| Effects of geometric distortion in 0.2T MRI on radiotherapy treatment planning of prostate cancer. | |
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MedLine Citation:
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PMID: 15066296 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND AND PURPOSE: To evaluate the impact of two different methods of geometric distortion correction of MR images from a Siemens Magnetom Open Viva 0.2T resistive MR unit on the process of external beam radiotherapy treatment planning for prostate cancer. PATIENTS AND METHODS: A method for correction of system related and object induced distortions and one for correction of purely system related distortions have been evaluated. The latter used information extracted from MR images of a 3D phantom specifically designed for geometric distortion evaluation. An active shim procedure was performed prior to all phantom and patient scans. For each of five patients five standard treatment plans were compared using uncorrected and corrected MR images alone (density=water) and CT images alone. Finally internal anatomical landmarks were used for image registration between MR images (corrected and uncorrected) and CT images to evaluate the impact of distortion correction on the image registration process. RESULTS: Maximum distortions of 28 mm (mean 2.2 mm) were found within the FOV in frequency encode direction. Maximum distortions could be reduced by a factor of two (mean factor four) by our phantom measurement based technique. Distortion patterns were found to be stable and reproducible over several weeks with this MR unit. For 4/5 patients, relative doses at the normalization point as calculated on the distortion corrected MR images only (all tissues taken water equivalent) were all within 1% of the corresponding value from the standard CT-based plan (actual Hounsfield units). The largest differences in isocentric dose found in one case were 3.1% MR uncorrected vs. CT and 2.6% MR corrected vs. CT. Typical sites of internal anatomical landmarks chosen for image registration show distortions up to 3 mm. CONCLUSIONS: Object induced distortions are negligible at such low field strengths compared to system related distortions. Treatment plans for prostate cancer do not seem to differ significantly from "standard" plans calculated on CT images when calculated on distortion corrected MR images, even if all tissues are assigned the electron density of water. Distortion correction of MR images can theoretically improve the starting point for image registration of MR and CT images. |
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Authors:
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Bernhard Petersch; Joachim Bogner; Annette Fransson; Thomas Lorang; Richard Pötter |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology Volume: 71 ISSN: 0167-8140 ISO Abbreviation: Radiother Oncol Publication Date: 2004 Apr |
Date Detail:
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Created Date: 2004-04-06 Completed Date: 2004-08-05 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 8407192 Medline TA: Radiother Oncol Country: Ireland |
Other Details:
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Languages: eng Pagination: 55-64 Citation Subset: IM |
Affiliation:
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Division Medical Radiation Physics, Department of Radiotherapy and Radiobiology, University of Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Humans Image Processing, Computer-Assisted / methods Magnetic Resonance Imaging* Male Phantoms, Imaging Prostatic Neoplasms / diagnosis*, radiotherapy* Radiotherapy Dosage Radiotherapy Planning, Computer-Assisted* Tomography, X-Ray Computed |
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