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 1 / RADIATION THERAPY PHYSICS

Med. Phys. 39, 195 (2012); http://dx.doi.org/10.1118/1.3666774 (11 pages)

A method for deriving a 4D-interpolated balanced planning target for mobile tumor radiotherapy

Teboh Roland, Russell Hales, Todd McNutt, John Wong, Patricio Simari, and Erik Tryggestad

Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, 401 North Broadway, Baltimore, Maryland 21231

View MapView Map

(Received 28 February 2011; accepted 15 November 2011; revised 31 October 2011; published online 15 December 2011)

Full Text: Read Online (HTML) | Download PDF | Buy PDF (US$30) | View Cart
Purpose: Tumor control and normal tissue toxicity are strongly correlated to the tumor and normal tissue volumes receiving high prescribed dose levels in the course of radiotherapy. Planning target definition is, therefore, crucial to ensure favorable clinical outcomes. This is especially important for stereotactic body radiation therapy of lung cancers, characterized by high fractional doses and steep dose gradients. The shift in recent years from population-based to patient-specific treatment margins, as facilitated by the emergence of 4D medical imaging capabilities, is a major improvement. The commonly used motion-encompassing, or internal-target volume (ITV), target definition approach provides a high likelihood of coverage for the mobile tumor but inevitably exposes healthy tissue to high prescribed dose levels. The goal of this work was to generate an interpolated balanced planning target that takes into account both tumor coverage and normal tissue sparing from high prescribed dose levels, thereby improving on the ITV approach.
Methods: For each 4DCT dataset, 4D deformable image registration was used to derive two bounding targets, namely, a 4D-intersection and a 4D-composite target which minimized normal tissue exposure to high prescribed dose levels and maximized tumor coverage, respectively. Through definition of an “effective overlap volume histogram” the authors derived an “interpolated balanced planning target” intended to balance normal tissue sparing from prescribed doses with tumor coverage. To demonstrate the dosimetric efficacy of the interpolated balanced planning target, the authors performed 4D treatment planning based on deformable image registration of 4D-CT data for five previously treated lung cancer patients. Two 4D plans were generated per patient, one based on the interpolated balanced planning target and the other based on the conventional ITV target. Plans were compared for tumor coverage and the degree of normal tissue sparing resulting from the new approach was quantified.
Results: Analysis of the 4D dose distributions from all five patients showed that while achieving tumor coverage comparable to the ITV approach, the new planning target definition resulted in reductions of lung V10, V20, and V30 of 6.3% ± 1.7%, 10.6% ± 3.9%, and 12.9% ± 5.5%, respectively, as well as reductions in mean lung dose, mean dose to the GTV-ring and mean heart dose of 8.8% ± 2.5%, 7.2% ± 2.5%, and 10.6% ± 3.6%, respectively.
Conclusions: The authors have developed a simple and systematic approach to generate a 4D-interpolated balanced planning target volume that implicitly incorporates the dynamics of respiratory-organ motion without requiring 4D-dose computation or optimization. Preliminary results based on 4D-CT data of five previously treated lung patients showed that this new planning target approach may improve normal tissue sparing without sacrificing tumor coverage.

© 2012 American Association of Physicists in Medicine

ACKNOWLEDGMENTS

This work was supported in part by a grant from Partnership for Cures/LUNGevity foundation. The authors would like to thank Nicolette O’Connell and Elekta CMS for providing the ABAS software.

Article Outline

  1. INTRODUCTION
  2. MATERIALS AND METHODS
    1. Planning target definition
      1. The ITV target
      2. The 4D-interpolated target
        1. Overlap volume index and the bounding targets.
        2. Target interpolation.
    2. Overlap volume histogram (OVH) and the 4D-interpolated balanced planning target estimation
    3. 4D planning for derivation of dosimetric benefits
  3. RESULTS
    1. Planning target definition
    2. OVH and the interpolated balanced planning target estimation
    3. Dosimetric benefit of the interpolated balanced planning target
  4. DISCUSSION
  5. CONCLUSION
Digital Object Identifier
http://dx.doi.org/10.1118/1.3666774

KEYWORDS and PACS

Keywords

biological tissues, cancer, cardiology, cellular biophysics, computerised tomography, dosimetry, image registration, lung, medical image processing, radiation therapy, tumours, balanced planning target derivation, deformable image registration on a GPU

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 (5) Tables (2)

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.)

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