Planning Target Research Articles

Enhancing pancreatic tumor delineation using dual-energy CT-derived extracellular volume fraction map.

Precise identification of pancreatic tumors is challenging for radiotherapy planning due to the anatomical variability of the tumor and poor visualization of the tumor on 3D cross-sectional imaging. Low extracellular volume fraction (ECVf) correlates with poor vasculature uptake and possible necrosis or hypoxia in pancreatic tumors. This work investigates the feasibility of delineating pancreatic tumors using ECVf spatial distribution maps derived from contrast enhanced dual-energy CT (DECT). Data acquired from radiotherapy simulation of 12 pancreatic cancer patients, using a dual source DECT scanner, were analyzed. For each patient, an ECVf distribution of the pancreas was computed from the simultaneously acquired low and high energy DECT series during the late arterial contrast phase combined with the patient's hematocrit level. Volume of interest (VECVf) maps in ECVf distribution of pancreas were identified by applying an appropriate threshold condition and a connected components clustering algorithm. The obtained VECVf was compared with the clinical gross tumor volume (GTV) using the positive predictive value (PPV), Dice similarity coefficient (DSC), mean distance to agreement (MDA) and true positive rate (TPR). As a proof of concept, our hypothetical threshold condition based on the first quartile separation of the ECVf distribution to find VECVf of the pancreas elucidates the tumor volume within the pancreas. Notably, 7 out of 12 cases studied for VECVf matched well with the GTV and the mean PPV of 0.83±0.12. The mean MDA (2.83±1.0) of the cases confirms that VECVf lies within the tolerance for comparing to the pancreatic GTV. For the remaining 5 cases, the VECVf is substantially affected by other compounding factors, e.g., large cysts, dilate ducts, and thus did not align with the GTVs. This work demonstrated the promising application of the ECVf map, derived from contrast enhanced DECT, to help delineate tumor target for RT planning of pancreatic cancer.

Understanding and modeling human-AI interaction of artificial intelligence tool in radiation oncology clinic using deep neural network: a feasibility study using three year prospective data

Objective.Artificial intelligence (AI) based treatment planning tools are being implemented in clinic. However, human interactions with such AI tools are rarely analyzed. This study aims to comprehend human planner's interaction with the AI planning tool and incorporate the analysis to improve the existing AI tool.Approach.An in-house AI tool for whole breast radiation therapy planning was deployed in our institution since 2019, among which 522 patients were included in this study. The AI tool automatically generates fluence maps of the tangential beams to create anAI plan. Human planner makes fluence edits deemed necessary and after attending physician approval for treatment, it is recorded asfinal plan. Manual modification value maps were collected, which is the difference between theAI-planand thefinal plan. Subsequently, a human-AI interaction (HAI) model using full scale connected U-Net was trained to learn such interactions and perform plan enhancements. The trained HAI model automatically modifies theAI planto generate AI-modified plans (AI-m plan), simulating human editing. Its performance was evaluated against originalAI-planandfinal plan. Main results. AI-m planshowed statistically significant improvement in hotspot control over theAI plan, with an average of 25.2cc volume reduction in breast V105% (p= 0.011) and 0.805% decrease in Dmax (p< .001). It also maintained the same planning target volume (PTV) coverage as thefinal plan, demonstrating the model has captured the clinic focus of improving PTV hot spots without degrading coverage.Significance.The proposed HAI model has demonstrated capability of further enhancing theAI planvia modeling human-AI tool interactions. This study shows analysis of human interaction with the AI planning tool is a significant step to improve the AI tool.

Assessing the correlation between Gamma passing rate and clinical dosimetric variations in breast cancer IMRT plans with multi-leaf collimator errors: perspectives from the ArcCHECK QA system.

This study aimed to comprehensively investigate the influence of multi-leaf collimator (MLC) position errors on both the clinical absolute dose distribution and Gamma passing rate (%GP) in intensity-modulated radiation therapy (IMRT) plans for breast cancer. Additionally, the correlation between %GP and the clinical absolute dose relative difference (%DE) caused by MLC position errors was analysed. Ten IMRT plans for breast cancer were randomly selected. Systematic and random MLC position errors were introduced into DICOM files representing the investigated treatment plans by modifying the plan files and adjusting the MLC positions. Systematic errors were categorized as MLC opening errors, closing errors, and shift errors. The %DE in the tumour planning target volume (PTV) and organs at risk (OARs) caused by MLC errors were statistically analyzed using dose-volume histogram (DVH) analysis. The ArcCHECK quality assurance (QA) system was used to detect the %GP differences between baseline plans and plans with MLC errors. The correlation between %GP and %DE was obtained using linear regression methods. The results of this study indicate that MLC opening and closing errors have a significant impact on %DE and %GP in IMRT plans for breast cancer. Opening and closing errors can be detected at a gamma level of 3%/2mm, if error values are greater than or equal to 0.5mm, and %GP can predict DVH dosimetric changes caused by MLC opening and closing errors. It is concluded that DVH-based verification of IMRT plans can serve as an adjunct method to Gamma analysis to improve QA accuracy for breast cancer cases. Additionally, it is concluded that greater attention should be given to MLC leaf opening and closing errors in clinical practice.

Efficacy of palliative hemostatic radiotherapy for tumor bleeding and pain relief in locally advanced pelvic gynecological malignancies.

The appearance of symptomatic tumor-related vaginal bleeding and pain in advanced incurable cancer patients with pelvic gynecological malignancies remains atherapeutic challenge in oncological treatment. The aim of our analysis was to evaluate the efficacy and safety of palliative hemostatic radiotherapy. We retrospectively identified patients who had received palliative hemostatic radiotherapy (RT) at our institution between 2011 and 2023 and evaluated acute toxicity, local control, cessation of bleeding, and pain relief. In total, 40patients with amedian planning target volume of 804 cm3 were treated with amedian total dose of 39 Gy in 13fractions, resulting in 6‑month and 1‑year local control rates of 66.9 and 60.8%, respectively. No higher-grade (>gradeIII) acute RT-induced toxicity appeared. Complete cessation of bleeding was achieved in 80.0% of all patients after amedian of 16days and pain relief was documented in 60.9% at first follow-up. 37.5% of the women required ablood transfusion and 25% an additional tamponade with local hemostatic agents. Successful stopping of bleeding was significantly less frequent in patients receiving anticoagulation concurrently with radiation and in the case of infield re-irradiation. Patients with ahigher total RT dose had cessation of bleeding significantly more often, with acut-off value of at least EQD2 (α/β = 10) = 36 Gy. The applied RT technique and planning target volume had no significant influence on the occurrence of bleeding cessation. Palliative hemostatic radiotherapy for locally advanced pelvic gynecological malignancies is safe and effective in achieving high control rates of hemostasis in tumor bleeding and pain relief.

RADT-17. FRACTIONATED REIRRADIATION OF RECURRENT IDH WILDTYPE GLIOBLASTOMA: HIGHER REIRRADIAITON DOSE AND SAFETY

Abstract The optimal regimen, normal tissue tolerances, and appropriate indications for reirradiation for recurrent glioblastoma (GBM) are uncertain. We evaluate outcomes and toxicity after fractionated reirradiation. Patients with recurrent IDH wildtype GBM after prior standard radiotherapy during 2007-2022 were retrospectively reviewed. All patients initially received conventionally fractionated radiotherapy. Radiation necrosis (RN) was determined by imaging or pathology. Overall survival (OS) was estimated using Kaplan-Meier methodology. Univariate and multivariate Cox proportional hazard models for OS were constructed. Bivariable associations with RN were estimated using fisher exact tests. 99 patients (median age 56 yrs, median KPS 80) were treated with reirradiation (median followup 7.4 mo). Median time between initial and reirradiation was 20 months (range, 2 – 214 mo). Median received dose at reirradiation was 41.4 Gy (30.6 – 60 Gy) to a median planning target volume (PTV) of 183 cc (16 – 825 cc). Median cumulative maximum dose to the optics and brainstem were 54 Gy (4 – 103 Gy) and 76 Gy (5 – 146 Gy), respectively. Median OS was 9 mo (95% CI 6.2 – 10.6 mo). On univariate analysis, time between initial and reirradiation ≥24 mo (HR 0.58, CI 0.36 – 0.94) and reirradiation dose ≥41.4 Gy (HR 0.56, CI 0.35 – 0.88) were associated with longer OS. On multivariate analysis, interval between radiation sessions (HR 0.56, CI 0.34 – 0.91) and higher reirradiation dose (HR 0.55, CI 0.35 – 0.87) remained associated with OS. No cases of radiation injury to the optics or brainstem were reported. 10% of patients experienced RN. Reirradiation dose ≥41.4 Gy, reirradiation PTV ≥200 cc and interval between radiation sessions &amp;lt; 24 mo were not significantly associated with RN. These data support the safety and efficacy of fractionated reirradiation for recurrent GBM including for large tumors. This study suggests that higher reirradiation dose may be feasible, including for large treatment volumes.

Defining the potential for sexual structures-sparing for prostate cancer external beam radiotherapy: A dosimetric study

PurposeThe purpose of the study was to evaluate the dosimetric impact of sexual-sparing radiotherapy for prostate cancer, with magnetic resonance-only treatment planning. Material and methodsFifteen consecutive patients receiving prostate cancer radiotherapy were selected. A synthetic CT was generated with a deep learning method from each T2-weighted MRI performed at the time of treatment planning. For each patient, two plans were performed: standard treatment planning and sexual-structures sparing treatment planning. The treatment plan was designed to deliver a dose of 78Gy to the prostate and 50Gy to the seminal vesicles in 2Gy daily fractions, using volumetric arc therapy. Dose–volume histograms were computed to compare treatment plans. ResultsAll plans fulfilled dosimetric objectives and were equivalent regarding planning target volume coverage. The doses delivered to both rectum, bladder, and femoral heads were similar between plans (P=0.20). Sexual-sparing plans enabled to decrease all dosimetric parameters on sexual organs-at-risk. The mean penile bulb dose in sexual-sparing plans was significantly reduced (21.1Gy±20.7 versus 13.4Gy±14.0, P<0.01), however with large variability observed between individuals. The mean dose delivered to the corpora cavernosa was also significantly reduced within sexual-sparing plans (13.1Gy±16.7 versus 8.6Gy±10.4, P<0.01). A significant reduction was also observed in the highest doses delivered to internal pudendal arteries (D10%: 48.4Gy±8.3 versus 33.1Gy±4.6, P<0.05; D5%: 52.0Gy±8.7 versus 36.8Gy±5.5, P<0.05). ConclusionSparing of sexual structures appears feasible, without compromising neither planning target volume coverage nor doses delivered to non-sexual organs at risk. The clinical significance of this dose-reduction requires prospective evaluation.

Validation of different automated segmentation models for target volume contouring in postoperative radiotherapy for breast cancer and regional nodal irradiation

IntroductionTarget volume delineation is routinely performed in postoperative radiotherapy (RT) for breast cancer patients, but it is a time-consuming process. The aim of the present study was to validate the quality, clinical usability and institutional-specific implementation of different auto-segmentation tools into clinical routine. MethodsThree different commercially available, artificial intelligence-, ESTRO-guideline-based segmentation models (M1-3) were applied to fifty consecutive reference patients who received postoperative local RT including regional nodal irradiation for breast cancer for the delineation of clinical target volumes: the residual breast, implant or chestwall, axilla levels 1 and 2, the infra- and supraclavicular regions, the interpectoral and internal mammary nodes. Objective evaluation metrics of the created structures were conducted with the Dice similarity index (DICE) and the Hausdorff distance, and a manual evaluation of usability. ResultsThe resulting geometries of the segmentation models were compared to the reference volumes for each patient and required no or only minor corrections in 72 % (M1), 64 % (M2) and 78 % (M3) of the cases. The median DICE and Hausdorff values for the resulting planning target volumes were 0.87–0.88 and 2.96–3.55, respectively. Clinical usability was significantly correlated with the DICE index, with calculated cut-off values used to define no or minor adjustments of 0.82–0.86. Right or left sided target and breathing method (deep inspiration breath hold vs. free breathing) did not impact the quality of the resulting structures. ConclusionArtificial intelligence-based auto-segmentation programs showed high-quality accuracy and provided standardization and efficient support for guideline-based target volume contouring as a precondition for fully automated workflows in radiotherapy treatment planning.

Dosimetric Evaluation of Beam-specific PTV and Worst-case Optimization Methods for Liver Proton Therapy.

In spot-scanning proton therapy, intra-fractional anatomical changes by organ movement can lead to deterioration in dose distribution due to beam range variation. To explore a more robust treatment planning method, this study evaluated the dosimetric characteristics and robustness of two proton therapy planning methods for liver cancer. Two- or three-field treatment plans were created for 11 patients with hepatocellular carcinoma or metastatic liver cancer using a single-field uniform dose (SFUD) technique. The plans were optimized using either beam-specific planning target volume (BSPTV) or worst-case optimization (WCO). The target coverage for the gross tumor volume (GTV), planning target volume (PTV), and organs at risk (OAR) parameters related to toxicity were calculated from the perturbed dose distributions, considering setup and range uncertainties. Statistical analyses of the BSPTV and WCO plans were performed using the Wilcoxon signed-rank sum test (p<0.05). The calculation times for a single optimization process were also recorded and compared. The robustness of the WCO plans in the worst-case scenario was significantly higher than that of the BSPTV plan in terms of GTV target coverage, prevention of maximum dose increase to the gastrointestinal tract, and the dose received by normal liver regions. However, there were no significant differences in PTV, and the calculation time required to create the WCO plan was considerably longer. In SFUD proton therapy for liver cancer, the WCO plans required a longer optimization time but exhibited superior robustness in GTV coverage and sparing of OARs.

Dosimetric optimization for dynamic mixed beam arc therapy (DYMBARC).

Non-coplanarity and mixed beam modality could be combined to further enhance dosimetric treatment plan quality. We introduce dynamic mixed beam arc therapy (DYMBARC) as an innovative technique that combines non-coplanar photon and electron arcs, dynamic gantry and collimator rotations, and intensity modulation with photon multileaf collimator (MLC). However, finding favorable beam directions for DYMBARC is challenging due to the large solution space, machine component constraints, and optimization parameters, posing a highly non-convex optimization problem. To establish DYMBARC and solve the pathfinding challenge by employing direct aperture optimization (DAO) to determine the table angles and gantry angle ranges of photon and electron arcs for different clinically motivated cases. The method starts by generating a grid of beam directions based on user-defined resolutions along the gantry and table angle axes for each beam quality considered. Beam directions causing collisions or entering through the end of CT are excluded. For electrons, a fixed source-to-surface distance of 80cm is used to reduce in-air scatter. Electron beam energies with insufficient range to reach the target or beam directions impinging on the table before reaching the patient are excluded. The remaining beam directions form the pathfinding solution space. Promising photon and electron MLC-defined apertures, with associated monitor unit (MU) weights, are iteratively added using a hybrid-DAO algorithm. This algorithm combines column generation to add apertures and simulated annealing to further refine aperture shapes and weights. Apertures are added until the requested number of paths are formed and the user-defined maximum total gantry angle range is reached. Paths are resampled to a finer gantry angle resolution and subject to DAO for simultaneous optimization of beam intensities along the photon/electron arcs. Subsequent final dose calculation and MU weight reoptimization result in a deliverable DYMBARC plan. DYMBARC plans are created for three clinically motivated cases (brain, breast, and pelvis) and compared to DYMBARC variants: colli-DTRT (dynamic collimator trajectory radiotherapy) using non-coplanar photon arcs; and Arc-MBRT (mixed beam radiotherapy) using photons and electrons but restricted to coplanar setup. Additionally, a manually defined volumetric modulated arc therapy (VMAT) setup serves as a reference clinical technique. Dose distributions, dose-volume histograms, and dosimetric endpoints are evaluated. Dosimetric validation with radiochromic film measurements (gamma evaluation, 3% / 2mm (global), 10% dose threshold) is performed on a TrueBeam system in developer mode for one case. While maintaining similar target coverage and homogeneity, DYMBARC reduced mean doses to organs-at-risk compared to VMAT by an average of 3.2, 0.5, and 2.9Gy for the brain, breast, and pelvis cases, respectively. Similar or smaller mean dose reductions were observed for Arc-MBRT or colli-DTRT, compared to VMAT. Electron contributions to the mean planning target volume dose ranged from 2% to 34% for DYMBARC and from 11% to 40% for Arc-MBRT. Measurement validation showed>99.7% gamma passing rate. DYMBARC was successfully established using a dosimetrically optimized pathfinding approach, combining non-coplanarity with mixed beam modality. DYMBARC facilitated the determination of photon and electron contributions on a case-by-case basis, enhancing more personalized treatment modalities.

How workable is a 20-minute city in Australia? Re-examining the challenge of change in spatial labour and job relations

ABSTRACT Most x-minute city studies focus on liveability and neighborhood accessibility to local services, but rarely include primary employment. This paper complements these studies by examining the urban employment structure and transport dynamics of an Australian city under the 20-minute city concept framework. To do this, we develop a comprehensive method to model residents’ job access time using census-based journey to work (JTW) data and detailed household activity and travel survey. Analysing JTW time stepping down to diverse industry and employment categories and transport modes allows new insight into the disparity in residents’ job and housing locations and transport choices at local scales. By evaluating the distribution of working residents, types of employment, and transport performance, this paper examines possible policy responses and challenges of change in expanding the 20-minute planning target for employment. The analysis suggests that housing infill development could support reduced JTW time for residents experiencing longer time for work travels. However, this would require active planning of both land-use mix and dwelling design to meet prevalent household expectations about dwelling size and quality.

Assessing the robustness of dose distributions in carbon ion prostate radiotherapy using a fast dose evaluation system.

We developed a software program for swiftly calculating dose distributions for carbon ion beams. This study aims to evaluate the accuracy of dose calculations using this software and assess the robustness of dose distribution in treating prostate cancer. At the Osaka Heavy Ion Therapy Center, markers are inserted into the prostate gland and used for position verification. To account for geometric changes along the beam path due to marker translation, a beam-specific planning target volume (bsPTV) is set for each beam. To validate the accuracy of the dose calculations using the developed software, dose distributions for prostate and sarcoma cases were calculated and compared with the treatment planning system. To assess the robustness of the dose distribution, position verification data from 346 cases were utilized to reproduce dose distributions for three matching methods: bone matching, widely adopted in most particle therapy centers; marker translation, which involves direct translation to markers without bone matching; and marker translation after bone matching. The coverage of the target (D99 of clinical target volume (CTV)) was assessed to evaluate the robustness of the dose distribution. Additionally, statistical analyses were conducted for the dose distributions of each matching method. The dose calculation for a single condition can be completed very quickly. Statistical analysis revealed significant differences among dose distributions considering the three matching methods. When irradiation was performed with bone matching only, the D99 was reduced by more than 10% in approximately 7.5% of cases, making it as the poorest among the three matching methods. However, there was no significant reduction in target coverage with the other two methods. We have demonstrated the accuracy of the developed software for rapidly calculating dose distributions for carbon ion beams and confirmed the robustness of the dose distributions based on the bsPTV.

Predictors of brain metastases in patients with oligometastatic solid tumours treated with stereotactic body radiation therapy.

In patients with oligometastatic disease (OMD) treated with stereotactic body radiation therapy (SBRT), those who develop brain metastases (BrM) may have poor outcomes. We aimed to investigate variables associated with BrM development in this population. Patients with ≤ 5 extracranial metastases from solid tumors treated with SBRT from 2008 to 2016 at Sunnybrook Odette Cancer Centre were included. We investigated the association between covariates and CIBrM (cumulative incidence of BrM) using Fine-Gray analysis, and progression-free survival (PFS) and overall survival (OS) using Cox regression. We investigated the association between extracranial progression and CIBrM using time-based conditional analysis. Among 404 patients, the most common primary sites were lung, colorectal, prostate, breast and kidney. Median follow-up was 49 months. Median PFS was 25 months. Median OS was 70 months. 58 patients developed BrM, and 5-year CIBrM was 16%. On multivariable analysis, number of extracranial metastases, location of metastases, total planning target volume (PTV), and time from primary diagnosis to OMD were not associated with CIBrM, although several of these variables were associated with extracranial PFS and OS. Primary site was associated with CIBrM, with colorectal and prostate cancer associated with lower CIBrM compared to lung cancer. Widespread extracranial progression (≥ 5 sites) within 24, 36, 48 and 60 months of OMD diagnosis was independently associated with higher CIBrM. In patients with OMD treated with SBRT, baseline variables related to extracranial disease burden and distribution were not associated with BrM development, while primary site and widespread extracranial progression were associated with BrM development.

Dosimetric comparison of gamma knife and linear accelerator (VMAT and IMRT) plans of SBRT of Lung tumours

This study evaluates dosimetric differences in Stereotactic Body Radiation Therapy (SBRT) for lung tumors using plans of Gamma Knife, and Volumetric Modulated Arc Therapy (VMAT), Intensity-Modulated Radiation Therapy (IMRT) plans based on Linear Accelerator, aiming to inform the reader of appropriate treatment strategy selection. Ten patients with 23 lung tumor lesions treated with SBRT at Zhongshan Hospital of Dalian University were analyzed. Plans of Gamma Knife, and VMAT, IMRT plans based on Linear Accelerator were created for each lesion, totaling 18 plans per type. Lesions were treated with 30–50 Gy in 5–10 fractions. Dosimetric parameters, including gradient index (GI), heterogeneity index (HI), conformity index (CI), and doses to the plan target volumes (PTVs), the gross tumor volumes (GTVs) and organs at risk (OARs) were compared. Plans of Gamma Knife showed superior HI and GI, higher PTV and GTV doses, and reduced doses to the ipsilateral and contralateral lungs, esophagus, spinal cord, and heart compared to VMAT and IMRT plans (p < 0.05). However, Plans of Gamma Knife required longer delivery times. When comparing VMAT and IMRT plans, VMAT plans had shorter delivery times than IMRT plans, but required more monitor units (MUs). Additionally, IMRT plans delivered a lower mean dose to the ipsilateral lung compared to VMAT plans. Gamma Knife SBRT plans achieves steeper dose falloff and minimizes radiation to normal lung tissue compared to VMAT and IMRT plans, but with longer delivery times. VMAT and IMRT plans displayed similar dose distributions for lung SBRT.

PDOC-05 MULTIPLE ISOCENTRE VMAT PLANNING FOR PAEDIATRIC CRANIOSPINAL IRRADIATION USING THE HALCYON LINEAR ACCELERATOR

Abstract Paediatric brain tumours constitute the leading cause of cancer specific deaths worldwide. Many patients require craniospinal irradiation (CSI), one of the most technically demanding techniques in radiotherapy. Many LMIC centres have installed Varian Halcyon® linear accelerators and require a technique to execute CSI safely. This study evaluates a multiple isocentre VMAT planning strategy for CSI. The Halcyon is a ring based linac with a single 6MV flattening filter free (FFF) photon beam, a stacked and staggered double MLC for beam shaping and modulation, and no movable collimator jaws. Multiple isocentres are required for treatment fields longer than 28 cm. Paediatric CSI requires dose to be delivered to the entire thecal sac incorporating whole brain as well as entire spinal cord, resulting in long planning target volumes. In addition to the length of the treatment field, CSI treatments are complex due to the change in geometry of the target and the patient body over the length of the treatment field. Traditional 3D conformal radiotherapy techniques (3DCRT) require multiple isocentres with field matching and junction feathering. VMAT offers an alternative, but also require multiple fields to achieve coverage. A Halcyon based three isocentre VMAT technique was investigated and evaluated according to the QUANTEC criteria. Portal dosimetry quality assurance was performed on all fields to ensure they were clinically deliverable. High quality paediatric CSI VMAT treatments can be delivered on the Halcyon, using three isocentres with automatic feathering applied in field overlap regions. Two full arcs and one support arc were used for the brain area, with two posterior partial arcs per spine isocentre, each covering a total of 140 degrees posteriorly to limit integral dose and dose to the lungs and kidneys. Imaging and setup is required for every isocentre further than 8cm/10cm (Halcyon V2/V3 respectively) from the previous isocentre.

Evaluation of radiotherapy planning approaches for head and neck patients with tumors close to the skin surface.

In radiotherapy of the head and neck (H&N) it is common for the clinical target volume (CTV) to extend to the patient's skin. Adding a margin for set-up uncertainty and delivery creates a planning target volume (PTV) that extends beyond the patient surface. This can result in excessive fluence being delivered to the build-up region and therefore the skin. This study evaluates four different planning methods used when inverse-planning H&N radiotherapy treatments with CTV extending to the skin. The aim of the study was to determine which planning method gives superior plan quality. Ten H&N cancer patients with a CTV contoured to the skin were inverse-planned using four planning methods. The planning methods compared were: cropping the optimization PTV back from the skin surface by 5.0, 3.0, and 0.0mm and a virtual bolus method. For each planning method, the increased fluence at the skin surface was analyzed. The CTV coverage and skin doses were compared. Plan robustness was evaluated by applying an isocenter shift of ±3.0mm in the major axes. The planning method cropping the PTV 0.0mm from the skin surface results in an increased fluence in the build-up region. The average volume of CTV receiving 98% of the prescription dose was 89.6%±3.4%, 91.6%±2.4%, and 93.5%±1.7% when cropped 5.0, 3.0, and 0.0mm, respectively, and 93.4%±2.1% for the virtual bolus method. Introducing plan uncertainty affects CTV coverage the most when cropping 5.0mm. When plan uncertainties are considered the methods of cropping 5.0, 3.0mm, and the virtual bolus method have the same average skin dose within ±0.3%. This study shows that a virtual bolus planning method results in no increased fluence at the patient's surface, improves CTV coverage, and is the most robust to changes in setup and patient anatomy.

Setup errors analysis in iterative kV CBCT: A clinical study of cervical cancer treated with Volumetric Modulated Arc Therapy.

This study aims to analyze setup errors in pelvic Volumetric Modulated Arc Therapy (VMAT) for patients with non-surgical primary cervical cancer, utilizing the onboard iterative kV cone beam CT (iCBCT) imaging system on the Varian Halcyon 2.0 ring gantry structure accelerator to enhance radiotherapy precision. We selected 132 cervical cancer patients who underwent VMAT with daily iCBCT imaging guidance. Before each treatment session, a registration method based on the bony structure was employed to acquire iCBCT images with the corresponding planning CT images. Following verification and adjustment of image registration results along the three axes (but not rotational), setup errors in the lateral (X-axis), longitudinal (Y-axis), and vertical (Z-axis) directions were recorded for each patient. Subsequently, we analyzed 3642 iCBCT image setup errors. The mean setup errors for the X, Y, and Z axes were 4.50±3.79mm, 6.08±6.30mm, and 1.48±2.23mm, respectively. Before correction with iCBCT, setup margins based on the Van Herk formula for the X, Y, and Z axes were 6.28, 12.52, and 3.26mm, respectively. In individuals aged 60 years and older, setup errors in the X and Y axes were significantly larger than those in the younger group (p<0.05). Additionally, there is no significant linear correlation between setup errors and treatment fraction numbers. Data analysis underscores the importance of precise Y-axis setup for cervical cancer patients undergoing VMAT. Radiotherapy centers without daily iCBCT should appropriately extend the planning target volume (PTV) along the Y-axis for cervical cancer patients receiving pelvic VMAT. Elderly patients exhibit significantly larger setup errors compared to younger counterparts. In conclusion, iCBCT-guided radiotherapy is recommended for cervical cancer patients undergoing VMAT to improve setup precision.

Fractionated Stereotactic Intensity-Modulated Radiotherapy for Large Brain Metastases: Comprehensive Analyses of Dose–Volume Predictors of Radiation-Induced Brain Necrosis

Background: The objective was to explore dosimetric predictors of brain necrosis (BN) in fractionated stereotactic radiotherapy (SRT). Methods: After excluding collinearities carefully, multivariate logistic models were developed for comprehensive analyses of dosimetric predictors in patients who received first-line fractionated SRT for brain metastases (BMs). The normal brain volume receiving an xx Gy biological dose in 2 Gy fractions (VxxEQD2) was calculated from the retrieved dose–volume parameters. Results: Thirty Gy/3 fractions (fr) SRT was delivered to 34 patients with 75 BMs (median target volume, 3.2 cc), 35 Gy/5 fr to 30 patients with 57 BMs (6.4 cc), 37.5 Gy/5 fr to 28 patients with 47 BMs (20.2 cc), and 40 Gy/10 fr to 20 patients with 37 BMs (24.3 cc), according to protocols, depending on the total target volume (p &lt; 0.001). After excluding the three-fraction groups, the incidence of symptomatic BN was significantly higher in patients with a larger V50EQD2 (adjusted odds ratio: 1.07, p &lt; 0.02), V55EQD2 (1.08, p &lt; 0.01), or V60EQD2 (1.09, p &lt; 0.01) in the remaining five- and ten-fraction groups. The incidence of BN was also significantly higher in cases with V55EQD2 &gt; 30 cc or V60EQD2 &gt; 20 cc (p &lt; 0.05). These doses correspond to 28 or 30 Gy/5 fr and 37 or 40 Gy/10 fr, respectively. Conclusions: In five- or ten-fraction SRT, larger V55EQD2 or V60EQD2 are BN risk predictors. These biologically high doses may affect BN incidence. Thus, the planning target volume margin should be minimized as much as possible.

Simultaneous integrated boost-intensity modulated radiation therapy (SIBIMRT) planning for pelvic tumours: dose coverage to target volume and normal tissue sparing.

To evaluate the better radiotherapy plan for pelvic tumours that may achieve a high target coverage dose and low normal tissue tolerance dose using simultaneous integrated boost-intensity-modulated radiation therapy technique. The analytical, cross-sectional, descriptive study was conducted from October 2020 to March 2021 at Al- Amal National Hospital for Cancer Treatment, Baghdad, Iraq, and comprised male pelvic cancer patients aged 50-80 years. Computed tomography scans were randomly selected. For each patient, 4 treatment plans (phases Ι and Π) were generated using the simultaneous integrated boost-intensity-modulated radiation therapy technique while keeping all parameters constant except the number of beams, which were 5, 7, 9 and 11. The optimal and safe dose was defined as the one to cover 95% planning target volume. Homogeneity and conformity indices were used to assess the uniformity of dose distribution in the target volume, and various treatment plans in the same patient were compared. Data was analysed using SPSS 24. There were 15 males with mean age 67.12±2.84 years. There was a significant variance in the target volume dose and organ at risk in the 4 different plans generated using the simultaneous integrated boost-intensitymodulated radiation therapy technique (p<0.05). The 9-beam treatment plan was the best for coverage of tumours and protection of healthy organs assessed through homogeneity and conformity indices (p<0.05). The 9-beam treatment plan showed significant tumour coverage, homogeneity and conformity values, and sparing dose for organs at risk.

Dosimetric Evaluation of Hippocampus Sparing Intensity Modulated Radiation Therapy in Patients With Stage T1-T2 and Stage T3-T4 Nasopharyngeal Carcinoma

PurposeTo compare the hippocampus (HPC) dose reduced by HPC-sparing IMRT plans between nasopharyngeal carcinoma (NPC) patients of stages T1-T2 and T3-T4, and to investigate the correlation between the dose of the hippocampus and the volume of PTVnx70 (the planning target volume of the primary tumor in the nasopharynx received 70 Gy). Methods and MaterialsFifty-eight NPC patients were retrospectively evaluated. HPC non-sparing IMRT or sparing IMRT for each patient was designed according to the protocol for NPC. Dose-volume histogram (DVH) was used to evaluate the IMRT plans for each patient. The difference values of HPC parameters (e.g., Dmin[NS] - Dmin[S]) between HPC sparing and non-sparing plans in stage T1-T2 Group and stage T3-T4 Group were compared. The correlations between the dose of the hippocampus and the volume of PTVnx70 were analyzed. ResultsThere was no significance between HPC-sparing and non-sparing IMRT plans. Compared with the HPC non-sparing plans, the HPC sparing plans significantly decreased both dosimetric and volumetric parameters for the HPC (P < 0.05), except for Dmin, D98%, and V5. The medians of Dmedian[NS] - Dmedian[S], Dmean[NS] - Dmean[S], D40%[NS] - D40%[S], V30[NS] - V30[S], V40[NS] - V40[S] and V50[NS] - V50[S] in the T1-T2 Group were significantly lower than in the T3-T4 Group (P < 0.05), respectively. Both dosimetric and volumetric parameters for the HPC were positively correlated with the volume of PTVnx70 in HPC-sparing and non-sparing plans (P < 0.05). The volume of PTVnx70 was positively correlated with Dmedian[NS] - Dmedian[S], Dmean[NS] - Dmean[S], D40%[NS] - D40%[S], V40[NS] - V40[S] and V50[NS] - V50[S] (P < 0.05). ConclusionsHPC-sparing IMRT plans may play a more significant role in decreasing Dmedian, Dmean, D40%, and V30 ∼ V50 of HPC in NPC patients with stages T3-T4 than those in stages T1-T2. PTVnx70 volume of NPC patients are positively correlated with all dosimetric and volumetric parameters of HPC and the reduction of specific dosage parameters by HPC-sparing IMRT plans.

Development of Agribusiness in Tiwi, Albay

This study determined the status of agribusiness in Tiwi, Albay, as basis for the development of business plan. Specifically, it sought to answer the following sub- problems: 1) What are the areas of agribusiness in the Municipality of Tiwi, Albay?; 2) What are the status of agribusiness along; crop production, animal production, aquaculture production, and agri-support services and manufacturing?; 3) What are the contributions of the above areas in the agribusiness in Tiwi, Albay?; 4) What are the problems encountered in agribusiness?; and 5) What business plan may be proposed to address the problems encountered in agribusiness? The study involved presenting the agribusiness sectors contributions through tables and charts, emphasizing their economic impact and community significance. It addressed challenges by organizing issues like infrastructure or market access, supported by relevant data or case studies. It proposed a comprehensive business plan targeting specific problems with detailed strategies, cost estimates, and potential outcomes. Descriptive surveys are crucial in agribusiness research, providing detailed insights into agricultural practices and factors affecting productivity within a specific population. These surveys utilize statistical tools such as frequency percentage and weighted mean to accurately depict response distribution and measure the significance of variables. Synthesizing findings and ensuring proper citation and definition of terms in research helps draw meaningful conclusions and contribute to a broader understanding of agribusiness practices in the region. Incorporating literature demands a structured approach, starting with an introduction highlighting the topic's significance, organizing sources thematically or chronologically, and synthesizing findings while ensuring proper citation and defining terms for clarity. Descriptive surveys in agribusiness employed tools like frequency percentage to depict response distribution and weighted mean to gauge variable significance, offering precise insights into agricultural practices and factors affecting productivity within the surveyed population.