Document Detail

Patient-induced susceptibility effect on geometric distortion of clinical brain MRI for radiation treatment planning on a 3T scanner.
MedLine Citation:
PMID:  23302471     Owner:  NLM     Status:  MEDLINE    
Concerns about the geometric accuracy of MRI in radiation therapy (RT) have been present since its invention. Although modern scanners typically have system levels of geometric accuracy that meet requirements of RT, subject-specific distortion is variable, and methods to in vivo assess and control patient-induced geometric distortion are not yet resolved. This study investigated the nature and magnitude of the subject-induced susceptibility effect on geometric distortions in clinical brain MRI, and tested the feasibility of in vivo quality control using field inhomogeneity mapping. For 19 consecutive patients scanned on a dedicated 3T MR scanner, B0 field inhomogeneity maps were acquired and analyzed to determine subject-induced distortions. For 3D T1 weighted images frequency-encoded with a bandwidth of 180 Hz/pixel, 86.9% of the estimated displacements were <0.5 mm, 97.4% <1 mm, and only 0.1% of displacements > 2 mm. The maximum displacement was <4 mm. The greatest distortions were observed at the interfaces with air at the sinuses. Displacements decayed to less than 1 mm over a distance of 8 mm. Metal surgical wires generated smaller distortions, with an averaged maximum displacement of 0.76 mm. Repeat acquisition of the field maps in 17 patients revealed a within-subject standard deviation of 0.25 ppm, equivalent to 0.22 mm displacement in the frequency-encoding direction in the 3D T1 weighted images. Susceptibility-induced voxel displacements in the brain are generally small, but should be monitored for precision RT. These effects are manageable at 3T and lower fields, and the methods applied can be used to monitor for potential local errors in individual patients, as well as to correct for local distortions as needed.
H Wang; J Balter; Y Cao
Publication Detail:
Type:  Journal Article     Date:  2013-01-10
Journal Detail:
Title:  Physics in medicine and biology     Volume:  58     ISSN:  1361-6560     ISO Abbreviation:  Phys Med Biol     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-16     Completed Date:  2013-06-26     Revised Date:  2014-04-15    
Medline Journal Info:
Nlm Unique ID:  0401220     Medline TA:  Phys Med Biol     Country:  England    
Other Details:
Languages:  eng     Pagination:  465-77     Citation Subset:  IM    
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MeSH Terms
Brain / radiation effects*
Brain Neoplasms / radiotherapy
Feasibility Studies
Magnetic Resonance Imaging*
Radiotherapy Planning, Computer-Assisted / methods*
Radiotherapy, Image-Guided / methods*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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