Quantification of confounding factors in MRI-based dose calculations as applied to prostate IMRT
| Autor: | Cornelis A. T. van den Berg, Gerald Schubert, Peter R. Seevinck, Matteo Maspero, Bram van Asselen, Gert J. Meijer, Michaela A.U. Hoesl, Max A. Viergever, Jan J.W. Lagendijk |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
Male
medicine.medical_specialty radiotherapy planning Dose calculation medicine.medical_treatment quality assurance Radiation Dosage 030218 nuclear medicine & medical imaging magnetic resonance 03 medical and health sciences 0302 clinical medicine Prostate Journal Article Humans Medicine Radiology Nuclear Medicine and imaging intensity modulated radiotherapy Radiation treatment planning dosimetry Radiological and Ultrasound Technology medicine.diagnostic_test MR-only treatment planning business.industry Radiotherapy Planning Computer-Assisted Confounding Prostatic Neoplasms Magnetic resonance imaging Gold standard (test) Magnetic Resonance Imaging Radiation therapy medicine.anatomical_structure 030220 oncology & carcinogenesis Radiology Tomography magnetic resonance radiotherapy planning dosimetry MR-only treatment planning intensity modulated radiotherapy quality assurance Tomography X-Ray Computed business Nuclear medicine |
| Zdroj: | Physics in Medicine and Biology, 62(3), 948. IOP Publishing Ltd. |
| ISSN: | 0031-9155 |
| Popis: | Magnetic resonance (MR)-only radiotherapy treatment planning requires pseudo-CT (pCT) images to enable MR-based dose calculations. To verify the accuracy of MR-based dose calculations, institutions interested in introducing MR-only planning will have to compare pCT-based and computer tomography (CT)-based dose calculations. However, interpreting such comparison studies may be challenging, since potential differences arise from a range of confounding factors which are not necessarily specific to MR-only planning. Therefore, the aim of this study is to identify and quantify the contribution of factors confounding dosimetric accuracy estimation in comparison studies between CT and pCT. The following factors were distinguished: set-up and positioning differences between imaging sessions, MR-related geometric inaccuracy, pCT generation, use of specific calibration curves to convert pCT into electron density information, and registration errors. The study comprised fourteen prostate cancer patients who underwent CT/MRI-based treatment planning. To enable pCT generation, a commercial solution (MRCAT, Philips Healthcare, Vantaa, Finland) was adopted. IMRT plans were calculated on CT (gold standard) and pCTs. Dose difference maps in a high dose region (CTV) and in the body volume were evaluated, and the contribution to dose errors of possible confounding factors was individually quantified. We found that the largest confounding factor leading to dose difference was the use of different calibration curves to convert pCT and CT into electron density (0.7%). The second largest factor was the pCT generation which resulted in pCT stratified into a fixed number of tissue classes (0.16%). Inter-scan differences due to patient repositioning, MR-related geometric inaccuracy, and registration errors did not significantly contribute to dose differences (0.01%). The proposed approach successfully identified and quantified the factors confounding accurate MRI-based dose calculation in the prostate. This study will be valuable for institutions interested in introducing MR-only dose planning in their clinical practice. |
| Databáze: | OpenAIRE |
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