Room: AAPM ePoster Library
To reduce the number of overrides over a treatment course due to patient’s position, a predicted treatment table position from simulation CT dataset was developed.
At the patient’s initial visit for radiotherapy, the table coordinates for isocenter position is captured and used for the remainder of the treatment course. These values are used as the target position by defining a user-specified range for subsequent fractions. When the position falls outside of this range, therapists must acknowledge and override values to be able to commence treatment.
To predict the table coordinate, a marker wire was placed on the breast board to create a landmark that could be used to establish vertical, lateral, and longitudinal coordinates. Using the current clinical range (Vertical ±1.5 cm, Longitudinal ±3.0 cm, Lateral ±3.0 cm), projected overrides were analyzed using both predicted table coordinates and the first day treatment table coordinates.
Sixty-nine isocenters were analyzed covering a total of 971 treatment fractions. With the use of the predicted table coordinates, the number of projected treatment overrides reduces from 25 to 13 (48% reduction). By reducing the longitudinal and lateral range to ±2.5 cm, it was found that similar amount of overrides (25) would have taken place as if the first day coordinates are used.
By using a table value predicted from the simulation CT, the number of overrides can be reduced or a similar amount found using a narrower range. A reduction can relieve therapy staff of override fatigue so to more alertly identify positional errors. Newer linear accelerators allow the therapist to translate the treatment couch to the given position. By starting at the predicted table coordinates, this should decrease setup time and lead to more consistent patient positioning.
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