ESTRO 2023 - Abstract Book

S1377

Digital Posters

ESTRO 2023

Conclusion We implemented an image preprocessing pipeline with the aim of facilitating the learning of an automatic segmentation tool without compromising the image visualization for the clinicians. Based on this preliminary work, the N4ITK and N4ITK_AHE application on 0.35T MRIs results mainly in either an improvement or no change of both overall IQ and OARs visualization in clinical practice. Results are also supported by quantitative metrics, showing a decrease in signal dispersion. Future work will investigate the effect of applying this pipeline on the performance of a dedicated AI-based auto segmentation algorithm.

PO-1673 Accuracy of electron density in a novel high-performance CBCT imaging system

T. Zhao 1 , A. Price 1 , N. Knutson 1 , E. Laugeman 1 , Y. Hao 1 , L. Henke 1 , P. Samson 1

1 Washington University in St. Louis, Radiation Oncology, St. Louis, USA

Purpose or Objective In this study, we reported the accuracy of the electron density for a novel, high-performance cone beam computed tomography (CBCT) imaging system . Materials and Methods A novel, high-performance CBCT imaging system was designed and installed by the vendor on an o-ring linear accelerator. The imaging panel was reengineered with the size of the panel doubled to 43cm x 86cm. The scintillator layer was changed to CsI of 700 µm in thickness in order to improve the detection sensitivity and imaging resolution. The clinical goal of the new imaging system is to improve image quality to facilitate improved treatment setup with better tumor localization, and to provide a high quality CBCT simulation that can be used for treatment planning/replanning and dose calculation. To verify the accuracy of the electron density of the new CBCT imaging system, Hounsfield units (HU) were measured with a CBCT Electron Density Phantom (SunNuclear, Model 062MA). The phantom is 26.5 cm in the longitudinal direction with optional extension plates to allow adequate scatter in a cone beam geometry. The compositions of the interchangeable inserts were supplied by the vendor. A stoichiometric CT calibration was employed to generate the HU-electron density curve for the two tube voltages commissioned for simulation. Verification was performed by comparing the electron densities measured on a Gammex phantom to the values provided by the vendor. Solid water plates were added to both ends of the Gammex phantom to allow adequate scattering. The measurements were repeated for various clinical protocols with exposures from 50 mAs to 800 mAs. A plan created on a study patient’s helical simulation CT was compared to its