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Commissioning of Brainlab IPlan On TrueBeam STx for 6MV with High-Definition MLCs

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C Yu

C Yu*, G Cui , Univ Southern California, Los Angeles, CA


SU-I-GPD-T-612 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: We present our experience with commissioning and validation of Brainlab iPlan on TrueBeam STx for 6MV with flattening filter (WFF) and High-definition MLCs.

Methods: Beam data were acquired using IBA’s Blue Phantom following the protocols provided by Brainlab for TrueBeam STx with HDMLCs, which include the percent depth dose, scatter factors or output factors for pre-defined 10 pair of MLC leaf and jaw settings, respectively, and both diagonal radial and transversal profiles at specific jaw and MLC leaf settings. Solid water phantom stacked on the top of each other with Gafchromic films between the slabs at depths of 5, 10 and 16cm were scanned. A plan of a single vertical beam was developed and delivered for a square field size of 5, 10, and 15mm, respectively. An anthropomorphic head phantom from IROC Houston containing a 1.9cm diameter spherical target with two TLDs for absolute dose and two orthogonal Gafchromic films for dose profiles and distribution was imaged and irradiated with a 7 arcs plan.

Results: Scatter factors are 0.562, 0.728, 0.800, 0.836, 0.867, 0.921, 0.965, for 5x5, 10x10, 20x20, 30x30, 40x40, 60x60, 80x80 HDMLCs, respectively. The percent depth dose and both radial and transversal profiles are in excellent agreement with Brainlab’s expected values for the specific system configuration. Validation measurements from solid water phantom showed an agreement of absolute dose ranged from 2% to 4% between plan and the delivered, and field sizes within 0.3mm to 1.0mm. The head phantom results showed an average TLD dose ratio of measured to institution of 0.98 and film Gamma index of 96% and 98% for coronal and sagittal planes, respectively.

Conclusion: The commissioning data showed good consistency with other users collected by Brainlab. Validation measurements from both self and external evaluations provide valuable insights and reliable assessments on the new modality.

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