Assessing the predictability of five intraocular lens calculation methods in eyes with prior myopic keratorefractive lenticule extraction.

PURPOSE: To evaluate and compare the predictability of five methods of intraocular lens (IOL) calculation in eyes with prior keratorefractive lenticule extraction (KLEx) for the treatment of myopia. METHODS: A retrospective case study included 100 eyes of 52 patients who underwent myopia and myopia with astigmatism treatment with small incision lenticule extraction (SMILE). Preoperative and 3-month postoperative measurements of optical biometry and corneal tomography were obtained. The spherical equivalent of the refractive change induced by surgery was converted to the corneal plane (SMILE-dif). A physically well-defined method was developed in which the same IOL model was implanted before and after SMILE. IOL power was calculated using ray-tracing (RT-Sirius), and several IOL power calculation formulas (Kane, EVO 2.0, Barrett Universal II Formula, Hoffer QST) before surgery. After surgery, IOL power was calculated with RT-Sirius, Kane using Mean Pupil Power at 5.5 mm by ray tracing, EVO 2.0 Post Myopic LASIK/PRK, Barrett True K and Hoffer QST Post Myopic LASIK/PRK after surgery. The difference between the refractive error induced by the IOL before and after SMILE in the corneal plane (IOL-dif) was compared with SMILE-dif. The predicted error (PE) was calculated as the difference between SMILE-dif and IOL-dif. RESULTS: The PE obtained was 0.26 ± 0.55 diopters (D), 0.10 ± 0.45 D, 0.40 ± 0.37 D, -0.03 ± 0.36 D, 0.02 ± 0.51 D, with RT-Sirius, Kane, EVO 2.0, Barrett True K, and Hoffer QST respectively. PE was not statistically significantly different between Barrett True K and Hoffer QST, with differences being more homogeneous with Barrett, (variance σ2 = 0,13). The absolute EP obtained with Barrett True K achieved 84% of cases within ± 0.5 D, followed by Kane (72%), Hoffer QST (65%), EVO (61%) and RT-Sirius (59%). CONCLUSIONS: Barrett True K formula was the most accurate method for IOL calculation in eyes that had undergone SMILE for the correction of myopia. KEY MESSAGES: What is known The literature regarding IOL power calculation after SMILE is sparse, and the methods used to estimate corneal power following LASIK/PRK may not be applicable to SMILE procedures. The most common approach to investigating the predictability of IOL calculation formulas involves a theoretical model encompassing the virtual implantation of an IOL. What is new The Hoffer QST formula, Kane formula using Mean Pupil Power at 5.5 mm, EVO 2.0, and Sirius' Ray Tracing software had not been previously evaluated using this approach. The Barrett True K formula was the most accurate method for IOL calculation in eyes that had undergone SMILE for myopia correction, outperforming Ray Tracing.

A Multi Comparison of 8 Different Intraocular Lens Biometry Formulae, Including a Machine Learning Thin Lens Formula (MM) and an Inbuilt Anterior Segment Optical Coherence Tomography Ray Tracing Formula.

A comparison of the accuracy of intraocular lens (IOL) power calculation formulae, including SRK/T, HofferQ, Holladay 1, Haigis, MM, Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO), and AS-OCT ray tracing, was performed. One hundred eyes implanted with either the Rayone EMV RAO200E (Rayner Intraocular Lenses Limited, Worthing, UK) or the Artis Symbiose (Cristalens Industrie, Lannion, France) IOL were included. Biometry was obtained using IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany) and MS-39 AS-OCT (CSO, Firenze, Italy). Mean (MAE) and median (MedAE) absolute errors and percentage of eyes within ±0.25D, ±0.50D, ±0.75D, and ±1.00D of the target were compared, with ±0.75D considered a key metric. The highest percentage within ±0.75D was found with MM (96%) followed by the Haigis (94%) for the enhanced monofocal IOL. SRK/T (94%) had the highest percentage within ±0.75D, followed by Holladay 1, MM, BUII, and ray tracing (all 90%) for the multifocal IOL. No statistically significant difference in MAE was found with both IOLs. EVO showed the lowest MAE for the enhanced monofocal and ray tracing for the multifocal IOL. EVO and ray tracing showed the lowest MedAE for the two respective IOLs. A similar performance with high accuracy across formulae was found. MM and ray tracing appear to have similar accuracy to the well-established formulae and displayed a high percentage of eyes within ±0.75D.

Optimization of Ray-Tracing-Guided LASIK Outcomes: A Prospective Comparative Study of ZZ InnovEyes Strategy versus Automated Strategy.

Purpose: To evaluate the effectiveness of Zhang and Zheng's InnovEyes (ZZ InnovEyes) strategy for optimizing outcomes of ray-tracing-guided laser in situ keratomileusis (LASIK) compared to the standard automated strategy. Methods: A total of 38 patients (71 eyes) undergoing therapeutic refractive surgery at Hangzhou MSK Eye Hospital were randomly assigned to the ZZ InnovEyes and automated groups using double-masked randomization. The study assessed visual acuity, refractive outcomes, and higher-order aberrations preoperatively and at 1-day, 2-week, 1-month, and 3-month follow-ups. Statistical analysis was done with Microsoft Excel and SPSS 19.0. Results: The exposure and control groups comprised 36 and 35 eyes, respectively. The ZZ InnovEyes group demonstrated significant advantages in manifest refraction spherical equivalent (MRSE) correction compared to the automated approach group (0.13 ± 0.30 D vs 0.62 ± 0.40 D, p < 0.001), achieving 97.22% uncorrected distance visual acuity (UDVA) of 20/16 or better compared to 85.71% in the automated group at the 3-month follow-up (p = 0.08), and achieving 50.00% UDVA of 20/12.5 or better compared to 28.57% in the automated group at the 3-month follow-up (p = 0.06). Loss lines from preoperative corrected distance visual acuity to postoperative UDVA were lower in the ZZ InnovEyes group (0.00%) than the automated group (8.57%; p = 0.07). Both groups exhibited similar astigmatism corrections and higher-order aberrations. Conclusion: The ZZ InnovEyes strategy, which incorporates manifest and wavefront refraction for ray-tracing-guided LASIK, demonstrated superior MRSE correction and potential advantages in visual acuity outcomes compared to the standard automated strategy. This study highlights the need for ongoing optimization and research in refractive surgery. Clinical Trial Registration Number: ChiCTR2300078709.

A GPU-accelerated Monte Carlo code, RT2for coupled transport of photon, electron/positron, and neutron.

Objective.This work aims to develop a graphics processing unit (GPU)-accelerated Monte Carlo code for the coupled transport of photon, electron/positron and neutron over a broad range of energies for medical applications.Approach.By separating the MC evolution of radiation into source, transport, and interaction kernels, the branch divergence was alleviated. The memory coalescence was achieved by vectorizing the access pattern in which the secondary particles were archived. To accelerate further particle tracking, ray-tracing hardware acceleration in the Nvidia OptiXTMframework was applied. For photon and electron/positron, the EGSnrc interaction modules were ported as a GPU-optimized configuration. For neutron, a group-wised transport based on NJOY21 preprocessed data was implemented. The developed code was validated against CPU-based FLUKA. Neutron, x-ray and electron beams incident on water and ICRP phantoms were simulated. The neutron energy group and the transport parameters of photon and electron were set to be the same in both codes. A single Nvidia RTX 4090 card was used in this code while all 20 threads of a single Intel Core i9-10900K node were used in FLUKA.Main results.The number of histories was set to ensure that statistical uncertainties lower than 2% for all voxels whose doses were larger than 20% of the maximum. In all cases, the dose differences in the voxels between the codes were within 2.5%. For photons and electrons, the developed code was 150-300 times faster than FLUKA in both geometries. For neutrons, the code was respectively 80 and 135 times faster in the water and ICRP phantoms than FLUKA.Significance.This study offers an appropriate solution for uncoalesced memory access and branch divergence commonly encountered in coupled MC transport on the GPU architecture. The formidable acceleration in computing times and accuracy shown in this study can promise a routine clinical use of MC simulations.

An Overview of Millimeter-Wave Radar Modeling Methods for Autonomous Driving Simulation Applications.

Autonomous driving technology is considered the trend of future transportation. Millimeter-wave radar, with its ability for long-distance detection and all-weather operation, is a key sensor for autonomous driving. The development of various technologies in autonomous driving relies on extensive simulation testing, wherein simulating the output of real radar through radar models plays a crucial role. Currently, there are numerous distinctive radar modeling methods. To facilitate the better application and development of radar modeling methods, this study first analyzes the mechanism of radar detection and the interference factors it faces, to clarify the content of modeling and the key factors influencing modeling quality. Then, based on the actual application requirements, key indicators for measuring radar model performance are proposed. Furthermore, a comprehensive introduction is provided to various radar modeling techniques, along with the principles and relevant research progress. The advantages and disadvantages of these modeling methods are evaluated to determine their characteristics. Lastly, considering the development trends of autonomous driving technology, the future direction of radar modeling techniques is analyzed. Through the above content, this paper provides useful references and assistance for the development and application of radar modeling methods.

Power Enhancement and Spot Homogenization Design for Arrayed Semiconductor Lasers.

Improving the spot brightness and uniformity of arrangement of the array laser is conducive to ensuring the beam quality of the fiber laser. Based on the light tracing principle, the optical model performance of two common fiber lasers was first analyzed. Then, a novel rotationally polarized optical model with high power and spot uniformity was designed and optimized on the basis of the aforementioned analysis. The results of the evaluation metrics of the multi-indicator optical model show that the spot uniformity of our proposed model improved by 24.03%, the power improved by 0.55%, and the maximum light distance was shortened from 120 mm to 82.58 mm. Further, the results of the coupling tolerance analysis of the optical elements show that the total coupling efficiency was 89.04%. The coupling power and tolerance relationships did not produce degradation compared with the traditional model. Extensive comparative results show that the designed rotationally polarized optical path model can effectively improve the optical coupling efficiency and spot uniformity of arrayed semiconductor lasers.

Universal simulation of absorption effects for X-ray diffraction in reflection geometry.

Analytical calculations of absorption corrections for X-ray powder diffraction experiments on non-ideal samples with surface roughness, porosity or absorption contrasts from multiple phases require complex mathematical models to represent their material distribution. In a computational approach to this problem, a practicable ray-tracing algorithm is formulated which is capable of simulating angle-dependent absorption corrections in reflection geometry for any given rasterized sample model. Single or multiphase systems with arbitrary surface roughness, porosity and spatial distribution of the phases in any combination can be modeled on a voxel grid by assigning respective values to each voxel. The absorption corrections are calculated by tracing the attenuation of X-rays along their individual paths via a modified shear-warp algorithm. The algorithm is presented in detail and the results of simulated absorption corrections on samples with various surface modulations are discussed in the context of published experimental results.

Ray-tracing analytical absorption correction for X-ray crystallography based on tomographic reconstructions.

Processing of single-crystal X-ray diffraction data from area detectors can be separated into two steps. First, raw intensities are obtained by integration of the diffraction images, and then data correction and reduction are performed to determine structure-factor amplitudes and their uncertainties. The second step considers the diffraction geometry, sample illumination, decay, absorption and other effects. While absorption is only a minor effect in standard macromolecular crystallography (MX), it can become the largest source of uncertainty for experiments performed at long wavelengths. Current software packages for MX typically employ empirical models to correct for the effects of absorption, with the corrections determined through the procedure of minimizing the differences in intensities between symmetry-equivalent reflections; these models are well suited to capturing smoothly varying experimental effects. However, for very long wavelengths, empirical methods become an unreliable approach to model strong absorption effects with high fidelity. This problem is particularly acute when data multiplicity is low. This paper presents an analytical absorption correction strategy (implemented in new software AnACor) based on a volumetric model of the sample derived from X-ray tomography. Individual path lengths through the different sample materials for all reflections are determined by a ray-tracing method. Several approaches for absorption corrections (spherical harmonics correction, analytical absorption correction and a combination of the two) are compared for two samples, the membrane protein OmpK36 GD, measured at a wavelength of λ = 3.54 Å, and chlorite dismutase, measured at λ = 4.13 Å. Data set statistics, the peak heights in the anomalous difference Fourier maps and the success of experimental phasing are used to compare the results from the different absorption correction approaches. The strategies using the new analytical absorption correction are shown to be superior to the standard spherical harmonics corrections. While the improvements are modest in the 3.54 Šdata, the analytical absorption correction outperforms spherical harmonics in the longer-wavelength data (λ = 4.13 Å), which is also reflected in the reduced amount of data being required for successful experimental phasing.

Ultra-short time-echo based ray tracing for transcranial focused ultrasound aberration correction in human calvaria.

OBJECTIVE: Magnetic resonance guided transcranial focused ultrasound holds great promises for treating neurological disorders. This technique relies on skull aberration correction which requires computed tomography (CT) scans of the skull of the patients. Recently, ultra-short time-echo (UTE) magnetic resonance (MR) sequences have unleashed the MRI potential to reveal internal bone structures. In this study, we measure the efficacy of transcranial aberration correction using UTE images. Approach. We compare the efficacy of transcranial aberration correction using UTE scans to CT based correction on four skulls and two targets using a clinical device (Exablate Neuro, Insightec, Israel). We also evaluate the performance of a custom ray tracing algorithm using both UTE and CT estimates of acoustic properties and compare these against the performance of the manufacturer's proprietary aberration correction software. Main results. UTE estimated skull maps in Hounsfield units (HU) had a mean absolute error of 242 ± 20 HU (n=4). The UTE skull maps were sufficiently accurate to improve pressure at the target (no correction: 0.44 ± 0.10, UTE correction: 0.79 ± 0.05, manufacturer CT: 0.80 ± 0.05), pressure confinement ratios (no correction: 0.45 ± 0.10, UTE correction: 0.80 ± 0.05, manufacturer CT: 0.81 ± 0.05), and targeting error (no correction: 1.06 ± 0.42 mm, UTE correction 0.30 ± 0.23 mm, manufacturer CT: 0.32 ± 0.22) (n=8 for all values). When using CT, our ray tracing algorithm performed slightly better than UTE based correction with pressure at the target (UTE: 0.79 ± 0.05, CT: 0.84 ± 0.04), pressure confinement ratios (UTE: 0.80 ± 0.05, CT: 0.84 ± 0.04), and targeting error (UTE: 0.30 ± 0.23 mm, CT: 0.17 ± 0.15). Significance. These 3D transcranial measurements suggest that UTE sequences could replace CT scans in the case of MR guided focused ultrasound with minimal reduction in performance which will avoid ionizing radiation exposure to the patients and reduce procedure time and cost. .

Comparison of radiant intensity in aqueous media using experimental and numerical simulation techniques.

Accurately modelling the propagation of radiant intensity in aqueous environments poses significant challenges for both academia and industry, due to complex interactions like absorption, scattering, and reflection. This study aims to improve the accuracy of optical modeling in water-based systems by comparing experimental data with numerical simulation techniques, addressing the need for more reliable simulation methods in multiple applications like treatment of water and environmental monitoring.Implementation has been done by analyzing how the method compares with the discrete ordinate method, radiometry, and actinometry. The study further quantifies the effect of the photoreactor quartz tube on measured intensity for multiple wavelengths. Losses in light intensity are estimated to be 10 ± 0.5% for FX-1 265 source. In contrast, the simulation in a water medium showed an increase of up to 64% in the light intensity delivered to the central part of the tube due to internal reflections and scattering. Model predictions from ray tracing successfully compared with the Discrete Ordinate Method (DOM) and experimental data (within ± 6%), ensuring the accurate design of complex systems for water disinfection. The data from simulations is seen to tackle challenges faced in complex radiation modeling and demonstrates that the method can be utilized as a useful tool for optimization and prediction.

Wavefront analysis and phase correctors design using SHADOW.

Knife-edge imaging is a successful method for determining the wavefront distortion of focusing optics such as Kirkpatrick-Baez mirrors or compound refractive lenses. In this study, the wavefront error of an imperfect elliptical mirror is predicted by developing a knife-edge program using the SHADOW/OASYS platform. It is shown that the focusing optics can be aligned perfectly by minimizing the parabolic and cubic coefficients of the wavefront error. The residual wavefront error provides precise information about the figure/height errors of the focusing optics suggesting it as an accurate method for in situ optical metrology. A Python program is developed to design a customized wavefront refractive corrector to minimize the residual wavefront error. Uniform beam at and out of focus and higher peak intensity are achieved by the wavefront correction in comparison with ideal focusing. The developed code provides a quick way for wavefront error analysis and corrector design for non-ideal optics especially for the new-generation diffraction-limited sources, and saves considerable experimental time and effort.

A RT-FDTD method of analyzing wireless propagation characteristics in underground mine.

Efficient communication is crucial in reducing injuries and fatalities in coal mine accidents, necessitating the study of simulation methods for mine communication. When transceiver antennas are positioned close to the same side of the tunnel, the simulation results from the Ray Tracing (RT) method exhibit significant errors. Additionally, the Finite-Difference Time-Domain (FDTD) method demands substantial computational resources. In response to these challenges, we propose a RT-FDTD method, guided by the law of conservation of energy. This approach involves dividing the mine tunnel into a cuboidal region, using the RT method to calculate the electric field strength on the cuboid's surface, and then employing this as the excitation source for the FDTD method. Subsequently, the FDTD method is used to calculate the electric field strength within the cuboid. Experimental results demonstrate that the RT-FDTD method effectively mitigates the limitations of the RT and FDTD methods, enhancing both the efficiency and accuracy of simulations in underground mine.

LiMOX-A Point Cloud Lidar Model Toolbox Based on NVIDIA OptiX Ray Tracing Engine.

Virtual testing and validation are building blocks in the development of autonomous systems, in particular autonomous driving. Perception sensor models gained more attention to cover the entire tool chain of the sense-plan-act cycle, in a realistic test setup. In the literature or state-of-the-art software tools various kinds of lidar sensor models are available. We present a point cloud lidar sensor model, based on ray tracing, developed for a modular software architecture, which can be used stand-alone. The model is highly parametrizable and designed as a toolbox to simulate different kinds of lidar sensors. It is linked to an infrared material database to incorporate physical sensor effects introduced by the ray-surface interaction. The maximum detectable range depends on the material reflectivity, which can be covered with this approach. The angular dependence and maximum range for different Lambertian target materials are studied. Point clouds from a scene in an urban street environment are compared for different sensor parameters.

Intraocular lens power calculation using total keratometry and ray tracing in eyes with previous small incision lenticule extraction - A case series.

Purpose: To assess the IOL power calculation accuracy in post-SMILE eyes using ray tracing and a range of total keratometry based IOL calculation formulae. Observations: Ray tracing showed excellent predictability in IOL power calculation after SMILE and its accuracy was clinically comparable with the Barrett TK Universal II and Haigis TK formula. Conclusions and importance: Incorporating posterior corneal curvature measurements into IOL power calculation after SMILE seems prudent. The ray tracing method as well as selected TK-based formulae yielded excellent accuracy and should be favored in post-SMILE eyes.

Asymmetric imaging through engineered Janus particle obscurants using a Monte Carlo approach for highly asymmetric scattering media.

The advancement of imaging systems has significantly ameliorated various technologies, including Intelligence Surveillance Reconnaissance Systems and Guidance Systems, by enhancing target detection, recognition, identification, positioning, and tracking capabilities. These systems can be countered by deploying obscurants like smoke, dust, or fog to hinder visibility and communication. However, these counter-systems affect the visibility of both sides of the cloud. In this sense, this manuscript introduces a new concept of a smoke cloud composed of engineered Janus particles to conceal the target image on one side while providing clear vision from the other. The proposed method exploits the unique scattering properties of Janus particles, which selectively interact with photons from different directions to open up the possibility of asymmetric imaging. This approach employs a model that combines a genetic algorithm with Discrete Dipole Approximation to optimize the Janus particles' geometrical parameters for the desired scattering properties. Moreover, we propose a Monte Carlo-based approach to calculate the image formed as photons pass through the cloud, considering highly asymmetric particles, such as Janus particles. The effectiveness of the cloud in disguising a target is evaluated by calculating the Probability of Detection (PD) and the Probability of Identification (PID) based on the constructed image. The optimized Janus particles can produce a cloud where it is possible to identify a target more than 50% of the time from one side (PID > 50%) while the target is not detected more than 50% of the time from the other side (PD < 50%). The results demonstrate that the Janus particle-engineered smoke enables asymmetric imaging with simultaneous concealment from one side and clear visualization from the other. This research opens intriguing possibilities for modern obscurant design and imaging systems through highly asymmetric and inhomogeneous particles besides target detection and identification capabilities in challenging environments.

In-situ sparse-array imaging for through-thickness cracks in plates with A0 Lamb waves and an efficient waveform inversion algorithm.

Structural health monitoring (SHM) requires efficient online crack detection and characterization to prevent structural failures, which mainly arise from fatigue cracks. Existing solutions for crack characterization involve analyzing sensed wave signals directly, but these approaches usually require onerous steps or many sensors to obtain sufficient and clear wave packets. An alternative strategy is a model-based inversion, which takes the full waveform into consideration and does not require analysis on a single wave packet. This approach can achieve accurate characterization with fewer sensors and simpler implementation. We propose an efficient model based on the Huygens' principle and the no-mode-conversion property of the A0 mode Lamb waves to meet the requirements of online monitoring. We then verify the proposed model-based crack imaging method through simulation and experiments on smooth and rough cracks. The proposed method is easy, cheap, and efficient, making it a desirable option for SHM tasks.

The Design and Fabrication of Large-Area Under-Screen Fingerprint Sensors with Optimized Aperture and Microlens Structures.

In this paper, we designed and fabricated an optical filter structure applied to the FoD (Fingerprint on Display) technology of the smartphone, which contains the microlens array, black matrix, and photodetector to recognize the fingerprint on a full touchscreen. First, we used optical ray tracing software, ZEMAX, to simulate a smartphone with FoD and a touching finger. We then further discussed how the aperture and microlens influence the fingerprint image in this design. Through numerical analysis and process constraint adjustment to optimize the structural design, we determined that a modulation transfer function (MTF) of 60.8% can be obtained when the thickness of the black matrix is 4 µm, allowing successful manufacturing using photolithography process technology. Finally, we used this filter element to take fingerprint images. After image processing, a clearly visible fingerprint pattern was successfully captured.

EDOF intraocular lens design: shift in image plane vs object vergence.

BACKGROUND: To compare 2 different design scenarios of EDOF-IOLs inserted in the Liou-Brennan schematic model eye using raytracing simulation as a function of pupil size. METHODS: Two EDOF IOL designs were created and optimized for the Liou-Brennan schematic model eye using Zemax ray tracing software. Each lens was optimized to achieve a maximum Strehl ratio for intermediate and far vision. In the first scenario, the object was located at infinity (O1), and the image plane was positioned at far focus (I1) and intermediate focus (I2) to emulate far and intermediate distance vision, respectively. In the second scenario, the image plane was fixed at I1 according to the first scenario. The object plane was set to infinity (O1) for far-distance vision and then shifted closer to the eye (O2) to reproduce the corresponding intermediate vision. The performance of both IOLs was simulated for the following 3 test conditions as a function of pupil size: a) O1 to I1, b) O1 to I2, and c) O2 to I1. To evaluate the imaging performance, we used the Strehl ratio, the root-mean-square (rms) of the spot radius, and the spherical aberration of the wavefront for various pupil sizes. RESULTS: Evaluating the imaging performance of the IOLs shows that the imaging performance of the IOLs is essentially identical for object/image at O1/I1. Designed IOLs perform dissimilarly to each other in near-vision scenarios, and the simulations confirm that there is a slight difference in their optical performance. CONCLUSION: Our simulation study recommends considering the difference between object shift and image plane shift in design and test conditions to achieve more accurate pseudoaccommodation after cataract surgery.

Neural-Network-Based Localization Method for Wi-Fi Fingerprint Indoor Localization.

Despite the high demand for Internet location service applications, Wi-Fi indoor localization often suffers from time- and labor-intensive data collection processes. This study proposes a novel indoor localization model that utilizes fingerprinting technology based on a convolutional neural network to address this issue. The aim is to enhance Wi-Fi indoor localization by streamlining the data collection process. The proposed indoor localization model leverages a 3D ray-tracing technique to simulate the wireless received signal strength intensity (RSSI) across the field. By incorporating this advanced technique, the model aims to improve the accuracy and efficiency of Wi-Fi indoor localization. In addition, an RSSI heatmap fingerprint dataset generated from the ray-tracing simulation is trained on the proposed indoor localization model. To optimize and evaluate the model's performance in real-world scenarios, experiments were conducted using simulated datasets obtained from the publicly available databases of UJIIndoorLoc and Wireless InSite. The results show that the new approach solves the problem of resource limitation while achieving a verification accuracy of up to 99.09%.

Ray theory-based compounded plane wave ultrasound imaging for aberration corrected transcranial imaging: Phantom experiments and simulations.

Compounded plane wave imaging (CPWI) allows high-frame-rate measurement and has been one of the most promising modalities for real-time brain imaging. However, ultrasonic brain imaging using the CPWI modality is usually performed with a worn thin or removal of the skull layer. Otherwise, the skull layer is expected to distort the ultrasonic wavefronts and significantly decrease intracranial imaging quality. The motivation of this study is to investigate a CPWI method for transcranial brain imaging with the skull layer. A coordinate transformation ray-tracing (CTRT) approach was proposed to track the distorted ultrasonic wavefronts and calculate the time delays for the ultrasound plane wave passing through the skull layer. With an accurate correction for the time delays in beamforming, the CTRT-based CPWI could achieve high-quality intracranial images with the presence of skulls. The proposed CTRT-based CPWI method was verified using a simplified three-layer transcranial model. The full-wave simulation demonstrated that CTRT could accurately (i.e., relative percentage error less than0.18%) track the distorted transmitting wavefront through skull. Compared with the CPWI without aberration correction, the CTRT-based CPWI provided high-quality intracranial imaging and could accurately localize intracranial point scatterers; specifically, positioning error decreases from 0.5 mm to 0.1 mm on average in the axial direction and from 0.7 mm to 0.1 mm on average in the lateral direction. As the compounded angles increased in the CTRT-based CPWI, the contrast improved by 16.2 dB on average for the region of interest, and the array performance indicator (representing resolution) decreased by 4.0 on average for the intracranial point scatterers. The CTRT is of low computational cost compared with full wave simulation. This study suggested that the proposed CTRT-based CPWI might have the potential for real-time and non-invasive transcranial aberration-corrected imaging.