Noncoplanar Geometry Research Articles

EP.08C.02 Impact of Non-Coplanar Radiation Beam Geometry on Effective Dose to Immune Cells (EDIC) In Stage III NSCLC

EP.08C.02 Impact of Non-Coplanar Radiation Beam Geometry on Effective Dose to Immune Cells (EDIC) In Stage III NSCLC

Theoretical and experimental studies on channel impulse response of short-range non-line-of-sight ultraviolet communications.

A theoretical channel impulse response (CIR) model of short-range non-line-of-sight (NLOS) ultraviolet communications (UVC) in noncoplanar geometry under the single-scatter condition is proposed. Simulation results obtained from the widely accepted Monte-Carlo (MC)-based channel model of NLOS UVC are provided to verify corresponding theoretical results obtained from the proposed theoretical single-scatter CIR model. Additionally, an outdoor experiment with a light-emitting diode (LED) as the light source is first designed to measure the channel step response of NLOS UVC and to further validate the proposed theoretical single-scatter CIR model. By varying the different parameters of the transmitter and the receiver, such as the baseline range, the inclination angle, the azimuth angle, the beam divergence angle, and the field-of-view angle, the results of the proposed theoretical single-scatter CIR model and the MC-based channel model are exhibited and further analyzed in detail. Results indicate that the computational time cost by the proposed theoretical single-scatter CIR model is decreased to less than 0.6% of the MC-based one with comparable accuracy in assessing the temporal characteristics of NLOS UVC channels. Additionally, theoretical results obtained from the proposed theoretical single-scatter CIR model manifest satisfactory agreement with corresponding experimental measurements.

Feasibility and Safety of Single-Isocenter/Multi-Lesion (SIML) HyperArc Brain SRT: Clinical Implementation and Early Outcomes

Patients with multiple brain metastases may not tolerate relatively longer treatment times for traditional stereotactic radiation therapy (SRT) with individual isocenter plans for each lesion due to discomfort or co-morbidities. SRT using a single-isocenter/multi-lesion (SIML) HyperArc volumetric modulated arc therapy (VMAT) plan with flattening filter free (FFF) beam could significantly shorten overall treatment time, and improve patient comfort, compliance, and clinic efficiency. We report early clinical results of treating multiple brain metastases with SIML HyperArc SRT. Twenty-three patients with multiple brain metastatic tumors (range, 2-9 lesions; total treated lesions, n = 96) were simulated using Encompass support and Q-fix mask, and treated with a highly-conformal SIML VMAT SRT plans via non-coplanar HyperArc geometry. Mean tumor distance to isocenter was 5.3 cm, maximum up to 7 cm. Common prescriptions were 25-30 Gy/5 fractions, 24-27 Gy/3 fractions, and 20 Gy/1 fraction prescribed to each planning target volume (PTV) using 2 mm margin around standard gross tumor volume (GTV) delineated on contrasted enhanced MP-RAGE MRI fusion. Acuros dose calculation for 6MV-FFF beam was used for tissue heterogeneity corrections. Alliance A071801 criteria was used for dose constraints to organs at risk (OAR) and target conformality. Treatment was delivered every other day with CBCT-guidance, adjustments made with 6DOF couch corrections on a medical linear accelerator, and treatment delivery time within 15 minutes. Local control rates were reported, and toxicity profile rated based on CTCAE v5.0 for brain radionecrosis, optic neuropathy, and brainstem dysfunction. All plans met Alliance A071801 requirements for each tumor coverage, dose to OAR including optic apparatus, brainstem, and spinal cord. Mean GTV and PTV volume were 9.4 cc (range, 0.3-54.8 cc) and 16.13 cc (range, 1.0-80.2 cc). Patient-specific quality assurance results were 98.3% for gamma passing criteria of 2%/2mm. Independent in-house Monte Carlo physics second check agreed with HyperArc plans by ±3.0%. Mean follow up was 6 months (range, 0.0-18.6 months). Of the 23 patients treated, 17 (74%) had post-treatment MRI imaging to assess local control and toxicity. Local control was achieved in 69/73 (95%) of treated and followed lesions. CTCAE grade 2 radionecrosis occurred in 2 patients and were managed with dexamethasone. No CTCAE grade 3+ events of radionecrosis, optic pathway dysfunction, or brainstem toxicity were observed. SIML HyperArc Brain SRT for multiple brain metastases has excellent local control and low toxicity profile in our patients. It can significantly reduce treatment delivery time as compared to traditional multiple-isocenter brain SRT or chronologically separate treatment courses and thus, help to improve patient comfort, compliance, ease of care, and clinic workflow. Longer median follow up of SIML brain SRT on larger patient cohort is warranted.

Triply differential cross sections for electron and positron impact on methane.

We here report theoretical triply differential cross sections (TDCS) for 250eV electron and positron impact ionization of the methane molecule calculated within the second-order distorted-wave Born approximation (DWBA2) for various momentum transfer conditions. The experimental data taken from Işık et al. [J. Phys. B: At., Mol. Opt. Phys. 49, 065203 (2016)] will be compared with the current theoretical predictions as well as molecular three body distorted wave (M3DW) approximation and generalized Sturmian function (GSF) theoretical models in a non-coplanar geometry. In the low analyzer scattering plane, the results obtained within the DWBA2 theory show better agreement with the experimental results compared to the GSF results. The M3DW results also exhibit agreement with the experimental results, in particular in the perpendicular plane geometry. Furthermore, significant differences between electron and positron TDCS were observed.

Static couch non-coplanar arc selection optimization for lung SBRT treatment planning

Objective. Non-coplanar arc geometry optimizations that take advantage of beam’s eye view (BEV) geometric overlap information have been proven to reduce dose to healthy organs-at-risk (OARs). Recently, a metric called mean arc distance (MAD) has been developed that quantifies the arc geometry sampling of 4π space. The purpose of this research is to combine improved BEV overlap information with MAD to generate static couch lung stereotactic body radiotherapy (SBRT) treatment plans deliverable on a C-arm linear accelerator. Approach. An algorithm utilizing the Moller–Trumbore ray-triangle intersection method was employed to compute a cost surrogate for dose to overlapping OARs using distances interpolated onto a PDD. Cost was combined with MAD for 100 000 random combinations of arc trajectories. A pathfinding algorithm for arc selection was created, balancing the contributions of MAD and 4π cost for the final trajectory. This methodology was evaluated for 18 lung SBRT patients. Cases were also planned with arcs from a clinical treatment template protocol for dosimetric and plan quality comparison. Results were evaluated using dose constraints in the context of RTOG0915. Main results. Five of six OARs had maximum dose reductions when planned with the arc trajectory optimization algorithm. Significant maximum dose reductions were found for esophagus (7.41 ± 0.91 Gy, p = 0.00019), trachea (5.56 ± 1.55 Gy, p = 0.0025), spinal cord (2.87 ± 1.13 Gy, p = 0.039), large bronchus (3.47 ± 1.49 Gy, p = 0.0075), and aorta (3.13 ± 0.99 Gy, p = 0.012). Mean dose to contralateral lung was also significantly reduced (0.50 ± 0.06 Gy, p = 0.00019). There were two significant increases in OAR doses: mean dose to ipsilateral lung (0.40 ± 0.09, p = 0.00086) and V5Gy to ipsilateral lung (1.95 ± 0.70%, p = 0.011). Paddick conformity index increased by 0.03 ± 0.02 (p = 0.14), remaining below a limit of 1.2 for both techniques. Significance. Static couch non-coplanar optimization yielded maximum dose reductions to OARs while maintaining target conformity for lung SBRT.

Experimental and Theoretical Study on Electron Momentum Spectroscopy of SF6: Distorted-Wave and Vibrational Motion.

The vibrational and distorted-wave effects are usually invoked to explain the measured electron momentum profiles for molecular orbitals. The vibrational effect can be accounted for quantitatively by a harmonic analytical quantum mechanical approach within the plane-wave impulse approximation (PWIA). On the other hand, quantitative calculation considering the distorted-wave effect was available only recently by a multicenter-three-distorted-wave (MCTDW) method (Phys. Rev. A2022, 105, 042805). Here, we report a joint experimental and theoretical investigation on electron momentum spectroscopy of SF6. The experiments were performed using a high-sensitivity (e, 2e) spectrometer employing non-coplanar symmetric geometry with incident electron energy equal to 1200 eV + binding energy. The experimental electron momentum profiles are compared with theoretical calculations by the MCTDW method at equilibrium geometry and by the PWIA method both at equilibrium geometry and considering vibrational motions. For all the measured orbitals, large discrepancies were observed between the experiments and the PWIA calculations at equilibrium geometry. For the highest occupied molecular orbital 1t1g, the vibrational effect can partly explain the high intensity of the experimental momentum profile at low momenta. For the other orbitals, the influence of the vibrational effect is negligible. On the other hand, the MCTDW calculations improve the agreement with the experiments for all the observed orbitals, indicating that the distorted-wave effect plays an important role in reproducing the measured momentum profiles of SF6.

Single-collision-induced path loss model of reflection-assisted non-line-of-sight ultraviolet communications.

By considering both scattering and reflection events as collision-induced events (CIEs), an analytical path loss model of reflection-assisted non-line-of-sight (NLOS) ultraviolet communications (UVC) is proposed with single CIE incorporated, which refers to the single-collision-induced (SCI) path loss model. More specifically, the analytical expressions of the received optical energy resulting from single-scatter and single-reflection events in reflection-assisted NLOS UVC are respectively derived. Then, in terms of those two expressions, the expression of the proposed SCI path loss model is obtained. Finally, Monte-Carlo (MC) simulations and experimental results are given to verify the correctness and effectiveness of the proposed SCI path loss model. The results manifest that the proposed SCI path loss model can work well in both coplanar and noncoplanar geometry of the reflection-assisted NLOS UVC.

Communication based on scattered laser radiation in a medium with high turbidity or in the presence of a noise source

The results of laboratory studies of an optical communication channel based on scattered radiation in the Big Aerosol Chamber of IAO SB RAS in a clean atmospheric environment, in the case of the chamber filled with vapor of the water-glycerin mixture, and in the presence of an noise laser source are analyzed. It is found that with the non-coplanar communication geometry in the chamber filled with the water-glycerin mixture, stable data transmission is possible with the azimuthal angle of orientation of the detector optical axis up to 5°. The error probability in the communication channel increases more slowly with an increase of the detector elevation angle in the chamber filled with the water-glycerin mixture than that in the chamber without this mixture does. The presence of an interfering laser radiation at a wavelength λ = 510 nm in the communication channel affects the communication quality. When the power of the noise laser source achieves 70 mW, the maximal error probability corresponds to 0.02.

Simplified Closed-Form Single-Scatter Path Loss Model of Non-Line-of-Sight Ultraviolet Communications in Noncoplanar Geometry

Considering the wide acceptability and practicability of single-scatter path loss (PL) model of non-line-of-sight (NLOS) ultraviolet communications (UVC) in noncoplanar geometry and the corresponding complexity of the triple integrals in the exact single-scatter PL model, a novel simplified PL model is proposed in this work with better analytical tractability and high accuracy. By approximately regarding the differential volume as a circular and thin plate, the triple integrals in the exact single-scatter PL model can be reduced to a single integral. With different baseline ranges between transmitter and receiver, beam divergence angles, receiver field-of-view (FOV) angles, inclination angles and azimuth angles taken into account, the results of the proposed PL model are compared with those of an exact single-scatter PL model, a Monte Carlo numerical model, and another recently reported approximate single-scatter PL model, which is called spherical crown (SC) model. Compared with the SC model, the proposed single-scatter PL model is obtained in closed form. Besides, taking the exact single-scatter PL model as the benchmark, the root-mean-square error (RMSE) of the proposed model and the SC model are calculated for comparison. It is demonstrated that the proposed model could achieve better accuracy than SC model under most conditions of our interest. Besides, it is shown that the RMSE of the proposed model is less than 0.4 dB for all considered transceiver geometry and the execution time of the proposed PL model is significantly reduced to less than 1% of the exact single-scatter PL model’s, which manifests the effectiveness of the proposed model. Finally, the experimental results are also provided to verify the correctness of the proposed model.

Electron Momentum Spectroscopy Study on the Valence Electronic Structure of Dimethyl Sulfide Considering Vibrational Effects.

We report an electron momentum spectroscopy study on the valence electronic structure of dimethyl sulfide. The binding energy and electron momentum profiles are measured using a high-sensitivity (e, 2e) apparatus employing a symmetric non-coplanar geometry at an incident energy of 1200 eV plus binding energy. The measurements are compared with the theoretical calculations by density functional theory performed both at equilibrium molecular geometry and by considering vibrational effects through a harmonic analytical quantum mechanical approach. The results demonstrate a significant influence of nuclear vibrational motions on the momentum profiles for valence orbitals of dimethyl sulfide, especially for 5b2, 1a2, and 4b2. A detailed analysis shows that the observed vibrational effects come mainly from vibrational normal modes breaking the mirror symmetry of (CH3)2S with respect to a plane perpendicular to the O-S-O plane.

Oxidized divinyl oligoacene-bridged diruthenium complexes: bridged localized radical characters and reduced aromaticity in bridge cores.

A series of bimetallic ruthenium vinyl complexes 1-5 bridged by oligoacenes were synthesized and characterized in this study. Comparative cyclic voltammetry results from 1-5 indicated that the first oxidation potential decreased gradually with the extension of conjugate ligands. Upon oxidation to singly oxidized species 1+-5+, rather small ν(CO) changes in the infrared (IR) spectra and the characteristic bands of metal-to-ligand charge transfer absorptions in the near IR (NIR) region predicted via time-dependent DFT calculations suggested that strong bridged ligands participate in redox processes. NIR absorptions were not observed in complexes 4+ and 5+ possibly because of instability in their twisted and noncoplanar geometry. Electron paramagnetic resonance results and spin density distribution demonstrated that the bridged localized degrees of 1+-5+ successively increased with the extension of oligoacene from benzene to tetracene. Further comparative analysis of neutral molecules and monocations to the aromaticity and π-electron density of bridge cores indicated a step-by-step transformation process from an aromatic to quinoidal radical upon oxidation.

Technical Note: Rotational positional error corrected intrafraction set-up margins in stereotactic radiotherapy: A spatial assessment for coplanar and noncoplanar geometry.

The aim of this study is to calculate setup margin based on six-dimensional (6D) corrected residual positional errors from kV cone beam computed tomography (CBCT) and from intrafraction projection kV imaging in coplanar and in noncoplanar couch positions in stereotactic radiotherapy. Six dimensional positional corrections were carried out before patient treatments, using a robotic couch and CBCT matching. A CBCT and stereoscopic ExacTrac image were acquired post-table position correction. Further, a series of intrafraction ExacTrac images were obtained for the variable couch position. Translational and rotational errors were identified as lateral (X), longitudinal (Y), vertical (Z); roll (Ɵ°), pitch (Φ°) and yaw (Ψ°). A total of 699 intrafraction image sets (361 coplanar and 338 noncoplanar) for 51 SRS/SRT patients were analysed. Rotational errors were corrected in terms of translational coordinates. Residual set-up margins were calculated from CBCT shifts. ExacTrac shifts give residual+intrafraction setup margins as a function of coplanar and noncoplanar couchpositions. The average residual positional error obtained from CBCT in X, Y, Z, Ɵ, Φ, Ψ were 0.1±0.4mm, 0.0±0.6mm,0.0±0.5mm, 0.2±0.8°, 0.1±0.6° and -0.1±0.7° respectively. For ExacTrac, the shits were -0.5±0.9mm, -0.0±1mm, -0.6±1.0mm, 0.4±0.9°, -0.2±0.6°, and -0.0±0.8°. CBCT calculated linear setup margins in X, Y, Z direction were 0.5, 1.2, and 1mm respectively. ExacTrac yielded coplanar and noncoplanar linear setup margins were 1.2, 1.3, 1.5, 1.4, 1.5, and 2.1mm respectively. CBCT-based gross residual set-up margin is equal to 1mm. ExacTrac calculated residual plus intrafraction setup margin falls within a 2mm range; attributed to intrafraction patient movement, table position inaccuracies, and poor image fusion in noncoplanar geometry. There could be variations in the required additional margin between centers and between machines, which require further studies.

A comparative study of interference effects in (e, 2e) electron momentum profiles of CO2, ethylene and 1,3-butadiene

We report a comparative (e, 2e) study of intereference effects in the spherically-averaged electron momentum density distributions of the outermost orbitals of CO2, ethylene and 1,3-butadiene. The experiments on the three molecular orbitals, being each composed of 2p atomic orbitals, were performed in the symmetric noncoplanar geometry and at an incident electron energy of 1.2 keV. Interference patterns have then been obtained for each molecular orbital by dividing the experimental data by (e, 2e) cross section of a 2p atomic orbital calculated by using distorted wave impulse approximation. It is clearly demonstrated that interference patterns tell about constructive or destructive nature of the overlap between the constituent 2p atomic orbitals. Furthermore, it is shown that higher instrumental momentum resolution would be required for detailed studies on interference effects in cases when two of the constituent atomic orbitals with larger spatial separation are both oriented perpendicular to the molecular axis or plane.

Experimental and theoretical investigations on the valence orbitals of fluorobenzene by electron momentum spectroscopy

We report here an electron momentum spectroscopy study on the valence orbitals of fluorobenzene. The experiments are performed by a binary (e, 2e) spectrometer employing symmetric non-coplanar geometry at impact electron energies of 1200 and 800 eV plus binding energy. The experimental momentum distributions are compared with the theoretical calculations using Hartree–Fock and density functional theory methods within the framework of plane wave impulse approximation (PWIA). It is shown that the calculations are in generally good agreement with the measured electron momentum profiles, while the discrepancies can be mostly attributed to the distorted-wave effect. It is interesting to find that for the inner-valence orbitals, the pole strengths (PSs) obtained by comparing the experimental data with the theoretical calculations are different for different impact electron energies. This indicates that the PS can properly be determined only when the PWIA is fulfilled.

Field-induced topological Hall effect in the noncoplanar triangular antiferromagnetic geometry of Mn3Sn

Non-collinear triangular antiferromagnets with a coplanar spin arrangement and vanishing net magnetic moment can exhibit a large anomalous Hall effect owing to their non-vanishing momentum space Berry curvature. Here we show the existence of a large field induced topological Hall effect in the non-coplanar triangular antiferromagnetic geometry of Mn3Sn. A detailed magnetic and Hall effect measurements demonstrate the presence of three distinct Hall contributions; a high temperature anomalous Hall effect, a low temperature topological Hall effect and an intermediate temperature region with coexistence of both the effects. The origin of the observed topological Hall effect is attributed to the scalar spin chirality induced real space Berry curvature that appears when the system undergoes from a trivial non-coplanar triangular spin alignment to a topologically protected non-trivial spin texture like skyrmions by application of magnetic field at low temperatures.

Electron momentum spectroscopy study of outer valence electronic structure of pyrrole

The binding energy spectrum and electron momentum distributions (EMDs) for the outer valence shells of pyrrole molecule are measured by a high-sensitivity (e, 2e) spectrometer at incident energy of 1200 eV plus the binding energy employing non-coplanar symmetric kinematic geometry. The obtained EMDs are compared with the theoretical calculations at equilibrium molecular geometry as well as considering vibrational effect by density functional theory method. The result shows that the molecular vibrational motion has obvious influence on EMDs for some of the outer valence orbitals. The controversy over the assignment of the ionization bands, especially the positions of satellite states concerning the ionization of 1b1 orbital, in the binding energy range of 11–16.5 eV has been clarified.

Non-conventional scans in high-resolution X-ray diffraction analysis of epitaxial systems

High resolution X-ray diffraction is commonly used for the analysis of single crystalline epitaxial layers exhibiting high degree of crystal perfection. The method enables to resolve fine variations of the measured intensities and therefore is very efficient in the investigation of the structural parameters of single or multilayered epitaxial systems. In this article the method combining the standard HR technique with grazing incidence set-up is outlined. It is shown that in non-coplanar geometry the intensity distribution within the section of reciprocal space perpendicular to the sample surface, standardly scanned in coplanar geometry, can be measured at constant angle of incidence α. For asymmetric diffractions that are not accessible in coplanar geometry the value of α can be decreased to extremely low values close to zero making the method depth-sensitive. The effect of non-coplanar geometry on the angular resolution is analyzed and the possible application of φ scans in asymmetric non-coplanar geometry is discussed. The proposed scans are illustrated by measurements on selected GaN based epitaxial layers and they can be applied also to other types of epitaxial systems with medium crystal quality.

Microstructure Characterization of Multilayer Thin Coatings ZrN/Si3N4 by X‐Ray Diffraction Using Noncoplanar Measurement Geometry

The structural characterization of multilayer thin coatings is performed by X‐ray diffraction using a noncoplanar measurement geometry. The application of such a measurement geometry enables a reliable and comprehensive microstructural analysis of the material comparing to other measurement geometries due to the accessibility to a larger number of measured Bragg reflections. The important advantage of noncoplanar geometry is a measurement setup without tilting and rotating the sample. A set of profiles for different Bragg reflections is measured for several multilayer coatings with different thicknesses of individual layers; the obtained profiles are combined into a single scan for the simultaneous fittingby a theoretical curve. The broadening of the diffraction profiles is considered to be affected by a small grain size and instrumental effects, with the grains being modeled by ellipsoidal shape with two equal in‐plane axes. Based on the proposed fitting procedure, the microstructural parameters of multilayer coatings are evaluated, including the grains size in parallel and normal to the surface directions. The dependence of evaluated grains size on the measurement direction confirms the validity of the selected grains model. The microstructural parameters evaluated from noncoplanar X‐ray diffraction show a good agreement with those obtained from HRTEM and STEM techniques.

Study of multilayer microstructure by XRD using noncoplanar measurement geometry

Study of multilayer microstructure by XRD using noncoplanar measurement geometry

Noncoplanar Geometry for Mobile NLOS MIMO Ultraviolet Communication With Linear Complexity Signal Detection

In this paper, we take a first step toward the mobile support for nonline-of-sight ultraviolet (UV) links by introducing a mesh UV network framework. Spatial multiplexing noncoplanar multiple-input-multiple-output (MIMO) UV system architecture is designed geometrically for the mobile mesh network to overcome the data rate bottleneck induced by scattered UV channel. Based on the MIMO UV channel characteristics, we further propose a modified sphere decoding (SD) method to accomplish MIMO signal detection in practical spatial correlated channels at a linear computational complexity. We evaluate mobile MIMO channel responses under various geometric parameters and the feasibility of this system geometry in $2 \times 2$ and $4 \times 4$ cases. Comparison of the bit error rates (BERs) between the modified SD, zero forcing, and SD is also done. Numerical results demonstrate that compared with the traditional linear array system structure, fully multiplexing is much easier via the noncoplanar MIMO geometry under very realistic parameters and the modified SD significantly improves the MIMO signal detection complexity with bit BER performance loss.