ESTRO 2024 - Abstract Book

S4779

Physics - Quality assurance and auditing

ESTRO 2024

Planning protocol compliance in the individual case reviews was high, with 86% showing acceptable variations. This suggests it may be possible to further streamline the process, replacing the labour-intensive prospective RT QA with retrospective review.

Variation from the trial protocol does not mean a plan is clinically unacceptable, however definition of such variations are required to ensure delivery of high quality, protocol-compliant RT to trial participants.

Streamlining through previous H&N trial participation has been shown to be very effective and should be maintained for future studies. Acceptability rates for prospective review were higher in streamlined centres than for those benchmarked for PATHOS, demonstrating ongoing trial participation is key to maintaining high radiotherapy standards.

Keywords: clinical trials, quality assurance

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Digital Poster

In vivo dosimetry of total body irradiation patients: a 10 years retrospective analysis

Stefano Carminati 1,2 , Sara Trivellato 2 , Chiara Ingraito 1,2 , Valeria E Tremolada 2 , Chiara Julita 3 , Stefano Arcangeli 3,4 , Elena De Ponti 2 1 University of Milan, Department of Physics, Milan, Italy. 2 IRCCS San Gerardo dei Tintori, Medical Physics Department, Monza, Italy. 3 IRCCS San Gerardo dei Tintori, Department of Radiation Oncology, Monza, Italy. 4 University of Milan Bicocca, School of Medicine and Surgery, Milan, Italy

Purpose/Objective:

Myeloablative total body irradiation (TBI) is a well-established practice used in the conditioning of hematopoietic stem cell transplantation in patients with hematological diseases. In 2012, an extended-distance technique was implemented using a 15 MV LINAC beam with complete CT planning at the TPS. In-vivo dosimetry (IVD) has been done using diodes or thermoluminescent dosimeters to monitor variation from the expected dose. Lead compensating filters together with PMMA and water bolus have been used to shield organs at risk (lungs) and to increase dose homogeneity, respectively. This study aims to review in-vivo dose measurements over 10 years of treatments assessing the technique’s robustness, accuracy, and efficiency.

Material/Methods:

In the implemented technique, a 2-lateral opposite fields plan (with source-to-midline distance ranging from 3.65 m to 3.90 m) is calculated with a collapsed-cone algorithm (Oncentra MasterPlan, Nulcetron B.V., Netherland) to estimate the shape and thickness of lung compensators and monitor units (MU) to give 100% of the prescription dose to the patient midline. The patient is positioned supine and the correct alignment is checked with lasers and markers