MR-ONLY as a reference image in verifying positioning in Radiotherapy

• Autor(a) principal: Marques, João
• Data de Publicação: 2022
• Outros Autores: Caetano, Marco, Stroom, Joep, Greco, Carlo
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: https://doi.org/10.46885/roentgen.v3i2.87
• topic: Radiotherapy; Registration; MR-Only; Synthetic CT; Radioterapia; Registo; MR-Only; TC sintética

Introduction: The planning systems use the information of the electronic densities, needed for the calculation of the dose from the CT. A recent trend is the use of MR as the only modality, using the MR image to create a synthetic CT. A workflow in which all pre-treatment steps are performed at the MR is favorable. The objective of this study is to validate the MR-Only technique as the reference image in the verification of positioning in Radiotherapy. Methods: 13 patients with brain tumor and 15 patients with rectal tumor followed at the Radiotherapy unit of the Champalimaud Clinical Center, from October 2019 to June 2020, were included. Based on the automatic registration of 80 CBCT, the deviations between images of planning CT and synthetic CT (MR-Only) were compared. Results: In the registration of the images in the rectum, the variation that was obtained was less than 1,4mm longitudinal, 1mm laterally and vertically. The variation verified in the translations was -0,2±0,3mm lateral, -0,3±0,4mm vertical and -0,4±0,7mm longitudinal. Regarding rotations were lower than 0,4º, with the variation verified 0,0±0,2º pitch, 0,0±0,1º yaw and 0,0±0,1º roll. In the brain it was less than 1,3mm longitudinally, 0,6mm vertically and 0,4mm laterally. The variation found was -0,2±0,2mm lateral, -0,3±0,2mm vertical and -0,4±0,5mm longitudinal. In the rotations, a maximum rotation of 0,3º was obtained, being the variation verified -0,2±0,1º pitch, 0,1±0,1º yaw and of 0,0±0,1º roll. Conclusion: The registration of the synthetic CT image with the CBCT verification image was validated. The minimum deviations found in the results between the planning CT and the synthetic CT of the MRI suggest that the use of the MR-Only technique as a reference image is justified.