MOSAIQ User's Guide - UCSF Radiation Oncology

Appendix D: Measurement of Accuracy for Medical Devices
Appendix D: Measurement of Accuracy for
Medical Devices
MLC Fit
MLC Leaf resolution may be characterized to 0.10 cm or 0.01 cm. MLC Fit calculates the leaf positions
for a machine to a resolution of either 0.10 cm or 0.01 cm based on this MLC resolution setting in the
machine characterization. MLC area calculations have sufficient internal precision to achieve the output
resolution required by the characterization regardless of the computational methods employed. MLC leaf
positions are stored in the MOSAIQ database in units of 0.01 cm and displayed in MOSAIQ to a precision
of 0.01 cm.
The precision of measurement or margin of error of MLC Fit is in addition to the precision or margin of
error throughout the entire system of use, including the MLC itself. Refer to your MLC user’s manual for
information regarding the accuracy of your particular equipment. Some examples of additional factors
affecting overall precision of leaf fit to shape are the accuracy of user digitization (if used), user variation in
leaf position dragging (if used), fit to shape variation due to leaf shape, and so on.
ViewStation
The measurements of the ViewStation ruler are calculated based on the pixel size (mm/pixel) of the
underlying image. The units of measurement for the ViewStation ruler length are displayed in centimeters
(cm), with a precision or margin of error of one-tenth of a millimeter (.1 mm). Precision of measurements
are directly proportional to the applied zoom factor (for example, at 200% zoom, a measurement twice as
fine can be achieved at 100% zoom).
Copyright 2010, Elekta Impac Software 295
LUGMSQ0002/4.0/23-Sep-2010