Homogeneity Index Research Articles

Comparison of Photon Dose Distribution in Breast Cancer Using 3DCRT and Half Beam Techniques

Radiotherapy planning can be done with 3D Conformal Radiotherapy (3DCRT) and Half Beam. The success of radiotherapy planning is considered by comparing the isodose curve, Dose Volume Histogram (DVH), Organs At Risk (OAR), Homogeneity Index (HI), and Conformity Index (CI) obtained by the 3DCRT and Half Beam techniques. This study used data from 5 patients at the Radiotherapy Installation at A.W. Hospital. Sjahranie Samarinda with radiation planning of 5000 cGy (25×2 Gy) for breast cancer. The two radiation plans used gantry angles of 310˚ and 120˚. The calculated dose distribution value can be seen through the 90%, 95% PTV dose, and OAR absorbed dose. PTV doses of 90% and 95% in the 3DCRT technique covered the target well. The radiation dose values of the 3DCRT technique at PTV 90% were around 4860 cGy – 4930 cGy and PTV 95% were around 4750 cGy – 4840 cGy. Meanwhile, the Half Beam technique could not cover the target well. It was because the radiation dose values received by the Half Beam technique at 90% PTV were around 780 cGy – 4860 cGy and 95% PTV were around 2210 cGy – 5020 cGy. The OAR absorbed doses values for the 3DCRT and Half Beam techniques were still within the safe limits of tolerance according to QUANTEC. Meanwhile, the HI and CI values in the 3DCRT technique were closer to the rules of ICRU Report 83 of 2010 compared to the Half Beam technique. Therefore, from the values that have been obtained, the success rate of the radiotherapy planning process after measurements is shown in the 3DCRT technique. It has the value of more efficient dose calculations and can be used as a reference in optimizing dose distribution to patients.

Psychometric evaluation of a Spanish translation of the moral injury symptom scale for healthcare professionals

BackgroundMoral injury is prevalent among health care professionals, especially nurses. It can have negative personal consequences for clinicians, and indirectly impact the quality of patient care. Although nurses around the world experienced moral injury during the pandemic, it will continue to be a professional challenge. Thus, this study aimed to determine the psychometric properties of a scale measuring moral injury translated into Spanish.MethodsA methodological study with a cross-sectional approach was conducted. After translating the Moral Injury Symptom Scale for Healthcare Professionals (MISS-HP) into Peruvian Spanish (MISS-HP-S) using International Test Commission methods, data were collected using online survey methods from a sample of 720 Peruvian nurses. Analytical methods included exploratory and confirmatory factor analysis, and invariance by age were examined. The corrected homogeneity index, ordinal alpha, and McDonald’s omega allowed the evaluation of internal reliability.ResultsFindings from this sample of nurses who were mostly female (92%), from coastal Peru (57%), and averaged 39 (± 11) years of age, provided support for the validity and reliability of the MISS-HP-S. Structural validity was endorsed by findings indicating consistent factorial structure and adequate invariance among different age groups. In this study, three factors were observed: guilt/shame, condemnation, and spiritual strength. Internal consistency values included an ordinal alpha of 0.795 and McDonald’s omega of 0.835.ConclusionThese findings differ from those reported from previous studies in other cultural contexts, suggesting the influence of cultural and sample-specific factors in the perception of moral injury among Peruvian nurses. Because this evidence supports the validity of the MISS-HP-S, it can be used in professional practice and in future research to identify and address situations that contribute to nurse moral injury.

Numerical investigation of in-cylinder gas motion dynamics in a heavy-duty direct injection hydrogen internal combustion engine

Mixture homogenization is one of the most important parameter for hydrogen internal combustion engines (H2ICE) to achieve near-zero NOx emissions and stable combustion, especially when premixed combustion strategy is used. On the other hand, inhomogeneities are inevitable due to the limited duration for mixing. This is more prominent in H2ICEs; those adopts low pressure direct injection (LPDI) system. Optimizing an engine to achieve higher level of homogeneity requires profound understanding of in-cylinder gas motion and mixing dynamics.To establish deeper comprehension of gas motion inside the cylinder, a 13-L LPDI H2ICE was modelled, and effect of different parameters were investigated by a holistic 1D-3D simulation methodology. While boundary conditions of operating point were obtained from the 1D simulations, different swirl numbers (SN), piston shapes and injector cap designs were simulated with 3D-CFD. Simulation results were analyzed based on uniquely defined parameters like homogeneity index (HI) and symmetricity of motion (SOM), as well as standard parameters like turbulence kinetic energy (TKE), and 3D visualizations of equivalence ratio iso-surfaces. Analysis showed that, there is a negative correlation between SN and HI under investigated conditions. Moreover, it was found that piston shapes which are promoting the tumble motion, improved average TKE by 31% and HI by 28% over base piston. This study aims to be a reference for the in-cylinder gas motion design of ultra-lean LPDI H2ICEs, where the target is retrofitting an existing diesel engine and attaining the best HI, SOM and TKE values at rated power conditions.

Evaluation and Comparison of the Dose Received by the Mandible, Maxilla, and Teeth in Two Methods of Three-dimensional Conformal Radiation Therapy and Helical Tomotherapy.

Using three-dimensional conformal radiation treatment (3D-CRT) and helical tomotherapy (HT), this study examines and contrasts the dosage received by the mandible, maxilla, and teeth. Sixteen patients with head-and-neck cancer (H and NC) were the subject of treatment planning at the Seyyed Al-Shohada Hospital in Isfahan, Iran. This study examined target coverage quality, exposure of healthy tissue, and radiation delivery effectiveness. In terms of a number of measures, including D2%, D50%, Dmean, V95%, conformity index (CI), and homogeneity index (HI) for the planning target volume (PTV) and D2%, D98%, Dmean, V95%, CI, and HI for the nodal PTV, HT showed considerable gains over 3D-CRT. The brainstem, D1cc, and D10cc received considerably lower maximum dosages in HT. Measurements of the right and left cochleas (Dmean, V55, and Dmax) revealed decreases in HT, with Dmean revealing the most significant variations. The Dmean and Dmax values for HT significantly decreased in constrictors as well. In terms of several HT-related indicators, the larynx, optic chiasm, optic nerves, oral cavity, mandible, thyroid, and parotid glands all showed considerable decreases. The findings of the comparison of the two treatment approaches revealed that the HT method was more than 50% more effective than the 3D-CRT method in sustaining organs at risk (OARs) and the target volume dose. In general, dosimetric coverage, homogeneity, conformity indices, and the absence of cold and hot patches showed that HT produced targets with greater accuracy than 3D-CRT. In addition, HT outperformed 3D-CRT in protecting important structures (OARs). HT as a result has the potential to be a more effective method of treatment for those with H and NC and involvement of regional lymph nodes.

Dose prediction for cervical cancer in radiotherapy based on the beam channel generative adversarial network

BackgroundExisting deep learning methods, such as generative adversarial network (GAN) technology, face challenges when dealing with mixed datasets, which involve a combination of Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT). This issue significantly complicates the application of dose prediction in the field of radiotherapy. In this study, we propose a novel approach called beam channel GAN (Bc-GAN) to address the task of radiation dose prediction for mixed datasets. Bc-GAN introduces a dose prediction calculation method that requires less precision. By defining an approximate range for dose prediction, Bc-GAN limits the physical range of GAN prediction, resulting in more reasonable dose distribution predictions. MethodsWe adopt a beam angle weighting method to determine the beam angle in the dose calculation. The dose of the beam with the highest weight is calculated using medical images and is then inputted into the artificial intelligence dose prediction model as the input channel. Additionally, we collect data from a total of 346 patients with Cervical Cancer (CC) for dataset. After cleaning the data, we exclude 51 cases with incomplete organ delineation, leaving us with 295 cases (IMRT: VMAT = 137:158) randomly divided into three sets: the training set, the validation set, and the test set, with proportions of 205:60:30, respectively. The assessment of model predictions was conducted via an analysis of dose distributions on the tomographic plane, dose volume histogram (DVH), and dosimetric parameters within the target zones and organs at risk (OAR). ResultsAfter DVH analysis, minimal discrepancy was found between predicted and actual dose distributions in PTV and OAR. The predicted distribution aligned with clinical standards. Dosimetric parameters for PTV were generally lower in the predicted model, except for homogeneity index (HI) (0.238 ± 0.024, P = 0.017) and Dmax (53.599 ± 0.710 Gy, P = 1.8e-05). The prediction model varied in estimating doses for six organs. Specifically, small intestine showed higher V20 (67.92 ± 51.64 %, P = 0.019) and V30 (57.171 ± 1.213 %, P = 0.024) than manual planning. A similar trend was seen in colon's V30 (37.13 ± 61.14 %, P = 0.016). However, predicted bladder V30 (87.51 ± 41.44 %, P = 2.03e-16) was lower, indicating significant dosimetric differences. ConclusionOverall, this study presents an innovative prediction method for CC in radiotherapy using the Bc-GAN model, addressing the challenges posed by different radiotherapy techniques. The proposed approach allows IMRT and VMAT in radiotherapy to be used as training sets, enabling the potential for large-scale engineering and commercialization applications of artificial intelligence (AI). The Bc-GAN-based prediction method for CC in radiotherapy not only reduces the amount of data needed for the training set but also expedites the model generation process. This approach can be applied to guide the development of clinical radiation therapy plans. Furthermore, future studies should consider extending the dose prediction method to encompass other types of tumors.

COMPARATIVE RADIATION DOSIMETRY OF WHOLE BREAST RADIOTHERAPY USING IMRT AND VMAT TECHNIQUES IN LEFT SIDED BREAST CANCER PATIENTS AFTER BREAST CONSERVING SURGERY

Background:The radiotherapy of left sided breast cancers is mandatory and integral part of treatment and challenging because of surrounding critical structures posing increased risk of complications. The main objective of this study was to quantify doses toorgan at risk(OARs) including left lung, heart, contralateral breast, spinal cord, and planning target volume (PTV) using different radiation techniques like Intensity modulated radiation therapy (IMRT)&volumetric modulated arc therapy (VMAT) and comparison of radiation dosimetry. Methods: A prospective study of 30 patients of left sided breast cancer who had undergone Breast Conservative Surgery (BCS) and chemotherapy was done for adjuvant radiation. For every patient radiation planning was done by two different techniques IMRT and VMAT. Then the comparison of radiation dosimetry parameters was done for all the techniques including the parameters like PTV coverage, doses to OAR like heart, left lung, contralateral breast and spinal cord and head of humerus. The Homogenity Index (HI) were calculated. Result: The Mean age of the patient was 46.7 years. When comparing the doses delivered in IMRT and VMAT Technique for left sided breast cancer post breast conservation surgery there was significant difference in PTV Breast and axilla V95 Gy. It was 96.2±1.9% (IMRT) vs 94.8±1.71% (VMAT), (p=0.004). However significant sparing of Organs at Risk was seen. With ipsilateral lung dose mean V5 Gy was 77.86± 9.68% (IMRT) v/s 83.04± 9.86 % (VMAT), (p=0.0446). Also mean V30 Gy was 14.6±4.82% with IMRT vs 16.54±5.86% with VMAT, (p=0.0169). Heart mean dose was 8.8±1.49 Gy with IMRT and 10.98±3.7 Gy with VMAT, (p=0.0227). Further V30 Gy for Heart was 4.61±3.8% with IMRT and 6.72±4.0% with VMAT, (p=0.0132).No significant difference was seen with IMRT and VMAT technique for contralateral lung, contralateral breast and spinal cord. Conclusion: In treatment of patients with radiation with left breast cancer patients post BCS using IMRT and VMAT technique it is seen significant dose reduction with IMRT Technique for ipsilateral lung and Heart as compared to VMAT technique. Significant V95 coverage for PTV Breast and axilla with IMRT as compared to VMAT. Hence in our Study IMRT technique was found to be superior for better sparing of Organ at risk and better PTV coverage.

1432: Comparative study of various homogeneity indices in SIB-VMAT planning for head and neck tumors.

1432: Comparative study of various homogeneity indices in SIB-VMAT planning for head and neck tumors.

Comparison of two different VMAT radiotherapy TPSs for pancreatic cancer using flattening filter free photon beam energy

BackgroundPancreatic cancer is a devastating disease with a poor prognosis, and radiation therapy plays a crucial role in its treatment and management. Conventional radiation therapy (RT) techniques have limitations in delivering adequate doses to the tumor while sparing surrounding normal tissues. However, modern RT techniques such as intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic body radiation therapy (SBRT) have led to the development of novel approaches that can reduce toxicity. The incorporation of advanced imaging modalities, like four-dimensional computed tomography (4D-CT) and magnetic resonance imaging (MRI), enables enhancement of tumor control and improves conformality and treatment outcomes. Additionally, using flattening filter-free (FFF) beams can further enhance treatment efficiency and efficacy. PurposeThis study aims to compare two different VMAT techniques using two different treatment planning systems (TPSs), Monaco and Eclipse, in the treatment of pancreatic cancer II stage infiltrating duct carcinoma patients using an FFF photon beam. Materials and methods20 pancreatic cancer II stage infiltrating duct carcinoma patients were retrospectively analyzed, and each patient's plans were designed using the two TPSs. The dose distribution of the target using 6 MV FFF for TrueBeam-Varian and organs at risk (OARs) were compared. The monitor unit (MU), treatment time, conformity (CI), and homogeneity (HI) indices were also evaluated. ResultsFor pancreatic cancer patients, the mean dose of the planning target volume (PTV) in the Monaco plan was lower than the Eclipse plan. The plan evaluation parameters in Monaco and Eclipse were similar without significant differences (p-value = 0.152). The Monaco plan was better than the Eclipse plan regarding mean dose and V15Gy of the kidneys; the spinal cord was lowest in the Monaco plan, and the maximum dose and V45Gy of the spinal cord were 592.1 cGy and 1.37% lower than the Eclipse plan, respectively. ConclusionThe VMAT Monaco plan is a favorable TPS for pancreatic cancer patients, providing improved sparing of critical organs while maintaining adequate target coverage.

A dosimetric comparison of brachytherapy sources for endometrial cancer: an electronic brachytherapy and an iridium-192 source with multichannel cylinders and a three-dimensional technique

Background and purposeIr192 vaginal brachytherapy (IBT) is commonly used for patients with postoperative endometrial cancer (EC). We devised a novel multichannel vaginal applicator that could be equipped with an electronic brachytherapy (EBT) device. We aimed to explore the differences in physical parameters between the EBT and IBT.Materials and methodsThis retrospective study included 20 EC patients who received adjuvant IBT from March 1, 2023, to May 1, 2023. Multichannel vaginal cylinders were used, and three-dimensional plans were generated. We designed an electronic multichannel vaginal applicator model and simulated a three-dimensional EBT plan. In order to ensure comparability, D90 of the CTV for the EBT plan was normalized to be equivalent to that of the IBT plan for the same patient.ResultsTwenty EBT plans were compared with 20 IBT plans. Results showed, the mean D90 value of clinical target volume (CTV) was 536.1 cGy for both treatment plans. For the mean dose of CTV, the EBT was significantly greater (738.3 vs. 684.3 cGy, p = 0.000). There was no significant difference in CTV coverage between the EBT and IBT plans. For high-dose areas (V200% and V150%), the EBTs were significantly greater. There were no significant differences in the maximum doses to the vaginal mucosa between the EBT and IBT, whether at the apex or in the middle segment. For the bladder and rectum, both the low-dose area and high-dose area were significantly lower in the EBT plans. For the conformity index, there was no significant difference between the EBT and IBT plans. For the dose homogeneity index, the EBT value was lower.ConclusionIn conclusion, under the premise of a three-dimensional brachytherapy plan, for patients receiving multichannel vaginal applicator brachytherapy, compared with IBT, EBT could reduce the dose to the surrounding organs at risk while maintaining the dose in the target area.

Comparative analysis of delivered and planned doses in target volumes for lung stereotactic ablative radiotherapy

BackgroundAdaptive therapy has been enormously improved based on the art of generating adaptive computed tomography (ACT) from planning CT (PCT) and the on-board image used for the patient setup. Exploiting the ACT, this study evaluated the dose delivered to patients with non-small-cell lung cancer (NSCLC) patients treated with stereotactic ablative radiotherapy (SABR) and derived relationship between the delivered dose and the parameters obtained through the evaluation procedure.MethodsSABR treatment records of 72 patients with NSCLC who were prescribed a dose of 60 Gy (Dprescribed) to the 95% volume of the planning target volume (PTV) in four fractions were analysed in this retrospective study; 288 ACTs were generated by rigid and deformable registration of a PCT to a cone-beam computed tomography (CBCT) per fraction. Each ACT was sent to the treatment planning system (TPS) and treated as an individual PCT to calculate the dose. Delivered dose to a patient was estimated by averaging four doses calculated from four ACTs per treatment. Through the process, each ACT provided the geometric parameters, such as mean displacement of the deformed PTV voxels (Warpmean) and Dice similarity coefficient (DSC) from deformation vector field, and dosimetric parameters, e.g. difference of homogeneity index (ΔHI, HI defined as (D2%-D98%)/Dprescribed*100) and mean delivered dose to the PTV (Dmean), obtained from the dose statistics in the TPS. Those parameters were analyzed using multiple linear regression and one-way-ANOVA of SPSS® (version 27).ResultsThe prescribed dose was confirmed to be fully delivered to internal target volume (ITV) within maximum difference of 1%, and the difference between the planned and delivered doses to the PTV was agreed within 6% for more than 95% of the ACT cases. Volume changes of the ITV during the treatment course were observed to be minor in comparison of their standard deviations. Multiple linear regression analysis between the obtained parameters and the dose delivered to 95% volume of the PTV (D95%) revealed four PTV parameters [Warpmean, DSC, ΔHI between the PCT and ACT, Dmean] and the PTV D95% to be significantly related with P-values < 0.05. The ACT cases of high ΔHI were caused by higher values of the Warpmean and DSC from the deformable image registration, resulting in lower PTV D95% delivered. The mean values of PTV D95% and Warpmean showed significant differences depending on the lung lobe where the tumour was located.ConclusionsEvaluation of the dose delivered to patients with NSCLC treated with SABR using ACTs confirmed that the prescribed dose was accurately delivered to the ITV. However, for the PTV, certain ACT cases characterised by high HI deviations from the original plan demonstrated variations in the delivered dose. These variations may potentially arise from factors such as patient setup during treatment, as suggested by the statistical analyses of the parameters obtained from the dose evaluation process.

An easy decision-making graphic tool to improve herd level milk yield in a local scale dairy farming system

Several features prevent dairy farms from reaching their full potential milk yield levels. A plurality of methods are available to analyse a farm’s yield gap, but in practice, farmers rarely use them to understand their main constraints to production. We propose a simple and graphical approach to tune the limiting (feed-related) or reducing (management-related) factors to evaluate the likelihood of being a high-yielding farm. We gathered data from 32 farms within a local-scale dairy system in Northern Italy. Data regarded milk yield (MY), dry matter intake (DMI), feeding ration’s homogeneity index (Hi), feed sorting (Si) index, ration’s geometric mean particle length (GMPL), ration digestibility, income over feed cost (IOFC) and MY summer-winter ratio (SWR). Farms were classified according to their MY levels into high (H) and low or medium (L + M), with a 36.7 kg × cow−1 day−1 threshold. At an ANOVA model for MY class, H farms resulted in higher IOFC (p < 0.001), GMPL (p = 0.046), DMI (p = 0.006), digestible DM (DDM, p = 0.013), digestible crude protein (DCP, p = 0.011), digestible starch (Dstarch, p = 0.001), and feed efficiency (FE, p = 0.003). At a logistic AIC stepwise regression, the GMPL (odds = 6.528, 95% CI = 1.11-64.2) and DMI (odds = 3.889, 95% CI = 1.43-16.5) favoured farms being classified in the H production class. The nomogram was used to calculate a confusion matrix, achieving an overall accuracy of 0.70, demonstrating its ability to transform predictive models into a graphical, realisable tool.

Comparison of 3D-printed multichannel non–co-planar vaginal applicators and single-channel vaginal applicators for brachytherapy with positive or close surgical margins in cervical cancer

OBJECTIVEThis study was conducted to compare the differences between 3D-printed multichannel non-coplanar vaginal applicators and single-channel vaginal applicators in cervical cancer patients with positive or close surgical margins. METHODSBetween January 2015 and June 2023, 104 cervical cancer patients who underwent radical surgery with positive or close surgical margins were enrolled to receive concurrent intensity-modulated chemoradiotherapy combined with 3D-printed multichannel non-coplanar vaginal applicators (3D-printed group, 41 patients) or single-channel vaginal applicators (single-channel group, 63 patients) guided brachytherapy. The dosimetric parameters, 5-year local control (LC), progression-free survival (PFS), overall survival (OS) of two groups were retrospectively analyzed. RESULTSThe high-risk clinical target volume (D90, D100) and high-dose volume fraction (V150) in 3D-printed group were significantly higher than those in single-channel group (p<0.05), and the homogeneity index (HI) and conformal index (COIN) were equally better in 3D-printed group. In 3D-printed group, the D2cc, D1cc, and D0.1cc of the bladder and rectum were significantly lower than those of the single-channel group (p<0.05). The 3D-printed group had significantly superior 5-year LC (70.0% vs. 51.3%, P=0.041) and PFS (63.0% vs. 44.2%, P=0.045), but OS were not significantly different between treatment groups (75.4% vs. 59.7%, P=0.112). The incidence of radiation enteritis and cystitis was lower in the 3D-printed group than in the single-channel group, but no statistical difference was noted. CONCLUSIONSThe 3D-printed multichannel non-coplanar vaginal insertion applicators shows the advantage of target dose, improve the LC and PFS in patients with positive or close surgical margins after cervical cancer surgery. Thus, the popularization of this method and its application may be of value.

Enhanced 3D dose prediction for hypofractionated SRS (gamma knife radiosurgery) in brain tumor using cascaded-deep-supervised convolutional neural network.

Gamma Knife radiosurgery (GKRS) is a well-established technique in radiation therapy (RT) for treating small-size brain tumors. It administers highly concentrated doses during each treatment fraction, with even minor dose errors posing a significant risk of causing severe damage to healthy tissues. It underscores the critical need for precise and meticulous precision in GKRS. However, the planning process for GKRS is complex and time-consuming, heavily reliant on the expertise of medical physicists. Incorporating deep learning approaches for GKRS dose prediction can reduce this dependency, improve planning efficiency and homogeneity, streamline clinical workflows, and reduce patient lagging times. Despite this, precise Gamma Knife plan dose distribution prediction using existing models remains a significant challenge. The complexity stems from the intricate nature of dose distributions, subtle contrasts in CT scans, and the interdependence of dosimetric metrics. To overcome these challenges, we have developed a "Cascaded-Deep-Supervised" Convolutional Neural Network (CDS-CNN) that employs a hybrid-weighted optimization scheme. Our innovative method incorporates multi-level deep supervision and a strategic sequential multi-network training approach. It enables the extraction of intra-slice and inter-slice features, leading to more realistic dose predictions with additional contextual information. CDS-CNN was trained and evaluated using data from 105 brain cancer patients who underwent GKRS treatment, with 85 cases used for training and 20 for testing. Quantitative assessments and statistical analyses demonstrated high consistency between the predicted dose distributions and the reference doses from the treatment planning system (TPS). The 3D overall gamma passing rates (GPRs) reached 97.15% ± 1.36% (3mm/3%, 10% threshold), surpassing the previous best performance by 2.53% using the 3D Dense U-Net model. When evaluated against more stringent criteria (2mm/3%, 10% threshold, and 1mm/3%, 10% threshold), the overall GPRs still achieved 96.53% ± 1.08% and 95.03% ± 1.18%. Furthermore, the average target coverage (TC) was 98.33% ± 1.16%, dose selectivity (DS) was 0.57 ± 0.10, gradient index (GI) was 2.69 ± 0.30, and homogeneity index (HI) was 1.79 ± 0.09. Compared to the 3D Dense U-Net, CDS-CNN predictions demonstrated a 3.5% improvement in TC, and CDS-CNN's dose prediction yielded better outcomes than the 3D Dense U-Net across all evaluation criteria. The experimental results demonstrated that the proposed CDS-CNN model outperformed other models in predicting GKRS dose distributions, with predictions closely matching the TPS doses.

Dosimetric effect of collimator rotation on intensity modulated radiotherapy and volumetric modulated arc therapy for rectal cancer radiotherapy.

Intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) are the main radiotherapy techniques for treating and managing rectal cancer. Collimator rotation is one of the crucial parameters in radiotherapy planning, and its alteration can cause dosimetric variations. This study assessed the effect of collimator rotation on the dosimetric results of various IMRT and VMAT plans for rectal cancer. Computed tomography (CT) images of 20 male patients with rectal cancer were utilized for IMRT and VMAT treatment planning with various collimator angles. Nine different IMRT techniques (5, 7, and 9 coplanar fields with collimator angles of 0°, 45°, and 90°) and six different VMAT techniques (1 and 2 full coplanar arcs with collimator angles of 0°, 45°, and 90°) were planned for each patient. The dosimetric results of various treatment techniques for target tissue (conformity index [CI] and homogeneity index [HI]) and organs at risk (OARs) sparing (parameters obtained from OARs dose-volume histograms [DVH]) as well as radiobiological findings were analyzed and compared. The 7-fields IMRT technique demonstrated lower bladder doses (V40Gy, V45Gy), unaffected by collimator rotation. The 9-fields IMRT and 2-arcs VMAT (excluding the 90-degree collimator) had the lowest V35Gy and V45Gy. A 90-degree collimator rotation in 2-arcs VMAT significantly increased small bowel and bladder V45Gy, femoral head doses, and HI values. Radiobiologically, the 90-degree rotation had adverse effects on small bowel NTCP (normal tissue complication probability). No superiority was found for a 45-degree collimator rotation over 0 or 30 degrees in VMAT techniques. Collimator rotation had minimal impact on dosimetric parameters in IMRT planning but is significant in VMAT techniques. A 90-degree rotation in VMAT, particularly in a 2-full arc technique, adversely affects PTV homogeneity index, bladder dose, and small bowel NTCP. Other evaluated collimator angles did not significantly affect VMAT dosimetrical or radiobiological outcomes.

Assessment of panel performance in CATA and RATA experiment

AbstractCATATIS is a recently developed method for the analysis of multiple binary datasets such as Check‐All‐That‐Apply (CATA) data. CATATIS yields a homogeneity index reflecting the overall agreement among the panelists and weights associated with the panelists that highlight the extent to which they agree with the general point of view. These weights are used to compute an average group configuration, which is submitted to Correspondence Analysis to derive a perceptual product map. Here, CATATIS is extended to situations where the data are not binary. In particular, we focus on the case of data from a CATA experiment with repetitions and data from a Rate‐All‐That‐Apply (RATA) experiment. Furthermore, a hypothesis‐testing framework based on permutations is set up to assess the significance of the weights associated with the panelists. Finally, the general strategy of analysis is illustrated using data from real case studies pertaining to CATA and RATA experiments.Practical ApplicationsEvaluating panel performance is often important in sensory studies, especially in industrial contexts. While many professionals are familiar with evaluating the outputs of conventional descriptive analysis, the increasing adoption of rapid sensory methods calls for methods and tools tailored to different sensory tasks. Our paper introduces an approach (CATATIS) to enhance the interpretation of the outputs of CATA and RATA tasks, focusing on attribute consistency, overall panel agreement, and individual weights associated with panelists. The approach is demonstrated through concrete case studies. CATATIS, together with its extensions, are available in XLSTAT software and in the R package ClustBlock.

Feasibility of dose calculation for treatment plans using electron density maps from a novel dual-layer detector spectral CT simulator

BackgroundConventional single-energy CT can only provide a raw estimation of electron density (ED) for dose calculation by developing a calibration curve that simply maps the HU values to ED values through their correlations. Spectral CT, also known as dual-energy CT (DECT) or multi-energy CT, can generate a series of quantitative maps, such as ED maps. Using spectral CT for radiotherapy simulations can directly acquire ED information without developing specific calibration curves. The purpose of this study is to assess the feasibility of utilizing electron density (ED) maps generated by a novel dual-layer detector spectral CT simulator for dose calculation in radiotherapy treatment plans.Methods30 patients from head&neck, chest, and pelvic treatment sites were selected retrospectively, and all of them underwent spectral CT simulation. Treatment plans based on conventional CT images were transplanted to ED maps with the same structure set, including planning target volume (PTV) and organs at risk (OARs), and the dose distributions were then recalculated. The differences in dose and volume histogram (DVH) parameters of the PTV and OARs between the two types of plans were analyzed and compared. Besides, gamma analysis between these plans was performed by using MEPHYSTO Navigator software.ResultsIn terms of PTV, the homogeneity index (HI), gradient index (GI), D2%, D98%, and Dmean showed no significant difference between conventional plans and ED plans. For OARs, statistically significant differences were observed in parotids D50%, brainstem in head&neck plans, spinal cord in chest plans and rectum D50% in pelvic plans, whereas the variance remained minor. For the rest, the DVH parameters exhibited no significant difference between conventional plans and ED plans. All of the mean gamma passing rates (GPRs) of gamma analysis were higher than 90%.ConclusionCompared to conventional treatment plans relying on CT images, plans utilizing ED maps demonstrated similar dosimetric quality. However, the latter approach enables direct utilization in dose calculation without the requirements of establishing and selecting a specific Hounsfield unit (HU) to ED calibration curve, providing an advantage in clinical applications.

Non-close-packed plasmonic Bravais lattices through a fluid interface-assisted colloidal assembly and transfer process

AbstractThe assembly of colloids at fluid interfaces followed by their transfer to solid substrates represents a robust bottom-up strategy for creating colloidal monolayers over large, macroscopic areas. In this study, we showcase how subtle adjustments in the transfer process, such as varying the contact angle of the substrate and controlling deposition speed and direction, enable the realization of all five two-dimensional Bravais lattices. Leveraging plasmonic core–shell microgels as the building blocks, we successfully engineered non-close-packed plasmonic lattices exhibiting hexagonal, square, rectangular, centered rectangular, and oblique symmetries. Beyond characterizing the monolayer structures and their long-range order, we employed extinction spectroscopy alongside finite difference time domain simulations to comprehensively investigate and interpret the plasmonic response of these monolayers. Additionally, we probed the influence of the refractive index environment on the plasmonic properties by two methods: first, by plasma treatment to remove the microgel shells, and second, by overcoating the resulting gold nanoparticle lattices with a homogeneous refractive index polymer film. Graphical Abstract

Effect of Different Dose Rates on Dosimetric Parameters and Accuracy of the Pretreatment Quality Assurance During Intensity-modulated Radiotherapy Planning Using Anthropomorphic Phantom

Background: This study investigates the impact of varying dose rates on dosimetric parameters and pretreatment quality assurance (QA) accuracy in intensity-modulated radiotherapy (IMRT) planning using anthropomorphic phantoms. The research explores the dosimetric effects of different dose rates ranging from 100 to 600 monitor units per minute (MU/min) on parameters such as Homogeneity Index (HI), Conformity Index (CI), and dose to organs at risk (OAR). Method: Anthropomorphic phantoms, mimicking human tissues, were employed for simulation. Treatment plans were generated using the Eclipse Treatment Planning System, and dosimetric evaluations were conducted using cumulative dose-volume histograms (DVH). Furthermore, pretreatment patient-specific QA was performed using EPID portal dosimetry and Delta4 dosimetry system. Result: Treatment plans adhere to institutional protocol, ensuring the target receives ≥95% of the prescription dose while meeting OAR constraints. All plans maintain target homogeneity and conformality, keeping maximum doses within the target below 107%. Low dose plans exhibit superior target coverage, conformality, and homogeneity compared to higher doses. However, increased dose rates elevate delivered Monitor Units and maximum doses to critical structures. Gamma passing rates vary with dose rates, with the lowest at 100 MU/min and the highest at 400 MU/min for 1% 1mm criteria. Dosimetric evaluations using Delta 4 and EPID QA methods confirm plan validity across different dose rates. Conclusion: Low dose rate dosimetry is superior to higher rates for target and organ-at-risk (OAR) delivery, albeit prolonging delivery time and affecting internal organ motion. Portal dosimetry offers a faster, more convenient tool for IMRT pretreatment quality assurance (QA). Optimal results are achieved at 400 MU/min, enhancing gamma agreement between calculated and measured portal doses for complex fields. This improvement in QA enhances IMRT treatment delivery quality. However, patient-specific QA using the DELTA4 dosimetry system and ICRU 83 recommendations are insufficient for discussing dosimetric differences relevant to patient treatment.

Prediction of Radiation Therapy Dose Distribution Using Random Forest Algorithm in Volumetric Modulated Arc Therapy Technique for Brain Cancer

Optimization of radiation dose distribution in clinical planning using a Treatment Planning System (TPS) for radiotherapy patients is crucial to achieving a balance between therapeutic effectiveness and patient safety. However, this process is time-consuming and relies heavily on the expertise of medical physicists. In this study, dose prediction using machine learning was performed on the Planning Target Volume (PTV) and Organ at Risk (OAR) for brain cancer cases using the Volumetric Modulated Arc Therapy (VMAT) planning technique. The planning DICOM data were extracted for radiomic and dosiomic values, which were then used as input and output in this study using a random forest algorithm model. Model evaluation results indicated that the random forest model's performance in predicting dose had a Mean Square Error (MSE) value of 0.018. The Homogeneity Index (HI) and Conformity Index (CI) values for the clinical data were 0.136±0.134 and 0.939±0.131 respectively, while the predicted results were 0.136±0.039 and 0.949±0.006, with p-values for PTV and OAR features &gt; 0.05. Thus, it can be concluded that the random forest model is effective in predicting dose for PTV brain cancer and OAR and can function as a reference in the planning process.

Characteristics of plankton community structure and applicability of biomanipulation in midstream of the Jialing River—the biggest tributary of the Yangtze River

Plankton, as an important part of the food chain in the river ecosystem, is sensitive to changes in the environment. To investigate the influence of plankton community structure on the aquatic ecosystem and further verify the applicability of biomanipulation, the midstream of the Jialing River was selected as the study area. A total of 149 species (varieties) from 7 phyla, 18 orders, 34 families, and 72 genera were identified for phytoplankton. A total of 48 species were found for zooplankton. The mean density of phytoplankton was 2.09 × 106 cells/L, and the mean density of zooplankton was 27.1 ind./L. Moreover, the mean values of the Shannon–Wiener diversity index (H′), Pielou homogeneity index (J′), and Margalef abundance index (D) for phytoplankton were 3.17, 0.76, and 4.47, respectively. The mean values of the Shannon–Wiener diversity index (H′), Pielou homogeneity index (J′), and Margalef abundance index (D) for zooplankton were 2.64, 0.92, and 5.07, respectively. Based on the diversity indices, the water quality was evaluated as oligo pollution to β-medium pollution level. Redundancy analysis (RDA) was used to explore the relationship between dominant plankton species and environmental factors. The RDA results show that the main environmental factors affecting the community structure of phytoplankton and zooplankton were water temperature (WT), electrical conductivity (EC), pH, total phosphorus (TP), and transparency (Secchi depth; SD). There were 17 functional groups in phytoplankton, which are X1, S1, Y, Y2, and so on. In zooplankton, there were six functional groups, which are Pmsl, Prsu, Pfif, Pmip, Lrsf and Lmic. Many articles have demonstrated the feasibility of using biological manipulation to control algae. The number of piscivorous fish in the midstream of the Jialing River had increased, and phytoplankton density in this survey was significantly decreased. The results show that traditional biomanipulation can be applied to this region, which can provide better scientific support for the future management of the aquatic environment in the Jialing River basin.