Virtual Source Position Research Articles

Sonification of a juggling performance using spatial audio

We developed a new musical instrument by equipping juggling balls with accelerometers, gyroscopes, and WiFi sensors. The system measures acceleration and rotation, allowing us to distinguish between ball movement and static states. We can determine the direction of each throw based on the acceleration data. A movement-driven instrument animates the virtual audio source position based on the throw direction. A different synthesizer is assigned to each ball, resulting in a synesthetic experience. The system integrates the juggling patterns simulator with OSC and MIDI API, allowing real-time rhythm generation and composition.

Using convergent half width half Maximum(c-HWHM) tilting method to determine the virtual source position of scanning-pass scattering beam in carbon ion therapy

IntroductionWe developed a half-width half-maximum tilting angle convergent method to replace the conventional measurement of the virtual source position for scanning-pass scattering beam in carbon ion therapy. Materials and methodsA homemade large-format CMOS sensor and Gaf Chromic EBT3 films were used for the virtual source position measurement. The Gaf films were embedded in a self-designed rectangular plastic frame to tighten the films and set up on a treatment couch for irradiation in the air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the SAD. The radiation rectangular field size in horizontal and vertical directions on film or detector delivered by 5 carbon ion energies were analyzed separately in this study. The virtual source position was determined with film or detector at a distance upstream or downstream from the various source-film-distance by the half width half maximum tilting angle convergent method to compare the results conducted with the same measurement condition by the back projecting the FWHM to zero methods. ResultsThe determination of virtual source position by using half width half maximum tilting angle convergent method agrees with the method by back projecting the FWHM to zero, and for higher carbon ion energy has an obvious longer virtual source position since the more carbon ion beam energy, hence, the less side scatter results in the less divergent at the downstream, then the virtual source positions is distal for high energies than low energies when back projects the field sizes to zero. ConclusionWe have developed a technique capable of dealing with the virtual source position with a geometric convergent method to avoid any mistakes in the passive scatter carbon ion beam. The method for investigating the virtual source position in the carbon ion beam in this study can also be used for electrons and proton beams.

The study of virtual source position with the geometric convergent ratio errors prevention management method of spot scanning beam in carbon ion therapy.

We developed a technique including preventing errors management method capable of dealing with the virtual source position delivered by different carbon ion energies from the pattern of spot scanning beam in this study. A homemade large-format complementary metal-oxide-semiconductor (CMOS) sensor and Gaf Chromic EBT3 films were used for the virtual source position measurement. The Gaf films were embedded in a self-designed rectangular plastic frame to tighten the films and set up on a treatment couch for irradiation in the air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the SAD. The horizontal carbon ion beam with five energies at a machine opening field size was carried out in this study. The virtual source position was determined mainly with a linear regression by back projecting the full width half maximum (FWHM) to zero at a distance upstream from the various source-film-distance and double checks additionally with a geometric convergent method to avoid any mistakes caused by manual measurement on FWHM. The virtual source position for higher carbon ion energy has an obvious longer distance from the SAD since the more carbon ion beam energy, the less spreading affected by the horizontal and vertical magnetism, therefore, the distance of virtual source positions is decreased from SAD with high to low energy. The method for investigating the virtual source position in the carbon ion beam in this study can also be used for electrons and the proton. We have developed a technique capable of dealing with the virtual source position with a geometric convergent method to avoid any mistakes in spot scanning carbon ion beam.

The determination of virtual source position using convergent arcCOS method for scanning-passive scatter beam in carbon ion therapy

The determination of virtual source position using convergent arcCOS method for scanning-passive scatter beam in carbon ion therapy

The Determination of Virtual Source Position Using Poka-Yoke Concept to Minimize Mistakes for Scanning-Passive Scatter Beam in Carbon Ion Therapy

The Determination of Virtual Source Position Using Poka-Yoke Concept to Minimize Mistakes for Scanning-Passive Scatter Beam in Carbon Ion Therapy

Improved imaging technique for nondestructive evaluation using arbitrary virtual array source aperture (AVASA)

In this paper, we propose a new phased array imaging technique called Arbitrary Virtual Array Source Aperture (AVASA) to image deeper defects with an improved SNR with fewer transmissions. The approach is to transmit the ultrasound waves by electronic beamforming at several arbitrary virtual source positions to achieve higher focal depth to increase the SNR of the received A-scans. Backscattered signals are recorded with all the array elements. A high-resolution image is obtained on reception by virtually focusing on every point in the region of interest by signal coherence summation. In this paper, the proposed AVASA and TFM methods are employed for scanning the larger thickness structure with an unknown defect nature to contrast the defect SNR and the number of defect imaging. Compared with TFM imaging, the AVASA method shows a significantly increasing defect-detecting range with higher amplitude. To further improve the imaging quality and reduce the reconstruction time, the influence of the virtual source parameters on the AVASA imaging and a scanning strategy is demonstrated. A good agreement between the AVASA and TFM is observed, and the number of transmissions is required to inspect the test specimen using AVASA reduced by a factor of four to eight.

The determination of virtual source position using convergent anti-trigonometric functions (arcCOS and arcSIN) method for scanning-passive scatter beam in carbon ion therapy

Abstract Introduction: We developed a convergent trigonometric functions technique (arcCOS, arcSIN) capable of dealing with the virtual source position delivered by different carbon ion energies from the pattern of scanning-passive scatter beam in this study. Materials and Methods: A home-made large-format CMOS sensor and Gaf Chromic EBT3 films were used for the virtual source position measurement. The Gaf films were embedded in a self-designed rectangular plastic frame to tighten the films and set up on a treatment couch for irradiation in the air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the SAD. The horizontal carbon ion beam with 5 energies at a machine opening field size was carried out in this study. The virtual source position was determined with a convergent arcCOS and arcSIN methods and compared with the linear regression by back-projecting the FWHM to zero at a distance upstream from the various source-film-distance. Results: The film FWHM measurement error of 0.5 mm (the large-format CMOS detectors was in pixel, a pixel equals 0.5 mm) leads to 1×10-3% deviation of α(cACOS and cASIN) at every assumed virtual source position. The overall uncertainty for the reproducibility of the calculated virtual source position by the assumed t in the vertical and horizontal directions amounts to 0.1%. The errors of calculated virtual source position by assumed t with back projecting FWHM to zero methods were within 1.1 ± 0.001, p = 0.033. The distance of virtual source positions is decreased from SAD with high to low energy. Conclusion: We have developed a technique capable of dealing with the virtual source position with a convergent arcCOS and arcSIN methods to avoid any manual measurement mistakes in scanning-passive scatter carbon ion beam. The method for investigating the virtual source position in the carbon ion beam in this study can also be used for external electrons and the proton.

Determination of virtual source position using back projecting zero and convergent arcTAN method for scanning-passive scatter beam in carbon ion therapy.

This study aims to develop and test a new technique by using the convergent arcTAN (cATAN) method capable of dealing with the virtual source position delivered by different carbon ion energies from the pattern of scanning-passive scatter beam. A homemade large-format CMOS sensor and Gaf Chromic EBT3 films are used for the virtual source position measurement. The Gaf films are embedded in a self-designed rectangular plastic frame to tighten films and set up on a treatment couch for irradiation in air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the SAD. The horizontal carbon ion beam with 5 energies at a machine opening field size is carried out in this study. The virtual source position is determined by using the convergent arcTAN (cATAN) method and compared with a linear regression by back projecting FWHM to zero at a distance upstream from the various source-film-distance. The film FWHM measurement error of 0.5 mm leads to 0.001% deviation of α (cATAN) at every assumed textend. The overall uncertainty for the reproducibility of calculated virtual source position by the assumed textend in the vertical and horizontal directions amounts to 0.1%. The errors of calculated virtual source position by assumed textend with back projecting FWHM to zero methods are within 1.1±0.001, p = 0.033. We develop a new technique capable of dealing with the virtual source position with a convergent arcTAN method to avoid any manual measurement mistakes in scanning-passive scatter carbon ion beam. The readers are encouraged to conduct the proposed cATAN method in this study to investigate the virtual source position in the Linac-based external electron beams and the proton beams.

The determination of virtual source position using convergent arcSIN method for scanning-passive scatter beam in carbon ion therapy

IntroductionWe developed a convergent arcSIN (cASIN) technique capable of dealing with the virtual source position delivered by different carbon ion energies from the pattern of scanning-passive scatter beam in this study. Materials and methodsA homemade large-format CMOS sensor and Gaf Chromic EBT3 films were used for the virtual source position measurement. The Gaf films were embedded in a self-designed rectangular plastic frame to tight the films and set up on a treatment couch for irradiation in the air with the film perpendicular to the carbon ion beam at the nominal source-axis-distance (SAD) as well as upstream and downstream from the measurement point at SAD. The horizontal carbon ion beam with 5 energies at a machine opening field size was carried out in this study. The virtual source position was determined with a convergent arcSIN method and compared to the way used nowadays with the linear regression by back projecting the FWHM to zero at a SAD distance upstream from the various source-film-distance. ResultsThe determination of virtual source position using convergent arcSIN method agrees with the method by back projecting the FWHM to zero, and for higher carbon ion energy has an obvious longer distance from the SAD since the more carbon ion beam energy, the less spreading affected by the horizontal and vertical magnetism, therefore, the distance of virtual source positions is decreased from the SAD point with high to low energy. ConclusionWe have developed a technique capable of dealing with the virtual source position with a convergent arcSIN method to avoid any manual measurement mistakes as well as a double-check mistake-proofing in scanning-passive scatter carbon ion beam. The method for investigating the virtual source position in the carbon ion beam in this study can also be used for external electrons and the proton.

A Mathematical Method to Adjust MLC Leaf End Position for Accurate Dose Calculation in Carbon Ion Beam Radiation Therapy Treatment Planning System.

Introduction We present a mathematical method to adjust the leaf end position for dose calculation correction in the carbon ion radiation therapy treatment planning system. Methods and Materials A straggling range algorism of 400 MeV/n carbon ion beam in nine different multileaf collimator (MLC) materials was conducted to calculate the dose 50% point to derive the offset corrections in the carbon ion treatment planning system (ciPlan). The visualized light field edge position in the treatment planning system is denoted as Xtang.p, and MLC position (Xmlc.p) is defined as the source to leaf end midpoint projection on axis for monitor unit calculation. The virtual source position of energy at 400 MeV/n and straggling range in MLC at different field sizes were used to calculate the dose 50% position on axis. On-axis MLC offset (correction) could then be obtained from the position corresponding to 50% of the central axis dose minus the Xmlc.p. Results The exact MLC position in the carbon ion treatment planning system can be used as an offset to do the correction. The offset correction of pure tungsten is the smallest among the others due to its shortest straggling range of carbon ion beam in MLC. The positions of 50% dose of all MLC materials are always located in between Xtang.p and Xmlc.p under the largest field of 12 cm by 12 cm. Conclusions MLC offset should be adjusted carefully at different field sizes in the treatment planning systems especially of its small penumbra characteristic in the carbon ion beam. It is necessary to find out the dose 50% position for adjusting MLC leaf edge on-axis location in the treatment planning system to reduce dose calculation error.

Prestack diffraction separation in the common virtual source gather

Diffractions are the seismic responses of subsurface small-scale geologic discontinuities or inhomogeneities, whose energy is much weaker than that of reflections. To eliminate the masking effect of strong reflections on weak diffractions, a prestack diffraction separation method is proposed based on the common virtual source gather (CVSG) and the median filter. The reflection generated from a reflector can be regarded as originating from a virtual source (or a focused area). According to this behavior, the reflection can be transformed into its corresponding virtual source position to build the CVSG. Unlike the reflection, diffraction cannot be regarded as originating from one virtual source. Therefore, diffractions have a curved shape, whereas reflections are flat in the CVSG. Based on the traveltime moveout method, the reflection traveltime is calculated for describing reflection events and generating CVSG. Theory and a simple synthetic data test demonstrate that there is almost no energy lost when transforming between a shot gather and CVSG. Then, for removing the reflection, the median filter is used in the CVSG where the reflection appears as a linear event. Complex synthetic and field examples demonstrate that the proposed method can flatten reflection events and thus can separate diffraction events from strong reflections in the prestack domain.

Do near-field cues enhance the plausibility of non-individual binaural rendering in a dynamic multimodal virtual acoustic scene?

It is commonly believed that near-field head-related transfer functions (HRTFs) provide perceptual benefits over far-field HRTFs that enhance the plausibility of binaural rendering of nearby sound sources. However, to the best of our knowledge, no study has systematically investigated whether using near-field HRTFs actually provides a perceptually more plausible virtual acoustic environment. To assess this question, we conducted two experiments in a six-degrees-of-freedom multimodal augmented reality experience where participants had to compare non-individual anechoic binaural renderings based on either synthesized near-field HRTFs or intensity-scaled far-field HRTFs and judge which of the two rendering methods led to a more plausible representation. Participants controlled the virtual sound source position by moving a small handheld loudspeaker along a prescribed trajectory laterally and frontally near the head, which provided visual and proprioceptive cues in addition to the auditory cues. The results of both experiments show no evidence that near-field cues enhance the plausibility of non-individual binaural rendering of nearby anechoic sound sources in a dynamic multimodal virtual acoustic scene as examined in this study. These findings suggest that, at least in terms of plausibility, the additional effort of including near-field cues in binaural rendering may not always be worthwhile for virtual or augmented reality applications.

Auditory Localization in Low-Bitrate Compressed Ambisonic Scenes

The increasing popularity of Ambisonics as a spatial audio format for streaming services poses new challenges to existing audio coding techniques. Immersive audio delivered to mobile devices requires an efficient bitrate compression that does not affect the spatial quality of the content. Good localizability of virtual sound sources is one of the key elements that must be preserved. This study was conducted to investigate the localization precision of virtual sound source presentations within Ambisonic scenes encoded with Opus low-bitrate compression at different bitrates and Ambisonic orders (1st, 3rd, and 5th). The test stimuli were reproduced over a 50-channel spherical loudspeaker configuration and binaurally using individually measured and generic Head-Related Transfer Functions (HRTFs). Participants were asked to adjust the position of a virtual acoustic pointer to match the position of virtual sound source within the bitrate-compressed Ambisonic scene. Results show that auditory localization in low-bitrate compressed Ambisonic scenes is not significantly affected by codec parameters. The key factors influencing localization are the rendering method and Ambisonic order truncation. This suggests that efficient perceptual coding might be successfully used for mobile spatial audio delivery.

Localization of electron virtual SSD in a Siemens-Primus linear accelerator: Comparison of measurements with Monte Carlo simulation

Introduction: Because of importance of impact of the Source to Surface Distance (SSD) in determining of monitor unit for electron-therapy, it is essential to know the Virtual Source Position (VSP) for electron beam for a linear therapeutic accelerator for each energy and field size. , especially using the Khan method (photo distance squared method) And compare the results with Monte Carlo. Materials and Methods: The VSP was measured for a Siemens- Primus linear accelerator for all available electron beams (5, 7, 8, 10 and 12 MeV) and for five applicator sizes (5×5, 10×10, 15×15, 20×20, 25×25 cm2) available at the department in Mahdieh Radiotherapy and Oncology Charity center in Hamadan. A theoretical method (known as Khan’s method) was applied to estimate VSP for all electron energies and for all potential applicators. A valid MCNPX Monte Carlo code was then used to evaluate the results achieved through the measurements. Results:The results showed a significant difference between Monte Carlo those were found to be ~4% and 5.2% for F4 and F8 tally approaches, respectively. Conclusion: MonteCarlo simulation code with correction factor can be used as an alternative approach to verify measurements acquired for VSD and other datasets applied for treatment Planning Systems.

Virtual auditory aperture passability.

Two experiments investigated (1) the ability of individuals to perceive the passability of apertures that are constructed using two virtual sounds sources and (2) the nature of the perceptual information that is used when determining passability in such a way. In the first experiment, participants judged whether they could successfully walk between two sound sources, heard through headphones, without turning their shoulders. We hypothesized that judgements would be accurate and driven by the detection of a proposed informational variable that relates head rotation, forward locomotion and aperture width. To test this hypothesis, we used motion tracking and a gain manipulation to alter apparent head rotation relative to virtual sound source positions and evaluated the effect on performance. Participants were able to accurately judge aperture passability based only on acoustic information. However, the gain manipulation did not show a significant influence on perceptual reports. The unexpected significant influence of lateral head movement on perceptual accuracy, however, does suggest that an alternative informational variable, based on lateral movement, may have been used. In the second experiment, a group of participants with wide shoulders was compared to a group with narrow shoulders on a similar task. Significant differences in minimally acceptable aperture width were found between the wide and narrow groups. When these aperture widths were scaled to the participants' shoulder widths, however, the differences were no longer present. These findings are consistent with previous studies investigating perception of passability and offer promising applications of virtual reality technology in the study of auditory perceptual abilities.

Verification of Experimental Virtual Electron Source Position by Using Monte Carlo

Background: In the treatment with the electron beams to get the appropriate dose distribution in the tumor region, the distance between virtual electron source position and patient’s body should be correctly identified. This study is an attempt to find the effective SSD (Source-surface distance)by using the Monte Carlo N-particle (MCNP v1. 51) code to substitute the measurements in the clinic. Materials and Methods: The MC (Monte Carlo) simulation of Oncor Linac (Siemens Co. Germany) was done based on manufacturer data in 9 MeV electron beam energy. In order to obtain the values of effective SSD using the inverse slope (IS) technique, point doses are calculated at dmax (the depth of maximum dose on the central axis), inside of the water phantom model, with the phantom simulated first at the standard SSD (5 cm air gap) and then with an increasing air gap of 3, 6, 9 and 12 cm between the distal end of applicator and the phantom surface. Results: The measured and MC-calculated effective SSDs using IS method are presented and compared with those reported from other works. The effective SSDs were found to be 95.68 cm and 96.66 cm from the MC tallies of *F8 and *F4, respectively. In addition, the effective SSDs were found to be 95.59 cm from ion chamber measurement. Conclusion: Considering the results from three methods of calculation, and comparing the results with experimental methods, it was shown that Monte Carlo simulation is a useful method in determination of electron virtual source position.

Implementation of the Marchenko method

The Marchenko method makes it possible to compute subsurface-to-surface Green’s functions from reflection measurements at the surface. Applications of the Marchenko method have already been discussed in many papers, but its implementation aspects have not yet been discussed in detail. Solving the Marchenko equation is an inverse problem. The Marchenko method computes a solution of the Marchenko equation by an (adaptive) iterative scheme or by a direct inversion. We have evaluated the iterative implementation based on a Neumann series, which is considered to be the conventional scheme. At each iteration of this scheme, a convolution in time and an integration in space are performed between a so-called focusing (update) function and the reflection response. In addition, by applying a time window, one obtains an update, which becomes the input for the next iteration. In each iteration, upgoing and downgoing focusing functions are updated with these terms. After convergence of the scheme, the resulting upgoing and downgoing focusing functions are used to compute the upgoing and downgoing Green’s functions with a virtual-source position in the subsurface and receivers at the surface. We have evaluated this algorithm in detail and developed an implementation that reproduces our examples. The software fits into the Seismic Unix software suite of the Colorado School of Mines.

Edge shadow projection method for measuring the brightness of electron guns.

The performance of an electron gun is evaluated in terms of the gun brightness. The brightness of an electron gun is typically measured by dividing the angular current density by the virtual source area. An electron gun brightness measurement system was constructed without an electron lens. The system consists of movable apertures (∅ 30, 50, 100, 200 μm), a Faraday cup, and a phosphor screen. The Faraday cup is employed to measure the angular current density. The electron beam passes through an aperture and its shade is projected onto the phosphor screen. The virtual source position is determined by measuring the displacement of the aperture shade made by the movement of the aperture. The blurring width of the edge of the shadow on the screen is measured by a charged-coupled device camera to calculate the virtual source size. Brightness values of a tungsten filament electron gun were obtained and compared to reported values.

SU‐F‐T‐71: A Practical Method for Evaluation of Electron Virtual Source Position

Purpose:Since electrons are easily scattered, the virtual source position for electrons is expected to locate below the x‐ray target of Medical Linacs. However, the effective SSD method yields the electron virtual position above the x‐ray target for some applicators for some energy in Siemens Linacs. In this study, we propose to use IC Profiler (Sun Nuclear) for evaluating the electron virtual source position for the standard electron applicators for various electron energies.Methods:The profile measurements for various nominal source‐to‐detector distances (SDDs) of 100–115 cm were carried out for electron beam energies of 6–18 MeV. Two methods were used: one was to use a 0.125 cc ion chamber (PTW, Type 31010) with buildup mounted in a PTW water tank without water filled; and the other was to use IC Profiler with a buildup to achieve charge particle equilibrium. The full width at half‐maximum (FWHM) method was used to determine the field sizes for the measured profiles. Backprojecting (by a straight line) the distance between the 50% points on the beam profiles for the various SDDs, yielded the virtual source position for each applicator.Results:The profiles were obtained and the field sizes were determined by FWHM. The virtual source positions were determined through backprojection of profiles for applicators (5, 10, 15, 20, 25). For instance, they were 96.415 cm (IC Profiler) vs 95.844 cm (scanning ion chamber) for 9 MeV electrons with 10×10 cm applicator and 97.160 cm vs 97.161 cm for 12 MeV electrons with 10×10 cm applicator. The differences in the virtual source positions between IC profiler and scanning ion chamber were within 1.5%.Conclusion:IC Profiler provides a practical method for determining the electron virtual source position and its results are consistent with those obtained by profiles of scanning ion chamber with buildup.

Clinical Commissioning of a Pencil Beam Scanning Treatment Planning System for Proton Therapy

In this report, we present the commissioning and validation results for a commercial proton pencil beam scanning RayStation treatment planning system. The commissioning data requirements are (1) integrated depth dose curves, (2) spot profiles, (3) absolute dose/monitor unit calibration, and (4) virtual source position. An 8-cm parallel plate chamber was used to measure the integrated depth dose curves by scanning a beam composed of a single spot in a water phantom. The spot profiles were measured at 5 different planes using a 2-dimensional scintillation detector. The absolute dose/monitor unit calibration was based on dose measurements in single-layer fields of size 10 × 10 cm2. The virtual-source position was calculated from the change in spot spacing with the distance from the isocenter. The beam model validation consisted of a comparison against commissioning data as well as a new set of verification measurements. For end-to-end testing, a series of phantom plans were created. These plans were measured at 1 to 3 depths using a 2-dimensional ion chamber array and evaluated for gamma index using the 3% and 3 mm criteria. The maximum deviation for spot sigma measured versus calculated was -0.2 mm. The point-dose measurements for single-layer beams were within ± 3%, except for the largest field size (29 × 29 cm2) and the highest energy (226 MeV). The point doses in the spread-out Bragg peak plans showed a trend in which differences > 3% were seen for ranges > 30 cm, field sizes > 15 × 15 cm2, and depths > 25 cm. For end-to-end testing, 34 planes corresponding to 13 beams were analyzed for gamma index with a minimum pass rate of 92.8%. The acceptable verification results and successful end-to-end testing ensured that all components of the treatment planning system were functional and the system was ready for clinical use.