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Treatment Planning
RTTP
| Question | Answer |
|---|---|
| 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
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