Room: Exhibit Hall | Forum 5
Purpose: We investigate the effect of deformation parameters on deformable image registration (DIR) mapping of simulated pulmonary DIR-based ventilation images using a novel non-rigid deformable phantom that ventilates air.
Methods: Computed tomography images of the phantom were acquired at exhale and inhale phases. Xenon gas was injected into the phantom, as an inhaled contrast agent. The exhalation image was deformed to an inhalation image with an in-house program using the NiftyReg software. Four DIR parameter settings (parameter A for a two-step deformation, and three sets (parameters B, C, and D) with different bending-energy penalty values for a four-step deformation) were compared to evaluate the spatial and DIR-based ventilation image accuracies. For the spatial accuracy, the target registration error (TRE) between the inhalation image and defo rmed exhalation image was calculated for sixteen landmarks. For the accuracy of the ventilation image, DIR-based ventilation images were generated using Jacobian determinant (JD) metrics, and changes in Hounsfield unit (HU) values between the inhalation image and deformed exhalation image were subsequently measured. In addition, the correlation coefficient between the JD metric and changes in the HU was calculated.
Results: The mean TRE values for the parameters A, B, C, and D, were 4.5 Â± 4.7 mm (maximum: 12.3 mm), 1.47 Â± 0.71 mm (maximum: 2.6 mm), 1.56 Â± 0.70 mm (maximum: 2.8 mm), and 1.53 Â± 0.66 mm (maximum: 2.5 mm), respectively. The parameters B, C, and D exhibited stronger correlations with coefficients of R = âˆ’0.71, âˆ’0.65, and âˆ’0.61, respectively, compared with that of the parameter A of R = âˆ’0.40.
Conclusion: We investigated the effect of deformation parameters on DIR mapping of simulated pulmonary ventilation using a non-rigid phantom. The accuracy of the DIR-based ventilation image could vary with the deformation parameters, although a spatial accuracy was achieved.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by Grant-in-Aid for JSPS Research Fellow.