AAPM Banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

You are not logged in Access to this article requires a subscription. Log In

Medical Physics / Volume 39 / Issue 2 / RADIATION THERAPY PHYSICS

Med. Phys. 39, 573 (2012); http://dx.doi.org/10.1118/1.3673772 (8 pages)

A method to estimate the effect of deformable image registration uncertainties on daily dose mapping

Martin J. Murphy, Francisco J. Salguero, Jeffrey V. Siebers, David Staub, and Constantin Vaman

Department of Radiation Oncology, Virginia Commonwealth University, Richmond Virginia 23298

View MapView Map

(Received 26 April 2011; accepted 8 December 2011; revised 28 November 2011; published online 11 January 2012)

Full Text: Read Online (HTML) | Download PDF | Buy PDF (US$30) | View Cart
Purpose: To develop a statistical sampling procedure for spatially-correlated uncertainties in deformable image registration and then use it to demonstrate their effect on daily dose mapping.
Methods: Sequential daily CT studies are acquired to map anatomical variations prior to fractionated external beam radiotherapy. The CTs are deformably registered to the planning CT to obtain displacement vector fields (DVFs). The DVFs are used to accumulate the dose delivered each day onto the planning CT. Each DVF has spatially-correlated uncertainties associated with it. Principal components analysis (PCA) is applied to measured DVF error maps to produce decorrelated principal component modes of the errors. The modes are sampled independently and reconstructed to produce synthetic registration error maps. The synthetic error maps are convolved with dose mapped via deformable registration to model the resulting uncertainty in the dose mapping. The results are compared to the dose mapping uncertainty that would result from uncorrelated DVF errors that vary randomly from voxel to voxel.
Results: The error sampling method is shown to produce synthetic DVF error maps that are statistically indistinguishable from the observed error maps. Spatially-correlated DVF uncertainties modeled by our procedure produce patterns of dose mapping error that are different from that due to randomly distributed uncertainties.
Conclusions: Deformable image registration uncertainties have complex spatial distributions. The authors have developed and tested a method to decorrelate the spatial uncertainties and make statistical samples of highly correlated error maps. The sample error maps can be used to investigate the effect of DVF uncertainties on daily dose mapping via deformable image registration. An initial demonstration of this methodology shows that dose mapping uncertainties can be sensitive to spatial patterns in the DVF uncertainties.

© 2012 American Association of Physicists in Medicine

ACKNOWLEDGMENTS

This work was supported in part by NCI Grant No. P01-CA116602 and in part by Philips Medical Systems.

Article Outline

  1. INTRODUCTION
  2. METHOD AND MATERIALS
    1. Creating a training set of DVF error maps
    2. Principal component analysis of the training set
    3. Estimating the PDFs of the principal coefficients and sampling from them to construct a sample error map
    4. Validating the error sampling procedure
    5. Modeling dose mapping uncertainties
  3. RESULTS
    1. Deformable image registration uncertainties due to ROI choice
    2. PCA of the ROI error maps
    3. Making and validating sample error maps
    4. Mapped dose uncertainty due to the DVF uncertainty associated with ROI choice
  4. DISCUSSION
  5. SUMMARY
Digital Object Identifier
http://dx.doi.org/10.1118/1.3673772

KEYWORDS and PACS

Keywords

computerised tomography, displacement measurement, dosimetry, image registration, principal component analysis, radiation therapy, sampling methods, deformable image registration, probabilistic treatment planning, dose mapping, principal components analysis

PACS

PUBLICATION DATA

ISSN

0094-2405 (print)  

Publisher

$abstract.society.value is a Member of CrossRef American Association of Physicists in Medicine

For access to fully linked references, you need to log in.

Figures (9)

Access to article objects (figures, tables, multimedia) requires a subscription; log in to view available files.
(Access to supplementary files, where available, is free for this journal.)



Close

Medical Physics is an official science journal of the AAPM and of the COMP/CCPM/IOMP
William R. Hendee, Editor
Departments of Radiology, Radiation Oncology, Biophysics, Community and Public Health, Medical College of Wisconsin
One Physics Ellipse
College Park, Maryland 20740
301-209-3352

© 2012, American Association of Physicists in Medicine. Individual readers of this journal, and nonprofit libraries acting for them, are freely permited to make fair use of the material in it, such as to copy an article for use in teaching or research. (For other kinds of copying see "Copying Fees.") Permission is granted to quote from this journal in scientific works with the customary acknowledgment of the source. To reprint a figure, table, or other excerpt requires, in addition, AAPM may require that permission also be obtained from one of the authors. Address inquiries and notices to Penny Slattery, Journal Manager, Medical Physics Journal, AAPM, One Physics Ellipse, College Park, MD 20740-3846; email: journal@aapm.org.

close