Physics Flashcards
1
Q
source of rad in XR tube
A
focal spot
2
Q
bc of line focus principle, the effective focal spot size decreases w decreasing?
A
target angle
3
Q
high capacity tube rotors revolve at?
A
10,000 rpm
4
Q
XR intensity (I) is lower on the anode side of the tube bc of the
A
heel effect
5
Q
cathode side of tube should be towards the _______ part of pt
A
thicker
6
Q
formula for heat units (HU) for a 3-phase, 6-pulse XR machine?
A
1.35 x kVp x mA x s
7
Q
tube failure can occur from?
A
long exposure T’s
8
Q
a dual focus tube has 2?
A
filaments
9
Q
ea tube has it’s own tube rating chart to show?
A
max exposure T’s
10
Q
the _______ is/are outside the glass envelope?
A
stators
11
Q
heel effect is caused by the?
A
anode angle
12
Q
the effective focal spot size is ________ the actual focal spot size.
A
smaller than
13
Q
projectile e-‘s travel from?
A
cathode to anode
14
Q
during an exposure most of the ______ energy of the projectile e-‘s is converted to _____
A
kinetic; heat
15
Q
the efficiency of XR production increases as _____ increases
A
kVp
16
Q
approx. ___ of the kinetic energy of the projectile e-‘s is converted to XRs at the target
A
1%
17
Q
e- interactions @ the inner shell of target atoms produce ________ rad
A
characteristic
18
Q
most of the heat generated at the target is due to?
A
outer-shell excitation
19
Q
production of heat @ anode is directly proportional to?
A
tube current
20
Q
useful characteristic XRs from tungsten targets are ______ XRs
A
K-shell
21
Q
characteristic K-shell XRs have an effective energy of _____ keV
A
69
22
Q
most XRs produced at the target are ________
A
bremsstrahlung
23
Q
at 55 kVp ______ of the XRs produced are bremsstrahlung
A
100%
24
Q
bremsstrahlung XRs are produced by _____ at the target
A
slowing e-‘s
25
characteristic XRs are produced by
released binding energy
26
quantity of bremsstrahlung rad increases proportionately w increased _____
mAs
27
an exposure taken at 100 kVp would have a continuous emission spectrum w a max energy of _____ keV
100
28
the ____ of an XR beam is higher when the peak of the emission spectrum is further to the ______
quality; right
29
an increase in mAs would _____ the ________ of the emission spectrum
increase; amplitude only
30
an increase in kVp would ______ the ________ of the emission spectrum
increase; amplitude & pos.
31
changes in ________ result in directly proportional changes in the amplitude of the emission spectrum
mA & T
32
the discrete portion of the XR emission spectrum would change pos. w a change in?
target material
33
amplitude of emission spectrum is _______ w a ________ generator than/as w a 3-phase generator
lower; single-phase
34
a 15% increase in kVp is = to
doubling mAs
35
how does added filtration affect the emission spectrum?
reduced amplitude and shift to R
36
Roentgens (or grays) is the measurement for XR?
quantity, exposure, & Intensity
37
of useful XRs in the beam defines the XR
quantity
38
standard XR machines produce about ____ mR/mAs at 70 kVp measured at 100cm SID
5
39
XR quantity increases in direct proportion to increases in?
mAs
40
if the distance from the source to the img (SID) is reduced by 1/2, how is the XR intensity at the img affected?
increased 4x's
41
if filter thickness is _____, then XR intensity is _____
increased, reduced; or reduced, increased (inversely proportional)
42
a 10% increase in kVp has _____ effect on XR intensity than/as a 10% increase in mAs
much greater
43
if XR quantity is doubled, the optical density (OD) on the finished radiograph will be?
increased by a factor of 2
44
if a tech changes the technique from 70 kVp @ 200 mAs to 70 kVp @ 400 mAs, the the XR intensity will _______ and optical density (OD) will _______
double, double
45
the inverse square law has the same effect on optical density (OD) and XR __________
intensity, exposure, & quantity
46
an increase of 15% in kVp is = to increasing mAs _________
100%
47
if the intensity of a 70 kVp exposure at 20 mAs is 100 mR, what would it be at 5 mAs?
25 mR
48
if an exposure is 50 mR at an SID of 40", what would the exposure be at an SID of 60"?
22.2 mR
49
XR intensity is proportional to?
kVp^2
50
penetrability of an XR beam is called XR _______
quality
51
an XR beam that should pass through dense tissue would have high?
penetrability & quality
52
a low quality beam would also have low?
penetrability
53
beam quality is affected by?
kVp & filtration
54
the half value layer (HVL) of XR beam is a measurement of beam?
quantity
55
img contrast is affected by?
beam quality & kVp
56
the HVL is lowered by a decrease in?
kVp
57
XR beam quality is improved by
increased filtration
58
main purpose os added filtration is to reduce
pt dose
59
added filtration will _____ beam quality and ______ beam quantity
increase, decrease
60
a compensating filter is used to create _____ optical density (OD) w a body part of ______ thickness
uniform; non-uniform
61
2 primary forms of XR interaction in the diagnostic range are
Compton scattering & photoelectric absorption
62
an incident XR interacts w an atom without ionization during __________
coherent scattering
63
an outer-shell e- is ejected & the atom is ionized w?
Compton interactions
64
which XR interaction involves the ejection of the K-shell e-?
photoelectric absorption
65
the scattered XR from a Compton interaction usually retains _____ of the energy of the indecent photon
most
66
Compton scatter is directed at (a) _______ angle from the incident beam
any
67
as kVp _____, the probability of photoelectric absorption ________
increases, decreases
68
there is complete absorption of the incident XR photon w
photoelectric effect
69
_________ only occurs at the very high energies used in rad therapy and in nuclear med PET imaging.
pair production
70
only at energies above 10 MeV can _______ take place
photodisintegration
71
when the mass density of the absorber is ______, it results in ______ Compton scatter
increased, increased; OR decreased, decreased (direct relationship)
72
K-shell binding energy increases w increasing ______
atomic #
73
what has the greatest mass density?
bone
74
img fog is caused by?
Compton scatter/interactions
75
bc of differential absorption, about ____ of the incident beam from the XR tube contributes to the finished img
0.5%
76
differential absorption is dependent on?
the kVp of exposure, atomic number (Z) of absorber, & mass density of absorber
77
attenuation is caused by?
absorption & scattering
78
Ba is a good contrast agent bc of it's
high Z
79
the use of contrast agents increases the amount of?
differential absorption, Compton Scatter, photoelectric absorption
80
a neg. contrast agent is?
air
81
XR transmitted without interaction contribute to
the radiographic img
82
Compton interactions, photoelectric absorption, & transmitted XRs ALL contribute to?
differential absorption
83
high kVp techniques reduce
pt dose
84
if 5% of an incident beam is transmitted through a body part, then 95% of that beam was
attenuated
85
smallest quantity of any type of electromagnetic rad
photon
86
velocity of all electromagnetic rad?
3 x 10^8 m/s
87
rate of rise and fall of a sine wave is called its
frequency
88
a hertz (Hz) is = to
1 cycle per sec
89
electromagnetic wave equation?
c=f⋋
90
the _____ of electromagnetic rad is constant
velocity
91
if the wavelength of a beam of electromagnetic rad increases by a factor of 2, then its frequency must
decrease by 1/2
92
the intensity of rad _____ in _____ proportion to the square of the distance of the object from the source
decreases, inverse
93
the reduction of rad intensity due to scattering & absorption is called ______
attenuation
94
velocity of light?
c = 3 x 10^8 m/s
95
max # of e-'s that can exist in an electron shell is calculated w?
2n^2
96
the shell # of an atom is called the
principal quantum #
97
the unit of measure of rad in the air is the
roentgen
98
the ______ is the unit used to describe the dose of ionizing rad received by a pt
rad
99
what unit is used to measure occupational dose?
rem
100
a measure od 10^-3 rads is a?
millirad
101
quantity of matter as described by its energy equivalence
mass
102
what has form/shape & occupies space
matter
103
energy of motion
kinetic
104
ability to do work
energy
105
rate of doing work
power
106
standard unit of mass in SI system?
kg
107
atoms & molecules are the fundamental building blocks of
matter
108
radio waves, light, & XRs are all ex's of ________ energy
electromagnetic
109
removal of an e- from an atom
ionization
110
ionizing rad is capable of removing ________ from atoms as it passes through matter
e-'s
111
biggest source of manmade ionizing rad exposure to the public
diagnostic XRs
112
Wilhelm Roentgen discovered XRs while experimenting w?
Crookes tube
113
radioactive material measured in
curies
114
which of the following is ionizing electromagnetic rad? (beta rays, gamma rays, radio waves, alpha rays)
gamma rays
115
Newton's 2nd law is written mathematically as?
F=MA
116
who invented fluoroscopic machine?
Thomas Edison
117
term "atom" was first used by the
Greeks
118
smallest particle that has all the properties of an element is a(n) ______
atom
119
periodic table of elements was developed by _______ in the late 19th century
Mendeleev
120
a pos. charged nucleus surrounded by neg. charged e-'s in well-defined orbits is the _______ model of the atom
Bohr
121
fundamental particles of an atom?
proton, e-, neutron
122
chem element is determined by the # of ____ in the atom
protons
123
an atom in a normal state has an electric charge of
zero
124
the binding energies or energy levels of e-'s are represented by their?
shells
125
when an atom has the same # of protons, but diff # of neutrons, its called an
isotope
126
when atoms of various elements combine, they form
molecules
127
an atom that loses/gains 1+ e- is an ____
ion
128
neutral atom has the same # of ______ & e-s
protons
129
innermost e- shell is
K-shell
130
atomic # symbolized w
Z
131
Aluminum has a Z of 13. how many protons does it have?
13
132
atomic # of molybdenum is 42 and the atomic mass # is 98. how many neutrons does it have?
56
133
only diff btw XRs & gamma rays is
their origin
134
the _______ is the least penetrating form of ionizing rad
alpha particle
135
gamma rays are produced in the _______ of the atom
nucleus
136
the T required for a quantity of radioactivity to be reduced to 1/2 of its original value
1/2 life
137
examples of particulate rad?
alpha & beta particles
138
what's common amongst all electromagnetic rad's?
their velocity
139
alpha particles are compared to a ________ nucleus
helium
140
the force that keeps an e- in orbit is the?
centripetal & centrifugal force
141
87º Fahrenheit is equal to _____ Celsius
Tc=5/9(Tf - 32)
Tc = 5/9 (87 - 32)
Tc = 30.5ºC
142
1/2 the distance from crest of a sine wave to the valley is the
amplitude
143
in a sine wave, the distance from one valley to another valley (or crest to crest) is
wavelength
144
of wavelengths that pass a point of observation per sec
frequency
145
in a sine wave, the shorter it's wavelength, the _______ its frequency
higher
146
the energy of a photon is directly proportional to its
frequency
147
the ___________ describes the relationship btw rad intensity and distance from the rad source
inverse square law
148
when white light goes through a prism, it gets
refracted
149
the study of fixed/stationary electric charge
electrostatics
150
fundamental unit of electric charge is
Coulomb
151
according to ________, electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance btw them
Coulomb's law
152
what states that "when an object becomes electrified, the electric charges are uniformly distributed throughout the object or on its surface"
electrostatic law #3
153
what states that "the electric charge of a conductor is concentrated along the sharpest curvature of its surface"?
electrostatic law #4
154
unit of electric potential?
volt
155
study of electric charges in motion is known as
electrodynamics
156
silicone & germanium are examples of
semiconductors
157
the property of some materials to exhibit no resistance below certain critical temp is illustrated as a concept known as
superconductivity
158
any property of the circuit that opposes/hinders the flow of the current is known as
resistance
159
what factors affect resistance?
material, diameter, length, & temp of conductor
160
which law states that the voltage across the total circuit or any portion of the circuit is = to the current multiplied by the resistance?
Ohm's law
161
if the e- flows alternatively in opposite direction, it is called
alternating current
162
______ is = to 1 ampere of current flowing through an electric potential of 1 volt
1 watt
163
any charged particle in motion creates
a magnetic field
164
the direction of the magnetic field is ________ to the motion of a charged particle
perpendicular
165
the ability of a material to attract the lines of magnetic field intensity is known as
magnetic permeability
166
degree to which various material can be magnetized is known as
magnetic susceptibility
167
what is considered as paramagnetic
MRI contrast
168
which transformer works under the principle of self-induction?
auto transformer
169
transformer law formula?
Vs/Vp = Ns/Np
170
a step up transformer has 500 coils at the primary & 7000 coils at the secondary. If 220 volt is supplied at the primary, how much voltage will be produced at the secondary?
3100v
171
the transformer loss due to the resistance of the wire is known as
Copper loss
172
a transformer has 600 coils on its primary side and 30 coils on its secondary side. what s the voltage on the secondary side when the primary side is 220 V?
11V
173
an electric current can be induced in a coil of wire if it is places near a(n)
electromagnet
174
the reduction of rad intensity due to scattering & absorption is called
attenuation
175
gamma rays are produced in the _____ of the atom
nucleus
176
photons w the highest frequencies have the
shortest wavelengths
177
like charges _____ and unlike charges _______
repel, attract
178
electrostatic force is _____ proportional to the distance btw charges and _______ proportional to the product of the charges
inversely, directly
179
charges on an electrified object are distributed
evenly throughout the object
180
on the surface of an electrified object the charges concentrate
on the sharpest curvatures
181
_______ is a source of a direct current
a battery
182
an alternating current (AC) is represented by a __________ line
sinusoidal
183
________ uses direct current? (hair dryer, toaster, microwave, flashlight)
flashlight
184
Ohm's law? (formula)
I = V/R
185
SI unit of magnetic field strength
tesla
186
what type of material can be made magnetic when placed in an external magnetic field?
ferromagnetic
187
if 3 resistors of 3 ohms, 4 ohms, & 6 ohms ea are connected in a series what will be the total resistance?
```
Rt = R1 + R2 + R3
Rt = 3+4+6
Rt = 13 Ohm's
```
188
if the current flowing through a circuit is 2A and the potential difference is 110V, what will be its resistance?
```
V = IR --> R = V/I
R = 110V/2A
R = 55 Ohm's
```
189
if a pt receives 100 mR standing at a distance of 72" from an XR source, what will be the rad dose to the pt if the pt is standing at a distance of 40"?
I1/I2 = D2^2/D1^2
100 mR/!2 = 40^2/72^2
1600I2 = 518400
I2 = 324 mR
190
what determines quality of XR beam?
kVp
191
what determines quantity of XR beam?
mA & exposure T
192
heating a coil of wire to produce e-'s is known as
thermionic emission
193
the flow of e- from filament to anode is known as
tube current
194
the alternating current can be converted to direct current w the use of a
rectifier
195
if a tech uses 70 kVp, 400 mA, & 1/10 s exposure T for a KUB, what will be the mAs produced?
40
196
what is located btw the auto-transformer & the step up transformer?
kVp meter
197
what transformer works under the principle of self-induction
auto transformer
198
what is located btw the step up transformer & XR tube?
rectifier
199
XR of L-spine needs 40 mAs. the tech wants to use the 200 mA station. what should be the exposure T?
0.20 s
200
a tech wants to use 110 kVp & 80 mAs for a L-spine. the tech wants to use 200 millisec exposure T. what mA station should be chosen?
400 mA
201
what is located at the secondary side of the step up transformer?
mA meter
202
two basic types of induction are _____ induction & ______ induction
self, mutual
203
a transformer converts
electrical potential to higher/lower intensity
204
the current to a transformer must be supplied by a(n)
AC source
205
variations in power distribution to the XR machine are corrected by the
line voltage compensator
206
the 1st component to receive power in the XR circuit is the
autotransformer
207
the ______ circuit provides e-'s for the XR tube current
filament
208
thermionic emission at the filament determines the _______ across the XR tube during an exposure
milliamperage
209
a step-down transformer is located in the ______ circuit
filament
210
the most accurate type of timer is the ______ timer
electronic
211
the AEC terminates the exposure when
sufficient rad reaches the IR
212
the ionization chamber is located
btw the pt & the IR
213
the f(x) of the photodiode is
to convert light to electric signal
214
the principal material used in the formulation of a solid state diode is
silicon
215
process by which alternating current is converted into pulsating direct current is termed
rectification
216
type of unit most likely to possess the smallest voltage ripple is a
high frequency unit (1%)
217
1 3-phase, 12-pulse wave formula has _____ ripple
4%
218
a high frequency wave form has ____ ripple
1%
219
a 3-phase, 6-pulse wave form has ____ ripple
14%
220
a single-phase wave form has ______ ripple
100%
221
a 3-phase, 6-pulse unit has an effective kV of about _____ of the peak kVp
86%
222
during capacitor discharge, the voltage falls at a rate of
1 kV/mAs
223
the e- cloud around the filament is known as
space charge
224
tungsten is the material of choice for the target bc?
high Z, high thermal conductivity, high melting point
225
according to line focus principle, the effective focal spot size is always ________ than the actual focal spot size
smaller
226
smaller the anode angle the ______ heel effect
larger
227
anode angle and effective focal spot size are
directly proportional
228
anode angle and heel effect are
indirectly proportional
229
to take advantage of the heel effect, the thicker body part must be positioned under the
cathode
230
the effective focal spot size is larger on the ______ side
cathode
231
the most frequent cause of abrupt tube failure is
e- arcing from the (open) filament
232
which kVp selection would result in the most scattered XRs in the img-forming beam? (90, 75, 60, 50)
90 kVp
233
decreasing kVp will increase
pt dose
234
contrast res is improved by? (3)
tight collimation, lowering kVp, pt compression
235
use of a compression device will increase _____
contrast
236
the use of ______ improves contrast & reduces pt dose
collimation
237
how can you improve img contrast w a heavy pt without increasing pt dose?
use tight collimation
238
img contrast improves when more of ______ rad is removed
scattered
239
a grid is constructed w _______ strips & _______ interspace material
radiopaque, radiolucent
240
a radiograph w a long scale of contrast will also have _____ latitude & ______ contrast
wide, low
241
grids are designed to remove scattered XRs before they reach
the IR
242
what is the grid ratio of a grid w 3-mm height, 0.025-mm thick pb grid strips, and 0.3-mm thick interspace material?
10:1
243
foreshortening is caused by a(n)
angled body part when the beam is perp to the IR
244
optical density (OD) is directly controlled by changing the _____
mAs
245
pt thickness affects img quality by affecting? (3)
magnification, rad contrast, focal spot blur
246
best way to min. magnification is to use a
long SID & small OID
247
subject contrast is affected by
pt thickness
248
3 primary factors influencing the intensity of scatter in the img-forming beam are
kVp, field size, & pt thickness
249
scatter rad increases as _______ increases
field size
250
the most commonly used beam restricting device is the ____________
variable collimator
251
the pos. beam limiting device (PBL) ensures that the XR beam is collimated to
the IR size
252
________ is the degree of difference in optical density (OD) btw areas of an img
contrast
253
amount of scatter absorption in a grid depends on? (3)
angle of scattered photon, height of the grid strips, & width of the interspace material
254
formula for grid ratio?
h/D
255
purpose of a grid is to achieve
improved img contrast
256
the interspace material in grids is made of ________
either aluminum or plastic (fiber)
257
grids generally have a frequency of _______ lines per in
60-110
258
the most critical consideration when using a crossed grid is ____________
alignment (positioning latitude)
259
how could contrast be improved on a bedside radiograph of a very large pt? (3)
use grid, lower kVp, use tight collimation
260
spatial res improves w decreased? (3)
screen/motion/geometric blur
261
radiographic ___________ is random fluctuation in the optical density (OD) of a radiograph
noise
262
the slope of the _______ portion of the characteristic curve shows the film contrast.
straight line
263
if 10% of the view box light is transmitted through an area of film, what is the optical density in that area?
1
264
a film w a characteristic curve showing a high slope would be useful when ________ is needed
high contrast
265
the 3 primary geometric factors affecting img quality are?
magnification, distortion, & focal spot blur
266
distortion can be reduced by
placing the object plane II to the IR
267
focal spot blur can be reduced by using a
small focal spot
268
XR img quality is improved when the ______ is increased.
SID
269
_______ is defined as the ability to img 2 separate objects & visually detect one from the other
resolution
270
higher speed img receptors generally produce img's w
increased noise
271
an img receptor w ________ can be used over a greater range of exposures
wide latitude
272
formula for optical density (OD)
OD = log10 (Io/It)
273
densities above 2.5 on a film are represented in the ________ portion of the characteristic curve
shoulder
274
sharpness of detail can be improved by increasing ______
SID
275
lowering kVp _____ pt dose & _______ img contrast
increases, increases
276
modern rad film base is made of ________
polyester
277
how thick is radiographic film base?
150-300 µm
278
crystals in film emulsion consist of ______ & ______
silver bromide, silver iodide
279
latent img formation occurs during film ________
exposure
280
a contaminant in the silver halide crystal creates the
sensitivity speck
281
the latent img can be seen
only after development
282
the latent img is made up of ______ atoms
silver
283
high contrast film contains ______ silver halide crystals (SHC) of _____ size
smaller, uniform
284
film is made w double emulsion to enhance film _______
speed
285
spectral matching is not a consideration when using
direct exposure film
286
storing film in very low humidity conditions can cause
static artifact
287
film should be stored at a temp of ______ or below & w humidity no higher than _______
68ºF; 60%
288
the rollers in the automatic processor are part of the _______ system
transport
289
replenishment of fixer & developer are controlled by the
microswitch
290
the undeveloped silver halide is removed from the emulsion during
fixing
291
name a rare earth phosphor?
lanthanum oxybromide
292
an increase in _____ will increase both beam quality & beam quantity
kVp
293
what are the 4 primary exposure factors?
kVp, mA, time, & SID
294
changes in kVp affect? (3)
OD, img contrast, img noise
295
an increase in mAs causes (an) _______ in beam quality & (an) ______ in beam quantity.
no change, increase
296
there is a direct relationship btw the quantity of XRs & the _____
milliamperage
297
if mAs are increased from 20 mAs to 40 mAs, the pt dose dose will
be doubled
298
beam penetrability is increased if ______ is increased
kVp
299
beam quality is improved when the _______ is increased, but ______ has no effect on beam quality.
kilovoltage, milliamperage
300
both beam quality & beam quantity are increased by
increasing kVp & changing from a single-phase to 3-phase voltage
301
to reduce img blur, what should tech do?
use shortest exposure T
302
when looking at exposure techniques, how can you tell which one gives the highest pt dose?
the one with the highest mAs
303
added filtration has the effect of _____ the beam quality & ______ pt dose
increasing, reducing
304
when all other exposure factors remain the same, changes in focal spot size result in ____ in beam quality and _____ in beam quantity
no change, no change
305
film can turn brown during storage due to a retention of ___________
ammonium thiosulfate
306
filtration is added to XR machines during manufacturing so that the required total of ___ mm Al equivalent filtration is achieved.
2.5
307
what kind of film is used in mammography?
single emulsion film
308
an exposure w an off-level grid will show grid cutoff
across the img
309
what is the formula for Bucky factor?
pt dose w grid/pt dose without grid
310
grid ratio is the _____ of the grid strips divided by the _____ of the interspace material
height, width
311
tree artifacts are caused by
friction
312
a high contrast XR has
short scale contrast
313
if a tech did a knee w a non-grid exposure using 10 mAs & wanted to use an 8:1 grid, what mAs should be used to produce a XR w the same density?
40
314
if a tech did a lat C-spine using a 12:1 grid & 10 mAs. if the tech is to be repeated using no grid, what should be the new mAs to produce a XR w the same density?
2
315
if a tech uses 24 mAs w a 16:1 grid, how much mAs should he/she use w a 6:1 grid?
12
316
which of the following technique chart causes less rad dose to the pt?
fixed kVp chart
317
the mAs values must be changed ___% to produce a perceptible change in OD.
30%
318
low humidity in the darkroom can cause
tree static
319
the undeveloped silver is removed from the emulsion during ______
fixing
320
Grid frequency
of pb strips per unit length (in/cm)
321
Types of grids used in rad
Linear & crossed
322
Most common grid type used
Linear
323
Which grid type gives more contrast?
Crossed
324
High or low ratio grid give more pos latitude?
Low ratio grid
325
Main disadvantage of II grid
Less contrast, removes less scatter
326
Main disadvantage of crossed grid?
Less pos latitude, absorbs more primary beam (May need to increase mAs to replace beam, which is more pt dose)
327
3 factors that control/affect detail
Screen/geometric/motion blur
328
As speed of IR increases, rad noise ______ & spatial res ______
Increases, decreases
329
Avg grid frequency used in rad depts?
25-45 lines/cm, 60-110 lines/in
330
4 most important characteristics of img quality?
Spatial res., contrast res., noise & artifacts
331
Primary control of contrast?
kVp
332
Primary control of OD
mAs
333
3 geometric factors
Magnification, distortion, focal spot blur
334
What controls detail?
Focal spot size
335
Detail is influenced by what
SID/OID & motion (screen/geometric/motion blur)
336
When are grid required?
Anatomical part 10+ cm or more than 60 kVp is needed
337
High/low grid ratio gives better contrast?
High (absorbs more scatter)
338
Grid is made w pb strips that are 16 mm long & separated by an interspacing material 2 mm wide. What's grid ratio?
8:1
339
How do you calculate the distance until grid cutoff?
D = SID/grid ratio
340
What happens to img contrast when grids are used?
Img contrast approx doubles
341
Random fluctuation in the OD of the img
Noise
342
Ability to img small objects that have high subject contrast
Spatial res
343
Factors that affect the visibility of detail
Img contrast & OD
344
Random nature by which XRs interacts w IR
Quantum mottle
345
What increases quantum mottle? How does it make img appear?
If produced w fewer XRs; grainy
346
How do you min quantum mottle (3)
High mAs, low kVp, slow IR
347
Ability to img 2 separate objects and visually distinguish btw the 2
Contrast res
348
Study of the relationship btw exposure intensity & blackness (density) on img
Sensitometry
349
Radiographic contrast is the product of ________ & ________
IR contrast & subject contrast
350
How do you calculate the slope of a characteristic curve
Calculate the avg gradient
351
Factors that affect magnification (4)
Size, shape, SID & OID
