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

Journal article

INTRODUCTION: Correct 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 METHODS: Three 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). RESULTS: Intra-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). CONCLUSION: ITVs created in stage I tumors using DR were closer to 'clinically optimal' ITVs than was the case with a MIP-modified approach.

Authors: van Dam, I; de Koste, v; Hanna, G; Muirhead, R; Slotman, B

• Publication status: Published
• Journal: Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology
• Volume: 96
• Issue: 1
• Pages: 67-72
• Publication date: 2010-07-01
• DOI: 10.1016/j.radonc.2010.05.003
• EISSN: 1879-0887
• ISSN: 0167-8140
• Language: English
• Keywords: Four-Dimensional Computed Tomography; Neoplasm Staging; Sampling Studies; Radiosurgery; Humans; Male; Observer Variation; Female; Lung Neoplasms; Carcinoma, Non-Small-Cell Lung; Radiotherapy Planning, Computer-Assisted