• Radiother Oncol · Jul 2010

    Comparative Study

    Improving target delineation on 4-dimensional CT scans in stage I NSCLC using a deformable registration tool.

    • Iris E van Dam, John R van Sörnsen de Koste, Gerard G Hanna, Rebecca Muirhead, Ben J Slotman, and Suresh Senan.
    • Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
    • Radiother Oncol. 2010 Jul 1; 96 (1): 67-72.

    IntroductionCorrect target definition is crucial in stereotactic radiotherapy for lung tumors. We evaluated use of deformable registration (DR) for target contouring on 4-dimensional (4D) CT scans.Materials And MethodsThree clinicians contoured gross tumor volume (GTV) in an end-inspiration phase of 4DCT of 6 patients on two occasions. Two clinicians contoured GTVs in all phases of 4DCT and on maximum intensity projections (MIP). The initial GTV was auto-propagated to 9 other phases using a B-spline algorithm (VelocityAI). Internal target volumes (ITVs) generated were (i) ITV(10manual) encompassing all physician-contoured GTVs, (ii) ITV-MIP(optimized) from MIP after review of individual 4DCT phases, (iii) ITV(10deformed) encompassing auto-propagated GTVs using DR, and (iv) ITV(10deformed-optimized), from an ITV(10deformed) target that was modified to form a 'clinically optimal' ITV. Volume-overlaps were scored using Dice's Similarity Coefficients (DSCs).ResultsIntra-clinician GTV reproducibility was greater than inter-clinician reproducibility (mean DSC 0.93 vs. 0.88, p<0.0004). In five of 6 patients, ITV-MIP(optimized) differed from the ITV(10deformed-optimized). In all patients, the DSC between ITV(10deformed-optimized) and ITV(10deformed) was higher than that between ITV(10deformed-optimized) and ITV-MIP(optimized) (p<0.02 T-test).ConclusionITVs created in stage I tumors using DR were closer to 'clinically optimal' ITVs than was the case with a MIP-modified approach.Copyright 2010 Elsevier Ireland Ltd. All rights reserved.

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