EXAM REVIEW Flashcards
Normalization point is the point chosen by the planner where the ________% Isodose line is placed.
100%
90%
50%
80%
100%
Which energy would give the most skin sparring?
6MeV
18MV
6MV
20MeV
18MV
Does dose falloff more rapidly with photons or electrons?
none of the above
same
photons
electrons
electrons
Does using more beams result in better homogeneity or worse homogeneity?
same
better
does not matter
worse
BETTER
Cerrobend blocks have more field conformality than MLC’s due to the
weight
MLC leaf size
field size
material
MLC leaf size
Single field treatment techniques are usually used for this type of treatment \_\_\_\_\_\_\_\_\_ brain Tspine prostate mantle
Tspine
A disadvantage of a parallel opposed treatment planning technique is
cold spots
entry and exit dose
weighting
complexity
entry and exit dose
An advantage of using a four field technique is:
max dose doubles
max dose increases
max dose stays same
max dose decreases
max dose decreases
What does VMAT stand for? Variable modulated arc therapy Variable module atomic therapy Volume mediated atom therapy Volumetric modulated arc therapy
Volumetric modulated arc therapy
A commonly used treatment site that uses a matching field technique is:
prostate
brain
larynx
craniospinal
craniospinal
Eliminates radiation dose to certain parts of an area where the beam is directed
Shielding
Allows normal dose distribution to be applied to the treated area whereas to even out the dose distribution
Compensation
Allows for a tilt in the radiation isodose curves
Wedge filtration
Where the distribution of the beam is altered by reducing the central exposure area relative to the peripheral
Flattening
The angle through which an isodose curve is tilted at the central ray of a beam at a specified depth (usually 10cm) is called the
wedge angle
hinge angle
tangent angle
isodose angle
wedge angle
The wedge factor is the ratio of the doses with and without the wedge inserted at a specified depth. T or F
True
False
True
Which type of wedge uses the motion of the collimator jaw or leaves during treatment delivery to modify the dose distribution.
motorized wedge
Physical wedge
Enhanced motorized wedge
Enhanced dynamic wedge
Enhanced dynamic wedge
MLC’s can create island blocks. T or F
True
False
False
Cerrobend blocks are composed of:
Pb, tin, cadmium, bismuth
Au, Pb, Ca, Bi
Al, tin, Pb, copper
Pb, cerro
Pb, tin, cadmium, bismuth
The melting point for Cerrobend is.
100 degrees
212degrees
165 degrees
158 degrees
158 degrees
What type of beam modifiers can be used to address tissue irregularities for sloping surfaces but today can also be used for tissue inhomogeneities inside the body?
Cerrobend
Compensators
Bolus
Flattening filters
Compensators
Bolus is used primarily to:
Limit Dmax
Block dose to certain areas
Skin sparring
Bring dose to the surface for treating superficial lesions
Bring dose to the surface for treating superficial lesions
As electron energy increases, skin dose ____________.
Stays same
Decreases
does not matter
Increases
Increases
Energy/2
50% isodose line
100% isodose line
Impractical range
Practical range
Practical range
Energy/3
50% isodose line
100% isodose line
80% isodose line
Impractical range
80% isodose line
Energy/4
50% isodose line
100% isodose line
80% isodose line
90% isodose line
90% isodose line
Pb cutout thickness for on skin electron blocking should be at least ____________
MeV/3 in cm of Pb MeV/4 in mm of Pb MeV/2 in mm of Pb MeV/3 in mm of Pb MeV in cm of Pb
MeV/2 in mm of Pb
Data registration and fusion are the geometric alignment of images with one another. T or F
True
False
True
Axial scanning provides better resolution but helical scanning is faster and delivers less dose. T or F
True
False
True
CT scans are used to create DRR’s. T or F
True
False
True
Disadvantages of using MRI include all of the following except __________________________________
distortions artifacts lack of signal from bone soft tissue imaging no relationship to electron density
soft tissue imaging
PET scans provide information about physiology rather than anatomy. T or F
True
False
True
Most common PET radionuclide is. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ DFG (deoxyfluoroglucose) GFD (glucosefluorodeox) T99 (technitium99) FDG (fluorodeoxyglucose)
FDG (fluorodeoxyglucose)
What are the 2 main types of image registrations?
vexing and convexing
rigid and deformable
Cumulative and recordable
formable and sharp
Rigid and deformable
What is the main advantage for using deformable registration?
patient position must be the same
patient position does not have to be the same
computer memory used
speed of registration
patient position does not have to be the same
IMRT stands for:
Intense modem radiating therapy
Intensity modulated radiation therapy
Intensified micro radiation therapy
Inverse modulated radiation therapy
Intensity modulated radiation therapy
What best describes an IMRT treatment:
Delivers a uniform fluence from different beam angles to generate a non conformal dose distribution
Delivers uniform fluence from different beam angles to generate a non uniform dose distribution
Delivers non uniform fluence from different beam angles to generate a conformal dose distribution
Delivers non uniform fluence from the same beam angles to generate a conformal dose distribution
Delivers non uniform fluence from different beam angles to generate a conformal dose distribution
IMRT planning assigns non uniform intensities or weights to small subdivisions of beams referred to as:
pixels
diodes
lasers
Beamlets
Beamlets
What type of planning concept does IMRT use?
Inverse
Forward
diagonal
intermediate
Inverse
IMRT is delivered most commonly using:
Wedges
MLC’s
Cerrobend blocks
Bolus
MLC’s
When treating using IMRT and using a step and shoot technique the leaves do not move when the beam is on. T or F
True
False
True
VMAT stands for:
Very magnified array therapy
Volumetric modulated arc therapy
Volume moderated arc treatmentt
Volume moderated arc treatment
Volumetric modulated arc therapy
When treating using VMAT technique radiation is delivered to the target while simultaneously moving the MLC’s and the gantry. T or F
True
False
True
SRS treatment is usually given in 5 fractions. T or F
True
False
False
SBRT stands for: Stereoscopic body radiation treatment Stereoscopic body radiation therapy Stereotactic brain radiation therapy Stereotactic body radiation therapy
Stereotactic body radiation therapy
IM-Internal Margin
expanded margin for volume differences (bladder, rectum respiration, swallowing).
ITV-Internal Target Volume
in include motion (CTV+IM)
SM-Setup Margin
Variation in daily patient positioning.
PTV-Planning Target Volume
to include all geometric variations (ITV+SM).
TV-Treated Volume
Volume to encompass prescribed dose.
PRV-Planning Organ at Risk Volume
Similar to PTV except for OAR’s
Isodose Distributions
Isodose levels are modified by changing the energy, field size, beam arrangements, beam modifiers, etc., to produce a desired dose distribution.•
Isodose Level Parameters
sodose levels are lines that pass-through points of equal dose expressed as a % relative to a reference point
Dose Volume Histogram, DVH
Two-dimensional graph showing dose delivered to volumes of interest.
Increase source size—
Increase Penumbra
Decrease Penumbra
Increase Penumbra
Increase SSD—
Increase Penumbra
Decrease Penumbra
Increase Penumbra
Increase depth—
Increase Penumbra
Decrease Penumbra
Increase Penumbra
Increase SDD—
Increase Penumbra
Decrease Penumbra
Decrease Penumbra
Planning Variables
Energy
•When choosing an energy consider the following:
- Tumor location
- Tumor size
- Surrounding tissues
- Skin sparring
- Depth
- Exit dose
Planning Variables
Beamarrangement
•Two considerations when selecting beam arrangements
•Avoid critical OAR’s (organs at risk)
•Allow homogeneous dose within planning target
-In general more beams result in better homogeneity and lower peak doses although a greater volume receives radiation
Beam arrangements that are asymmetric usually require wedges or compensators to be homogenous
Planning Variables
Field shape
- Cerrobend blocks have more field conformality than MLC’s due to the leaf size
- The blocking must always be larger than the target volume to account for penumbra
Isodose Distributions
Single field
- Advantages
- Disadvantages
- Advantages
- Simple setup
- Uses SSD technique
- Decreased treatment time
- Disadvantages
- Limited treatment depth
- Max doses
Isodose distributions
Parallel opposed fields
- Advantages
- Disadvantages
- Advantages
- Simple setup
- Decreased chance of geometric miss
- Homogeneous dose
- Ability to weight beams
- Disadvantages
- Entry and exit doses
- Difficult to avoid critical structures
Isodose Distributions
Multiple fields
- Advantages
- Disadvantages
- Advantages
- Dose conformality
- Decreased max dose
- Avoidance of critical organs
- Disadvantages
- More integral dose (total dose in body)
- Avoidance of critical organs
Isodose Distributions
Rotational therapy
- Best suited for small deep-seated tumors
- Able to shape dose distribution based on number of arcs and degree of arcs
- Decreased treatment time
- Increased Conformality of doses
- Varian linacs- Rapidarc
- Elekta linacs- VMAT (Volumetric Modulated Arc Therapy)Partial arc therapy may require “Past-pointing” where the isocenter is placed deeper than the target
Isodose Distributions
Wedge field technique
•Common uses:
- Can account for sloping anatomy such as a chestwall or breast
- Omit a beam such as a in a 3 field rectum
- Use as tissue compensator
- Use for a one sided target such as a rt sided brain tumor
- Wedge/ Hinge angle•180 - 2(wedge angle)= hinge angle
Solid individual wedges are made up of?
Pb
Steel
or both
Both (Pb and Steel)
True/False
The wedge angle is defined as the angle between the isodose curve and central axis
True
At a specified depth (10cm common) or isodose line (50% common)
Which wedge is Less restricted field sizes and more time efficient (no need to enter treatment room)
Solid Wedge
Motorized wedge
Enhanced dynamic wedge
Enhanced dynamic wedge
T/F
MLC- Multileaf collimatorLeaves move independently to generate an aperture of any shape
•Some linacs can have up to 80, 120 or 160 leaves
•Most leaf thicknesses are 1cm or less
•Made of Tungston alloy
•Uses tongue and groove design
True
T/F Some advantages of MLC’s include •Island blocking •Jagged field boundary •Field matching difficult •Penumbra is larger
False
Cerrobend blocks - Composed of •bismuth, •cadmium, •lead •tin
All •bismuth, •cadmium, •lead •tin
As photon energy increases, skin dose decreases
decreases
As electron energy increases, skin dose increases
increases
As beam angle of incidence increases skin dose increases
increases
As field size increases, skin dose increases
increases
As field size increases, MUs
decrease.
“Inverse is true”
The typical parallel-opposed set-up is treated as a ___ set-up
SSD
SAD
Both
SAD
Thickness (or IFD) can help a Physician decide what ______ to use
Field Size
Energy
SSD
SAD
Energy
- Penumbra increases with _______ air gap (or overall distance).
increase
decrease
increases
- Penumbra is wider at depth with
higher energy
lower energy
higher energy
- Penumbra is wider at the surface with
higher energy
lower energy
lower energy.
Wedges are calibrated at what depth
2cm
5cm
10cm
15cm
10cm
Subclinical malignant disease is contoured as part of the _____.
a. GTV
b. IrV
c. TV
d. CTV
e. PTV
d. CTV
A distant metastases is initially contoured as part of the __________ .
a. CTV
b. IrV
c. GTV
d. TV
e. PTV
c.GTV
Of the tumor treatment volumes listed, which is a result of treatment planning?
a. GTV, CTV, PTV
b. GTV only
c. IrV only
d. TV only
e. IrV and TV
e. IrV and TV
Which of the following treatment volumes is the largest?
a. PTV
b. GTV
c. CTV
d. OTV
a. PTV
Which treatment volume takes into account patient set-up error?
a. GTV
b. CTV
c. IrV
d. TV
e. PTV
e. PTV
PTV stands for ______.
a. Planning Tumor Volume
b. Primary Tumor Volume
c. Planning Target Volume
d. Primary Target Volume
c. Planning Target Volume
The ICRU 50 (62) deals with:
a. Regulating the volumes prescribed in radiation therapy
b. Prescribing, recording and reporting photon beam therapy
c. Monitoring advances in clinical radiation oncology
d. Internally coordinating and rationing universal healthcare
b. Prescribing, recording and reporting photon beam therapy
Which tumor treatment volume could be increased if the radiation oncologist suspected that a patient could not hold still during treatment?
a. PTV
b. CTV
c. GTV
d. IrV
e. TV
a. PTV
In a patient being treated for a parotid gland cancer, which of the following would most likely be considered an OAR?
a. GTV
b. CTV
c. TV
d. IrV
e. Brainstem
e. Brainstem
An IM can be added to accommodate all of the following treatment variables, EXCEPT:
a. variable bladder volume
b. breathing
c. movement of the gantry
d. heartbeat
e. swallowing
c. movement of the gantry
Which of the following is true concerning the ITV?
a. ITV = CTV + IM
b. ITV = CTV + GTV
c. ITV = IM + PTV
d. IM = ITV + CTV
e. IM = ITV + GTV
a. ITV = CTV + IM
Lymphadenopathy associated with a thoracic tumor would be contoured initially as part of the ____ .
a. OAR
b. GTV
c. PTV
d. None of the above
b. GTV
“Yes, that is correct. Lymphadenopathy is contoured as part of the GTV.”
A DVH, dose volume histogram, graphically summarizes the dose to various volumes for a given treatment plan.
a. Yes, this is correct.
b. No, this is not correct
a. Yes, this is correct.
The V20 of the lung is:
a. The amount of dose that 20% of the lung receives
b. The amount of lung that receives 20 cGy
c. The amount of lung that receives 20% of the prescribed dose
d. The amount of lung that receives 20 Gy
d. The amount of lung that receives 20 Gy
The V20 of the lung is approximately:
a. 2800 cGy
b. 5200 cGy
c. 35%
d. 95%
c. 35%
Hitn “The answer is 35% b/c at 2000 cGy the graph was at 35%.”
(Graph is used)
The point dose to the left parotid is approximately:
a. 2800 cGy
b. 1700 cGy
c. 7000 cGy
d. 5600 cGy
d. 5600 cGy
Hint “The answer is 56Gy b/c that’s the total dose that is received
In this DVH, the PTV_HR_4mminSkin (shown in red) states that:
a. 100% of the volume will receive at least 95% of the dose
b. 100% of the dose will cover 95% of the volume
c. Both of the above
c. Both of the above
In the previous question, if the physician changes his/her prescription from an energy of 15MV to an energy of 6MV (with all other criteria the same), what happens to the MUs?
a) Increases
b) Decreases
c) Stays the same
a) Increases
Hint “Yes, this is correct. Lower energy beams are less penetrating, requiring more MUs to deliver dose to a given depth.”
In an SAD AP/PA set-up, if a patient has an IFD of 30 cm and is being treated to midplane, what is the PA SSD?
a) 100
b) 70
c) 85
d) 130
e) 115
c) 85
Generally speaking, as the field size increases, the number of necessary MUs:
a) Increases
b) Decreases
c) Stays the same
b) Decreases
In the previous question, the physician increases the field size to cover two additional vertebral bodies. All other set-up criteria remain the same. The number of MUs:
a) Increases
b) Decreases
c) Stays the same
b) Decreases
Hint “Yes, this is correct. As field size increases, the number of MUs needed decreases due to the additional scatter.”
In an SSD PA set-up, if a patient has an IFD of 30 cm, and is being treated to a depth of 4 cm, what is the PA SSD?
a) 100
b) 70
c) 85
d) 130
e) 96
a) 100
It is common to treat the spinal cord with laterals in what area of the spine?
a) Cervical
b) Thoracic
c) Lumbar
d) All of the above
a) Cervical
A typical beam arrangement for thoracic spine treatments is:
a) AP only or AP/PA
b) AP only or laterals
c) PA only or laterals
d) PA only or AP/PA
d) PA only or AP/PA
A patient is being treated with an AP/PA set-up, SAD. The AP SSD is 87. The PA SSD is 92. What is the thickness (IFD) of the patient?
a) 13
b) 21
c) 8
d) 26
b) 21
A field size for a whole brain is 17 x 25 cm. Later, the field size is increased. Will the MUs necessary to deliver the prescribed dose:
a) Decrease due to scatter
b) Increase due to scatter
c) Remain the same because the prescription did not change
a) Decrease due to scatter
If the patient is accidently treated SAD, but was planned SSD, the patient will be:
a) Overdosed
b) Underdosed
c) Neither, as long as the prescription did not change
a) Overdosed
If the treatment is set up SSD and accidently treated SAD:
a) The light field will appear larger on the patient
b) The light field will appear smaller on the patient
c) The light field will be the same on the patient as long as the field size does not change
d) The light field will not be on the patient’s brain, but will appear on his lower neck
b) The light field will appear smaller on the patient
If a patient is set up for an SSD whole brain and the collimator is 25 on the right side, the collimator angle on the left side will be:
a) 25 degrees
b) 155 degrees
c) 335 degrees
d) 65 degree
e) 115 degrees
c) 335 degrees
The two most commonly used bony landmarks in a whole brain set-up are:
a) The maxillary bone and the mastoid tip
b) The orbital canthis and the mastoid tip
c) The orbital canthis and C2
d) The inferior border of the eye and C2
b) The orbital canthis and the mastoid tip
A whole brain patient is set up SAD, and to midplane. If his IFD is 18, what will you expect his SSD to be?
a) 8
b) 82
c) 91
d) 118
d) 100
c) 91
A whole brain patient is set up SSD. If his IFD is 15, what will you expect his SSD to be?
a) 7.5
b) 81
c) 91
d) 92.5
d) 100
d) 100
Which electron energy has the most penetrating power?
a) 6 MeV
b) 4 MeV
c) 9 MeV
d) 21 MeV
e) 15 MeV
d) 21 MeV
Which electron energy has more surface dose?
a) 6 MeV
b) 4 MeV
c) 9 MeV
d) 21 MeV
e) 15 MeV
d) 21 MeV
Hint “Higher energy more surface dose”
What is the practical range of 21 MeV electrons?
a) 7 cm
b) 3 cm
c) 10.5 cm
d) 5.25 cm
e) 21 cm
c) 10.5 cm
Hint “E/2”
The 80% line for 6 MeV electrons is approximately:
a) 2 cm
b) 3 cm
c) 1.5 cm
d) 4 cmIn
e) .78 cm
a) 2 cm
Hint “E/3”
If you increase the air gap in an electron calculation, the number of monitor units will:
a) Increase
b) Decrease
c) Stay the same
Hint “Yes, this is correct. The dose rate decreases as the patient moves farther away, so more monitor units are required to deliver the same dose “
In which of these cases could electrons be reasonably used:
1. A patient with a lymph node 4 cm below the skin surface
2. A patient with a small lesion 4 cm anterior to the spinal cord
3. A patient with a small lesion 4 cm superior to the seminal vesicles
4. A patient with a 4 cm small lesion on the scalp
a) 1 only
b) 2 only
c) 1 & 2
d) 1 & 4
e) All of the above
d) 1 & 4
If you increase the output factor in an electron calculation, the number of monitor units will:
a) Increase
b) Decrease
c) Stay the same
b) Decrease
Which electron energy has a broader isodose shoulder?
a) 6 MeV
b) 12 MeV
c) 4 MeV
d) 21 MeV
d) 21 MeV
Which is true concerning electron penumbra?
1. Electron penumbra increases with air gap and overall distance
2. Penumbra is wider at depth with higher energies
3. Penumbra is wider at the surface with higher energies
a) 1 only
b) 2 only
c) 1 & 2
d) 1 & 3
e) All of the above
c) 1 & 2
