Homogeneity Index Research Articles

Evaluation of Dynamic Multi-Leaf Collimator (MLC) versus Fixed MLC for Intensity Modulated Radiotherapy (IMRT) Using the Agility 160-Leaf Collimator.

This study aimed to evaluate the efficacy of static or step-and-shoot intensity-modulated radiotherapy (ssIMRT) and dynamic intensity-modulated radiotherapy (dIMRT) delivery techniques for various treatment sites. The treatment planning system (TPS) was utilized to develop optimal treatment plans for twenty-seven patients selected for this comparative study, including nine with head and neck cancer, nine with prostate cancer, and nine with cervical cancer. The prescribed doses were 7000cGy/33fr, 7425cGy/33fr, and 5000cGy/25fr for the nasopharynx, prostate, and cervix cases, respectively, in both ssIMRT and dIMRT delivery techniques. Plans were generated using the Monaco treatment planning system with a 6MV photon beam and nine equidistant fields. Plan evaluation criteria included dose-volume histogram analysis, dose homogeneity index, conformity index, radiation delivery time, and monitor unit requirements. All plans were optimized to ensure that 98% of the planning target volume (PTV) received at least 95% of the prescribed dose, while meeting the planning objectives for organs at risk. dIMRT plans exhibited superior conformity (CI = 0.85 ± 0.05) compared to ssIMRT plans (CI = 0.79 ± 0.08), with statistically significant differences (P < 0.01). Inhomogeneity within the PTV was significantly higher in ssIMRT plans (HI = 0.10 ± 0.02) compared to dIMRT plans (HI = 0.09 ± 0.01), with a significant difference (P < 0.01). Delivery time per fraction was significantly lower in dIMRT compared to ssIMRT (P < 0.01). Furthermore, dIMRT plans required a higher mean monitor unit value (1335.4 ± 172.2) compared to ssIMRT plans (974.4 ± 133.6) with a significant difference (P < 0.001). The findings of this study indicate that dIMRT provides improved target coverage, homogeneity, and conformity while reducing treatment delivery time compared to ssIMRT.

Individualized 3D-printed applicators for magnetic resonance imaging-guided brachytherapy in nasal vestibule cancer

Background and purposeBrachytherapy is treatment of choice for early stage nasal vestibule cancer. Over the years improvements were achieved by means of image guided target definition, interstitial implant techniques and also individual mold techniques. The aim of this study was to improve the technique of the implant so that the need for interstitial catheters can be limited by making use of patient individualized 3D-printed applicators. Materials and MethodsIn 19 patients 3D-printed applicators were used to deliver pulse dose rate (PDR) brachytherapy. All patients underwent computed tomography (CT) and magnetic resonance imaging (MRI). A pre-plan with tumor delineation and manually optimized catheter positions to achieve tumor coverage was made. Based on the pre-plan a 3D-printed applicator was manufactured. Dose was evaluated by several indices: Conformity Index, Healthy Tissues Conformity Index, Dose Homogeneity Index, Dose non-uniformity ratio, Conformal index and high dose (HD) index. ResultsA high target coverage was achieved, with a median V100%CTV of 99.1 % (range, 81.8–100 %) and median CI of 0.99 (range, 0.82–1.00), as well as a median V0.7GyGTV of 100 % (range, 93.0–100 %). The median HD was 0.39 (range, 0.20–0.83). Interstitial catheters were needed in 12 patients. None of the patients developed grade ≥ II toxicity within the median follow up of 18 months. ConclusionsThis study shows that using 3D-printed applicators limits the need for interstitial catheters and also limits the high doses in normal tissue.

Prevalence of Rotifers in the Tigris River before and after the Al Kut Dam /Iraq

A study was conducted to analyze the makeup of the rotifera community in terms of both quantity and quality. The study took place over four seasons at two locations on the Tigris River, both before and after the construction of Al-Kut's Barrage. The study period spanned from January to December 2023, during which a total of 48 taxonomic units of rotifera were discovered. The overall population density of the Rotifera at the initial location prior to Al-Kut's Barrage varied between the peak value of 10509.9 individuals/m3 in the spring and the minimum value of 2621.1 individuals/m3 in the winter. The second location downstream of Al-Kut's Barrage had a peak density of 5198.8 persons per cubic meter during spring, while the lowest density of 1088.3 individuals per cubic meter was seen during winter. The study examined the indicators of relative abundance and the Shannon-Wienercoefficient of biological diversity. The values observed ranged from 2.198 to 6542 bits per individual. The index of species appearance homogeneity ranged from 0.67 to 0.85, and the index of species abundance ranged from 5.25 to 7.89. The decline in the population of Rotifera during winter is attributed to the adverse impact of cold temperatures, which hampers the restricted growth of the species. During the winter season, there is a reduction in illumination and phytoplankton, resulting in a fall in food availability. This shortage of food is responsible for the decline in Rotifera populations.

Reproductive qualities of French selection of the White Large breed of sows and their evaluation according to some mathematical models

Objective. To investigate the reproductive qualities of sows of the large white breed of French selection and to evaluate the indicated group of traits according to some mathematical models of selection indices. Methods. Zootechnical and statistical research methods were used to achieve the goal. The experimental part of the work was carried out in the breeding breeder for breeding pigs of the large white breed of the experimental farm of the Institute of Agriculture of the Northeast of the National Academy of Sciences. The assessment of sows of the large white breed of French breeding was carried out according to the indicators of reproductive qualities, taking into account the following quantitative characteristics: multifertility, goal, high fertility, kg; milk yield, kg; the number ofpiglets at the time of weaning, goal; nest weight at the time of weaning at the age of 28 days, kg; nest weight at the time of weaning at the age of 60 days, kg; preservation, %. A comprehensive evaluation of sows for reproductive qualities was carried out using the selection index of reproductive qualities of the sow (SIRQS) (Tsereniuk O. M. et al., 2010) and the index of Shatalina Yu. D. (Vashchenko P. A., 2019). Biometric research results were processed according to generally accepted methods (Kovalenko V. P. et al., 2010). Results. Studies have shown that sows of experimental group I prevailed over sows of the same age in groups II and III in terms of multifertility by 15.67 and 34.32 %, milk yield - 23.29 and 34.94 %, number of piglets at the time of weaning at the age of 28 days - 13.91 and 33.30 %, by the weight of the nest at the time of weaning at the age of 28 days - 17.39 and 27.60 %, by the weight of the nest at the time of weaning at the age of 60 days - 17.89 and 28.30 %. The difference between the animals of the I, II, and III experimental groups (intrabreed differentiation according to the index of Shatalina Yu. D.) in terms offertility, milk yield, the number ofpiglets at the time of weaning at the age of 28 days, the weight of the litter at the time of weaning at the age of 28 days and the weight of the litter at the time of weaning at the age of 60 days is highly reliable and is equal to 23.58 %. The maximum indicators of high fertility and survival ofpiglets at the time of weaning at the age of 28 days and the minimum values of the sow nest alignment (homogeneity) index based on the live weight of piglets at the time of their birth (IVH0) were established in sows of the III sub-experimental group of intrabreed differentiation according to SIRQS and the index of Shatalina Yu. D. Conclusions. Sows of the large white breed of French breeding are characterized by pretty high indicators of reproductive qualities, and in terms offertility and litter weight at the time of weaning at the age of 60 days, they belong to the 1st class and the elite class. The number of reliable pairwise correlation coefficients between the absolute indicators o f reproductive qualities of sows, SIRQS, the index of Shatalina Yu. D. and the index of evenness (homogeneity) of the sow's nest according to the live weight ofpiglets at the time of their birth (IVH0) is 100 %. This indicates a high level of efficiency of their use for evaluation and selection of highly productive animals in controlled populations. Keywords: sow, breed, reproductive qualities, index, variability, correlation.

125I seed implantation for lymph node metastasis from radioactive iodine-refractory differentiated thyroid carcinoma: a study on short-term efficacy and dosimetry.

To investigate the feasibility and evaluate the safety and effectiveness of Computed Tomography (CT) guided125I radioactive particle implantation for treating lymph node metastases in radioiodine-refractory differentiated thyroid cancer (RAIR-DTC). To verify the accuracy of the computerized three-dimensional treatment planning system (TPS) in treating lymph node metastasis using125I particle implantation at the dosimetric level. A retrospective analysis was conducted on 42 patients with RAIR-DTC and lymph node metastases who were admitted to the General Hospital of the Northern Theater Command between December 2016 and January 2019. During this analysis, physicians utilized preoperative CT images to design an intraoperative plan using TPS. The dosimetric parameters of the postoperative plan were then compared to the preoperative plan. Additionally, this study examined the changes in tumor size and tumor-related marker Thyroglobulin (Tg) values in patients at 2, 6, and 12 months after the operation. The number of125I radioactive particles implanted in 42 patients was 226, with an average of 14.5 (range 2.0-30.0) particles implanted per lesion. The local remission rates were 97.62% (41/42), 88.10% (37/42), and 85.71% (36/42) at 2, 6, and 12 months postoperatively, respectively. The volume of the lesions was (4.44 ± 1.57) cm3, (4.20 ± 1.70) cm3, and (4.23 ± 1.77) cm3at 2, 6, and 12 months after treatment, respectively, which significantly decreased from the preoperative baseline level of (6.87 ± 1.67) cm3(t-values: 9.466, 9.923, 7.566, all P<0.05). The Tg levels were 15.95 (5.45, 73.93) μg/L, 8.90 (2.20, 39.21) μg/L, and 6.00 (1.93, 14.18) μg/L at 2, 6, and 12 months after treatment, respectively, which were significantly lower than the preoperative baseline levels of 53.50 (20.94, 222.92) μg/L (Z values: -5.258, -5.009, -4.987, all P < 0.001). Postoperatively, Delivered to 90% of the GTV(D90) was slightly lower than the prescribed dose in 95.23% (40/42) of patients, but the difference was not statistically significant [(12,378.8 ± 3,182.0), (12,497.8 ± 1,686.4) cGy; t=0.251, P>0.05], and postoperative dose parameters delivered to 100% of the gross tumor volume (GTV)(D100) (6,881.5 ± 1,381.8) cGy, the volume percentages of GTV receiving 150% of the prescribed dose(V150) (58.5 ± 18.40)%) were lower than the preoperative plan D100 (8,085.8 ± 2,330.0) cGy, V150 (66.5 ± 17.70)%; t-value=8.913 and 3.032, both P<0.05; the remaining indicators were not significantly different from the preoperative plan (the differences in the number of implanted particles, Planning Target Volume(PTV), the volume percentages of GTV receiving 100% of the prescribed dose(V100), Homogeneity Index(HI)were not statistically significant (t/Z = -0.593, -1.604, 1.493, -0.663, all P>0.05). Referring to the TPS preoperative plan, the125I particle implantation therapy for RAIR-DTC lymph node metastasis can achieve the expected dose distribution, ensuring precise short-term local tumor control efficacy.

Comparison of Lung and Contralateral Scattered Breast Dose between Field-in-Field and Wedge Techniques in Patients with Early Breast Cancer

Purpose: This study aims to evaluate the dosimetric result of the Field-In-Field (FIF) plans compared with Tangential Wedged Beams (TWB) plans for whole breast radiotherapy of patients. Materials and Methods: In this survey, we entered fifty patients with breast-conserving surgery and postoperative whole-breast radiotherapy. FIF and a TWB plan were made for each patient to compare dosimetric outcomes. Results: The Homogeneity Index (HI) and Conformity Index (CI) were specified for the evaluation of Planning Target Volume (PTV). The mean dose of the ipsilateral lung and contra-lateral breast for the evaluation of organs at risk dose were used. The FIF plans had significantly lower HI (p &lt; 0.01) and CI (p &lt; 0.01) than those of the TWB plans. It means in the dosimetric comparisons of the PTV, the FIF plans were better than the TWB plans. The V10lung (31.152vs. 32.72%, p &lt; 0.01), V20lung (25.6064vs. 26.6%, p &lt; 0.01) V30lung (17.4% vs. 18.4%, p &lt; 0.01) were lower with the FIF plans compared with those of the TWB plans, with statistical significance. The FIF plans had a lower mean dose for the lung than those of TWB plans (1225.48 vs. 1670.32 cGy) but no statistical significance (p=0.06). The mean dose in the contra-lateral of the breast in FIF plans was lower than in TWB plans (61.666 vs. 163.45 cGy), with statistical significance (p &lt; 0.01). Conclusion: The FIF plans increased the dose homogeneity, and conformity of the target volume for the whole-breast irradiation compared with the TWB plans. Moreover, the doses of organs at risk (ipsilateral lung and contralateral breast) were reduced with FIF plans.

Safety and Feasibility of Hippocampal Sparing Cranial Radiation in Pediatric and Adolescent Acute Lymphoblastic Leukemia Patients: A Prospective Study.

Introduction Acute lymphoblastic leukemia (ALL) constitutes a significant portion of pediatric malignancies, with central nervous system (CNS) relapse posing a considerable threat to patient outcomes. While cranial radiation therapy (CRT)has been utilized to mitigate CNS relapse, it is associated with neurocognitive (NC) side effects. This study explores the feasibility and safety of using volumetric arc therapy (VMAT) with hippocampal sparing (HS) during cranial radiation therapy for ALL patients, aiming to reduce these side effects. Methodology This prospective observational study included pediatric and young adult patients with ALL who werein remission. HS was achieved using VMAT, and NC assessments were performed at baseline, six months, one year, and, to a limited extent, four years posttreatment. Results VMAT enabled precise hippocampal-sparing CRT with minimal dose to the hippocampus. Dosimetric analysis revealed that patients receiving 18 Gy had mean doses to planning target volume (PTV) and bilateral hippocampus of 18.9 and 9 Gy, respectively. Those receiving 12 Gy had corresponding doses of 13.3 and 7 Gy, respectively. Conformity and homogeneity indices were 0.9 and 0.1, and no brain relapses were observed among the patients in this study. NC assessments demonstrated no decline in intelligence quotient (IQ) scores over time, while only a subset of patients could be assessed at the four-year mark; telephone interviews suggested no significant cognitive decline. Conclusions This study highlights the potential of VMAT with HS as a promising approach to CRT for ALL patients in reducing the risk of NC side effects. The absence of brain relapses and preservation of NC function are encouraging findings, though larger studies are necessary to establish conclusive evidence.

Short course irradiation in rectal cancer: Dosimetry study comparing 3D conformal radiotherapy versus intensity-modulated radiotherapy versus volumetric modulated arc therapy

The standard radiotherapy planning technique for locally advanced rectal cancer (LARC) was 3D Conformal Radiotherapy (3DCRT). Modern radiation delivery techniques, including Intensity-Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) techniques, have been developed in recent years in terms of dose delivery to the target while minimizing the dose to the organ at risk (OAR). The objective of this study was to identify the most suitable treatment plan technique from the available options of 3DCRT, IMRT and VMAT for LARC using short course radiotherapy (SCRT). Therefore, twenty-five adult patients with LARC in the last five-year period (2017–2021) were involved in this study. For each patient, three radiotherapy treatment plans were generated for dosimetric comparison of short course irradiation (25 Gy/5 fractions, which is the new standard of care) using Varian Eclipse software to generate 3DCRT in comparison with IMRT and VMAT plans. The conformity index (CI), the homogeneity index (HI), and the organs at risk (OAR), including bladder, small bowel, and femoral heads, were compared between the three plans. The results revealed that VMAT and IMRT plans had a higher level of conformity for the planning target volume (PTV) with 0.996 and 0.994, respectively, compared to the 3DCRT planning of 0.947 (both p < 0.005). The PTV dose distribution was less homogeneous with 3DCRT than with VMAT or IMRT plans. VMAT offered superior homogeneity to IMRT and 3DCRT plans with 1.055, 1.066, and 1.089, respectively (p < 0.005). The findings showed that VMAT is superior to IMRT and 3DCRT in almost all parameters, including dose distribution conformity and homogeneity of the target volume, as well as providing better OAR sparing in LARC patients.

Life cycle water and energy consumption and efficiency analysis of major crops in China

Water and energy are key elements in food production. However, only a few studies have investigated water and energy consumption simultaneously in a crop cultivation life cycle. In this study, we established a bottom–up framework to explore water and energy consumption in each period of the crop growth process, including sowing, germination, growth, maturation, and harvesting. We propose a novel homogenization index, the Water–Energy Efficiency for Food (WEEF) index, to compare crop production efficiency by reasonably eliminating regional location effects. Changes in water and energy consumption were evaluated for six major crops in China, including wheat, maize, rice, soybean, peanut, and cotton. The results showed that the water and energy consumption during the main growth period were largely synchronized in most regions, with peak periods occurring in July–August and May–June. Owing to the increased use of agricultural machinery and irrigation energy, the total energy consumption per unit yield of cotton, maize, and rice increased by 28%, 19%, and 16%, respectively, in 2018 compared with 2012, reaching 25.81, 2.53, and 2.49 MJ/kg, respectively. The WEEF index revealed that the efficiency of wheat and soybean production in China surpassed that of other crops. In general, the average crop production efficiency in the northern region was about 4％ lower than that in the southern region. Implementing spatiotemporal refined water and energy management strategies is imperative to attain sustainable agricultural development.

The effect of auto-planning parameter settings on the quality of automated cervical cancer plans

PurposeThis study refines the parameters of automatic planning to improve plan quality and enhance the protection of organs at risk (OARs). Materials & methods30 cases of cervical cancer underwent manual (M-VMAT) and automated VMAT planning. The automated planning used five parameters: Engine Type (Biological and Non-Biological) and Use Cold-Spot ROIs (Yes and No) were qualitative; Tuning Balance (1–100%, default: 11%), Dose Fall-off Margin (1.0–4.5 cm, default: 2.6 cm), and Hot-Spot Maximum Goal (101–110%, default: 107%) were quantitative. The original automated plans (A1-VMAT) utilized default parameters, while the adjusted automated plans (A2-VMAT) utilized modified parameters. Dosimetric parameters and plan complexities were compared among M-VMAT, A1-VMAT, and A2-VMAT. ResultsCompared to M-VMAT, the A1-VMAT underperformed in protecting OARs. However, the A2-VMAT effectively addressed this issue. When adjusting “Use Cold-Spot ROIs” to “No”, “Tuning Balance” to 100%, and “Hot-Spot Maximum Goal” to 110%, while keeping the remaining parameters at their default settings, A2-VMAT significantly improved OAR protection in this study. Compared to A1-VMAT, the A2-VMAT showed only a slight increase in bowel's Dmax (approximately 2.11%, P < 0.05), while various OARs achieving significant dose reductions. Notably, there were significant reductions (over 30%, P < 0.05) in V35, V40 of rectum, V25, V30, V35 of femoral heads, and V10, V15, V20 of kidney. Furthermore, the efficacy of these five parameters was also observed in this study. Except for Engine Type, adjustments to the other parameters impacted Conformity Index, Homogeneity Index, and maximum dose (Dmax) for the PTV. Engine Type affected the average dose to OARs, and Hot-Spot Maximum influenced the Dmax for OARs overlapping with the PTV. ConclusionThe adjusted automated plan improved plan quality compared to the original automated plan, enhancing OAR protection. The adjusted plan demonstrated lower complexity than the manual plan.

Robot base position and spacecraft cabin angle optimization via homogeneous stiffness domain index with nonlinear stiffness characteristics

The use of mobile robots for machining large components has received considerable research interest for the application of industrial robots in the machinery manufacturing sector. However, the low structural stiffness of industrial robots can result in poor machining quality under the action of cutting forces. Therefore, this paper proposes a simultaneous optimization method the mobile robot base position and cabin angle using homogeneous stiffness domain (HSD) index for large spacecraft cabins. First, a nonlinear joint stiffness model that considers the gravity compensator mechanism is established to describe the stiffness characteristics of heavy-duty robots more accurately. Subsequently, a HSD index is proposed to evaluate the overall stiffness values and stiffness fluctuation for all robot postures in the machining program. An optimization model is then established based on the HSD under the constraints of machining accessibility, joint angle limitation and singularity. The optimal base position and cabin angle are determined simultaneously using the sparrow search algorithm. Finally, simulation and milling experiments are used to demonstrate that the optimization method proposed in this paper can effectively improve the machining quality.

Using dose volume histogram (DVH) predictions to improve the plan quality of helical tomotherapy (HT)

This study aimed to investigate whether the RapidPlan (RP) model configured by volumetric modulated arc therapy (VMAT) plans of nasopharyngeal carcinoma (NPC) could be used to assist in the optimization of HT plans and improve their quality.An RP model was trained using 100 clinically accepted VMAT plans of NPC patients. The predicted dose constraints of the VMAT trained RP model were used to reoptimize 25 consecutive clinically accepted HT plans (HT_clinical) and perform new VMAT plans based on the same computed topography (CT). The dosimetric quality of the reoptimized HT plans (HT_reoptimized), HT_clinical, and VMAT group were compared. The minimum dose encompassing 2% target (D2%), the minimum dose encompassing 98% target (D98%), homogeneity index (HI) and conformity index (CI) were similar for most targets between the HT_clinical and HT_reoptimized plans, although certain targets in the HT_reoptimized plans had higher D2% and HI and lower D98%. The HT_reoptimized plans outperformed the HT_clinical plans in the Dmax and D1cc of the spinal cord, V40Gy of the left temporal lobe, Dmean and V30Gy of the oral cavity, Dmean of the larynx and thyroid, and the differences were statistically significant. HT plans had higher CI and HI than VMAT plans. HT plans outperformed VMAT plans in the Dmax of the spinal cord and lenses, V30Gy of the oral cavity and parotids, and V40Gy of the temporal lobes, but underperformed in the Dmax and D1cc of the brainstem, D1cc of the spinal cord and Dmean of the oral cavity.The VMAT-based RP model can be used to assist in the planning of HT plans and improve the dosimetry quality of HT plans.

Helical tomotherapy was superior to intensity-modulated radiation therapy in hippocampal avoidance prophylactic cranial irradiation in patients with limited-stage small-cell lung cancer.

e20099 Background: Hippocampal avoidance (HA) techniques have been developed to reduce the risk of neurocognitive dysfunction associated with prophylactic cranial irradiation (PCI) in patients with limited-stage small-cell lung cancer (LS-SCLC). However, applying different radiotherapy techniques to HA has not yet been further analyzed. This study discussed the dosimetric differences between intensity-modulated radiation therapy (IMRT) and helical tomotherapy (TOMO) in HA-PCI and analyzed the benefit of the dosimetric advantage in the risk of brain metastasis (BM) from a clinical perspective. Methods: We retrospectively evaluated patients who underwent PCI from June 2020 to December 2021 at Shandong Cancer Hospital. They were divided according to hippocampal avoidance and radiotherapy techniques: IMRT without HA (non-HA-IMRT), HA-IMRT, and HA-TOMO. The cumulative incidence of BM, target coverage (TC), homogeneity index (HI), conformity index (CI), and hippocampal doses of these radiotherapy programs were evaluated. Results: One hundred seventy-two patients were included in the analysis: 56, 78, and 38 patients in the non-HA-IMRT, HA-TOMO, and HA-IMRT groups, respectively. The 2-year cumulative incidence of BM was 31.4% in patients with HA (78 patients in the HA-TOMO group and 38 patients in the HA-IMRT group) and 23.2% in patients without HA (hazard ratio [HR]: 0.75, 95% confidence interval [95% CI]: 0.43-1.31; P= 0.340). However, the 2-year cumulative incidence of BM was lower in the HA-TOMO group than in the HA-IMRT group (25.0% vs. 44.7%, HR: 0.51, 95% CI: 0.26-0.99; P= 0.029). Both techniques achieved hippocampal protection, but HA-TOMO accomplished significantly better TC (96.24%±0.65% vs. 93.75%±2.45%, P&lt; 0.001), HI (0.09±0.02 vs. 0.27±0.12, P&lt; 0.001), and CI (0.88±0.02 vs. 0.85±0.04, P&lt; 0.001). Conclusions: HA-PCI did not increase BM risk. Additionally, HA-TOMO could achieve better TC, HI, and CI with respect to the planned tumor in the brain while achieving more rapid dosing in the hippocampal region. The cumulative incidence of BM was lower with HA-TOMO than with HA-IMRT.

Exploring and Predicting Landscape Changes and Their Driving Forces within the Mulan River Basin in China from the Perspective of Production–Living–Ecological Space

With rapid economic development and urban expansion, China faces a serious imbalance between production, living, and ecological land use, in which the erosion of water ecological space by urban expansion is especially notable. In order to alleviate or solve this imbalance, this study constructs the water ecological space in the Mulan River Basin based on national land spatial planning using remote sensing statistics and the 2000–2020 statistical yearbooks for the Mulan River Basin. A landscape index is applied to explore this landscape in terms of its production–living–ecological space (PLES) patterns and evolutionary characteristics. Factors affecting the drivers of PLES changes are analyzed through Geo-Detector, and predictions are made using the cellular automata Markov (CA-Markov) model. It was found that (1) PLES distribution patterns in the Mulan River Basin from 2000 to 2020 are dominated by non-watershed ecological spaces, with a significant expansion of living space. Its ecological space is shrinking, and there is significant spatial variation between its near-river and fringe areas. (2) Of the PLES conversions, the most dramatic conversions are those of production space and living space, with 81.14 km2 of production space being transferred into living space. Non-water ecological space and water ecological space are also mainly transferred into production space. (3) As shown by the results of the landscape index calculation, non-water ecological space in the Mulan River Basin is the dominant landscape, the values of the Shannon diversity index (SHDI) and Shannon homogeneity index (SHEI) are small, the overall level of landscape diversity is low, the aggregation index (AI) is high, and the degree of aggregation is obvious. (4) The progressive PLES changes in the Mulan River Basin are influenced by a combination of natural geographic and socioeconomic factors, with the mean population density and mean elevation being the most important factors affecting PLES changes among social and natural factors, respectively. (5) The Kappa coefficient of the CA-Markov model simulation is 0.8187, showing a good simulation accuracy, and it is predicted that the area of water ecological space in the Mulan River Basin will increase by 3.66 km2 by 2030, the area of production space and non-water ecological space will further decrease, and the area of construction land will increase by 260.67 km2. Overall, the aquatic ecological space in the Mulan River Basin has made progress in terms of landscape ecological protection, though it still faces serious erosion. Therefore, attaching importance to the restoration of the water ecological space in the Mulan River Basin, integrating multiple elements of mountains, water, forests, fields, and lakes, optimizing the spatial structure of its PLES dynamics, and formulating a reasonable spatial planning policy are effective means of guaranteeing its ecological and economic sustainable development. This study offers recommendations for and scientific defenses of the logical design of PLES spatial functions in the Mulan River Basin.

The clinical practice and dosimetric outcome of the manual adaptive planning during definitive radiotherapy for cervical cancer

ProposeTo evaluate the advantage of the manual adaptive plans comparing to the scheduled plans, and explored clinical factors predicting patients suitable for adaptive strategy.Methods and materialsEighty two patients with weekly online cone-beam computed tomography (CBCT) were enrolled. The re-CT simulation was performed after 15 fractions and a manual adaptive plan was developed if a significant deviation of the planning target volume (PTV) was found. To evaluate the dosimetric benefit, D98, homogeneity index (HI) and conformity index (CI) for the planning target volume (PTV), as well as D2cc of the bowel, bladder, sigmoid and rectum were compared between manual adaptive plans and scheduled ones. The clinical factors influencing target motion during radiotherapy were analyzed by chi-square test and logistic regression analysis.ResultsThe CI and HI of the manual adaptive plans were significantly superior to the scheduled ones (P = 0.0002, 0.003, respectively), demonstrating a better dose coverage of the target volume. Compared to the scheduled plans, D98 of the manual adaptive plans increased by 3.3% (P = 0.0002), the average of D2cc to the rectum, bladder decreased 0.358 Gy (P = 0.000034) and 0.240 Gy (P = 0.03), respectively. In addition, the chi-square test demonstrated that age, primary tumor volume, and parametrial infiltration were the clinical factors influencing target motion during radiotherapy. Multivariate analysis further identified the large tumor volume (≥ 50cm3, OR = 3.254, P = 0.039) and parametrial infiltration (OR = 3.376, P = 0.018) as the independent risk factors.ConclusionWe found the most significant organ motion happened after 15 fractions during treatment. The manual adaptive plans improved the dose coverage and decreased the OAR doses. Patients with bulky mass or with parametrial infiltration were highly suggested to adaptive strategy during definitive radiotherapy due to the significant organ motion.

Dosimetric comparison of HyperArc and InCise MLC-based CyberKnife plans in treating single and multiple brain metastases.

This study aimed to compare the dosimetric attributes of two multi-leaf collimator based techniques, HyperArc and Incise CyberKnife, in the treatment of brain metastases. 17 cases of brain metastases were selected including 6 patients of single lesion and 11 patients of multiple lesions. Treatment plans of HyperArc and CyberKnife were designed in Eclipse 15.5 and Precision 1.0, respectively, and transferred to Velocity 3.2 for comparison. HyperArc plans provided superior Conformity Index (0.91±0.06vs. 0.77±0.07, p<0.01) with reduced dose distribution in organs at risk (Dmax, p<0.05) and lower normal tissue exposure (V4Gy-V20Gy, p<0.05) in contrast to CyberKnife plans, although the Gradient Indexes were similar. CyberKnife plans showed higher Homogeneity Index (1.54±0.17vs. 1.39±0.09, p<0.05) and increased D2% and D50% in the target (p<0.05). Additionally, HyperArc plans had significantly fewer Monitor Units (MUs) and beam-on time (p<0.01). HyperArc plans demonstrated superior performance compared with MLC-based CyberKnife plans in terms of conformity and the sparing of critical organs and normal tissues, although no significant difference in GI outcomes was noted. Conversely, CyberKnife plans achieved a higher target dose and HI. The study suggests that HyperArc is more efficient and particularly suitable for treating larger lesions in brain metastases.

Dosimetric evaluation of different planning strategies for hypofractionated whole-breast irradiation technique

Purpose. The dose hotspot areas in hypofractionated whole-breast irradiation (WBI) greatly increase the risk of acute skin toxicity because of the anatomical peculiarities of the breast. In this study, we presented several novel planning strategies that integrate multiple sub-planning target volumes (sub-PTVs), field secondary placement, and RapidPlan models for right-sided hypofractionated WBI. Methods. A total of 35 cases of WBI with a dose of 42.5 Gy for PTVs using tangential intensity-modulated radiotherapy (IMRT) were selected. Both PTVs were planned for simultaneous treatment using the original manual multiple sub-PTV plan (OMMP) and the original manual single-PTV plan (OMSP). The manual field secondary placement multiple sub-PTV plan (m-FSMP) with multiple objects on the original PTV and the manual field secondary placement single-objective plan (m-FSSP) were initially planned, which were distribution-based of V105 (volume receiving 105% of the prescription dose). In addition, two RapidPlan-based plans were developed, including the RapidPlan-based multiple sub-PTVs plan (r-FSMP) and the RapidPlan-based single-PTV plan (r-FSSP). Dosimetric parameters of the plans were compared, and V105 was evaluated using multivariate analysis to determine how it was related to the volume of PTV and the interval of lateral beam angles (ILBA). Results. The lowest mean V105 (5.64 ± 6.5%) of PTV was observed in m-FSMP compared to other manual plans. Upon validation, r-FSSP demonstrated superior dosimetric quality for OAR compared to the two other manual planning methods, except for V5(the volume of ipsilateral lung receiving 5 Gy) of the ipsilateral lung. While r-FSMP showed no significant difference (p = 0.06) compared to r-FSSP, it achieved the lowest V105 value (4.3 ± 4.5%), albeit with a slight increase in the dose to some OARs. Multivariate GEE linear regression showed that V105 is significantly correlated with target volume and ILBA. Conclusions. m-FSMP and r-FSMP can substantially enhance the homogeneity index (HI) and reduce V105, thereby minimizing the risk of acute skin toxicities, even though there may be a slight dose compromise for certain OARs.

Minimizing normal tissue low dose bath for left breast Volumetric Modulated Arc Therapy (VMAT) using jaw offset.

With proper beam setup and optimization constraints in the treatment planning system, volumetric modulated arc therapy (VMAT) can improve target dose coverage and conformity while reducing doses to adjacent structures for whole breast radiation therapy. However, the low-dose bath effect on critical structures, especially the heart and the ipsilateral lung, remains a concern. In this study, we present a VMAT technique with the jaw offset VMAT (JO-VMAT) to reduce the leakage and scatter doses to critical structures for whole breast radiation therapy. The data of 10 left breast cancer patients were retrospectively used for this study. CT images were acquired on a CT scanner (GE, Discovery) with the deep-inspiration breath hold (DIBH) technique. The planning target volumes (PTVs) and the normal structures (the lungs, the heart, and the contralateral breast) were contoured on the DIBH scan. A 3D field-in-field plan (3D-FiF), a tangential VMAT (tVMAT) plan, and a JO-VMAT plan were created with the Eclipse treatment planning system. An arc treatment field with the x-jaw closed across the central axis creates a donut-shaped high-dose distribution and a cylinder-shaped low-dose volume along the central axis of gantry rotation. Applying this setup with proper multi-leaf collimator (MLC) modulation, the optimized plan potentially can provide sufficient target coverage and reduce unnecessary irradiation to critical structures. The JO-VMAT plans involve 5-6 tangential arcs (3 clockwise arcs and 2-3 counterclockwise arcs) with jaw offsets. The plans were optimized with objective functions specified to achieve PTV dose coverage and homogeneity; For organs at risk (OARs), objective functions were specified individually for each patient to accomplish the best achievable treatment plan. For tVMAT plans, optimization constraints were kept the same except that the jaw offset was removed from the initial beam setup. The dose volume histogram (DVH) parameters were generated for dosimetric evaluation of PTV and OARs. The D95% to the PTV was greater than the prescription dose of 42.56Gy for all the plans. With both VMAT techniques, the PTV conformity index (CI) was statistically improved from 0.62 (3D-FiF) to 0.83 for tVMAT and 0.84 for JO-VMAT plans. The difference in the homogeneity index (HI) was not significant. The Dmax to the heart was reduced from 12.15Gy for 3D-FiF to 8.26Gy for tVMAT and 7.20Gy for JO-VMAT plans. However, a low-dose bath effect was observed with tVMAT plans to all the critical structures including the lungs, the heart, and the contralateral breast. With JO-VMAT, the V5Gy and V2Gy of the heart were reduced by 32.7% and 15.4% compared to 3D-FiF plans. Significantly, the ipsilateral lung showed a reduction in mean dose (4.65-3.44Gy) and low dose parameters (23.4% reduction for V5Gy and 10.7% reduction for V2Gy) for JO-VMAT plans compared to the 3D-FiF plans. The V2Gy dose to the contralateral lung and breast was minimal with JO-VMAT techniques. A JO-VMAT technique was evaluated in this study and compared with 3D-FiF and tVMAT techniques. Our results showed that the JO-VMAT technique can achieve clinically comparable coverage and homogeneity and significantly improve dose conformity within PTV. Additionally, JO-VMAT eliminated the low-dose bath effect at all OARs evaluation metrics including the ipsilateral/contralateral lung, the heart, and the contralateral breast compared to 3D-FiF and tVMAT. This technique is feasible for the whole breast radiation therapy of left breast cancers.

Comparison of plan quality and robustness using VMAT and IMRT for breast cancer

Abstract To evaluate the plan quality and robustness of volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) for breast cancer, 50 patients, including 25 patients who received radiotherapy after breast-conserving surgery (BCR) and 25 patients who received postmastectomy radiotherapy (PRT), were selected for this study. Nominal VMAT and IMRT plans were generated for each patient on Eclipse treatment planning system (version 15.6). The dosimetric metrics, dose distribution, gamma passing rate, and delivery time were compared. In addition, 12 uncertainty plans with plan isocenter uncertainty and CT density uncertainty were recalculated based on the nominal plans for each patient. The dose volume histogram (DVH) band width (DVHBW) was adopted to quantify the plan robustness of the nominal plans for the perturbed scenarios in this study. For BCR, the dosimetric metrics except planning target volume (PTV) conformal index (CI) and ipsilateral lung V 5 were not statistically different for IMRT and VMAT plans. PTV CI of VMAT plans was better than that of IMRT plans (VMAT: 0.923 ± 0.024, IMRT: 0.855 ± 0.032, p = 0.003). The ipsilateral lung V 5 of VMAT plan was higher than that of IMRT plan (VMAT: 42.4% ± 2.8%, IMRT: 40.5% ± 4.0%, p = 0.045). The VMAT plans save more than 1.20 min compared to the IMRT plans (VMAT: 0.87 min, IMRT: 2.08 min, p &lt; 0.001). The gamma passing rates of VMAT plans were better than those of IMRT plans (3 mm/3%, VMAT: 99.7% ± 0.2%, IMRT: 99.4% ± 0.4%, p &lt; 0.001; 2 mm/2%, VMAT: 97.2% ± 1.0%, IMRT: 96.9% ± 0.6%, p = 0.108). For PRT, the dosimetric metrics of VMAT plans, including PTV D mean, homogeneity index (HI), CI, and D max of spinal cord, were significantly better than those of IMRT plans. The VMAT plans save more than 45% time compared with IMRT plans (VMAT: 1.54 min, IMRT: 2.81 min, p &lt; 0.001). The difference in gamma passing rates between VMAT plans and IMRT plans was not statistically significant. For the plan robustness, the DVHBW of VMAT plans and IMRT plans for BCR were 2.09% ± 0.23% and 2.98% ± 0.40%, respectively (p &lt; 0.05). For PRT, the DVHBW of VMAT plans was significantly better than those of IMRT plans (VMAT: 3.05% ± 0.26%, IMRT: 3.57% ± 0.27%, p &lt; 0.05). The results show that the dosimetric metrics of VMAT plans were comparable to those of IMRT plans. More importantly, the VMAT plans had excited dose distribution and fast execution efficiency. The plan robustness of VMAT plans were superior.

HyperArc performance in radiotherapy and its correlations with number and volume of multiple brain metastases

ObjectiveTo assess the performance and advantages of HyperArc for radiotherapy of multiple brain metastases with dosimetric parameters with respect to coplanar volumetric modulated arc radiotherapy (c-VMAT), and characterize implicit correlations between tumor features and dosimetric parameters. MethodsThis retrospective study involved 40 patients with multiple brain metastases (4–16 tumors, 12.8–240.8 cm3) who received simultaneous radiotherapy at the Department of Radiation Oncology, Shenzhen People's Hospital from January 2019 to December 2022. Both HyperArc and c-VMAT plans were designed by the same and qualified physicist using the Eclipse system with Truebeam. A single isocenter and a 6 ​MV flattening filter-free (6FFF) photon beam were used for radiotherapy of multiple brain metastases in each plan. Dosimetric parameters of tumors and organs at risk (OARs) were compared between HyperArc and c-VMAT plans. Correlations between tumor features (number and volume) and dosimetric parameters were revealed and analyzed. Furthermore, monitor units (MUs) of both plan types were recorded to assess rays utilization and delivery efficiency. ResultsCompared to c-VMAT plans, HyperArc plans achieved higher maximum dose (Dmax) (5.23%, t ​= ​7.87, P ​< ​0.01), but lower minimum dose (Dmin) (3.94%, t ​= ​−2.12, P ​= ​0.04) and mean dose (Dmean) (1.05%, t ​= ​−3.29, P < ​0.01) for planning gross tumor volumes (PGTVs). The conformity index (CI), homogeneity index (HI), gradient index (GI) and R50% of PGTVs with HyperArc were better than those with c-VMAT, with the improvements of 20.78%, 1.68%, 19.83% and 36.20%, respectively (P ​< ​0.01). The dosimetric parameters of OARs were significantly improved in HyperArc plans compared to c-VMAT plans. Specifically, the Dmax and the Dmean to the brainstem decreased by 16.14% and 11.37%, respectively. The Dmax for eye_L decreased by 16.88%, for eye_R decreased by 11.67%, for optical nerve_L decreased by 12.56 ​%, and for chiasm decreased by 18.12%. Few correlations were observed between the differences of CI/HI/GI/R50% and the number of PGTVs between the two plan types. Whereas, regression analysis indicated that the differences of CI/ GI/ R50% were negatively correlated with the volume of PGTVs, respectively. Moreover, although HyperArc plans reduced the MUs by 4.74 ​% compared to c-VMAT, no significant difference was observed (P ​> ​0.05). ConclusionsThis study demonstrates the promising performance of HyperArc for radiotherapy of multiple brain metastases, including better dose conformity for the tumors, more rapid dose drop and less dose spillage outside the tumors area, effective reduction of dose bridges among close tumors, and sparing OARs. It also reveals the correlations between the number or volume of tumors and dose parameters, which can help optimize the use of HyperArc and predict clinical benefits.