Parallel and Anti-parallel Protons in NMR

I'm an Alevel Student trying to understand the concept of NMRI, I understand that when an external magnetic field is applied, the protons either line up with (parallel) or line up against (...
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Hyperspectral Imaging

Is it possible for a HSI camera to detect how long back a particular wound occured in the body? Eg: There's a body for postmortems with some marks/wounds at some places, can a HSI camera help us in ...
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2 votes
1 answer
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Calculating equivalent dose from exposure to radium

My mother was unknowingly exposed to radiation from some radium needles (Ra-226). The exposure was at waist height, from a distance of about 25cm, for a total duration of about 1.25 hours. This ...
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What causes a steel gurney to accelerate towards an MRI machine? [duplicate]

What is the basic concept in electromagnetism that explains the MRI projectile effect in which steel objects such as gurneys crash into an MRI machine with a force that is sufficient to kill or ...
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How to calculate tube flow in layered ultrasound phantom using Doppler

Using a tank with the top filled with water and the bottom filled with a gel which is slightly denser than the water. Inside the gel is a tube tilted 60 degrees above the horizontal axis. The tube ...
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Equivalences for mCi doses and cGy?

I was searching a lot and could only find dosages for curing cancer and allowed emission, but no Iridium 192 dose that could be given internally through brachy sources been found, lets say a 700 cGy ...
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2 votes
1 answer
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Ionizing Radiation Interaction with Air

Asking this question purely out of interest. I have no background in this topic. In modern radiation therapy, there's air in between the treatment machine head and the patient. With the high levels ...
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2 votes
0 answers
306 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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3 votes
5 answers
212 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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1 vote
2 answers
139 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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1 answer
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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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13 votes
3 answers
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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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7 votes
2 answers
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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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4 votes
3 answers
662 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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1 answer
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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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1 vote
1 answer
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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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3 votes
1 answer
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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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2 votes
1 answer
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How can a frequency-specific interference in MRI be limited to a single stripe on the corresponding image (zipper artifact)?

The so-called herringbone or spike MRI artifact on a given example could be traced to a specific point(s) in Fourier space ("k-space"). The idea is that during the acquisition of the image, a certain ...
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1 answer
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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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