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In this study, the imaging performance of electronic portal imaging devices (EPIDs) is evaluated, comparing measurements collected from EPID images captured at 115 cm, with a field size of 15 × 15 cm2, monitor units (MUs) in the range of 2 MU-100 MU and dose rates (DRs) of 200 MU/min, 400 MU/min and 600 MU/min, using a 6 MV LINAC system and the QC-3V image quality phantom. The analysis includes the normalized contrast transfer function (CTFnorm), the noise power spectrum (NPS) and the information capacity (IC), as well as the signal-to-noise frequency response (SNFR), which can be used as a comprehensive quality index. The results of our study are compared with previously published data captured at 100 cm under similar exposure conditions. They show similar CTF curves with different source-to-phantom distances, with the lowest values observed at specific MU and DR combinations. Moreover, NPS graphs are found to decrease with respect to spatial frequency. SNFR values also display a reduction with increasing spatial frequency. In addition, irradiation with the phantom placed closer to the EPID, 115 cm from the LINAC, yields better SNFR and IC performance characteristics, indicating better delineation of the organs closer to the EPID. The testing of EPID performance may potentially benefit from our results, which may lead to improvements in the quality of radiotherapy treatments. [ABSTRACT FROM AUTHOR]

Due to its inherent technical challenges, craniospinal irradiation (CSI) entails crucial considerations regarding plan complexity and robustness. The scope of this work was to establish and validate methods suitable for the evaluation of robustness, as well as for dose verification in CSI with VMAT. Five patients previously treated with CSI were retrospectively selected. For each patient, two technically different treatment plans were generated, based on the conventional (static overlap) and staggered (dynamic overlap) configuration. These techniques served as a benchmark to evaluate the potential of a metric proposed in this work, aimed at quantifying robustness, the Overlap Robustness Index (ORI). Furthermore, they were utilized to assess the suitability of two experimental methods relying on film dosimetry, as well as on Delta4 phantom for identifying sources of uncertainties in CSI applications. In accordance with the positional error simulation performed, the staggered approach yielded a statistically significant superior ORI value compared to the conventional one. Additionally, the strong correlation observed between the positional shift induced dose distribution changes and ORI results (Spearman's r = -0.941, p-value < 0.001) demonstrated the sensitivity of ORI in detecting areas of steep dose gradients within the overlapping regions that could potentially compromise the quality of treatment. Concerning dose verification, analysis in terms of dose profiles revealed a superior dosimetric accuracy for the staggered technique relative to conventional for both film and Delta4 measurements. Film-based gamma index results showed that staggered technique outperformed the conventional for the majority of passing criteria considered, with differences in passing rates up to 8.1%. The two treatment techniques however, exhibited equivalent dose delivery accuracy for the clinically relevant passing criteria when Delta4 was employed, with passing rate differences less than 0.6%. Findings of this study revealed that ORI is suitable for quantifying robustness in CSI with VMAT, while radiochromic films appeared to be the best candidate for CSI dose verification in this work. [ABSTRACT FROM AUTHOR]

To evaluate and compare the efficiency of orthodontic treatment and surgical uprighting of first and second mandibular molars. An electronic literature search in PubMed, Science Direct, Embase, Scopus, Web of Science, Cochrane Library, LILACS, and Google Scholar, as well as a hand search was conducted by two independent researchers to identify relevant articles up to January 2022. In addition, a manual search was done that included article reference lists, grey literature, and dissertations. The risk of bias of the included prospective and retrospective studies was assessed with the Risk Of Bias Tool In Non-randomized Studies of Interventions (ROBINS-I) assessment tool. A total of six nonrandomized clinical trials (non-RCT) evaluating the efficiency of mandibular molar orthodontic and/or surgical uprighting were included. The quality analysis showed certain defects of the Non-RCTs included and, according to the criteria used, the majority of the articles were judged to be of moderate quality. Based on the evidence, orthodontic and surgical uprighting appear to be effective treatment methods for mandibular molars. Surgical uprighting may be associated with more complications than orthodontic uprighting. However, the existing literature on the subject is limited, heterogeneous, and methodologically limited. Therefore, the outcomes should be interpreted carefully. [ABSTRACT FROM AUTHOR]

Simple Summary: Cell killing and tumor response in cancer patients depends not only on the absorbed radiation dose but also on the dose rate and delivery time. In this study, a biodosimetry assay based on the frequency of dicentrics chromosomes scored in peripheral blood lymphocytes from prostate cancer patients and PC3 human prostate cancer cell line was used to investigate the radiobiological impact of the relative prolonged dose delivery time and/or decreased dose rate met in advanced modulated radiotherapy techniques (VMAT and IMRT) compared to conventional non-modulated (3D-CRT) in prostate patient plan irradiations. The results showed a small but statistically significant decrease in the number of dicentrics following radiation with the modulated techniques, suggesting a corresponding decrease on the radiation dose efficiency. The biodosimetry assay could be used as an alternative to the laborious conventional clonogenic assay, while both lymphocytes and cancer cell line could effectively be used for estimation of the biological absorbed dose. While rapid technological advances in radiotherapy techniques have led to a more precise delivery of radiation dose and to a decreased risk of side effects, there is still a need to evaluate the efficacy of the new techniques estimating the biological dose and to investigate the radiobiological impact of the protracted radiotherapy treatment duration. The aim of this study is to compare, at a cytogenetic level, advanced radiotherapy techniques VMAT and IMRT with the conventional 3D-CRT, using biological dosimetry. A dicentric biodosimetry assay based on the frequency of dicentrics chromosomes scored in peripheral blood lymphocytes from prostate cancer patients and PC3 human prostate cancer cell line was used. For each patient blood sample and each subpopulation of the cultured cell line, three different irradiations were performed using the 3D-CRT, IMRT, and VMAT technique. The absorbed dose was estimated with the biodosimetry method based on the induced dicentric chromosomes. The results showed a statistically significant underestimation of the biological absorbed dose of ~6% for the IMRT and VMAT compared to 3D-CRT irradiations for peripheral blood lymphocytes, whereas IMRT and VMAT results were comparable without a statistically significant difference, although slightly lower values were observed for VMAT compared to IMRT irradiation. Similar results were obtained using the PC3 cell line. The observed biological dose underestimation could be associated with the relative decreased dose rate and increase irradiation time met in modulated techniques compared to the conventional 3D-CRT irradiations. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this study was to evaluate radiation dose reduction in coronary computerised tomography angiography (CCTA), using a commercially available iterative reconstruction (IR) algorithm as well as the behaviour of the image noise., Methods: A total cohort of 47 patients underwent CCTA examination on a 64-slice multi-detector CT. They were divided into four groups according to the time when the examination was performed (before or after the installation of iDose) and the acquisition protocol followed (prospective or retrospective electrocardiography-ECG gated). The images acquired with reduced dose settings were reconstructed using two levels (L4 and L6) of the iDose4 algorithm. Image noise was measured in all cases., Results: In retrospective acquisition, images acquired with a 46% lower radiation dose and reconstructed with iDose4 L6 provided noise comparable to that in the full-dose filtered back-projection images. For the prospective acquisition mode, a slight decrease (26%) in radiation dose resulted in noise improvement in low-dose images reconstructed with iDose4 L4 (16% noise removal) and L6 (30% noise removal)., Conclusions: The fact that image quality is improved while radiation exposure is reduced indicates that there is room for a further reduction in exposure settings. Additionally, the combination of iDose4 with prospective acquisition is able to significantly reduce the radiation dose associated with CCTA at values of about 2 mSv and even lower.