What Is attenuation? correct answers gradual reduction in intensity of signal
How is attenuation caused? correct answers By the scattering and absorption of photons
When are collisions most likely? correct answers When the material is dense
More dense allow high or low x-rays out? correct ...
Medical Biophysics 2500 Quiz 1 || Already Passed.
What Is attenuation? correct answers gradual reduction in intensity of signal
How is attenuation caused? correct answers By the scattering and absorption of photons
When are collisions most likely? correct answers When the material is dense
More dense allow high or low x-rays out? correct answers Less x-rays out
Less dense allows high or low x-rays out? correct answers More x-rays out
What does full attenuation mean? correct answers x-rays don't reach the film/sensor, so the film
looks white
What does partial attenuation mean? correct answers some rays reach the film/sensor so the film
looks grey
What does no attenuation mean? correct answers all x-rays reach the film/sensor so the film
looks black
What does the attenuation coefficient (µ) describe? correct answers the fraction of a beam of x-
rays absorbed or scattered per unit thickness of the material
What are the 4 primary densities? correct answers 1. Bone
2.Water
3.Fat
4.Gas
What does the white in x-rays mean? correct answers That the material is the thickest
How do CT scans work? correct answers Uses multiple slices of x-rays that are stacked to create
a 3D image
Is there attenuation in CT scans? correct answers No. It is removed in order to see the finer
details
Why do we need more than 1 angle? correct answers Some angles can make the same object
look different or vice versa
How are Hounsfield numbers calculated? correct answers µvoxel - µwater /µwater
Are all organs equally sensitive to radiation? correct answers No
As x-rays are attenuated, where is the energy going? correct answers energy is delivered to the
tissues which are ionized and can lead to DNA damage
, Which organs are most sensitive? correct answers Organs with cells that divide rapidly
What is effective dose? correct answers Effective dose = equivalent dose x weighting factor
What is contrast resolution? correct answers The ability to distinguish many shades of gray from
black to white (intensity of image)
What are phantoms? correct answers specially designed objects to tune the performance of
various imaging devices
What are artifacts? correct answers Artificial image features which arise from physics of
imaging, problems with scanners and motion of the patient
Bones appear which in X-rays because...? correct answers They highly attenuated x-rays
CT numbers are also called...? correct answers Houndsfield units
True or false: Tissue appears darker than air in x-ray because of proton density? correct answers
False
True or false: An abdominal radiograph exposes the patient to less biologically effective
radiation dose than an abdominal CT scan correct answers True
True or false: The transmission of an x-ray through two attenuating materials is independent of
their order of placement in the x-ray beam correct answers True
True or false: Tissue appears darker than air in an x-ray because of the linear attenuation of x-
rays correct answers True
What are the strengths of x-rays? (3) correct answers 1. Cheap
2. Quick and available
3.good at distinguishing bone from tissue
What are the weaknesses of x-rays? (4) correct answers 1. some radiation
2.Attenuation shawdows overlap
3.Cant distinguish difference tissues
4. Many slices needed to see finer detail
What are the strengths of CT scans? (3) correct answers 1. Good at see overlying structures
2. View at different angles
3.Can image soft tissues
What are the weaknesses of CT scans? (2) correct answers 1. Exposure to radiation
2.Expensive
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