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Reproducibility of CT Ventilation Imaging Based On Breath-Hold CT Toward Functional Image-Guided Adaptive Radiotherapy for Lung

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Y Onozato

Y Onozato*, T Shiinoki , H Hanazawa , K Shibuya , Yamaguchi University, Ube, Yamaguchi


TU-C2-GePD-J(A)-2 (Tuesday, August 1, 2017) 10:00 AM - 10:30 AM Room: Joint Imaging-Therapy ePoster Lounge - A

Purpose: 4D-CT ventilation imaging has been applied to radiation therapy. However, the frequency and magnitude of an artifact in 4D-CT were alarmingly higher than those in the breath-hold CT, which may reduce the accuracy of ventilation imaging. The purpose of this study was to quantify the reproducibility of the breath-hold CT-based lung ventilation imaging.

Methods: Eleven lung cancer patients were enrolled in this study. Three breath-hold CT images were acquired for each patient within a short time interval. To calculate the CT-based ventilation imaging, the peak-inhale images were deformed to the peak-exhale images using deformable image registration (DIR) technique. We calculated three lung functional images for each patient based on the results of DIR using three metrics: Hounsfield unit change metric (VHU), Jacobian metric (Vjac) and Density change metric (Vdensity). The reproducibility was quantified using voxel-based Spearman rank correlation coefficients for all lung voxels and dice similarity coefficients (DSC) for the spatial overlap of segmented high, moderate, and low functional lung volumes.

Results: The mean voxel-based correlation among three breath-hold CT-based ventilation images for VHU, Vjac, and Vdensity were 0.60 ± 0.13, 0.60 ± 0.14, and 0.60 ± 0.12, respectively. The mean DSCs were relatively high for the high- (0.61 ± 0.15 (VHU), 0.60 ± 0.13 (Vjac), and 0.60 ± 0.16 (Vdensity)), moderate- (0.56 ± 0.19 (VHU), 0.51 ± 0.17 (Vjac), and 0.55 ± 0.21 (Vdensity)), and low-functional lung (0.61 ± 0.21 (VHU), 0.67 ± 0.15 (Vjac), and 0.60 ± 0.19 (Vdensity)), respectively.

Conclusion: We found that the mean voxel-based correlation and the mean DSCs for VHU, Vjac, and Vdensity were relatively high and the variations of those for each metric were small, indicating that the breath-hold CT-based lung ventilation imaging had high reproducibility. It may provide accurate estimates of the lung function for functional image-guided adaptive radiotherapy.

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