3D Radiation Research Articles

Feasibility and Clinical Acceptability of Automation-Assisted 3D Conformal Radiotherapy Planning for Patients With Cervical Cancer in a Resource-Constrained Setting.

The Ocean Road Cancer Institute (ORCI) in Tanzania began offering 3D conformal radiation therapy (3DCRT) in 2018. Steep learning curves, high patient volume, and a limited workforce resulted in long radiation therapy (RT) planning workflows. We aimed to establish the feasibility of implementing an automation-assisted cervical cancer 3DCRT planning system. We performed chart abstractions on 30 patients with cervical cancer treated with 3DCRT at ORCI. The Radiation Planning Assistant (RPA) generated a new automated set of contours and plans on the basis of anonymized computed tomography images. Each were assessed for edit time requirements, dose-volume safety metrics, and clinical acceptability by two ORCI physician investigators. Dice similarity coefficient (DSC) agreement analysis was conducted between original and new contour sets. The average time to manually develop treatment plans was 7 days. Applying RPA, automated same-day contours and plans were developed for 29 of 30 patients (97%). Of the 29 evaluable contours, all were approved with <2 minutes of edit time. Agreement between clinical and RPA contours was highest for the rectum (median DSC, 0.72) and bladder (DSC, 0.90). Agreement was lower with the primary tumor clinical target volume (CTVp; DSC, 0.69) and elective nodal clinical target volume (CTVn; DSC, 0.63). All RPA plans were approved with <4 minutes of edit time. RPA target coverage was excellent, covering the CTVp with median V45 Gy 100% and CTVn with median V45 Gy 99.9%. Automation-assisted 3DCRT contouring yielded high levels of agreement for normal structures. The RPA met all planning safety metrics and sustained high levels of clinical acceptability with minimal edit times. This tool offers the potential to significantly decrease RT planning timelines while maintaining high-quality RT delivery in resource-constrained settings.

Multidimensional Radiation Hydrodynamics Simulations of Pulsational Pair-instability Supernovae

Stars with masses of 80–130 M ⊙ can encounter pulsational pair-instability at the end of their lives, which triggers consecutive episodes of explosive burning that eject multiple massive shells. Collisions between these shells produce bright transients known as pulsational pair-instability supernovae (PPI SNe) that may explain some extreme supernovae. In this paper, we present the first 2D and 3D radiation hydrodynamics simulations of PPI SNe with the CASTRO code. Radiative cooling causes the collided shells to evolve into thin, dense structures with hot spots that can enhance the peak luminosity of the SN by factors of 2–3. The light curve peaks at 1.9–2.1 × 1043 erg s−1 for 50 days and then plateaus at 2–3 × 1042 erg s−1 for 200 days, depending on the viewing angle. The presence of 12C and 16O and the absence of 28Si and 56Fe in its spectra can uniquely identify this transient as a PPI SN in follow-up observations. Our models suggest that multidimensional radiation hydrodynamics is required to model the evolution and light curves of all shell-collision SNe, such as Type IIne, not just PPI SNe.

Self-consistent 3D Radiative Transfer for Kilonovae: Directional Spectra from Merger Simulations

We present 3D radiative transfer calculations for the ejecta from a neutron star merger that include line-by-line opacities for tens of millions of bound–bound transitions, composition from an r-process nuclear network, and time-dependent thermalization of decay products from individual α and β − decay reactions. In contrast to expansion opacities and other wavelength-binned treatments, a line-by-line treatment enables us to include fluorescence effects and associate spectral features with the emitting and absorbing lines of individual elements. We find variations in the synthetic observables with both the polar and azimuthal viewing angles. The spectra exhibit blended features with strong interactions by Ce iii, Sr ii, Y ii, and Zr ii that vary with time and viewing direction. We demonstrate the importance of wavelength calibration of atomic data using a model with calibrated Sr, Y, and Zr data, and find major differences in the resulting spectra, including a better agreement with AT2017gfo. The synthetic spectra for a near-polar inclination show a feature at around 8000 Å, similar to AT2017gfo. However, they evolve on a more rapid timescale, likely due to the low ejecta mass (0.005 M ☉) as we take into account only the early ejecta. The comparatively featureless spectra for equatorial observers gives a tentative prediction that future observations of edge-on kilonovae will appear substantially different from AT2017gfo. We also show that 1D models obtained by spherically averaging the 3D ejecta lead to dramatically different direction-integrated luminosities and spectra compared to full 3D calculations.

Retrieving 3D distributions of atmospheric particles using Atmospheric Tomography with 3D Radiative Transfer – Part 2: Local optimization

Abstract. Our global understanding of clouds and aerosols relies on the remote sensing of their optical, microphysical, and macrophysical properties using, in part, scattered solar radiation. Current retrievals assume clouds and aerosols form plane-parallel, homogeneous layers and utilize 1D radiative transfer (RT) models. These assumptions limit the detail that can be retrieved about the 3D variability in the cloud and aerosol fields and induce biases in the retrieved properties for highly heterogeneous structures such as cumulus clouds and smoke plumes. In Part 1 of this two-part study, we validated a tomographic method that utilizes multi-angle passive imagery to retrieve 3D distributions of species using 3D RT to overcome these issues. That validation characterized the uncertainty in the approximate Jacobian used in the tomographic retrieval over a wide range of atmospheric and surface conditions for several horizontal boundary conditions. Here, in Part 2, we test the algorithm's effectiveness on synthetic data to test whether the retrieval accuracy is limited by the use of the approximate Jacobian. We retrieve 3D distributions of a volume extinction coefficient (σ3D) at 40 m resolution from synthetic multi-angle, mono-spectral imagery at 35 m resolution derived from stochastically generated cumuliform-type clouds in (1 km)3 domains. The retrievals are idealized in that we neglect forward-modelling and instrumental errors, with the exception of radiometric noise; thus, reported retrieval errors are the lower bounds. σ3D is retrieved with, on average, a relative root mean square error (RRMSE) &lt; 20 % and bias &lt; 0.1 % for clouds with maximum optical depth (MOD) &lt; 17, and the RRMSE of the radiances is &lt; 0.5 %, indicating very high accuracy in shallow cumulus conditions. As the MOD of the clouds increases to 80, the RRMSE and biases in σ3D worsen to 60 % and −35 %, respectively, and the RRMSE of the radiances reaches 16 %, indicating incomplete convergence. This is expected from the increasing ill-conditioning of the inverse problem with the decreasing mean free path predicted by RT theory and discussed in detail in Part 1. We tested retrievals that use a forward model that is not only less ill-conditioned (in terms of condition number) but also less accurate, due to more aggressive delta-M scaling. This reduces the radiance RRMSE to 9 % and the bias in σ3D to −8 % in clouds with MOD ∼ 80, with no improvement in the RRMSE of σ3D. This illustrates a significant sensitivity of the retrieval to the numerical configuration of the RT model which, at least in our circumstances, improves the retrieval accuracy. All of these ensemble-averaged results are robust in response to the inclusion of radiometric noise during the retrieval. However, individual realizations can have large deviations of up to 18 % in the mean extinction in clouds with MOD ∼ 80, which indicates large uncertainties in the retrievals in the optically thick limit. Using less ill-conditioned forward model tomography can also accurately infer optical depths (ODs) in conditions spanning the majority of oceanic cumulus fields (MOD &lt; 80), as the retrieval provides ODs with bias and RRMSE values better than −8 % and 36 %, respectively. This is a significant improvement over retrievals using 1D RT, which have OD biases between −30 % and −23 % and RRMSE between 29 % and 80 % for the clouds used here. Prior information or other sources of information will be required to improve the RRMSE of σ3D in the optically thick limit, where the RRMSE is shown to have a strong spatial structure that varies with the solar and viewing geometry.

Commissioning of a solid tank design for fan-beam optical CT based 3D radiation dosimetry.

Objective.Optical computed tomography (CT) is one of the leading modalities for imaging gel dosimeters used in the verification of complex radiotherapy treatments. In previous work, a novel fan-beam optical CT scanner design was proposed that could significantly reduce the volume of the refractive index baths that are commonly found in optical CT systems. Here, the proposed scanner has been manufactured and commissioned.Approach.Image reconstruction is performed through algebraic reconstruction technique and iterated using the fast iterative shrinkage-thresholding algorithm (FISTA) algorithm. Ray tracing for algebraic reconstruction was performed using an in-house developed ray tracing simulator. A set of Sylgard® 184 phantoms were created to commission spatial resolution, geometric deformity, contrast-to-noise ratio (CNR), and scan settings.Main Results.The scanner is capable of a 0.929 mm-1spatial resolution, observed at 200 iterations, although the spatial resolution is highly dependent on the number of iterations. The geometric distortion, measured by scanning a needle phantom with the prototype scanner as well as a conventional x-ray CT was found to be within <0.25 mm. The CNR was found to peak between 65 and 190 occurring between 50 and 100 iterations and was highly dependent on the region chosen for background noise calculation. The proposed scanner is capable of scanning and reading out slices in less than 1 min per slice.Significance.This work displays the viability of a fan-beam optical CT scanner with minimal index matching using ray-traced algebraic reconstruction.

In situ time-resolved Raman spectroscopy of nitromethane under static and dynamic compression

Energetic materials are extensively used as propellants in rockets demanding the understanding of their chemical and thermal stability for safe storage and transportation as well as ease of decomposition. Nitromethane (NM) is one such material with significant performance advantage over other mono propellants. In this manuscript, we report the detailed molecular-level behavior of NM under static and dynamic compression. Dynamic compression experiments were performed up to ∼6.4 GPa using a 2 J/8 ns Nd: YAG laser coupled with time-resolved Raman spectroscopy (TRRS) setup. Static compression experiments were performed up to ∼20 GPa using a diamond anvil cell. During laser-driven shock compression, NM undergoes three phase transitions at 1.1, 2.5, and 3.4 GPa. However, in the case of static compression, the corresponding phase transitions were observed at 0.3, 1.3–1.8, and 2.5 GPa. TRRS was also performed at 300 mJ (1.47 GW/cm2), 500 mJ (2.45 GW/cm2), and 800 mJ (3.9 GW/cm2) and intensity ratios of shocked and un-shocked Raman peaks were utilized to experimentally calculate the shock velocities, which were determined to be 2.66 ± 0.09, 3.58 ± 0.40, and 3.83 ± 0.60 km/s, respectively. These experimental results were corroborated with the one-dimensional (1D) radiation hydrodynamics simulations, performed to obtain shock pressure. The shock velocities at these laser intensities were calculated to be 2.98, 3.69, and 3.92 km/s, respectively, which are in reasonably close agreement with our observed results.

Evaluating the potential of airborne hyperspectral LiDAR for assessing forest insects and diseases with 3D Radiative Transfer Modeling

Accurately monitoring forest insects and diseases disturbances is important for managing forests and implementing effective forest quality improvement measures. However, monitoring disturbances in the lower and middle parts of the forest canopy with traditional remote sensing technologies is difficult. A new sensor called hyperspectral LiDAR (HSL) makes the monitoring of these forest disturbances possible, however, its applicability to canopy scale has not been fully studied due to the current hardware limitation. This paper assessed the potential of airborne hyperspectral LiDAR (AHSL) for monitoring forest insects and diseases stress using 3D radiative transfer modeling and in-situ measurements. A virtual 3D forest scene with explicitly described structures was first reconstructed from terrestrial laser scanning and field measurement data, upon which a number of different insects and diseases disturbance scenarios with different damage locations and stress levels were defined. AHSL point cloud and the corresponding hyperspectral image (HI) were then simulated with large-scale and remote sensing image simulation (LESS) model for each combination of the different damage locations and stress levels. LiDAR point cloud from different layers of the simulated AHSL point cloud were then extracted and rasterized into images with 3-m spatial resolution, which, along with the hyperspectral images, were used to test the insect and disease monitoring ability by using a random forest model. Results show that AHSL has significant higher overall accuracies (OA: 65.95% ∼ 89.45%) than HI (OA: 33.99% ∼ 57.02%) for predicting insects and diseases stress levels. Compared to AHSL, HI is affected by a variety of factors such as soil and shadows, resulting in poorer monitoring capability for different damage locations, with the highest classification accuracy in the case of entire canopy damage (OA: 57.02%). For AHSL, it has good classification accuracy for all damage locations, with the lowest accuracy in the case of lower canopy damage (OA: 65.95%). This study demonstrates that AHSL is a promising and reliable tool to monitor forest disturbances, especially for structural and spectral changes in the lower and middle parts of canopy, which may have great potential for early detecting forest insects and diseases.

Novel simulation for dosimetry impact of diaphragm respiratory motion in four-dimensional volumetric modulated arc therapy for esophageal cancer

Background and purposeThe diaphragm respiratory motion (RM) could impact the target dose robustness in the lower esophageal cancer (EC). We aimed to develop a framework evaluating the impact of different RM patterns quantitatively in one patient, by creating virtual four-dimensional computed-tomography (v4DCT) images, which could lead to tailored treatment for the breathing pattern. We validated virtual 4D radiotherapy (v4DRT) along with exploring the acceptability of free-breathing volumetric modulated arc therapy (FB-VMAT). Methods and MaterialsWe assessed 10 patients with superficial EC through their real 4DCT (r4DCT) scans. v4DCT images were derived from the end-inhalation computed tomography (CT) image (reference CT) and the v4DRT dose was accumulated dose over all phases. r4DRT diaphragm shifts were applied with magnitudes derived from r4DCT scans; clinical target volume (CTV) dose of v4DRT was compared with that of r4DRT to validate v4DRT. CTV dosage modifications and planning organ at risk volume (PRV) margins of the spinal cord were examined with the diaphragm movement. The percentage dose differences (ΔDx) were determined between the v4DRT and the dose calculated on the reference CT image. ResultsThe CTV ΔDx between the r4DRT and v4DRT were within 1% in cases with RM ≦ 15 mm. The average ΔD100% and ΔDmean of the CTV ranging from 5 to 15 mm of diaphragm motion was 0.3% to 1.7% and 0.1% to 0.4%, respectively. All CTV index changes were within 3% and ΔD1cc and ΔD2cc of Cord PRV were within 1%. ConclusionWe postulate a novel method for evaluating the CTV robustness, comparable to the conventional r4DCT method under the diaphragm RM ≦ 15 mm permitting an impact of within 3% in FB-VMAT for EC on the CTV dose distribution.

A Novel Setup Technique for Radiation Treatment of a Severely Obese Patient With a Primary Brain Tumor.

Modern external beam radiation therapy (EBRT) techniques rely on the accurate positioning of the patient using the treatment couch. These motorized couches have weight limits that have decreased over time and are not able to support severely obese patients requiring EBRT. We aimed to develop a technique to support obese patients who are above their weight tolerance while accurately delivering radiation treatment to a brain tumor. This technique was used on a patient receiving adjuvant radiation for gliosarcoma, a variant of glioblastoma. The patient was CT scanned, and the 3D conformal radiation therapy plan was created. A custom treatment couch was created using a transport stretcher, Styrofoam, a CT couch-top, and an IMRT board, which allowed for a thermoplastic mask to be used for a reproducible setup. AP and lateral portal films were taken prior to each treatment to confirm the accuracy of the manual daily setup of the patient on the custom couch. The patient received 60 Gy in 30 daily fractions of 3DCRT in a reproducible fashion. The average deviation from the isocenter fell within the 10 mm and 8 mm planning margins applied to the clinical target volume (CTV) for the initial and boost fields, respectively. The average daily shifts in the anterior-posterior (AP) direction for the patient were 7.97 (-16.19 to 12.04) mm and 1.98 mm (-1.1 to 4.3) mm for the initial and boost treatments, respectively. The average daily shifts in the superior-inferior (SI) direction were 2.2 (-5.08 to 9.04) mm and 3.88 (-2.9 to 8.0) mm for the initial and boost treatments, respectively. This novel approach allowed treatment at 60 Gy for a gliosarcoma patient who had previously been denied treatment due to his weight. By utilizing readily available materials within the department, our team was able to create a reproducible setup technique to safely treat the patient.

Design of a compact wideband bi-directional pattern antenna for 5G applications

In this research, a wideband bi-directional pattern antenna implemented by a circular monopole encircled with an enforced-radiation circular ring incorporated with inversed L-shaped stub is designed to operate over the mid-band of 5G applications ranging from 2 to 6 GHz. It is contrived of a copper overlaid on FR4 substrate with relative permittivity of 4.3 and height of 1.6 mm. This proposed antenna is fed by a 50-ohm coplanar waveguide, which is printed on the same side of the radiated circular monopole. To further enrich the impedance matching, a pair of etched slots is added-on the ground plane near the fed line to reduce the return loss. In the study, the initial parameters are theoretically worked out, and then simulation is then performed by using an electromagnetic solutions tool to numerically discover the set of solution parameters. From the simulation results, this proposed antenna offers the |S11|&lt;–10 dB covered the operating frequency running from 1.79 to over 8 GHz with fractional bandwidth 126.90 % and 1.74 to 7.07 GHz with fractional bandwidth 101.04 % for the simulation excluded and included SMA, respectively. It provides a linear polarization with total efficiency better than 81.5 %. After that, an antenna prototype with compact dimensions of 45×45×0.6 mm3 was fabricated and testified to validate the simulation results. The measurement results provide a stability bi-directional pattern with peak gain of 5.54 dBi covering a 10 dB return loss bandwidth of 118.5 % (1.93–7.54 GHz). Simulated |S11|, 2D radiation pattern and gain are reasonably in good agreement with experimental results. Furthermore, this proposed antenna is compared with the current compact, wideband and 5G antenna to indicate its prospective for the interested bands

Economical Evaluation of Cancer Types Using Intensity-Modulated Radiation Therapy Compared to 3D Conformal Radiation Therapy: A Systematic Review.

Cancer is the second most common cause of death worldwide. Economic evaluation of cancer treatment to reduce costs can save the health care system millions of dollars while optimizing care. Therefore, this systematic review aimed to study the economic evaluation of cancer treatment using intermediate intensity radiation therapy (IMRT) compared to conventional 3D conformal radiation therapy (3D-CRT). Literatures from PubMed, Embase, Cochran Library, Google scholar, Scopus and Iranian databases were retrieved since Jan 2000 to Apr 2020 for eligible English studies. The quality of the studies was evaluated using Cheers' checklist and then the textual data were analyzed manually by content analysis method. Overall, 1790 articles were retrieved, of which 12 studies were reviewed. The article quality score ranged from 14.5 to 23 out of a maximum of 24 points. Eleven studies referred to cost-effectiveness analysis and one study referred to cost-utility analysis. Studies have been conducted in the United States, Canada, Australia, Brazil, the Netherlands, the United Kingdom, and Hungary. IMRT appears to be a cost-effective treatment strategy for rectal cancer, soft tissue sarcoma, and localized carcinoma of the pharynx, and for prostate cancer in terms of prolonging survival, but it is a cost-effective treatment strategy for head cancer. In addition, the neck was not in India's cancer control program. The results can help to decide whether to use radiation therapy and radiotherapy in the standard treatment path. Furthermore, they underline that IMRT treatment technique was cost effective for a long-time care service.

Asymptotic stability of viscous contact wave to a radiation hydrodynamic limit model

This paper is concerned with the large time behavior of the solutions for 1D radiation hydrodynamic limit model without viscosity and its asymptotic stability of the viscous contact discontinuity wave under the smallness assumption of the strength of the contact wave and initial perturbations. The present pressure includes a fourth-order term about the absolute temperature from radiation effect which brings the main difficulty. Furthermore, the dissipative of the system is weaker for the lack of viscosity. All these make the problem more challenging. The prove is mainly based on the energy method, including normal and radial directions energy estimates.

Turbulence-supported Massive Star Envelopes

The outer envelopes of massive (M ≳ 10 M ⊙) stars exhibit large increases in opacities from forests of lines and ionization transitions (particularly from iron and helium) that trigger near-surface convection zones. One-dimensional (1D) models predict density inversions and supersonic motions that must be resolved with computationally intensive three-dimensional (3D) radiation hydrodynamic (RHD) modeling. Only in the last decade have computational tools advanced to the point where ab initio 3D models of these turbulent envelopes can be calculated, enabling us to present five 3D RHD Athena++ models (four previously published and one new 13 M ⊙ model). When convective motions are subsonic, we find excellent agreement between 3D and 1D velocity magnitudes, stellar structure, and photospheric quantities. However, when convective velocities approach the sound speed, hydrostatic balance fails as the turbulent pressure can account for 80% of the force balance. As predicted by Henyey, we show that this additional pressure support leads to a modified temperature gradient, which reduces the superadiabaticity where convection is occurring. In addition, all five models display significant overshooting from the convection in the Fe convection zone. As a result, the turbulent velocities at the surface are indicative of those in the Fe zone. There are no confined convection zones as seen in 1D models. In particular, helium convection zones seen in 1D models are significantly modified. Stochastic low-frequency brightness variability is also present in the 13 M ⊙ model with comparable amplitude and characteristic frequency to observed stars.

Fetal and Maternal Atomic Bomb Survivor Dosimetry Using the J45 Pregnant Female Phantom Series: Considerations of the Kneeling and Lying Posture with Comparisons to the DS02 System.

Organ dosimetry data of the atomic bomb survivors and the resulting cancer risk models derived from these data are currently assessed within the DS02 dosimetry system developed through the Joint US-Japan Dosimetry Working Group. In DS02, the anatomical survivor models are limited to three hermaphroditic stylized phantoms-an adult (55 kg), a child (19.8 kg), and an infant (9.7 kg)-that were originally designed for the preceding DS86 dosimetry system. As such, organ doses needed for assessment of in-utero cancer risks to the fetus have continued to rely upon the use of the uterine wall in the adult non-pregnant stylized phantom as the dose surrogate for all fetal organs regardless of gestational age. To address these limitations, the Radiation Effects Research Foundation (RERF) Working Group on Organ Dose (WGOD) has established the J45 (Japan 1945) series of high-resolution voxel phantoms, which were derived from the UF/NCI series of hybrid phantoms and scaled to match mid-1940s Japanese body morphometries. The series includes male and female phantoms-newborn to adult-and four pregnant female phantoms at gestational ages of 8, 15, 25, and 38 wk post-conception. In previous studies, we have reported organ dose differences between those reported by the DS02 system and those computed by the WGOD using 3D Monte Carlo radiation transport simulations of atomic bomb gamma-ray and neutron fields for the J45 phantoms series in their traditional "standing" posture, with some variations in their facing direction relative to the bomb hypocenter. In this present study, we present the J45 pregnant female phantoms in both a "kneeling" and "lying" posture and assess the dosimetric impact of these more anatomically realistic survivor models in comparison to current organ doses given by the DS02 system. For the kneeling phantoms facing the bomb hypocenter, organ doses from bomb source photon spectra were shown to be overestimated by the DS02 system by up to a factor of 1.45 for certain fetal organs and up to a factor of 1.17 for maternal organs. For lying phantoms with their feet in the direction of the hypocenter, fetal organ doses from bomb source photon spectra were underestimated by the DS02 system by factors as low as 0.77, while maternal organ doses were overestimated by up to a factor of 1.38. Organs doses from neutron contributions to the radiation fields exhibited an increasing overestimation by the DS02 stylized phantoms as gestational age increased. These discrepancies are most evident in fetal organs that are more posterior within the mother's womb, such as the fetal brain. Further analysis revealed that comparison of these postures to the original standing posture indicate significant dose differences for both maternal and fetal organ doses depending on the type of irradiation. Results from this study highlight the degree to which the existing DS02 system can differ from organ dosimetry based upon 3D radiation transport simulations using more anatomically realistic models of those survivors exposed during pregnancy.

Generation of high circular polarization of interstellar Lyman α radiation triggering biological homochirality

ABSTRACT The homochirality of biological molecules on Earth is a long-standing mystery regarding the origin of life. Circularly polarized ultraviolet (UV) light could induce the enantiomeric excess of biological molecules in the interstellar medium, leading to the homochirality on Earth. By performing 3D radiation transfer simulations with multiple scattering processes in interstellar dusty slabs, we study the generation of the circular polarization (CP) of UV light at Lyα ($\lambda = 0.1216~{\rm \mu m}$) as well as at near-infrared (NIR, $\lambda = 2.14~{\rm \mu m}$) wavelengths. Our simulations show that the distributions of CP exhibit a symmetric quadrupole pattern, regardless of wavelength and viewing angle. The CP degree of scattered light from a dusty slab composed of aligned grains is ∼15 per cent for Lyα and ∼3 per cent at NIR wavelengths in the case of oblate grains with an Mathis-Rumpl-Nordsieck size distribution. We find that the CP degree of Lyα is well correlated with that in the NIR regardless of viewing angle, whilst being a factor of ∼5 higher. Thus, a high CP of Lyα is expected at sites where NIR CP is detected. We suggest that such circularly polarized Lyα may initiate the enantiomeric excess of biological molecules in space.

Radiation doses and accuracy of navigated pedicle screw placement in cervical and thoracic spine surgery: a comparison of sliding gantry CT and mobile cone-beam CT in a homogeneous cohort.

Multiple solutions for navigation-guided pedicle screw placement are currently available. Intraoperative imaging techniques are invaluable for spinal surgery, but often there is little attention paid to patient radiation exposure. This study aimed to compare the applied radiation doses of sliding gantry CT (SGCT)- and mobile cone-beam CT (CBCT)-based pedicle screw placement for spinal instrumentation. The authors retrospectively analyzed 183 and 54 patients who underwent SGCT- or standard CBCT-based pedicle screw placement, respectively, for spinal instrumentation at their department between June 2019 and January 2020. SGCT uses an automated radiation dose adjustment. Baseline characteristics, including the number of screws per patient and the number of instrumented levels, did not significantly differ between the two groups. Although the accuracy of screw placement according to Gertzbein-Robbins classification did not differ between the two groups, more screws had to be revised intraoperatively in the CBCT group (SGCT 2.7% vs CBCT 6.0%, p = 0.0036). Mean (± SD) radiation doses for the first (SGCT 484.0 ± 201.1 vs CBCT 687.4 ± 188.5 mGy*cm, p < 0.0001), second (SGCT 515.8 ± 216.3 vs CBCT 658.3 ± 220.1 mGy*cm, p < 0.0001), third (SGCT 531.3 ± 237.5 vs CBCT 641.6 ± 177.3 mGy*cm, p = 0.0140), and total (SGCT 1216.9 ± 699.3 vs CBCT 2000.3 ± 921.0 mGy*cm, p < 0.0001) scans were significantly lower for SGCT. This was also true for radiation doses per scanned level (SGCT 461.9 ± 429.3 vs CBCT 1004.1 ± 905.1 mGy*cm, p < 0.0001) and radiation doses per screw (SGCT 172.6 ± 110.1 vs CBCT 349.6 ± 273.4 mGy*cm, p < 0.0001). The applied radiation doses were significantly lower using SGCT for navigated pedicle screw placement in spinal instrumentation. A modern CT scanner on a sliding gantry leads to lower radiation doses, especially through automated 3D radiation dose adjustment.

Spherical Harmonics for the 1D Radiative Transfer Equation. I. Reflected Light

A significant challenge in radiative transfer theory for atmospheres of exoplanets and brown dwarfs is the derivation of computationally efficient methods that have adequate fidelity to more precise, numerically demanding solutions. In this work, we extend the capability of the first open-source radiative transfer model for computing the reflected light of exoplanets at any phase geometry, PICASO (Planetary Intensity Code for Atmospheric Spectroscopy Observations). Until now, PICASO has implemented two-stream approaches to the solving the radiative transfer equation for reflected light, in particular following the derivations of Toon et al. In order to improve the model accuracy, we have considered higher-order approximations of the phase functions; namely, we have increased the order of approximation from two to four, using spherical harmonics. The spherical harmonics approximation decouples spatial and directional dependencies by expanding the intensity and phase function into a series of spherical harmonics, or Legendre polynomials, allowing for analytical solutions for low-order approximations to optimize computational efficiency. We rigorously derive the spherical harmonics method for reflected light and benchmark the four-term method (SH4) against Toon et al. and two independent and higher-fidelity methods (CDISORT and doubling method). On average, the SH4 method provides an order-of-magnitude increase in accuracy, compared to Toon et al. Finally, we implement SH4 within PICASO and observe only a modest increase in computational time, compared to two-stream methods (20% increase).

Simulations on the effects of an optimized bowtie dipole antenna with an adaptive FIR filter

In the evolution of technology through the years, antennas are use in varying wireless systems have been in demand. Antennas play a great role in transmitting and receiving signals. As its application is heavily used in many days to day activities, it is important to create a cost-efficient and quick way to analyze its performance, characteristics, and relationship to different variables. As many radiation pattern acquisition devices are expensive, this simulation proposes a quick, reliable, and cost-friendly way to simulate 2D patterns in the E-plane and H-plane of a bowtie dipole antenna with an adaptive finite impulse response (FIR) filter. Through this study, the software MATLAB will be utilized to successfully simulate the radiation patterns of antennas with varying lengths. With the use of MATLAB toolboxes, the researchers aim to be able to compare different antenna lengths and determine the relationship and effect of it in the obtained 2D radiation pattern. If this method is successful various antenna applications may be implemented in the future with the use of 2D radiation pattern results.

Student perceptions of the use of three-dimensional (3-D) virtual reality (VR) simulation in the delivery of radiation protection training for radiography and medical students

BackgroundVR simulation-based learning is increasingly used in healthcare education to prepare students for clinical practice. This study investigates healthcare students' experience of learning radiation safety in a simulated interventional radiology (IR) suite. MethodRadiography students (n = 35) and medical students (n = 100) were introduced to 3D VR radiation dosimetry software designed to improve the learners' understanding of radiation safety in IR. Radiography students underwent formal VR training and assessment, which was complemented with clinical placement. Medical students practiced similar 3D VR activities informally without assessment. An online questionnaire containing Likert questions and open-ended questions was used to gather student feedback on the perceived value of VR-based radiation safety education. Descriptive statistics and Mann–Whitney U tests were used to analyse Likert-questions. Open-ended question responses were thematically analysed. ResultsA survey response rate of 49% (n = 49) and 77% (n = 27) was obtained from radiography and medical students respectively. Most respondents (80%) enjoyed their 3D VR learning experience, favouring the in-person VR experience to online VR. 73% felt that VR learning enhanced their confidence across all relevant learning outcomes. Whilst confidence was enhanced across both cohorts, VR learning had a greater impact on confidence levels amongst medical students with respect to their understanding of radiation safety matters (U = 375.5, p < 0.01). 3D VR was deemed a valuable assessment tool. ConclusionRadiation dosimetry simulation-based learning in the 3D VR IR suite is perceived to be a valuable pedagogical tool by radiography and medical students and enhances curricula content.

Effect of moisture release on radiation behavior of burning coal bed between enclosed confined surfaces

In this study, a numerical analysis was performed to predict the radiation characteristics of burning coal layers heated on confined surfaces in an enclosed chamber. The one-dimensional (1D) unsteady energy balance equation and radiative transfer equation (RTE) were solved simultaneously using the semi-implicit Runge–Kutta method (SIRK) and discrete ordinate method (DOM). In addition to the 1D analysis, a commercial software was used to analyze the two-dimensional (2D) radiation behavior of the burning coal layers using the DOM.The heat generation rate (relevant to the combustion rate) and particle absorption coefficient were independently determined using combustion and thermal emission experiments. The gas absorption coefficient was calculated from gray gas models to account for the change of H2O vapor along coal and gas mixture with high moisture content. The dimensionless radiative heat flux and temperature distribution were determined for the three calculation cases. Two different predictions based on 1D and 2D geometries were validated against measured heat flux and temperature data. The effect of the moisture release inside the particle layer was particularly examined. The result indicates that the condensation of H2O is probably more responsible than the absorption of H2O vapor for a reduced heat flux observed in the combustion condition of high moisture coal burning at high pressure.