A strategy for selecting measurement points in the determination of depth-dose curves and dose profiles

Knowledge of the central-axis depth-dose curve and the dose profiles of a r adiotherapy treatment unit are essential for setting up an external system for planning radiotherapy treatment. Estimates for these are usually found with the aid of a measurement probe with which the dose is measured at equa lly spaced measurement points. In this paper a strategy for selecting the m easurement points for determination of the depth-dose curve and dose profil e is proposed. The performance of the method is evaluated with real 6 MV ph oton depth-dose data and real 18 MV dose-profile data. The studies show tha t the proposed method allows the estimation of the depth-dose curve with ad equate accuracy typically from 10-14 measurements at this energy instead of approximately 120 measurements, which is a common number of measurements. Thus the measurements protocol decreases about tenfold the number of measur ements required. The studies also show that a fivefold decrease can be achi eved in the dose-profile measurement.