• Neurosurg Focus · Jul 2005

    Comparative Study

    Dynamic collimator optimization compared with fixed collimator angle in arc-based stereotactic radiotherapy: a dosimetric analysis.

    • Christopher M Lee, Gordon A Watson, and Dennis D Leavitt.
    • Department of Radiation Oncology, University of Utah, Huntsman Cancer Institute, Latter-Day Saints Hospital, Salt Lake City, Utah, USA.
    • Neurosurg Focus. 2005 Jul 15; 19 (1): E12.

    ObjectThe purpose of this study was to determine the effect of static and dynamic collimator optimization when using a micromultileaf collimator (mMLC) in dynamic-arc stereotactic radiosurgery (SRS) by evaluating the dose to healthy peritumoral tissue.MethodsThirty patients previously treated for intracranial lesions with the BrainLAB mMLC underwent retrospective replanning. Three collimator optimization strategies were compared for a simulated SRS treatment plan, as follows: Strategy 1, static collimation fixed at 90 degrees throughout arcs; Strategy 2, static collimator settings optimized for each arc; and Strategy 3, dynamic collimator settings optimized every 10 degrees throughout treatment arcs. Dose-volume histograms for a 0.7-cm shell of healthy peritumoral tissue were quantitatively compared. Collimator optimization schemes (Strategies 2 and 3) significantly decreased the volume of peritumoral tissue that is irradiated when compared with static collimation at 90 degrees (Strategy 1). The volume was reduced by 40.6% for Strategy 2 (95% confidence interval [CI] +/- 11) and by 47.1% for Strategy 3 (95% CI +/- 8.1) at the 95% isodose; by 28.4% for Strategy 2 (95% CI +/- 4.9) and 39.1% for Strategy 3 (95% CI +/- 6) at the 90% isodose; and by 18.2% for Strategy 2 (95% CI +/- 8.1) and 25.4% for Strategy 3 (95% CI +/- 7.1) at the 80% isodose. Serial collimator optimization throughout the treatment arcs (Strategy 3) reduced the mean volume of peritumoral tissue irradiated when compared with static collimator optimization (Strategy 2), by 16.1% (95% CI +/- 1.5) at 95% isodose, by 11.7% (95% CI +/- 1) at 90% isodose, and by 8.2% (95% CI +/- 1.2) at 80% isodose regions. In specific cases, linear or polynomial functions were formulated to optimize collimator settings dynamically throughout treatment arcs.ConclusionsDynamic collimator optimization during arc-based SRS decreases the volume of healthy peritumoral tissue treated with high doses of radiation and appears to be an effective method of improving target conformality. This study is the first step toward determination of a smoothing function algorithm to allow for true dynamic collimation during SRS.

      Pubmed     Full text   Copy Citation     Plaintext  

      Add institutional full text...

    Notes

     
    Knowledge, pearl, summary or comment to share?
    300 characters remaining
    help        
    You can also include formatting, links, images and footnotes in your notes
    • Simple formatting can be added to notes, such as *italics*, _underline_ or **bold**.
    • Superscript can be denoted by <sup>text</sup> and subscript <sub>text</sub>.
    • Numbered or bulleted lists can be created using either numbered lines 1. 2. 3., hyphens - or asterisks *.
    • Links can be included with: [my link to pubmed](http://pubmed.com)
    • Images can be included with: ![alt text](https://bestmedicaljournal.com/study_graph.jpg "Image Title Text")
    • For footnotes use [^1](This is a footnote.) inline.
    • Or use an inline reference [^1] to refer to a longer footnote elseweher in the document [^1]: This is a long footnote..

    hide…