Radiation Beam Research Articles

Feasibility of Flash Radiation Therapy Using X-ray Sources Based on Simulation Method

Background: The main challenge in radiation therapy (RT) has been the destruction of tumor or cancerous tissue while causing the least damage to healthy and normal tissues around the tumor. This is despite the fact that the maximum tolerated dose for normal tissue is limited, and this factor limits tumor destruction with radiation, thus lowering the efficiency of RT. The flash effect was initially proposed as a solution for the movement of the organ under treatment, such as the lung, demonstrating that tissue displacement occurs with breathing. Methods: In this study, the feasibility of achieving the flash effect, in the direction of the beam and perpendicular to the direction of the radiation beam was investigated using X-rays with energies in keV. Results: The results of this study, which is the only examination of the effect of distance on radiation, revealed that the amount of energy received in the target increased with the shortening of the distance, and on the other hand, in the direction perpendicular to the radiation, the extent and dispersion of the beam were reduced with the shortening of the distance between the source and the surface of the phantom. Conclusion: This issue can justify in flash effect, the beam will be more concentrated and theside tissues will be less affected by the radiation compared to conventional radiation therapy

Special MCP-N thermoluminescent detectors (TLD) with better angular dependence

One of the basic parameters in the use of thermoluminescent detectors is the angular characteristics, i.e. receiving different signals depending on the angle of radiation exposure. The TLD detector is typically installed in a slide/badge and here the angular characteristics may have an influence, adding non-uniform coverage of the detectors with filters for the correct determination of the dose as a function of energy, because the energy characteristics are usually not flat.As part of the work, special MCP-N (LiF:Mg, Cu, P) detectors of various shapes were prepared to improve the angular characteristics. The detectors were round pellets with the same circular shape with a diameter of 4.5 mm, and a modified form inside (large and small drilled holes) or a modified surface (cavity or hemisphere). For comparison, standard MCP-N type detectors were used. Detectors in special boxes were exposed to X-rays with an energy of 80 keV. The radiation beam was formed by a medical X-ray apparatus adapted for experiments at the Warsaw University of Technology in Warsaw. Exposures were made for angles of 0, 30, 45, 50, and 90° for a dose of 1.5 mGy.Results show that it is possible to improve the angular characteristics for detectors with modified shapes. Better angular characteristics will allow for more accurate measurements, in particular in comparison tests, for accreditation and other calibrations. Especially improved angular dependence detectors could be useful for H*(10) environmental measurements.

Collection efficiencies of cylindrical and plane parallel ionization chambers: analytical and numerical results and implications for experimentally determined correction factors

Objectives. To derive a collection efficiency formula, fGauss , for cylindrical ionization chambers in pulsed radiation beams from a volume recombination model of Boag et al (1996 Phys. Med. Biol. 41 885–97) including free electrons. To validate fGauss and a parallel plate chamber formula fexp using an ion transport code and calculate changes in collection efficiencies caused by electric field charge screening at 0.1–100 mGy doses-per-pulse. And to determine collection efficiencies CE∞ predicted at infinite voltage in the absence of avalanche effects by fitting scaled formulae to efficiencies computed for 100–400 V chamber voltages and 10 and 100 mGy doses-per-pulse. Approach. Calculations were performed for an idealized parallel plate chamber with 2 mm electrode separation d , and for an idealized cylindrical chamber with 0.5 and 2.333 mm inner and electrode radii rin and rout . Main results. fGauss and fexp predict the same collection efficiencies for cylindrical and parallel plate chambers satisfying d2=(rout2−rin2)ln(rout/rin)/2 , an equivalence condition met by the chambers studied. Without charge screening, efficiencies computed using the code equalled fGauss and fexp . With screening, efficiencies changed by ⩽0.03%, ⩽1.1% and ⩽21.3% at 1, 10 and 100 mGy doses-per-pulse, and differed between the chambers by ⩽0.9% and ⩽19.6% at ⩽10 and 100 mGy dose-per-pulse. For fits of fexp and fGauss , CE∞ values were ⩽1.2% and ⩽17.6% from unity at 10 and 100 mGy per pulse respectively, closer than for other formulae tested. Significance. Allowing for screening, fGauss and fexp described computed collection efficiencies to within 0.03%, 1.1% and 21.3% at doses-per-pulse ⩽1, 10 and 100 mGy. Equivalence of the two chambers broke down at 100 mGy per pulse. Departures of CE∞ values from unity suggest that collection efficiencies determined experimentally by fitting fGauss or fexp to readings made at multiple voltages will be accurate to within 1.2% and 17.6% at 10 and 100 mGy per pulse respectively.

Knowledge and Utilization of Sex-Specific Lead Aprons Among Pediatric Orthopaedic Surgeons.

Orthopaedic surgeons routinely face exposure to ionizing radiation during intraoperative use of fluoroscopy. Lead personal protective equipment reduces occupational radiation exposure. Female-specific lead aprons are designed with expanded lateral coverage to improve protection of breast tissue against radiation beams. The purpose of this study was to identify current trends in knowledge and utilization of female-specific lead aprons as well as any barriers to utilization. An anonymous electronic survey including 20 multiple choice and multiple selection responses was distributed to all members of the Pediatric Orthopaedic Society of North America (POSNA). Respondents who reported the use of intraoperative fluoroscopy in their practice were included in the study. Most respondents were attending surgeons (91%) and practiced in an academic setting (85%) in an urban environment (75%). Most respondents reported using a lead apron for every case (76%) and a thyroid shield for every case (75%), while most respondents reported they do not wear lead glasses (73%). Fifty-one percent of respondents were aware of female-specific lead aprons. The majority of respondents reported female-specific lead is unavailable (45%) or available in insufficient quantities (5.5%) at their institution. Ninety percent of females reported they do not wear female-specific lead with the common reasons being lack of availability and discomfort. Knowledge of female-specific lead is low with lack of availability as a common barrier to utilization. As female presence in the field of orthopaedic surgery expands, efforts should be made to improve education and availability of sex-specific lead aprons.

Estimation of doses absorbed by the thyroid and salivary glands, eyes, and brains of pediatric dental patients

In addition to the quality of the image, radiological protection of the patient must be considered to ensure an adequate diagnosis in dental radiology, especially in regard to those parts of the patient's body that are close to the radiation beam, such as the thyroid, salivary glands, and brain. In this work, the doses absorbed by the thyroid, salivary glands, eyes and brain of pediatric dental patients undergoing radiographic examinations are estimated using MCNP 6.2 coupled with virtual anthropomorphic phantoms, based on information from dental scenarios with a periapical X-ray unit. The absorbed doses were estimated for five- and 10-year-old male and female children. In the occlusal position, a higher absorbed dose to the thyroid was found for a five-year-old patient, whereas in the molar tube position, the brain was found to receive a higher absorbed dose for five- and 10-year-old patients. The results obtained here, expressed in terms of the absorbed dose, indicate that the beam direction and the use of different image acquisition techniques strongly influence the entrance dose values for the organs of interest in this study.

Numerical study of anisotropic scattering and solar radiation impact on liquid droplet radiator performance

The Liquid Droplet Radiator (LDR), a lightweight frameless radiant heat rejection system, is widely regarded as the optimal heat rejection solution for megawatt-scale space nuclear power systems. The LDR dissipates heat to space through its droplet layer, which plays a crucial role in determining its radiative rejection capacity. Radiation beams undergo a series of emission, scattering, and absorption processes within the layer before being emitted into space. Prior studies typically assume isotropic scattering in this process. However, this study develops a three-dimensional model for the LDR’s droplet layer based on Mie theory and Monte-Carlo methods to investigate the impact of anisotropic scattering and solar radiation. Our calculations reveal that the working fluid exhibits strong forward anisotropic scattering characteristics. Under the anisotropic assumption, the heat rejection capability of the LDR is 27–33 % higher compared to the isotropic assumption. Regarding the temperature distribution within the LDR, under the anisotropic assumption, the layer’s temperature is 6 K lower at the XY boundary surface and 3 K higher at the layer median, as opposed to the isotropic assumption. We introduce the concept of the probability of a light beam escape to elucidate the distinct beam transmission mechanisms and temperature distribution. When the distance between the LDR and the sun is in the vicinity of 1 AU, the impact of solar radiation on the LDR’s ability to operate is on the scale of 1E-5, which is almost negligible. This study lays down a theoretical groundwork for calculating the heat rejection capacity during the LDR design phase.

Design, construction, and dosimetry of 3D printed heterogeneous phantoms for synchrotron brain cancer radiation therapy quality assurance

Objective. This study aims to design, manufacture, and test 3D printed quality assurance (QA) dosimetry phantoms for synchrotron brain cancer radiation therapy at the Australian synchrotron. Approach. Fabricated 3D printed phantoms from simple slab phantoms, a preclinical rat phantom, and an anthropomorphic head phantom were fabricated and characterized. Attenuation measurements of various polymers, ceramics and metals were acquired using synchrotron monochromatic micro-computed tomography (CT) imaging. Polylactic acid plus, VeroClear, Durable resin, and tricalcium phosphate were used in constructing the phantoms. Furthermore, 3D printed bone equivalent materials were compared relative to ICRU bone and hemihydrate plaster. Homogeneous and heterogeneous rat phantoms were designed and fabricated using tissue-equivalent materials. Geometric accuracy, CT imaging, and consistency were considered. Moreover, synchrotron broad-beam x-rays were delivered using a 3 Tesla superconducting multipole wiggler field for four sets of synchrotron radiation beam qualities. Dose measurements were acquired using a PinPoint ionization chamber and compared relative to a water phantom and a RMI457 Solid Water phantom. Experimental depth doses were compared relative to calculated doses using a Geant4 Monte Carlo simulation. Main results. Polylactic acid (PLA+) shows to have a good match with the attenuation coefficient of ICRU water, while both tricalcium phosphate and hydroxyapatite have good attenuation similarity with ICRU bone cortical. PLA+ material can be used as substitute to RMI457 slabs for reference dosimetry with a maximum difference of 1.84%. Percent depth dose measurement also shows that PLA+ has the best match with water and RMI457 within ±2.2% and ±1.6%, respectively. Overall, PLA+ phantoms match with RMI457 phantoms within ±3%. Significance and conclusion. The fabricated phantoms are excellent tissue equivalent equipment for synchrotron radiation dosimetry QA measurement. Both the rat and the anthropomorphic head phantoms are useful in synchrotron brain cancer radiotherapy dosimetry, experiments, and future clinical translation of synchrotron radiotherapy and imaging.

Additive antitumor effect of arsenic trioxide with exposure to ionizing radiation to human acute promyelocytic leukemia HL‑60 cells.

Arsenic trioxide (ATO) is expected to be a chemical drug with antitumor activity against acute promyelocytic leukemia (APL), a type of acute myeloid leukemia. In Japan, its antitumor effects were confirmed in clinical trials for APL, and it has been approved in various countries around the world. However, there have been no reports on ATO's antitumor effects on radioresistant leukemia cells, which can be developed during radiotherapy and in combination with therapeutic radiation beams. The present study sought to clarify the antitumor effect of ATO on APL cells with radiation resistance and determine its efficacy when combined with ionizing radiation (IR). The radiation‑resistant HL60 (Res‑HL60) cell line was generated by subjecting the native cells to 4‑Gy irradiation every week for 4 weeks. The half‑maximal inhibitory concentration (IC50) for cell proliferation by ATO on native cell was 0.87 µM (R2=0.67), while the IC50 for cell proliferation by ATO on Res‑HL60 was 2.24 µM (R2=0.91). IR exposure increased the sub‑G1 and G2/M phase ratios in both cell lines. The addition of ATO resulted in a higher population of G2/M after 24 h rather than 48 h. When the rate of change in the sub‑G1 phase was examined in greater detail, the sub‑G1 phase in both control cells without ATO significantly increased by exposure to IR at 24 h, but only under the condition of 2 Gy irradiation, it had continued to increase at 48 h. Res‑HL60 supplemented with ATO showed a higher rate of sub‑G1 change at 24 h; however, 2 Gy irradiation resulted in a decrease compared with the control. There was a significant increase in the ratio of the G2/M phase in cells after incubation with ATO for 24 h, and exposure to 2 Gy irradiation caused an even greater increase. To determine whether the inhibition of cell proliferation and cell cycle disruptions is related to reactive oxygen species (ROS) activity, intracellular ROS levels were measured with a flow cytometric assay. Although the ROS levels of Res‑HL60 were higher than those of native cells in the absence of irradiation, they did not change after 0.5 or 2 Gy irradiation. Furthermore, adding ATO to Res‑HL60 reduced intracellular ROS levels. These findings provide important information that radioresistant leukemia cells respond differently to the antitumor effect of ATO and the combined effect of IR.

Design of a low-profile bi-directional radiated Fabry-Perot cavity antenna with independent forward and backward radiation based on metasurface technique.

This paper introduces a novel Fabry-Perot cavity (FPC) antenna design based on metasurface technique to achieve bi-directional radiation with independent forward and backward beam control capability and a low-profile configuration. Two pieces of partially reflective metasurface (PRMS) based on receiver-transmitter architecture with independent control of transmission and reflection phases are designed to serve as the upper and lower layers of the FPC antenna, respectively. By manipulating the transmission phase distribution of the two pieces of PRMS, designable independent multi-beam bi-directional radiation patterns can be achieved. For validation, two FPC antennas based on the proposed configuration are designed with different bi-directional radiation patterns. Proved by simulated results, Antenna 1 can achieve forward dual-beam and backward single-beam radiation simultaneously with a return loss of less than -10 dB at 10.4 GHz. The two beams of forward radiation point in the -45° and 35° directions, respectively, with gains of 7.42 dBi and 7.70 dBi. The gain of the single beam of backward radiation is 10.82 dBi. Antenna 2 can achieve a four-beam radiation pattern with both forward and backward dual beams. The beam directions of the four beams are -153°, -44°, 37°, and 146°, respectively. The gains in each direction are 5.45 dBi, 6.63 dBi, 5.97 dBi, and 5.22 dBi, respectively. The overall profile is 23.72 mm (0.81 λ) for both antennas. The prototype of Antenna 1 is fabricated and measured. The results are in good agreement with the simulated counterparts, which demonstrates the feasibility of the proposed design methodology.

A Study on Radiation Level at the Treatment Plane Due to Induced Activity in Linear Accelerator Head.

The induced activity is produced in the target, monitor chamber, flattening filter (FF), collimating jaws, etc., when a high-energy photon beam is utilized for radiation therapy. This may result in add-on exposure to radiation professionals. This study aims to measure the radiation level (RL) at the treatment plane due to induced activity in the linear accelerator head. In this study, RLs were measured close to the isocenter (I), LINAC head (H), and 0.5 m lateral to the isocenter (L) inside the radiation bunker. The RLs were measured for field sizes (FS) 5 cm × 5 cm, 10 cm × 10 cm, 20 cm × 20 cm, 30 cm × 30 cm, and 40 cm × 40 cm, using 50, 100, 200, 300, 400, 500, and 1000 monitor units (MUs) at above said locations inside the bunker using 10 mega-voltage (MV), 10 MV FF free, and 15 MV radiation beam. RL increases with an increase in FS and MUs at all mentioned locations inside the bunker, except for 40 cm × 40 cm FS. The present study shows that RL increases with an increase in radiation beam energy, and there was significant RL inside the bunker at the mentioned location, even after the 1 min of high-energy radiation exposure. Therefore, treatment with a high-energy beam should be scheduled in the later evening of the working day and the jaw should be closed to a minimum before entering the bunker and a sufficient time gap should be followed to minimize the additional exposure due to induced activation in high-energy treatment.

High-accuracy beam generation and scanning using reconfigurable coding metasurface

Metasurface technology has attracted widespread attention, owing to its remarkable capability to control electromagnetic properties. In this paper, we design a reconfigurable reflective metasurface array operating at 5 GHz for beam generation and scanning based on coding metasurface. Field programmable gate array (FPGA) is equipped for switching the states of PIN (positive-intrinsic-negative) diodes loaded on the metasurface in real-time, resulting in a 180° phase difference. To obtain multi-beam radiation and high-accuracy beam steering, the coding sequence to produce the target radiation pattern is calculated by an algorithm program. We design the fitness function of a genetic algorithm (GA) to optimize the sequence corresponding to the target directions. The simulation result shows that with the accuracy of 1°, the proposed metasurface is capable of generating multi-beam and scanning two-dimensional beams within the 50° range. Further, we fabricate and measure a prototype sample of 15 × 15 elements, which is verified feasible by comparing the measured result and the simulation. This work demonstrates the great potential of applying this reflective metasurface to wireless communication or radar.

Effects of irradiation on the survival of Sarcocystis bradyzoites in beef.

Sarcocystis is a food-borne zoonotic protozoan whose final hosts are humans, dogs, cats, and other carnivores and intermediate hosts are birds and mammals, especially humans and herbivores. Humans become infected by eating raw and undercooked meat contaminated with bradyzoites or by consuming water or food contaminated with the sporocyst stage of the parasite. The aim of this study was to investigate the effects of gamma radiation and electron beam on the survival rate of Sarcocystis bradyzoites in infected beef and to determine the effective dose. Three replicates of 100g of infected meat were treated with different doses (0.5, 1, 1.5 and 2kGy). As a control, 20g of contaminated meat was stored separately at 4°C. The viability of the bradyzoites after digestion in pepsin solution was assessed, stained (trypan blue) and unstained, under a stereomicroscope. To assess survival of the bradyzoites, the irradiated meat samples were fed to 30 dogs. After 10 days, faecal samples were examined for sporocysts. The results showed that the highest and lowest mortality rate of Sarcocystis bradyzoites in infected organs using electron beam at a dose of 2kGy were 92.5% and 100%, respectively, and the lowest mortality rate at a dose of 0.5kGy were 2.5% and 7.89%, respectively. The results of statistical analysis showed that the mortality rate of Sarcocystis bradyzoites was significant between different doses of gamma ray and electron beam, so that gamma rays were better compared to electron beam in destroying Sarcocystis bradyzoites.

Exploring single-shot propagation and speckle based phase recovery techniques for object thickness estimation by using a polychromatic X-ray laboratory source.

Propagation and speckle-based techniques allow reconstruction of the phase of an X-ray beam with a simple experimental setup. Furthermore, their implementation is feasible using low-coherence laboratory X-ray sources. We investigate different approaches to include X-ray polychromaticity for sample thickness recovery using such techniques. Single-shot Paganin (PT) and Arhatari (AT) propagation-based and speckle-based (ST) techniques are considered. The radiation beam polychromaticity is addressed using three different averaging approaches. The emission-detection process is considered for modulating the X-ray beam spectrum. Reconstructed thickness of three nylon-6 fibers with diameters in the millimeter-range, placed at various object-detector distances are analyzed. In addition, the thickness of an in-house made breast phantom is recovered by using multi-material Paganin's technique (MPT) and compared with micro-CT data. The best quantitative result is obtained for the PT and ST combined with sample thickness averaging (TA) approach that involves individual thickness recovery for each X-ray spectral component and the smallest considered object-detector distance. The error in the recovered fiber diameters for both techniques is , despite the higher noise level in ST images. All cases provide estimates of fiber diameter ratios with an error of 3% with respect to the nominal diameter ratios. The breast phantom thickness difference between MPT-TA and micro-CT is about 10%. We demonstrate the single-shot PT-TA and ST-TA techniques feasibility for thickness recovery of millimeter-sized samples using polychromatic microfocus X-ray sources. The application of MPT-TA for thicker and multi-material samples is promising.

CRITERIA FOR THE OPTIMAL MODE OF NON-DESTRUCTIVE TESTING BY DIGITAL RADIOGRAPHY

Theoretically justified and experimentally confirmed criteria for the selection of modes and parameters of digital radiography control. The analysis of the digital image quality showed its dependence on the parameters and control modes, on the value of the signal-to-noise ratio. Analytical information was obtained a relationship linking the size of the defect in the plane perpendicular to the axis of the radiation beam, the size of the focal spot of the radiation source, the parameters of the control circuit and the pixel size of the detector system. The validity of the analytical expression has been confirmed experimentally.

Ultrasonic Sensor-based Water Leveling for Three-dimensional Water Phantom: Prototype Development.

The purpose of this study was to develop a prototype for controlling the water level of a three-dimensional (3D) water phantom using ultrasound sensors and Arduino technology and evaluate its performance in setting up the 3D water phantom for radiation beam measurements. A prototype consisted of an Arduino Nano board and two types of ultrasound sensors (US015 and SR04). The accuracy of both sensors was tested at various distances and the performance was evaluated through statistical analysis. The distance measurement test was performed rigorously at intervals of 2 cm from 5 cm to 21 cm, measuring an average error and a maximum deviation for each sensor. Both sensors demonstrated the measurement accuracy within 2 mm. When using the traditional and prototype-based setup methods, the measured photon and electron beam profiles did not show any significant difference. This result suggests the equivalent setup capability when using these two different 3D water phantom setup methods. The ultrasound sensor-based prototype is demonstrated as a more effective device in maintaining the 3D water phantom setup consistently compared to the traditional method, which is prone to human error, and it will aid in facilitating precise phantom setup during the commissioning and routine quality assurance (QA) of linear accelerators in radiotherapy clinics.

Cubical radiator for three‐dimensional flexible beam controller with multiple radiation beams and directions

AbstractA novel approach for generation of the multiple three‐directional and controllable beams from a cubical electromagnetic (EM) wave radiator is proposed in this paper. This cubical radiator is a multiple‐mode EM resonator, which is formed by a cubical metal cavity. Three resonant modes are excited in this cavity resonator by a feeding slot. Besides the feeding slot, a few additional slots are opened on the side wall(s) of the cavity to act as the EM wave radiation elements. Various combinations of radiation slots contribute to different beam directions, for example, side‐direction (single radiation slot), edge‐direction (two radiation slots), and vertex‐direction of the cavity (three radiation slots). More combinations of these slots are further studied in the cases of side + edge and edge + vertex to illustrate the diversity in the directions of the produced EM beams. To validate the predicted results, two prototypes are fabricated and measured to display their far‐field radiation patterns. The measured results agree well with the full‐wave simulated ones, thereby demonstrating the possibility of a large number of the flexible EM beams, as well as the capability of the controllable beam directions.

A Novel Flying Robot Swarm Formation Technique Based on Adaptive Wireless Communication using MUSIC Algorithm

This paper presents a novel technique to address the challenge of coordinating swarm flying robots in a leader-follower configuration. A combination of the Multi Signal Classification (MUSIC) estimation algorithm, based on a wireless MIMO array antenna, along with onboard robot control are used for precise route tracking of an individual robot. Employing an array antenna reduces energy consumption for followers in passive mode and reduces computational complexity when measuring the angles of leader angle interferences, which depends on the phase difference of the impinging signal on the antenna elements of the array. Additionally, the angles estimation and beamforming processes, utilizing MUSIC algorithm, form an inner loop that furnishes orientation angles in 3D (Azimuth and elevation angles) for both the leader and potential interference sources. The outer loop, contingent on the onboard controller and the robot's GPS system, enabling fine adjustments in angle and position relative to the leader's location. The simulation results illustrated the efficiency of the proposed technique in estimating the orientation angles of the leader and the interference sources. The technique robustness is confirmed through testing the performance on different trajectories. Where the follower perfectly generates a main radiation beam directed towards the leader, effectively mitigates interference signals from neighboring group leaders, and successfully tracks the leader path.

Assessment of peripheral dose as a function of distance and depth from cobalt-60 beam in water phantom using TLD-100

BackgroundInnovations in cancer treatment have contributed to the improved survival rate of cancer patients. The cancer survival rates have been growing and nearly two third of those survivors have been exposed to clinical radiation during their treatment. The study of long-term radiation effects, especially secondary cancer induction, has become increasingly important. An accurate assessment of out-of-field/peripheral dose (PDs) is necessary to estimate the risk of second cancer after radiotherapy and the damage to the organs at risk surrounding the planning target volume. This study was designed to measure the PDs as a function of dose, distances, and depths from Telecobalt-60 (Co-60) beam in water phantom using thermoluminescent dosimeter-100 (TLD-100).MethodsThe PDs were measured for Co-60 beam at specified depths of 0 cm (surface), 5 cm, 10 cm, and 15 cm outside the radiation beam at distances of 5, 10, and 13 cm away from the radiation field edge using TLD-100 (G1 cards) as detectors. These calibrated cards were placed on the acrylic disc in circular tracks. The radiation dose of 2000 mGy of Co-60 beam was applied inside 10 × 10 cm2 field size at constant source to surface distance (SSD) of 80 cm.ResultsThe results showed maximum and minimum PDs at surface and 5 cm depth respectively at all distances from the radiation field edge. Dose distributions out of the field edge with respect to distance were isotropic. The decrease in PDs at 5 cm depth was due to dominant forward scattering of Co-60 gamma rays. The increase in PDs beyond 5 cm depth was due to increase in the irradiated volume, increase in penumbra, increase in source to axis distance (SAD), and increase in field size due to inverse square factor.ConclusionIt is concluded that the PDs depends upon depth and distance from the radiation field edge. All the measurements show PDs in the homogenous medium (water); therefore, it estimates absorbed dose to the organ at risk (OAR) adjacent to cancer tissues/planning target volume (PTV). It is suggested that PDs can be minimized by using the SAD technique, as this technique controls sources of scattered radiation like inverse square factor and effect of penumbra up-to some extent.

Modeling the beam of gravitational radiation from a cosmic string loop

Modeling the beam of gravitational radiation from a cosmic string loop

High-Capacity Multiple-Input Multiple-Output Communication for Internet-of-Things Applications Using 3D Steering Nolen Beamforming Array

In this paper, a novel 2D Nolen beamforming phased array with 3D scanning capability to achieve high channel capacity is presented for multiple-input multiple-output (MIMO) Internet-of-Things (IoT) applications. The proposed 2D beamforming phased array is designed by stacking a fundamental building block consisting of a 3 × 3 tunable Nolen matrix, which applies a small number of phase shifters with a small tunning range and reduces the complexity of the beam-steering control mechanism. Each 3 × 3 tunable Nolen matrix can achieve a full 360° range of progressive phase delay by exciting all three input ports, and nine individual radiation beams can be generated and continuously steered on azimuth and elevation planes by stacking up three tunable Nolen matrix in horizontal and three in vertical to maximize signal-to-noise ratio (SNR) in the corresponding spatial directions. To validate the proposed design, the simulations have been conducted on the circuit network and assessed in a fading channel environment. The simulation results agree well with the theoretical analysis, which demonstrates the capability of the proposed 2D Nolen beamforming phased array to realize high channel capacity in MIMO-enabled IoT communications.