Universität zu Köln

Heidorn, Sarah-Charlotta, Kilby, Warren and Fuerweger, Christoph (2018). Novel Monte Carlo dose calculation algorithm for robotic radiosurgery with multi leaf collimator: Dosimetric evaluation. Phys. Medica, 55. S. 25 - 33. OXFORD: ELSEVIER SCI LTD. ISSN 1724-191X

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Abstract

Purpose: At introduction in 2014, dose calculation for the first MLC on a robotic SRS/SBRT platform was limited to a correction-based Finite-Size Pencil Beam (FSPB) algorithm. We report on the dosimetric accuracy of a novel Monte Carlo (MC) dose calculation algorithm for this MLC, included in the Precision (TM) treatment planning system. Methods: A phantom was built of one slab (5.0 cm) of lung-equivalent material (0.09...0.29 g/cc) enclosed by 3.5 cm (above) and 5 cm (below) slabs of solid water (1.045 g/cc). This was irradiated using rectangular (15.4 x 15.4 mm(2) to 53.8 x 53.7 mm(2)) and two irregular MLC-fields. Radiochromic film (EBT3) was positioned perpendicular to the slabs and parallel to the beam. Calculated dose distributions were compared to film measurements using line scans and 2D gamma analysis. Results: Measured and MC calculated percent depth dose curves showed a characteristic dose drop within the low-density region, which was not correctly reproduced by FSPB. Superior average gamma pass rates (2%/1 mm) were found for MC (91.2 +/- 1.5%) compared to FSPB (55.4 +/- 2.7%). However, MC calculations exhibited localized anomalies at mass density transitions around 0.15 g/cc, which were traced to a simplification in electron transport. Absence of these anomalies was confirmed in a modified build of the MC engine, which increased gamma pass rates to 96.6 +/- 1.2%. Conclusions: The novel MC algorithm greatly improves dosimetric accuracy in heterogeneous tissue, potentially expanding the clinical use of robotic radiosurgery with MLC. In-depth, independent validation is paramount to identify and reduce the residual uncertainties in any software solution.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Heidorn, Sarah-Charlotta UNSPECIFIED UNSPECIFIED UNSPECIFIED Kilby, Warren UNSPECIFIED UNSPECIFIED UNSPECIFIED Fuerweger, Christoph UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-167632
DOI:	10.1016/j.ejmp.2018.10.011
Journal or Publication Title:	Phys. Medica
Volume:	55
Page Range:	S. 25 - 33
Date:	2018
Publisher:	ELSEVIER SCI LTD
Place of Publication:	OXFORD
ISSN:	1724-191X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language CLINICAL IMPLEMENTATION; PHOTON; BEAM; VERIFICATION; CYBERKNIFE; PERFORMANCE; VALIDATION; FIELDS Multiple languages Radiology, Nuclear Medicine & Medical Imaging Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/16763