175. A preliminary study on the correlation of modulation plan parameters with dosimetric accuracy of VMAT treatment plans performed in two centres with different linear accelerators and treatment planning systems

Purpose: The purpose of this study is to compare the performance of three 3-dimensional radiotherapy treatment planning systems (TPS) in terms of user-friendliness and dosimetric accuracy.Methods: A scale type questionnaire, which contained 129 items under 13 aspects of the TPS, was used to collect opinions from users from three different institutions with regards to the user-friendliness. The assessment of dosimetric accuracy was carried out by comparing the measured dose values with those calculated by the TPS under 18 different irradiating and phantom set-up conditions.Results: Eleven respondents completed the questionnaires for each TPS. Our study indicated that the Varian CadPlan was outstanding in the plotting and network transfer of treatment plans to other workstations, the CMS Focus performed better in the construction of treatment aids, and the ADAC Pinnacle in the outlining, modification of field parameters, control of graphics and normalization of dose. In terms of dosimetric accuracy, the measured and the calculated data for the 3 TPSs showed fairly good agreement. Except for the field with median block, in which the Focus presented with the best result, the differences in other irradiating conditions were not obvious with the percentage dose deviations within ±3%.Conclusion: In conclusion, for the 3 TPSs evaluated, each had its own strengths and weaknesses, and no TPS was superior in all test conditions.

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Implementation of carbon fibre treatment couches in the XiO® and Monaco® Treatment Planning Systems

Polish Journal of Medical Physics and Engineering ◽

10.2478/pjmpe-2020-0025 ◽

2020 ◽

Vol 26 (4) ◽

pp. 211-215

Author(s):

Christoffel Jacobus Van Reenen ◽

Christoph Jan Trauernicht

Keyword(s):

Carbon Fibre ◽

Treatment Planning ◽

Conformal Radiotherapy ◽

Ct Scanner ◽

Planning Systems ◽

Linear Accelerators ◽

Treatment Planning Systems ◽

Fibre Treatment ◽

Treatment Plans ◽

The Individual

AbstractPurpose: Carbon fibre treatment couches on linear accelerators provide a strong, rigid framework for patient support. Patient safety is a priority, therefore the dosimetric properties of treatment couches need to be accurately incorporated in treatment plans, to minimize differences between planned and delivered dose. This study aims to determine the attenuation effect of treatment couches for 3-D Conformal Radiotherapy (3-D CRT) and to validate the implementation thereof in the XiO and Monaco treatment planning systems (TPS).Material and methods: Attenuation measurements were performed on the ELEKTA Connexion couches of the ELEKTA Precise and Synergy-Agility linear accelerators. Measurements were made at 10° intervals in RMI-457 Solid water (30 cm x 30 cm x 30 cm) using a PTW Farmer-type ionization chamber (TW30013) positioned at the accelerator’s isocentre. The percentage attenuation was calculated as the ratio of the electrometer readings for parallel-opposed fields. The Computed Tomography (CT) data sets of the set-ups were obtained on a Philips Big Bore 16-slice CT scanner and exported to the TPS. The individual couch structures were delineated and electron density (ED) values were assigned using the commissioned CT-to-ED curve. Test treatment plans were generated with 100MU per field at 10° gantry intervals.Results: The percentage attenuation was determined to be within 2% and 3% for beams perpendicular to the couch surface for XiO and Monaco, respectively. The maximum attenuation was observed for oblique fields which was significantly higher than the manufacturer specified values. TPS validation showed an agreement to 1% for XiO and Monaco. At extreme oblique angles, both planning systems overestimated this effect up to a maximum of 4%.Conclusions: Couch attenuation differs significantly with gantry angle and beam energy. As a result, the treatment couch models should be included in all treatment planning calculations.

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