Questions tagged [medical-physics]
A field of applied physics dealing with the application of physics to diagnosis and treatment of diseases.
115
questions
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1answer
51 views
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,...
1
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1answer
16 views
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,...
0
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2answers
71 views
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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0answers
23 views
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, ...
1
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0answers
64 views
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 ...
2
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0answers
49 views
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 ...
2
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1answer
80 views
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 ...
3
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1answer
57 views
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 ...
0
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1answer
50 views
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 ...
1
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1answer
82 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 ...
-1
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1answer
62 views
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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3answers
278 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 ...
4
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1answer
54 views
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 ...
1
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1answer
34 views
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 ...
0
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1answer
31 views
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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votes
1answer
125 views
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 ...
1
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1answer
31 views
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 ...
1
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2answers
207 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 (...
0
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0answers
16 views
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 ...
2
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1answer
64 views
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 ...
0
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1answer
40 views
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 ...
0
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1answer
23 views
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 ...
0
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0answers
22 views
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 ...
2
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1answer
48 views
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 ...
2
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0answers
273 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....
3
votes
5answers
107 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
104 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 ...
0
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1answer
88 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 ...
13
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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 ...
7
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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?...
3
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3answers
646 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?
0
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1answer
33 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 ...
1
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1answer
1k 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 ...
2
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1answer
350 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 ...
2
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1answer
328 views
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 ...
0
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1answer
56 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 ...
0
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1answer
25 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 ...
0
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2answers
114 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 ...
0
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1answer
75 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 ...
0
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1answer
245 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 ...
1
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1answer
38 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 ...
1
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2answers
83 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 ...
0
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1answer
32 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 ...
1
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1answer
151 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 ...
0
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3answers
954 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 ...
0
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1answer
58 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 ...
2
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4answers
114 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-...
1
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1answer
185 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 ...
2
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1answer
304 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 ...
7
votes
2answers
2k 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 ...
