M.M. GHANNAM*, H.M. DIAB**, MARIAM M. ALHASHIM***, B. MOFTAH****

*Physics Department, Faculty of Science, “King Saud” University, Riyadh, KSA; permanent address: Biophysics Department, Faculty of Science, Cairo University, Giza, Egypt
**Physics Department, Faculty of Science, Northen Border University, Arar, KSA; permanent address: Radiation Dosimetry Laboratory, National Institute of Standards, Giza, Egypt
*** Medical Physics Department, “King Fahd” Scientific Hospital, Riyadh, KSA

Abstract. In this work, an extensive set of measured data was developed to verify the accuracy of a photon dose calculation algorithm for the Eclipse treatment planning system (TPS). Test cases included square fields, rectangular fields, fields having different source-to-surface distances, wedged fields, irregular fields, obliquely incident fields, asymmetrically collimated fields with wedges, multileaf collimator-shaped fields. The data set was used to validate the photon dose calculation algorithm in the Eclipse TPS. The monitor unit tests revealed that the 6 MV open square fields, rectangular fields, wedged fields, oblique incidence, source-to surface distance variation, mantle field, half beam block, and oblique incidence with wedge test cases did not meet the TG-53 criteria all the time. The results can be used also to establish standards of acceptance for the demonstration of the correct working of the TPS in regular QA-checks. The algorithm must accurately calculate dose distributions for a variety of clinical beam configurations. It was concluded that the generally stated goal of accuracy in dose delivery of within 5% cannot be met in all situations using this beam model in the Eclipse TPS. Although Eclipse is more accurate than measured reading for total scatter factor in water phantom, it is recommended to improve the accuracy of the treatment planning process, e.g. with the incorporation of the Monte Carlo calculation method to the latest version of Eclipse.
Key words: photon dose calculations, accuracy, Eclipse, radiotherapy.

Corresponding author’s e-mail: mmghanam@ksu.edu.sa

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