Ray Imaging Research Articles

Accelerating Kirchhoff Pre-stack depth migration on a GPU by overlapping ray tracing and imaging

Kirchhoff-based depth migration is in great demand for imaging at large scales and high-density seismic data exploration. A Graphic Processing Unit, or GPU, can compose a heterogeneous hardware that contains a traditional Central Processing Unit (CPU), and it can greatly accelerate migration calculations. An improved acceleration method is proposed here that uses overlapped ray tracing, which provides two-way travel times, and an imaging kernel. In our method, ray tracing is calculated by the CPU due to its complicated divergences. The imaging kernel is passed to the GPU by unlooping the imaging volume. Streams and asynchronous calculation functions are used to overlap the imaging kernel of a previous trace to the ray tracing of the next trace. The nvprof profiling tool, along with the elapsed time, are used to measure the efficiency of the accelerated work, and it is found that the GPU code results in a speedup factor of 60 relative to single thread CPU code, and when using the overlapped computation, the GPU efficiency is improved by 30%. This method shows great potential for further application in large scale seismic data imaging with GPU.

High precision integrated projection imaging optical design based on microlens array.

We propose a microlens array (MLA) construction method based on sub-channel optimal design and splicing, and an integrated projection imaging analysis method by using ray tracing and image warping. Our stop mask greatly improves imaging quality and eliminates crosstalk. We realize various projection distances, required projection imaging dimensions, and design optimization of sub-lens structures, providing freedom and possibility for MLA structure design requirements. Optical system chief ray tracing and sub-image generation is combined by using radial basis function forward image warping. Imaging distortion and overlap misalignment from short focal projection, multi-aperture offset, and complicated surfaces are perfectly corrected. Sub-image warping pixel mapping facilitates real-time replacement of projected images. We conduct substantial MLA integration imaging designs and precision analysis of different sub-aperture sizes, MLA sizes, and projection distances.

Compton-based prompt gamma imaging using ordered origin ensemble algorithm with resolution recovery in proton therapy

Prompt gamma ray (PG) imaging based on Compton camera (CC) is promising to realize in vivo verification during the proton therapy. However, the finite spatial and energy resolution of current CC, as well as the Doppler broaden effect, degrade the quality and resolution of PG images. In addition, due to the inherent geometrical complexity of Compton camera data, PG imaging can be time-consuming and difficult to reconstruct in real-time, while using standard techniques such as filtered back-projection or maximum likelihood-expectation maximization. In this paper, we propose three modifications of origin ensembles with resolution recovery (OE-RR) algorithm based on Markov chains to accelerate the convergence to equilibrium of OE-RR algorithm and improve the image quality. For evaluation, we performed a Monte Carlo simulation of a three-stage CZT Compton camera with resolution loss to detect the PG produced by a proton beam in a water phantom, and evaluate image quality of the gamma rays emitted during proton irradiation. The results show that our ordered OE-RR algorithm realized a good resolution recovery and accurate estimation of the position, including the peak and the distal falloff of the PG emission with remarkably faster reconstruction, thus demonstrating the feasibility of this new method in non-idealized PG-based proton range verification.

269. Pediatric front to back X-ray chest exposure: Image quality and dose optimization

Purpose In this study we changed the acquisition parameters in chest X-ray of 5 years old pediatric patients in order to lower radiation dose and preserve image quality. A new acquisition technique (T2) was compared to the previous (T1). The comparison regarded dosimetric and a qualitative assessment on phantom and on patients. Methods For dose evaluation we calculated the ESD on a phantom and on patients and we used PCXMC software to evaluate the effective dose (E). We used the TO.20 Leeds Test and AutoPIA software to perform an analysis on a plexiglass phantom simulating patient with the test in between, exposing the phantom to different parameters in order to choose the best technique to use: T2 and comparing it with T1 [1] . The images were analysed from a quantitative viewpoint determining the Correct Observation Ratio% (COR%) and Normalized Correct Observation Ratio% (NCOR%) [2] in order to establish which had the maximum value. For qualitative analysis of the clinical image, radiologists examined X- ray images of patients using T1 and comparing it with T2. Results We noticed that T2 can entail a lower ESD: −68% and a lower effective dose: −65%. In relation to qualitative analysis, carried out by radiologists, there was no significant preference of one technique over another. T2 proved to be the best also in TO.20 analysis performed on a phantom: COR% is comparable: T2 (36%), T1 (39%) and NCOR% is better: T2 (6.2%), T1 (3.9%). Conclusions By optimising acquisition parameters in chest acquisition of pediatric patients, using filtration 0.1 mmCu + 1mmAl, removing grid and setting lower kV, it is possible to lower radiation dose preserving image quality.

X-ray image global enhancement algorithm in medical image classification

The current global enhancement algorithm for medical X-ray image has problems of poor de-noising and enhancement effect and low reduction of the enhanced medical X-ray image. To address the problems, a global enhancement algorithm for X-ray image in medical image classification is proposed in this paper. The medical X-ray image is gray scaled, which provides the basis for the further processing of the image. The noise in medical X-ray image is removed by using multi-wavelet transform to improve the enhancement effect of the method. With the curve-let domain the medical X-ray image is enhanced, the reduction degree of medical X-ray image is improved and the global enhancement of the medical X-ray image is completed. Experimental results show that the de-noising effect of the proposed method is effective, the enhanced medical X ray image is better, and the reduction degree of medical X-ray image is high.

High-precision compton imaging of 4.4 MeV prompt gamma-ray toward an on-line monitor for proton therapy

Proton therapy is a widely used and effective treatment for cancer. A high-dose concentration of proton beam reduces damage to normal tissues. However, it also requires a high accuracy of irradiation. PET is generally used to verify the proton range after irradiation, but, the distributions of positrons and the energy deposited by protons are not similar to each other. Recently, prompt gamma-ray imaging has attracted attention as a new, online imaging technique. In particular, 4.4 MeV gamma rays emitted from 12C* is one of the best probes to monitor the proton dose, however imaging techniques are far from established. We have developed a novel, 3-D position sensitive Compton camera based on Ce:GAGG scintillators coupled with multi-pixel photon counter (MPPC) arrays, thus making it optimized for imaging in the 1–10 MeV range. The angular resolution is 5 degrees (FWHM) at 4.4 MeV. We have established various methods to discriminate multiple-Compton and escape events, both of which can be critical backgrounds for precise imaging of prompt gamma rays. By irradiating a 70 MeV proton beam on the PMMA phantom, we demonstrated that 4.4 MeV gamma ray image is sharply concentrated on the Bragg peak, as was expected from the PHITS simulation.

A CdTe pixel detector–CMOS preamplifier for room temperature high sensitivity and energy resolution X and [formula omitted] ray spectroscopic imaging

X and γ ray imaging devices with spectroscopic capabilities are strongly demanded in industrial, medical and scientific applications. CdTe detectors with Schottky contacts are very interesting due to their high absorption coefficient and the low leakage current of the reverse-biased rectifying junction even at room temperature. A CdTe detector with a pixel size of 0.75 mm × 0.75 mm has been coupled to SIRIO, a research-grade charge sensitive preamplifier with 1.2 electrons r.m.s. intrinsic noise. The system has been characterized at +20 °C for X and γ ray spectroscopy with a 241Am source. An intrinsic energy resolution of 326 eV FWHM has been measured and spectral line widths from 337 eV FWHM at 2.7 keV to 843 eV FWHM at 59.54 keV have been recorded. The linearity error of the spectrometer has been measured to be within ±0.1% in the 2.7 keV–59 keV energy range. Effects of escaping photons and fluorescences have been resolved and identified. The line widening sources and their effect on Fano factor determination have been discussed.

Optimization of the Synthesis and Physical Characterization of Praseodymium-Doped Type III KGd(PO3)4 Nanocrystals.

Scintillator materials are used as detectors in the ray imaging techniques for medical diagnosis. Because the ideal medical scintillator material does not exist, many efforts are being made to find new materials that satisfy a greater number of properties. Here, the synthesis conditions of Pr:KGd(PO3)4 nanocrystals by the modified Pechini method are optimized to obtain a single crystalline phase of those that form the polymorphism of KGd(PO3)4. The interest lies in the type III phase because less quenching by Pr3+ concentration is expected. By performing transmittance measurements and because of the wide transparency window of the type III KGd(PO3)4 host, the 3H4 → 5d1 absorption transition of Pr3+ has been observed in the vacuum ultraviolet spectral range. After creating electron–hole pairs in the host due to the excitation of the material by X-ray radiation, the bands corresponding to the 5d1 → 3H4, 3H5, 3H6 and 5d1 → 3F3, 3F4, 1G4 transitions of Pr3+ have been observed in the near-visible spectral range, being these 5d → 4f transitions interesting for scintillation applications. Therefore, the type III Pr:KGd(PO3)4 nanocrystals allow the conversion from high-energy radiation to visible or near-visible light.

Analytic simulator and image generator of multiple-scattering Compton camera for prompt gamma ray imaging.

For prompt gamma ray imaging for biomedical applications and environmental radiation monitoring, we propose herein a multiple-scattering Compton camera (MSCC). MSCC consists of three or more semiconductor layers with good energy resolution, and has potential for simultaneous detection and differentiation of multiple radio-isotopes based on the measured energies, as well as three-dimensional (3D) imaging of the radio-isotope distribution. In this study, we developed an analytic simulator and a 3D image generator for a MSCC, including the physical models of the radiation source emission and detection processes that can be utilized for geometry and performance prediction prior to the construction of a real system. The analytic simulator for a MSCC records coincidence detections of successive interactions in multiple detector layers. In the successive interaction processes, the emission direction of the incident gamma ray, the scattering angle, and the changed traveling path after the Compton scattering interaction in each detector, were determined by a conical surface uniform random number generator (RNG), and by a Klein-Nishina RNG. The 3D image generator has two functions: the recovery of the initial source energy spectrum and the 3D spatial distribution of the source. We evaluated the analytic simulator and image generator with two different energetic point radiation sources (Cs-137 and Co-60) and with an MSCC comprising three detector layers. The recovered initial energies of the incident radiations were well differentiated from the generated MSCC events. Correspondingly, we could obtain a multi-tracer image that combined the two differentiated images. The developed analytic simulator in this study emulated the randomness of the detection process of a multiple-scattering Compton camera, including the inherent degradation factors of the detectors, such as the limited spatial and energy resolutions. The Doppler-broadening effect owing to the momentum distribution of electrons in Compton scattering was not considered in the detection process because most interested isotopes for biomedical and environmental applications have high energies that are less sensitive to Doppler broadening. The analytic simulator and image generator for MSCC can be utilized to determine the optimal geometrical parameters, such as the distances between detectors and detector size, thus affecting the imaging performance of the Compton camera prior to the development of a real system.

X-ray analysis of foramen rotundum for preliminary diagnosis of fossa pterygopalatina lesions

Objectives: Fossa pterygopalatina is located posterior to maxillary sinus, anterior to pterygoid plates and inferior to greater sphenoid wing. Tumors that arise in fossa pterygopalatina are usually asymptomatic and often discovered at late stage. Because of its deep and relative inaccessible location, clinical examination of fossa pterygopalatina is difficult. Aplastic or nonvisible foramen rotundum may give an early indication for the regional tumors. Methods: In the present study, foramen rotundum was visualized as a round structure with prominent sclerotic margins located near ethmoid cells, maxillary sinus or orbital cavity in X ray images. X-rays (radiographs) of 17 dry skulls and 7 half dry skulls were performed with Phillips Digital Diagnost X-Ray device. All dry skulls were positioned similar to Caldwell’s view. We have designed a fixation apparatus to optimize the positioning of dry skulls and half skulls. After fixation of the skulls with the apparatus, the X-ray beam centered about 3–4 cm below the external occipital protuberance with an angle of 15 degrees to the chantomeatal line. Each radiologic image was examined for the location of foramen rotundum in relation with orbital cavity, ethmoidal cells and maxillary sinuses. We described the characteristic of foramen rotundum with count and percent values. Results: In the present study, 41 foramina rotunda were analyzed. Out of 41 foramina rotunda, twenty were right-sided, twenty one were left-sided. Of the 20 right-sided foramina rotunda, 19 were visible on X-ray images. On the other side 18 of 21 leftsided foramina rotunda were apparent. 14 of 19 visible right-sided foramina rotunda were identified in the orbital cavity (73.68%). Three of them were identified in ethmoidal cells, and two in the maxillary sinus. 11 of 18 visible left-sided foramina rotunda were identified in the orbital cavity (61.11%). Two of these were found in ethmoidal cells, eight in the maxillary sinus. Out of 17 dry skulls, one had bilateral nonvisible foramina rotunda. Conclusion: Foramen rotundum must be taken into consideration in evaluation of routine X-rays to prevent misdiagnosis of the patients with persistent non-specific symptoms.

Calibration of AGILE-GRID with On-ground Data and Monte Carlo Simulations

AGILE is a mission of the Italian Space Agency (ASI) Scientific Program dedicated to γ-ray astrophysics, and has operated in a low Earth orbit since 2007 April 23. It is designed to be a very light and compact instrument, capable of simultaneously detecting and imaging photons in the 18–60 keV X-ray energy band and in the 30 MeV–50 GeV γ-ray energy range with a good angular resolution (≈1◦ @ 1 GeV). The core of the instrument is the Silicon Tracker, supplemented by a CsI calorimeter and an AntiCoincidence system, which form the Gamma Ray Imaging Detector (GRID). Before launch, the GRID needed on-ground calibration with a tagged γ-ray beam to estimate its performance and validate the Monte Carlo simulation. The GRID was calibrated using a tagged γ-ray beam with energy up to 500 MeV at the Beam Test Facilities at the INFN Laboratori Nazionali di Frascati. These data are used to validate a GEANT 3-based simulation by comparing the data and the Monte Carlo simulation by measuring the angular and energy resolutions. The GRID angular and energy resolutions obtained using the beam agree well with the Monte Carlo simulation. Therefore the simulation, can be used to simulate the same performance on-flight with high reliability.

Identification of activity peaks in time-tagged data with a scan-statistics driven clustering method and its application to gamma-ray data samples

Context.The investigation of activity periods in time-tagged data samples is a topic of great interest. Among astrophysical samples, gamma-ray sources are widely studied, due to the huge quasi-continuum data set available today fromFermi-LAT (FermiLarge Area Telescope) and the AGILE-GRID (Astro Rivelatore Gamma a Immagini LEggero-Gamma Ray Imaging Detector)Aims.To reveal flaring episodes of a given gamma-ray source, researchers make use of binned light curves. This method suffers from several drawbacks: the results depend on time-binning and the identification of activity periods is difficult for bins with a low signal-to-noise ratio. A different approach is investigated in this paper.Methods.We developed a general temporal-unbinned method to identify flaring periods in time-tagged data and discriminate statistically significant flares. We propose an event clustering method in one dimension to identify flaring episodes, and scan statistics to evaluate the flare significance within the whole data sample. This is a photometric algorithm. The comparison of the photometric results (e.g. photometric flux, gamma-ray spatial distribution) for the identified peaks with the standard likelihood analysis for the same period is mandatory to establish if source confusion is spoiling results.Results.The procedure can be applied to reveal flares in any time-tagged data sample. The result of the proposed method is similar to a photometric light curve, but peaks are resolved, they are statistically significant within the whole period of investigation, and peak detection capability does not suffer time-binning related issues. The study of the gamma ray activity of 3C 454.3 and of the fast variability of the Crab Nebula are shown as examples. The method can be applied for gamma-ray sources of known celestial position, for example, sources taken from a catalogue. Furthermore the method can be used when it is necessary to assess the statistical significance within the whole period of investigation of a flare from an unknown gamma-ray source. Extensive results based on this analysis method for some astrophysical problems are the subject of a forthcoming paper.

Interpretation of runaway electron synchrotron and bremsstrahlung images

The crescent spot shape observed in DIII-D runaway electron synchrotron radiation images is shown to result from the high degree of anisotropy in the emitted radiation, the finite spectral range of the camera and the distribution of runaways. The finite spectral camera range is found to be particularly important, as the radiation from the high-field side can be stronger by a factor 106 than the radiation from the low-field side in DIII-D. By combining a kinetic model of the runaway dynamics with a synthetic synchrotron diagnostic we see that physical processes not described by the kinetic model (such as radial transport) are likely to be limiting the energy of the runaways. We show that a population of runaways with lower dominant energies and larger pitch-angles than those predicted by the kinetic model provide a better match to the synchrotron measurements. Using a new synthetic bremsstrahlung diagnostic we also simulate the view of the gamma ray imager diagnostic used at DIII-D to resolve the spatial distribution of runaway-generated bremsstrahlung.

Detection of Osteoporosis Using Fractal Method Based on Fourier Analysis of Hand Bone Image

This study applies the method of fractal-based 2D Fourier transform to determine an image of osteoporosis or normal based on the dimensions and intercept of the X ray image hand bones. The first step is to create a program to determine the dimensions and the intercept of image. It is determined by using a fractal method based on 2D Fourier transform. Testing the success of the program is done by input X ray image of the hand bones. The result shows that the program testing 2D Fourier transforms can be applied to determine the dimensions and intercept of the hand bones image. The classification of the normal and osteoporosis images is based on the dimensions and intercept values. Normal image has dimension <1.4 and intercept value > 34, osteoporosis image has dimension >1.4 and intercept value <34. Dimensional of osteoporosis image have higher than normal image but the normal image density is higher than the osteoporosis image. Classification results quite effectively to help diagnose osteoporosis.

Precision imaging of 4.4 MeV gamma rays using a 3-D position sensitive Compton camera

Imaging of nuclear gamma-ray lines in the 1–10 MeV range is far from being established in both medical and physical applications. In proton therapy, 4.4 MeV gamma rays are emitted from the excited nucleus of either 12C* or 11B* and are considered good indicators of dose delivery and/or range verification. Further, in gamma-ray astronomy, 4.4 MeV gamma rays are produced by cosmic ray interactions in the interstellar medium, and can thus be used to probe nucleothynthesis in the universe. In this paper, we present a high-precision image of 4.4 MeV gamma rays taken by newly developed 3-D position sensitive Compton camera (3D-PSCC). To mimic the situation in proton therapy, we first irradiated water, PMMA and Ca(OH)2 with a 70 MeV proton beam, then we identified various nuclear lines with the HPGe detector. The 4.4 MeV gamma rays constitute a broad peak, including single and double escape peaks. Thus, by setting an energy window of 3D-PSCC from 3 to 5 MeV, we show that a gamma ray image sharply concentrates near the Bragg peak, as expected from the minimum energy threshold and sharp peak profile in the cross section of 12C(p,p)12C*.

Feasibility study of single photon emission coupled tomography imaging technique based on prompt gamma ray during antiproton therapy using boron particle

In this study, we proposed an absorbed-dose monitoring technique using prompt gamma rays emitted from the reaction between an antiproton and a boron particle, and demonstrated the greater physical effect of the antiproton boron fusion therapy in comparison with proton beam using Monte Carlo simulation. The physical effect of the treatment, which was 3.5 times greater, was confirmed from the antiproton beam irradiation compared to the proton beam irradiation. Moreover, the prompt gamma ray image is acquired successfully during antiproton irradiation to boron regions. The results show the application feasibility of absorbed dose monitoring technique proposed in our study.

Detection of a casting defect tracked by deep convolution neural network

In order to relieve the problem of a false and missed detection of casting defects in X-ray detection, a robust detection method based on vision attention mechanism and deep learning of feature map is proposed. The ray images are used as input sequence, the false detection is eliminated by the intra-frame attention strategy, and the missed detection is excluded by the inter-frame deep convolution neural network (DCNN) strategy. In the intra-frame detection stage, the center-peripheral difference method is proposed to simulate the difference operation of biological vision; the suspicious defect area is directly detected according to the gradient threshold in this stage. In the inter-frame learning stage, the convolution neural network is established based on deep learning strategy to extract defect feature from a suspicious defect area; a deep learning feature vector is obtained in this stage. The similarity degree of the suspicious defect area is computed by a feature vector; a casting defect is tracked by the similarity matching of the suspicious defect in continuous frames; then, the false defects (such as noise) is excluded after defect tracking. The experimental results show that the false rate and missed rate for detection of casting defects are less than 4%, and the accuracy of the defect detection is more than 96%, which proves the robustness of the proposed method.

Counting loxodromics for hyperbolic actions

Let G ⤻ X be a non-elementary action by isometries of a hyperbolic group G on a (not necessarily proper) hyperbolic metric space X. We show that the set of elements of G which act as loxodromic isometries of X has density one in the word metric on G. That is, for any finite generating set of G, the proportion of elements in G of word length at most n, which are X–loxodromics, approaches 1 as n → ∞ . We also establish several results about the behavior in X of the images of typical geodesic rays in G; for example, we prove that they make linear progress in X and converge to the Gromov boundary ∂ X . We discuss various applications, in particular to mapping class groups, Out ( F N ) , and right–angled Artin groups.

12.1: Invited Paper: The Creation of Non‐paraxial Optics and Its Application in 3D, VR &amp; AR

This paper introduces a different imaging method from Gaussian optics called non‐paraxial optics, which is a study of non‐paraxial ray imaging. When the viewer’s eye (left eye or right eye) is not aligned with the symmetry axis, the distance from the eye to the axis is called eccentricity. It is found that the magnified virtual image traverses perpendicularly to the axis of symmetry without losing the integrity of the image. This imaging law is similar to Gaussian optics, except that the focus needs to be redefined. Gaussian optics can be considered non‐paraxial optics when eccentricity equals to zero.After years of research and experience, the author has successfully prototyped decentered pairs of lenses using non‐paraxial optical theory. These lenses magnify the left and right eye images in the virtual image space and shift them toward the axis of symmetry. The non‐destructive virtual images coincide completely so that they form a perfect 3D image. This stereo image maintains its brightness, precision, grayscale, contrast, and color saturation. It also has no crosstalk or flicker. It has the best image quality among the most popular products on the market today.3D is the foundation of VR and AR. Only when 3D receives the ideal development would VR and AR progress. The stereoscopic view based on this theory can become a common 3D platform and can be applied in various fields. Not only does it meet the most demanding image quality requirements in the medical field, but it also fulfills people's pursuit of higher aesthetic art studies.

Evaluation of target coverage and margins adequacy during CyberKnife Lung Optimized Treatment.

Evaluation of target coverage and verification of safety margins, in motion management strategies implemented by Lung Optimized Treatment (LOT) module in CyberKnife system. Three fiducial-less motion management strategies provided by LOT can be selected according to tumor visibility in the X ray images acquired during treatment. In 2-view modality the tumor is visible in both X ray images and full motion tracking is performed. In 1-view modality the tumor is visible in a single X ray image, therefore, motion tracking is combined with an internal target volume (ITV)-based margin expansion. In 0-view modality the lesion is not visible, consequently the treatment relies entirely on an ITV-based approach. Data from 30 patients treated in 2-view modality were selected providing information on the three-dimensional tumor motion in correspondence to each X ray image. Treatments in 1-view and 0-view modalities were simulated by processing log files and planning volumes. Planning target volume (PTV) margins were defined according to the tracking modality: end-exhale clinical target volume (CTV)+3mm in 2-view and ITV+5mm in 0-view. In the 1-view scenario, the ITV encompasses only tumor motion along the non-visible direction. Then, non-uniform ITV to PTV margins were applied: 3mm and 5mm in the visible and non-visible direction, respectively. We defined the coverage of each voxel of the CTV as the percentage of X ray images where such voxel was included in the PTV. In 2-view modality coverage was calculated as the intersection between the CTV centred on the imaged target position and the PTV centred on the predicted target position, as recorded in log files. In 1-view modality, coverage was calculated as the intersection between the CTV centred on the imaged target position and the PTV centred on the projected predictor data. In 0-view modality coverage was calculated as the intersection between the CTV centred on the imaged target position and the non-moving PTV. Similar to dose-volume histogram, CTV coverage-volume histograms (defined as CVH) were derived for each patient and treatment modality. The geometric coverages of the 90% and 95% of CTV volume (C90, C95, respectively) were evaluated. Patient-specific optimal margins (ensuring C95≥95%) were computed retrospectively. The median±interquartile-rage of C90 and C95 for upper lobe lesions was 99.1±0.6% and 99.0±3.1%, whereas they were 98.9±4.2% and 97.8±7.5% for lower and middle lobe tumors. In 2-view, 1-view and 0-view modality, adopted margins ensured C95≥95% in 70%, 85% and 63% of cases and C95≥90% in 90%, 88% and 83% of cases, respectively. In 2-view, 1-view and 0-view a reduction in margins still ensured C95≥95% in 33%, 78% and 59% of cases, respectively. CTV coverage analysis provided an a-posteriori evaluation of the treatment geometric accuracy and allowed a quantitative verification of the adequacy of the PTV margins applied in CyberKnife LOT treatments offering guidance in the selection of CTV margins.