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CTC Paul > War Machine RR > Flashcards

War Machine RR Flashcards

1
Q

Bremsstrahlung

A

Variable Distances of Interactions

Average Brems energy is equal to one third of the kVp selected

Continuous Spectrum of Energy

Majority of the Photons in X-Ray Beam

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2
Q

Characteristic Xrays

A

Incident Electron Eject an INNER SHELL
electron from the Target.

Energy of the characteristic photon is
specific to the shell and the target

Classic -69.5 K shell Tungsten

Small Minority of the Photons in the X-Ray Beam

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3
Q

X-Ray Production Device

Glass Enclosure / Envelope

A
  • Maintain a Vacuum

* Allow the amount and speed of the electrons to be controlled independently.

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4
Q

X-Ray Production Device

Cathode

A

• The Filament
• The place in the device where the
electrons enter

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5
Q

X-Ray Production Device

Focusing Cup

A

Help the electron beam strike the target in an acceptable size

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6
Q

X-Ray Production Device

A

Target of tungsten

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7
Q

Increased Target Atomic Number (Z)

A

Increases Quality and Quantity

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8
Q

Increased kVp

A

Increases Quality and Quantity

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9
Q

Increased mAs

A

Increased Quantity

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10
Q

Increased Voltage Ripple

A

Decrease in Quantity and Quality

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11
Q

Added Filtration

A

Increased Quality,

Decreased Quantity

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12
Q

H e e l E ffe c t

Smaller Angles

A

Worsening Heal Effect
(steeper angle = more abmpt intensity
change)

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13
Q

H e e l E ffe c t

Cathode Side

A

Strong Side

more intense side of the beam

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14
Q

H e e l E ffe c t

Larger Focus to Film Distance (FFD)

A

Less Heel Effect

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15
Q

H e e l E ffe c t

Smaller Film (field of view)

A

Less Heel Effect

Assuming same FFD

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16
Q

H e e l E ffe c t

Mammo - Cathode Side on the …

A

Chest Wall

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17
Q

Target (Anode) overview

A

Negative Charge - Repels Electrons

Made of Tungsten

Tungsten is Used Because:
Has a hiqh atomic
number (A 184, Z 74) -
this allows for more
efficient bremsstrahlunq
production

It wont’t melt (hiqh
melting temperature
(3422°c)

Rhenium is often added to tungsten: To prevent cracking at
high temperatures

Rotating Anodes will use a molybdenum stem: Molybdenum will not
transmit heat to the
thing that spins the
target disc (rotor and
bearing)
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18
Q

Filament (Cathode) Overview

A

Positive Charge - Attracts Electrons

Made of thin (0.2 mm) Tungsten wire

Tungsten is Used Because:
Has a hiqh atomic
number (A 184, Z 74)

Is a good thermionic
emitter (poops out lots
of electrons)

It wont’t melt (hiqh
melting temperature
(3422°c)

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19
Q

Area of Interest Cathode Side

A

Breast Chest Wall
CXR (AP) Abdomen (belly is denser than lungs)
Thoracic Spine (AP) Abdomen (belly is denser than lungs)
Femur (AP and lateral) Head (upper thigh is thicker)
Femur (AP and lateral) ** PEDS Knee (reduce dose to gonads)
Tibia / Fibula (AP and lateral) Knee (upper calf is thicker)
Humerus (AP and lateral) Shoulder (upper arm is thicker)
Forearm (AP and lateral) Elbow (upper forearm is thicker)

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20
Q

Loss of Characteristic X-Rays

A

If you drop the kVp below the

threshold for k shell electrons you are going to lose those characteristic peaks

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21
Q

X-Ray In te ra c tio n s

Compton

A

Major Contributor to Scatter / Fog

Involves the OUTER Shell Electron

Variable Energy Transfer

Does NOT Care About Z

Depends on Density

Dominates above 30 keV

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22
Q

X-Ray In te ra c tio n s

Photoelectric

A

Major Contributor to Image Contrast

Involves the INNER Shell Electron

“All or Nothing”

Depends on Z3

Dominates below 30 keV

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23
Q

G eometric Relationship

Magnification Increases With

A
  1. Greater Object to Detector Distance

2. Less Source to Object Distance

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24
Q

G eometric Relationship

Less Blur

A
  1. Small Focal Spot

2. Closer the object is to the detector

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25
Q

G eometric Relationship

More Blur

A
  1. Closer the source is to the image

2. More Magnification

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26
Q

DQE =

A

Measurement of efficiency
• High DQE = Low Dose
• Low DQE = High Dose

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27
Q

DQE is directly proportional to

A

MTF

MTF describes the relationship between
sharpness and resolution.

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28
Q

DQE is inversely proportional to

A

Signal to Noise Ratio

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29
Q

DQE is better at

A

Low spatial resolution

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30
Q

Approximate DQE:

A

DR = 0.45

Plain Film = 0.25

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31
Q

mAs Controls the

A

Radiographic Density

how black the image is

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32
Q

kVp Controls the

A

Radiographic Contrast
• Low kVp = High Contrast
• High kVp = Low Contrast

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33
Q

To achieve a noticeable difference in “density”

A

Increase mAs by 30%

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34
Q

To maintain density after decreasing mA by

50% you would

A

Increase kVp by 15%

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35
Q

4 cms o f tissue requires

A

Double the mA

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36
Q

Grids typically are NOT used with

A

Babies and Extremities

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37
Q

Cons to using a Grid

A

Increased Dose

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38
Q

Ways to Reduce Scatter (Improve Contrast)

A

1 - Collimate
2 - Compress the Part
3 - Lower kVp
4 - Grid / Air Gap

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39
Q

Pros of Collimation

A

1 - Increase Contrast
2 - Decrease Scatter
3 - Decrease KAP

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40
Q

Cons o f Collimation

A

1 - Smaller FOV

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41
Q

Scatter is Most Severe With

A
  • High kVp Technique
  • Large Field o f View
  • Thick Parts (or People)
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42
Q

D ig ita l - T riv ia S um m a ry

A

Digital imaging provides a wider dynamic range than film screen
Spatial Resolution of film is still probably superior.
The typical standard o f care for a digital display is 3 Mega-Pixels.

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43
Q

The primary factor influencing image contrast

in film systems

A

kvp

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44
Q

The primary factor influencing image contrast (in digital systems)

A

LUT

kVp still influences contrast, but digital
systems have a much wider dynamic
range.

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45
Q

Digital response curve

A
  • Digital has a linear response curve,

* Film has a curvilinear response curve.

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46
Q

Major determinant of spatial resolution with

digital images is

A

Pixel Size and Spacing (pixel pitch)

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47
Q

Digital

Decreased Pixel Pitch

A

Better Spatial Resolution

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48
Q

Digital

Increased Pixel Density

A

Better Spatial Resolution

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49
Q

Digital

Direct vs Indirect

A

Indirect (scintillators)
Xrays ==> Light = > Charge

Direct (photoconductors) =
X rays ==> Charge

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50
Q

Digital

Indict uses

A

Thallium doped Cesium Iodide (Csl)

“Scintillator”

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51
Q

Digital

Direct uses

A

Amorphous Selenium

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52
Q

Specific Factors Affecting the Spatial Resolution of CR

Laser Spot Size:

A

smaller is better

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53
Q

Specific Factors Affecting the Spatial Resolution of CR

Phosphor Pate Density / Thickness

A

More Thick = More Light Spreading = Less Resolution

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54
Q

Specific Factors Affecting the Spatial Resolution of CR

Sampling Frequency (Rate of Light Sampling):

A

Increasing the sampling frequency

results in a smaller pixel pitch with improves the spatial resolution.

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55
Q

Specific Factors Affecting the Spatial Resolution of CR

Imaging Plate:

A

You are supposed to use the SMALLEST plate size reasonable for the anatomic
area of interest. The reason is that for fixed matrix size CR systems using a smaller plate for a
given field of view improves your spatial resolution.

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56
Q

Specific Factors Affecting the Spatial Resolution of CR

Increasing x-rays will NOT improve

A

Maximum spatial resolution

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57
Q

Specific Factors Affecting the Spatial Resolution of DR

A
  • Spatial Resolution for DR is Superior to CR because the pixel detector is built into the DR flat panel -
  • Direct systems that avoid lateral dispersion of light have better spatial resolution
  • Spatial Resolution for Flat Panel Detectors is limited to the DEL (detector element); smaller detector elements = better spatial resolution.
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58
Q

Direct Conversion

A

Directly converts x-rays to electrical signal

Detector material is amorphous selenium

Signal does not “laterally disperse”, as the applied voltage separates the electrons and holes made by x-rays

Fill Factor is high (near 100%)

Fligher Detector Quantum Efficiency (DQE)

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59
Q

In d ire c t Conversion

A

X-Ray -> Light -> Electrical Signal

Phospor material is usually thallium doped cesium iodine

Light can scatter (worse with thicker crystal),
better if columnar structure is used.

Moderate fill factor (depends on size of pixel)

Moderate Detector Quantum Efficiency (DQE)

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60
Q

Mammo vs General Radiology

mammo

A

Low Energy 25-35 kVp

Most Common Anode is Moly

Low Tube Current 100mA

Long Exposure Times: 1000 ms

High Receptor Air Kerma lOO(micro)Gy

Beryllium Window

Small Focal Spot

Lower Grid Ratio: 5-1

High Optic Density

Brighter View boxes - 3000cd/m2

Longer Processing Times

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61
Q

Mammo vs General Radiology

general radiology

A

High Energy: 50-120 kVp

Most Common Anode is Tungsten

High Tube Current 500mA

Fast Exposure Times: 50 ms

Low Receptor Air Kerma 5 pGy

Pyrex Glass Window

Larger Focal Spot

Higher Grid Ratio 10-1

Low Optic Density

Darker View boxes - 1500cd/m2

Shorter Processing Times

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62
Q

Contact Mode - The Normal Mammogram

A

Breast is in direct contact with the bucky

The Grid is on

Larger Focal Spot - 0.3mm

Regular Paddle

Regular mA — around 100

Normal Exposure Time (around 1 second)

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63
Q

Magnifications - 1.5x - 2x (mammo)

A

Air Gap between Boob and Detector

No Grid - A ir Gap used to reduce scatter

Small Focal Spot 0.1mm
- need better spatial resolution

Smaller Paddle

Less mA - around 25

Increased exposure time (around 3
seconds)

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64
Q

Mammo Target Trivia

Larger or denser breasts

A

R h /R h
Mo anode can also be combined with an aluminum
filter, fo r a harder beam to penetrate denser breasts.

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65
Q

Mammo Target Trivia

“Intermediate” density breasts

A

Mo anode with Rhodium filter

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66
Q

Mammo Target Trivia

“Thin” breasts

A

Mo anode with Mo filter

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67
Q

Mammo Target Trivia

What Combination would you
“never” use?

A

Rh Target (21 kev) with a Mo Filter (20 Kev K edge)

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68
Q

PPV1

A

Abnormal Screener “Call Back”

3-8%

4.4%

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69
Q

PPV2

A

Recommended Biopsy (4 or 5)

15-40% (25*50% if palpable)

25.4%

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70
Q

PPV3

A

Biopsy Done
- Actual Cancer

20-45% (30-55% if palpable)

31.0%

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71
Q

Specific QA Tasks

A 
Processor QC Daily
Darkroom Cleanliness Daily
Viewbox Conditions Weekly
Phantom Evaluation Weekly
Repeat Analysis Quarterly
Compression Test Semi-Annually
Darkroom Fog Semi-Annually
Screen-Film Contrast Semi-Annually
Evil Overlord behind MQSA? FDA
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72
Q

Appropriate Target Range

for Medical Audit

A

Recall Rate 5-7%

Cancers/ 1000 Screened 3-8

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73
Q

The Privilege to Read a Mammogram

A 
During the last two years of
training you have to read
240
Formal Training Requirement 3 months
Documented Hours of Education 60
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74
Q

Brea st Phantom Trivia

A 
Breast Phantom is ?
• “The Average Breast”
• 50% Fat
• 4.2 cm Compressed
Phantom Dose
Should Be?
300 millirads (3 mGy)
Phantom Dose is
Performed?
WITH a Grid
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75
Q

General Radiology vs fluoro

general rads

A

mA 200-800
kVp 50 -120
Very short exposure times
Focal Tube Spot 1.0 -1.2mm

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76
Q

General Radiology vs fluoro

fluoro

A

mA 0-5
kVp 50 -120
Longer exposure times
Focal Spot 0.3-0.6mm

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77
Q

Last Image

Hold

A

The last frame of the
fluoroscopic loop is “held”

Low Dose

More Quantum
Mottle (less photons)

Spatial Resolution
around 2 Line Pairs
per mm

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78
Q

Spot Film

A

Cassette is placed in front of the detector - like a conventional X-Ray

Higher Dose

Less Quantum Mottle (increased mA, with
optimized kVp)

Spatial Resolution
around 3 Line Pairs
per mm

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79
Q

Digital Spot

A

Digital Equivialant to Spot

Film - minus the cassette

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80
Q

Geometric

Mag

A

To magnify something, you generally bring it closer to the x-ray source.

Mag = SID/SOD

Closer to the tube you get more radiation— and it doesn’t double, it squares (inverse square law in reverse).

Operator Dose also increases (scatter is not blocked as efficiently)

Causes Focal Spot Blurring (decreased resolution)

Creates an Air Gap - which reduces scatter

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81
Q

Electronic

Mag (Zoom)

A

Magnification that occurs from projecting a small field of view onto the matrix of detectors (change in minification gain).

With FPD - the image is enlarged digitally.

There is an increase in dose - driven by the automatic brightness control (typically 1.4x-2.0x per setting).

Increases Air Kerma

Does NOT Increase KAP

Does NOT Cause Focal Spot Blurring (resolution is improved)

Allows for Increased: Collimation

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82
Q

Fluoro Trivia

Best Position of the I.I. and X-ray Tube ?

A

X- Ray tube far away, with the I.I. close.

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83
Q

Fluoro Trivia

Where is the ideal place to stand ?

A

On the same side of the patient as the

imaging intensifier

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84
Q

Fluoro Trivia

Double the distance from the tube does what to dose ?

A

Decreases it by a factor of 4 (inverse

square law).

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85
Q

Fluoro Trivia

Normal Air Kerma Limit ?

A

87 mGy/min (10 Roentgens per min)

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86
Q

Fluoro Trivia

High Level Control (Really Fat Level Control) ?

A

176 mGy/min (20 Roentgens per min)

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87
Q

Fluoro Trivia

In “high level mode”, you must have ?

A

Audible or visual alarms (in addition to the
normal time alarm used in normal
fluoroscopy.)

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88
Q

Pulsed Fluoro

Conventional fluoro

A

long very low continuous mA.

• Pulse fluoro is pulsed (NOT continuous mA but instead pulse of higher mA).

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89
Q

Pulsed Fluoro

Pulse Fluoro is good for moving patients (Wiggling Babies)

A

Gives you sharper

images with less motion blur

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90
Q

Pulsed Fluoro

Pulsed Fluoro can reduce dose

A

when the frame rate is below 30 frame /second

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91
Q

Pulsed Fluoro

People always use a drop o f 30 to 15 frames per second as an example

A

because
that equals a dose reduction o f 30%. Math to get there isn’t important, just
understand it’s not a direct 1:1 thing. 50% reduction in pulse rate = 30 %
reduction in dose.

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92
Q

Pulsed Fluoro

Be careful how the question is worded

A

because a lower frame rate will have more
mA per individual pulse - but the overall mAs will be decreased relative to regular
fluoro below 30 frames per second.

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93
Q

Fluoro in IR Trivia

Best kVp to use with IV contrast is ?

A

Between 60-80 kVp (average beams

hit that k-edge nicely)

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94
Q

Fluoro in IR Trivia

IR uses relatively Small Focal Spots, and
Small Anode Angle Because ?

A

The need for maximum spatial resolution

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95
Q

Fluoro in IR Trivia

Grids ?

A

Usually
■ but Not with Peds and
■ Not with Extremities

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96
Q

Fluoro in IR Trivia

50% of the dose is delivered ?

A

in the superficial 3-5 cm of skin/fat
The depth o f this 50% depends on the kVp
andfiltration (higher kVp + Copper
Filtration = more penetration)

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97
Q

Fluoro in IR Trivia

“Dose Spreading”

A

The idea here is to change the angle of the
gantry (especially in a long case) in order
to spread the skin dose over a broader area
- decreasing the skin dose to any specific
location

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98
Q

Fluoro in IR Trivia

“Best Place to Stand”

A 
You should try and stand / work on the
image receptor side of the patient.
You are trying to avoid the large amount
of Compton scatter radiation produced
where the beam enters the patient.
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99
Q

Fluoro in IR Trivia

Magification will … ?

A

increase Air Kerma, but NOT KAP

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100
Q

Fluoro in IR Trivia

The dose (outside lead) standing 1 meter from
the patient is about “?” of the dose received by
the patient.
A

1/1000

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101
Q

General Radiology vs CT

A

mA 200-800 mA HIGH up to 1000
kVp 50-120 kVp 80-120
Focal Tube Spot 1.0 -1.2 mm Focal Spot 0.6-1.2 mm

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102
Q

CT Trivia

What kind of x-rays are used with CT?

A

Highly filtered, High kV

average energy 75 keV

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103
Q

CT Trivia

Bow Tie Filters do what ?

A
  • Compensate for uneven filtration,
  • Reduce Scatter,
  • Reduce Dose
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104
Q

CT Trivia

“Septa” is the CT term for ?

A

A Grid

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105
Q

CT Trivia

Minimal slice thickness is determined by ?

A

Detector element aperture width in a modem CT

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106
Q

CT Trivia

Pixel size =

A

Field of View / Matrix Size

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107
Q

CT Trivia

How do you improve spatial resolution ?

A

You need to make the pixels smaller (matrix larger).

Remember that Pixel Size = FOV/ Matrix

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108
Q

CT Trivia

Decreasing kV from 140 to 80 will do
what to the HU of a contrast enhanced
vessel?

A

It will increase.
*Increase is only seen with high “Z ” substances
such as Iodine. The benefit is not really there
with water, soft tissue, Calcium etc…
*It s a k-edge thing (Iodine k-edge 32, mean
photon energy o f 80 kVp is 44)

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109
Q

Pitch

o f “ l ” ?

A

There is no overlap

between slices.

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110
Q

Pitch

“Greater than 1” ?

A

This means the table
moved faster than the
beam, and you have gaps
betw’een your slices.

Spatial Resolution
Decreased

Dose Decreased

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111
Q

Pitch

“Less than 1 ” ?

A

This means the table
moved slow, and your
slices overlapped.

Spatial Resolution
Improved

Dose Increased

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112
Q

Window Level (or Center)

A

Thing you change for “Brightness”

This is the midpoint of the gray scale
display (the “center”). You want your
level at the attenuation of the thing you are interested in.

For example, if you are interested in bone
- you want a high level.

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113
Q

Widows Width

A

Thing you change for Contrast

This is selected based on what you are
comparing. If you are comparing things
with very different densities you want a
wide width. If you are comparing things
with very similar densities (example white
and gray matter), you want a very narrow
window width.

Above the upper limit of the width
everything will look white. Below the
lower limit of the width everything will
look black

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114
Q

A narrow (decreased) window width

A

Increases Contrast.

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115
Q

A wider (increased) window width

A

Decreases Contrast.

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116
Q

WL - “Brain” ?

A

W 80, L +40

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117
Q

WL - “Stroke” ?

A

W 3 0 , L +30

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118
Q

WL - “Lung’

A

W 1500, L - 400

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119
Q

WL - “Abdomen” ?

A

W 400, L + 50

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120
Q

WL - “Bone” ?

A

W 1600, L +500

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121
Q

Cardiac CT

Prospective:
“Step and Shoot”
- R-R interval

pro

A

There is reduced
radiation b/c the
scanner isn’t on the
whole time

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122
Q

Cardiac CT

Prospective:
“Step and Shoot”
- R-R interval

con

A

No functional
imaging.
Susceptible to
motion artifact.

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123
Q

Cardiac CT

Prospective:
“Step and Shoot”
- R-R interval

trivia

A

Always axial, not
helical.
You need a slow heart
rate (50-65 bpm)

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124
Q

Cardiac CT

Retrospective:
Scans the whole
time, then back
calculates

pro

A

Can do functional
imaging (evaluate
contraction and wall
motion)

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125
Q

Cardiac CT

Retrospective:
Scans the whole
time, then back
calculates

con

A

Higher radiation
(use of low pitch -
increases dose)

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126
Q

Cardiac CT

Retrospective:
Scans the whole
time, then back
calculates

trivia

A

none lol

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127
Q

Beta Blockers

A

Metoprolol Tartrate
(Lopressor) 2.5-5.0 mg IV

Regulate / lower heart rate
to less than 65 bpm for
prospective ECG-triggered
coronary CT

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128
Q

Beta Blockers

CI

A 
• SBP < 100
• Decompensated Cardiac
Failure
• Asthma on beta-aeonist
inhalers (albuterol)
• Active bronchospasm
• Severe COPD
• 2nd or 3rd-degree AV block
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129
Q

Nitroglycerine

A

0.8-1.2 mg glycerol trinitrate
• 5 mg isosorbide dinitrate

Dilates coronary arteries.
Improves visualization /
sensitivity etc… etc.. so on
and so forth.

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130
Q

Nitroglycerine

CI

A 
• Aortic stenosis (severe)
• Hypertrophic
cardiomyopathy
• Phosphodiesterase-5
(PDE-5) inhibitor — i.e.
boner pills: Viaura
(sildena///) and the others
“fils” like tadalafil etc...
for 48 hours prior to the
exam. Keep that dirtv dick
in your pants 48 hours prior
to exam.
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131
Q

Beta Blockers

reversal

A 
Antidotes / Treatment:
(1) Fluids — careful in CHF
(2) Atropine 0.5 mg IV - can
be repeated up to 3 mg.
(3) Glucagon - 50
micrograms/kg iv loading
dose, followed by a
continuous infusion of
1-15 mg/h
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132
Q

Spatial Resolution

Holding matrix size
constant and
decreasing FOV

A

This will decrease pixel size.

Spatial Resolution is Improved

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133
Q

Spatial Resolution

Holding matrix size
constant and
increasing FOV

A

This will increase pixel size.

Spatial Resolution is Degraded

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134
Q

Spatial Resolution

Optimal Reconstruction
Filter

A

Bone “sharp ” algorithm gives

a higher spatial resolution

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135
Q

Contrast Resolution

Holding matrix size
constant and
decreasing FOV

A

This will decrease pixel size.
Contrast Resolution is Degraded
(less photons per box)

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136
Q

Contrast Resolution

Holding matrix size
constant and
increasing FOV

A

This will increase pixel size.

Contrast Resolution is Improved.

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137
Q

Contrast Resolution

Optimal Reconstruction
Filter

A

“Soft tissue ” or “smooth ”
improves contrast resolution -
relative to bone

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138
Q

Contrast Resolution Trivia

What changes to kVp
and mA will maximize
contrast resolution ?

A 
Increased mA (less mottle, more signal).
Decreased kVp (less scatter, less noise). **especially in “small”
patients (kids), and contrasted exams.
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139
Q

Spatial Resolution Trivia

A “?” Focal Spot will
improve spatial
resolution

A

Smaller Spot = Better

Determines Spatial Resolution in the X-YPlane… sided to side.

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140
Q

Spatial Resolution Trivia

A “?” Detector Width
will improve spatial
resolution

A

Smaller Detector = Better
Determines Spatial Resolution in the Z Plane (the long axis or
Cranial Caudal direction)

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141
Q

Spatial Resolution Trivia

A “?” Pitch will
improve spatial
resolution

A

• Pitch < 1 improves spatial resolution,
• Pitch > 1 shitty spatial resolution
Pitch > 1 “increases slice sensitivity profde (SSP) ”. As the SSP
widens the slice thickness increases.

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142
Q

Spatial Resolution Trivia

Consequences of
decreasing the pitch ?

A

More Dose

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143
Q

CT Dose Related Trivia

Decrease kVp or
Decreased mA

A

Decreasing mA will decrease the dose
50% decrease in mA = 50% dose decrease

Decreasing kVp will decrease the dose
Quadratic relationship between kVp and radiation dose
Remember this is different than plain film because the skin
dose is spread via the rotating gantry

Decreasing kVp with compensatory increase in mA will
probably decrease the dose (although this is complicated -
a lotta ins, a lotta outs, a lotta what-have-yous).

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144
Q

CT Dose Related Trivia

Larger Pitch ?

A

Decreased Dose

50% increase in pitch = 50% dose decrease

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145
Q

CT Dose Related Trivia

```
Reconstruction Method
Iterative > Filtered Back
~~~

A

Iterative algorithms handle noise better — allows for a lower
dose technique to be used.

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146
Q

CT Dose Related Trivia

Acquired slice thickness?
*Z-Axis Resolution

A

Short Answer: Thinner = Maybe* Increase in Dose
Long Answer:
• Part A: Thinner slicer will have more noise. To compensate
for noise you may* be tempted to increase mA which would
increase dose.
• Part B: If you are increasing beam collimation to acquire a
thinner slice, this may* result in higher dose.
*In general CTDI is independent o f collimation, but this
can change at higher / narrow beam collimation settings.

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147
Q

CT Dose Related Trivia

Increased Rotational Time ?

A 
Less Dose (Faster rotation = less dose.)
Dose is proportional to both scan time and rotation time.
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148
Q

CT A r tifa c t R e la te d T riv ia

Ring

A

Call the manufacturer / “Scanner Mechanic”

The detector needs fix ed / replaced.

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149
Q

CT A r tifa c t R e la te d T riv ia

Partial Volume

A

Acquire thinner slices (decrease beam width , increase beam

collimation)

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150
Q

CT A r tifa c t R e la te d T riv ia

Stair Step

A

Acquire thinner slices (decrease beam width , increase beam collimation)
Reconstruction with overlapping intervals

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151
Q

CT A r tifa c t R e la te d T riv ia

Beam Hardening

A

Reposition the patient (arms up - etc…)

Increase the kVp

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152
Q

CT A r tifa c t R e la te d T riv ia

Metal

A
  • Increase the kVp (sometimes works).
  • Use thinner slices.
  • Certain interpolation software can help.
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153
Q

CT A r tifa c t R e la te d T riv ia

Photon
Starvation

A

• Automatic tube current modulation (increase mA). If you
increase the dose through the area of greater attenuation you can add enough photons to overcome this effect.
• Adaptive filtration can be performed to correct the
attenuation profile “smooth the data” in the high attenuation
portions.

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154
Q

CT A r tifa c t R e la te d T riv ia

Motion

A

• Tie the crazy patients down.
• Use a modem (fast) scanner ~ decrease scan acquisition time.
• “Over scanning” an extra 10% on the 360 rotation, with the
repeated portion averaged.
• Gating / Beta Blockers - cardiac.

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155
Q

U ltra so u n d R e la te d T riv ia

Reflection

A

Ultrasound energy gets reflected at a boundary between two tissues because of the differences in the acoustic
impedances of the two tissues.

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156
Q

U ltra so u n d R e la te d T riv ia

Refraction - Influenced by:

A

(1) Speed Change - which is based on tissue compression,

(2) the Angle of Incidence. “Snells Law”

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157
Q

U ltra so u n d R e la te d T riv ia

High Frequency Probes:

  • Scatter ?
  • Attenuation ?
A
  • More Scatter.

* More Attenuation

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158
Q

U ltra so u n d R e la te d T riv ia

Piezoelectric Materials
(PZT) are ?

A

• Functional part of the probe
• “The Crystal”
• Determines the frequency of the probe:
■ Lower frequency is seen with thicker crystals
■ Higher frequency is seen with thinner crystals

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159
Q

U ltra so u n d R e la te d T riv ia

High Q Dampening Block

A
  • Low Damping (high Q)
  • Narrow Bandwidth
  • For Doppler, to preserve velocity information.
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160
Q

U ltra so u n d R e la te d T riv ia

Low Q Dampening Block

A

• Heavy Damping (low Q)
• Broad Bandwidth
• Gives you high spatial (axial) resolution *fewer
interference effects and therefore more uniformity

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161
Q

U ltra so u n d R e la te d T riv ia

Matching Layer Function ?

A

Minimizes the acoustic impedance differences between

the transducer and the patient.

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162
Q

U ltra so u n d R e la te d T riv ia

French / Latin Sounding words
for:
• Near Zone:
• Far Zone:

A
  • The Near Field (Fresnel Zone)

* The Far Field (Fraunhofer Zone)

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163
Q

U ltra so u n d R e la te d T riv ia

Higher Transducer Frequency
does what to the near field ?

A

Higher Transducer Frequency = Longer Near Field.

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164
Q

U ltra so u n d R e la te d T riv ia

Focal Zone Maximizes “?”

A

lateral resolution

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165
Q

U ltra so u n d R e la te d T riv ia

How do you improve tissue
penetration (depth) ?

A

Use a lower frequency probe.

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166
Q

U ltra so u n d R e la te d T riv ia

How do you brighten up deep
structures ?

A

Start fucking around with the “TGC”
- Time Gain Compensation
Buzzword “Uniform brightness”

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167
Q

Im p ro v in g A x ia l

R e so lu tio n US

A

Shorter Pulses
(Smaller Spatial Pulse
Length)

Greater Damping “Low Q ”
(shorter pulses)

Higher Frequency Probe
(shorter wavelength)

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168
Q

Im p ro v in g L a te ra l

R e s o lu tio n US

A

Put the thing you want to
look at in the focal zone.
Phased array with multiple
focal zones

Increasing the “line density”
or lines per cm.

Higher Frequency Probe
(less beam spreading)

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169
Q

Im p ro v in g E le v a tio n

R e s o lu tio n US

A

Use a fixed focal length
across the entire surface of
the array (downside is
partial volume effects)

Use a Thinner Crystal
Minimize slice thickness -
done by phase excitation of
the outer to inner arrays

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170
Q

R e s o lu tio n T riv ia US

The stand off pad serves
what function?

A
  • Helps place superficial things in the focal zone

* This improves the lateral resolution

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171
Q

R e s o lu tio n T riv ia US

Axial Resolution
depends on ?

A

Spatial Pulse Length

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172
Q

R e s o lu tio n T riv ia US

Lateral Resolution
depends on ?

A

Transducer Element Width

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173
Q

R e s o lu tio n T riv ia US

Elevation Resolution
depends on ?

A

Transducer Element Height

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174
Q

R e s o lu tio n T riv ia US

Axial Resolution is
independent of ?

A

Depth

* Lateral Resolution changes with depth.

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175
Q

R e s o lu tio n T riv ia US

High Frequency Probes
improve ?

A

Axial Resolution
* Small wavelength allows for smaller spatial pulse length
Lateral Resolution
*Less beam spreading

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176
Q

R e s o lu tio n T riv ia US

Harmonics improves ?

A

Lateral Resolution

177
Q

Harmonics works by ?

A

Transmitting at one frequency and

receiving at another

178
Q

Compound Imaging works by ?

A

Using electronic steering of the ultrasound
beams from the transducer to image an
object in multiple different directions

179
Q

Harmonics are NOT produced in the ?

A

Near Field

they haven’t traveled fa r enough

180
Q

Harmonics can result in reduced ?

A

1 - Reverberation Artifact
2- Depth Penetration
(remember higher frequency attenuates -
so the beam is attenuated-faster).

181
Q

Compound Imaging can result in reduced ?

A

Posterior shadowing

182
Q

Compound Imaging will “?” the edges

A

Sharpen them

183
Q

Artifact

comet tail

A

harmonics - more visible

compounding - less visible

184
Q

Artifact

ring down

A

harmonics - n/a

compounding - reduced

185
Q

Artifact

reverberation

A

harmonics - reduced/eliminated

compounding - n/a

186
Q

Artifact

increased through transmission

A

harmonics - increased

compounding - n/a

187
Q

Artifact

acoustic shadowing

A

harmonics - increased

compounding - decreased

188
Q

Artifact

speckle noide

A

harmonics - reduced

compounding - reduced

189
Q

Artifact

A

harmonics -

compounding -

190
Q

Artifact

side lobe/grating

A

harmonics - reduced

compounding - n/a

191
Q

Thermal Index (T.I.) ?

A

Heating: this is the maximum temperature rise

in tissue secondary to energy absorption.

192
Q

Mechanical Index (M.I.) ?

A

Cavitation (Mechanical Damage):
this is how likely it is that cavitation will occur
considering peak rarefaction pressure and
frequency.

193
Q

What should be avoided with neonatal

imaging ?

A

Pulsed Spectral Doppler

194
Q

What should be used instead ?

A

M-Mode US (to document fetal HR)

195
Q

The T.I. should be ?

A

Under 1.0 (some sources say 0.7)

196
Q

Ideal Doppler Angle ?

A

The angle should be between 30- 60.

Theoretically the best angle is zero.

197
Q

Doppler Angle of 90 Degrees will ?

A

Look like no flow

198
Q

If you are looking for slow flow, you

should ?

A
  • Use a low pulse repetition frequency (PRF)

* Use Power Doppler

199
Q

Power Doppler does Not depend on ?

A

The Doppler Angle

200
Q

Power Doppler does Not provide

information on ?

A

The Direction of Flow

201
Q

Power Doppler will Not demonstrate

this artifact ?

A

Aliasing (both color and spectral can).

202
Q

Aliasing Artifact occurs when ?

A

the doppler shift is greater than a threshold called the

“Nyquist frequency”

203
Q

Aliasing Artifact Can be reduced by ?

A

• Increasing the scale
• Increasing the Pulse Repetition Frequency
(which will increase your Nyquist)
• using a lower frequency transducer or using a
doppler angle closer to 90 (increasing the angle)
(which will reduce the doppler shift)

204
Q

Artifacts from Multiple Echoes

Reverberation

A

Two parallel highly reflective surfaces - Multiple equidistantly spaced
linear reflections.

205
Q

Artifacts from Multiple Echoes

Comet Tail

A 
Two parallel highly reflective surfaces -
closer together (< 1/2 SPL) Triangle (comet) shaped
206
Q

Artifacts from Multiple Echoes

Ring Down Artifact

A

Fluid trapped between a tetrahedron of
air bubbles
Parallel band extending
posterior to a collection of gas

207
Q

Artifacts from Multiple Echoes

Mirror Image

A

Trapped behind a strong reflector This is almost always shown
with the liver on lung.

208
Q

IsotoPe

A

Same Number of Protons.

209
Q

IsotoNe

A

Same Number of Neutrons

210
Q

IsoBAR

A

Same MASS Number.

*Lift the barbell to put on some mass

211
Q

IsoMer

A

Same Number of Protons and Neutrons. But the energy
level is different — classic example is isoMeric Tc99M to
Tc99.

212
Q

H a lf Life

Physical

A

How long it takes to decay to 1/2 activity. You’ll need to memorize these.

213
Q

H a lf Life

Biologic

A

How long it takes your body to shit, piss, cry, sweat out the tracer. They have
to provide you with this number

214
Q

H a lf Life

Effective

A

Takes both Physical and Biologic into account (it’s always less)
1/Effective = 1/Physical + 1/Biologic

215
Q

Tc - 99m

A

Analog:

Energy:“Low” - 140

Physical half life: 6 hours

216
Q

Iodine-123

A

Analog:Iodine

Energy: “Low” - 159

Physical half life: 13 hours

217
Q

Xenon -133

A

Analog:

Energy: “Low” - 81

Physical half life: 125 hours
(biologic tl/2 30 seconds)

218
Q

Thallium - 201

A

Analog: Potassium

Energy: “Low”
- 135(2%)
- 167(8%)
use 71 201 Hg
daughter x-rays

Physical half life: 73 hours

219
Q

Indium -111

A

Analog:

Energy: “Medium”

  • 173 (89%),
  • 247(94%)

Physical half life: 67 hours

220
Q

Gallium - 67

A

Analog: Iron

Energy: Multiple:

  • 93 (40%),
  • 184(20%),
  • 300(20%),
  • 393 (5%)

Physical half life: 78 hours

221
Q

Iodine -131

A

Analog: Iodine

Energy: “High” - 365

Physical half life: 8 days

222
Q

Fluorine -18

A

Analog: Sugar

Energy: “High” -511

Physical half life: 110 mins

223
Q

Cobalt -57

A

Analog: Used for Extrinsic
Field Uniformity
QA (Flood)

Energy: “Low”

  • 122
  • 136

Physical half life: 270.9 days

224
Q

Germanium 68/

Gallium 68

A

Analog: Used for PET QA

Energy: “High” - 511 (via Ga)

Physical half life: 270 days - Ge
68 minutes - Ga

225
Q

Treatment Radionuclides
Half Life

Strontium 89

A

50.5 DAYS

14 days in bone

226
Q

Treatment Radionuclides
Half Life

Samarium 153

A

46 Hours

227
Q

Treatment Radionuclides
Half Life

Radium 223

A

11 Days

228
Q

Treatment Radionuclides
Half Life

Yttrium 90

A

64 Hours

229
Q

Cardiac Radionuclides
Half Life

Rubidium 82

A

75 seconds

230
Q

Cardiac Radionuclides
Half Life

Nitrogen 13

A

10 mins

231
Q

Beta Minus

A 
Lots of Neutrons
Not Enough Protons
Generate a Beta Particle
(Electron)
ISO BA R IC transition
232
Q

Beta Plus

A

Lots of Protons
Not Enough Neutrons
Generate a Positron
has 1.02 MeV

233
Q

Electron

Capture

A

Lots of Protons
Not Enough Neutrons
Does NOT require
1.02MeV

Captured “sheath”
electron and proton
merge to form a neutron.
Can produce gamma
photons when coupled
with an isomeric
transition
234
Q

Alpha

A 
Heavy Unstable
Atoms
Omits a heavy Helium
nuclei (2 protons, 2
neutrons)
235
Q

Collimator Type

Parallel Hole

A 
Size of image is NOT affected by
distance. The FOV is constant with
distance.
You want the collimator and
detector as close as possible to the
patient for the best spatial
resolution (this is affected by
distance).
236
Q

Collimator Type

Parallel Hole Image size and used for

A

Imase Size =
- 1:1 - Equal to Patient
“The work horse ”

237
Q

Collimator Type

Pinhole

A 
Distance Sensitive - amount of
magnification decreases as object
gets farther from the collimator. If
the object is as far from the pinhole
as the pinhole is the camera crystal
there will be zero magnification.
The FOV increases with distance.
238
Q

Collimator Type

Pinhole Image size and used for

A 
mage Size =
- Magnifies and Inverts
Usedfor:
- Thyroids and other small parts
(hip joint, peds, etc...)
- Large objects get distorted (front
is magnified more than back).
239
Q

Collimator Type

Converging

A

Distance Sensitive - amount of
magnification increases as object
gets farther from the collimator.
The FOV decreases with distance.

240
Q

Collimator Type

Converging Image size and used for

A 
Image Size =
- Magnifies without inverting
Usedfor:
- Multiple choice questions.
- Sometimes small body parts
241
Q

Collimator Type

Diverging

A

Distance Sensitive - amount of
minification increases as object gets
farther from the collimator
The FOV increases with distance.

242
Q

Collimator Type

Diverging Image size and used for

A 
Image Size =
- “Minifies” , Takes a large object
and makes it small.
Usedfor:
- Large Body Parts (lung scan with
mobile gamma camera in the ICU)
243
Q

Parallel Hole Factor

Septa Length

A 
Long Septa:
- Low Sensitivity (Noisy)
- High Spatial Resolution
Short Septa:
- High Sensitivity
- Low Spatial Resolution
244
Q

Parallel Hole Factor

Hole Diameter

A 
Wider Hole:
- High Sensitivity
- Low Resolution
Narrow Hole:
- Low Sensitivity
- High Resolution
245
Q

Parallel Hole Factor

Septa Thickness

A 
Thick Septa:
- Less Penetration
- Less Available space for
holes (Less Sensitivity)
Thin Septa
- More Penetration (Blur)
- More Available space for
holes (More sensitivity)
246
Q

Q/A on the Dose Calibrator (Ionizing Chamber

Consistency

A

Daily
Should be within 5% of
computed activity

Checked with reference
sources

247
Q

Q/A on the Dose Calibrator (Ionizing Chamber

Linearity

A

Quarterly

Accurate readout for
activities over the whole
range of potentially
encountered activities

Checked with a large
activity of Tc (around
200mCi) and decaying it
down to less than the
smallest activity you
would measure for use.
248
Q

Q/A on the Dose Calibrator (Ionizing Chamber

Accuracy

A

Annually

Standard measurements
of radiotracers measured
and compared to what the
activity should be

Standard Energy Sources:
• Low (Co-57)
. Medium (Cs-137)
. High (Co-60)

249
Q

Q/A on the Dose Calibrator (Ionizing Chamber

Geometry

A

Installation and any
time you move the
device

Correction for different
positioning and size

Different volumes of
liquid (Tc-99m)

250
Q

G e ig e r - M u lle r C o u n te r

A

Detects Ionizing Radiation (alpha, beta, gamma)

Detects Ionizing Radiation (alpha, beta, gamma)

Great for Low-Level Radioactive Survey

Terrible for Very High Radiation Fields
(“Dead Time”)

251
Q

Ionizing chamber

A

For measuring dose rate.
Used with higher rates.

Lower Sensitivity

Stable across a wide voltage range - Excellent
for accurate estimates (or exposure).

252
Q

“Pocket Ionization Detector”

A

uses a miniature ionization chamber.
They give you real-time estimated dose, but must be charged and zero’d
prior to use. These are not used anymore - which makes them high yield.

253
Q

“Solid State Dosimeter ”

A

Accumulated dose or rate can be read real

time with LCD display.

254
Q

“Film Badge ”

A

Uses a thin metallic filter with a radiosensitive film.
The degree of darkening (relative optic density) corresponds with dose.
They can be damaged by temperature, humidity, etc…

255
Q

“Optically Stimulated Dosimeter”

A

the film badge. Chips /

Strips are placed under a filter.

256
Q

Survey Meters

A

G-M and Ionization Detectors - discussed on prior page

257
Q

Well Counter

A

Basically a small gamma camera, with one PMT. Susceptible to “dead
time” at counts over 5000 per second. Good for urine and blood
samples. Good for “wipe test” samples.

258
Q

Dose Calibration
& Automated Dose
Injection Systems

A

Used to measure radiopharmaceuticals.

259
Q

Thyroid Uptake

Probe

A

Compares counts from region over the thyroid to a calibrated capsule of
the same radionuclide. The probe is a cylindrical scintillator detector
attached to a PMT. A positioning guide keeps the distance constant. A
Chi-Squared test can be used to evaluate the reliability of consistent
operation.

260
Q

Intra-operative

Probes

A

Used for lymphoscintigraphy

261
Q

10CFR part 19

A

Nwootrik,c eerss,. instmctions, and reports to workers

…i nspecti. ons „

262
Q

10 CFRpart 20

A

Standards for protection against radiation,

“radiation protection”

263
Q

10CFR part 35

A

Medical use of by-product material.

“human use of
radioisotopes”

264
Q

Regulations
Major Spill

Tc-99m

A

Greater than 100 mCi

265
Q

Regulations
Major Spill

Tl-201

A

Greater than 100 mCi

266
Q

Regulations
Major Spill

In-111

A

Greater than 10 mCi

267
Q

Regulations
Major Spill

1-123

A

Greater than 10 mCi

268
Q

Regulations
Major Spill

Ga-67

A

Greater than 10 mCi

269
Q

Regulations
Major Spill

1-131

A

Greater than 1 mCi

270
Q

Regulations
Major Spill

steps

A
  1. Clear area.
  2. Cover spill with absorbent paper.
    Do NOT clean it up.
  3. Clearly indicate boundaries of spill
    Limit movement of contaminated
    pet sons
  4. Shield source if possible
  5. Notify the Radiation Safety Officer
    immediately
  6. Decontaminate persons
271
Q

Regulations - General Public

Annual Dose limit

A

100 mrem

272
Q

Regulations - General Public

“Unrestricted area”

A

Not greater than 2 mrem per hour

273
Q

Regulations - General Public

“Restricted Area”

A

Defined as:

“Any place that receives a dose greater than 2 mrem/h”

274
Q

Radiation Area

A

Any place you could get 0.005 rem (0.05mSv) in 1 hour at 30cm

275
Q

High Radiation Area

A

Any place you could get O.lrem (lmSv) in 1 hour at 30cm

276
Q

Very High Radiation Area:

A

Any place you could get 500 rads (5 gray) in 1 hour at 1 meter

277
Q

Regulations - NRC Occupational Exposure Dose Limits

Total Body Dose per Year

A

5 rem (50 mSv)

278
Q

Regulations - NRC Occupational Exposure Dose Limits

Dose to the Ocular Lens per year

A

15 rem (150 mSv)

279
Q

Regulations - NRC Occupational Exposure Dose Limits

Total equivalent organ dose

A

50 rem (500 mSv)

280
Q

Regulations - NRC Occupational Exposure Dose Limits

Total equivalent extremity dose per year

A

50 rem (500 mSv)

281
Q

Regulations - NRC Occupational Exposure Dose Limits

Total Dose to Embryo/fetus over entire 9 months

A 
0.5 rem (5 mSv)
I f the fetus has already got 5 mSv at
the time o f declaration - the NRC
states you can get 0.5 mSv more fo r
the remainder o f the pregnancy.
282
Q

Regulations - NRC Occupational Exposure Dose Limits

units

A

1 rad = 1 rem, 1 rad = 0.01 Gy
1 mSv =100 mrem = 0.1 rem

1 rad = 1 rem
1 rad = 0.01 Gy
1 mSv =100 mrem = 0.1 rem

283
Q

Reportable vs Recordable

(wrong drug, wrong dose
- by 20%, wrong pt, etc…

Whole Body Dose > or < 5 rem
Single Organ Dose > or <50 rem
greater

A

RePORTabie Event

Call NRC within 24 hrs
Write NR C Letter within
15 days
Present your testicles to
the NR C for castration
(within 30 days)
Notify Referring Doctor
within 24 hours
Notify the Patient (or let
referring do it)
284
Q

Reportable vs Recordable

(wrong drug, wrong dose
- by 20%, wrong pt, etc…

Whole Body Dose > or < 5 rem
Single Organ Dose > or <50 rem

lesser

A

ReCORDable Event

Record Locally
Institutional Review

285
Q

Receiving, Storing, and Disposing of Radioactive Material

A

Within 3 hours of receipt (3 working hours) you (the tech) has to survey packages when they
arrive. This process involves a GM counter test at the surface and 1 meter from the package, as
well as wipes of all surfaces of the package (>6600 dpm/300 cm2 is not allowed).
Next Step => Contact both the shipper and the NRC if beyond allowable limits

286
Q

Package labe: white 1

A

no special handling

Surface dose rate <0.5 mrem/hr, 1 meter 0 mrem/hr

There is no T.I.
(Transportation Index)
because the rate at 1 meter
will be so low.

287
Q

Package

Label: yellow 1

A

special handling required

Surface dose rate <50 mrem/hr,
1 meter < 1 mrem/hr

T.I. < 1.0 mR per hour

288
Q

Package label yellow 2

A

special handling rquired

Surface dose rate < 200 mrem/hr,
1 meter < 10 mrem/hr

T.I. >1.0 mR per hour

289
Q

Common Carriers

A

A truck that carries regular packages
and radioactive material

T.I. should not exceed
10 mR / per hour.
Surface rate should not be
more than 200 mR

290
Q

Multiple Packages

A

Those shipped together
Sum should NOT exceed
50 mR.

291
Q

Radionuclide
Purity

What is it?

A

How much Mo
in the Tc ?
“Moly
Breakthrough ’’

292
Q

Radionuclide
Purity

Tested?

A 
Tested in a dose
calibrator with lead
shields;
Looking for 700
keV photons of
Moly (remember Tc
is only like 140)
293
Q

Radionuclide
Purity

Limit?

A

0.15 microcuries of Mo per

1 millicurie of Tc

294
Q

Chemical
Purity

What is it?

A

How much A1
in the Tc ?
“Aluminum
Breakthrough

295
Q

Chemical
Purity

Tested?

A

Tested with pH
paper (Color
Indicator Paper, or
Paper Strip Test)

296
Q

Chemical
Purity

Limit?

A 
<10 micrograms A1 per 1ml
Aluminum Contamination
Can Be Shown Two Ways:
1. Liver Spleen Scan + Luna =
Aluminum Contamination
2. Tc scan + Liver Activity =
Aluminum Contamination
297
Q

Radiochemical
Purity

What is it?

A

How much Free

Tc?

298
Q

Radiochemical
Purity

Tested?

A

Tested with Thin
Layer
Chromotography

299
Q

Radiochemical
Purity

Limit?

A 
. 95% Na99mTc04
• 92% for 99mTc sulfur colloid
(MAA)
• 91% for all other Tc
radiopharmaceuticals
Free Tc Classically Shown as:
- Gastric uptake
- Salivary Glands uptake
- Thyroid uptake
300
Q

Tc - Moly Generator operates with “Transient Equilibrium ”

A

which occurs at 4 daughter

half lives — Remember the t 1/2 of Tc is 6 hours. (4 x 6 = 24 hours)

301
Q

2D PET vs 3D PET

2d

A

Septa collimator (reject scatter)

Less Sensitivity

Fewer True, Scattered and Random
Coincidences

Smaller FOC for true coincidences

More Tracer

302
Q

2D PET vs 3D PET

3d

A

NO Septa Collimator
(fast coincidence detector)

More Sensitivity

More True, Scattered and Random
Coincidences

Larger FOV for true coincidences

Less Tracer

303
Q

Attenuation Correction pet

A

ligth skin and light lungs

304
Q

Uncorrected pet

A

hot skin andhot lungs

305
Q

SUV Trivia

A

Monstrously Obese Fatties SUVs are overestimated
Delayed Scan Timing
In other words, if you did “delays” you would get higher FDG values.
High Blood Glucose SUVs are Lower
Smaller Tumor (or object of interest)
Smaller than 1 cm = Lower SUV.
IV Dose Extravasation Dose Extravasation = Lower SUV
Iterative reconstruction More iterations the higher the SUV.

306
Q

Dose units pet

Exposure
C/kg

A

Charge (C) in the air created divided by the mass (kg) of that
air.

307
Q

Dose units pet

Absorbed Dose
Gy

A

1 Gy = 100 rads

Energy deposited per kilogram of material (J/kg = Gy),
Organ Dose =
Total energy to that organ / Total mass of the organ.

308
Q

Dose units pet

Equivalent Dose
Sv

A

Absorbed dose of different types of radiation creates
different levels of biologic damage (thus measured in
Sv). A weighting factor is used to adjust the value. For
example, an alpha particle can do more damage than an
electron.
EqD = Dose x Weight Factor
Weight Factor = for x-rays and gamma rays this is 1,
Weight Factor = for alpha particles it’s 20.

309
Q

Dose units pet

Effective Dose
Sv

A

Closest measure of cancer risk,
since it considers both
radiation and tissue type.

This takes into account whether radiation has been
absorbed by the specific tissue. In other words, you are
taking into account the type of radiation and the
variable sensitivity of the organ / body part.
Bone Marrow and Bowel are Radiosensitive (higher
wT). The Brain is relatively insensitive (lower wT).
If all the dose is absorbed then 1 Gy = 1 Sv. If you are
dealing with organs or specific body parts you have to
use a “tissue weighting” conversion factor.
EfD = Equivalent Dose x Tissue Factor “wT”

310
Q

Deterministic Effects

A

Deterministic Effects
Severity is dose related
Does Not include Cancer Risk

311
Q

Stochastic Effects (“Random”)

A

Has NO threshold
Probability of effect increases with dose
Severity is NOT dose related
Includes heritable effects and carcinogenesis
(NOT cell killing)

312
Q

Dose Units - Fluoro

Air Kerma
AK
(Gy/min)

A 
Measures the intensity of the
x-ray beam.
Absorbed dose in Air
Energy transfer from the primary
interaction of photons on tissue
atoms. NOT the secondary
production of scatter electrons
which also contribute to the
overall dose.
Relates to Deterministic Risk
Decreases with distance from the
x-ray source — inverse square.
313
Q

Dose Units - Fluoro

Kerma-Area
Product (KAP
Gy-cm2)

A 
Accounts for both exposure
and area exposed - best thought
of as “the whole beam.”
KAP = Dose “AK” x Cross Sectional Area
Relates to Stochastic Risk
Independent of the source
distance. You can measure it
at any point along its path and
it will be the same.
Collimation will DECREASE
the KAP.
314
Q

Dose Units - Fluoro

Cumulative Air
Kerma (CAK
Gy)

A

Total of all the AK values for
individual exposures,

Described at a specific
interventional reference point:
15 cm toward the x-ray tube
measured from the isocenter of
the fluoroscopy machine.
315
Q

Dose Units - CT

CTDI
“CT Dose
Index”
mGy

A

This is the radiation dose,
normalized to beam width

CTDI numbers are based on
phantoms. The body phantom
is 32 cm in diameter.
If the patient is larger (a big fat
pig) than the phantom, then
dose is over estimated.
If the patient is smaller (peds)
than the phantom, then dose is
under estimated.
316
Q

Dose Units - CT

“Weighted
CTDI”
mGy

A

This is 1/3 the central CTDI + 2/3
the Peripheral CTDI (expressed in
mGy)

317
Q

Dose Units - CT

“Volume
CTDI”
mGy

A 
This is obtained by dividing
weighted CTDI by the Pitch.
2/3 CDTIp + 1/3 CTDIc / pitch
“Reference Dose ”
set by the ACR at 75 percentile
CTDI vol:
• 75mGy for Head,
• 25 mGy for Adult Abd,
• 20 mGy for Peds Abd (5 year old)
318
Q

Dose Units - CT

DLP
“Dose Length
Product”
mGy - cm

A

CTDI - Vol x the length of the
scan in cm.
It is appropriate to add DLP from
series to series.

319
Q

Dose Units - CT

“Effective
Dose” fo r CT
mSv

A

Effective Dose = k x DLP.
Remember that “k” is a body
part constant.

320
Q

This vs That: Direct vs Indirect Radiation

Direct Radiation
minority

A

Acts on DNA

Most likely for High
LET Radiation
(unusual in x-ray
imaging)

321
Q

This vs That: Direct vs Indirect Radiation

Indirect Radiation
majority

A 
Acts on water in the
cytoplasm, creating
free radicals - which
in turn damage the
DNA

More likely for Low
LET Radiation

This process is
promoted by the
presence of oxygen

322
Q

Acute
Radiation
Syndrome

Bone Marrow

A

Dose Needed - > 2 Gy

Dose Needed
“Rounded For
Memory” - 5 Gy

Latent Period -1 -6 Weeks

Outcome -You do worse
with higher
doses. It’s
possible to
survive.
323
Q

Acute
Radiation
Syndrome

GI

A

Dose Needed - > 8 Gy

Dose Needed
“Rounded For
Memory” - 10 Gy

Latent Period -5-7 Days

Outcome -Death within 2
weeks

324
Q

Acute
Radiation
Syndrome

CNS

A

Dose Needed - > 20-50 Gy

Dose Needed
“Rounded For
Memory” - 100 Gy

Latent Period -4-6 Hours

Outcome -Death within 3
days (unless you
get to Elysium)

325
Q

WB Dose (Gy)

< 1

A

No vomiting No skin redness

Surveillance for 5
weeks

326
Q

WB Dose (Gy)

1-2

A 
Vomiting 2-3 hours
after exposure
Skin redness
(12-24 hours after
exposure)

Surveillance for 3
weeks, Consider
General Hospital

327
Q

WB Dose (Gy)

2-4

A 
Vomiting 1 -2 hours
after exposure
Skin redness
(8-15 hours after
exposure)

Hospitalize - Bum
Center

328
Q

WB Dose (Gy)

> 4

A 
Vomiting < 1 hour
after exposure
Skin redness
(1-6 hours after
exposure)

Hospitalize -
Specialized Radiation
Center

329
Q

Skin Problem
Dose (Gy) Onset
Early Transient Erythema

A

2 Gy skin dose hours

330
Q

Skin Problem
Dose (Gy) Onset
Severe “Robust” Erythema

A

6 Gy skin dose 1 Week

331
Q

Skin Problem
Dose (Gy) Onset
Telangiectasia

A

10 Gy skin dose 52 Weeks

332
Q

Skin Problem
Dose (Gy) Onset
Dry Desquamation

A

13 Gy skin dose 4 Weeks

333
Q

Skin Problem
Dose (Gy) Onset
Moist Desquamation / Ulceration

A

18 Gy skin dose 4 Weeks

334
Q

Skin Problem
Dose (Gy) Onset
Secondary Ulceration

A

24 Gy skin dose > 6 weeks

335
Q

Hair Problem
Dose (Gy) Onset

Temporary Epilation

A

3 Gy 21 Days

336
Q

Hair Problem
Dose (Gy) Onset
Permanent Epilation

A

7 Gy 21 Days

337
Q

Cell Sensitivity - Trivia

A

Order of Sensitivity M > G2 > Gl > S.

338
Q

Most radiosensitive part of the GI tract ?

A

Small Bowel

339
Q

MOST sensitive blood cells in the body ?

A

Lymphocytes. A dose of 0.25 Gy is enough to

depress the amount circulating in the blood.

340
Q

< 50 mGy fetus

A

0-2 Weeks: “All or Nothing” - Spontaneous Abortion or Not
- but probably OK at these low doses

> 2 Weeks: Dose isn’t enough to matter (probably)

341
Q

> 50-100 mGy fetus

A

0-2 Weeks:”All or Nothing” - Spontaneous Abortion or Not
- risk o f fetal loss is more legit above 100 mGy

8-15 Weeks:Neuronal Development - might cause a retard (Borat’s Brother Billo).
Most sources call this period the greatest risk of teratogenesis

> 25 Weeks: No teratogenic effects at diagnostic doses (those less than 100 mGy)

342
Q

100-500 mGy fetus

A

Consider aborting - based on individual risk factors, and various superstitious beliefs

343
Q

T 1 (Longitudinal) is determined by ?

A

Interaction with the Spin - Lattice

77 = has grown to 63% o f magnetization

344
Q

T2 (Transverse) is determined by ?

A

Spin-Spin Interactions dephase magnetization

12 = has decayed to 37% o f original value

345
Q

T2* (Free Induction Decay) is determined by ?

A

Spin-Spine Interactions PLUS the Non-

Uniformity of the Magnetic Field

346
Q

T1 “Shortening” is ?

A

Bright

347
Q

T2 “Shortening” is ?

A

Dark

348
Q

T1

A

Short TR

Short TE

349
Q

T2

A

Long TR

Long TE

350
Q

Proton Density

A

Long TR

Short TE

351
Q

Spin Echo

A

Short TR 250-700 ms
Long TR >2000 ms
Short TE 10-25 ms
Long TE >60 ms

352
Q

GRadient Echo

A

Short TR < 50 ms
Long TR >100 ms
Short TE 1-5 ms
Long TE >10 ms

353
Q

MRI - Table Time

Standard Sequence ?

A

TR x Phase Matrix x NEX

354
Q

MRI - Table Time

3D Sequence ?

A

TR x Phase Matrix x NEX x # Slices

355
Q

MRI - Table Time

Fast Spin Echo ?

A

Acquisition time is approximately proportional to 1/Echo Train Length

356
Q

MRI - Slice Thickness

Thinner Slice

A

Steep (“Increased”)
Slice Selection Gradient
Decreased Transmit
Bandwidth

357
Q

MRI - Slice Thickness

Thicker Slice

A

Shallow (“Decreased”)
Slice Selection Gradient
Increased Transmit
Bandwidth

358
Q

MRI Modification

Thicker Slices

A

Signal to noise:Increased

Spatial resolution:Decreased

Duration of Exam:No Effect

359
Q

MRI Modification

Larger Field of View

A

Signal to noise:Increased

Spatial resolution:Decreased

Duration of Exam:No Effect

360
Q

MRI Modification

Larger Matrix

A

Signal to noise:Decreased

Spatial resolution:Increased

Duration of Exam:Increased

361
Q

MRI Modification

Greater Field
Strength

A

Signal to noise:Increased

Spatial resolution:No Effect

Duration of Exam:No Effect

362
Q

MRI Modification

Greater Receiver
Bandwidth

A

Signal to noise:Decreased

Spatial resolution:No Effect

Duration of Exam: decreased

363
Q

MRI Modification

Greater Transmit
Bandwidth

A

Signal to noise:Increased

Spatial resolution:Decreased

Duration of Exam:No Effect

364
Q

MRI Modification

More Excitations
per Slice
“More Averages ”

A

Signal to noise:Increased

Spatial resolution:No Effect

Duration of Exam:Increased

365
Q

MRI Modification

Utilizing Partial K
Space Sampling

A

Signal to noise:Decreased

Spatial resolution:No Effect

Duration of Exam:Decreased

366
Q

MRI - Receive vs Transmit

Large Receiver
Bandwidth

A

Decrease SNR

367
Q

MRI - Receive vs Transmit

Large Transmit
Bandwidth

A

Increased SNR

Large Slice

368
Q

MRI - Receive vs Transmit

Small Receiver
Bandwidth

A

Increased SNR

369
Q

MRI - Receive vs Transmit

Small Transmit
Bandwidth

A

Decrease SNR

Thin Slice

370
Q

MRI - “Tradeoffs”

Thicker Slices

A

Improves SNR Degrades Spatial

Resolution

371
Q

MRI - “Tradeoffs”

Thinner Slices

A

More Noise Improves Spatial

Resolution

372
Q

MRI - “Tradeoffs”

Stronger Magnet

A 
Better SNR
*more signal
Worsening
Chemical Shift (Type 1)
and Susceptibility
“Metal” Artifacts
373
Q

MRI - “Tradeoffs”

Thinner receiver
bandwidth

A 
Improves SNR
Worsening
Chemical Shift (Type 1)
and Susceptibility
“Metal” Artifacts
374
Q

MRI - “Tradeoffs”

Increasing NEX
(Number o f
Excitations)

A

Improves SNR Increased Table Time

375
Q

MRI - “Tradeoffs”

Longer TR

A

Improves SNR Increased Table Time

376
Q

MRI - “Tradeoffs”

Shorter TE

A 
Improves SNR
Can screw up you
tissue contrast (reduced
T2 effect) - should only
be done with Tl.
377
Q

Best Sequence for SNR ?

A

Proton Density

Long TR, Short TE

378
Q

1.5 T: Out of Phase, In Phase Times ?

A

Out of Phase 2.2 msec, In Phase 4.4 msec,

Out of Phase 6.6 msec, In Phase 8.8 msec

379
Q

3.0 T: Out of Phase, In Phase Times ?

A

Out of Phase 1.1 msec, In Phase 2.2 msec,

Out of Phase 3.3 msec, In Phase 4.4 msec

380
Q

fMRI depends on ?

A

T2* effects
uses Blood Oxygen Level Dependent
(BOLD) imaging

381
Q

Cardiac Sequence “Bright Blood” ?

A

Gradient

382
Q

Cardiac Sequence “Black Blood” ?

A

Double Inversion Spin Echo

383
Q

Cardiac Sequence to Null Myocardium ?

A 
Inversion Recovery
(TJ. selected to match patient’s myocardium)
384
Q

Magnevist

A 
Gadopentetate
(Gd-DTPA) Linear Ionic
Oldest PDA Approved Agent
Probably has the highest NSP
Risk
385
Q

Multihance

A

Gadobenate

(Gd-BOPTA) | Linear Ionic 5% Hepatocyte Uptake

386
Q

Eovist

A

Gadoxetate

(Gd-EOB-DTPA) Linear Ionic 50% Hepatocyte Uptake

387
Q

Gadavist

A

Gadobutrol
(Gd-BT-D03A) Macrocylic Non-Ionic High Viscosity
Low (none?) Risk of NSP

388
Q

Fat Saturation Sequences Post Gad ?

A

NOT STIR - Inversion time is too similar

389
Q

Gad Works By?

A

Increasing Spin-Lattice interactions

“Shortens” T1

390
Q

NSF is a risk when ?

A 
Renal Failure (GFR < 30)
Pro-Inflammatory States (Acute Illness)
391
Q

NSF highest association ?

A

“Omniscan” (Gadodiamide)

392
Q

Artifact

Aliasing

A

Direction: Phase
Encoding

Better: •Increase the field of
view
•Change the phase
encoding direction

Worse: Smaller FOVs

Trivia:Caused by a small FOV

393
Q

Artifact

Chemical Shift
Type 1

A

Direction: Frequency
Encoding

Better: •Bigger Pixels
•Fat Suppression
•Increase Receiver
Bandwidth

Worse: •Stronger Magnetic
Field
•Lower Receiver
Bandwidth

Trivia:Caused by differences in
resonance frequencies

394
Q

Artifact

Chemical Shift
Type 2
“India Ink”

A

Direction: Both phase
and
frequency

Better:  •Adjust the TE
• Perfonn Spin Echo
Sequence (remember
this only occurs with
GRE)

Worse:

Trivia:Caused by differences in
resonance frequencies -
oppose each other at
specific TE intervals.

395
Q

Artifact

Gibbs /
Truncation

A

Direction: Both phase
and
frequency

Better:  • Bigger Matrix
•Decrease Bandwidth
•Decrease Pixel Size
(increase PE Steps,
Decrease FOV)

Worse:

Trivia:•Caused by limited
sample of FID
•Classically seen in the
spinal cord

396
Q

Artifact

Partial Volume

A

Direction:

Better: •Decrease Pixel Size
(increase PE Steps,
Decrease FOV)

Worse: Thicker Slices

Trivia:

397
Q

Artifact

Motion Artifact

A

Direction: Phase
Encoding

Better:  •Saturation pulses
•Respiratory gating
•Faster sequences
(BLADE,
PROPELLER)

Worse:

Trivia:

398
Q

Artifact

Cross Talk

A

Direction:

Better: •Increase slice gap
•Interleave slices

Worse:

Trivia:Caused by overlap of
slices

399
Q

Artifact

Zipper

A

Direction: Phase
Encoding

Better:

Worse:

Trivia:Caused by poor shielding

400
Q

Artifact

Field Inhomogeneity

A

Direction:

Better: •Shimming

Worse: GRE Sequences

Trivia: Caused by geometric
distortion

401
Q

Artifact

Susceptibility
“Metal”

A

Direction:

Better:  • Spin Echo
• Less Field Strength
•High receiver
bandwidth
•Short echo spacing
•Thin Slices

Worse: GRE Sequences
Bigger Field
Strength

Trivia: •Caused by augmentation
of magnetic field
•Very bad in EPI

402
Q

Artifact

Eddy Current

A

Direction:

Better: •Optimize sequence of
gradient pulses

Worse: DWI - large gradient
changes

Trivia: Caused by geometric
distortion or nonuniformity

403
Q

Artifact

Dielectric
Effects

A

Direction:

Better: •Parallel Transmit
•Use 1.5 T

Worse: 3 T

Trivia: • Standing waves created
as radiowave approaches
length of body part

404
Q

Artifact

Magic Angle

A

Direction:

Better: •T2

Worse: Tl, PD

Trivia: Occurs at 55 Degrees

405
Q

MR - Safety Related Trivia

Zone I

A

No Restriction This is basically outside the building

406
Q

MR - Safety Related Trivia

Zone II

A

No Restriction
This is the waiting room and the dressing
room. This is where you can screen patients
and control access to Zone 3 and 4.

407
Q

MR - Safety Related Trivia

Zone III

A

Restricted Room
This is typically the control room, where the
MRI tech does his/her thing. There should be
some kind of a lock on the door between
zone 2 and 3.

408
Q

MR - Safety Related Trivia

Zone IV

A

Restricted Room This is the actual MRI scanner room (the

same room as the magnet)

409
Q

MR - Safety Related Trivia

Quenching - Only if ?

A

There is a fire or trapped patients or staff member trapped

410
Q

MR - Safety Related Trivia

Prior to the quench …

A

Get the fuck out of the room (zone 4)

411
Q

MR - Safety Related Trivia

Quench if code ?

A

A code is NOT a reason to quench

412
Q

MR - Safety Related Trivia

Who should push the Quench
button

A

Medical Student, Tech, Non-English Speaking Observer….

Anyone but you

413
Q

MR - Safety Related Trivia

5 G Line ?

A

.It is an implanted device safety thing, not a pulling

(translational force) thing

414
Q

MR - Safety Related Trivia

Hearing Damage Trivia:

A

• Noise - from the gradient set.
• Worse with Echo Planar
• Damage to the fetal ossicles is part of the
theoretical (complete bullshit) reason fetal

415
Q

MR - Safety Related Trivia

Neurostimulation ?

A

High-bandwidth readouts and rapid gradient switching

(echo-planar imaging) are the usual culprits

416
Q

MR - Safety Related Trivia

SAR Formula ?

A

Bo2 x Alpha2 x Duty Cycle
(B = magnet strength, Alpha = Flip angle, Duty Cycle —
how short your TR is).

417
Q

MR - Safety Related Trivia

SAR Limit ?

A

4W/kg

418
Q

MR - Safety Related Trivia

Doubling the TR will do what
to the Duty Cycle?

A

Double the TR - will half the Dutv Cycle

419
Q

Fat Saturation Sequences Post Gad ?

A

NOT STIR - Inversion time is too similar

420
Q

Gad Works By?

A

Increasing Spin-Lattice interactions

“Shortens” TI

421
Q

NSF is a risk when ?

A 
Renal Failure (GFR < 30)
Pro-Inflammatory States (Acute Illness)
422
Q

NSF highest association ?

A

Omniscan” (Gadodiamide)

423
Q

Lactation ?

A

Current guidelines: No need to stop
breastfeeding after contrast administration.
This goes for both CT Contrast (iodine) and MR
Contrast (Gadolinium)

424
Q

What agents are NOT
safe with Lactation ?
What are the
recommendations ?

A

I131 No more breast feeding
Gallium67 No more breast feeding
Tc”m You can resume breast feeding in 12-24 hours
I123 You can resume breast feeding in 2-3 days

425
Q

Precision

A

This is the immunity to variation

426
Q

Accuracy Definition

A

This is the immunity to systematic error or bias

427
Q

Type 1 Error

A

The is a false positive.

The fire alarm has gone off, but there is no fire.

428
Q

Type 2 Error:

A

This is a false negative.

The house is on fire, but the alarm does NOT go off.

429
Q

Incidence Rate

A

New Cases of Disease/

Total Number of People are Risk

430
Q

Prevalence Rate

A

Number of Cases of Disease/

Total Number of People at Risk

431
Q

Sensitivity

A

True Positive/

True Positive + False Negatives.

432
Q

Specificity

A

True Negative/
True Negative + False Positives
*Specific Exams Rule IN Disease

433
Q

Accuracy

A

True Positive + True Negative/

TP + FP + TN + FN

434
Q

Positive Predictive Value

A

True Positive/

True Positive + False Positives

435
Q

Negative Predictive Value

A

True Negative/

True Negative + False Negative

436
Q

Absolute Risk

A

Same as Incidence Rate

New Cases of Disease/
Total Number of People are Risk

437
Q

Relative Risk

A

Incidence of disease among persons exposed to risk factor/

Incidence of disease among people who did NOT get exposed to risk factor.

438
Q

Odds Radio

A

Cases WITH Exposure x Controls WITHOUT Exposure/

Controls WITH Exposure x Cases WITHOUT Exposure

CTC Paul (17 decks)

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