MOSAIQ User's Guide - UCSF Radiation Oncology

MOSAIQ User’s Guide
Using MLC Fit
The MLC Fit feature provides you with the ability to create, view, and edit geometric
information that is ultimately used to generate treatment field shapes. To do so, MLC Fit
enables you to digitize treatment field shapes, derive Multi-leaf Collimator (MLC) leaf plans
from these digitized shapes, and modify those shapes within MOSAIQ.
Using MLC Fit
Selecting the Fit option instructs the MLC Fit feature to perform the following operations:
1. Extract the leaf sizes and position limits from the Machine Characterization record for
the specified (selected) machine.
2. Automatically perform a Fit, fitting the leaves to the digitized shape using the constraint
specified in the Fit Method group of the Beam’s Eye View window.
If the Fit Method specified is Intrusive, then the leaves are positioned so that the
leading edge of each leaf is completely within the shape. Additionally, the leaf
position is rounded to the resolution specified in the Machine Characterization
record.
If the Fit Method is Centered, then the leaves are positioned so that the center of
each leaf’s leading edge crosses an edge of the shape. The leaf position is rounded to
the resolution specified in the Machine Characterization record.
If the Fit Method is Non-Intrusive, then the leaves are positioned so that no part of a
leaf intrudes within the shape. The leaf position is rounded to the resolution specified
in the Machine Characterization record.
If there is no leaf position that satisfies the Fit Method constraint, then the leaf is
driven to butt up against its opposing leaf.
If a fitted leaf position exceeds its positional limit, then the leaf is set to the
positional limit.
The position of opposing, touching leaf pairs is adjusted in order to prevent
opposing adjacent leaves from extending beyond each other.
The Y-jaws are set to the position determined by the recommended jaw function
specified in the Machine Characterization record. If a recommended jaw function is
not specified in the record, then, for all fit methods, the Y-jaws are driven to their
most extended position so long as they do not intrude into the shape.
The X-jaws are set to the position determined by the recommended jaw function
specified in the Machine Characterization record. If a recommended jaw function is
not specified in the record, then, for all fit methods, the X-jaws are driven to their
most extended position providing they do not extend past the end of any leaf.
If a fitted jaw position exceeds its positional limit, then the jaw is set to the
positional limit.
The Fit is performed at the collimator angle specified in the Angle field of the
Collimator group in the Beam’s Eye View window.
130 Copyright 2010, Elekta Impac Software
LUGMSQ0002/4.0/23-Sep-2010