ESTRO 2024 - Abstract Book

S5920

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

2177

Digital Poster

Impact Metal Implants on Radiotherapy Planning: HU Value Variations with 80kV and 140kV Tube Voltage

Sook Yang 1 , Euncheol Choi 2 , Byungyong Kim 2 , Sang Jun Byun 2 , Young Kee Oh 2 , Ye Won Kim 2 , Myeongsoo Kim 2

1 R&D center, CusMedi co., Ltd, Suwon, Korea, Republic of. 2 Department of Radiation Oncology, Keimyung University Dongsan Hospital, Daegu, Korea, Republic of

Purpose/Objective:

With the increasing utilization of metal implants, especially 3D-printed craniofacial implants in the medical field for reconstructive and cosmetic surgeries, there is a growing need to assess their impact on radiotherapy planning for craniofacial tumors. Metal implants, when positioned in the skull's basal region, can potentially influence the delineation of critical structures and dose calculations due to discrepancies in CT Hounsfield Unit (HU) values. Metal materials introduce artifacts in CT images, leading to inaccuracies in HU values for both the implant and surrounding tissues. This study aims to evaluate the influence of X-ray tube voltage on variations in HU values and to explore how these variations affect radiotherapy planning, with a specific focus on 3D-printed implants.

Material/Methods:

Nine 1cm cubes were arranged in a row in the central region of a solid water phantom with a thickness of 11cm. Three different materials were subjected to computerized tomography (CT) scans (SOMATOM Definition AS, Erlangen, Germany) with scanning conducted at 80kV and 140kV. Separate images were reconstructed for each using conventional Hounsfield Units (HU) and Extended HU values. The Extended HU reconstruction was performed with the simultaneous application of the iMAR algorithm. All reconstructed CT images were subsequently employed in the development of a radiotherapy treatment plan using the Eclipse 15.7 version (Palo Alto, California, USA) based radiotherapy planning system. The treatment involved delivering a single-beam field at a gantry angle of 0 degrees. The central cube among the nine cubes was designated as the isocenter. A reference point was marked 3.5 cm posterior to the isocenter, and a dose plan was created to deliver 200cGy/one fractions using a 6MV energy beam. The linear accelerator selected for this purpose was the Vital linear accelerator. Dose measurements were carried out at the reference point using the IBA Dosimetry Matrixx FFF system (IBA Dosimetry, Louvain-la-Neuve, Belgium).