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Tuning Dose Curve in Tomotherapy

U Reyes Serrano*,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: A simple protocol for the elaboration of a tuning Dose Curve in tomotherapy is shown. The tuning dose should be done as a function of dose reported by the planning system vs the dose measured with the ionization chamber.


Methods: the Tomotherapy HDA, two A1SL ionization chamber with their respective electrometer, the tomophantom with different HU inserts, solid water plates and the tomotherapy planning system have been used. This work is structured in 2 sections: the first one is the protocol to generate the Tuning Dose Curve and finally the protocol to verify that the Tuning Dose has worked.


Results: With 5 measured dose values, the linear adjustment was made, and the tuning equation was obtained. It was observed that by modifying the internal ionization chamber 1 of the tomotherapy in 266 counts, it is possible to adjust the difference between the dose reported by the planning system and the dose measured with the ionization chamber by 1%. With the information obtained from the Tuning Curve Dose, 400 counts were increased to the internal ionization chamber 1 and the results after making this adjustment were: for the 3 treatment plans the major difference due to -0.4%. The dose rate gave a difference of -0.1% and the beam quality was 59.73%.


Conclusion: The way to tune the dose between planned and measured is a simple process, but we must review it periodically. The information obtained from the Tuning Dose Curve should be applied to tune de doses mainly when a change of Linac in tomotherapy is made. With this simple protocol, it is possible to adjust the dose of the planning system versus the dose delivered with differences less than 0.5%.

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