https://ogma.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42282 Wed 16 Aug 2023 14:37:30 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43582 99mTc-carbon (‘Technegas’), a clinical V-SPECT modality featuring smaller radioaerosol particles with less clumping. Methods: Eleven lung cancer radiotherapy patients with early stage (T1/T2N0) disease received treatment planning four-dimensional CT (4DCT) scans paired with Technegas V/Q-SPECT/CT. For each patient, we applied three different CTVI methods. Two of these used deformable image registration (DIR) to quantify breathing-induced lung density changes (CTVI_DIR-HU), or breathing-induced lung volume changes (CTVI_DIR-Jac) between the 4DCT exhale/inhale phases. A third method calculated the regional product of air-tissue densities (CTVI_HU) and did not involve DIR. Corresponding CTVI and V-SPECT scans were compared using the Dice similarity coefficient (DSC) for functional defect and nondefect regions, as well as the Spearman's correlation r computed over the whole lung. The DIR target registration error (TRE) was quantified using both manual and computer-selected anatomic landmarks. Results: Interestingly, the overall best performing method (CTVI_HU) did not involve DIR. For nondefect regions, the CTVI_HU, CTVI_DIR-HU, and CTVI_DIR-Jac methods achieved mean DSC values of 0.69, 0.68, and 0.54, respectively. For defect regions, the respective DSC values were moderate: 0.39, 0.33, and 0.44. The Spearman r-values were generally weak: 0.26 for CTVI_HU, 0.18 for CTVI_DIR-HU, and −0.02 for CTVI_DIR-Jac. The spatial accuracy of CTVI was not significantly correlated with TRE, however the DIR accuracy itself was poor with TRE > 3.6 mm on average, potentially indicative of poor quality 4DCT. Q-SPECT scans achieved good correlations with V-SPECT (mean r > 0.6), suggesting that the image quality of Technegas V-SPECT was not a limiting factor in this study. Conclusions: We performed a validation of CTVI using clinically available 4DCT and Technegas V/Q-SPECT for 11 lung cancer patients. The results reinforce earlier findings that the spatial accuracy of CTVI exhibits significant interpatient and intermethod variability. We propose that the most likely factor affecting CTVI accuracy was poor image quality of clinical 4DCT.]]> Mon 26 Sep 2022 10:33:32 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:43579 4DCBCT) can complement existing 4DCT-based methods (CTVI^4DCT) to track lung function changes over a course of lung cancer radiation therapy. However, the accuracy of CTVI^4DCBCT needs to be assessed since anatomic 4DCBCT has demonstrably poor image quality and small field of view (FOV) compared to treatment planning 4DCT. We perform a direct comparison between short interval CTVI^4DCBCT and CTVI^4DCT pairs to understand the patient specific image quality factors affecting the intermodality CTVI reproducibility in the clinic. Methods and materials: We analysed 51 pairs of 4DCBCT and 4DCT scans acquired within 1 day of each other for nine lung cancer patients. To assess the impact of image quality, CTVIs were derived from 4DCBCT scans reconstructed using both standard Feldkamp-Davis-Kress backprojection (CTVI4DCBCT/FDK) and an iterative McKinnon-Bates Simultaneous Algebraic Reconstruction Technique (CTVI4DCBCT/MKBSART). Also, the influence of FOV was assessed by deriving CTVIs from 4DCT scans that were cropped to a similar FOV as the 4DCBCT scans (CTVI4DCT/crop), or uncropped (CTVI4DCT/uncrop). All CTVIs were derived by performing deformable image registration (DIR) between the exhale and inhale phases and evaluating the Jacobian determinant of deformation. Reproducibility between corresponding CTVI^4DCBCT and CTVI^4DCT pairs was quantified using the voxel-wise Spearman rank correlation and the Dice similarity coefficient (DSC) for ventilation defect regions (identified as the lower quartile of ventilation values). Mann–Whitney U-tests were applied to determine statistical significance of each reconstruction and cropping condition. Results: The (mean ± SD) Spearman correlation between CTVIRDCBCT/FDK and CTVI4DCT/uncrop was 0.60 ± 0.23 (range −0.03–0.88) and the DSC was 0.64 ± 0.12 (0.34–0.83). By comparison, correlations between CTVI4DCBCT/MKBSART and CTVI4DCTuncrop showed a small but statistically significant improvement with = 0.64 ± 0.20 (range 0.06–0.90, P = 0.03) and DSC = 0.66 ± 0.13 (0.31–0.87, P = 0.02). Intermodal correlations were noted to decrease with an increasing fraction of lung truncation in 4DCBCT relative to 4DCT, albeit not significantly (Pearson correlation R = 0.58, P = 0.002). Conclusions: This study demonstrates that DIR based CTVIs derived from 4DCBCT can exhibit reasonable to good voxel-level agreement with CTVIs derived from 4DCT. These correlations outperform previous cross-modality comparisons between 4DCT-based ventilation and nuclear medicine. The use of 4DCBCT scans with iterative reconstruction and minimal lung truncation is recommended to ensure better reproducibility between 4DCBCT- and 4DCT-based CTVIs.]]> Mon 26 Sep 2022 10:30:30 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:47480 Mon 23 Jan 2023 11:40:34 AEDT ]]>