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Treatment Planning

RTTP

QuestionAnswer
What does spatial resolution measure? Detail in a CT image
Define treatment planning The process by which dose delivery is optimized for a given patient and clinical situation
What are the four most desired qualities of CT images? spatial resolution, image contrast, low noise, and low dose
Spatial resolution refers to the clarity or the measure of detail in a CT image. T/F True
Orthogonal images are two images taken at right angles to one another. T/F True
The right lymphatic duct drains the upper left part of the body. T/F False, it drains the upper right part of the body
In CT simulation, what are the two most common methods by which contrast media may be introduced into the body? oral and intravascular
Barium sulfate is water soluble. T/F False
Barium sulfate should not be used when there is a risk of perforation in the gastrointestinal tract. T/F True, it is not water soluble
At what vertebral level does the thoracic lymph duct begin in the abdominal cavity? L2
Optical components of a fluoro-based simulator include the laser system, ODI and field light indicator. T/F True
The SAD approach to treatment planning places the isocenter within the target volume with the aid of imaging modalities. T/F True
The SAD treatment planning approach is also known as what technique? Isocentric technique
Isocentric technique provides tumor localization in three dimensions. T/F True
Name three commonly used contrast media for simulation procedures. Barium sulfate, iodinated contrast materials, and negative contrast agents such as air
What is maximum intensity projection, or MIP? Fused scan that shows the maximum amount of tumor movement during the respiratory cycle
Varying electron densities displayed as pixels in shades of gray on an imaging display are called what? Hounsfield units
Hounsfield numbers which correspond to the electron density of specific tissue such as lung, soft tissue, and bone are set to a scale of -100 (for air) to +100 (for dense bone) T/F False, the scale is -1000 to +1000
What is window width on a CT image? The range of numbers displayed or the contrast on a CT image
Narrowing the window width results in a reduction in contrast. T/F False, narrowing the WW results in greater contrast or sharper changes in the shades of gray
The term window level represents the central HU of all the CT numbers within the window width. T/F True
DICOM (Digital Imaging and Communications in Medicine) is an electronic network and is the standard image format to transfer information between imaging devices and the treatment planning computer. T/F True
Patient positioning is one of the weakest links in treatment planning. T/F True
Solid-state detectors of a CT scanner are designed to convert radiation into light. T/F True
What is noise on an image? Noise is considered any undesirable characteristic detracting from image quality
What is the term for the ratio of the absorbed dose at a given depth to the absorbed dose at the same point in air? Tissue Air Ratio (TAR)
What is the term for the ratio, expressed as a percentage, of the absorbed dose at a given depth to the absorbed dose at a fixed reference depth, usually Dmax? Percentage Depth Dose (PDD)
What is the practical range in tissue for a 6 MeV electron beam? 3 cm
To find the practical range in centimeters in tissue for electron beams, you would divide the energy of the electron beam in MeV by 2. T/F True
The depth of the 80% isodose line in centimeters in tissue for an electron beam is calculated by dividing the energy of the electron beam in MeV by 2? T/F False, 80% isodose line is found by dividing the MeV by 3
What is the formula used to find the 90% isodose line in centimeters in tissue for an electron beam? 90% isodose = MeV/4
How do you find the dose per port for a treatment with two ports that are not equally weighted? You would divide the total dose by the sum of the weighting ratio. That answer can then be multiplied by the weighting for each port
What do flattening filters do for photon beams? Flattening filters reduce the increased photon intensity existing in the center of the beam. The flattening filter is designed to produce a “flat” intensity pattern at some predefined depth (normally 10 cm)
Inverse planning systems calculate dose distributions and create MLC patterns based on initial dose delivery and avoidance parameters. T/F True, IMRT is often “inverse planned”
Forward planning requires that dose-altering parameters and beam modifiers be entered into the treatment plan by the planner. T/F True, 3D-CRT uses conventional forward planning
Disease that is visible on CT and palpable is A) gross tumor volume GTV; B) clinical tumor volume CTV; C) planning target volume; D) treated volume A) gross tumor volume GTV
A geometric volume that has dimensions believed to A tissue volume containing visible/palpable and/or subclinical microscopic malignant disease is A) gross tumor volume GTV; B) clinical tumor volume CTV; C) planning target volume; D) treated volume B) clinical tumor volume CTV
Contains visible/palpable and/or microscopic malignant disease as well as taking into account setup uncertainties and patient and/or organ motion is A) gross tumor volume; B) clinical tumor volume; C) planning target volume; D) treated volume C) planning target volume PTV
The tissue volume enclosed by the isodose surface selected as being appropriate to achieve the purpose of treatment is A) gross tumor volume; B) clinical tumor volume; C) planning target volume; D) treated volume D) treated volume
Beam’s eye views (BEVs) are images reconstructed from CT data that represent the patient’s anatomy and defined volumes from the perspective of the treatment beam. T/F True, treatment fields are often designed from BEVs
Treatment planning systems often combine CT images with images from other modalities. What is this called? Image fusion or image registration
A frequency distribution of the number of target or normal structure voxels (volume elements) receiving a certain dose is called the what? Dose-volume histogram (DVH). The DHV is a plot of target or normal structure volume as a function of dose
Why is the dose-volume histogram (DHV) an important tool in radiation therapy treatment planning? Allows for an evaluation of a patient’s treatment plan after dose calculations have been completed. The information shows if you fall within the target dose homogeneity and normal tissue protection constraints that you have set for a treatment.
Define gradient The rate of change of a value (dose) with a change in position
A scattering foil is used to widen a photon beam. T/F False, they are used to widen the “pencil beam” of electrons
What is Sterling’s formula and what is it used to calculate? 4 x Area/Perimeter, it is used to calculate the equivalent square of a rectangular field
The use of a moving collimator jaw to produce a wedged field is often termed what? Dynamic wedge
Which nodes are commonly involved with primary breast cancers located in the inner breast quadrants and when there are positive axillary nodes? Internal mammary nodes
The junction of the manubrium and the body of the sternum form the sternal angle at T4, this is also called the what? Angle of Louis
The cartilage that serves as the lower border of the larynx and is the only complete ring of cartilage in the respiratory passage is the what? Cricoid cartilage, at the level of C6
Rotter’s node is located in the supraclavicular triangle? T/F False, it is in the supraclavicular fossa
What are four commonly used bony surface landmarks of the posterior pelvis? lateral iliac crests, iliac crests, coccyx, and the posteriosuperior iliac spine
The lymphatic pathways and nodes of the abdomen are often referred to as what? Visceral nodes
Most breast tumors are located in what quadrant? Upper outer quadrant
The principle pathway of of lymph in the breast involves collection in the lobules that follow ducts, which anastomose behind the areola. T/F True
Created by: susan27