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Empirical estimation of beam-on time for prostate cancer patients treated on Tomotherapy
Małgorzata Skórska1, Tomasz Piotrowski2
1Department of Medical Physics, Greater Poland Cancer Centre, Poznan, Poland.
Background And Aim:
This study proposed a method to estimate the beam-on time for prostate cancer patients treated on Tomotherapy when FW (field width), PF (pitch factor), modulation factor (MF) and treatment length (TL) were given.
Material And Methods:
THE STUDY WAS DIVIDED INTO TWO PARTS: building and verifying the model. To build a model, 160 treatment plans were created for 10 patients. The plans differed in combination of FW, PF and MF. For all plans a graph of beam-on time as a function of TL was created and a linear trend function was fitted. Equation for each trend line was determined and used in a correlation model. Finally, 62 plans verified the treatment time computation model - the real execution time was compared with our estimation and irradiation time calculated based on the equation provided by the manufacturer.
Results:
A linear trend function was drawn and the coefficient of determination R (2) and the Pearson correlation coefficient r were calculated for each of the 8 trend lines corresponding to the adequate treatment plan. An equation to correct the model was determined to estimate more accurately the beam-on time for different MFs. From 62 verification treatment plans, only 5 disagreed by more than 60 s with the real time from the HT software. Whereas, for the equation provided by the manufacturer the discrepancy was observed in 16 cases.
Conclusions:
Our study showed that the model can well predict the treatment time for a given TL, MF, FW and it can be used in clinical practice.
