Evaluation of deformation parameters for deformable image registration-based ventilation imaging using an air-ventilating non-rigid phantom. (June 2018)

• Record Type: Journal Article
• Authors: Miyakawa, Shin; Tachibana, Hidenobu; Moriya, Shunsuke; Kurosawa, Tomoyuki; Nishio, Teiji
• Is Part Of: Physica medica. Volume 50(2018)
• Page Start: 20
• Page End: 25
• Publication Date: 2018-06
• Subjects: DIR-based ventilation image -- Xenon gas -- Non-rigid phantom -- Deformable image registration; Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.05.016
• Languages: English
• ISSNs: 1120-1797

Abstract

Highlights: CT ventilation image (CT-V) is generated by using deformable image registration (DIR). Effects of DIR parameters on CT-V were examined using a ventilation phantom. Small changes in the DIR parameters resulted in large relative changes in CT-V. The accuracy of CT-V images may be variable in different DIR parameter settings. Adequate DIR parameter settings were found for the NiftyReg package. Abstract: Purpose: This study aimed to evaluate different deformable image registration (DIR) parameters for the open-source NiftyReg package in its application to DIR-based ventilation imaging. Methods: Two three-dimensional (3D)-computed tomography (CT) scans of a non-rigid air-ventilating phantom were acquired at peak exhalation and peak inhalation, with xenon (Xe) gas being used as an air-based contrast agent. We compared four different sets of DIR parameters, including one set with two-step deformation and three sets with four-step deformation. For spatial accuracy, the target registration error (TRE) was calculated for 16 landmarks. For ventilation imaging accuracy, DIR-based ventilation images were generated using Jacobian determinant (JD) metrics, and changes in Hounsfield unit (HU) values between the two exhalation and inhalation CT images were subsequently measured. The correlation coefficients between the JD metrics and changes in HU values were calculated. Results: The mean TRE values were 4.5 ± 4.7 mm (maximum, 12.3 mm), 1.47 ± 0.71 mm (maximum, 2.6 mm), 1.56 ± 0.70 mm (maximum, 2.8 mm), and 1.53 ± 0.66 mm (maximum, 2.5 mm) for the two-step deformation and three four-step deformations, respectively. The four-step deformations (R = − 0.71, −0.65, and −0.61) showed stronger correlation coefficients than the two-step deformation (R = −0.40). Conclusions: The accuracy of DIR-based ventilation imaging may vary with different DIR parameter settings, even though spatial accuracy may be tolerable and within guidelines. We found adequate parameter settings for four-step NiftyReg DIR for visualization of simulated pulmonary ventilation function.