Beam Orientation Research Articles

Uncertainty contribution of the laser-beam orientation for laser Doppler vibrometer measurements at the carotid artery

Displacement signals acquired at the carotid artery with laser Doppler vibrometry (LDV) present a characteristic waveform that is correlated to the blood pressure inside the vessel. There are different models in literature that relate the displacement amplitude to the pressure. Therefore, a wrong estimation of the displacement amplitude would lead to errors on the extraction of the pressure information. LDV measures the vibration component in the direction of the laser beam. If the laser beam is not parallel to the vibration direction of the target, only a projection of the real vibration amplitude is measured. With a 3D-LDV measurement it is possible to measure the real amplitude of the displacement. For 1D-LDV measurements it is necessary to calculate the contribution of the uncertainty of the laser beam orientation to the displacement. In this paper, we investigate the uncertainty contribution due to the laser beam direction on the displacement amplitude of vibration signals acquired at the carotid artery. We used a multipoint vibrometer for the investigation. Our aim is to quantify this uncertainty for 1D-LDV measurements at the carotid artery. Moreover, we quantify its influence on the detection of the pressure. We derive an uncertainty contribution due to the laser beam direction of 13% for the displacement amplitude.

Spectroscopy of fractional orbital angular momentum states.

We present an approach for measuring the orbital angular momentum (OAM) of light tailored towards applications in spectroscopy and non-integer OAM values. It is based on the OAM sorting method (Berkhout et al., Phys. Rev. Lett. 105, 153601 (2010)). We demonstrate that mixed OAM states and fractional OAM states can be identified using moments of the sorted output intensity distribution and OAM states with integer and non-integer topological charge can be clearly distinguished. Furthermore the difference between intrinsic OAM and total OAM for fractional OAM states is highlighted and the importance of the orientation of the fractional OAM beam is shown. All experimental results show good agreement with simulations. Finally we discuss possible applications of this method for spectroscopy of semiconductor systems such as exciton-polaritons in microcavities.

Tailoring polarization states of multiple beams that carry different topological charges of orbital angular momentums.

In the past few years, orbital angular momentum (OAM) has aroused great interest in the scientific communities, because it shows great potential for enhancing capacities of radio and optical communication systems. Here, we propose anisotropic metasurfaces to generate multiple OAM vortex beams at microwave frequencies. A phase compensation theory is presented, in order to determine the phase distributions on metasurfaces, This theory enables independent control of beam numbers, polarizations, orientations, and topological charges of OAM vortex beams, respectively. The metasurface is composed of anisotropic elements, whose reflection phases can be engineered separately in different polarization directions. The scheme is validated by both simulation and experimental results and shows great potential for the polarization division multiplexing in OAM communication systems.

4πVMAT: A Novel Method to Efficiently Deliver Non-Coplanar Treatment

Existing Volumetric Modulated Arc Therapy (VMAT) optimization using one or more arcs, each being coplanar by itself, is a highly efficient way to deliver intensity modulated radiation therapy (IMRT). Static beam IMRT utilizing optimized non-coplanar beam orientation has resulted in superior dosimetry to VMAT but is substantially less efficient. In this study, we developed a novel optimization framework for non-coplanar VMAT, incorporating simultaneous couch and gantry rotation during the arc motion, to maximally utilize the 4π solid angle (4πVMAT) with high efficiency. The 4πVMAT optimization framework includes a Direct Aperture Optimization (DAO) module and a beam trajectory selection (BTS) module. DAO was achieved by adding to the dose fidelity objective a total variation term for regulating the fluence smoothness, a single segment term for forming deliverable fluence map, and a group sparsity term for selecting beam angles. The BTS was formulated as a travelling salesman problem on a hierarchical graph, where the edge and node costs were determined by the maximal gantry rotation speed and the estimated fluence map at the current iteration, respectively. Continuous gantry/couch angle trajectories were selected on the graph using the Dijkstra's algorithm. Candidate beams in the couch-gantry-patient collision space, evaluated on actual machine geometry and a human subject 3D surface, were excluded in both the DAO and BTS modules. The optimization framework was solved by alternating between the DAO module and the BTS. Efficacy of 4πVMAT using one full-arc or two full arcs was tested on a brain, a lung and a prostate cancer patient. The plan was compared against a coplanar VMAT (2πVMAT) plan using more arcs with collimator rotation. The 4πVMAT consisted of two efficient arcs, each taking 160 seconds in estimate to deliver. In the first arc, the couch rotated in either the clockwise or counterclockwise direction, and then reversed the rotation in the second arc. The gantry rotations were coordinated with the couch rotation for optimal dose distribution while avoiding couch-gantry-patient collision. With the same target coverage, 4πVMAT remarkably reduced the max and mean organs-at-risk (OARs) doses compared to 2πVMAT, as shown in Table 1. The dose compactness measured using R50 was reduced by 19.7%. By optimizing feasible and efficient non-coplanar arc trajectories, the novel 4πVMAT optimization framework simultaneously achieves the desirable dosimetric quality of 4π therapy and the delivery efficiency of coplanar 2πVMAT.Abstract TU_35_3241: Table 1OAR dose: 2πVMAT - 4πVMAT (% of the prescription dose)patientDmaxDmeanLargestAverageLargestAveragebrain12.847.529.324.68lung32.6012.7810.583.62prostate10.502.764.300.35OAR mean and maximum dose differences between πVMAT and 2πVMAT for all patients. “Largest” and “Average” represent the largest and average values among all OARs. Open table in a new tab

Laser microtextured titanium implant surfaces reduce in vitro and in situ oral biofilm formation.

IntroductionMicro- or nano-topography can both provide antimicrobial properties and improve osseointegration of dental implant titanium surfaces. Laser treatment is one of the best surface microtexturing techniques. The aim of this study was to evaluate in vitro and in situ biofilm formation on a laser-treated titanium surface, comparing it with two conventional surfaces, machined and grit-blasted.MethodsFor the in vitro experiment, an oral microcosm biofilm model was developed on the surface of titanium disks and reference human enamel using a bioreactor for 48 h. For the in situ experiment, titanium implants with laser-treated, machined and grit-blasted surfaces were mounted on intraoral trays and worn by ten volunteers for 48 h. Biofilm formation was quantitatively evaluated, and surfaces were analyzed using confocal laser scanning microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy.Results–in vitro studyBiofilm structures with a prevalence of viable cells covered most of the machined, grit-blasted and human enamel surfaces, whereas less dense biofilm structures with non-confluent microcolonies were observed on the laser-treated titanium. Laser-treated titanium showed the lowest biofilm formation, where microorganisms colonized the edges of the laser-created pits, with very few or no biofilm formation observed inside the pits.Results–in situ studyThe biofilm formation pattern observed was similar to that in the in vitro experiment. Confocal laser scanning microscopy showed complete coverage of the implant threads, with mostly viable cells in grit-blasted and machined specimens. Unexpectedly, laser-treated specimens showed few dead microbial cells colonizing the bottom of the threads, while an intense colonization was found on the threading sides.ConclusionThis data suggests that laser-created microtopography can reduce biofilm formation, with a maximum effect when the surface is blasted orthogonally by the laser beam. In this sense the orientation of the laser beam seems to be relevant for the biological interaction with biofilms.

Flexural behavior of composite sandwich beams with different kinds of GFRP ribs in flatwise and edgewise positions

This paper investigated the flexural behavior of composite sandwich beams, composed of glass fiber reinforced polymer (GFRP) skins and a polyurethane (PU) foam core with different kinds of GFRP ribs reinforcement, in flatwise and edgewise positions. The GFRP ribs, consisted of longitudinal, transverse and horizontal ribs, respectively, were embedded inside of the PU foam core. Twenty specimens were tested under four-point bending to verify the influence of the GFRP ribs and beam orientation on the bending stiffness, ultimate load bearing capacity, and failure modes of sandwich beams. It was found that changing the beam orientation from flatwise to edgewise change the beam failure mode from foam core shear failure to skin compressive failure. The sandwich beam's high stiffness and ultimate load bearing capacity can be efficiently utilized by placing them in edgewise position, and the longitudinal ribs played a major role on the bending stiffness and ultimate load bearing capacity compared with the transverse and horizontal ribs in flatwise position. Furthermore, an analytical model accounting for shear and flexural rigidities was proposed to predict the deflection and ultimate load bearing capacity of composite sandwich beams with different kinds of GFRP ribs in flatwise and edgewise positions. The analytical results were agreed well with test results.

Intraoperative Evaluation of the Anatomic Lateral Distal Femoral Angle and Its Variation due to Positioning.

Preoperative evaluation of the contralateral anatomic lateral distal femoral angle (aLDFA) at our institution is used to judge coronal plane alignment. In our study, we investigated 4 different techniques for obtaining an anteroposterior intraoperative fluoroscopic image of the distal femur to determine which technique provides (1) the greatest interobserver reliability; (2) the lowest variability from the previously published population mean; and (3) the lowest side-to-side variability. Inclusion criteria included lower extremity injuries needing fixation that required intraoperative fluoroscopy with an intact femur and an intact extensor mechanism (N = 100). Fluoroscopic images were obtained of the distal femur in 4 positions differentiated by the position of the limb and the orientation of the C-arm beam to the femoral shaft. All measurement techniques resulted in mean measurements within one degree of 81 degrees. Variance between measurements was small among patients with all views, but images that involved a true anteroposterior with the beam perpendicular to the femur had the lowest rate of measurements that were <78 or >84 degrees. Side-to-side differences in patients were <2 degrees on average with every image used. With the best-performing images, 20% of patients had an aLDFA > 3 degrees different from the population mean of 81 degrees and 3% of patients were >5 degrees different. Although restoring aLDFA to 81 degrees will be within 3 degrees of the contralateral side the vast majority of the time, matching the aLDFA to the injured side will be the most accurate reconstruction.

Distal Tibial Intramedullary Nailing Using an Extraarticular, Lateral Parapatellar Approach in the Semiextended Position

Semiextended positioning can improve the surgeon's ability to obtain, maintain, and fluoroscopically evaluate a fracture reduction when performing fixation with an intramedullary nail, especially in fractures at the proximal and distal ends. Furthermore, this position allows for evaluation of instrument placement, including the start point, without moving the fluoroscopic unit into extremes of angulation or compromising the quality of the beam orientation. The intraarticular suprapatellar approach has been described as a soft tissue approach to maintain the leg in a position that would not complicate management of these fractures, especially those in the proximal third of the tibia. A semiextended extraarticular soft tissue approach to the start point was described by Kubiak et al, and the lateral parapatellar version has become commonly used on the Orthopaedic Trauma Service at Washington University in Saint Louis. This video demonstrates advantages of semiextended positioning while performing reduction and intramedullary nail fixation for distal tibia fractures. This lateral parapatellar approach can be performed without specialized instrumentation, results in precise establishment of the start point and completion of the fixation without injury to the knee.

Experimental demonstration of metamaterial-assisted antenna beam deflection through folded transformation optics

Based on the folded transformation optics, a methodical approach for manipulating the orientation and directivity of a planar antenna beam is propounded. Unlike the classical phased array antennas, the tilted emitting beam is achieved by a homogeneous metamaterial-based superstrate in a triangle shape configuration, rather than by utilizing complicated and bulky phase shifters. Such a simple coating layer is elaborately designed via folding the virtual space to physical one with an affine transformation. The competency of the proposed method is demonstrated through some examples, indicating the capability of the coating layer in tilting the radiated beam to any desired off-normal directions in both the upper and lower half spaces. To authenticate the concept, a tilted beam metamaterial-based antenna is fabricated and tested; it is observed that the experimental results are in a good agreement with the numerical simulations and theoretical predictions. The presented method paves the way towards steering the beam of a metamaterial-assisted antenna, which has been a topic of great interest in several fields of engineering, such as antenna technologies, satellite communication, and multiple-input multiple-output systems.

First Tarsometatarsal Joint Shape and Orientation

Category: Bunion Introduction/Purpose: Studies have demonstrated that patients with hallux valgus (HV) deformities have increased mobility in the first tarsometatarsal (TMT) joint. Anatomical factors widely considered to play a role in the instability are shape and frontal plane orientation of the joint. An oblique rather than horizontal orientation of the articular surfaces and a round shape, rather than a flat shape, are believed to predispose to the deformity. The purpose of this study was to assess whether the shape and angulation of the first TMT joint are affected by the positioning of the foot and orientation of the x-ray beam. Methods: Ten adult above knee fresh frozen cadaveric specimens were used, with a mean age of 79.9 (range, 54-88) years. There were no clinical forefoot deformities noted in any of the feet. One of the specimens had moderate ankle arthritis and one had a mild cavus-varus. A radiolucent loading apparatus was built that, allowing neutral positioning of a plantigrade foot and controlled angulation of 5o, 10 o, 15o and 20o in dorsiflexion, plantarflexion, inversion and eversion. Fluoroscopic images were obtained of each cadaveric specimen in all seventeen different positions, with the x-ray beam perpendicular to the floor and aiming to the base of the 1st metatarsal. Two blinded orthopaedic surgeons independently measured the 1st tarsometatarsal (TMT) joint angle and graded the distal articular cartilage of the medial cuneiform as flat or curved. Readers also graded the image quality into assessing the joint into “Low”, “Intermediate” and “Good”. Results: 1st TMT joint angle was 112.92o ± 6.89o. Values were significantly different between cadaveric specimens (p&lt;.0001). There was a tendency for increased valgus angulation of the joint in images positioned in neutral, plantarflexion and inversion and decreased valgus angulation with dorsiflexion and eversion.Regarding the shape of the distal articular cartilage of the medial cuneiform, joints with flat configuration showed significantly increased mean 1st TMT joint angle when compared to curved surfaces (115.9o vs. 110.7o, p&lt;.0001). In 8 out of 10 of the cadaveric specimens (80%) the shape of the 1st TMT joint changed between curved or flat configuration depending on the positioning of the foot. In only 2/10 (20%) the joint configuration remained the same for all different positions (one flat and one curved). Conclusion: Our cadaveric study found that the shape and angulation of the first TMT joint is affected by the positioning of the foot and orientation of the x-ray beam. Clinical usefulness of the 1st TMT radiographic anatomical characteristics is limited and should not influence in the treatment of patients with possible instability the first tarsometatarsal (TMT) joint.

A method for compensating platform attitude fluctuation for helicopter-borne LiDAR: Performance and effectiveness

Attitude fluctuation of helicopter-borne platform is an important factor influencing the quality of point cloud products from airborne LiDAR, especially the roll and pitch parts. Therefore, we proposed a method to compensate the attitude fluctuation for helicopter-borne laser scanning; an attitude compensation prototype was designed, to eliminate the impact of both the roll and pitch fluctuations on point cloud products. The mechanical structure and control system of the prototype were designed. In order to test the dynamic compensation effectiveness of the prototype for airborne LiDAR, we established a semi-physical simulation system. In the experiment setup, the prototype, a laser rangefinder as well as a position and orientation system (POS) were all mounted on the platform of a three-axis turntable. The inner and middle shafts of the three-axis turntable rotated with sinusoidal movements to simulate the roll and pitch fluctuations of helicopter-borne platform. The x-axis and y-axis frameworks of the prototype were controlled to rotate inversely halves of the measured rotation angles of the simulated attitude fluctuations by the POS. Hence, the emitting orientations of the pulsed laser beams reflected by the scanning mirror embedded in the prototype would not be affected by the dynamic changing of the roll and pitch fluctuations. Total 11 groups of experiments were carried out to verify the control performance and dynamic compensation effectiveness of the compensation prototype under 11 sets of sinusoidal attitude fluctuations with different frequencies and amplitudes. Experimental results show that, under the impact of different frequencies and amplitudes sinusoidal attitude fluctuations, the attitude compensation prototype can always significantly decrease the unfavorable influence of the attitude fluctuations and have good dynamic compensation effectiveness.

Integrated beam orientation and scanning-spot optimization in intensity-modulated proton therapy for brain and unilateral head and neck tumors.

Intensity-Modulated Proton Therapy (IMPT) is the state-of-the-art method of delivering proton radiotherapy. Previous research has been mainly focused on optimization of scanning spots with manually selected beam angles. Due to the computational complexity, the potential benefit of simultaneously optimizing beam orientations and spot pattern could not be realized. In this study, we developed a novel integrated beam orientation optimization (BOO) and scanning-spot optimization algorithm for intensity-modulated proton therapy (IMPT). A brain chordoma and three unilateral head-and-neck patients with a maximal target size of 112.49cm3 were included in this study. A total number of 1162 noncoplanar candidate beams evenly distributed across 4π steradians were included in the optimization. For each candidate beam, the pencil-beam doses of all scanning spots covering the PTV and a margin were calculated. The beam angle selection and spot intensity optimization problem was formulated to include three terms: a dose fidelity term to penalize the deviation of PTV and OAR doses from ideal dose distribution; an L1-norm sparsity term to reduce the number of active spots and improve delivery efficiency; a group sparsity term to control the number of active beams between 2 and 4. For the group sparsity term, convex L2,1-norm and nonconvex L2,1/2-norm were tested. For the dose fidelity term, both quadratic function and linearized equivalent uniform dose (LEUD) cost function were implemented. The optimization problem was solved using the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA). The IMPT BOO method was tested on three head-and-neck patients and one skull base chordoma patient. The results were compared with IMPT plans created using column generation selected beams or manually selected beams. The L2,1-norm plan selected spatially aggregated beams, indicating potential degeneracy using this norm. L2,1/2-norm was able to select spatially separated beams and achieve smaller deviation from the ideal dose. In the L2,1/2-norm plans, the [mean dose, maximum dose] of OAR were reduced by an average of [2.38%, 4.24%] and[2.32%, 3.76%] of the prescription dose for the quadratic and LEUD cost function, respectively, compared with the IMPT plan using manual beam selection while maintaining the same PTV coverage. The L2,1/2 group sparsity plans were dosimetrically superior to the column generation plans as well. Besides beam orientation selection, spot sparsification was observed. Generally, with the quadratic cost function, 30%~60% spots in the selected beams remained active. With the LEUD cost function, the percentages of active spots were in the range of 35%~85%.The BOO-IMPT run time was approximately 20min. This work shows the first IMPT approach integrating noncoplanar BOO and scanning-spot optimization in a single mathematical framework. This method is computationally efficient, dosimetrically superior and produces delivery-friendly IMPT plans.

Optimization and analysis of porosity and roughness in selective laser melting 316L parts

Purpose: The investigations have been carried out on 316L stainless steel parts fabricated by Selective Laser Melting (SLM) technique. The study aimed to determine the effect of SLM parameters on porosity, hardness, and structure of 316L stainless steel. Design/methodology/approach: The analyses were conducted on 316L stainless steel parts by using AM125 SLM machine by Renishaw. The effects of the different manufacturing process parameters as power output, laser distance between the point’s melted metal powder during additive manufacturing as well as the orientation of the model relative to the laser beam and substrate on porosity, hardness, microstructure and roughness were analysed and optimised. Findings: The surface quality parts using 316L steel with the assumed parameters of the experiment depends on the process parameters used during the SLM technique as well as the orientation of formed walls of the model relative to the substrate and thus the laser beam. The lowest roughness of 316L SLM parts oriented perpendicularly to the substrate was found when 100 W and 20 μm the distance point was utilised. The lowest roughness for part oriented at 60° relatives to the substrate was observed when 125 W and the point distance 50 μm was employed. Practical implications: Stainless steel is one of the most popular materials used for selective laser sintering (SLM) processing to produce nearly fully dense components from 3D CAD models. Reduction of porosity is one of the critical research issues within the additive manufacturing technique SLM, since one of the major cost factors is the post-processing. Originality/value: This manuscript can serve as an aid in understanding the importance of technological parameters on quality and porosity of manufactured AM parts made by SLM technique.

Seismic Analysis of Low and High Rise Building Frames Incorporating Metallic Yielding Dampers

There are many passive energy dissipating devices designed to dissipate earthquake energy in a structure. Metallic yielding dampers is one of these devices which are very efficient as they dissipate seismic input energy through hysteretic behavior. This research used ETABS software to analyze the performance of three metallic yielding dampers; X-shaped damper, Double X-Shaped and Comb Teeth Damper. The storey response data obtained from the analysis is storey shear. Each damper has three types of material; A992 steel, A36 steel and Aluminium. Concentrically braced steel frames with Chevron bracing were used and the dampers were placed in brace to beam orientation in each frame. The two types of frames analyzed were; low rise building with five storeys and a high rise building with twenty storeys. The site locations for both structures were in the region of California in the United States of America. The structures were analyzed by subjecting them to two earthquakes Loma Prieta and San Fernando as they were two of the major earthquakes that struck California in the nineties.

Nano-patterning of surfaces by ion sputtering: Numerical study of the anisotropic damped Kuramoto-Sivashinsky equation

Nonlinear models for pattern evolution by ion beam sputtering on a material surface present an ongoing opportunity for new numerical simulations. A numerical analysis of the evolution of preexisting patterns is proposed to investigate surface dynamics, based on a 2D anisotropic damped Kuramoto-Sivashinsky equation, with periodic boundary conditions. A finite-difference semi-implicit time splitting scheme is employed on the discretization of the governing equation. Simulations were conducted with realistic coefficients related to physical parameters (anisotropies, beam orientation, diffusion). The stability of the numerical scheme is analyzed with time step and grid spacing tests for the pattern evolution, and the Method of Manufactured Solutions has been used to verify the proposed scheme. Ripples and hexagonal patterns were obtained from a monomodal initial condition for certain values of the damping coefficient, while spatiotemporal chaos appeared for lower values. The anisotropy effects on pattern formation were studied, varying the angle of incidence of the ion beam with respect to the irradiated surface. Analytical discussions are based on linear and weakly nonlinear analysis.

Optimizing orientation of piezoelectric cantilever beam for harvesting energy from human walking

Harvesting energy from human body motion for powering small scale electronic devices is attracting research interest in recent years. Piezoelectric energy harvester (PEH) capable of harvesting energy from vibratory movement is a suitable candidate for this particular application. In this study, a cantilever beam with a piezoelectric patch attached at the end of the cantilever is evaluated for potential to harvest energy from human motion. Since the frequency of human walking motion is low, the frequency up conversion technique is adopted in this study to harvest the inertial energy. The effect of orientation of the cantilever beam with tip mass on the efficiency of the power generated is experimentally studied. A prototype is developed and attached onto the leg of a person walking on a treadmill at a constant speed. A theoretical lumped model is adopted to predict the voltage output using the experimentally measured acceleration as input data. Results show close agreement between the experiment and the model. Results also indicate that by varying the orientation of the PEH, the efficiency of the energy harvester can be significantly increased. Maximum power is found to be achieved when the PEH is orientated at 70° with reference to a coordinate system attached to the leg when walking on a treadmill.

Fraction-variant beam orientation optimization for non-coplanar IMRT

Conventional beam orientation optimization (BOO) algorithms for IMRT assume that the same set of beam angles is used for all treatment fractions. In this paper we present a BOO formulation based on group sparsity that simultaneously optimizes non-coplanar beam angles for all fractions, yielding a fraction-variant (FV) treatment plan. Beam angles are selected by solving a multi-fraction fluence map optimization problem involving 500-700 candidate beams per fraction, with an additional group sparsity term that encourages most candidate beams to be inactive. The optimization problem is solved using the fast iterative shrinkage-thresholding algorithm. Our FV BOO algorithm is used to create five-fraction treatment plans for digital phantom, prostate, and lung cases as well as a 30-fraction plan for a head and neck case. A homogeneous PTV dose coverage is maintained in all fractions. The treatment plans are compared with fraction-invariant plans that use a fixed set of beam angles for all fractions. The FV plans reduced OAR mean dose and D2 values on average by 3.3% and 3.8% of the prescription dose, respectively. Notably, mean OAR dose was reduced by 14.3% of prescription dose (rectum), 11.6% (penile bulb), 10.7% (seminal vesicle), 5.5% (right femur), 3.5% (bladder), 4.0% (normal left lung), 15.5% (cochleas), and 5.2% (chiasm). D2 was reduced by 14.9% of prescription dose (right femur), 8.2% (penile bulb), 12.7% (proximal bronchus), 4.1% (normal left lung), 15.2% (cochleas), 10.1% (orbits), 9.1% (chiasm), 8.7% (brainstem), and 7.1% (parotids). Meanwhile, PTV homogeneity defined as D95/D5 improved from .92 to .95 (digital phantom), from .95 to .98 (prostate case), and from .94 to .97 (lung case), and remained constant for the head and neck case. Moreover, the FV plans are dosimetrically similar to conventional plans that use twice as many beams per fraction. Thus, FV BOO offers the potential to reduce delivery time for non-coplanar IMRT.

A Prospective 4π Radiation Therapy Clinical Study in Recurrent High-Grade Glioma Patients

To evaluate the feasibility, safety, dosimetric benefits, delivery efficiency, and patient comfort in the clinical implementation of 4π radiation therapy. Eleven patients with recurrent high-grade glioma were recruited for the trial. 4π plans integrating beam orientation and fluence-map optimization were created using an in-house column-generation algorithm. The collision-free beam solution space throughout the 4π steradian was determined using a computer-aided-design model of the Varian TrueBeam system and a human subject. Twenty beams were optimized for each case and imported into Eclipse for intensity modulated radiation therapy planning. Beam orientations with neighboring couch kicks were merged for increased delivery efficiency, generating plans with an average of 16 beam orientations. Volumetric modulated arc therapy (VMAT) plans with 3-4 arcs were also generated for each case, and the plan achieving superior dosimetric quality was selected for treatment. Patient comfort was surveyed after every fraction. Multiple 2-dimensional X-ray images were obtained to measure intrafractional motion. Of 11 patients, 9 were treated with 4π. Mean and maximum organ at risk doses were equal or significantly lower (P<.05) with 4π than with VMAT. Particularly substantial dose reduction of 2.92Gy in the average accumulated brainstem maximum dose enabled treatments that would otherwise not satisfy safe dose constraints with VMAT. One patient was not treated because neither plan met the dosimetric criteria. The other was treated with VMAT owing to comparable dosimetry resulting from a planning target volume located in a separate co-plane superior to organs at risk. Treatments were well tolerated, with an average patient comfort score of 8.6/10. Intrafractional motion was <1.5mm for all delivered fractions, and the average delivery time was 34.1minutes. The feasibility, safety, dosimetric benefits, delivery efficiency, and patient comfort of 4π radiation therapy have been clinically demonstrated with a prospective clinical trial. The results elucidate the potential and challenges of wider clinical implementations.

Study on the Mainardi beam through the fractional Fourier transforms system

In this paper, we introduced the Mainardi beam and indicated its attributes under the Fractional Fourier transform for power variations of Fractional Fourier transform. The results represent that the behavior of the Mainardi beam is similar to that of the Airy beam. The obtained formula is a very powerful tool to describe propagation of a Mainardi beam through the FFT and the FrFT systems. An analytical expression of the Mainardi beam passing through an Fractional Fourier transform system presented. The influences of the Fractional Fourier transform, rational order of the Mittag-Leffler function (Fourier transform of the Mainardi function) on the normalized intensity distribution and characteristics of the Mainardi beam in the Fractional Fourier transform system examined. Power of the Fractional Fourier transform (p) and rational order of the Mittag-Leffler function (q) control characteristics of the Mainardi beam such as effective beam size, number, width, height, and orientation of the beam spot.

Evolutionary DVH evaluation for beam orientations in intensity modulated radiation therapy

Evolutionary DVH evaluation for beam orientations in intensity modulated radiation therapy