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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Why take into account deceleration radiation only, but not acceleration radiation when Bremsstrahlung happens?
Why only take into account deceleration radiation rather than the radiation caused by acceleration when going tangent towards the nucleus and acceleration caused by the change in direction when flyby ...
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Bragg-Gray cavity theory
Why does the Bragg-Gray cavity theory require that all charged particles will not stop in the cavity and dose is solely due to charged particles crossing the cavtiy in the cavity?
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Charged particle equilibrium and Bragg-Gray cavity theory
About the charged particle equilibrium: 'In a small volume in the radiation field, some secondary electrons generated in the volume escape from the volume, and some electrons generated outside the ...
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Gamma and X-Ray Shielding with Photoelectric Effect
The photoelectric effect is most probably seen when the incoming light has lower energy than the energy needed for both Compton scattering and pair production to happen.
The probability of the ...
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How much Uranium would a country like Iran need to produce for supplying its Technetium needs?
This is not a question about politics, although the motivation is a political situation.
Iran, which enriches Uranium to a level of $60\%$ $\rm{^{235}U}$, is claiming it has civilian uses for this ...
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Reverse blood flow in an IV
When the IV drip for a patient is completed, the patient's blood will flow back.
This is apparently due to the pressure difference.
However, IV needles are inserted into veins in the direction of ...
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6-day curie to grams?
I am a pre-med interested in nuclear medicine. I recently came upon this wonderous radioisotope called Mo-99 (which decays into Technetium-99m), but in their industry, they measure the quantity of ...
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Why does vitrification cause less damage to biological tissue than freezing does?
Long-duration cryopreservation of biological tissue (most often semen, egg cells, or fertilized embryos) is typically done at 77 K, since the samples can be easily kept at that temperature by ...
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How does CT imaging deal with the thickness of materials?
In the medical CT imaging field, image of an inspected object is obtained through xray projection. xray is attenuated by the inspected object through the formula $I=I_0e^{-\mu t}$. The projection $p$ ...
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How to treat the thickness of materials in dual energy computed tomography (CT)? [duplicate]
In computed tomography (CT) imaging, the dual energy CT extracts the mass density of two materials based on linear mass attenuation. With two measurements at two different energy, the dual CT can ...
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Why does absorbed dose increase with increasing tube potential in computed tomography?
In X-ray radiography it is a common technique to reduce patient absorbed dose by increasing the X-ray tube potential (kVp) while keeping the detector exposure constant by decreasing the tube current-...
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Depth ionization $\neq$ depth dose for electron beam?
Consider an electron beam which is targeted towards some object with a certain depth. The concept of dose refers to the amount of energy expended by the electrons in collisions with atoms of the ...
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Energy of electron in photon interactions
There are three ways that a colliding photon can cause an electron to be ejected from the nucleus : via the photoelectric effect, the Compton effect, and pair production. Does the initial kinetic ...
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Radiation dose delivered to a cavity of air
I have a cavity of air which is exposed to a radiation source that liberates a known amount of charge in the cavity ( in the form of ionization ). What theory should I use to model the situation so I ...
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Is the absorbed dose defined as a differential or a quotient?
The absorbed dose D is defined as
$D = \frac{dE}{dM}$ You can find this definition in numerious books.
However, when looking for calculation examples, the definition $D = \frac{E}{M}$ is used.
How ...
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Conditions for Bragg-Gray Cavity theory
The conditions for applying the theory are, first, that the cavity of material $g$ has to be small enough, so that the cavity does not affect the incoming radiation to the material surrounding the ...
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Difference between absolute dose and absorbed dose to water? (Radiotherapy)
In the calibration of clinical radiation devices, such as electron or photon beam generators, we are interested in the dose delivered to an air cavity. The air cavity is inside an ion chamber, which ...
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Why X-ray imaging base on photon counting is more quick than traditional energy integral detector?
photon counting based on detector can be used to x-ray imaging in industrial pubilc security. In traditional, people often use energy integral scintillation detecor to imaing object through x-ray. The ...
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What is the input of calculating signal noise ratio (SNR) and detective quantum efficiency (DQE) in estimation of imaging system?
In its definition, the signal noise ratio (SNR) is the ratio of the mean siganl to the standard deviation of the noise. However, for a given picture what is the noise? The detective quantum efficiency ...
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Is MRI permanent magnet sensitive to temperature?
My question is related to MRI machines that use a permanent magnet to generate their main magnetic field:
Are all permanent magnets used in such MRI machines sensitive to temperature, meaning does a ...
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Why is it in electrocardiogram (ECG), we talk about the voltage generated by depolarisation of the heart is a vector and not a scalar?
I'm asking to understand is the potential difference generated during depolarisation of the heart an exception to the rule that voltage is a scalar quantity? And if so, why?
I remember learning in my ...
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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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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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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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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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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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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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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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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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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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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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Bremsstrahlung radiation 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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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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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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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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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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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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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 ...
