Treatment planning of intracranial targets on MRI derived substitute CT data |
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Authors: | Joakim H. Jonsson,Adam Johansson,Karin Sö derströ m,Thomas Asklund,Tufve Nyholm |
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Affiliation: | 1. Radiation Physics, Department of Radiation Sciences, Umeå University, Sweden;2. Oncology, Department of Radiation Sciences, Umeå University, Sweden |
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Abstract: | BackgroundThe use of magnetic resonance imaging (MRI) as a complement to computed tomography (CT) in the target definition procedure for radiotherapy is increasing. To eliminate systematic uncertainties due to image registration, a workflow based entirely on MRI may be preferable. In the present pilot study, we investigate dose calculation accuracy for automatically generated substitute CT (s-CT) images of the head based on MRI. We also produce digitally reconstructed radiographs (DRRs) from s-CT data to evaluate the feasibility of patient positioning based on MR images.Methods and materialsFive patients were included in the study. The dose calculation was performed on CT, s-CT, s-CT data without inhomogeneity correction and bulk density assigned MRI images. Evaluation of the results was performed using point dose and dose volume histogram (DVH) comparisons, and gamma index evaluation.ResultsThe results demonstrate that the s-CT images improve the dose calculation accuracy compared to the method of non-inhomogeneity corrected dose calculations (mean improvement 2.0% points) and that it performs almost identically to the method of bulk density assignment. The s-CT based DRRs appear to be adequate for patient positioning of intra-cranial targets, although further investigation is needed on this subject.ConclusionThe s-CT method is very fast and yields data that can be used for treatment planning without sacrificing accuracy. |
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Keywords: | Magnetic resonance Radiotherapy Treatment planning Dose calculation Substitute CT |
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