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Session Item

Friday
May 07
14:15 - 15:30
21st century brachytherapy: is it available, affordable and relevant?
There are several reports of declining use of brachytherapy worldwide despite its well-documented advantages. Brachytherapy is often perceived to be resource-intensive and expensive and its role in the era of increasingly sophisticated external beam radiotherapy techniques has been questioned. This session discusses some of the issues that influence availability and utilisation of brachytherapy. Topics include current status of cervix cancer brachytherapy availability worldwide and global initiatives to improve access, socio-economic factors impacting brachytherapy treatment trends in the United States, a literature review of time activity based costing studies of brachytherapy, and brachytherapy training and interest amongst European radiation oncology residents.
Symposium
00:00 - 00:00
Validation of a MC software for the QA of patients treated with modulated intensity photon beams
PO-1386

Abstract

Validation of a MC software for the QA of patients treated with modulated intensity photon beams
Authors: PIFFER|, Stefano(1,2)*[stefano.piffer.3@gmail.com];Napora|, Maja(1);Toci|, Thomas(1);Casati|, Marta(3);Marrazzo|, Livia(3);Arilli|, Chiara(3);Calusi|, Silvia(3);Desideri|, Isacco(1);Simontacchi|, Gabriele(4);Pallotta|, Stefania(1,2,3);Alber|, Markus (5,6);Talamonti|, Cinzia(1,3);
(1)Università degli studi di Firenze, Dipartimento di Scienze Biomediche- Sperimentali e Cliniche "Mario Serio", Firenze, Italy;(2)Istituto Nazionale di Fisica Nucleare INFN, Sede di Firenze, Firenze, Italy;(3)Azienda Ospedaliera Universitaria Careggi, Medical Physics, Firenze, Italy;(4)Azienda Ospedaliera Universitaria Careggi, Radiation Oncology, Firenze, Italy;(5)ScientificRT, GmbH, Munich, Germany;(6)Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany;
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Purpose or Objective

Nowadays patient QA is very important in the RT workflow, especially for patients with highly conformed treatment plans, and it is usually performed prior to patient treatment. Patient QA is fairly time consuming and takes up a lot of time-machine, stealing it from patients'' treatments. Moreover, physicist’s time is a limited resource.
The innovation proposed within this work is to introduce a new MC software (SciMoCa) in the RT workflow, which can be used as a fast-secondary dose check and an independent plan QA evaluating tool. This method allows to verify only those treatments that do not pass the minimum acceptance criteria.
The aim of the study is to evaluate SciMoCa, testing its performances in term of accuracy, repeatability and calculation time.

Material and Methods

SciMoCa was benchmarked against TPS Monaco (Elekta) and Pinnacle (Philips) in VMAT techniques, they are based on MC and CCC dose calculation algorithm respectively. All three software were commissioned for the same 6MV Elekta accelerator using the same measurement set.
Fifty patients of six clinical classes (CNS, H&N, breast, lung, prostate and bone metastasis) were randomly selected from the clinical database and computed with all algorithms using the same calculation parameters. Dose accuracy was studied by assessing the isocenter point dose differences while dose distributions were evaluated with the statistics of 2D-γ analysis (3%3mm-TH10%). Software performances were also verified at the accelerator with measurements relying on ArcCHECK to evaluate the dose differences in a homogeneous phantom. The comparison was performed with the same setting as before.

Results

Results are shown in Table1. On average, the percentage point dose differences between Monaco and Pinnacle compared to SciMoCa are -1.8±1.8% and -0.5±1.1%, respectively; while TPSs to ionization chamber measurements are -0.6±1.7% and 0.4±1.4%, for Monaco and Pinnacle respectively.
Comparing the SciMoCa dose distributions to those of Monaco and Pinnacle, the average passing rates of the γ analysis (absolute term), are 94.5±5.4% and 96.5±3.5%, respectively. Comparing TPSs to ArcCHECK measurements, on average the γ analysis (absolute term) is 94.0±3.3% and 95.3±2.5% for Monaco and Pinnacle respectively.
The repeatability of the simulated dose is very high, within few ‰. Considering a standard PC (CPU: Intel Core i7-6500U, 2.59GHz; RAM:16GB) the calculation time is in the order of 30 minutes. It decreases as dose computation uncertainty increases and the same happens increasing dose grid resolution.

Conclusion

An excellent agreement was found between SciMoCa, TPSs (both MC and CCC dose calculation algorithm) and measurements. This innovation software could be used as a secondary dose check verification system and it could become a fast and positive chance for the patient QA, saving a lot of time both for physics and machine. It could also be useful in adaptive RT for checking the impact of the approved RT-Plan on the daily patient anatomy modifications.