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Most respiratory-induced target motion data have been measured at only a few points, the centroid and the edge. Due to organ deformation, volumetric measurement is more appropriate than point measurement. Previously, we proposed a quantitative method to evaluate respiratory-induced organ motion using deformable image registration (DIR), called vector volume histogram (VVH). However, the process of VVH was very complicated and no one can use the VVH because the deformation vector field (DVF) was calculated on the treatment planning system (TPS) and the file format was converted by in-house software. We developed a volumetric quantitative evaluation user-friendly software to evaluate respiratory-induced organ motion using DIR. The B-spline-based DIR algorithm was used to compute the DVF, which includes DVF LR (left-right), DVF AP (anterior-posterior), and DVF CC (cranio-caudal). The VVH function was written in Python. Two sets of images were required for DIR in the VVH software: a reference image set and a registered image set. The VVH was a calculation method similar to the dose volume histogram. In the VVH software, the user could change the result of the direction by selecting a combo box. Other features included a calculation index, changing the range of the x and y axes, a tracking bar, and exporting to a CSV file. A displaced target within a moving phantom was used to evaluate the performance of the VVH system. The 2 cm diameter target was systematically displaced 5, 10, 15, and 20 mm in the CC direction. To evaluate respiration-induced target motion, the VVH method was applied to the inhalation and exhalation phases of 4D CT scans in 5 patients with lung cancer. L 5% (length at 5% volume) and L 50% (length at 50% volume) were calculated to evaluate target motion. Target centroid was measured for comparison with VVH methods. In the phantom study, L 5% and L 50% were 5 mm versus 4.7 mm, 9.7 mm versus 10.3 mm, 14.7 mm versus 14.9 mm, and 19.7 mm versus 20.0 mm for displacements of 5, 10, 15, and 20 mm, respectively. In the patient study, the average difference between the L 5% and L 50% methods and the centroid methods was as follows: L 5% and L 50% were 0.2 mm versus 0.5 mm, 0.3 mm versus 0.6 mm, and 2.0 mm versus 0.8 mm in the LR, AP, and CC directions, respectively. Although it was difficult to decide which index to use, the centroid and L 50% results were close. The performance of VVH depends on the accuracy of the DIR algorithm and the extent of anatomic changes. The performance of the VVH software was demonstrated by verifying the phantom and the patient with tumor motion. The VVH software provided a volumetric quantitative assessment of respiratory-induced target motion, which in its clinical application can provide strategy-decision at the time of treatment planning. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to find descriptors that correlates with normal brain dose to determine the feasibility of performing fractionated stereotactic radiosurgery (SRS) for multiple brain metastases (BMs) using five linac machines., Methods: Thirty-two patients with 1-30 BMs were enrolled. Treatment plans were created using TrueBeam, Novalis Tx, TrueBeam Edge, Halcyon, and Tomotherapy linacs. The sum of all planning target volumes (PTVs) was defined as PTV all , and the brain region excluding PTV all was defined as normal brain. The total surface area (TSA) of the PTV was calculated from the sum of the surface areas of the equivalent spheres for each PTV. Volumes receiving more than 5, 12, and 18 Gy (V 5Gy , V 12Gy , and V 18Gy , respectively) were used for evaluation of normal brain dose. Correlations between normal brain dose and each tumor characteristic (number, PTV all , and TSA) were investigated using the Spearman rank correlation coefficient., Results: Correlations between each characteristic and normal brain dose were statistically significant (p < 0.05) across all machines. The correlation coefficients between each characteristic and V 18Gy for the five machines were as follows: tumor number, 0.39-0.60; PTV all , 0.79-0.93; TSA, 0.93-0.99. The fit equations between TSA and V 18Gy exhibited high coefficients of determination, ranging from 0.92 to 0.99 across five machines., Conclusion: This study devised fractionated SRS plans using for 1-30 BMs across five linac machines to find descriptors for determining SRS feasibility based on normal brain dose. TSA proved to be a promising descriptor of SRS feasibility for treating multiple BMs., (© 2024 The Author(s). Journal of Applied Clinical Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)