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Comprehensive Evaluation of Three Deformation Image Registration Algorithms Using Digital Phantoms Created From Patients with Head and Neck Cancer

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Z Shen

Z Shen1*, K Bzdusek2, Q Shang1, P Xia1, (1) Cleveland Clinic, Cleveland, OH, (2) Philips Healthcare, Fitchburg, WI


SU-E-J-166 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To create digital phantoms using paired planning and replanning CTs from patients with H&N cancer and to comprehensively evaluate three commonly-used deformable image registration (DIR) algorithms with known ROIs and volumetric doses from the established phantoms.

Methods: We have identified five H&N patients with adaptive-IMRT. For each patient, manually-adjusted meshes were created for selected physician-approved ROIs. These meshes were applied to drive the thin-plate spline algorithm to deform the planning CT to match the replanning CT. The digital phantom consisted of the planning CT and simulated replanning CT, which were linked by a known deformation vector field (DVF). Three DIR algorithms (Fast-Symmetric Demons, B-Spline, and intensity-based) were applied to these five digital phantoms. The images, ROIs, and volumetric doses were mapped from the planning CT to the simulated replanning CT using the DVFs computed by these three DIRs and compared to those using the known DVF.

Results: The average normalized cross-correlation (NCC) value between planning and replanning CTs with rigid registration was 0.924, indicating large anatomical changes. The NCC values were improved to 0.998, 0.974, and 0.996, with Demons, B-Spline, and intensity-based DIRs, respectively. The mean Dice coefficients for selected ROIs (e.g. PTV, brainstem, spinal cord, mandible, parotids) were in the range of 0.87-0.95, 0.84-0.94, and 0.85-0.95 for Demons, B-Spline, and intensity-based DIRs, respectively. The mean slice-wise Hausdorff distances for selected ROIs were in the range of 1.8-4.9 mm, 2.2-5.4 mm, and 2.4-6.6 mm for Demons, B-Spline, and intensity-based DIRs, respectively. The average percentage of voxels in the external contours that have dose errors <2Gy were 88.6%, 85.7%, and 90.7% for Demons, B-Spline, and intensity-based DIRs, respectively.

Conclusion: All three DIR algorithms were very comparable. The deformed images, ROIs, and volumetric doses obtained by these three DIRs agreed well with those mapped from the known DVF.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by a research grant from Philips Healthcare. Karl Bzdusek is an employee of Philips Healthcare.

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