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Background Purpose Methods and materials Results Conclusion Radiation therapy often requires the accumulation of doses from multiple treatment fractions or courses for plan evaluation and treatment response assessment. However, due to underlying mass changes, the accumulated dose may not accurately reflect the total deposited energy, leading to potential inaccuracies in characterizing the treatment input.This study introduces an energy‐conserving dose summation method to calculate the total dose in scenarios where patients experience changes in body mass during treatment.The proposed method transfers dose and mass data from dosimetry images, where the delivered doses were calculated, to a reference image using an energy and mass‐conserving dose reconstruction technique. The reconstructed dose assumes the same resolution and dimension as the reference image. The transferred masses are averaged at each image voxel in the reference image to generate an average mass. The transferred doses are then adjusted by multiplying by the ratio of their transferred mass to the average mass, and subsequently summed to calculate a mass‐weighted (MW) total dose at each voxel. This method is demonstrated with a case of lung cancer retreatment.The MW total dose was shown to be equivalent to the total deposited energy divided by the average mass. In the lung cancer retreatment case, the energy derived from the MW total dose was consistent with the sum of energy transferred from two treatments across all evaluated organs.The MW dose summation method can produce a total dose that accurately reflects the total energy deposited in each organ. The consistency may provide a robust foundation for verifying dose accumulations in adaptive radiotherapy. [ABSTRACT FROM AUTHOR]

This article explores the role of Deformable Dose Accumulation (DDA) in Adaptive Radiotherapy (ART). DDA involves combining doses from different treatment sessions to ensure optimal dose delivery and respect dose constraints. Dr. Hualiang Zhong supports DDA, emphasizing its ability to improve cumulative dose calculations, while Dr. Jennifer Pursley raises concerns about the uncertainties and limitations of DDA. Both perspectives offer valuable insights for medical physicists and radiation oncologists. While DDA is considered important for ART, caution is advised due to challenges in accurately registering deformable images. The article also discusses alternative approaches to estimate delivered dose, such as using the original treatment plan or accumulating specific dose parameters across fractions. The rebuttal section presents differing opinions on the usefulness and accuracy of DDA, with one author suggesting that DDA can provide more informative dose distributions if errors are properly managed, while the other author proposes direct dose summation as a more practical and consistent approach for online ART. [Extracted from the article]

Purpose: We evaluate the performance of a deformable image registration (DIR) software package in registering abdominal magnetic resonance images (MRIs) and then develop a mechanical modeling method to mitigate detected DIR uncertainties. Materials and Methods: Three evaluation metrics, namely mean displacement to agreement (MDA), DICE similarity coefficient (DSC), and standard deviation of Jacobian determinants (STD‐JD), are used to assess the multi‐modality (MM), contour‐consistency (CC), and image‐intensity (II)‐based DIR algorithms in the MIM software package, as well as an in‐house developed, contour matching‐based finite element method (CM‐FEM). Furthermore, we develop a hybrid FEM registration technique to modify the displacement vector field of each MIM registration. The MIM and FEM registrations were evaluated on MRIs obtained from 10 abdominal cancer patients. One‐tailed Wilcoxon‐Mann‐Whitney (WMW) tests were conducted to compare the MIM registrations with their FEM modifications. Results: For the registrations performed with the MIM‐CC, MIM‐MM, MIM‐II, and CM‐FEM algorithms, their average MDAs are 0.62 ± 0.27, 2.39 ± 1.30, 3.07 ± 2.42, 1.04 ± 0.72 mm, and average DSCs are 0.94 ± 0.03, 0.80 ± 0.12, 0.77 ± 0.15, 0.90 ± 0.11, respectively. The p‐values of the WMW tests between the MIM registrations and their FEM modifications are less than 0.0084 for STD‐JDs and greater than 0.87 for MDA and DSC. Conclusions: Among the three MIM DIR algorithms, MIM‐CC shows the smallest errors in terms of MDA and DSC but exhibits significant Jacobian uncertainties in the interior regions of abdominal organs. The hybrid FEM technique effectively mitigates the Jacobian uncertainties in these regions. [ABSTRACT FROM AUTHOR]

Purpose: We present a DVH overlay technique as a quality assurance (QA) metric for deformable image registration‐based dose accumulation (DIR‐DA). We use the technique to estimate the uncertainty in a DIR‐DA for a revised treatment plan, and to compare two different DIR algorithms. Materials and methods: The required inputs to the DVH overlay workflow are deformably registered primary and secondary images, primary regions‐of‐interest (ROIs), and secondary dose distribution. The primary ROIs were forward warped to the secondary image, the secondary dose was inversely warped to the primary image, and the DVHs for each image were compiled. Congruent DVHs imply minimal inverse consistency error (ICE) within an ROI. For a pancreas case re‐planned after 21 fractions of a 29‐fraction course, the workflow was used to quantify dose accumulation error attributable to ICE, based on a hybrid contour‐and‐intensity‐based DIR. The usefulness of the workflow was further demonstrated by assessing the performance of two DIR algorithms (one free‐form intensity‐based, FFIB, the other using normalized correlation coefficients, NCC, over small neighborhood patches) as applied toward kilovoltage computed tomography (kVCT)‐to‐megavoltage computed tomography (MVCT) registration and five‐fraction dose accumulation of ten male pelvis cases. Results: For the re‐planned pancreas case, when applying the DVH‐overlay‐based uncertainties the resulting accumulated dose remained compliant with all but two of the original plan objectives. Among the male pelvis cases, FFIB and NCC DIR showed good invertibility within the planning target volume (PTV), according to the DVH overlay QA results. NCC DIR exhibited better invertibility for the bladder and rectum compared with FFIB. However, compared with FFIB, NCC DIR exhibited less regional deformation for the bladder and a tendency for increased local contraction of the rectum ROI. For the five‐fraction summations, ICE for the PTV V100%Rx is comparable for both algorithms (FFIB 0.8 ± 0.7%, NCC 0.7 ± 0.3%). For the bladder and rectum V70%Rx, ICE is greater for FFIB (1.8 ± 0.7% for bladder, 1.7 ± 0.6% for rectum) than for NCC (1.0 ± 0.3% for bladder, 1.0 ± 0.4% for rectum). Conclusions: The DVH overlay technique identified instances in which a DIR exhibits favorable invertibility, implying low ICE in a DIR‐based dose accumulation. Differences in the overlaid DVHs can also estimate dose accumulation errors attributable to ICE for given ROIs. [ABSTRACT FROM AUTHOR]

We discuss the stability of complex exponential frames in , . Specifically, we improve the -theorem and obtain explicit upper and lower bounds for some complex exponential frames perturbed along the real and imaginary axes, respectively. Two examples are given to show that the bounds are best possible. In addition, the growth of the entire functions of exponential type on the integer sequence is estimated.

Introduction: 4-Dimensional computed tomography (4DCT)-based ventilation imaging is a promising technique for evaluating pulmonary function, but lung elasticity and mechanics are usually not part of the ventilation image analysis. In this study we demonstrate a 4DCT-based imaging technique that can be used to calculate regional lung compliance changes after radiotherapy (RT).Methods: Six lung cancer patients were included in this study. Four of the patients had 4DCT images acquired pre-RT, 3 and 9 months post-RT. Ventilation and compliance were calculated from the deformable image registration (DIR) of 4DCTs, performed from the end-inhale to the end-exhale breathing phase. Regional compliance was defined as the ratio of volumetric variation and associated stress in each voxel, representing lung elasticity and computed using a FEM-based framework. Ventilation, compliance and CT density were calculated for all pre-RT and post-RT 4DCTs and evaluation metrics were computed.Results: Average CT density changes were 13.6 ± 11.4HU after 3 months and 26.9 ± 15.8HU after 9 months. Ventilation was reduced at 3 months, but improved at 9 months in regions with dose ≥ 35 Gy, encompassing about 10% of the lung volume; compliance was reduced at both time-points. Radiation dose ≥ 35 Gy caused major change in lung density and ventilation, which was higher than that previously reported in the literature (i.e. 24 Gy).Conclusion: Lung tissue response is diverse with respect to CT density, ventilation and compliance. Combination of ventilation and compliance with CT density could be beneficial for understanding radiation-induced lung damage and consequently could help develop improved treatment protocols for lung cancer patients. [ABSTRACT FROM AUTHOR]