S2079
Physics - Image acquisition and processing
ESTRO 2026
Digital Poster 3763 Metal artifact reduction for 3T MRI-only prostate radiotherapy with hip prostheses: target definition, synthetic CT and fiducial marker identification Mizgin Coskun 1 , J Stefan Petersson 1,2 , Sacha af Wetterstedt 1,2 , Patrik Brynolfsson 2 , Christian Jamtheim Gustafsson 1,2 , Adalsteinn Gunnlaugsson 3 , Lars E Olsson 1,2 , Carl Siversson 1,4 1 Medical Radiation Physics, Department of Translational Medicine, Lund University, Malmö, Sweden. 2 Radiation Physics, Department of Hematology, Oncology, and Radiation Physics, Skåne University Hospital, Lund, Sweden. 3 Division of Oncology, Department of Clinical Sciences Lund, Skåne University Hospital, Lund University, Lund, Sweden. 4 MR Radiation Oncology, GE HealthCare, Helsingborg, Sweden Purpose/Objective MRI-only prostate radiotherapy planning offers superior soft-tissue contrast and eliminates uncertainties from multi-modality registrations. However, in patients with metallic implants, MRI-only workflows remain challenging since target delineation, synthetic CT (sCT) generation, and fiducial marker identification ideally need to be performed on the same MR image. Metal artifact reduction sequences (MARS) mitigate metal distortions [1] but often suppress the signal void of gold seed fiducial markers, complicating their detection. This study presents a proof-of-concept MRI-only workflow for prostate cancer patients with hip prostheses at 3T, employing MARS MAVRIC-SL for target/organ-at-risk (OAR) delineation and sCT generation, and introduces a method for fiducial marker identification. Material/Methods Five prostate cancer patients were included (three unilateral, two bilateral hip prostheses). All underwent CT and MRI for radiotherapy planning, including 3T MAVRIC-SL MRI (GE Healthcare). The analysis was retrospectively performed without influencing clinical treatment. In MAVRIC-SL images, intraprostatic markers used for patient positioning were not directly visible due to signal void artifact reduction. However, reconstructing MAVRIC-SL raw data into spectral bin images enabled manual identification of marker signal voids (Fig. 1). sCTs were generated from the MAVRIC-SL images using MRI Planner (Spectronic Medical AB). Ingoing radiation through metal implants was avoided by applying an avoidance sector. Hip prostheses signal voids visible in MAVRIC-SL images were delineated and used to define an avoidance sector (AS2). For comparison, conventional avoidance sectors derived
Conclusion: PCD-CT was successfully integrated in our radiotherapy workflow. Dose calculation can be successfully performed on either EI or spectral images. Mass densities directly reconstructed from spectral post-processing are highly accurate and provide an excellent candidate for dose reconstruction, especially for targets encompassing bones or for patients with contrast. References: [1] ImPACT (UK’s national CT evaluation centre) Information Leaflet 1: CT Scanner Acceptance Testing, www.impactscan.org[2] D. Kearns, M. McJury, Commissioning a new CT simulator I: CT simulator hardware, Journal of Radiotherapy in Practice (2007), 6, 153-162, 2007 Cambridge University Press, doi: 10.1017/S1460396907006097[3] AAPM-TG66 report, Quality assurance for computed-tomography simulators and the computed tomography simulation process, DOI: 10.1118/1.1609271 Keywords: photon-counting detector, CT commissioning
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