ESTRO 2024 - Abstract Book

S4808

Physics - Quality assurance and auditing

ESTRO 2024

Conclusion:

High GPR among the plans on both beam qualities and MLC models indicate strong agreement between planned and measured doses. This shows the choice of beam quality or MLC model does not affect the physical dose agreement in a lung SBRT VMAT plan. The plan complexity metrics show that there are certainly differences in the plan characteristics between the two MLC models resulting in slightly more complex plans from Millennium 120 MLC. Lastly, 10FFF and 6FFF plans were found to perform equally in terms of dosimetric indices, plan complexity and plan deliverability. With these results, our institution decided to employ 10FFF rather than 6FFF for Lung SBRT VMAT as it can deliver treatment more efficiently with nearly double the dose rate which reduces the treatment delivery time. This is especially beneficial for patient with motion managements such as breath-hold and abdominal compression plate.

Keywords: Lung SBRT, gamma passing rate, acceptance

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Digital Poster

Commissioning of Prosoma Core for SRS treatments.

Anna Bangiri 1,2 , Jonathan D Allred 1 , Jonathan CR Stoddart 3 , Man Ho Calvin Lee 1

1 Nottingham University Hospitals NHS Trust, Radiotherapy Physics, Nottingham, United Kingdom. 2 University of Nottingham, School of Medicine, Nottingham, United Kingdom. 3 Nottingham University Hospitals NHS Trust, Radiotherapy Physics, Nottingham, USA

Purpose/Objective:

The aim of this project was to test Prosoma Core and our Patient Specific Quality Assurance (PSQA) process for Stereotactic Radiosurgery (SRS) patients by introducing known errors to clinical plans.

Material/Methods:

At Nottingham University Hospitals NHS Trust we treat on average 3 to 4 SRS patients per week. The PSQA associated with each patient is time consuming and resource heavy. EBT-XD films are used within the STEEV phantom to capture a 2D dose distribution for the smallest PTV of each patient plan. The measured dose distribution is compared to the planned using global gamma analysis and a 95% pass rate (5%/2mm, 20% threshold). Prosoma Core uses a 3D Monte Carlo algorithm1, allowing the recalculation of complex treatment plans, and also has a log-file analysis module. During commissioning, two clinical plans were created using Monaco. One plan, named Original, had two PTVs that were treated off axis, with 22Gy/1#. The second plan, named PTV3, had one PTV that was treated on axis with 22Gy/1#. QA plans were created for both plans, and PTV1 and PTV3 would be tested during PSQA.