ESTRO 2024 - Abstract Book

S4768

Physics - Quality assurance and auditing

ESTRO 2024

The image quality control allows our team to monitor most parameters over time and make adjustments in case of unacceptable deviations. The variability in SNR makes it difficult to use this measure. For SRS practices, the presence of distortions is the most critical aspect of the MRI. Our results show that, within a 32cm diameter sphere centred at isocentre and with the distortion correction algorithm turned on, the distortions of our 3T MRI are on average smaller than 1mm. In conclusion, we can safely use the 3T MRI for our brain SRS patients and keep our PTV margins at 2mm for LINAC patients and at 1mm for Cyberknife patients.

Keywords: MRI QC, Distorsions, ACR

References:

1.Netherlands Commission on Radiation Dosimetry (2023), Quality Assurance of MRI for Radiotherapy. Report 36. https://doi.org/10.25030/ncs-036

2. Glide-Hurst, C.K., Paulson, E.S., McGee, K., Tyagi, N., Hu, Y., Balter, J. and Bayouth, J. (2021), Task group 284 report: magnetic resonance imaging simulation in radiotherapy: considerations for clinical implementation, optimization, and quality assurance. Med. Phys., 48: e636-e670. https://doi.org/10.1002/mp.14695

711

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Analysis of dose-volume histogram using Fourier transformation

Indra J Das 1,2 , ahtesham U Khan 1

1 Northwestern Memorial Hospital, Radiation Oncology, Chicago, USA. 2 Northwestern University Feinberg School of Medicine, Radiation Oncology, Chicago, USA

Purpose/Objective:

Inverse planned (intensity modulated radiation therapy and volumetric modulated arc therapy, IMRT/VMAT) dose distributions are derived from inverse planning process providing a byzantine pattern of multileaf collimators from multiple angles that provides the desired dose distribution to a target volume and spares organs at risk (OAR) (1). However, there is no talisman that can provide a measure of optimum dose distribution that can measure the superiority indices of dose-volume histogram (DVH). The parameters, tumor control probability TCP and normal tissue complication probability (NTCP) were developed 30 years ago (2) to provide guidance but their use has not proliferated due to poor understanding of the biological indices and its direct correlation to outcome. In current practices, conformity index (CI), homogeneity index (HI) and gradient index (GI) has been suggested as indicated by ICRU-83 and ICRU 91 (3, 4). We have proposed a unique method using Fourier transformation of the DVH to derive a merit of quality that can be successfully used in a clinical scenario.

Material/Methods: