Accuracy and Immobilisation Flashcards
What is the definition of accuracy?
closeness of agreement between measured quantity and it’s true value
What is the definition of Precision?
The closeness of the results when the same measurement is made repeatedly
What is the definition of Error?
difference between the measured quantity and its reference value.
What is the definition of setup error?
discrepancy between intended and actual treatment position. It comprises a systematic and random component.
What is a systematic error?
deviation that occurs in the same direction and is of a similar magnitude for each fraction throughout the treatment course.
What is a random error?
error is a deviation that can vary in direction and magnitude for each delivered treatment fraction.
What are systematic errors?
Target delineation error
Patient set up error
What is a phantom transfer error?
accumulates when transferring image data (systematic)
What is an individual systematic error?
error for an individual patient is the mean error over the course of trea
What is an population systematic error?
error for a group of patients is an indication of the spread of individual mean errors
What is a random error?
occur at the treatment delivery stage and for this reason are often referred to as treatment (or daily) execution errors
What is an Infra-fraction errors?
changes in the patient’s position and internal anatomy arising during the delivery of a single fraction,
What is individual random error?
random error for an individual patient is the standard deviation (SD) of the measured errors over the course of treatment and quantifies the spread of errors.
What is random error for a population?
random error for a group of patients is calculated as the mean of the individual random errors and is given the lower case sigma symbol (σ).
What is an action level or maximum permissible error?
difference between measured value and it’s expected or reference value
