Comparison of Dynamic Trajectory Radiotherapy and Volumetric Modulated Arc Therapy for Loco-Regionally Advanced Oropharyngeal Cancer

PURPOSE/OBJECTIVE(S)

Dynamic trajectory radiotherapy (DTRT) extends volumetric modulated arc therapy (VMAT) with dynamic table and collimator rotation. We investigate the potential benefit of DTRT over VMAT with respect to organ-at-risk (OAR) sparing for patients with loco-regionally advanced oropharyngeal cancer (OPC).

MATERIALS/METHODS

We created DTRT and VMAT plans for 46 cases with prescribed doses of 50-70 Gy (2 Gy fractions, sequential boost) using 6 MV flattened beam on c-arm Linacs. For DTRT: case-specific collision avoidance maps were created and gantry-table paths were determined based on contoured structures to minimize fractional target/OAR overlap in beam's eye view. Gantry-collimator paths minimized field width in the leaf-travel direction. DTRT paths were imported in a research version of a commercial treatment planning system for intensity modulation optimization using the same optimizer and dose calculation algorithms as for VMAT. Plans at each dose level were normalized with 100% of the prescribed dose to 95% of the planning target volume (PTV). PTV coverage and OAR sparing for DTRT and VMAT were compared using Wilcoxon matched-pair signed rank test (5% significance level). The correlation between the fractional OAR/PTV50Gy volume overlap and difference in OAR Dmean between the two techniques was evaluated using Spearman's correlation coefficient.

RESULTS

Plans at each dose level were all acceptable and had D0.03cc<110% prescription dose (difference between DTRT and VMAT were not statistically significant). In the combined plans, PTV50Gy D95% and D98% and PTV70Gy D95% were significantly higher with DTRT compared to VMAT. Differences in PTV66Gy coverage and PTV70Gy D5% were not statistically significant. Mean Dmean to the contralateral (CL) parotid gland was 13.99 / 15.28 Gy for DTRT / VMAT respectively, it was 25.75 / 28.05 Gy for the CL submandibular gland, 44.88 / 45.82 Gy for the pharynx and 30.90 / 33.93 Gy for the oral cavity (all with p<.001). Mean Dmean to the ipsilateral (IL) parotid gland was 29.00 / 29.28 Gy for DTRT / VMAT respectively (p = .77) and 57.71 / 57.91 Gy for the IL submandibular gland (p = .99). Significantly higher doses were observed with DTRT than with VMAT for the optical and auditory OARs and for the brain, but well below the clinical goals. The difference in Dmean (VMAT-DTRT) was negatively correlated to the fractional OAR/PTV50Gy overlap for the CL parotid and submandibular gland and the IL submandibular gland (r = -0.55 to -0.51, p<.001) but not for IL parotid gland (r = -0.17, p = .26), oral cavity (r = -0.13, p = .41) or pharynx (r = -011, p = .47).

CONCLUSION

For at least the same target coverage, DTRT statistically significantly improves sparing for OARs related to salivary and swallowing functions compared to state-of-the-art VMAT. The advantage of DTRT decreases with increasing fractional OAR/PTV50Gy volume overlap for some salivary glands but not for pharynx or oral cavity. DTRT is promising to reduce treatment-related toxicity for patients with OPC.

Auto-commissioning of a Monte Carlo electron beam model with application to photon MLC shaped electron fields

Objective.Presently electron beam treatments are delivered using dedicated applicators. An alternative is the usage of the already installed photon multileaf collimator (pMLC) enabling efficient electron treatments. Currently, the commissioning of beam models is a manual and time-consuming process. In this work an auto-commissioning procedure for the Monte Carlo (MC) beam model part representing the beam above the pMLC is developed for TrueBeam systems with electron energies from 6 to 22 MeV.Approach.The analytical part of the electron beam model includes a main source representing the primary beam and a jaw source representing the head scatter contribution each consisting of an electron and a photon component, while MC radiation transport is performed for the pMLC. The auto-commissioning of this analytical part relies on information pre-determined from MC simulations, in-air dose profiles and absolute dose measurements in water for different field sizes and source to surface distances (SSDs). For validation calculated and measured dose distributions in water were compared for different field sizes, SSDs and beam energies for eight TrueBeam systems. Furthermore, a sternum case in an anthropomorphic phantom was considered and calculated and measured dose distributions were compared at different SSDs.Main results.Instead of the manual commissioning taking up to several days of calculation time and several hours of user time, the auto-commissioning is carried out in a few minutes. Measured and calculated dose distributions agree generally within 3% of maximum dose or 2 mm. The gamma passing rates for the sternum case ranged from 96% to 99% (3% (global)/2 mm criteria, 10% threshold).Significance.The auto-commissioning procedure was successfully implemented and applied to eight TrueBeam systems. The newly developed user-friendly auto-commissioning procedure allows an efficient commissioning of an MC electron beam model and eases the usage of advanced electron radiotherapy utilizing the pMLC for beam shaping.

Efficiency enhancements of a Monte Carlo beamlet based treatment planning process: implementation and parameter study

Objective.The computational effort to perform beamlet calculation, plan optimization and final dose calculation of a treatment planning process (TPP) generating intensity modulated treatment plans is enormous, especially if Monte Carlo (MC) simulations are used for dose calculation. The goal of this work is to improve the computational efficiency of a fully MC based TPP for static and dynamic photon, electron and mixed photon-electron treatment techniques by implementing multiple methods and studying the influence of their parameters.Approach.A framework is implemented calculating MC beamlets efficiently in parallel on each available CPU core. The user can specify the desired statistical uncertainty of the beamlets, a fractional sparse dose threshold to save beamlets in a sparse format and minimal distances to the PTV surface from which 2 × 2 × 2 = 8 (medium) or even 4 × 4 × 4 = 64 (large) voxels are merged. The compromise between final plan quality and computational efficiency of beamlet calculation and optimization is studied for several parameter values to find a reasonable trade-off. For this purpose, four clinical and one academic case are considered with different treatment techniques.Main results.Setting the statistical uncertainty to 5% (photon beamlets) and 15% (electron beamlets), the fractional sparse dose threshold relative to the maximal beamlet dose to 0.1% and minimal distances for medium and large voxels to the PTV to 1 cm and 2 cm, respectively, does not lead to substantial degradation in final plan quality compared to using 2.5% (photon beamlets) and 5% (electron beamlets) statistical uncertainty and no sparse format nor voxel merging. Only OAR sparing is slightly degraded. Furthermore, computation times are reduced by about 58% (photon beamlets), 88% (electron beamlets) and 96% (optimization).Significance.Several methods are implemented improving computational efficiency of beamlet calculation and plan optimization of a fully MC based TPP without substantial degradation in final plan quality.

Associations between training characteristics and change in peak oxygen consumption following exercise training in patients with heart failure with preserved ejection fraction

Introduction

In heart failure with preserved ejection fraction (HFpEF), moderate continuous training (MCT) and high-intensity interval training (HIIT) are both effective in increasing peak oxygen uptake (peak V̇O2).

Purpose

The aim of this study was to investigate the association of training characteristics (i.e. average sessions/week, average duration/week, mean intensity) and change in peak V̇O2 following 3 months of MCT and HIIT in patients with HFpEF.

Methods

Among 120 patients who were randomized to MCT (5x40 min/week at 35–50% heart rate reserve [HRR]) or HIIT (3x38 min/week at 80–90% HRR), those who completed 3-month follow-up (N=107) were considered for this analysis. Training duration and heart rates [HR] were recorded with a smartphone application, evaluated with a customized software and manually checked for plausibility. If HR measurements were classified as invalid/unreliable (e.g. very strong fluctuations), patients were excluded from analysis. Intensities were calculated as average % HRR of total sessions in MCT and the average of the highest % HRR values of all intervals in HIIT. Associations between training characteristics and change in peak V̇O2 were evaluated using univariate and multivariate regression analyses. Individual HR-V̇O2 relationships were used to calculate and compare energy expenditure (MET-minutes) in MCT and HIIT.

Results

After excluding 16 patients due to invalid/unreliable HR data, 91 patients (67% female, 69±7 years) were included in this analysis. On average, MCT patients (N=45) performed 4.0±1.2 sessions/week (162±52 min/week) at 47.4±6.7% HRR, while HIIT patients (N=46) performed 2.4±0.8 sessions/week (96±40 min/week) at 81.8±11.8% HRR. Peak V̇O2 was improved by 1.70±2.35 ml/kg/min in MCT and 1.46±2.98 ml/kg/min in HIIT (difference: 0.24 [95% CI, −0.87 to 1.34], p=0.67). The associations between training characteristics and change in peak V̇O2 are shown in Fig.1. Mean % HRR was not significantly associated with the change in peak V̇O2 in the HIIT group, whereas in MCT, mean duration/week and mean intensity were of similar relative importance (standardized coefficients) and explained up to 26% of the variation in change in peak V̇O2 (Table 1). Average weekly MET-minutes above rest were 451±260 for MCT and 389±375 for HIIT (difference: 62 [95% CI, −71 to 195], p=0.36). After adjustment for MET-minutes, the difference in change in peak V̇O2 between groups diminished to 0.09 ml/kg/min (95% CI, −0.97 to 1.16; p=0.98).

Conclusions

Weekly duration and mean % HRR had a similar predictive ability for the change in peak V̇O2 following MCT with, interestingly, lower change in peak V̇O2 with increasing intensity. In HIIT, mean % HRR was not significantly associated with the change in peak V̇O2. After adjusting for energy expenditure, the difference in change in peak V̇O2 between training modes diminished, suggesting that MCT and HIIT were similarly effective.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Commission, Framework Program 7

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Objective. The purpose of this study is to develop a treatment planning process (TPP) for non-isocentric dynamic trajectory radiotherapy (DTRT) using dynamic gantry rotation, collimator rotation, table rotation, longitudinal, vertical and lateral table translations and intensity modulation and to validate the dosimetric accuracy. Approach. The TPP consists of two steps. First, a path describing the dynamic gantry rotation, collimator rotation and dynamic table rotation and translations is determined. Second, an optimization of the intensity modulation along the path is performed. We demonstrate the TPP for three use cases. First, a non-isocentric DTRT plan for a brain case is compared to an isocentric DTRT plan in terms of dosimetric plan quality and delivery time. Second, a non-isocentric DTRT plan for a craniospinal irradiation (CSI) case is compared to a multi-isocentric intensity modulated radiotherapy (IMRT) plan. Third, a non-isocentric DTRT plan for a bilateral breast case is compared to a multi-isocentric volumetric modulated arc therapy (VMAT) plan. The non-isocentric DTRT plans are delivered on a TrueBeam in developer mode and their dosimetric accuracy is validated using radiochromic films. Main results. The non-isocentric DTRT plan for the brain case is similar in dosimetric plan quality and delivery time to the isocentric DTRT plan but is expected to reduce the risk of collisions. The DTRT plan for the CSI case shows similar dosimetric plan quality while reducing the delivery time by 45% in comparison with the IMRT plan. The DTRT plan for the breast case showed better treatment plan quality in comparison with the VMAT plan. The gamma passing rates between the measured and calculated dose distributions are higher than 95% for all three plans. Significance. The versatile benefits of non-isocentric DTRT are demonstrated with three use cases, namely reduction of collision risk, reduced setup and delivery time and improved dosimetric plan quality.

Long-term predictive value of serum PSA values obtained in clinical practice: Results from the Norwegian Prostate Cancer Consortium (NPCC)

5021

Background: A baseline prostate-specific antigen (PSA) level in midlife is strongly associated with risk of lethal prostate cancer several decades later. In most prior studies, PSA was measured in archived blood from men participating in cohort studies unrelated to prostate cancer. In clinical practice, however, men commonly obtain a PSA test because of lower urinary tract symptoms. Here, we study the association between PSA values when a first PSA test was obtained as part of clinical care – and subsequent risks of prostate cancer diagnosis and death. Methods: The NPCC database contained laboratory results from 1995-2006 of the first (“baseline”) PSA test below 4.0 ng/mL in 157,836 men aged 40-69 years without prior prostate cancer (PCa) diagnosis. PSA strata were pre-defined: < 1, 1-1.99, 2-2.99, 3-3.99 ng/ml and analyses were split in two age groups based on a prior risk: 40-54 (“younger”) and 55-69 (“older”). Predictive accuracy was assessed with Harrell’s concordance (C) index. The Kaplan-Meier method was used to visualize risk of PCa death as reported on the death certificate by PSA strata for the two age groups. Results: Among 157,836 men with a PSA below 4.0 ng/mL, 83% had < 2.0 ng/mL. Risk of prostate cancer and death from prostate cancer were strongly associated with PSA-levels and age: Harrell’s C-index 0.75 and 0.72 for diagnosis of younger and older group, respectively and 0.72 for PCa death for both age groups. In the younger age group 196 deaths among 75,446 men (0.26%) were registered, in the older 943 deaths among 82,390 men (1.14%). The risk of PCa death in lowest (< 1) and highest (3-3.99) strata were 0.23% and 3.22%, respectively (189 deaths among 81,982 vs. 274 deaths among 8517 men). Conclusions: This population-based NPCC study shows as strong predictive impact of the different strata of the initial PSA measurement in routine clinical care as prior studies based on cryopreserved blood samples. [Table: see text]

Effects of a telemedically supported home-based lifestyle intervention in patients with chronic ischaemic heart disease and type 2 diabetes mellitus

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Federal Joint Committee Germany

Background

Ischaemic heart disease is the leading cause of global mortality and when accompanied by type 2 diabetes mellitus (T2DM), prognosis is even worse. Lifestyle (LS) interventions are recommended, however, evidence in patients with both chronic ischaemic heart disease (CIHD) and T2DM is scarce. Furthermore, LS interventions were generally performed in a resource intensive supervised setting. Therefore, this study examined whether an individualised telemedically supported home-based LS intervention has a different effect on changes in glycosylated haemoglobin (HbA1c) compared to usual care (UC) in patients with CIHD and T2DM.

Methods

Eligible patients (ICD-10: I20-25; HbA1c≥6.5% or anti-diabetic drugs) were randomly assigned (1:1) to LS or UC at 11 sites. LS intervention consisted of home-based exercise training (ET) and nutritional recommendations following 7-day nutrition diaries. ET was based on the results of a cardiopulmonary exercise test (CPET), i.e. ventilatory thresholds and peak oxygen consumption, and was provided and recorded by a smartphone application. Intensities varied and volume was gradually increased to reach at least 150 min/week. Every 2-4 weeks, patients were contacted by telephone to receive feedback and adjust the training (if necessary). CPETs and nutrition diaries were analysed by a core laboratory, which also provided the feedback to the patients. Primary endpoint was the change in HbA1c after 6 months. Secondary endpoints included change in weight, waist circumference, HDL, LDL, triglycerides and quality of life (QoL). The main analysis included all patients with baseline and follow-up (FU) measures (full analysis). In a per-protocol analysis (PPA), patients randomised to LS who performed less than 2/3 of the scheduled exercise time or filled less than 2 out of 3 nutrition diaries were excluded.

Results

Among 499 enrolled patients (mean age, 68 years; 16% female; mean HbA1c, 6.9%), 402 (81%) completed the 6-month FU. From 201 patients who completed FU in the LS group, 76 (38%) were included in the PPA [81 (40%) adhered to ET, 144 (72%) filled at least 2 nutrition diaries]. In the full analysis, mean change in HbA1c was significantly different between LS and UC (-0.1% [95% CI, -0.2 to 0.0], p=0.04). Furthermore, significant differences were found for changes in weight (p&lt;0.001) and the QoL mental component score (MCS) of the Short-Form-36 questionnaire (p=0.006, Table 1). In the PPA, mean changes in HbA1c (p=0.002), weight (p&lt;0.001), waist circumference (p&lt;0.001), triglycerides (p=0.03) and the QoL MCS (p=0.004) were significantly different between groups (Table 1).

Conclusion

In patients with CIHD and T2DM, a telemedically supported home-based LS intervention significantly reduced HbA1c as compared to UC. However, only in the per-protocol analysis, change in HbA1c met a clinically meaningful difference of 0.3% between groups. Therefore, future studies should aim at increasing adherence to such interventions.

Development of a Monte Carlo based robustness calculation and evaluation tool

Background

Evaluating plan robustness is a key step in radiotherapy.

Purpose

To develop a flexible Monte Carlo (MC)‐based robustness calculation and evaluation tool to assess and quantify dosimetric robustness of intensity‐modulated radiotherapy (IMRT) treatment plans by exploring the impact of systematic and random uncertainties resulting from patient setup, patient anatomy changes, and mechanical limitations of machine components.

Methods

The robustness tool consists of two parts: the first part includes automated MC dose calculation of multiple user‐defined uncertainty scenarios to populate a robustness space. An uncertainty scenario is defined by a certain combination of uncertainties in patient setup, rigid intrafraction motion and in mechanical steering of the following machine components: angles of gantry, collimator, table‐yaw, table‐pitch, table‐roll, translational positions of jaws, multileaf‐collimator (MLC) banks, and single MLC leaves. The Swiss Monte Carlo Plan (SMCP) is integrated in this tool to serve as the backbone for the MC dose calculations incorporating the uncertainties. The calculated dose distributions serve as input for the second part of the tool, handling the quantitative evaluation of the dosimetric impact of the uncertainties. A graphical user interface (GUI) is developed to simultaneously evaluate the uncertainty scenarios according to user‐specified conditions based on dose‐volume histogram (DVH) parameters, fast and exact gamma analysis, and dose differences. Additionally, a robustness index (RI) is introduced with the aim to simultaneously evaluate and condense dosimetric robustness against multiple uncertainties into one number. The RI is defined as the ratio of scenarios passing the conditions on the dose distributions. Weighting of the scenarios in the robustness space is possible to consider their likelihood of occurrence. The robustness tool is applied on IMRT, a volumetric modulated arc therapy (VMAT), a dynamic trajectory radiotherapy (DTRT), and a dynamic mixed beam radiotherapy (DYMBER) plan for a brain case to evaluate the robustness to uncertainties of gantry‐, table‐, collimator angle, MLC, and intrafraction motion. Additionally, the robustness of the IMRT, VMAT, and DTRT plan against patient setup uncertainties are compared. The robustness tool is validated by Delta4 measurements for scenarios including all uncertainty types available.

Results

The robustness tool performs simultaneous calculation of uncertainty scenarios, and the GUI enables their fast evaluation. For all evaluated plans and uncertainties, the planning target volume (PTV) margin prevented major clinical target volume (CTV) coverage deterioration (maximum observed standard deviation of D98%CTV was 1.3 Gy). OARs close to the PTV experienced larger dosimetric deviations (maximum observed standard deviation of D2%chiasma was 14.5 Gy). Robustness comparison by RI evaluation against patient setup uncertainties revealed better dosimetric robustness of the VMAT and DTRT plans as compared to the IMRT plan. Delta4 validation measurements agreed with calculations by >96% gamma‐passing rate (3% global/2 mm).

Conclusions

The robustness tool was successfully implemented. Calculation and evaluation of uncertainty scenarios with the robustness tool were demonstrated on a brain case. Effects of patient and machine‐specific uncertainties and the combination thereof on the dose distribution are evaluated in a user‐friendly GUI to quantitatively assess and compare treatment plans and their robustness.

A hybrid column generation and simulated annealing algorithm for direct aperture optimization

The purpose of this work was to develop a hybrid column generation (CG) and simulated annealing (SA) algorithm for direct aperture optimization (H-DAO) and to show its effectiveness in generating high quality treatment plans for intensity modulated radiation therapy (IMRT) and mixed photon-electron beam radiotherapy (MBRT). The H-DAO overcomes limitations of the CG-DAO with two features improving aperture selection (branch-feature) and enabling aperture shape changes during optimization (SA-feature). The H-DAO algorithm iteratively adds apertures to the plan. At each iteration, a branch is created for each field provided. First, each branch determines the most promising aperture of its assigned field and adds it to a copy of the current apertures. Afterwards, the apertures of each branch undergo an MU-weight optimization followed by an SA-based simultaneous shape and MU-weight optimization and a second MU-weight optimization. The next H-DAO iteration continues the branch with the lowest objective function value. IMRT and MBRT treatment plans for an academic, a brain and a head and neck case generated using the CG-DAO and H-DAO were compared. For every investigated case and both IMRT and MBRT, the H-DAO leads to a faster convergence of the objective function value with number of apertures compared to the CG-DAO. In particular, the H-DAO needs about half the apertures to reach the same objective function value as the CG-DAO. The average aperture areas are 27% smaller for H-DAO than for CG-DAO leading to a slightly larger discrepancy between optimized and final dose. However, a dosimetric benefit remains. The H-DAO was successfully developed and applied to IMRT and MBRT. The faster convergence with number of apertures of the H-DAO compared to the CG-DAO allows to select a better compromise between plan quality and number of apertures.

Phantom-based prospective analysis of the accuracy of photo registration technology in electromagnetic navigation of the frontal skull base

OBJECTIVE

This prospective study compared the accuracy of two different company-specific registration methods (Fiagon GmbH, Hennigsdorf, Germany) in the electromagnetic navigation of the frontal skull base. A newly developed photo registration technology (Fiagon tracey©) promises an increase in accuracy and user-friendliness, but there is no phantom-based prospective study comparing the new method with the classic approach of tactile surface registration.

MATERIALS AND METHODS

A phantom skull was prepared with 27 markers in the sagittal, axial and coronary planes, and their reference coordinates were determined using a navigational CT (low dose, slice 0.6 mm). Subsequently, 20 runs of automatic photo registration and tactile surface registration were carried out, and the resulting marker coordinates were compared with the reference coordinates. The target registration error (TRE) of the 27 markers was assessed and compared between the two methods using a 2-factor ANOVA with repeated measures.

RESULTS

The mean TRE using surface registration was 1.97 mm ± 0.57, while the mean TRE of the automatic photo registration was 1.54 mm ± 0.24 (p < 0.001). In a subgroup analysis limited to markers in anatomical regions of clinical relevance in terms of paranasal sinus surgery, the mean TRE for the photo registration procedure can even be reduced to 1.29 mm (± 0.43) compared to tactile registration (1.80 mm; ±0.50; p=0.01).

CONCLUSIONS

Photo registration is a promising new technology in the field of electromagnetic navigation in paranasal sinus surgery. This prospective phantom-based study showed that the photo registration method achieves a significantly lower target registration error (1.29 mm) compared to the surface-based tactile registration procedure (1.80 mm).

Effect of exercise training on vascular function and endothelial repair in heart failure with preserved ejection fraction: results from the OptimEx trial

Background

Exercise training improves peak oxygen uptake (VO2) in heart failure with preserved ejection fraction (HFpEF), but the underlying mechanisms are unknown. In other cardiovascular diseases, exercise training improves vascular function and increases levels of circulating endothelium-repairing cells. We aimed to investigate the effects of moderate continuous training (MCT) and high intensity interval training (HIIT) on vascular function and cellular endothelial repair in HFpEF.

Methods

This was a prespecified subanalysis of the Optimizing Exercise Training in Prevention and Treatment of Diastolic Heart Failure randomized trial. HFpEF patients (n=180) were randomized to HIIT, MCT or attention control. At baseline and after 12 weeks, we measured peak VO2, fingertip arterial tonometry (n=109), brachial artery flow-mediated dilation (n=59), aortic pulse wave velocity (n=94), and flow cytometry (n=136) for endothelial progenitor cells (CD45dimCD34+VEGFR2+) and angiogenic T cells (CD3+CD31+CD184+). Changes in these parameters were compared between groups using linear mixed models. Parameters were correlated using Spearman's rho.

Results

At 3 months, we did not observe significant differences between HIIT, MCT and control group regarding changes in vascular function throughout the vascular tree (fingertip arterial tonometry, brachial artery flow-mediated dilation and central arterial stiffness, Table 1) or levels of circulating endothelium-repairing cells (endothelial progenitor cells and angiogenic T cells, Table 1). Results were similar at 12 months and when restricting analysis to patients with at least 70% adherence to training sessions. Patients with higher peak VO2 at baseline had lower numbers of circulating endothelial progenitor cells (rho=−0.22, p=0.011).

Conclusions

In patients with HFpEF, exercise training did not change vascular function or levels of endothelium-repairing cells. Thus, improved vascular function likely does not contribute to the change in peak VO2 after training. These findings are in contrast with the benefits of exercise on vascular function in heart failure with reduced ejection fraction and coronary artery disease.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): EU Framework Programme 7 Table 1

Hemispheric specialization for nonverbal gestures depicting motion and space

INTRODUCTION

The right hemispheric specialisation for mental rotation suggests a left hand preference for nonverbal gestures that depict spatial information. We therefore hypothesized that nonverbal depictions of spatial information are preferentially demonstrated by the left hand, i.e., are grounded in right hemispheric functions.

METHODS

Right-handed participants were asked in two experiments to nonverbally demonstrate how to move tachistoscopically presented (in the left or right visual hemifields) geometric objects of different rotations into an identical final position. Two independent blind raters evaluated the videotaped hand gestures employing the Neuropsychological Gesture (NEUROGES) Coding System.

RESULTS

Pantomime gestures increase in order to rotate gravitationally unstable objects whereas spatial relation presentation gestures increase when to nonverbally demonstrate a gravitationally stable object. Individuals preferred the right hand for pantomime gestures but the left hand for spatial relation presentation gestures.

DISCUSSION

Individuals increase their pantomime gestures to nonverbally depict motion particularly with the right hand, i.e. the left hemisphere. In contrast, increased left hand spatial relation presentations gestures indicate that those gestures are of right hemispheric origin. Thus, the hemispherical lateralization of nonverbal gestures seems to depend on the hands' functional depiction.

TriB-RT: Simultaneous optimization of photon, electron and proton beams

PURPOSE

To develop a novel treatment planning process (TPP) with simultaneous optimization of modulated photon, electron and proton beams for improved treatment plan quality in radiotherapy.

METHODS

A framework for fluence map optimization of Monte Carlo (MC) calculated beamlet dose distributions is developed to generate treatment plans consisting of photon, electron and spot scanning proton fields. Initially, in-house intensity modulated proton therapy (IMPT) plans are compared to proton plans created by a commercial treatment planning system (TPS). A triple beam radiotherapy (TriB-RT) plan is generated for an exemplary academic case and the dose contributions of the three particle types are investigated. To investigate the dosimetric potential, a TriB-RT plan is compared to an in-house IMPT plan for two clinically motivated cases. Benefits of TriB-RT for a fixed proton beam line with a single proton field are investigated.

RESULTS

In-house optimized IMPT are of at least equal or better quality than TPS-generated proton plans, and MC-based optimization shows dosimetric advantages for inhomogeneous situations. Concerning TriB-RT, for the academic case, the resulting plan shows substantial contribution of all particle types. For the clinically motivated case, improved sparing of organs at risk close to the target volume is achieved compared to IMPT (e.g. myelon and brainstem [Formula: see text] -37%) at cost of an increased low dose bath (healthy tissue V _10% +22%). In the scenario of a fixed proton beam line, TriB-RT plans are able to compensate the loss in degrees of freedom to substantially improve plan quality compared to a single field proton plan.

CONCLUSION

A novel TPP which simultaneously optimizes photon, electron and proton beams was successfully developed. TriB-RT shows the potential for improved treatment plan quality and is especially promising for cost-effective single-room proton solutions with a fixed beamline in combination with a conventional linac delivering photon and electron fields.

Pilot Study of Hyperpolarized 13C Metabolic Imaging in Pediatric Patients with Diffuse Intrinsic Pontine Glioma and Other CNS Cancers

BACKGROUND AND PURPOSE

Pediatric CNS tumors commonly present challenges for radiographic interpretation on conventional MR imaging. This study sought to investigate the safety and tolerability of hyperpolarized carbon-13 (HP-¹³C) metabolic imaging in pediatric patients with brain tumors.

MATERIALS AND METHODS

Pediatric patients 3 to 18 years of age who were previously diagnosed with a brain tumor and could undergo MR imaging without sedation were eligible to enroll in this safety study of HP [1-¹³C]pyruvate. Participants received a one-time injection of HP [1-¹³C]pyruvate and were imaged using dynamic HP-¹³C MR imaging. We assessed 2 dose levels: 0.34 mL/kg and the highest tolerated adult dose of 0.43 mL/kg. Participants were monitored throughout imaging and for 60 minutes postinjection, including pre- and postinjection electrocardiograms and vital sign measurements.

RESULTS

Between February 2017 and July 2019, ten participants (9 males; median age, 14 years; range, 10-17 years) were enrolled, of whom 6 completed injection of HP [1-¹³C]pyruvate and dynamic HP-¹³C MR imaging. Four participants failed to undergo HP-¹³C MR imaging due to technical failures related to generating HP [1-¹³C]pyruvate or MR imaging operability. HP [1-¹³C]pyruvate was well-tolerated in all participants who completed the study, with no dose-limiting toxicities or adverse events observed at either 0.34 (n = 3) or 0.43 (n = 3) mL/kg. HP [1-¹³C]pyruvate demonstrated characteristic conversion to [1-¹³C]lactate and [¹³C]bicarbonate in the brain. Due to poor accrual, the study was closed after only 3 participants were enrolled at the highest dose level.

CONCLUSIONS

Dynamic HP-¹³C MR imaging was safely performed in 6 pediatric patients with CNS tumors and demonstrated HP [1-¹³C]pyruvate brain metabolism.

Selection for increased cranial capacity in small mammals during a century of urbanization

Urbanization is a selective force that is known to drive changes in the population dynamics of wildlife. How animals adapt to changing environmental conditions is crucial to their survival in these environments. Relative brain size, or cranial capacity, is a known proxy of behavioral flexibility, and can be used to assess how well a species has adapted to a particular environment. We examined changes in cranial capacity in a time series of small mammal skulls collected from urban and rural populations in southwestern Pennsylvania. Skulls from urban populations were collected from Allegheny County, an area that experienced rapid urbanization over the past century, and skulls of rural populations from the Powdermill Nature Reserve of the Carnegie Museum, which has remained relatively unchanged forest over the same period. Our results show that Peromyscus leucopus and Microtus pennsylvanicus from urban populations had significantly greater cranial capacity than their rural counterparts, but the opposite was true for Eptesicus fuscus. We found no difference in relative cranial capacity across time in any of the small mammal species. Our results suggest that a larger cranial capacity is selected for in an urban environment and reinforces the hypothesis that behavioral flexibility is important for animals to adapt to novel environments.

The prognostic value of preprocedural high-sensitivity troponin T in patients with severe aortic stenosis undergoing valve replacement: a gender analysis

Introduction

Recent studies have demonstrated the predictive value of preprocedural cardiac biomarkers, such as N-terminal pro brain natriuretic peptide (NT-proBNP) and high-sensitivity troponin T (hsTnT), in patients with severe aortic valve stenosis undergoing valve replacement. Nonetheless, it remains still unclear whether hsTnT may be influenced by gender-specific differences.

Purpose

The aim of this subanalysis was to evaluate sex-related differences of preprocedural hsTnT in predicting postoperative long-term survival in a large cohort undergoing either surgical or transcatheter aortic valve replacement.

Methods

The TASS-2 group, a consortium of four university hospital centers, analysed 3595 consecutively enrolled patients admitted for valve implantation because of severe aortic stenosis between 2007 and 2017.

Results

The study cohort consisted of 1728 (48.1%) female and 1867 (51.9%) male patients. During a median follow-up of 2.9 years, cardiovascular mortality was found in 556 (15.5%) patients, amongst whom were 292 (16.9%) women and 264 (14.1%) men. All-cause mortality was detected in 919 (25.6%) patients dividing into 462 (26.7%) women and 457 (24.5%) men.

Preprocedural hsTnT was significantly higher (p&lt;0.001) in male (19 ng/l, 11.8–34.0) than in female (16 ng/l, 10.0–30.0) patients. In contrary, NT-proBNP was lower (p=0.002) in male (1286 ng/l, 444.5–3225.5) than female (1407 ng/l, 604.5–3217.5) patients. For the univariate analysis of survival, hsTnT was categorized by using predefined subgroups (&lt;5 ng/l; 5–13.99 ng/l; 14–50 ng/l; &gt;50 ng/l). Cardiovascular and all-cause mortality were significantly increased with higher hsTnT plasma levels in women (p&lt;0.001) as well as in men (&lt;0.001).

In two separate multivariate cox regression models, one for either gender - adjusting for STS risk score, NT-proBNP plasma levels, degree of left ventricular systolic dysfunction, atrial fibrillation, age, renal function, chronic obstructive pneumonic disease, arterial hypertension, diabetes mellitus, concomitant significant coronary artery disease and type of procedure – pre-procedural hsTnT was a strong independent predictor for postoperative cardiovascular mortality with an hazard ratio [HR] of 3.34, 95% confidence interval [CI] 1.03–10.80, P=0.044 for mildly to moderately elevated hsTnT (14–50 ng/l) and an HR of 3.98, CI 1.19–13.30, P=0.025 for severely elevated hsTnT (&gt;50 ng/l) in women, whereas an hazard ratio [HR] 4.09, 95% confidence interval [CI] 0.55–29.99, P=0.166 for mildly to moderately elevated hsTnT (14–50 ng/l) and an HR 7.48, CI 0.99–56.12, P=0.050 for severely elevated hsTnT (&gt;50 ng/l) in men was yielded.

Conclusion

Long-term postoperative survival in patients with severe AS admitted for valve implantation was independently predicted by hsTnT, irrespective of gender.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): Tiroler Wissenschaftsförderung (Innsbruck, Austria)

Diffusion Characteristics of Pediatric Diffuse Midline Gliomas with Histone H3-K27M Mutation Using Apparent Diffusion Coefficient Histogram Analysis

BACKGROUND AND PURPOSE

Diffuse midline gliomas with histone H3 K27M mutation are biologically aggressive tumors with poor prognosis defined as a new diagnostic entity in the 2016 World Health Organization Classification of Tumors of the Central Nervous System. There are no qualitative imaging differences (enhancement, border, or central necrosis) between histone H3 wildtype and H3 K27M-mutant diffuse midline gliomas. Herein, we evaluated the utility of diffusion-weighted imaging to distinguish H3 K27M-mutant from histone H3 wildtype diffuse midline gliomas.

MATERIALS AND METHODS

We identified 31 pediatric patients (younger than 21 years of age) with diffuse gliomas centered in midline structures that had undergone assessment for histone H3 K27M mutation. We measured ADC within these tumors using a voxel-based 3D whole-tumor measurement method.

RESULTS

Our cohort included 18 infratentorial and 13 supratentorial diffuse gliomas centered in midline structures. Twenty-three (74%) tumors carried H3-K27M mutations. There was no difference in ADC histogram parameters (mean, median, minimum, maximum, percentiles) between mutant and wild-type tumors. Subgroup analysis based on tumor location also did not identify a difference in histogram descriptive statistics. Patients who survived <1 year after diagnosis had lower median ADC (1.10 × 10^-3mm²/s; 95% CI, 0.90-1.30) compared with patients who survived >1 year (1.46 × 10^-3mm²/s; 95% CI, 1.19-1.67; P < .06). Average ADC values for diffuse midline gliomas were 1.28 × 10^-3mm²/s (95% CI, 1.21-1.34) and 0.86 × 10^-3mm²/s (95% CI, 0.69-1.01) for hemispheric glioblastomas with P < .05.

CONCLUSIONS

Although no statistically significant difference in diffusion characteristics was found between H3-K27M mutant and H3 wildtype diffuse midline gliomas, lower diffusivity corresponds to a lower survival rate at 1 year after diagnosis. These findings can have an impact on the anticipated clinical course for this patient population and offer providers and families guidance on clinical outcomes.

MANTRA: a serious game improving knowledge of maternal and neonatal health and geohazards in Nepal

Background

Mobile technology is increasingly important for delivering public health interventions to remote populations. This research study developed, piloted, and assessed a serious game for mobile devices that teaches geohazard, maternal, and neonatal health messages. This unique mHealth intervention aimed at low-literacy audiences in low resource settings is part of the Maternal and Neonatal Technologies in Rural Areas (MANTRA) project: Increasing maternal and child health resilience before, during, and after disasters using mobile technology in Nepal. Specifically, we assess impact of the serious game to improve knowledge gain in our target audience.

Methods

Co-creation with the MANTRA team and local stakeholders in Nepal identified core needs, developed appropriate pictograms and mechanics, and tailored the pilot game to the local cultural context. Through picture matching with immediate audio and visual feedback, the game teaches 28 learning objectives in three modules: maternal health, neonatal health, and geohazards. To assess the game, 35 participants were recruited in Kathmandu and villages in Kavre district. Sessions consisted of pre-test assessment, playing the game, post-test assessment, and a focus group to elicit qualitative feedback.

Results

The knowledge assessment quantified knowledge gain. Overall, the group averaged a normalized 6.8 point improvement (p = 0.000022). Change in the geohazard module was 9.5 points (p = 0.001), followed by maternal health (7.4 points, p = 0.007), and neonatal health (4.3 points, p = 0.83). Four learning objectives had statistically significant change (p &lt; 0.05). Feedback demonstrated high engagement, motivation, and usability of the game.

Conclusions

This MANTRA study is a unique mhealth intervention of a serious game to teach core health and hazards messages to low-literacy audiences in rural Nepal. The pilot intervention demonstrated statistically significant knowledge improvement among participants.

Key messages

The pilot MANTRA mobile serious game intervention is a novel idea, to bring public health knowledge to difficult to reach vulnerable populations, including often ignored illiterate audiences. The pilot MANTRA mobile serious game intervention demonstrated a statistically significant knowledge improvement of geohazard, maternal, and neonatal health learning objectives among participants.

Dynamic intracochlear pressure measurement during cochlear implant electrode insertion

Background: Electrode insertion into the cochlea can cause significant pressure changes inside the cochlea with assumed effects on the cochlea's functionality regarding residual hearing. Model-based intracochlear pressure (ICP) changes were performed statically at the cochlear helix. Aims/objectives: The aim of this study was to observe dynamic pressure measurements during electrode insertion directly at the cochlear implant electrode. Material and methods: The experiments were performed in an uncurled cochlear model that contained a volume value equivalent to a full cochlea. A microfibre pressure sensor was attached at one of two positions on a cochlear implant electrode and inserted under different insertional conditions. Results: We observed the ICP increase depending on the insertional depth. A sensor-position-specific pressure change is insertional-depth dependent. Interval insertion did not lead to a lower peak insertional ICP. Conclusions and significance: In contrast to the static pressure-sensor measurement in the artificial model's helix, a dynamic measurement directly at the electrode shows the pressure profile to increase based on the insertional depth. A mechanical traumatic relevance of the observed pressure values cannot be fully excluded.

P4665High sensitivity troponin t and n-terminal pro brain natriuretic peptide plasma levels predict long-term postoperative survival in patients with severe aortic stenosis admitted for valve implantation

Aims

Optimal timing of valve implantation in patients with severe aortic stenosis (AS) is under debate, considering the subjective nature of symptom onset. We aimed to investigate the pre-procedural value of routinely available cardiac biomarkers in predicting postoperative long-term outcome in a large cohort undergoing either surgical or transcatheter aortic valve implantation.

Methods

The Tyrolean Aortic Stenosis Study-2 (TASS-2) group, a consortium of four university hospital centers in Austria, analysed pre-procedural high-sensitivity troponin T (hsTnT) and N-terminal pro brain natriuretic peptide (NT-proBNP) plasma levels in 3595 patients admitted for valve implantation because of severe aortic stenosis since 2007.

Results

Transcatheter aortic valve implantation was performed in 1517 (42.2%) of patients. During a median follow-up of 2.93 (1.91–4.92) years, 919 patients (25.6%) died, among them 556 (15.5%) due to cardiovascular causes. In multivariate cox regression analysis - adjusting for STS risk score (intermediate risk 4–8%, high risk >8%), degree of left ventricular systolic dysfunction (ejection fraction 30–50% and <30%), atrial fibrillation, sex, age, renal function, COPD, arterial hypertension, diabetes mellitus, concomitant significant coronary artery disease and type of procedure (surgical aortic valve replacement or transcatheter aortic valve implantation) - pre-procedural hsTnT as well as NT-proBNP plasma levels were strong independent predictors for postoperative survival: hazard ratio [HR] 1.82, 95% confidence interval [CI] 1.07–3.11, P=0.028 for mildly to moderately elevated hsTnT (14–50 ng/l); HR 2.80, CI 1.61–4.89, P<0.001 for severely elevated hsTnT (>50 ng/l); HR 1.38, CI 1.06–1.81, P=0.018 for mildly to moderately elevated NT-proBNP (defined by an increase of up to threefold of age- and sex-corrected normal range); HR 1.68, CI 1.29–2.18, P<0.001 for severely elevated NT-proBNP (defined by an increase of more than threefold of age- and sex-corrected normal range). For direct comparison of these two biomarkers a second cox regression model was conducted including only hsTnT and NT-proBNP revealing the strength of hsTnT as a predictive biomarker: HR 2.20, 95% CI 1.29–3.77, P=0.004 for minimally elevated hsTnT (5–13.99 ng/l); HR 4.05, CI 2.41–6.82, P<0.001 for mildly to moderately elevated hsTnT (14–50 ng/l); HR 8.63, CI 5.07–14.70, P<0.001 for severely elevated hsTnT (>50 ng/l); HR 1.47, CI 1.13–1.91, P=0.004 for mildly to moderately elevated NT-proBNP; HR 1.96, CI 1.54–2.51, P<0.001 for severely elevated NT-proBNP.

Conclusion

hsTNT and NT-proBNP strongly predict long-term postoperative survival in patients with severe AS admitted for valve implantation.

Acknowledgement/Funding

This work was supported by the Tiroler Wissenschaftsförderung: grant number TWF-2017-1-5, GZ: UNI-0404-2104

P3383Left atrial appendage and left atrial morphology is associated with cryptogenic stroke

Background

Stroke causes a high burden of morbidity and mortality worldwide. Approximately 30% of stroke cases remain cryptogenic (CS), of which one third is due to occult atrial fibrillation (AF) with left atrial appendage (LAA) being the most frequent thrombus source.

Hence, aim of our study was to assess if LAA morphological parameters analysed by computed tomography angiography (CTA) are associated with CS.

Methods and materials

In 184 patients (Table 1), 82 CS patients and 102 controls (age median 62 (52,2–72), 40.2% females), matched for BMI, a CTA was performed, and LAA morphology evaluated retrospectively.

LAA morphology was classified into 5 types (Figure 1): Cactus, Cauliflower, Chicken-wing, Windsock and the new “Seahorse” with a distinctive tip angulation of ≤90° and 2 bends (Z-shape). Further measurements included: LAA tip angulation (≤90°, 91–110°, >110°), LAA lobe number, LAA ostium size (length) and angulation, left atrium wall thickness (LAWT).

Results

LAA and left atrium (LA) parameters associated with CS on multivariable analysis after adjusting for CHA2DS2-VASc score were: Chicken-wing type (OR 2.15; 95% CI: 1.01–4.56, p=0.046), a greater lobe number (OR 2.01; 95% CI: 1.52–2.64, p<0.001), a greater middle and mean LAWT (respectively, OR 2.13; 95% CI: 1.49–3.05, p<0.001, OR 2.64; 95% CI: 1.63–4.29, p<0.001), a larger (length, OR 1.08; 95% CI: 1.0–1.16, p=0.039) and a less bent LAA ostium (OR 1.02; 95% CI: 1.01–1.03, p=0.006). In contrast, a sharp-angled LAA tip (≤90°) was protective from CS (OR 0.43; 95% CI: 0.23–0.83, p=0.012) on multivariable analysis.

Table1. Clinical patient characteristics CS (n=82) Non-stroke (n=102) p value Females 21 (25.6%) 53 (52%) p<0.001 Age, y 66.5 (57–73) 57.5 (50–70) 0.001 BMI, kg/m2 25.6 (23.9–28.2) 26 (23.3–30.1) 0.320 CHA2DS2-VASc score 2 (1–3) 2 (1–3) 0.387 AF (paroxysmal/permanent) 0 4 0.071 Hypertension 68 (82.9%) 54 (56.3%) p<0.001 Diabetes mellitus, type 2 16 (19.8%) 11 (11.5%) 0.145 Values are given in median ± IQR. AF, atrial fibrillation; BMI, body mass index.

LAA and LA morphology in CTA.

Conclusion

In CS, a Chicken-wing LAA, a greater number of lobes and a thicker LA wall are independently associated with CS while a sharp LAA tip (≤90°) mostly seen in Seahorse type LAA is protective. Such “high-risk” LAA and LA morphology could help to select CS patients benefiting from extended rhythm-monitoring to detect an occult AF, however, further prospective studies are needed to confirm this hypothesis.

Benchmarking Monte-Carlo dose calculation for MLC CyberKnife treatments

Background

Vendor-independent Monte Carlo (MC) dose calculation (IDC) for patient-specific quality assurance of multi-leaf collimator (MLC) based CyberKnife treatments is used to benchmark and validate the commercial MC dose calculation engine for MLC based treatments built into the CyberKnife treatment planning system (Precision MC).

Methods

The benchmark included dose profiles in water in 15 mm depth and depth dose curves of rectangular MLC shaped fields ranging from 7.6 mm × 7.7 mm to 115.0 mm  × 100.1 mm, which were compared between IDC, Precision MC and measurements in terms of dose difference and distance to agreement. Dose distributions of three phantom cases and seven clinical lung cases were calculated using both IDC and Precision MC. The lung PTVs ranged from 14 cm³ to 93 cm³. Quantitative comparison of these dose distributions was performed using dose-volume parameters and 3D gamma analysis with 2% global dose difference and 1 mm distance criteria and a global 10% dose threshold. Time to calculate dose distributions was recorded and efficiency was assessed.

Results

Absolute dose profiles in 15 mm depth in water showed agreement between Precision MC and IDC within 3.1% or 1 mm. Depth dose curves agreed within 2.3% / 1 mm. For the phantom and clinical lung cases, mean PTV doses differed from − 1.0 to + 2.3% between IDC and Precision MC and gamma passing rates were > =98.1% for all multiple beam treatment plans. For the lung cases, lung V20 agreed within ±1.5%. Calculation times ranged from 2.2 min (for 39 cm³ PTV at 1.0 × 1.0 × 2.5 mm³ native CT resolution) to 8.1 min (93 cm³ at 1.1 × 1.1 × 1.0 mm³), at 2% uncertainty for Precision MC for the 7 examined lung cases and 4–6 h for IDC, which, however, is not optimized for efficiency but used as a gold standard for accuracy.

Conclusions

Both accuracy and efficiency of Precision MC in the context of MLC based planning for the CyberKnife M6 system were benchmarked against MC based IDC framework. Precision MC is used in clinical practice at our institute.

Swiss consumers' willingness to pay and attitudes regarding dual-purpose poultry and eggs

Chick culling is an efficient and cost-effective method in modern poultry farming, but it raises ethical concerns. Dual-purpose poultry (DP), in which males are fattened and females are used for egg production, is currently the most realistic alternative to culling, as in ovo sexing is not yet viable for practical application. Consumers' acceptance of DP products and their willingness to pay (WTP) for them have not been studied yet, and we expect that both aspects are closely related to the acceptance of and WTP for products from systems claiming beyond-conventional animal welfare, such as organic products. Results from a survey conducted among 402 consumers at 8 Swiss supermarkets revealed that the practice of chick culling was largely unknown (75% of respondents). Generally, respondents' knowledge about poultry production was low. The DP alternative was preferred to chick culling, but no preference emerged between DP and in ovo sexing. Furthermore, the WTP for DP products was proportionally lower for chicken than for eggs, probably because of the different price elasticity between these products. A regression analysis was used to determine the factors influencing consumers' WTP for DP products. Consumers' WTP was positively related to knowledge about poultry production, habits tied to purchasing organic or free-range poultry products, and familiarity with DP products. Therefore, a combination of the DP alternative with an organic label is recommended.

Part 2: Dynamic mixed beam radiotherapy (DYMBER): Photon dynamic trajectories combined with modulated electron beams

PURPOSE

The purpose of this study was to develop a treatment technique for dynamic mixed beam radiotherapy (DYMBER) utilizing increased degrees of freedom (DoF) of a conventional treatment unit including different particle types (photons and electrons), intensity and energy modulation and dynamic gantry, table, and collimator rotations.

METHODS

A treatment planning process has been developed to create DYMBER plans combining photon dynamic trajectories (DTs) and step and shoot electron apertures collimated with the photon multileaf collimator (pMLC). A gantry-table path is determined for the photon DTs with minimized overlap of the organs at risk (OARs) with the target. In addition, an associated dynamic collimator rotation is established with minimized area between the pMLC leaves and the target contour. pMLC sequences of photon DTs and electron pMLC apertures are then simultaneously optimized using direct aperture optimization (DAO). Subsequently, the final dose distribution of the electron pMLC apertures is calculated using the Swiss Monte Carlo Plan (SMCP). The pMLC sequences of the photon DTs are then re-optimized with a finer control point resolution and with the final electron dose distribution taken into account. Afterwards, the final photon dose distribution is calculated also using the SMCP and summed together with the one of the electrons. This process is applied for a brain and two head and neck cases. The resulting DYMBER dose distributions are compared to those of dynamic trajectory radiotherapy (DTRT) plans consisting only of photon DTs and clinically applied VMAT plans. Furthermore, the deliverability of the DYMBER plans is verified in terms of dosimetric accuracy, delivery time and collision avoidance. For this purpose, The DYMBER plans are delivered to Gafchromic EBT3 films placed in an anthropomorphic head phantom on a Varian TrueBeam linear accelerator.

RESULTS

For each case, the dose homogeneity in the target is similar or better for DYMBER compared to DTRT and VMAT. Averaged over all three cases, the mean dose to the parallel OARs is 16% and 28% lower, D2% to the serial OARs is 17% and 37% lower and V10% to normal tissue is 12% and 4% lower for the DYMBER plans compared to the DTRT and VMAT plans, respectively. The DYMBER plans are delivered without collision and with a 4-5 min longer delivery time than the VMAT plans. The absolute dose measurements are compared to calculation by gamma analysis using 2% (global)/2 mm criteria with passing rates of at least 99%.

CONCLUSIONS

A treatment technique for DYMBER has been successfully developed and verified for its deliverability. The dosimetric superiority of DYMBER over DTRT and VMAT indicates utilizing increased DoF to be the key to improve brain and head and neck radiation treatments in future.