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Physics chps 8-10

Question	Answer
A radiographic image is a result of	differential absorption of primary x-rays that interact with underlying tissue composition of the anatomic area of interest
beam attenuation occurs when	primary x-ray beam loses energy as it interacts with anatomic tissues
t/f: x-rays have the ability to eject electrons (ionization) from atoms within anatomic tissue	true
ionization	ejection of electrons from atoms
3 primary processes occur during x-ray interaction with anatomic tissue	absorption, transmission, scattering
scattering aka	compton
total absorption of the incoming x-ray photon is a result of	photoelectric effect
scattering of incoming x-ray photon is a result of	Compton effect
Scatter radiation reaching the IR provides...and creates...on the radiograpgh	no useful info; unwanted density/fog
Complete absorption of incoming x-ray occurs when it has enough energy to...	remove/eject an inner-shell electron
attenuation	reduction in energy of primary x-ray beam as it passes through anatomic tissue
Coherent scattering	incoming photon interacts with atom causing it to become excited, x-ray does not lose energy but changes direction
energy of coherent scattering	low energy, below diagnostic range
coherent aka	thompson or classical
coherent energy in kvp	10 kVp or less
Compton effect	loss of energy of incoming photon when it ejects an outer-shell electron from atom. remaining lower-energy photon changes direction and may leave anatomic part
compton aka	scatter, recoil
differential absorption	some of x-ray beam is absorbed in tissue and some passes through(transmits) the anatomic part
exit radiation	attenuated beam leaves patient
exit radiation composed of	transmitted and scattered radiation
photoelectric effect has enough energy to...	remove(eject) inner shell electron.
higher kVp = ...scatter	more
photoelectron	ejected electron resulting from total absorption of photon during photoelectric effect interaction
remnant radiation aka	exit radiation
Scattering	some incoming photons are not absorbed, but instead lose energy during interactions with atoms comprising tissue and change direction and may leave anatomic part
does transmission radiation interact with atomic structures	no
results in process of image formation, whereby x-ray beam interacts with anatomic tissue and a portion of beam strikes IR	differential absorption
loss of some energy from xray beam as it passes through tissue being imaged	attenuation
process of removing an electron from an atom	ionization
when xray photon strikes an atom within tissue being imaged and loses all of its energy to an inner shell electron of that atom, the photon is said to have been... and undergone...	absorbed, photoelectric interaction
coherent regarding direction and interaction	changes direction, no interaction
when xray photon strikes an atom within tissue and loses only part of its energy to an outer shell electron of that atom, the photon is said to have been...and undergone...	scattered, compton interaction
photoelectric deals with ... shell	inner
t/f:coherent changes direction	true
outer shell electron that is ejected during compton interaction is aka	secondary electron, compton electron
can compton effect strike the IR, resulting in useful anatomic info	no
t/f: compton interaction can occur within all diagnostic xray energies	true
T/F: any time tissue is hit = scatter	true
T/F: compton interactions are most likely to occur in soft tissue as compared to bone	false, density does not matter
T/F: density does not matter with compton interactions	true
meV of pair production	1.02 meV
meV of photodisintegration	10 meV
interactions of low energy xrays (below diagnostic range) with tissue include:	coherent scattering
xray beam that leaves patient in direction of IR is often referred to as	exit radiation
unwanted density on a radiograph due to scatter radiation	fog (washes out image)
At higher kilovoltage, ... photon interactions occur, resulting in...transmission	fewer, increased
if kVp goes up, mAs...	divide by 2
if kVp goes down...%, mAs...	15%, multiply by 2
efficiency of xray production increases as ... increase	kVp
penetrability of an xray beam	quality
beam quality is affected by	kVp and filtration
image contrast is affected by	beam quality/kVp
Half value layer of beam measures beam ...	quality
HVL is lowered by a decrease in ...	kVp
main purpose of added filtration	reduce patient dose
two primary forms of xray interaction in diagnostic range	compton scattering, photoelectric absorption
thompson aka	classical
outer shell electron is ejected and atom is ionized with ... interactions	compton
Xray interaction that involves ejection of K-shell electron	photoelectric
As kVp ... probability of photoelectric absorption ...	increases, decreases
complete absorption of incident xray photon with ... effect	photoelectric
... occurs only at very high energies used in radiation therapy and nuclear medicine PET imaging	pair production
only at energies above 10 MeV ... can take place	photodisintegration
attenuation is caused by	absorption and scattering
negative contrast agent	air
barium is a good contrast agent because	of its high atomic #
at energies below 40 KeV, predominant xray interaction in soft tissue and bone is	photoelectric absorption
Find following: 200 mA, .05 sec, 70 kVp ... mA, .01 sec, 80 kVp	200 mA x .05 sec = 10 mAs kVp increases by 15%, mAs/2 mAs = 5 500 x .01 secs=5 answer = 500 mA
Find following: 400 mA, .06 sec, 80 kVp 200 mA, ... sec, 80 kVp	400 mA x .06 sec = 24 answer = .12 sec
increase in kVp results in increase in	radiation quality
increase in mAs will increase ...	xray quantity
purpose of wedge filter	produce a uniform xray beam intensity at IR
purpose of adding filtration to an xray beam	remove low energy xrays
process that contributes most to the radiographic image	photoelectric effect
high kVp in chest xrays will increase/decrease contrast/patient dose or demonstrate spine?	decrease patient dose
radiographic quality is combination of	both visibility (photographic properties) and sharpness (geometric properties of recorded detail
visibility is aka	photographic properties
sharpness is aka	geometric properties
visibility of recorded detail is achieved by	proper balance of radiographic density and radiographic content
radiographic density -controlled by	the amount of oeverall blackness produced on image after processing -miliamperage and exposure time selected
a change in mAs results in direct change in	radiographic density
to maintain density, milliamperage and ... have an inverse relationship	exposure time
if mA increases, sec ... to maintain density	decreases
... changes the penetrating power of xray beam and has a direct effect on density	kilovotage
if kVp increase, scatter ...	increases
% of mAs needed to see changes on film	30%
% of kVp needed to see changes on film	15%
if SID increases, density ... -unless	decreases -compensating a change on film
changing SID and/or film-screen speed requires an adjustment in ... to maintain density	mAs
increased film speed = ... density and ... resolution	increased density, decreased resolution
radiographic contrast is combined result of -affects ... of recorded detail	IR contrast and subject contrast -visibility
a radiograph with few densities but great differences among them is said to have ... -described as ...	high contrast -short scale contrast
a radiograph with a large number of densities but little differences among them is said to have ... -described as ...	low contrast -long-scale contrast
kilovoltage has an inverse relationship with	radiographic contrast
high kVp will create an image with ... contrast and low kVp will create and image with ... contrast	low, high
increasing amount of scatter radiation reaching image receptor creates ... on image and will decrease ...	fog, contrast
exposure factors may need to be modified for ... patients	pediatric
increased collimation = ... density	decreased
thicker part = ... + ... decreased	density and contrast
film processing affects ... because ... is either too much or too little	contrast negatively, density
film speed increases, mAs ... and density ...	mAs decreases, density increases
kVp increases, contrast ... or more ...	decreases, more grays
total absorption	photoelectric affect
positive contrast agent	barium
more mAs = more ...	quantity/dose
if you decrease/increase distance, you need to decrease/increase	mAs
# of xrays in useful beam = ...	quantity
quantity proportional to	mAs
if distance decreases by 1/2, intensity goes up by ...	4 times
intensity is always ... when distance is decreased	squared
if filter thickness increases, intensity ...	decreases
if quantity is doubled, optical density...	goes up by 2 (20 mAs -> 40 mAs)
intensity is aka	kVp
optical density is aka	mAs
if kVp increase by 15%, mAs increases by ... %	100% 70 kVp, 20 mAs --> 80 kVp, 40 mAs
intensity formula	mAs1/mAs2 = d2/d1
beam quality affected by 2	kVp, filtration
beam quality NOT affected by ... 2	mAs, distance
image contrasted is affected by	kVp
quality improves by increased	beam filtration (eliminates lower energies)
if filtration is increased, quality ... and quantity ...	quality increases, quantity decreases
energy loss at coherent	none
coherent energy level	10 kVp or less
coherent interaction	capture and release
interaction where atom is ionized (outer shell kicked out)	compton/recoil
T/F: with compton interaction, electron retains most of its energy	true
direction compton can be directed	any angle
if kVp increases, there is going to be less of ... interaction	photoelectric (absorption)
2 interactions at a higher energy radiation than diagnostic	photodisintegration and pair production
photodisintegration occurs at ... energy level	10 meV
pair production occurs at ... energy level	1.02 meV
higher k-shell binding energy is directly proportional to what characteristic of atom	high atomic number
greatest mAs density in body	bone
image fog is caused by	compton
differential absorption depends on 3	kVp, atomic number and mAs
attenuation is caused by	absorption and scatter
transmitted means	radiation that went through patient
xrays transmitted w/o ... contribute to image	interaction
absorbed xrays contribute to ... radiation	scatter
spatial resolution improves with	less motion/geometric blur
speed = less ... and more ...	less detail, more noise
density	overall blackening of a radiograph
mAs determines the ... that wil be produced	quantity (number) of xrays
an increase in mAs will result in an increase in	density
the controlling factor for density is ... because ...	mAs, because it affects density but not any other radiographic qualities
... is directly proportional to density	mAs
in order to make a significant change in density, mAs should be increased/decreased by ...	increased by 100% or decreased by 50%
an increase in kVp will result in an ... in density because of	increase; more scatter
it only takes ... kVp to double density of a radiograph	15%
... determines intensity of xray beam	SID
an increase in SID will ... density	decrease
two types of filtrations	beam and compensating
beam filtration amount	2.5 Al
beam filtration filters	low energy xrays from xray beam
beam filtration above 2.5 Al will result in	a decrease in density
compensating filter is designed to compensate for	differences in tissue thicknesses
an increase in the thickness of a compensating filter will result in ... in density	decrease
increased of distance does not change ...	kVp
... distance = better detail	further distance
filtration measured in	millimeters of aluminum
amount of inherent filtration	.5 mm Al
inherent filtration found in	glass tube
anode heel effect	greatest intensity on cathode side of tube
body habitus	form of body
high contrast	radiograph with few densities but great differences among them
high contrast aka	short scale contrast
long scale contrast	radiograph with large number of densities but little differences among them
long scale contrast aka	low contrast
OID	object to distance distance
radiographic contrast can aka	grays
radiographic density	overall blackness produced on image after processing
short scale contrast	radiograph with few densities but great differences
short scale contrast aka	high contrast
SID	distance between source of radtiatin and IR
brightness aka	grays
changing kVp, etc. in digital imaging will only change contrast as it relates to	scatter radiation
few densities = ... scale contrast	short
several densities = ... scale contrast	long
total amount of filtration	2.5 mm Al
if using barium you need to adjust kVp by ... it	increasing
... kVp used with iodine contrast	70 or below
if filament temperature increases, there is ... mAs	more
square law	mAs1/mAs2 =d1(squared)/d2(squared)
too much filtration cuts down on ...	useful xrays
with hardening, only ... xrays come through	high quality
trough filtration used for	chest xrays
more distance needs more ... but ... doesnt change	mAs, kVp

Created by: dina11

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