A. Different treatment types and procedures Flashcards
_______ Radiation Therapy Conforms the radiation beam so that the target volume receives the prescribed dose and the surrounding healthy tissue receives a much lower dose
3-D Conformal
Planning uses 3D imaging such as ______
computed tomograpy
________ is a monoenergetic beam that is used to treat superficial tumors
Electron beam
- mono energetic beam
- treat superficial tumors <5 cm deep
- 6-20 Mev
Electron beams Scatter easily in
air
Electron beams r equires a cone to confine the beam closer to the
patient’s skin surface
Electron beam field edges balloon out because of _____and aren’t definitive like photon beams
scatter
For electron beams, there is a “rapid falloff” of dose, which means that
deeper organs and tissues will receive very little or no dose
For electron beams there is _____________, which means more dose to the skin compared to photons
Less skin sparing
_____ is a radiation beam that has varying intensities throughout the beam
IMRT
IMRT has Many smaller beams or “beamlets”. Beamlets are commonly as small as
1 cm x 1 cm
T/F for IMRT the dose is uniform
FALSE
IMRT allows for higher doses to tumors while minimizing doses to
surrounding healthy tissues
IMRT uses _____ treatment planning and dynamic MLCs
inverse
______ treats small tumors within the cranium at a high dose
SRS
SRS treats tumors with how many fractions?
One
SRS tumors are normally less than ____Cm
3cm
Treatment positioning must be +/- ___mm
1mm
SRS of intracranial lesions may require
a frame attached to the patients head
What are the common disease treated with SRS that are in the cranium?
AVMS, trigeminal neuralgia, acoustic neuromas, meningiomas, pituitary adenomas, metastatic and primary brain tumors, less common in spine
What are some examples of machines that preform SRS treatment?
Gamma Knife and Cyber Knife
______ treats small tumors outside of the cranium with a very high dose for about 3-5 fx
SBRT
_____ is a type of radiation therapy that targets the whole body to prepare for bone marrow transplants and to treat other malignancies
TBI
_____ is used prior to treatment to confirm patient position
Image Guided Radiation Therapy (IGRT)
What are examples of IGRT
EPID, KV, MV cone beam, Ultrasound
_____ = high energy charged particles such as protons, alpha particles, and carbon ions
Particle beam radiotherapy
______ is the dose curve of a proton beam. It starts off low at the beginning but then rapidly rises toward the end of the path. Then abruptly falls to zero.
Bragg peak
___________ Helps to position the patient for treatment
Patient positioning aids
Positioning aids do NOT….
limit the patient’s movement
What are positioning devices than can be used for multiple patients
head holders, sponge pillows, foam cushions, neck rolls
________________ immobilization devices- Limit the patients movement and create a very reproducible setup
Complex
Complex immobilization devices are Customized for each patient. What are some examples?
alpha cradle, vac-lok, thermoplastic molds, bite blocks
_______immobilization devices Help to constrain patient
Simple
Simple immobilization devices are Used with positioning aids. They are Not as restricting as complex immobilization devices. What are some examples?
tape, rubber band, arm-to-foot straps
When is contrast used?
simulation
What does contrast do to help create the treatment plan?
It will highlight specific organs
What can contrast highlight?
Area to be treated and critical structures to be avoided
______ contrast agents appear radiopaque (white) on radiographic imaging due to high atomic numbers
positive
What are examples of positive contrast agents?
iodine, gadolinium, and barium
______ contrast agents appear radiolucent (black) on radiographic imaging due to low atomic numbers
negative
What are some examples of negative contrast agents?
air, oxygen, carbon dioxide, and nitrous oxide
_____ is the most common imaging modality used for RT treatment planning
computed tomography (CT)
CT simulators create ____ images
3D
CT images are produced by
X-ray, detectors, and computer
the CT scanner follows A XYZ axis
Z axis = length of patient
x axis = width
y axis = height
CT images are acquired through
Spiral or helical scanning
_____ is the thickness of the section in the patient that contributes to echo signals on any one image
slice thickness
Slice thickness is Controlled by pre-patient collimation within the
CT gantry
Thinner image slices are a result from _________ collimation that narrows the x-ray beam
more
___________ slices reduce scatter and create better image quality
thinner
Typical CT simulation slice thickness is ___ to ___ mm
2-3 mm
One CT slice delivers __to___ cgy at the skin’s surface
1 to 6 cGy
Spacing between CT slices should be less than ____
5 mm
__________ space between the slices leads to less information obtained by the scan and more interpolation performed by the computer algorithms
more
What are two key factors for generating high-quality DRRs?
slice thickness and space between slices
_____ Measures the beam quantity, or how many x-rays are produced
mA
mA Increase leads to higher
patient dose
mA is a Technical factor used to create a
high-quality image
CT image displays use a matrix size of _______ x _______
512 X 512
CT images are a display of many small pixels with different shades of gray, depending on the
attenuation rate or Hounsfield units
the number of shades of gray displayed on an image or the contrast of the image.
window width (WW)
A _____ window width has more contrast
narrow
the median shade of gray or hounsfield unit within the window width
Window Level (WL)
Window level changes the image
brightness
An increase in window level creates a
darker image
A decrease in window level creates a
brighter image
_____ is a value that represents a shade of gray
CT number
CT number is also known as the
Hounsfield Unit (HU)
CT number represents the _____ of different tissues
density
For CT number the shade of gray is determined by
how the structure attenuates the x-ray beam
What is CT number for air
-1,000
What is CT number for water
0
What is CT number for bone
1000
____ is where the computer uses algorithms to create the CT image in different planes
Reconstruction
Where are reconstructed CT Images first acquired?
the axial plane
CT Images are reconstructed to be viewed in the _______ planes
coronal and sagittal
During a _______, raw data is acquired during a scan and it is then reconstructed into image data to be viewed
CT simulation
The computer assigns each pixel an HU to become _______ in reconstruction of image
image data
The amount of raw data used to create or display an image
display field of view (DFOV)
Area of interest to be scanned
Scan field of view (SFOV)
_______ is a 3-D image taken in the treatment position that provides data of the anatomy of the patient, such as the skin, tumor and other organs within the body
contour
Contours are necessary for creating accurate treatment plans and
calculating doses
In the _______ ( treatment planning system) the physician can identify the treatment borders and the isocenter location
Virtual simulator
What does DICOM stand for
Digital imaging and communication in medicine
DICOM is used to
Transfer of images and patient reports to planning computers
Used to store and share images
PACS
____ lasers are at a fixed distance from the internal scanner lasers usually 500mm (50cm)
External
___ lasers are mounted to the side of wall and project vertical and horizontal directions
Wall
_____ laser is a single laser located on the ceiling and is moveable. It moves in the left/ right position. Important since CT table cant move Lt/Rt.
Sagittal
___ lasers are internally mounted within the gantry bore
Scanner
Who created Sim order
Radiation oncologist
What should be included in Sim order?
Patient position, body part to be simmed, laterality of body part, contrast instructions, and immobilization technique
what is Non - volumetric arc therapy ?
used for small tumors
- where gantry rotates but the mlc stay stationary
- 3D plan
you can find the range depth in electron by doing
Mev/2
