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
G eometric Relationship More Blur
1. Closer the source is to the image | 2. More Magnification
26
DQE =
Measurement of efficiency • High DQE = Low Dose • Low DQE = High Dose
27
DQE is directly proportional to
MTF MTF describes the relationship between sharpness and resolution.
28
DQE is inversely proportional to
Signal to Noise Ratio
29
DQE is better at
Low spatial resolution
30
Approximate DQE:
DR = 0.45 | Plain Film = 0.25
31
mAs Controls the
Radiographic Density | how black the image is
32
kVp Controls the
Radiographic Contrast • Low kVp = High Contrast • High kVp = Low Contrast
33
To achieve a noticeable difference in “density”
Increase mAs by 30%
34
To maintain density after decreasing mA by | 50% you would
Increase kVp by 15%
35
4 cms o f tissue requires
Double the mA
36
Grids typically are NOT used with
Babies and Extremities
37
Cons to using a Grid
Increased Dose
38
Ways to Reduce Scatter (Improve Contrast)
1 - Collimate 2 - Compress the Part 3 - Lower kVp 4 - Grid / Air Gap
39
Pros of Collimation
1 - Increase Contrast 2 - Decrease Scatter 3 - Decrease KAP
40
Cons o f Collimation
1 - Smaller FOV
41
Scatter is Most Severe With
- High kVp Technique - Large Field o f View - Thick Parts (or People)
42
D ig ita l - T riv ia S um m a ry
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.
43
The primary factor influencing image contrast | in film systems
kvp
44
The primary factor influencing image contrast (in digital systems)
LUT kVp still influences contrast, but digital systems have a much wider dynamic range.
45
Digital response curve
* Digital has a linear response curve, | * Film has a curvilinear response curve.
46
Major determinant of spatial resolution with | digital images is
Pixel Size and Spacing (pixel pitch)
47
Digital Decreased Pixel Pitch
Better Spatial Resolution
48
Digital Increased Pixel Density
Better Spatial Resolution
49
Digital Direct vs Indirect
Indirect (scintillators) Xrays ==> Light = > Charge Direct (photoconductors) = X rays ==> Charge
50
Digital Indict uses
Thallium doped Cesium Iodide (Csl) | “Scintillator”
51
Digital Direct uses
Amorphous Selenium
52
Specific Factors Affecting the Spatial Resolution of CR Laser Spot Size:
smaller is better
53
Specific Factors Affecting the Spatial Resolution of CR Phosphor Pate Density / Thickness
More Thick = More Light Spreading = Less Resolution
54
Specific Factors Affecting the Spatial Resolution of CR Sampling Frequency (Rate of Light Sampling):
Increasing the sampling frequency | results in a smaller pixel pitch with improves the spatial resolution.
55
Specific Factors Affecting the Spatial Resolution of CR Imaging Plate:
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.
56
Specific Factors Affecting the Spatial Resolution of CR Increasing x-rays will NOT improve
Maximum spatial resolution
57
Specific Factors Affecting the Spatial Resolution of DR
* 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.
58
Direct Conversion
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)
59
In d ire c t Conversion
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)
60
Mammo vs General Radiology mammo
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
61
Mammo vs General Radiology general radiology
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
62
Contact Mode - The Normal Mammogram
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)
63
Magnifications - 1.5x - 2x (mammo)
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)
64
Mammo Target Trivia Larger or denser breasts
R h /R h Mo anode can also be combined with an aluminum filter, fo r a harder beam to penetrate denser breasts.
65
Mammo Target Trivia “Intermediate” density breasts
Mo anode with Rhodium filter
66
Mammo Target Trivia “Thin” breasts
Mo anode with Mo filter
67
Mammo Target Trivia What Combination would you “never” use?
Rh Target (21 kev) with a Mo Filter (20 Kev K edge)
68
PPV1
Abnormal Screener “Call Back” 3-8% 4.4%
69
PPV2
Recommended Biopsy (4 or 5) 15-40% (25*50% if palpable) 25.4%
70
PPV3
Biopsy Done - Actual Cancer 20-45% (30-55% if palpable) 31.0%
71
Specific QA Tasks
``` 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 ```
72
Appropriate Target Range | for Medical Audit
Recall Rate 5-7% | Cancers/ 1000 Screened 3-8
73
The Privilege to Read a Mammogram
``` During the last two years of training you have to read 240 Formal Training Requirement 3 months Documented Hours of Education 60 ```
74
Brea st Phantom Trivia
``` 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 ```
75
General Radiology vs fluoro general rads
mA 200-800 kVp 50 -120 Very short exposure times Focal Tube Spot 1.0 -1.2mm
76
General Radiology vs fluoro fluoro
mA 0-5 kVp 50 -120 Longer exposure times Focal Spot 0.3-0.6mm
77
Last Image | Hold
The last frame of the fluoroscopic loop is “held” Low Dose More Quantum Mottle (less photons) Spatial Resolution around 2 Line Pairs per mm
78
Spot Film
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
79
Digital Spot
Digital Equivialant to Spot | Film - minus the cassette
80
Geometric | Mag
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
81
Electronic | Mag (Zoom)
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
82
Fluoro Trivia Best Position of the I.I. and X-ray Tube ?
X- Ray tube far away, with the I.I. close.
83
Fluoro Trivia Where is the ideal place to stand ?
On the same side of the patient as the | imaging intensifier
84
Fluoro Trivia Double the distance from the tube does what to dose ?
Decreases it by a factor of 4 (inverse | square law).
85
Fluoro Trivia Normal Air Kerma Limit ?
87 mGy/min (10 Roentgens per min)
86
Fluoro Trivia High Level Control (Really Fat Level Control) ?
176 mGy/min (20 Roentgens per min)
87
Fluoro Trivia In “high level mode”, you must have ?
Audible or visual alarms (in addition to the normal time alarm used in normal fluoroscopy.)
88
Pulsed Fluoro Conventional fluoro
long very low continuous mA. | • Pulse fluoro is pulsed (NOT continuous mA but instead pulse of higher mA).
89
Pulsed Fluoro Pulse Fluoro is good for moving patients (Wiggling Babies)
Gives you sharper | images with less motion blur
90
Pulsed Fluoro Pulsed Fluoro can reduce dose
when the frame rate is below 30 frame /second
91
Pulsed Fluoro People always use a drop o f 30 to 15 frames per second as an example
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.
92
Pulsed Fluoro Be careful how the question is worded
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.
93
Fluoro in IR Trivia Best kVp to use with IV contrast is ?
Between 60-80 kVp (average beams | hit that k-edge nicely)
94
Fluoro in IR Trivia IR uses relatively Small Focal Spots, and Small Anode Angle Because ?
The need for maximum spatial resolution
95
Fluoro in IR Trivia Grids ?
Usually ■ but Not with Peds and ■ Not with Extremities
96
Fluoro in IR Trivia 50% of the dose is delivered ?
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)
97
Fluoro in IR Trivia “Dose Spreading”
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
98
Fluoro in IR Trivia “Best Place to Stand”
``` 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. ```
99
Fluoro in IR Trivia Magification will ... ?
increase Air Kerma, but NOT KAP
100
Fluoro in IR Trivia ``` The dose (outside lead) standing 1 meter from the patient is about “?” of the dose received by the patient. ```
1/1000
101
General Radiology vs CT
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
102
CT Trivia What kind of x-rays are used with CT?
Highly filtered, High kV | average energy 75 keV
103
CT Trivia Bow Tie Filters do what ?
* Compensate for uneven filtration, * Reduce Scatter, * Reduce Dose
104
CT Trivia “Septa” is the CT term for ?
A Grid
105
CT Trivia Minimal slice thickness is determined by ?
Detector element aperture width in a modem CT
106
CT Trivia Pixel size =
Field of View / Matrix Size
107
CT Trivia How do you improve spatial resolution ?
You need to make the pixels smaller (matrix larger). | Remember that Pixel Size = FOV/ Matrix
108
CT Trivia Decreasing kV from 140 to 80 will do what to the HU of a contrast enhanced vessel?
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)
109
Pitch | o f “ l ” ?
There is no overlap | between slices.
110
Pitch | “Greater than 1” ?
This means the table moved faster than the beam, and you have gaps betw’een your slices. Spatial Resolution Decreased Dose Decreased
111
Pitch | “Less than 1 ” ?
This means the table moved slow, and your slices overlapped. Spatial Resolution Improved Dose Increased
112
Window Level (or Center)
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.
113
Widows Width
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
114
A narrow (decreased) window width
Increases Contrast.
115
A wider (increased) window width
Decreases Contrast.
116
WL - “Brain” ?
W 80, L +40
117
WL - “Stroke” ?
W 3 0 , L +30
118
WL - “Lung’
W 1500, L - 400
119
WL - “Abdomen” ?
W 400, L + 50
120
WL - “Bone” ?
W 1600, L +500
121
Cardiac CT Prospective: “Step and Shoot” - R-R interval pro
There is reduced radiation b/c the scanner isn’t on the whole time
122
Cardiac CT Prospective: “Step and Shoot” - R-R interval con
No functional imaging. Susceptible to motion artifact.
123
Cardiac CT Prospective: “Step and Shoot” - R-R interval trivia
Always axial, not helical. You need a slow heart rate (50-65 bpm)
124
Cardiac CT Retrospective: Scans the whole time, then back calculates pro
Can do functional imaging (evaluate contraction and wall motion)
125
Cardiac CT Retrospective: Scans the whole time, then back calculates con
Higher radiation (use of low pitch - increases dose)
126
Cardiac CT Retrospective: Scans the whole time, then back calculates trivia
none lol
127
Beta Blockers
Metoprolol Tartrate (Lopressor) 2.5-5.0 mg IV Regulate / lower heart rate to less than 65 bpm for prospective ECG-triggered coronary CT
128
Beta Blockers CI
``` • SBP < 100 • Decompensated Cardiac Failure • Asthma on beta-aeonist inhalers (albuterol) • Active bronchospasm • Severe COPD • 2nd or 3rd-degree AV block ```
129
Nitroglycerine
0.8-1.2 mg glycerol trinitrate • 5 mg isosorbide dinitrate Dilates coronary arteries. Improves visualization / sensitivity etc... etc.. so on and so forth.
130
Nitroglycerine CI
``` • 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. ```
131
Beta Blockers reversal
``` 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 ```
132
Spatial Resolution Holding matrix size constant and decreasing FOV
This will decrease pixel size. | Spatial Resolution is Improved
133
Spatial Resolution Holding matrix size constant and increasing FOV
This will increase pixel size. | Spatial Resolution is Degraded
134
Spatial Resolution Optimal Reconstruction Filter
Bone “sharp ” algorithm gives | a higher spatial resolution
135
Contrast Resolution Holding matrix size constant and decreasing FOV
This will decrease pixel size. Contrast Resolution is Degraded (less photons per box)
136
Contrast Resolution Holding matrix size constant and increasing FOV
This will increase pixel size. | Contrast Resolution is Improved.
137
Contrast Resolution Optimal Reconstruction Filter
“Soft tissue ” or “smooth ” improves contrast resolution - relative to bone
138
Contrast Resolution Trivia What changes to kVp and mA will maximize contrast resolution ?
``` Increased mA (less mottle, more signal). Decreased kVp (less scatter, less noise). **especially in “small” patients (kids), and contrasted exams. ```
139
Spatial Resolution Trivia A “?” Focal Spot will improve spatial resolution
Smaller Spot = Better | Determines Spatial Resolution in the X-YPlane... sided to side.
140
Spatial Resolution Trivia A “?” Detector Width will improve spatial resolution
Smaller Detector = Better Determines Spatial Resolution in the Z Plane (the long axis or Cranial Caudal direction)
141
Spatial Resolution Trivia A “?” Pitch will improve spatial resolution
• 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.
142
Spatial Resolution Trivia Consequences of decreasing the pitch ?
More Dose
143
CT Dose Related Trivia Decrease kVp or Decreased mA
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).
144
CT Dose Related Trivia Larger Pitch ?
Decreased Dose | 50% increase in pitch = 50% dose decrease
145
CT Dose Related Trivia | ``` Reconstruction Method Iterative > Filtered Back ```
Iterative algorithms handle noise better — allows for a lower dose technique to be used.
146
CT Dose Related Trivia Acquired slice thickness? *Z-Axis Resolution
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.
147
CT Dose Related Trivia Increased Rotational Time ?
``` Less Dose (Faster rotation = less dose.) Dose is proportional to both scan time and rotation time. ```
148
CT A r tifa c t R e la te d T riv ia Ring
Call the manufacturer / “Scanner Mechanic” | The detector needs fix ed / replaced.
149
CT A r tifa c t R e la te d T riv ia Partial Volume
Acquire thinner slices (decrease beam width , increase beam | collimation)
150
CT A r tifa c t R e la te d T riv ia Stair Step
Acquire thinner slices (decrease beam width , increase beam collimation) Reconstruction with overlapping intervals
151
CT A r tifa c t R e la te d T riv ia Beam Hardening
Reposition the patient (arms up - etc...) | Increase the kVp
152
CT A r tifa c t R e la te d T riv ia Metal
* Increase the kVp (sometimes works). * Use thinner slices. * Certain interpolation software can help.
153
CT A r tifa c t R e la te d T riv ia Photon Starvation
• 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.
154
CT A r tifa c t R e la te d T riv ia Motion
• 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.
155
U ltra so u n d R e la te d T riv ia Reflection
Ultrasound energy gets reflected at a boundary between two tissues because of the differences in the acoustic impedances of the two tissues.
156
U ltra so u n d R e la te d T riv ia Refraction - Influenced by:
(1) Speed Change - which is based on tissue compression, | (2) the Angle of Incidence. “Snells Law”
157
U ltra so u n d R e la te d T riv ia High Frequency Probes: - Scatter ? - Attenuation ?
* More Scatter. | * More Attenuation
158
U ltra so u n d R e la te d T riv ia Piezoelectric Materials (PZT) are ?
• 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
159
U ltra so u n d R e la te d T riv ia High Q Dampening Block
* Low Damping (high Q) * Narrow Bandwidth * For Doppler, to preserve velocity information.
160
U ltra so u n d R e la te d T riv ia Low Q Dampening Block
• Heavy Damping (low Q) • Broad Bandwidth • Gives you high spatial (axial) resolution *fewer interference effects and therefore more uniformity
161
U ltra so u n d R e la te d T riv ia Matching Layer Function ?
Minimizes the acoustic impedance differences between | the transducer and the patient.
162
U ltra so u n d R e la te d T riv ia French / Latin Sounding words for: • Near Zone: • Far Zone:
* The Near Field (Fresnel Zone) | * The Far Field (Fraunhofer Zone)
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U ltra so u n d R e la te d T riv ia Higher Transducer Frequency does what to the near field ?
Higher Transducer Frequency = Longer Near Field.
164
U ltra so u n d R e la te d T riv ia Focal Zone Maximizes “?”
lateral resolution
165
U ltra so u n d R e la te d T riv ia How do you improve tissue penetration (depth) ?
Use a lower frequency probe.
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U ltra so u n d R e la te d T riv ia How do you brighten up deep structures ?
Start fucking around with the “TGC” - Time Gain Compensation Buzzword “Uniform brightness”
167
Im p ro v in g A x ia l | R e so lu tio n US
Shorter Pulses (Smaller Spatial Pulse Length) Greater Damping “Low Q ” (shorter pulses) Higher Frequency Probe (shorter wavelength)
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Im p ro v in g L a te ra l | R e s o lu tio n US
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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Im p ro v in g E le v a tio n | R e s o lu tio n US
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
170
R e s o lu tio n T riv ia US The stand off pad serves what function?
* Helps place superficial things in the focal zone | * This improves the lateral resolution
171
R e s o lu tio n T riv ia US Axial Resolution depends on ?
Spatial Pulse Length
172
R e s o lu tio n T riv ia US Lateral Resolution depends on ?
Transducer Element Width
173
R e s o lu tio n T riv ia US Elevation Resolution depends on ?
Transducer Element Height
174
R e s o lu tio n T riv ia US Axial Resolution is independent of ?
Depth | * Lateral Resolution changes with depth.
175
R e s o lu tio n T riv ia US High Frequency Probes improve ?
Axial Resolution * Small wavelength allows for smaller spatial pulse length Lateral Resolution *Less beam spreading
176
R e s o lu tio n T riv ia US Harmonics improves ?
Lateral Resolution
177
Harmonics works by ?
Transmitting at one frequency and | receiving at another
178
Compound Imaging works by ?
Using electronic steering of the ultrasound beams from the transducer to image an object in multiple different directions
179
Harmonics are NOT produced in the ?
Near Field | they haven’t traveled fa r enough
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Harmonics can result in reduced ?
1 - Reverberation Artifact 2- Depth Penetration (remember higher frequency attenuates - so the beam is attenuated-faster).
181
Compound Imaging can result in reduced ?
Posterior shadowing
182
Compound Imaging will “?” the edges
Sharpen them
183
Artifact comet tail
harmonics - more visible compounding - less visible
184
Artifact ring down
harmonics - n/a compounding - reduced
185
Artifact reverberation
harmonics - reduced/eliminated compounding - n/a
186
Artifact increased through transmission
harmonics - increased compounding - n/a
187
Artifact acoustic shadowing
harmonics - increased compounding - decreased
188
Artifact speckle noide
harmonics - reduced compounding - reduced
189
Artifact
harmonics - compounding -
190
Artifact side lobe/grating
harmonics - reduced compounding - n/a
191
Thermal Index (T.I.) ?
Heating: this is the maximum temperature rise | in tissue secondary to energy absorption.
192
Mechanical Index (M.I.) ?
Cavitation (Mechanical Damage): this is how likely it is that cavitation will occur considering peak rarefaction pressure and frequency.
193
What should be avoided with neonatal | imaging ?
Pulsed Spectral Doppler
194
What should be used instead ?
M-Mode US (to document fetal HR)
195
The T.I. should be ?
Under 1.0 (some sources say 0.7)
196
Ideal Doppler Angle ?
The angle should be between 30- 60. | Theoretically the best angle is zero.
197
Doppler Angle of 90 Degrees will ?
Look like no flow
198
If you are looking for slow flow, you | should ?
* Use a low pulse repetition frequency (PRF) | * Use Power Doppler
199
Power Doppler does Not depend on ?
The Doppler Angle
200
Power Doppler does Not provide | information on ?
The Direction of Flow
201
Power Doppler will Not demonstrate | this artifact ?
Aliasing (both color and spectral can).
202
Aliasing Artifact occurs when ?
the doppler shift is greater than a threshold called the | “Nyquist frequency”
203
Aliasing Artifact Can be reduced by ?
• 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
Artifacts from Multiple Echoes Reverberation
Two parallel highly reflective surfaces - Multiple equidistantly spaced linear reflections.
205
Artifacts from Multiple Echoes Comet Tail
``` Two parallel highly reflective surfaces - closer together (< 1/2 SPL) Triangle (comet) shaped ```
206
Artifacts from Multiple Echoes Ring Down Artifact
Fluid trapped between a tetrahedron of air bubbles Parallel band extending posterior to a collection of gas
207
Artifacts from Multiple Echoes Mirror Image
Trapped behind a strong reflector This is almost always shown with the liver on lung.
208
IsotoPe
Same Number of Protons.
209
IsotoNe
Same Number of Neutrons
210
IsoBAR
Same MASS Number. | *Lift the barbell to put on some mass
211
IsoMer
Same Number of Protons and Neutrons. But the energy level is different — classic example is isoMeric Tc99M to Tc99.
212
H a lf Life Physical
How long it takes to decay to 1/2 activity. You’ll need to memorize these.
213
H a lf Life Biologic
How long it takes your body to shit, piss, cry, sweat out the tracer. They have to provide you with this number
214
H a lf Life Effective
Takes both Physical and Biologic into account (it’s always less) 1/Effective = 1/Physical + 1/Biologic
215
Tc - 99m
Analog: Energy:“Low” - 140 Physical half life: 6 hours
216
Iodine-123
Analog:Iodine Energy: “Low” - 159 Physical half life: 13 hours
217
Xenon -133
Analog: Energy: “Low” - 81 Physical half life: 125 hours (biologic tl/2 30 seconds)
218
Thallium - 201
Analog: Potassium ``` Energy: “Low” - 135(2%) - 167(8%) use 71 201 Hg daughter x-rays ``` Physical half life: 73 hours
219
Indium -111
Analog: Energy: “Medium” - 173 (89%), - 247(94%) Physical half life: 67 hours
220
Gallium - 67
Analog: Iron Energy: Multiple: - 93 (40%), - 184(20%), - 300(20%), - 393 (5%) Physical half life: 78 hours
221
Iodine -131
Analog: Iodine Energy: “High” - 365 Physical half life: 8 days
222
Fluorine -18
Analog: Sugar Energy: “High” -511 Physical half life: 110 mins
223
Cobalt -57
Analog: Used for Extrinsic Field Uniformity QA (Flood) Energy: “Low” - 122 - 136 Physical half life: 270.9 days
224
Germanium 68/ | Gallium 68
Analog: Used for PET QA Energy: “High” - 511 (via Ga) Physical half life: 270 days - Ge 68 minutes - Ga
225
Treatment Radionuclides Half Life Strontium 89
50.5 DAYS | 14 days in bone
226
Treatment Radionuclides Half Life Samarium 153
46 Hours
227
Treatment Radionuclides Half Life Radium 223
11 Days
228
Treatment Radionuclides Half Life Yttrium 90
64 Hours
229
Cardiac Radionuclides Half Life Rubidium 82
75 seconds
230
Cardiac Radionuclides Half Life Nitrogen 13
10 mins
231
Beta Minus
``` Lots of Neutrons Not Enough Protons Generate a Beta Particle (Electron) ISO BA R IC transition ```
232
Beta Plus
Lots of Protons Not Enough Neutrons Generate a Positron has 1.02 MeV
233
Electron | Capture
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
Alpha
``` Heavy Unstable Atoms Omits a heavy Helium nuclei (2 protons, 2 neutrons) ```
235
Collimator Type Parallel Hole
``` 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
Collimator Type Parallel Hole Image size and used for
Imase Size = - 1:1 - Equal to Patient “The work horse ”
237
Collimator Type Pinhole
``` 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
Collimator Type Pinhole Image size and used for
``` 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
Collimator Type Converging
Distance Sensitive - amount of magnification increases as object gets farther from the collimator. The FOV decreases with distance.
240
Collimator Type Converging Image size and used for
``` Image Size = - Magnifies without inverting Usedfor: - Multiple choice questions. - Sometimes small body parts ```
241
Collimator Type Diverging
Distance Sensitive - amount of minification increases as object gets farther from the collimator The FOV increases with distance.
242
Collimator Type Diverging Image size and used for
``` 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
Parallel Hole Factor Septa Length
``` Long Septa: - Low Sensitivity (Noisy) - High Spatial Resolution Short Septa: - High Sensitivity - Low Spatial Resolution ```
244
Parallel Hole Factor Hole Diameter
``` Wider Hole: - High Sensitivity - Low Resolution Narrow Hole: - Low Sensitivity - High Resolution ```
245
Parallel Hole Factor Septa Thickness
``` 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/A on the Dose Calibrator (Ionizing Chamber Consistency
Daily Should be within 5% of computed activity Checked with reference sources
247
Q/A on the Dose Calibrator (Ionizing Chamber Linearity
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/A on the Dose Calibrator (Ionizing Chamber Accuracy
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/A on the Dose Calibrator (Ionizing Chamber Geometry
Installation and any time you move the device Correction for different positioning and size Different volumes of liquid (Tc-99m)
250
G e ig e r - M u lle r C o u n te r
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
Ionizing chamber
For measuring dose rate. Used with higher rates. Lower Sensitivity Stable across a wide voltage range - Excellent for accurate estimates (or exposure).
252
“Pocket Ionization Detector”
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
“Solid State Dosimeter ”
Accumulated dose or rate can be read real | time with LCD display.
254
“Film Badge ”
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
“Optically Stimulated Dosimeter”
the film badge. Chips / | Strips are placed under a filter.
256
Survey Meters
G-M and Ionization Detectors - discussed on prior page
257
Well Counter
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
Dose Calibration & Automated Dose Injection Systems
Used to measure radiopharmaceuticals.
259
Thyroid Uptake | Probe
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
Intra-operative | Probes
Used for lymphoscintigraphy
261
10CFR part 19
Nwootrik,c eerss,. instmctions, and reports to workers ...i nspecti. ons „
262
10 CFRpart 20
Standards for protection against radiation, "radiation protection”
263
10CFR part 35
Medical use of by-product material. “human use of radioisotopes"
264
Regulations Major Spill Tc-99m
Greater than 100 mCi
265
Regulations Major Spill Tl-201
Greater than 100 mCi
266
Regulations Major Spill In-111
Greater than 10 mCi
267
Regulations Major Spill 1-123
Greater than 10 mCi
268
Regulations Major Spill Ga-67
Greater than 10 mCi
269
Regulations Major Spill 1-131
Greater than 1 mCi
270
Regulations Major Spill steps
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
Regulations - General Public Annual Dose limit
100 mrem
272
Regulations - General Public “Unrestricted area”
Not greater than 2 mrem per hour
273
Regulations - General Public “Restricted Area”
Defined as: | “Any place that receives a dose greater than 2 mrem/h”
274
Radiation Area
Any place you could get 0.005 rem (0.05mSv) in 1 hour at 30cm
275
High Radiation Area
Any place you could get O.lrem (lmSv) in 1 hour at 30cm
276
Very High Radiation Area:
Any place you could get 500 rads (5 gray) in 1 hour at 1 meter
277
Regulations - NRC Occupational Exposure Dose Limits Total Body Dose per Year
5 rem (50 mSv)
278
Regulations - NRC Occupational Exposure Dose Limits Dose to the Ocular Lens per year
15 rem (150 mSv)
279
Regulations - NRC Occupational Exposure Dose Limits Total equivalent organ dose
50 rem (500 mSv)
280
Regulations - NRC Occupational Exposure Dose Limits Total equivalent extremity dose per year
50 rem (500 mSv)
281
Regulations - NRC Occupational Exposure Dose Limits Total Dose to Embryo/fetus over entire 9 months
``` 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
Regulations - NRC Occupational Exposure Dose Limits units
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
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
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
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
ReCORDable Event Record Locally Institutional Review
285
Receiving, Storing, and Disposing of Radioactive Material
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
Package labe: white 1
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
Package | Label: yellow 1
special handling required Surface dose rate <50 mrem/hr, 1 meter < 1 mrem/hr T.I. < 1.0 mR per hour
288
Package label yellow 2
special handling rquired Surface dose rate < 200 mrem/hr, 1 meter < 10 mrem/hr T.I. >1.0 mR per hour
289
Common Carriers
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
Multiple Packages
Those shipped together Sum should NOT exceed 50 mR.
291
Radionuclide Purity What is it?
How much Mo in the Tc ? “Moly Breakthrough ’’
292
Radionuclide Purity Tested?
``` Tested in a dose calibrator with lead shields; Looking for 700 keV photons of Moly (remember Tc is only like 140) ```
293
Radionuclide Purity Limit?
0.15 microcuries of Mo per | 1 millicurie of Tc
294
Chemical Purity What is it?
How much A1 in the Tc ? “Aluminum Breakthrough
295
Chemical Purity Tested?
Tested with pH paper (Color Indicator Paper, or Paper Strip Test)
296
Chemical Purity Limit?
``` <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
Radiochemical Purity What is it?
How much Free | Tc?
298
Radiochemical Purity Tested?
Tested with Thin Layer Chromotography
299
Radiochemical Purity Limit?
``` . 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
Tc - Moly Generator operates with “Transient Equilibrium ”
which occurs at 4 daughter | half lives — Remember the t 1/2 of Tc is 6 hours. (4 x 6 = 24 hours)
301
2D PET vs 3D PET | 2d
Septa collimator (reject scatter) Less Sensitivity Fewer True, Scattered and Random Coincidences Smaller FOC for true coincidences More Tracer
302
2D PET vs 3D PET 3d
NO Septa Collimator (fast coincidence detector) More Sensitivity More True, Scattered and Random Coincidences Larger FOV for true coincidences Less Tracer
303
Attenuation Correction pet
ligth skin and light lungs
304
Uncorrected pet
hot skin andhot lungs
305
SUV Trivia
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
Dose units pet | Exposure C/kg
Charge (C) in the air created divided by the mass (kg) of that air.
307
Dose units pet | Absorbed Dose Gy
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
Dose units pet | Equivalent Dose Sv
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
Dose units pet | Effective Dose Sv
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
Deterministic Effects
Deterministic Effects Severity is dose related Does Not include Cancer Risk
311
Stochastic Effects (“Random”)
Has NO threshold Probability of effect increases with dose Severity is NOT dose related Includes heritable effects and carcinogenesis (NOT cell killing)
312
Dose Units - Fluoro | Air Kerma AK (Gy/min)
``` 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
Dose Units - Fluoro | Kerma-Area Product (KAP Gy-cm2)
``` 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
Dose Units - Fluoro | Cumulative Air Kerma (CAK Gy)
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
Dose Units - CT CTDI “CT Dose Index” mGy
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
Dose Units - CT “Weighted CTDI” mGy
This is 1/3 the central CTDI + 2/3 the Peripheral CTDI (expressed in mGy)
317
Dose Units - CT “Volume CTDI” mGy
``` 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
Dose Units - CT DLP “Dose Length Product” mGy - cm
CTDI - Vol x the length of the scan in cm. It is appropriate to add DLP from series to series.
319
Dose Units - CT “Effective Dose” fo r CT mSv
Effective Dose = k x DLP. Remember that “k” is a body part constant.
320
This vs That: Direct vs Indirect Radiation | Direct Radiation minority
Acts on DNA Most likely for High LET Radiation (unusual in x-ray imaging)
321
This vs That: Direct vs Indirect Radiation | Indirect Radiation majority
``` 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
Acute Radiation Syndrome Bone Marrow
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
Acute Radiation Syndrome GI
Dose Needed - > 8 Gy Dose Needed “Rounded For Memory” - 10 Gy Latent Period -5-7 Days Outcome -Death within 2 weeks
324
Acute Radiation Syndrome CNS
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
WB Dose (Gy) < 1
No vomiting No skin redness Surveillance for 5 weeks
326
WB Dose (Gy) 1-2
``` Vomiting 2-3 hours after exposure Skin redness (12-24 hours after exposure) ``` Surveillance for 3 weeks, Consider General Hospital
327
WB Dose (Gy) 2-4
``` Vomiting 1 -2 hours after exposure Skin redness (8-15 hours after exposure) ``` Hospitalize - Bum Center
328
WB Dose (Gy) > 4
``` Vomiting < 1 hour after exposure Skin redness (1-6 hours after exposure) ``` Hospitalize - Specialized Radiation Center
329
Skin Problem Dose (Gy) Onset Early Transient Erythema
2 Gy skin dose hours
330
Skin Problem Dose (Gy) Onset Severe “Robust” Erythema
6 Gy skin dose 1 Week
331
Skin Problem Dose (Gy) Onset Telangiectasia
10 Gy skin dose 52 Weeks
332
Skin Problem Dose (Gy) Onset Dry Desquamation
13 Gy skin dose 4 Weeks
333
Skin Problem Dose (Gy) Onset Moist Desquamation / Ulceration
18 Gy skin dose 4 Weeks
334
Skin Problem Dose (Gy) Onset Secondary Ulceration
24 Gy skin dose > 6 weeks
335
Hair Problem Dose (Gy) Onset Temporary Epilation
3 Gy 21 Days
336
Hair Problem Dose (Gy) Onset Permanent Epilation
7 Gy 21 Days
337
Cell Sensitivity - Trivia
Order of Sensitivity M > G2 > Gl > S.
338
Most radiosensitive part of the GI tract ?
Small Bowel
339
MOST sensitive blood cells in the body ?
Lymphocytes. A dose of 0.25 Gy is enough to | depress the amount circulating in the blood.
340
< 50 mGy fetus
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
> 50-100 mGy fetus
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
100-500 mGy fetus
Consider aborting - based on individual risk factors, and various superstitious beliefs
343
T 1 (Longitudinal) is determined by ?
Interaction with the Spin - Lattice | 77 = has grown to 63% o f magnetization
344
T2 (Transverse) is determined by ?
Spin-Spin Interactions dephase magnetization | 12 = has decayed to 37% o f original value
345
T2* (Free Induction Decay) is determined by ?
Spin-Spine Interactions PLUS the Non- | Uniformity of the Magnetic Field
346
T1 “Shortening” is ?
Bright
347
T2 “Shortening” is ?
Dark
348
T1
Short TR | Short TE
349
T2
Long TR | Long TE
350
Proton Density
Long TR | Short TE
351
Spin Echo
Short TR 250-700 ms Long TR >2000 ms Short TE 10-25 ms Long TE >60 ms
352
GRadient Echo
Short TR < 50 ms Long TR >100 ms Short TE 1-5 ms Long TE >10 ms
353
MRI - Table Time Standard Sequence ?
TR x Phase Matrix x NEX
354
MRI - Table Time 3D Sequence ?
TR x Phase Matrix x NEX x # Slices
355
MRI - Table Time Fast Spin Echo ?
Acquisition time is approximately proportional to 1/Echo Train Length
356
MRI - Slice Thickness Thinner Slice
Steep (“Increased”) Slice Selection Gradient Decreased Transmit Bandwidth
357
MRI - Slice Thickness Thicker Slice
Shallow (“Decreased”) Slice Selection Gradient Increased Transmit Bandwidth
358
MRI Modification Thicker Slices
Signal to noise:Increased Spatial resolution:Decreased Duration of Exam:No Effect
359
MRI Modification Larger Field of View
Signal to noise:Increased Spatial resolution:Decreased Duration of Exam:No Effect
360
MRI Modification Larger Matrix
Signal to noise:Decreased Spatial resolution:Increased Duration of Exam:Increased
361
MRI Modification Greater Field Strength
Signal to noise:Increased Spatial resolution:No Effect Duration of Exam:No Effect
362
MRI Modification Greater Receiver Bandwidth
Signal to noise:Decreased Spatial resolution:No Effect Duration of Exam: decreased
363
MRI Modification Greater Transmit Bandwidth
Signal to noise:Increased Spatial resolution:Decreased Duration of Exam:No Effect
364
MRI Modification More Excitations per Slice “More Averages ”
Signal to noise:Increased Spatial resolution:No Effect Duration of Exam:Increased
365
MRI Modification Utilizing Partial K Space Sampling
Signal to noise:Decreased Spatial resolution:No Effect Duration of Exam:Decreased
366
MRI - Receive vs Transmit Large Receiver Bandwidth
Decrease SNR
367
MRI - Receive vs Transmit Large Transmit Bandwidth
Increased SNR Large Slice
368
MRI - Receive vs Transmit Small Receiver Bandwidth
Increased SNR
369
MRI - Receive vs Transmit Small Transmit Bandwidth
Decrease SNR Thin Slice
370
MRI - “Tradeoffs” Thicker Slices
Improves SNR Degrades Spatial | Resolution
371
MRI - “Tradeoffs” Thinner Slices
More Noise Improves Spatial | Resolution
372
MRI - “Tradeoffs” Stronger Magnet
``` Better SNR *more signal Worsening Chemical Shift (Type 1) and Susceptibility “Metal” Artifacts ```
373
MRI - “Tradeoffs” Thinner receiver bandwidth
``` Improves SNR Worsening Chemical Shift (Type 1) and Susceptibility “Metal” Artifacts ```
374
MRI - “Tradeoffs” Increasing NEX (Number o f Excitations)
Improves SNR Increased Table Time
375
MRI - “Tradeoffs” Longer TR
Improves SNR Increased Table Time
376
MRI - “Tradeoffs” Shorter TE
``` Improves SNR Can screw up you tissue contrast (reduced T2 effect) - should only be done with Tl. ```
377
Best Sequence for SNR ?
Proton Density | Long TR, Short TE
378
1.5 T: Out of Phase, In Phase Times ?
Out of Phase 2.2 msec, In Phase 4.4 msec, | Out of Phase 6.6 msec, In Phase 8.8 msec
379
3.0 T: Out of Phase, In Phase Times ?
Out of Phase 1.1 msec, In Phase 2.2 msec, | Out of Phase 3.3 msec, In Phase 4.4 msec
380
fMRI depends on ?
T2* effects uses Blood Oxygen Level Dependent (BOLD) imaging
381
Cardiac Sequence “Bright Blood” ?
Gradient
382
Cardiac Sequence “Black Blood” ?
Double Inversion Spin Echo
383
Cardiac Sequence to Null Myocardium ?
``` Inversion Recovery (TJ. selected to match patient’s myocardium) ```
384
Magnevist
``` Gadopentetate (Gd-DTPA) Linear Ionic Oldest PDA Approved Agent Probably has the highest NSP Risk ```
385
Multihance
Gadobenate | (Gd-BOPTA) | Linear Ionic 5% Hepatocyte Uptake
386
Eovist
Gadoxetate | (Gd-EOB-DTPA) Linear Ionic 50% Hepatocyte Uptake
387
Gadavist
Gadobutrol (Gd-BT-D03A) Macrocylic Non-Ionic High Viscosity Low (none?) Risk of NSP
388
Fat Saturation Sequences Post Gad ?
NOT STIR - Inversion time is too similar
389
Gad Works By?
Increasing Spin-Lattice interactions | “Shortens” T1
390
NSF is a risk when ?
``` Renal Failure (GFR < 30) Pro-Inflammatory States (Acute Illness) ```
391
NSF highest association ?
“Omniscan” (Gadodiamide)
392
Artifact Aliasing
Direction: Phase Encoding Better: •Increase the field of view •Change the phase encoding direction Worse: Smaller FOVs Trivia:Caused by a small FOV
393
Artifact Chemical Shift Type 1
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
Artifact Chemical Shift Type 2 “India Ink”
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
Artifact Gibbs / Truncation
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
Artifact Partial Volume
Direction: Better: •Decrease Pixel Size (increase PE Steps, Decrease FOV) Worse: Thicker Slices Trivia:
397
Artifact Motion Artifact
Direction: Phase Encoding ``` Better: •Saturation pulses •Respiratory gating •Faster sequences (BLADE, PROPELLER) ``` Worse: Trivia:
398
Artifact Cross Talk
Direction: Better: •Increase slice gap •Interleave slices Worse: Trivia:Caused by overlap of slices
399
Artifact Zipper
Direction: Phase Encoding Better: Worse: Trivia:Caused by poor shielding
400
Artifact Field Inhomogeneity
Direction: Better: •Shimming Worse: GRE Sequences Trivia: Caused by geometric distortion
401
Artifact Susceptibility “Metal”
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
Artifact Eddy Current
Direction: Better: •Optimize sequence of gradient pulses Worse: DWI - large gradient changes Trivia: Caused by geometric distortion or nonuniformity
403
Artifact Dielectric Effects
Direction: Better: •Parallel Transmit •Use 1.5 T Worse: 3 T Trivia: • Standing waves created as radiowave approaches length of body part
404
Artifact Magic Angle
Direction: Better: •T2 Worse: Tl, PD Trivia: Occurs at 55 Degrees
405
MR - Safety Related Trivia Zone I
No Restriction This is basically outside the building
406
MR - Safety Related Trivia Zone II
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
MR - Safety Related Trivia Zone III
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
MR - Safety Related Trivia Zone IV
Restricted Room This is the actual MRI scanner room (the | same room as the magnet)
409
MR - Safety Related Trivia Quenching - Only if ?
There is a fire or trapped patients or staff member trapped
410
MR - Safety Related Trivia Prior to the quench ...
Get the fuck out of the room (zone 4)
411
MR - Safety Related Trivia Quench if code ?
A code is NOT a reason to quench
412
MR - Safety Related Trivia Who should push the Quench button
Medical Student, Tech, Non-English Speaking Observer.... | Anyone but you
413
MR - Safety Related Trivia 5 G Line ?
.It is an implanted device safety thing, not a pulling | (translational force) thing
414
MR - Safety Related Trivia Hearing Damage Trivia:
• Noise - from the gradient set. • Worse with Echo Planar • Damage to the fetal ossicles is part of the theoretical (complete bullshit) reason fetal
415
MR - Safety Related Trivia Neurostimulation ?
High-bandwidth readouts and rapid gradient switching | (echo-planar imaging) are the usual culprits
416
MR - Safety Related Trivia SAR Formula ?
Bo2 x Alpha2 x Duty Cycle (B = magnet strength, Alpha = Flip angle, Duty Cycle — how short your TR is).
417
MR - Safety Related Trivia SAR Limit ?
4W/kg
418
MR - Safety Related Trivia Doubling the TR will do what to the Duty Cycle?
Double the TR - will half the Dutv Cycle
419
Fat Saturation Sequences Post Gad ?
NOT STIR - Inversion time is too similar
420
Gad Works By?
Increasing Spin-Lattice interactions | “Shortens” TI
421
NSF is a risk when ?
``` Renal Failure (GFR < 30) Pro-Inflammatory States (Acute Illness) ```
422
NSF highest association ?
Omniscan” (Gadodiamide)
423
Lactation ?
Current guidelines: No need to stop breastfeeding after contrast administration. This goes for both CT Contrast (iodine) and MR Contrast (Gadolinium)
424
What agents are NOT safe with Lactation ? What are the recommendations ?
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
Precision
This is the immunity to variation
426
Accuracy Definition
This is the immunity to systematic error or bias
427
Type 1 Error
The is a false positive. | The fire alarm has gone off, but there is no fire.
428
Type 2 Error:
This is a false negative. | The house is on fire, but the alarm does NOT go off.
429
Incidence Rate
New Cases of Disease/ | Total Number of People are Risk
430
Prevalence Rate
Number of Cases of Disease/ | Total Number of People at Risk
431
Sensitivity
True Positive/ | True Positive + False Negatives.
432
Specificity
True Negative/ True Negative + False Positives *Specific Exams Rule IN Disease
433
Accuracy
True Positive + True Negative/ | TP + FP + TN + FN
434
Positive Predictive Value
True Positive/ | True Positive + False Positives
435
Negative Predictive Value
True Negative/ | True Negative + False Negative
436
Absolute Risk
Same as Incidence Rate New Cases of Disease/ Total Number of People are Risk
437
Relative Risk
Incidence of disease among persons exposed to risk factor/ | Incidence of disease among people who did NOT get exposed to risk factor.
438
Odds Radio
Cases WITH Exposure x Controls WITHOUT Exposure/ | Controls WITH Exposure x Cases WITHOUT Exposure