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PURPOSE In this study, we evaluate and compare single isocenter multiple target VMAT (SIMT) and Conformal Arc Informed VMAT (CAVMAT) radiosurgery's sensitivity to uncertainties in dosimetric leaf gap (DLG) and treatment delivery. CAVMAT is a novel planning technique that uses multiple target conformal arcs as the starting point for limited inverse VMAT optimization. METHODS All VMAT and CAVMAT plans were recalculated with DLG values of 0.4, 0.8, and 1.2 mm. DLG effect on V6Gy [cc], V12Gy [cc], and V16Gy [cc], and target dose was evaluated. Plans were delivered to a Delta4 (ScandiDos, Madison, WI) phantom and gamma analysis performed with varying criteria. Log file analysis was performed to evaluate MLC positional error. Sixteen targets were delivered to a SRS MapCHECK (Sun Nuclear Corp., Melbourne, FL) to evaluate VMAT and CAVMAT's dose difference (DD) as a function of DLG. RESULTS VMAT's average maximum and minimum target dose sensitivity to DLG was 9.08 ±3.50%/mm and 9.50 ± 3.30%/mm, compared to 3.20 ± 1.60%/mm and 4.72 ± 1.60%/mm for CAVMAT. For VMAT, V6Gy [cc], V12Gy [cc], and V16Gy [cc] sensitivity was 35.83 ± 9.50%/mm, 34.12 ± 6.60%/mm, and 39.23 ± 8.40%/mm. In comparison, CAVMAT's sensitivity was 23.19 ± 4.50%/mm, 22.45 ± 4.40%/mm, and 24.88 ± 4.90%/mm, respectively. Upon delivery to the Delta4 , CAVMAT offered superior dose agreement compared to VMAT. For a 1%/1 mm gamma analysis, VMAT and CAVMAT had a passing rate of 94.53 ± 4.40% and 99.28 ± 1.70%, respectively. CAVMAT was more robust to DLG variation, with the SRS MapCHECK plans yielding an absolute average DD sensitivity of 2.99 ± 1.30%/mm compared to 5.07 ± 1.10%/mm for VMAT. Log files demonstrated minimal differences in MLC positional error for both techniques. CONCLUSIONS CAVMAT remains robust to delivery uncertainties while offering a target dose sensitivity to DLG less than half that of VMAT, and 65% of that of VMAT for V6Gy [cc], V12Gy [cc], and V16Gy [cc]. The superior dose agreement and reduced sensitivity of CAVMAT to DLG uncertainties indicate promise as a robust alternative to VMAT for SIMT SRS.

Purpose To investigate the dosimetric impact of deep learning-based auto-segmentation of organs at risk (OARs) on nasopharyngeal and rectal cancer. Methods and materials Twenty patients, including ten nasopharyngeal carcinoma (NPC) patients and ten rectal cancer patients, who received radiotherapy in our department were enrolled in this study. Two deep learning-based auto-segmentation systems, including an in-house developed system (FD) and a commercial product (UIH), were used to generate two auto-segmented OARs sets (OAR_FD and OAR_UIH). Treatment plans based on auto-segmented OARs and following our clinical requirements were generated for each patient on each OARs sets (Plan_FD and Plan_UIH). Geometric metrics (Hausdorff distance (HD), mean distance to agreement (MDA), the Dice similarity coefficient (DICE) and the Jaccard index) were calculated for geometric evaluation. The dosimetric impact was evaluated by comparing Plan_FD and Plan_UIH to original clinically approved plans (Plan_Manual) with dose-volume metrics and 3D gamma analysis. Spearman’s correlation analysis was performed to investigate the correlation between dosimetric difference and geometric metrics. Results FD and UIH could provide similar geometric performance in parotids, temporal lobes, lens, and eyes (DICE, p > 0.05). OAR_FD had better geometric performance in the optic nerves, oral cavity, larynx, and femoral heads (DICE, p p p = 0.05). Only one significant correlation was found between the mean dose of the femoral head and its HD index (R = 0.4, p = 0.01), there is no OARs showed strong correlation between its dosimetric difference and all of four geometric metrics. Conclusions Deep learning-based OARs auto-segmentation for NPC and rectal cancer has a nonsignificant impact on most PTV and OARs dose-volume metrics. Correlations between the auto-segmentation geometric metric and dosimetric difference were not observed for most OARs.

The evaluation of the agreement between calculated and measured dose plays an essential role in the quality assurance procedures of intensity-modulated radiation therapy (IMRT). This study aimed to compare gamma analysis using portal dosimetry (PD), Epiqa, and 2D array detector for dose verification of radiotherapy treatment plans. Five field step-and-shoot IMRT plan was performed for 20 prostate IMRT patients using the dual-energy DHX linear accelerator (Varian Medical System, Palo Alto, Calif., USA). The treatment plans were created using Varian DHX Eclipse treatment planning system (TPS) version 15.1. All measurements were performed by aS500 EPID integrated into Varian DHX linear accelerator and 2D array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (1%/1 mm, 2%/2 mm, 3%/2 mm, and 3%/3 mm) for dose agreement and distance to agreement parameters. Statistical analyses were evaluated by using Mann–Whitney U test and Kruskal–Wallis test, and p-value of p < 0.01 was considered to be significant. The average pass rate for 20 IMRT plans was above 95 for all devices with 2%/2 mm, 3%/2 mm, and 3%/3 mm. The mean and standard deviation pass rates (γ ≤ 1) were found to be 99.80 ± 0.19, 99.35 ± 0.34, and 97.53 ± 0.71 for PD, Epiqa, and 2D array, respectively. All IMRT plans passed 2%/2 mm, 3%/2 mm, and 3%/3 mm gamma by more than 95 of three dosimetric systems. They are all in good agreement with the literature. All three devices are acceptable for quality control of IMRT. Due to the simplicity and fast evaluation process, PD can be preferred for quality control.

La gestión de los tratamientos en radioterapia se ve mejorada si existe la posibilidad de tratar a un paciente indistintamente en diferentes aceleradores sin necesidad de realizar cambios en el plan de tratamiento. Para que esto sea posible, las características dosimétricas y mecánicas de los aceleradores deben ser suficientemente semejantes. El objetivo de este trabajo es verificar que los aceleradores lineales de electrones Elekta Synergy e Infinity, ambos instalados en nuestro centro, con haces de fotones de 6 MV de energía, filtro aplanador y cabezal Agility, pueden considerarse gemelos. Para ello, se miden distintos parámetros dosimétricos en el acelerador Infinity para compararlos posteriormente con los obtenidos previamente en la puesta en marcha del acelerador Synergy. También se evalúa la calidad de varios tratamientos VMAT (Volumetric Modulated Arc Therapy) a través del análisis gamma (3 %/ 2 mm). La diferencia obtenida fue menor de un 2 % en todos los parámetros de calidad del haz y menor de un 3 % entre los análisis gamma de los tratamientos VMAT medidos en ambos aceleradores. Se confirma la posibilidad de utilizar el mismo modelado para ambos aceleradores lo que permite impartir un tratamiento en uno u otro indistintamente.

El presente artículo analiza el diseño y uso del espacio a través de la aplicación de análisis gamma en dos conventos coloniales femeninos, específicamente el de Santa Catalina de Arequipa en Perú, fundado en 1579, y el convento de Santa Catalina de Sena en Buenos Aires, Argentina, fundado en 1745. Lo anterior se desarrolla desde una perspectiva que considera que dichos conventos son expresiones materiales cuyo desarrollo reproduce relaciones sociales y de poder altamente complejas, cruzadas por las categorías de género y castas en el contexto de la sociedad patriarcal colonial y su desarrollo en el marco de la transformación de la sociedad Barroca colonial a la introducción del pensamiento ilustrado. Dichos espacios permitieron la configuración de dinámicas internas en donde ciertas religiosas alcanzaron un poder inédito para la época, manifestado en distintos soportes materiales como la arquitectura, lo que permite ver la relevancia en las dinámicas de uso, apropiación y transformación de los cenobios y las implicancias sociopolíticas de éstas a lo largo del Periodo Colonial.

We aimed to analyze the effects of printing parameters on characterization of three-dimensional (3D) printed bolus used in external beam radiotherapy. Two sets of measurements were performed to investigate the dosimetric and physical characterization of 3D-printed bolus at different printing parameters. In the first step, boluses were produced at different infill-percentages, infill-patterns and printing directions. Two-dimensional (2D) dose measurements were performed in Elekta Versa HD linear accelerator using 6 MV photon energy. Measured 2D dose maps for both printed and reference bolus materials were compared using the 2D gamma analysis method. Additionally, patient-specific bolus was produced with defined optimum printing parameters for anthropomorphic head and neck phantom. Then, point dose measurements were performed to evaluate the feasibility of printed bolus in clinical use. In the second step, physical measurements were carried out to evaluate the printing accuracy, the mean hounsfield unit (HU) value and the weight of 3D-printed boluses. According to our measurement, infill-percentage, infill-pattern and printing direction significantly changed the dosimetric and physical properties of the 3D-printed bolus independently. Maximum gamma passing rate at 1.5 and 5 cm depths were found as 93.8% and 98.8%, respectively, for 60% infill-percentage, sunglass fill infill-pattern and horizontal printing direction. The printing accuracy of the products was within 0.4 mm. Dosimetric and physical properties of the printed bolus material changed significantly with the selected printing parameters. Therefore, it is important to note that each combination of these printing parameters that will be used in the production of patient-specific bolus should be investigated separately.

Delivery quality assurance (DQA) is the process of establishing a treatment plan and verifying that the pre-treatment dose is delivered without any problems through a simulation. If the result does not meet certain criteria, the dose delivered to the patient is judged to be inaccurate, and the measurement or the treatment plan should be reconsidered. Therefore, it is important to analyze the plan parameters that influence the DQA outcome. The plan parameters have been studied for LINAC-based intensity-modulated radiation therapy and the Tomo helical method but not for the Tomo direct (TD) method. In this study, we perform this investigation using the TD method. A Radixcat X9 machine was used to collect data. Furthermore, in the TD method, we set the passing rate for each gamma analysis criterion as 2%/2 mm and 3%/3 mm. Next, the plan parameters influencing the DQA passing rate were confirmed by Pearson’s correlation analysis and regression analysis. Based on the gamma analysis, the mean passing rates of 2%/2 mm and 3%/3 mm were 97.9299 and 99.8472, respectively. The plan parameters influencing the DQA passing rate during the Pearson correlation analysis were IECZ (2%/2 mm: p = 0.008), duration (2%/2 mm: p = 0.002), and planning target volume (2%/2 mm: p = 0.030 and 3%/3 mm: p = 0.034). Based on these results, a regression analysis was performed. As a result of the regression analysis, duration (2%/2 mm: p = 0.047) was identified as the most significant plan parameter for the DQA passing rate. However, statistically for the gamma analysis criterion of 3%/3 mm, there were no significant plan parameters. As the beta of the duration has a negative relationship with the passing rate, reducing the duration improves the passing rate. When confirming the passing rate for each group in a duration of 60 s, it was confirmed that the passing rate was high if it was set to less than 240 s. So, we recommend setting the duration to 240 s or less.

The accuracy of radiotherapy is the subject of continuous discussion, and dosimetry methods, particularly in dynamic techniques, are being developed. At the same time, many oncology centers develop quality procedures, including pretreatment and online dose verification and proper patient tracking methods. This work aims to present the possibility of using portal dosimetry in the assessment of radiotherapy repeatability. The analysis was conducted on 74 cases treated with dynamic techniques. Transit dosimetry was made for each collision‐free radiation beam. It allowed the comparison of summary fluence maps, obtained for fractions with the corresponding summary maps from all other treatment fractions. For evaluation of the compatibility in the fluence map pairs (6798), the gamma coefficient was calculated. The results were considered in four groups, depending on the used radiotherapy technique: stereotactic fractionated radiotherapy, breath‐hold, free‐breathing, and conventionally fractionated other cases. The chi2 or Fisher's exact test was made depending on the size of the analyzed set and also Mann–Whitney U‐test was used to compare treatment repeatability of different techniques. The aim was to test whether the null hypothesis of error‐free therapy was met. The patient is treated repeatedly if the P‐value in all the fluence maps sets is higher than the level of 0.01. The best compatibility between treatment fractions was obtained for the stereotactic technique. The technique with breath‐holding gave the lowest percentage of compliance of the analyzed fluence pairs. The results indicate that the repeatability of the treatment is associated with the radiotherapy technique. Treated volume location is also an essential factor found in the evaluation of treatment accuracy. The EPID device is a useful tool in assessing the repeatability of radiotherapy. The proposed method of fluence maps comparison also allows us to assess in which therapeutic session the patient was treated differently from the other fractions.

Purpose In order to reduce heart dose, DIBH has become a common practice in left‐sided whole breast irradiation. This technique involves a significant strain on patients due to the breath‐hold requirements. We hereby investigate the dosimetric and delivery feasibility of using flattening filter free (FFF) energies with electronic tissue compensation (ECOMP) planning technique to reduce the required breath‐hold lengths and increase patient compatibility. Methods Fifteen left‐sided, postlumpectomy patients previously receiving DIBH whole‐breast radiotherapy (266cGy x 16fx) were retrospectively planned using ECOMP for both 6X and 6X‐FFF. A dosimetric comparison was made between the two plans for each patient using various dosimetric constraints. Delivery feasibility was analyzed by recalculating the 6X ECOMP plan with 6X‐FFF without replanning (6X‐FFF QA) and delivering both plans for a one‐to‐one comparison using Gamma analysis. Beam‐on times for the 6X and 6X‐FFF plans were measured. For all tests, Wilcoxon signed‐rank test was used with P 95% passing). Conclusion ECOMP planning with FFF was found feasible for left‐sided breast patients with DIBH. Plan quality is comparable, if not better, than plans using flattened beams. FFF ECOMP could significantly reduce beam‐on time and required breath‐hold lengths thereby increasing patient compatibility for this treatment while offering satisfactory plan quality and delivery accuracy.

Purpose This work presents a novel method of visualising the results of patient-specific quality assurance (QA) for modulated radiotherapy treatment plans, using a three-dimensional distribution of gamma pass rates, referred to as the “gamma surface”. The method was developed to aid in comparing borderline and failing QA plans, and to better compare patient-specific QA results between departments. Methods Gamma surface plots were created for a representative sample of situations encountered during patient-specific QA. To produce a gamma surface plot, for each QA result, gamma pass rates were plotted as a heat map, with dose difference on one axis and distance-to-agreement on the other. This involved the calculation of 100 × 100 gamma pass rates over a dose difference and distance-to-agreement grid. As examples, five 220 × 680 arrays of dose points from radiotherapy treatment plans were compared against measurement data consisting of 21 × 66 arrays of dose points spaced 10 mm apart. Results The gamma surface plots facilitated the rapid evaluation of criteria combinations for each plan, clearly highlighting the difference between plans that are modelled and delivered well, and those that are not. Large scale features were also evident in each surface, hinting at potential over-modulation, systematic dose errors, and small or large scale areas of disagreement in the distributions. Conclusions Gamma surface plots are a useful tool for investigating QA failures and borderline results, and have the capacity to grant insights into treatment plan QA performance that may otherwise be missed.

Introduction The purpose of the study was to compare the results of gamma value based film analysis according to the used type of self-developer film and software product. Material and methods The films were irradiated with different treatment techniques such as 3D conformal and intensity modulated radiotherapy with static and rotational delivery. Stereotactic plans with conformal and intensity modulated arc techniques, using coplanar and non-coplanar beam setup were also evaluated. The data of irradiated film were compared with the planned planar dose distribution exported from the treatment planning system. Three film analysis software programs were evaluated: PTW Mephysto (PTW), FilmQA Pro (FQP) and radiohromic.com(RC). Both EBT2 and EBT3 types of films were examined. The comparisons of dose distributions were performed with gamma analysis using 10% cut-off level. Results The results of the gamma analysis for larger fields were between 78.3% and 98.3%, 75.7% and 100%, 80.2% and 98.8% with PTW, FQP and RC, respectively. The results of evaluation in case of stereotactic measurements were 76.8%–99.2% for PTW, 95.7%–100% for FQP and 91.2%–99.9% for RC. Conclusions All the three software programs are suitable for calibrating and evaluating films, performing gamma analysis, and can be used for patient specific quality assurance measurements. There is no direct connection between gamma passing rate and absolute accuracy or software quality, it is just a feature of the software. The interpretation of own results has to be defined on an institutional level according to given workflow and preliminary results.

In situ indoor gamma dose rate measurements were held in 79 dwellings by NaI(Tl) scintillation probe connected portable dose rate meter. For the building materials and impurities (nodules), spectrometric gamma analysis was applied by a high-resolution HpGe detector. For Ahmetçe and Nusratlı villages in Ayvacik/Çanakkale (Turkey), the measured in situ indoor gamma dose rates and related indoor annual effective dose equivalents (AEDEin) were 3 and 3.3 times, and indoor excess lifetime cancer risks (ELCRin) were 4.25 and 4.68 times higher than those of the world averages, respectively. The used local rocks were mostly ignimbrite and dacitic–rhyolitic tuffaceous (Arıklı tuff), and wall plasters were made of local soil. The highest in situ indoor gamma dose rates of the region belonged to Nusratlı village due to the intense impurities (nodules) and hydrothermal alterations in Arıklı tuff. Spectrometric gamma results revealed that 40K has an important effect on the indoor gamma doses.

Purpose To analyse the impact of different optimization strategies on the compatibility between planned and delivered doses during radiotherapy of cervical cancer. Material/methods Four treatment plans differing in optimisation strategies were prepared for ten cervical cancer cases. These were: volumetric modulated arc therapy with (_OPT) and without optimization of the doses in the bone marrow and for two sets of margins applied to the clinical target volume that arose from image guidance based on the bones (IG(B)) and soft tissues (IG(ST)). The plans were subjected to dosimetric verification by using the ArcCHECK system and 3DVH software. The planned dose distributions were compared with the corresponding measured dose distributions in the light of complexity of the plans and its deliverability. Results The clinically significant impact of the plans complexity on their deliverability is visible only for the gamma passing rates analysis performed in a local mode and directly in the organs. While more general analyses show statistically significant differences, the clinical relevance of them has not been confirmed. The analysis showed that IG(ST)_OPT and IG(B)_OPT significantly differ from IG(ST) and IG(B). The clinical acceptance of IG(ST)_OPT obtained for hard combinations of gamma acceptance criteria (2%/2 mm) confirm its satisfactory deliverability. In turn, for IG(B)_OPT in the case of the rectum, the combination of 2%/2 mm did not meet the criteria of acceptance. Conclusion Despite the complexity of the IG(ST)_OPT, the results of analysis confirm the acceptance of its deliverability when 2%/2 mm gamma acceptance criteria are used during the analysis.

Purpose We performed three-dimensional (3D) dose reconstruction-based pretreatment verification to evaluate gamma analysis acceptance criteria in volumetric modulated arc therapy (VMAT) for prostate cancer. Materials and methods Pretreatment verification for 28 VMAT plans for prostate cancer was performed using the COMPASS system with a dolphin detector. The 3D reconstructed dose distribution of the treatment planning system calculation (TC) was compared with that of COMPASS independent calculation (CC) and COMPASS reconstruction from the dolphin detector measurement (CR). Gamma results (gamma failure rate and average gamma value [GFR and γAvg]) and dose-volume histogram (DVH) deviations, 98%, 2% and mean dose-volume difference (DD98%, DD2% and DDmean), were evaluated. Gamma analyses were performed with two acceptance criteria, 2%/2 mm and 3%/3 mm. Results The GFR in 2%/2 mm criteria were less than 8%, and those in 3%/3 mm criteria were less than 1% for all structures in comparisons between TC, CC, and CR. In the comparison between TC and CR, GFR and γAvg in 2%/2 mm criteria were significantly higher than those in 3%/3 mm criteria. The DVH deviations were within 2%, except for DDmean (%) for rectum and bladder. Conclusions The 3%/3 mm criteria were not strict enough to identify any discrepancies between planned and measured doses, and DVH deviations were less than 2% in most parameters. Therefore, gamma criteria of 2%/2 mm and DVH related parameters could be a useful tool for pretreatment verification for VMAT in prostate cancer.

In this study, the delivery quality assurance (DQA) results of commercially available dosimetric systems (ionization chamber and EBT film, MapCHECK, ArcCHECK, and dosimetry check (DC) software) for helical tomotherapy (HT) were compared, and the feasibility of performing pretreatment using MapCHECK, ArcCHECK, and DC for HT, instead of ionization chambers and EBT films, was assessed. Sixty-five HT-treated patients were considered. Point dose differences, dose profiles, and gamma passing rates were used to evaluate the agreement between the calculated and the measured data, and the outcomes of the four DQA devices were compared in various clinical cases. The calculated and the measured point doses were within ±5% of each other. In terms of the root-mean-square error (RMSE), the point dose differences were within 2.9 for the four tested devices in all of the studied cases. Gamma analysis was performed based on the 3%/3 mm and 2%/2 mm passing rate criteria. In terms of the average RMSE, the gamma passing rates of the four tested DQA devices were within 2.85 (3%/3 mm) and 7.30 (2%/2 mm). These DQA systems could be used interchangeably for routine DQA pretreatment in HT cases.

Aim:The aim of this work was to study the acceptability of plans prepared for prostate patients treated by volumetric modulated arc therapy (VMAT) with the vision to evaluate the quality of plans and test pre-treatment quality assurance (QA).Material methods:VMAT plans of 35 patients, planned on the Eclipse Treatment Planning System (Aria 15), were included in the study. Plan acceptability was checked using statistical analysis, which includes homogeneity index, radical and median homogeneity index, coverage and uniformity index. Dose–volume histograms (DVH) of the plans were also studied to check prescribed dose (PD), Dmax, Dmin, D5 and D95. Portal dosimetry was also done by gamma analysis using 3%/3 mm criterion. SD and mean SD error were also calculated and analysed.Results:Statistical analysis showed a mean HI of 1·054, coverage 0·959, UI 1·055, mDHI 0·962 and rDHI 0·866. SD of HI, coverage, UI, mDHI and rDHI was 0·019, 0·019, 0·014, 0·013 and 0·030, respectively. From the DVHs, mean of D5, D95, Dmin and Dmax was calculated at 6,252·9, 5,757·4, 6,413·3 and 5,657·7 cGy, respectively, with a prescribed dose of 6,000 cGy. According to gamma analysis, area gamma < 1 was 99·12% with a tolerance limit of 95%, maximum gamma was 1·466 with a tolerance limit of 3·5, average gamma was 0·388 with a tolerance limit of 0·5, area gamma > 1·2 was 0·242% with a tolerance limit of 0·5%, maximum dose difference was 0·6 with a tolerance limit of 1·0 and average dose difference was 0·029 with a tolerance limit of 0·2.Conclusion:All three computations showed the results to be within acceptable limits. VMAT possesses a unique feature of delivering the whole treatment with only two rotations of the gantry. VMAT has an improved efficiency of delivery for equivalent dosimetric quality.

Background/aim The Purpose of this study was to develop a Monte Carlo (MC) model for the Agility multileaf collimator (MLC) mounted and to validate its accuracy. Materials and methods To describe the Agility MLC in the BEAMnrc MC code, an existing component module code was modified to include its characteristics. The leaf characterization of the MC model was validated by comparing the calculated interleaf transmission and tongue-and-groove effect with EBT2 film and diode measurements and IMRT and VMAT calculations with film measurements. Results Agreement between mean calculated and measured leaf transmissions was within 0.1%. The discrepancy between MC calculation and measurement in a static irregular field was less than 2%/2 mm. Gamma analysis of the comparison of MC and EBT2 film measurements in IMRT and VMAT fields yielded pass rates of 99.1% and 99.5% with 3%/3 mm criteria, respectively. Conclusion Our findings demonstrate the accuracy of the MC model using an adapted BEAMnrc component module for the Agility MLC.

This work proposes a new method for pseudo-3D verification of intensity-modulated radiation therapy (IMRT) dose distributions. Unlike commercial solutions, it uses measured doses only for gamma evaluation. Its resolution is far better than with electronic detectors within the measured plane and comparable in other directions. It is readily available at clinics because it uses existing resources—a slab phantom and EBT3 films. The method was tested on six IMRT clinical cases. An in-house code for 2D and pseudo-3D gamma analysis was written in MATLAB and compared to OmniPro I’mRT.

In radiotherapy, radiochromic films can be used for verification of delivery of dose distributions calculated by treatment planning systems. The main objective of this work was to compare three different techniques for evaluation of dose distributions for prostate cancer treatment plans using radiochromic EBT3 films. These techniques are: red channel evaluation taking into account only a response of irradiated film (R), red channel evaluation taking into account a response of unirradiated and irradiated film (Rcor) and multichannel evaluation in FilmQA software (RGB). Also comparison between film and MatriXX measurement was performed. Comparison showed that gamma analysis passing rates strongly depend on evaluation technique and on a model of scanner for digitizing films. The highest gamma passing rates were obtained with red channel evaluation taking into account a response of unirradiated and irradiated film using Epson V750 scanner (Rcor) and multichannel evaluation in FilmQA using Epson 11000XL scanner.

Purpose The aim of this review article is to provide a useful reference for dose comparison techniques within the frame of treatment plan verification. Each technique is presented with a general description given along with advantages and disadvantage and the rationale for its development. Methods The review was conducted in PubMed from 1993 to 2019 including articles referring to the methodology of dose comparison for treatment plan verification. Results The search identified thirty-one dose comparison methods that were categorized according to the number of physical parameters that take into account for dose comparison. Conclusions Among the available methods for the comparison of two dose distributions, the γ-analysis (gamma analysis) has been widely adopted as the gold standard in verification procedures. However, due to various intrinsic limitations of gamma index, the development of a better metric taking into account both statistical and in clinical parameters is required.

Objective Adaptive radiation therapy (ART) is an integral part of MR-guided RT (MRgRT), requiring a new RT plan for each treatment fraction and resulting in a significant increase in patient-specific quality assurance (PSQA). This study investigates the possibility of using treatment log-file for automated PSQA. Method All treatment plans were delivered in 1.5T Unity MR-Linac (Elekta). A Unity compatible version of LinacView (Standard Imaging) was commissioned to automatically monitor and analyze the log-files. A total of 220 fields were delivered and measured by ArcCheck® -MR (Sun Nuclear) and LinacView. Thirty incorrectly matched fields were also delivered to check for error detection sensitivity. The gamma analysis, γ, with 3%, 3 mm criteria was used in both ArcCheck® -MR and LinacView. Additionally, the gantry angle, jaws, and multileaf collimators (MLC) positions reported in the log-file were compared with plan positions using TG-142 criteria. Result The γ (3%, 3 mm) for the 190 plans were found to be between the range of 72.5%-100.0% and 95.4%-100.0% for ArcCheck® -MR and LinacVeiw, respectively. All the delivered gantry angle and jaws were found to be within 0.2° and 2 mm. MLCs that were outside the guard leaves or under the diaphragms were found to have more than 1.0 mm discrepancy. This was attributed to the linac internal override for these MLCs and had no dosimetric impact. Excluding these discrepancies, all MLC positions were found to be within 1.0 mm. The γ (3%, 3 mm) for the 30 incorrectly matched fields were found to be 3.9%-84.8% and 0.1%-64.4% for ArcCheck® -MR and LinacVeiw, respectively. Conclusion Significant ranked correlation demonstrates the automated log-file analysis can be used for PSQA and expedite the ART workflow. Ongoing PSQA will be compared with log-file analysis to investigate the longer term reproducibility and correlation.

Purpose The objective of this work is to explore a methodology to enable plan transfers from Standard MLC (STD) to High Definition MLC (HD) Varian units without replanning. Using “Plan Transformation”, we aim to utilize full departmental capacity to disperse patients from STD Varian units to HD units, when the former goes down for repair. Methods Our centre is equipped with four STD and two HD MLC Varian Truebeam units. Plan transformation is used to transfer patients from STD to HD units when needed. Static or manually segmented fields with Y jaws ≤ 21.6 cm are eligible for plan transformation. The MLC pattern for each field is exported out of Eclipse. An in-house program based on C# is used to convert those patterns from STD to HD. STD and HD MLCs are different in design but dosimetrically comparable for these type of plans. Still to avoid extra uncertainty, transformed plans are recalculated in Eclipse to enable the user to assess the quality of the process. Results On a given day, more than 25% of appointments on STD units were eligible for transformation. The majority of eligible plans were breast tangent and boost. The delivery and safety of plan transformation was examined directly on a Varian Truebeam linac. A gamma analysis comparison between measured and calculated transformed plans yields a pass-rate of 100% for 3%/3mm, identical to non-transformed plans. Conclusion Plan transformation is feasible and saves time for planners as it takes less than a quarter the time required for a replan.

The possible application of Pulsed Fast/Thermal Neutron Analysis (PFTNA) for determining the carbon-to-nitrogen ratio (C/N) of compost will be discussed. This analysis method has several ad...

A system for analyzing soil content of a field includes a data acquisition unit configured to detect gamma spectra of each of a plurality of soil samples, wherein a surface area of the field is divided into a plurality of portions and the plurality of soil samples comprises at least one soil sample from each of the plurality of portions, a navigation unit configured to detect geographic coordinates of each of the plurality of soil samples, a data analysis unit configured to associate the detected gamma spectra of each of the plurality of soil samples with the geographic coordinates of the soil sample and determine a weight percent of at least one element within each of the soil samples based on the detected gamma spectra, and an element content map unit configured to generate a map indicating concentration of the at least one element within the soil of the field.

Introduction Employing routine dosimetry protocols for intraoperative electron beam needs further refinements to obtain reliable results. In this regard, the performance of some cylindrical and parallel plate ion chambers for both relative and absolute dosimetry of intraoperative electron beam has been evaluated. Materials and methods Four different ion chambers including Semiflex and PinPoint cylindrical chambers as well as Advanced Markus and Roos parallel plate ones were employed for PDD measurement and dose rate determination in reference condition of the electron beam produced by LIAC intraoperative accelerator. The results of PDD measurements were compared with those of Gafchromic EBT2 film. Specific recommendations were followed to determine the chamber correction factors including ks and k Q,Q 0 for absolute dosimetry in intraoperative reference condition. Results There was good agreement between PDDs measured by employed chambers and EBT2 film at all nominal energies. Nevertheless, Advanced Markus chamber had the best performance based on the gamma analysis results. Obtained k Q,Q 0 and ks for studied ion chambers largely differed from expected values by TRS-398 protocol. The difference of measured dose rates at 12 MeV energy by investigated chambers was less than 1.1% and Advanced Markus had the best accordance with pre-set dose rate by manufacture. Conclusion Results showed that ignoring the specific recommended procedures in determining the chamber correction factors causes the overestimation of the measured dose. Therefore, dedicated dosimetry protocol should be developed for high dose per pulse intraoperative electron dosimetry including all of the updated correction factors and deviations from routine ionometric electron dosimetry formalisms.

The capability of error detection of patient-specific QA tools plays an important role in verifying MLC motion accuracy. The goal of this study was to investigate the capability in error detection of portal dosimetry, MapCHECK2 and MatriXX QA tools in IMRT plans. The 9 fields IMRT for 4 head and neck plans and 7 fields IMRT for 4 prostate plans were selected for the error detection of QA devices. The measurements were undertaken for the original plan and the modified plans, where the known errors were introduced for increasing and decreasing of prescribed dose (±2%, ±4% and ±6%) and position shifted in X-axis and Y-axis (±1, ±2, ±3 and ±5 mm). After measurement, the results were compared between calculated and measured values using gamma analysis at 3%/3 mm criteria. The average gamma pass for no errors introduced in head and neck plans was 96.9%, 98.6%, and 98.8%, while prostate plans presented 99.4%, 99.0%, and 99.7%, for portal dosimetry, MapCHECK2 and MatriXX system, respectively. In head and neck plan, the shifted error detections were 1 mm for portal dosimetry, 2 mm for MapCHECK2, and 3 mm for MatriXX system. In prostate plan, the shifted error detections were 2 mm for portal dosimetry, 3 mm for MapCHECK2, and 5 mm for MatriXX system. For the dose error detection, the portal dosimetry system could detect at 2% dose deviation in head and neck and 4% in prostate plans, while other two devices could detect at 4% dose deviation in both head and neck and prostate plans. Portal dosimetry shows slightly more capability to detect the error compared with MapCHECK2 and MatriXX system, especially in the complicated plan. It may be due to higher resolution of the detector; however, all three-detector types can detect various errors and can be used for patient-specific IMRT QA.

Background and purposeThis study reported the justification and selection of acceptable γ criteria with respect to low (6 MV) and high (15 MV) photon beams for intensity-modulated radiation therapy quality assurance (IMRT QA) using the Gafchromic external beam therapy 3 (EBT3) film.Materials and methodsFive-field step-and-shoot IMRT was used to treat 16 brain IMRT patients using the dual-energy DHX-S linear accelerator (Varian Medical System, Palo Alto, CA, USA). Dose comparisons between computed values of the treatment planning system (TPS) and Gafchromic EBT3 film were evaluated based on γ analysis using the Film QA Pro software. The dose distribution was analysed with gamma area histograms (GAHs) generated using different γ criteria (3%/2 mm, 3%/3 mm and 5%/3 mm) for the 6 and 15 MV photon beams, to optimise the best distance-to-agreement (DTA) criteria with respect to the beam energy.ResultsFrom the comparison between the dose distributions acquired from the TPS and EBT3 film, a DTA criterion of 3%/2 mm showed less dose differences (DDs) with passing rates up to 93% for the 6 MV photon beams, while for the 15 MV a relaxed DTA criterion of 5%/3 mm was consistent with the DD acceptability criteria with a 95% passing rate.ConclusionsOur results suggested that high-energy photon beams required relaxed DTA criteria for the brain IMRT QA, while low-energy photon beams showed better results even with tight DTA criteria.

Purpose To investigate intrinsic sensitivity of an electronic portal imaging device (EPID) and the ArcCHECK detector and to use this in assessing their performance in detecting delivery variations for lung SBRT VMAT. The effect of detector spatial resolution and dose matrix interpolation on the gamma pass rate was also considered. Materials and methods Fifteen patients’ lung SBRT VMAT plans were used. Delivery variations (errors) were introduced by modifying collimator angles, multi‐leaf collimator (MLC) field sizes and MLC field shifts by ±5, ±2, and ±1 degrees or mm (investigating 103 plans in total). EPID and ArcCHECK measured signals with introduced variations were compared to measured signals without variations (baseline), using OmniPro‐I'mRT software and gamma criteria of 3%/3 mm, 2%/2 mm, 2%/1 mm, and 1%/1 mm, to test each system's basic performance. The measurement sampling resolution for each was also changed to 1 mm and results compared to those with the default detector system resolution. Results Intrinsic detector sensitivity analysis, that is, comparing measurement to baseline measurement, rather than measurement to plan, demonstrated the intrinsic constraints of each detector and indicated the limiting performance that users might expect. Changes in the gamma pass rates for ArcCHECK, for a given introduced error, were affected only by dose difference (DD %) criteria. However, the EPID showed only slight changes when changing DD%, but greater effects when changing distance‐to‐agreement criteria. This is pertinent for lung SBRT where the minimum dose to the target will drop dramatically with geometric errors. Detector resolution and dose matrix interpolation have an impact on the gamma results for these SBRT plans and can lead to false positives or negatives in error detection if not understood. Conclusion The intrinsic sensitivity approach may help in the selection of more meaningful gamma criteria and the choice of optimal QA device for site‐specific dose verification.

Clinical implementation of intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) requires the ability to verify complex radiation dose delivery. The use of new dosimetry tools and procedures for clinical quality assurance (QA) practice is becoming increasingly important, especially when taking into account the necessity of reliable but also time-sparing QA protocols. An effective IMRT QA protocol should verify the accuracy of complex calculated absorbed dose distributions to prevent clinically significant errors that may compromise the treatment safety. Although many institutions have developed dosimetry modalities for patient specific QA measurements in which typically the evaluated (e.g. calculated) absorbed dose distribution is compared against the reference (e.g. measured) distribution, most of them commonly use gamma (γ) analysis as a comparison metric. The efficacy of the IMRT/VMAT technique asserts the necessity of defining reliable criteria to facilitate the dose distribution comparison process. In a comparison of a given reference point in a dose distribution and any one of the evaluated dose distribution points, a generalized Euclidean distance may be defined in a k+1 dimensional hyperspace, where k+1 refers to the spatial coordinates plus the dose. The difference between the evaluated and the reference absorbed dose, and the spatial differences are normalized by the maximum the dose and spatial differences criteria in the gamma index expression, respectively. Assuming that the evaluated dose distribution is available with high spatial resolution, the gamma evaluation index is then given by the minimum value of the generalized distance, searching across all available evaluation points. The γ analysis has nowadays being accepted as an essential tool for the comparison of two absorbed dose distributions, the reference and evaluated distribution. The comparison criteria and failure rate tolerance levels have hitherto normally been based on empirical evidence, rather than the actual uncertainties of absorbed dose measurements and detector positioning. For a proper determination of the acceptable failure rate, a statistical evaluation should be carried out. The goal of this work was to investigate the gamma analysis method by using a statistical approach to evaluate the relation between the acceptance criteria and the actual uncertainties of the dose measurement. For that purpose, in the initial stage, the gamma analysis program code for 1D and 2D dose distribution comparisons were developed, verified, and validated. Measured absorbed dose values in cases of 1D and 2D absorbed dose distributions were simulated by assuming that the calculated value at the measurement point represented the expectation value, taking the calculated absorbed dose at a randomly displaced position, and by adding a random measurement noise. The detector displacement and the measurement noise were drawn from normal distributions with standard deviations in the range of interest. Finally, the nearest calculation point was determined according to the gamma evaluation procedure and the smallest gamma index value was calculated. The acceptance criteria, dose difference, and distance-to-agreement criteria were set equal to the standard deviations of the associated uncertainties. By comparison between absorbed dose calculations and simulated measurements for clinical cases in 1D and 2D, it has been found that the resulting squared gamma index distribution follows a chi-squared (χ^2) distribution with one degree of freedom. This result can be used to verify the statistical significance of measured deviations, and to determine proper failure rate tolerance levels in clinical radiotherapy quality assurance. The latter simulation results valid only for a single measurement were extended from single detector system to an entire array of detectors, mimicking thus a measurement conditions for verification of calculated absorbed dose distribution. Simulated dose measurements that were derived from a set of clinical head-and-neck IMRT dose distributions, calculated in a uniform phantom and evaluated by the gamma index analysis, clearly showed that the probability of having a gamma value above unity is not spatially uniform. The gamma evaluation produced relatively more false positives in regions with larger values of the second-order derivative pointing to the feature that the statistical significance of the gamma failure criterion (i.e., γ >1) is not uniquely related to a given set of spatial and dose tolerance values. This shortcoming appears (or strongly indicates) to be responsible for the limited ability of the gamma evaluation method to detect errors in clinically relevant situations. Uvod i motivacija : Nakon razdoblja intenzivne primjene trodimenzijske (3D) konformalne radioterapije (engl. conformal radiotherapy, 3DCRT), pojavom radioterapije moduliranog intenziteta (jakosti) i volumno-modulirane lučne radioterapije (engl. intensity modulated radiotherapy, IMRT, volumetric modulated arc radiotherapy, VMAT), koje se provode linearnim akceleratorima opremljenim višelistićnim kolimatorom (engl. multileaf collimator, MLC) čime se dobivaju složeni oblici raspodjela apsorbirane doze, ukazala se potreba za boljim razumijevanjem dozimetrijskih alata i njihovih ograničenja pri mjerenju i usporedbi tih raspodjela kako bi se osigurala sigurna i točna provedba naprednih postupka radioterapije. Osiguranje kvalitete (eng. quality assurance, QA) terapije zračenjem moduliranog intenziteta od presudnog je značaja i olakšava njegovu uspješnu i pouzdanu kliničku provedbu. Program osiguranja kvalitete uključuje nekoliko dozimetrijskih postupaka koji se provode prije radioterapijskog liječenja pacijenta. Provjerom točnosti izračuna doze, prijenosa plana zračenja s računalnog sustava za planiranje (engl. treatment planning system, TPS) na linearni akcelerator i isporuke doze, osiguranjem kvalitete za pojedinačne pacijente osigurava se točna isporuka propisane doze. IMRT postupak uključuje predaju apsorbirane doze koja dovodi do velikog gradijenta doze u blizini kritičnih struktura. Moduliranje intenziteta snopa fotona omogućava da se zračenje može usmjeriti izravno kroz kritične organe i strukture, a postupak optimizacije modulacije snopa zračenja ograničava dozu na kritične organe. Takva složenost raspodjela doza znači da se osiguranje kvalitete kod IMRT-a mora više usredotočiti na kumulativnu isporučenu dozu kao i na provjeru doza na više mjesta, a ne na osiguranje kvalitete pojedinih segmenata snopa. Druga važna značajka je podudaranje gradijenta doze s ciljnim volumenom i razmještajem okolnog normalnog tkiva. Kriteriji prihvatljivosti rezultata osiguranja kvalitete radioterapije moduliranog intenziteta donekle se razlikuju u različitim ustanovama što je posljedica različitih uređaja za zračenje, linearnih akceleratora, algoritama računalnih sustava za planiranja i njihove praktične primjene, kao i mjerne opreme koja se koristi u provođenju programa osiguranja kvalitete. Postoje različiti izvori koji mogu uzrokovati pogreške kako u planiranju IMRT/VMAT raspodjela apsorbirane doze, tako i u njenoj isporuci. To su prije svih, pogreške vezane uz računalni sustav za planiranje, a najvažniji čimbenici koji mogu dovesti do pogrešnog planiranja postupka zračenja su načini na koji se modelira kraj listića kolimatora kao i učinak jezička i žlijeba (engl. tongue and groove), transmisija kolimatora i višelističnih kolimatora, izlazni faktori malih polja zračenja i izvan osni profili doza. Izbor veličine matrice za izračun doze također može uzrokovati pogreške i artefakte, kao i korištenje modela za popravke heterogenosti sredstva. Pored toga, pogrešku može uzrokovati i ograničenje mjernog sustava koji se koristi u provođenju programa osiguranja kvalitete, kao što je rezolucija matričnog detektora s velikom brojem detektora. Iako ovaj detektor može istovremeno provjeravati doze na više prostornih mjesta, njegov relativno velik razmak detektora ograničava ga u provjeri detaljnih struktura raspodjele doze. Iako su razne ustanove razvile vlastite modalitete i koriste različite, komercijalne, mjerne sustave, metoda gama analize postala je standard u ocjeni slaganja referentne raspodjele doze (npr. mjerene) i procijenjene (npr. izračunate) u za pacijenta specifičnom postupku osiguranja kvalitete u radioterapiji moduliranog intenziteta i široko je dostupna za uporabu u komercijalnim paketima programske podrške. Konkretno, gotovo sveprisutni kriteriji tolerancije (dopustivosti) razlike u dozi (engl. dose difference, DD) i udaljenosti-do-slaganja (engl. distance-to-agreement, DTA) od 3%/3 mm, prag niskih doza od 10%, globalno normiranje doze i prihvatljiva stopa neuspjeha (engl. failure rate) od 5-10%, koriste se gotovo sa svim novim uređajima i tehnikama zračenja, uz pretpostavku da je visoki postotak gama prolaznosti pokazatelj dobrog podudaranja između mjerenih i izračunatih raspodjela apsorbirane doze. Zbog nepouzdanosti mjerenja apsorbirane doze i položaja detektora, neke točke u gama analizi neće proći kriterij prihvatljivosti, čak i ako ne postoji stvarno odstupanje, a određeni udio točaka koje ne zadovoljavaju kriterij se mora dopustiti. Iako su se kriteriji prihvatljivosti za stupanj nepostizanja zahtijevane razine tolerancije dosad obično temeljili samo na empirijskim dokazima, odgovarajući podaci trebali bi biti izabrani na temelju statističke analize stvarnih nepouzdanosti i biti povezani s mjerenjem apsorbirane doze i pozicioniranja detektora. U tu svrhu, neki autori su usvojili pristup propagacije nepouzdanosti, koji u analizu uključuje lokalni gradijent apsorbirane doze. U praktičnim izvedbama, međutim, takve metode su općenito ograničene na linearnu aproksimaciju gradijenta, koja može uvesti anomalije u konveksnim ili konkavnim dijelovima raspodjele doze. U slučaju da je poznata raspodjela vjerojatnosti gama indeksa, kriteriji prihvatljivosti bi mogli biti određeni na temelju analize vjerojatnosti. Pod određenim uvjetima, približna raspodjela kvadrata gama indeksa može se izvesti teorijski; aproksimacija raspodjele s tri momenta razvijena je primjenom općih rezultata kvadratnog oblika normalnih slučajnih varijabli i hi-kvadratne (χ^2) raspodjele. Ova metoda može potencijalno biti izvedena u uobičajenim postupcima gama analize, zahtijeva samo male preinake i nekoliko dodatnih izračuna. Predmet ove disertacije je ispitivanje kriterija prihvatljivosti rezultata gama analize, proučavanjem statističke raspodjele vrijednosti gama indeksa pod uvjetima bez stvarnih odstupanja (pogreške), u pokušaju izdvajanja statistički značajnih odstupanja u općim uvjetima. U prvom dijelu disertacije, razvijeni su i provjereni računalni alati za gama analizu u slučajevima 1D i 2D raspodjela doza. Jednodimenzionalne raspodjele apsorbirane doze opisane analitičkom funkcijom odgovarajućeg oblika i 2D raspodjele apsorbirane doze IMRT polja zračenja, izračunate u fantomima za provođenje kontrole kvalitete pripremljene su za simulacije. To su bili skupovi izračunatih raspodjela apsorbirane doze. Mjerene vrijednosti apsorbirane doze simulirane su na način da su pomak idealnog detektora i nepouzdanost mjerenja na slučajan način odabrani prema normalnoj raspodjeli i dodani izračunatim raspodjelama doza. Simulirana mjerenja su zatim uspoređena s izvornim proračunom, a vrijednost gama indeksa je izračunata korištenjem kriterija tolerancije za razlike u dozi i udaljenosti-do-slaganja jednakim simuliranim nepouzdanostima. Na ta način dobivena je i analizirana rezultirajuća raspodjela vrijednosti kvadrata gama indeksa. Uz istraživanja za jednu točku mjerenja, istražen je i klinički važniji slučaj matričnog detektora koji može imati i nekoliko stotina detektora, a koristi se za usporedbu raspodjela apsorbirane doze. Pretpostavljeno je da će ukoliko su detektori u matrici statistički neovisni (ishod mjerenja, odnosno rezultat jednog detektora ne utječe na drugi), vrijednosti stope neuspjeha dobivene u simulacijama, slijediti binomnu raspodjelu. Zbog uočenog odstupanja simuliranih rezultata, od očekivane teorijske raspodjele na ograničenom broju simulacija temeljenih na kliničkim IMRT raspodjelama apsorbirane doze na određenoj dubini u homogenom fantomu, predložen je izračun odgovarajućih empirijskih kumulativnih funkcija raspodjele vjerojatnosti stope neuspjeha. Potom se za željenu vrijednost empirijske kumulativne funkcije raspodjele vjerojatnosti (npr. 0.95) može izračunati odgovarajuća najveća očekivana stopa neuspjeha. Ako je opažena stopa neuspjeha veća od ove vrijednosti, za pretpostaviti je, uz značajnost 0.05, da odstupanja nisu samo slučajna. Nadalje, veći skup kliničkih IMRT raspodjela apsorbirane doze korišten je ponovno u simuliranju mjerenja doze uz pretpostavku da izračunata doza predstavlja očekivanu vrijednost i uz dodavanje slučajnog prostornog pomaka u širem opsegu i nepouzdanosti doze. I u ovom slučaju, metoda gama analize korištena je za povezivanje simuliranih mjerenja na više položaja detektora s računatim raspodjelama doze. Raspodjela rezultirajućeg gama indeksa analizirana je za različite razine nepouzdanosti položaja detektora i apsorbirane doze. Materijali i metode : U uvodnom dijelu istraživanja, razvijeni su i analizirani računalni programi za standardnu usporedbu raspodjela doza metodom gama analize u 1D i 2D slučajevima. Ovi računalni programi omogućavaju pretraživanje čitave procijenjene (npr. izračunate) raspodjele doze, za svaku pojedinačnu točku referentne raspodjele doze, u svrhu pronalaženja najmanje vrijednosti gama indeksa ili ograničavanje pretraživanja procijenjene raspodjele na korisnički određeni opseg pretraživanja. Pored toga, moguće je odabrati lokalni ili globalni izračun gama indeksa s izborom normalizacije, postavljanje kriterija tolerancije za razlike u dozi i udaljenosti-do-slaganja kao i različite razine interpolacije referentne i procijenjene raspodjele doza definirane parametrom razlučivosti. U ispitivanju razvijenih programa, prvo je analiziran slučaj 1D raspodjele doze. Matematički dobiven referentni profil koji predstavlja područje polusjene (engl. penumbra) 6 MV fotonskog snopa, polja veličine 10 cm × 10 cm, na dvije različite dubine, d_max i 10 cm, nastao je superpozicijom funkcija normalnih kumulativnih funkcija raspodjele s određenim vrijednostima srednje vrijednosti i standardne devijacije, te dopuštenim podešavanjem pomaka položaja, dozimetrijskog odstupanja i faktora normalizacije raspodjele, čime se iz referentne raspodjele mogla dobiti željena procijenjena raspodjela doze. U cilju analize razvijenog računalnog koda u slučaju 2D raspodjela doza, referentna raspodjela simulirana je najprije kao jednolika s vrijednošću apsorbirane doze od 100 cGy u središnjem dijelu postavljenom na pozadinu vrijednosti doze nula. Procijenjena raspodjela doza modificirana je povećanjem doze središnjeg dijela referentne raspodjele i prostornim pomakom referentne raspodjele u x i y smjeru. U ovom skupu usporedbi raspodjela i u svrhu statističke analize, izračunate su vrijednosti srednje (γ_mean,) i maksimalne (γ_max) vrijednosti γ indeksa, 99-tog postotka (γ1%) γ indeksa i očekivanim stupnjem prolaznosti gama analize (P_γ

Purpose To provide a practical protocol for absolute dose verification of stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) treatment plans, based on our clinical experience. It aims to be a concise summary of the main aspects to be considered when establishing an accurate film dosimetry system. Methods Procedures for film calibration and conversion to dose are described for a dosimetry system composed of Gafchromic™ EBT-XD films and a flatbed document scanner. Factors that affect the film-scanner response are also reviewed and accounted for. The accuracy of the proposed methodology was assessed by taking a set of strips irradiated to known doses and its applicability is illustrated for ten SBRT/SRS treatment plans. The film response was converted to dose using red and triple channel dosimetry. The agreement between the planned and measured dose distributions was evaluated using global gamma analysis with criteria of 3%/2mm 10% threshold (TH), 2%/2mm 10% TH, and 2%/2mm 20% TH. Results The differences between the expected and determined doses from the strips analysis were 0.9 ± 0.6% for the red channel and 1.1 ± 0.7% for the triple channel method. Regarding the SBRT/SRS plans verification, the mean gamma passing rates were 99.5 ± 1.0% vs 99.6 ± 1.0% (3%/2mm 10% TH), 96.9 ± 3.5% vs 99.1 ± 1.3% (2%/2mm 10% TH) and 98.4 ± 1.8% vs 98.8 ± 1.5% (2%/2mm 20% TH) for red and triple channel dosimetry, respectively. Conclusions The proposed protocol allows for accurate absolute dose verification of SBRT/SRS treatment plans, applying both single and triple channel methods. It may work as a guide for users that intend to implement a film dosimetry system.

El objetivo fue comisionar el sistema XVI como un sistema de adquisición de imágenes apto para tratamiento para lo cual se desarrolló una metodología que permitió adquirir imágenes en el sistema XVI de los aceleradores del Centro Javeriano de Oncología CJO-HUSI para realizar planes de tratamientos sobre ellas de manera segura y confiable, como se realizan actualmente con los CTs convencionales. La adquisición de imágenes Cone Beam Computed Tomography (CBCT por sus siglas en ingles), dentro del servicio, se hace de manera rutinaria, lo que permite conseguir los volúmenes de tratamiento en 3D. Esta condición a su vez conlleva a detectar en tiempo real la regresión o progresión de tumores macroscópicos, o las diferenciaciones por cambios en el peso del paciente y por supuesto cambios en el posicionamiento. Haciendo uso de dos maniquís (CIRS y CATPhan) se adquirió imágenes con el sistema XVI, y en el CT convencional, se inició un proceso para medir las curvas de DE-UH, las cuales se cargaron en el sistema de planeación de tratamiento del HUSI-CJO. En este sistema se implementaron diferentes planes de tratamiento, con estos se compararon las unidades monitor (UM) y la dosis para las imágenes de CBCT y CT convencional. Posterior a ello se procedió a validar los planes de tratamiento para uso clínico haciendo el análisis gamma y dosis a punto. De esta forma se promueve que la evaluación imagenológica de parte clínica desencadena en adaptaciones de los volúmenes, evitando la re-simulación y permite que la radioterapia adaptativa sea un proceso que tenga mayor fluidez e integre eficientemente los procesos, evitando una nueva dosis adicional de radiación para la adquisición de imágenes de planificación y cálculo de la dosis. The objective was to commission the XVI system as an image acquisition system suitable for treatment, for which a methodology was developed that allowed to acquire images in the XVI system of the accelerators of the Centro Javeriano de Oncología CJO-HUSI to carry out treatment plans on them. safely and reliably, as is currently done with conventional CTs. The acquisition of Cone Beam Computed Tomography (CBCT) images, within the service, is done on a routine basis, which allows to achieve the volumes of treatment in 3D. This condition in turn leads to detecting in real time the regression or progression of macroscopic tumors, or the differentiations due to changes in the patient's weight and, of course, changes in positioning. Using two mannequins (CIRS and CATPhan), images were acquired with the XVI system, and in the conventional CT, a process was started to measure the DE-UH curves, which were loaded into the HUSI treatment planning system. -CJO. In this system, different treatment plans were implemented, with these the monitor units (MU) and the dose for the images of CBCT and conventional CT were compared. After this, the treatment plans for clinical use were validated by making the gamma analysis and ready doses. In this way, it is promoted that the imaging evaluation of the clinical part triggers adaptations of the volumes, avoiding re-simulation and allows adaptive radiotherapy to be a process that has greater fluidity and efficiently integrates the processes, avoiding a new additional dose of radiation for the acquisition of planning images and dose calculation. Magíster en Física Médica Maestría https://scienti.minciencias.gov.co/cvlac/visualizador/generarCurriculoCv.do?cod_rh=0001352122

Objective: To explore the efficacy and sensitivity of 3D gamma analysis and bio-mathematical model for cervical cancer in detecting dose changes caused by dose-calculation-grid-size (DCGS).Methods：17 patients’ plans for cervical cancer were enrolled (Pinnacle TPS，VMAT), and the DCGS was changed from 2.0mm to 5.0mm to calculate the planned dose respectively. The dose distribution calculated by DCGS = 2.0mm as the “reference” data set (RDS), the dose distribution calculated by the rest DCGS as the“measurement”data set (MDS), the 3D gamma passing rates and the (N)TCPs of the all structures under different DCGS were obtained, and then analyze the ability of 3D gamma analysis and (N)TCP model in detecting dose changes and what factors affect this ability.Results: The effect of DCGS on planned dose was obvious. When the gamma standard was 1.0mm, 1.0% and 10.0%, the difference of the results of the DCGS on dose-effect could be detected by 3D gamma analysis (all p value < 0.05). With the decline of the standard, 3D gamma analysis’ ability to detect this difference shows weaker. When the standard was 1.0mm, 3.0% and 10.0%, the p value of > 0.05 accounted for the majority. With DCGS=2.0mm being RDS, ∆gamma-passing-rate presented the same trend with ∆(N)TCPs of all structures except for the femurs only when the 1.0mm, 1.0% and 10.0% standards were adopted for the 3D gamma analysis.Conclusions: The 3D gamma analysis and bio-mathematical model can be used to analyze the effect of DCGS on the planned dose. For comparison, the former’s detection ability has a lot to do with the designed standard, and the latter’s capability is related to the parameters and calculated accuracy instrinsically.

In order to correct the lateral effect caused by the light source of the flatbed scanner in the Gafchromic film EBT3, the usefulness of the correction method using the average value of the correction coefficient considering the scan directions were evaluated. EBT3 was scanned from four directions to measure the optical density (OD) of the red, blue, and, red/blue components and the correction coefficient were calculated. For the correction coefficients, average values were calculated for the purpose of use, when the scan directions could not be aligned (average lateral effect correction). Correction accuracy was verified with the pass rate of gamma analysis (3 mm/3%, threshold 30%) of the dose distribution using the EBT3 film irradiated with the step pattern. OD of the red, blue, and, red/blue components in the scanning vertical direction tended to be higher in the center than in the peripheral portion. The pass rate of the step pattern was the red component's before correction, from 26.9 to 45.1% (before correction), from 84.1 to 96.7% (after correction), the red/blue component, from 37.6 to 48.4% (before correction) and from 84.4 to 96.7% (after correction). When using the correction coefficient using the average value, the pass rate was 89.8% for the red component and 94.7% for the red/blue component. The lateral effect correction improves the accuracy of the dose distribution verification, and the correction coefficient using the average value is useful when the scanning direction is different from that at the time of obtaining the dose concentration curve.

Patients receiving postoperative irradiation for uterine cervical cancer might not be able to eat during radiation therapy because of the effects of concurrent chemo-radiotherapy; this may lead to changes in the patient’s body shape during treatment. When performing image-guided radiotherapy, it is necessary to determine immediately whether treatment can be performed on the day or whether re-planning is required. The purpose of this study was to determine indicators for re-planning by examining the effects of changing body contours on radiation therapy dose. The original body contour was reduced by 1 cm in the front portion (structure-set 1). Based on the original dose distribution, the dose recalculation was performed with a structure set created using the body contour of structure-set 1. The difference between the original and recalculated dose distributions of structure-set 1 was evaluated through gamma analysis (GA). In the GA results for dose distribution obtained via recalculation with structure-set 1, a pass rate of 90% or more was obtained for a criterion of 2 mm/2% in all cases. The results suggest that dose re-planning is rarely required when the body shape is reduced by only 1 cm in the front.

Purpose To investigate, in proton therapy, whether the Gamma passing rate (GPR) is related to the patient dose error and whether MU scaling can improve dose accuracy. Methods Among 20 consecutively treated breast patients selected for analysis, two IMPT plans were retrospectively generated: (1) the pencil-beam (PB) plan and (2) the Monte Carlo (MC) plan. Patient-specific QA was performed. A 3%/3-mm Gamma analysis was conducted to compare the TPS-calculated PB algorithm dose distribution with the measured 2D dose. Dose errors were compared between the plans that passed the Gamma testing and those that failed. The MU was then scaled to obtain a better GPR. MU-scaled PB plan dose errors were compared to the original PB plan. Results Of the 20 PB plans, 8 were passed Gamma testing (G_pass_group) and 12 failed (G_fail_group). Surprisingly, the G_pass_group had a greater dose error than the G_fail_group. The median (range) of the PTV DVH RMSE and PTV ΔDmean were 1.36 (1.00–1.91) Gy vs 1.18 (1.02–1.80) Gy and 1.23 (0.92–1.71) Gy vs 1.10 (0.87–1.49) Gy for the G_pass_group and the G_fail_group, respectively. MU scaling reduced overall dose error. However, for PTV D99 and D95, MU scaling worsened some cases. Conclusion For breast IMPT, the PB plans that passed the Gamma testing did not show smaller dose errors compared to the plans that failed. For individual plans, the MU scaling technique leads to overall smaller dose errors. However, we do not suggest use of the MU scaling technique to replace the MC plans when the MC algorithm is available.

Purpose To externally validate a hidden Markov model (HMM) for classifying gamma analysis results ofin vivoelectronic portal imaging device (EPID) measurements into different categories of anatomical change for lung cancer patients. Additionally, the relationship between HMM classification and deviations in dose-volume histogram (DVH) metrics was evaluated. Methods The HMM was developed at CHU de Quebec (CHUQ), and trained on features extracted from gamma analysis maps ofin vivoEPID measurements from 483 fractions (24 patients, treated with three-dimensional 3D-CRT or intensity modulated radiotherapy), using the EPID measurement of the first treatment fraction as reference. The model inputs were the average gamma value, standard deviation, and average value of the highest 1% of gamma values, all averaged over all beams in a fraction. The HMM classified each fraction into one of three categories: no anatomical change (Category 1), some anatomical change (no clinical action needed, Category 2) and severe anatomical change (clinical action needed, Category 3). The external validation dataset consisted of EPID measurements from 263 fractions of 30 patients treated at Maastro with volumetric modulated arc therapy (VMAT) or hybrid plans (containing both static beams and VMAT arcs). Gamma analysis features were extracted in the same way as in the CHUQ dataset, by using the EPID measurement of the first fraction as reference (gamma Q), and additionally by using an EPID dose prediction as reference (gamma M). For Maastro patients, cone beam computed tomography (CBCT) scans and image-guided radiotherapy (IGRT) classification of these images were available for each fraction. Contours were propagated from the planning CT to the CBCTs, and the dose was recalculated using a Monte Carlo dose engine. Dose-volume histogram metrics for targets and organs-at-risk (OARs: lungs, heart, mediastinum, spinal cord, brachial plexus) were extracted for each fraction, and compared to the planned dose. HMM classification of the external validation set was compared to threshold classification based on the average gamma value alone (a surrogate for clinical classification at CHUQ), IGRT classification as performed at Maastro, and differences in DVH metrics extracted from 3D dose recalculations on the CBCTs. Results The HMM achieved 65.4%/65.0% accuracy for gamma Q and gamma M, respectively, compared to average gamma threshold classification. When comparing HMM classification with IGRT classification, the overall accuracy was 29.7% for gamma Q and 23.2% for gamma M. Hence, HMM classification and IGRT classification of anatomical changes did not correspond. However, there is a trend towards higher deviations in DVH metrics with classification into higher categories by the HMM for large OARs (lungs, heart, mediastinum), but not for the targets and small OARs (spinal cord, brachial plexus). Conclusion The external validation shows that transferring the HMM for anatomical change classification to a different center is challenging, but can still be valuable. The HMM trained at CHUQ cannot be used directly to classify anatomical changes in the Maastro data. However, it may be possible to use the model in a different capacity, as an indicator for changes in the 3D dose based on two-dimensional EPID measurements.

Radyasyon tedavisinde istenilen dozu hedef hacme doğru bir şekilde vermek çok önemlidir. Yoğunluk ayarlı radyasyon tedavisi (YART), kalite kontrol açısından daha karmaşıktır ve ayrıntılı iki boyutlu dozimetrik doğrulama gerektirir. YART tekniğinin karmaşıklığından dolayı hastaya özgü tedavi öncesi kalite kontrollerinin yapılması YART tedavisinin en önemli aşamalarından biridir. Hesaplanan ve ölçülen doz arasındaki değerlendirme, YART teadvisinin kalite güvencesinde önemli bir rol oynar. Klinik tedavilerin artan karmaşıklığı, daha doğru doz doğrulama süreçleri ve sistemlerine duyulan ihtiyacı arttırmaktadır. Kalite kontroller tedavi planlama sisteminde (TPS) modellenen doz dağılımının, ölçülen doz dağılımıyla benzerliği analiz edilerek yapılır. Bu çalışmanın amacı, radyoterapi tedavi planlarının doz doğrulaması için Portal dozimetri, Epiqa ve 2-D Array dedektörü kullanarak gama analizlerini karşılaştırmaktır. Ters planlama tekniğiyle yapılan 20 tane prostat kanseri hastası için 2 farklı tedavi planları, optimizasyon işleminden sonra doz dağılımları Anizotropik Analitik Algoritması'yla (AAA) hesaplanmış ve kalite kontrol planları yaratılmıştır. Tedavi planları TPS'de Eclipse 15.1 sürümü kullanılarak oluşturulmuştur. Tüm ölçümler Varian DHX lineer hızlandırıcısına entegre edilmiş bir aS500 ve 2-D Array ile yapılmıştır. Doz dağılımı, doz uyumu ve anlaşma parametrelerine uzaklık için farklı γ kriterleri (%2/2 mm ve %3/3 mm) kullanılarak oluşturulan gama alanı histogramları (GAH) ile değerlendirilmiştir. 40 YART planının ortalama geçiş oranı, %2/2 mm ve % 3/3 mm olan tüm cihazlar için % 95'in üzerinde bulunmuştur. %2/2 mm ve %3/3 mm kriterleri için, portal dozimetride gama analizinin geçiş oranları, epiqa ve 2-D Array sisteminden daha yüksek bulunmuştur. İstatistiksel analizler Mann Whitney Test ve Kruskall-Wallis Test kullanılarak değerlendirilmiş ve p, It is very important to deliver the desired dose to the target volume accurately in radiation treatment. IMRT is more complex in terms of quality assurance and requires detailed two-dimensional dosimetric verification. Because of the high complexity of IMRT patient-specific pretreatment quality assurance (QA) is generally considered a necessary pre-requisite to patient treatment. The evaluation between calculated and measured dose plays an important role in the quality assurance of IMRT. The increasing complexity of clinical treatments raises the need for more accurate dose verification procedures and systems. The quality control is done by analysing of similarity between dose distribution modelled in treatment planning system (TPS) and measured dose distribution. The aim of this study was to compare gamma analysis by using Electronic Portal Imaging Device (Epid), Epiqa and 2-D Array detector for dose verification of radiotherapy treatment plans. Following the optimization process, dose distribution of 20 plans (prostate) done by inverse planning technique is calculated by Anisotropic Analytical Algorithm (AAA), and quality control plans were created. The treatment plans were created using treatment planning system (TPS) version 15.1. All measurents were performed by aS500 Epid integrated into Varian DHX linear accelerator, and 2-D Array detector. The dose distribution was evaluated with gamma area histograms (GAHs) generated using different γ criteria (%2/2 mm and %3/3 mm) for dose agreement and distance to agreement parameters. The average pass rate for 20 IMRT plans was above to %95 for all devices with %2/2 mm and %3/3 mm. For the %2/2 mm and %3/3 mm criteria, the passing rates of gamma analysis for the Epid system were higher than those of epiqa and 2-D Array. Statistical analyses were evaluated by using Mann Whitney Test and Kruskall-Wallis Test and p value of p