• Int. J. Radiat. Oncol. Biol. Phys. · Apr 2000

    Optimization of beam weights in conformal radiotherapy planning of stage III non-small cell lung cancer: effects on therapeutic ratio.

    • W R De Gersem, S Derycke, C De Wagter, and W C De Neve.
    • Division of Radiotherapy, University Hospital, Gent, Belgium.
    • Int. J. Radiat. Oncol. Biol. Phys. 2000 Apr 1; 47 (1): 255-60.

    PurposeTo evaluate the effects of beam weight optimization for 3D conformal radiotherapy plans, with or without beam intensity modulation, in Stage III non-small cell lung cancer (NSCLC).Methods And MaterialsTen patients with Stage III NSCLC were planned using a conventional 3D technique and a technique involving noncoplanar beam intensity modulation (BIM). Two planning target volumes (PTVs) were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic tumor volume. Virtual simulation defined the beam shapes and incidences as well as the wedge orientations (3D) and segment outlines (BIM). Weights of wedged beams, unwedged beams, and segments were determined by human trial and error for the 3D-plans (3D-manual), by a standard weight table (SWT) for the BIM-plans (BIM-SWT) and by optimization (3D-optimized and BIM-optimized) using an objective function with a biological and a physical component. The resulting non-optimized and optimized dose distributions were compared, using physical endpoints, after normalizing the median dose of PTV1 to 80 Gy.ResultsOptimization improved dose homogeneity at the target for 3D- and BIM-plans and the minimum dose at PTV1. The minimum dose at PTV2 was decreased by optimization especially in 3D-plans. After optimization, the dose-volume histograms (DVHs) of lung and heart were shifted to lower doses for 80-90% of the organ volume. Since lung is the dose-limiting organ in Stage III NSCLC, an increased minimum dose at PTV1 together with a decreased dose at the main lung volume suggests an improved therapeutic ratio. Optimization allows 10% dose escalation for 3D-plans and 20% for BIM-plans at isotoxicity levels of lung and spinal cord. Upon dose escalation, esophagus may become the dose-limiting structure when PTV1 extends close to the esophagus.ConclusionsOptimization using a biophysical objective function allowed an increase of the therapeutic ratio of radiotherapy planning for Stage III NSCLC.

      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…