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RAD 370 - Techniques and Applications > Test 2 > Flashcards

Test 2 Flashcards

1
Q

Process carried out by therapist under the supervision of the radiation oncologist; part of treatment planning procedure, which delineate the treatment field and construct any necessary immobilization or treatment devices

A

Simulation

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2
Q

Geometric definition of position and extent of tumor volume and critical normal structures by using x-ray, CT, MRI and/or PET

A

Localization

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3
Q

Final check to ensure each of the planned treatment beams cover the tumor or target volume and don’t irradiate critical structures; port films

A

Verification

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4
Q

Small markers are often used to mark specific points on a patient during CT; ex: vaginal or rectal, wire for breast or scars (seeding)

A

Radiopaque marker

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5
Q

Measurement with calipers of a patient along the central axis or at any other specified point within the irradiated volume

A

Separation

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6
Q

Dimensions of treatment field at isocenter determined by the collimator opening in simulation software, treatment planning system, and on the treatment unit

A

Field size

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7
Q

2D image reconstructed from CT data that shows a beam’s eye view of the treatment field created at isocenter

A

Digitally reconstructed radiograph (DRR)

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8
Q

Change in target position from one fraction to another due to setup error, change in marks, etc.

A

Interfraction motion

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9
Q

Change in target position during treatment delivery; ex: respirations in thorax, gas in bowel, etc.

A

Intrafraction motion

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10
Q

Palpable/solid tumor, macroscopic disease; different margins created in treatment planning computer

A

Gross tumor volume (GTV)

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11
Q

GTV and surrounding volume of tissue that may contain subclinical or microscopic disease too small to visualize

A

Clinical target volume (CTV)

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12
Q

CTV plus margins for geometric uncertainties; ex: patient motion, treatment setup differences (distance change, etc.), and penumbra

A

Planning target volume (PTV)

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13
Q

Outer edges of radiation beam less intense

A

Penumbra

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14
Q

CTV plus an internal margin that accounts for tumor motion; ex: gating for lung

A

Internal target volume

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15
Q

Volume of tissue receiving a significant dose (over 50%) of the specified target dose

A

Irradiated volume

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16
Q

Difference between SSD and SAD setups

A

Changing isocenter; SAD at depth, SSD to skin

SSD requires more MUs because it’s further from treatment and have to move patient every time we move to new field

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17
Q

Two films taken at right angles/90° to one another; gives more information about depth and can see superimposed structures (ex: four field pelvis)

A

Orthogonal films/orthogs

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18
Q

Distance from target of radiation to the imager

A

Target-image receptor distance (TID)

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19
Q

3 commonly used contrast media

A

Barium Z #56 (drink a lot of water)
Ionic or nonionic iodinated Z #53
Negative: air

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20
Q

About ____% of anaphylactic reactions happen in about 5 minutes; usually occur within ____ min

A

70%; 30 min

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21
Q

When to use contrast for head and neck

A

Power injector seconds before scan to highlight vessels and distinguish them from lymph nodes (LN) or mass

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22
Q

When to use contrast for brain

A

IV push 10-30 minutes before scan because tumors are very vascular

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23
Q

When to use contrast for liver (abdomen)

A

Power injector 20-40 seconds before scan to visualize hepatic arterial phase and 60-90 seconds before to see venous phase

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24
Q

3 contrasts used for pelvis

A

IV push at least 15 minutes before scan for prostate to highlight bladder
Radiopaque marker for rectum (critical structure)
Barium 30-60 minutes before to see small bowel

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25
Q

3 contrasts used for GI tumors

A

Barium paste to coat esophagus
Dilute barium sulfate solution to highlight stomach or small bowel
Barium 30-60 minutes before to see small bowel

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26
Q

Deliver high dose to small volume, usually the GTV only, excluding regional lymph nodes or OARs

A

Boost fields

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27
Q

2 methods of CT simulation

A

Shift method

No-shift method

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28
Q

Reference marks placed on patient before CT
Later physician/dosimetrist determines treatment isocenter coordinates
Shifts between the marks placed on the patient while they’re on the CT scanner and the treatment isocenters are calculated
Initial reference marks removed and new treatment isocenters are marked on patient
Zero out isocenter

A

Shift method

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29
Q

Patient scanned and while patient is on couch, images reviewed by doctor and the treatment isocenter is determined based on the areas contoured on the images; isocenter coordinates programmed into the moveable lasers in scanner room and patient is marked accordingly

A

No-shift method

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30
Q

Patient has coordinates related to table they’re at every treatment

A

Registering/indexing patient to table

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31
Q

Respiratory gating currently used to account for moving tumor volumes

A

4D CT

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32
Q

Provides physiologic function by using the beta decay radiotracer 2-fluoro (fluorine 18) fluoro-2-deoxy-D-glucose (FDG) which accumulates in organs with high glucose utilization, which occurs in areas of more metabolic activity such as disease sites
Can be fused with CT acquired during simulation and used for treatment planning; maintains position which is very desireable

A

Positron emission tomography (PET)

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33
Q

Offers better soft tissue contrast and resolution than CT but inherently has some geometric distortion

A

MRI

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34
Q

External representation of patient’s surface/topography

A

Contour

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35
Q

4 contour devices

A

Lead solder wire
Plaster of paris
Aquatube
CT (best)

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36
Q

CPR compressions to breaths ratio

A

30 compressions : 2 breaths

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37
Q

Process of aligning multiple data sets into a single coordinate system so that the spatial locations of corresponding points coincide

A

Registration

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38
Q

5 types of image-guided radiation therapy (IGRT)

A 
Ultrasound (around 2000, prostate)
On-board imager (OBI)
Exac Trac from BrainLab
CT-on-rails
Cone beam CT (CBCT)
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39
Q

kV imager provides better soft tissue contrast than MV (depends on electron density)
Generally only used to view anatomy because it has different geometry than treatment
Mounts x-ray unit and IR system by using robotic arms on the accelerator gantry at 90° from electronic portal imaging device (EPID)

A

On-board imager (OBI)

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40
Q

Not attached to the accelerator and uses two floor-recessed x-ray units and two ceiling mounted amorphous silicon flat panel detectors
Images from system can be analyzed and couch corrections calculated to position the patient before treatment
Infrared tracking system used to track patient during treatment

A

Exac Trac from BrainLab

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41
Q

CT in treatment room
Accelerator treatment table rotates 180° and CT unit moves on rails while patient is imaged with couch in a stationary position

A

CT-on rails

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42
Q

At certain degree intervals during rotation of gantry single projection images are acquired; ex: 1°
These different angle images are slightly offset from one another and are the basis upon which 3D volumetric data sets are generated
Net result is a 3D reconstructed data set, which can project images in three orthogonal planes (axial, sagittal, and coronal)
Final product is 3D data set with patient in treatment position

A

Cone beam CT (CBCT)

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43
Q

MV imager, photoelectric depends on Z^3/E^3 = grainy images

A

Electronic portal imaging device (EPID)

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44
Q

2 forms of respiratory motion management

A

Abdominal compression

Gated treatments

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45
Q

Respiratory cycle

A

Adult at rest breathes in and out 12-16 breaths per minute

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46
Q

Tracks tumor and radiation is turned on when the target is within the treatment volume and radiation is turned off when target is outside target volume
Increases treatment time

A

Gated treatments

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47
Q

2 gated treatment devices

A

Real time positron management system (RPM)
Electromagnetic transponder near x-ray tube reads movement 10-12 times per second by using electromagnetic detector system

48
Q

Lesions in lower lobe of lung movement as much as ____ mm in the superior inferior directions and as much as ____ mm in the AP and left and right lateral directions

A

Lesions in lower lobe of lung movement as much as 12 mm in the superior inferior directions and as much as 5 mm in the AP and left and right lateral directions

49
Q

In a study of 22 patients, 10 showed no tumor motion in the superior-inferior direction, in remaining 12 patients. ___-___ mm motion

A

3-22 mm

50
Q

Therapy that delivers nonuniform exposure across the radiation field using a variety of techniques and equipment

A

Intensity modulated radiation therapy (IMRT)

51
Q

Therapy that with the use of 3D treatment planning, allows the delivery of higher tumor doses to selected target volumes without increasing treatment morbidity; set specific shapes in and around a volume to exclude critical structures

A

Conformal radiation therapy (CRT)

52
Q

Used to define a coordinate system in the treatment planning and delivery process

A

Fucidals

53
Q

4 IMRT delivery methods

A

Physical modulators: brass block, .decimal pieces
MLC’s: bimodal - open or shut
Arc therapy
Fan beam

54
Q

2 types of MLC’s

A

Static

Dynamic

55
Q

Machine turns off when field moves

A

Static MLC

56
Q

Constantly moving MLC

A

Dynamic

57
Q

Radiation therapy delivered while the gantry moves through its arc of rotation, thus effectively delivering radiation through a continuous sequence of individual overlapping treatment portals; ex: ion linacs

A

Arc therapy

58
Q

Treatment unit where the linac rotates continuously while the treatment couch moves through the gantry bore producing a spiral treatment beam
First treatment machine capable of spiral/arc therapy
Like CT but has the 6 MV tube in it

A

Tomotherapy

Fan beam

59
Q

Lower dose of radiation is released at the surface but a sharp burst of radiation is released as the beam reaches the tumor site
Stops at the tumor, leaving the healthy cells beyond it unaffected
The beam can be contoured to the exact shape of the tumor, further decreasing radiation exposure and limiting side effects
High dose to tumor volume near critical structures

A

Proton therapy

60
Q

Sum of several individual Bragg peaks at staggered depths that provides a useful beam over a greater range in patient; maximum energy can treat the entire tumor from the most distal to proximal edges

A

Spread-out Bragg peak (SOBP)

61
Q

8 times radiation therapy with protons can be used

A 
CNS
Prostate (right and left lateral)
Lung
Ocular
Head and neck
Esophagus
Pediatric
Retreatment possibilities (limit dose to previously treated area)
62
Q

Placing the radiation sources in or at close proximity to the treatment volume and away from normal tissue, very high tumoricidal doses of radiation can be delivered to the target area while sparing surrounding tissues and organs at risk (OARs)
Isotopes placed right up against tumor/islands at very high dose close to proximity to radiation
Short amount of of time, treatment at a short distance
Supplemental boost treatment
Up to 100 Gy
Immediate
Low dose to critical structures because it falls off rapidly

A

Brachytherapy

63
Q

Time source is in body determined by activity, etc.

A

Dwell time

64
Q

4 applications of brachytherapy

A

Interstitial
Intraluminal
Topical/surface
Intracavitary

65
Q

Placement of radioactive sources directly into a tumor or tumor bed; commonly used in neck, breast, prostate, and soft tissue sarcoma treatment (ex: catheters in breast or skin)

A

Interstitial brachytherapy

66
Q

Placement of radioactive sources in body tubes such as esophagus, trachea, bronchus, and endometrium via catheters

A

Intraluminal brachytherapy

67
Q

Placement of radioactive sources on top of area to be treated; ex: skin, eye plaque, etc.

A

Topical/surface brachytherapy

68
Q

Placement of radioactive sources within a body cavity; ex: cervical

A

Intracavitary brachytherapy

69
Q

3 roles of source strength

A

Provides a commonly accepted means for measurement when describing quantities of emitted radiation
Provides practitioners dose calculations
Serves as a prescription basis

70
Q

Rate of decay
Quantity of radiation emitted from the source to be used; describes strength of a source
Number of disintegrations per unit time

A

Activity

71
Q

Traditional unit of activity; 1 gram of radium

A

Curie (Ci)

72
Q

SI unit of activity

A

Becquerel (Bq)

73
Q

1 Ci = ? disintegrations per second

A

3.7 x 10^10 disintegrations per second

74
Q

1 Bq = ? disintegrations per second

A

1 disintegrations per second

75
Q

3.7 x 10^10 Bq = ? Ci

A

1 Ci

76
Q

Total number of atoms that decay per unit time

A

Radioactive decay

77
Q

Decay constant

A

λ = 0.693/half-life

78
Q

Decay constant and activity are ________ while half-life and activity are ________ (takes longer = less activity present)

A

Proportional; inversely proportional

79
Q

Activity formula

A

At = Aoe^-λt

Ao = initial source activity
At = activity after time
80
Q

Average lifespan for decay of radioactive atom/source

Know when last half-life (T^1/2) of permanent implant is

A

Mean life

81
Q

Mean life formula

A

T^1/2(1.44)

82
Q

2 permanent implants

A

Gold-198

Iodine-125

83
Q

First isotope used in brachytherapy, equivalent substitutes used today
Brachytherapy sealed, encapsulated

A

Radium

84
Q

Disadvantage of radium

A

Daughter product radon can leak as gas and be harmful because of its high specific activity

85
Q

Activity per unit mass of radioactive material

A

Specific activity

86
Q

Actual length of source (shorter/smaller)

A

Active length

87
Q

Capsule length (longer)

A

Physical length

88
Q

Measures air kerma strength

A

Exposure rate

89
Q

Mass of radium required to produce the same exposure rate at 1 cm from the substitute source

A

mg-Ra-eq

90
Q

1 mg-Ra-eq = ? mCi

A

0.98 mCi

91
Q

3 methods for applying brachytherapy

A

External/mold applicators
Interstitial applicators
Intracavitary applicators

92
Q

Surface lesions requires higher localized doses; ex: eye plaque

A

External/mold applicators

93
Q

2 interstitial applicators

A

Permanent

Temporary

94
Q

Interstitial applicators used when tumor is inaccessible; deep-seated tumors like lung, abdomen, pelvis, etc.

A

Permanent

95
Q

No body cavity or orifice to accept source so it’s placed near tumor and removed later

A

Temporary interstitial applicators

96
Q

3 intracavitary applicators

A

Tandem and ovoids
Heyman capsules
Vaginal cylinders

97
Q

Intracavitary applicator inserted through cervical os into endometrium/uterus

A

Tandem

98
Q

Intracavitary applicators set in fornices of cervix

A

Ovoids

99
Q

Intracavitary applicator in uterus, can be used with tandems (only one point of source) and offers the best dose distribution

A

Heyman capsules

100
Q

Used for uveal melanoma of eye (most common eye CA but rare)
Stitched and placed in eye
Source: Iodine-125 (low energy)
Thin layer of gold on outside shields radiation from getting out
5000 cGe (cGy equivalent because it takes alpha beta ratio into effect/biological effect)
Only takes a couple days

A

Eye plaque

101
Q

Measures length of uterus (don’t want to perforate it)

A

Uterine sound
Histometer
Fletcher suit

102
Q

3 hand calculations

A

Paterson-Parker/Manchester system
Quimby/Memorial system
Paris system

103
Q

Uses nonuniform distribution of radioactive material and produces a uniform dose distribution based on how sources are placed in patient
+/- 10% accurate
Uses specific points: A, B, P, rectum, and bladder

A

Paterson-Parker/Manchester system

104
Q

2 ways to calculate Paterson-Parker/Manchester system

A

Planar implants

Volume implants

105
Q

Sources in order, calculation based on shape

A

Planar implants

106
Q

Representation of sources takes specific shape

A

Volume implants

107
Q

Uniform distribution of activity within the implant; 1 cm apart
Rectilinear

A

Quimby/Memorial system

108
Q

Uses uniform distribution of the radiation sources like Quimby; rectilinear

A

Paris system

109
Q

Distance paths/lines which are always parallel to the axis at right angles

A

Recitlinear

110
Q

Used today, can be checked by hand calculations

A

Computer calculation method

111
Q

2 cm lateral to the midline of the cervical canal/tandem/patient 2 cm superior to cervical os/end of the tandem
Can go from midline of tandem because patient’s cervical canal may not be exactly midline
Uterine vessels cross ureters at this point; critical structures that limit dose

A

A

112
Q

3 cm lateral of point A, 5 cm lateral to patient’s midline

A

B

113
Q

1 cm further lateral to point B

A

P

114
Q

At point of foley catheter

A

Bladder

115
Q

5 mm posterior to vaginal wall

A

Rectum

116
Q

Tandem and ovoids distribution ______-shaped because of ovoids; get better coverage
Dose falls from inside-out

A

Pear

117
Q

Measures uniformity of dose

A

Autoradiograph

RAD 370 - Techniques and Applications (6 decks)

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