Journal of X-Ray Science and Technology - Volume 23, issue 2

Authors: Ingleby, Harry | Lippuner, Jonas | Rickey, Daniel W. | Li, Yue | Elbakri, Idris

Article Type: Research Article

Abstract: PURPOSE: To develop a fast patient-specific analytical estimator of first-order Compton and Rayleigh scatter in cone-beam computed tomography, implemented using graphics processing units. METHODS: The authors developed an analytical estimator for first-order Compton and Rayleigh scatter in a cone-beam computed tomography geometry. The estimator was coded using NVIDIA's CUDA environment for execution on an NVIDIA graphics processing unit. Performance of the analytical estimator was validated by comparison with high-count Monte Carlo simulations for two …different numerical phantoms. Monoenergetic analytical simulations were compared with monoenergetic and polyenergetic Monte Carlo simulations. Analytical and Monte Carlo scatter estimates were compared both qualitatively, from visual inspection of images and profiles, and quantitatively, using a scaled root-mean-square difference metric. Reconstruction of simulated cone-beam projection data of an anthropomorphic breast phantom illustrated the potential of this method as a component of a scatter correction algorithm. RESULTS: The monoenergetic analytical and Monte Carlo scatter estimates showed very good agreement. The monoenergetic analytical estimates showed good agreement for Compton single scatter and reasonable agreement for Rayleigh single scatter when compared with polyenergetic Monte Carlo estimates. For a voxelized phantom with dimensions 128 × 128 × 128 voxels and a detector with 256 × 256 pixels, the analytical estimator required 669 seconds for a single projection, using a single NVIDIA 9800 GX2 video card. Accounting for first order scatter in cone-beam image reconstruction improves the contrast to noise ratio of the reconstructed images. CONCLUSION: The analytical scatter estimator, implemented using graphics processing units, provides rapid and accurate estimates of single scatter and with further acceleration and a method to account for multiple scatter may be useful for practical scatter correction schemes. Show more

Keywords: Scatter estimation, compton scatter, rayleigh scatter, graphics processing units

DOI: 10.3233/XST-150475

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 119-133, 2015

Authors: Pontoriero, Antonio | Amato, Ernesto | Iatí, Giuseppe | De Renzis, Costantino | Pergolizzi, Stefano

Article Type: Research Article

Abstract: OBJECTIVE: Purpose of this work was to study the dose perturbation within the target volume of a external MV radiation therapy when using metal fiducials. METHODS: We developed a Monte Carlo simulation in Geant4 of a cylindrical fiducial made either of gold or of steel and simulated the photon irradiation beam originating from a medical Linac operating at 6, 10 or 15 MV. For each energy, two different irradiation schemes were simulated: a single …5 × 5-cm square field in the -x direction, and five 5 × 5-cm fields at 0°, 80°, 165°, 195° and 280°. RESULTS: In a single beam irradiation scheme, we observed a dose reduction behind fiducials varying from −20% for gold at 6 MV to −5% for steel at 15 MV, and a dose increment in front of the fiducial ranging from +33% for gold at 15 MV to +10% for steel at 6 MV. When five beams were employed, a dose increment ranging from +28% to +46% has been found around gold. Around a steel fiducial, an average increment of +17% was found, irrespective of the photon energy. CONCLUSIONS: When using a single beam, the decrement of dose behind both steel and gold markers increases with the photon energy. This effect vanishes when a multifield treatment is delivered; in this instance there is a dose increment around fiducials, according to both fiducial material and photon energy, with lower values for steel and 6 MV. This energy represents the best choice when fiducial markers are present inside the irradiated volume. Show more

Keywords: Radiotherapy, Monte Carlo, dose, fiducial marker x-rays

DOI: 10.3233/XST-150476

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 135-140, 2015

Authors: Sun, Tianxi | MacDonald, C.A.

Article Type: Research Article

Abstract: A monochromatic X-ray imaging setup based on a combination of a doubly curved crystal and a polycapillary focusing X-ray lens was designed. In this setup, the bent crystal optic was used not only to monochromatize but also to focus the divergent X-ray beam from a conventional X-ray source to form a monochromatic X-ray focal spot with a size of 426 × 467 μm^{2} at 17.5 keV. The beam expanding from this focal point was …focused by the polycapillary optic to obtain a focal spot which was then used as the monochromatic X-ray imaging virtual source. The output focal spot size of the focusing polycapillary optic at 17.5 keV was 97 μm. Compared with the beam expansion after the focal spot of the bent crystal optic, the beam expansion after the focal spot of the focusing polycapillary optic was relatively large. This was helpful for magnifying the X-ray image of the sample. The focused beam was helpful to decrease the exposure time for imaging small samples. Show more

Keywords: Monochromatic X-ray imaging, doubly curved crystal, polycapillary X-ray lens

DOI: 10.3233/XST-150477

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 141-146, 2015

Authors: Wang, Guohe | Zhang, Bin | Ding, Yichen | He, Yun | Chen, Jingsong | Lu, Yanye | Jiang, Xiaoyun | Shi, Junwei | Bai, Jing | Ren, Qiushi | Li, Changhui

Article Type: Research Article

Abstract: Nowadays multi-modality imaging has gained great interest in biology research by offering complementary information. In this paper, a modularly designed fluorescence molecular tomography (FMT) system has been developed, which can be not only used as a standalone imaging device, but also feasibly integrated with other imaging modalities, such as X-ray computed tomography (X-CT), single photon emission computed tomography (SPECT) and positron emission tomography (PET), to perform multi-modality imaging in a sequential manner. …The system rotates the CCD camera and the excitation light source in the vertical plane, while the animal is stationed on a horizontally moveable transparent animal holder at its natural prone position. FMT and other imaging modalities are co-registered automatically. Phantom and animal experiments have been carried out to demonstrate the performance of the system. The accurate results show that this innovative flexible FMT system has a great potential to be a powerful tool for the study of small animal disease models. Show more

Keywords: Fluorescence molecular tomography, multi-modality imaging, fluorescence imaging

DOI: 10.3233/XST-150478

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 147-156, 2015

Authors: Zhao, Shuang-Ren | Jiang, Dazong | Yang, Kevin | Yang, Kang

Article Type: Research Article

Abstract: The cone-beam reconstruction theory has been proposed by Kirillov in 1961, Tuy in 1983, Feldkamp in 1984, Smith in 1985, Pierre Grangeat in 1990. The Fourier slice theorem is proposed by Bracewell 1956, which leads to the Fourier image reconstruction method for parallel-beam geometry. The Fourier slice theorem is extended to fan-beam geometry by Zhao in 1993 and 1995. By combining the above mentioned cone-beam image reconstruction theory and the above mentioned Fourier slice theory of …fan-beam geometry, the Fourier slice theorem in cone-beam geometry is proposed by Zhao 1995 in short conference publication. This article offers the details of the derivation and implementation of this Fourier slice theorem for cone-beam geometry. Especially the problem of the reconstruction from Fourier domain has been overcome, which is that the value of in the origin of Fourier space is 0/0. The 0/0 type of limit is proper handled. As examples, the implementation results for the single circle and two perpendicular circle source orbits are shown. In the cone-beam reconstruction if a interpolation process is considered, the number of the calculations for the generalized Fourier slice theorem algorithm is O(N^4) , which is close to the filtered back-projection method, here N is the image size of 1-dimension. However the interpolation process can be avoid, in that case the number of the calculations is O(N^5) . Show more

Keywords: Fourier, slice theorem, projection, cone-beam, fan-beam, image reconstruction, CT, FBP

DOI: 10.3233/XST-150479

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 157-188, 2015

Authors: Wang, Shenghao | Han, Huajie | Gao, Kun | Wang, Zhili | Zhang, Can | Yang, Meng | Wu, Zhao | Wu, Ziyu

Article Type: Research Article

Abstract: X-ray phase-contrast imaging can provide greatly improved contrast over conventional absorption-based imaging for weakly absorbing samples, such as biological soft tissues and fibre composites. In this study, we introduced an easy and fast way to develop a user-friendly software platform dedicated to the new grating-based X-ray phase-contrast imaging setup at the National Synchrotron Radiation Laboratory of the University of Science and Technology of China. The control of 21 motorized stages, of a piezoelectric stage and of …an X-ray tube are achieved with this software, it also covers image acquisition with a flat panel detector for automatic phase stepping scan. Moreover, a data post-processing module for signals retrieval and other custom features are in principle available. With a seamless integration of all the necessary functions in one software package, this platform greatly facilitate users' activities during experimental runs with this grating based X-ray phase contrast imaging setup. Show more

Keywords: X-ray imaging, phase-contrast, LabVIEW, instrument control, image acquisition, image processing, software platform

DOI: 10.3233/XST-150480

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 189-199, 2015

Authors: Montagner, Florian | Kaftandjian, Valérie | Farlay, Delphine | Brau, Daniel | Boivin, Georges | Follet, Hélène

Article Type: Research Article

Abstract: In order to simplify bone mineralization measurements, a system using radiographic films has been updated with a digital detector. The objective of this paper was to validate this new device. Technologies and physical phenomena involved in both systems (radiographic films and digital detector) are different. The methodology used to compare the two systems was based on image quality and assessed on two main parameters: contrast to noise ratio and spatial resolution. Results showed that the contrast …to noise ratio was similar between the two systems, provided that acquisition parameters were optimized. With regard to spatial resolution, a magnification factor of at least 4 or more was required to achieve the same resolution as films. A final validation was also shown on a real image of a bone sample. The results showed that both systems have similar image quality performances, and the system using digital detector has several advantages (easier to use than films, no consumables and faster acquisition time). Show more

Keywords: Mineralization of bone, quantitative microradiography, digital detector, spatial resolution, contrast to noise ratio

DOI: 10.3233/XST-150481

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 201-211, 2015

Authors: Kong, Huihua | Yu, Hengyong

Article Type: Research Article

Abstract: To develop low-cost and low-dose computed tomography (CT) scanners for developing countries, recently a parallel translational computed tomography (PTCT) is proposed, and the source and detector are translated oppositely with respect to the imaging object without a slip-ring. In this paper, we develop an analytic filtered-backprojection (FBP)-type reconstruction algorithm for two dimensional (2D) fan-beam PTCT and extend it to three dimensional (3D) cone-beam geometry in a Feldkamp-type framework. Particularly, a weighting function …is constructed to deal with data redundancy for multiple translations PTCT to eliminate image artifacts. Extensive numerical simulations are performed to validate and evaluate the proposed analytic reconstruction algorithms, and the results confirm their correctness and merits. Show more

Keywords: Parallel translational computed tomography, analytic reconstruction, filtered backprojection, feldkamp-type extension

DOI: 10.3233/XST-150482

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 213-228, 2015

Authors: Li, Ming | Zheng, Jian | Zhang, Tao | Guan, Yihui | Xu, Pin | Sun, Mingshan

Article Type: Research Article

Abstract: In computed tomography (CT), metal objects in the scanning filed are accompanied by physical phenomenon that causes projections to be inconsistent. These inconsistencies produce bright and dark shadows or streaks in analytically reconstructed images. Interpolation-based metal artifact reduction (MAR) algorithms usually replace the inconsistent projection data by estimating surrogate data based on the surrounding uncorrupted projections. In such cases, secondary artifacts will be generated when the data estimates are inaccurate. Therefore, better …projection estimation is critical. This paper proposes an image post-processing strategy to create an intermediate image, named the prior image and better estimates of the surrogate data by forward projecting this prior image. The proposed method consists of three steps based on the forward projection MAR framework. First, metallic implants in the uncorrected images are segmented using a Markov random field model (MRF). Then a prior image is generated via an edge-preserving filter and a recovery procedure of the adjacent anatomical structures. Finally, the projection is completed via forward projecting this prior image and the corrected image is reconstructed by the filtered backprojection (FBP) method. Studies on both phantom and clinical data are carried out to verify the performance of the proposed method. The comparisons with other previous MAR algorithms demonstrate that the proposed MAR method performs better in metal artifact suppression and anatomical structure preservation. Show more

Keywords: Computed tomography, metal artifact reduction, secondary artifacts, prior image

DOI: 10.3233/XST-150483

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 229-241, 2015

Authors: Chen, Huei-Yung | Lu, Nan-Han | Huang, Yung-Hui | Chen, Tai-Been

Article Type: Research Article

Abstract: Positron emission tomography (PET) had been utilized to image gene therapy, estimate tumor growth, detect neural function of the brain, and diagnose disease. However, sinogram noise always results inaccurate PET images. The factorial design of experiment (DOE), a statistical method, was applied to investigate, correct and estimate the fraction of scattering of 2D sinogram in PET. The DOE was included as factors of angle views and scatter media with two levels designed. The PET sinogram after …scattering correction was then reconstructed by filtered back projection (FBP). Both Ge-68 uniform phantom and Jaszczak anthropomorphic torso phantom were applied to exam the performance of presented scattering correction algorithm. The signal-to-noise ratio (SNR), standard deviation (STD) of background, and full width at half maximum (FWHM), and uniformity test were applied to validate the performance of presented method. The proposed method provides a narrower FWHM, smaller STD of the background, higher SNR and better uniformity than those of original protocols. This method should be tested for accuracy and feasibility with three-dimensional phantoms or real animal studies and consideration effects of cross-talk between slices in future work. Show more

Keywords: Factorial design of experiment, PET, scattering correction algorithm

DOI: 10.3233/XST-150484

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 243-251, 2015

Authors: Yang, Jian | Fan, Jingfan | Fu, Tianyu | Ai, Danni | Zhu, Jianjun | Li, Qin | Wang, Yongtian

Article Type: Research Article

Abstract: This study proposes a novel hierarchical pyramid strategy for 3D registration of multimodality medical images. The surfaces of the source and target volume data are first extracted, and the surface point clouds are then aligned roughly using convex hull matching. The convex hull matching registration procedure could align images with large-scale transformations. The original images are divided into blocks and the corresponding blocks in the two images are registered by affine and non-rigid registration procedures. The …sub-blocks are iteratively smoothed by the Gaussian kernel with different sizes during the registration procedure. The registration result of the large kernel is taken as the input of the small kernel registration. The fine registration of the two volume data sets is achieved by iteratively increasing the number of blocks, in which increase in similarity measure is taken as a criterion for acceptation of each iteration level. Results demonstrate the effectiveness and robustness of the proposed method in registering the multiple modalities of medical images. Show more

Keywords: Convex hull, multimodality image, registration

DOI: 10.3233/XST-150485

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 253-265, 2015

Authors: Agah, K. Mikaili | Ghoranneviss, M. | Elahi, A. Salar

Article Type: Research Article

Abstract: Determinations of plasma parameters as well as the Magnetohydrodynamics (MHD) activity, energetic electrons energy and energy confinement time are essential for future fusion reactors experiments and optimized operation. Also some of the plasma information can be deduced from these parameters, such as plasma equilibrium, stability, and MHD instabilities. In this contribution we investigated the relation between energetic electrons, hard x-ray emission and MHD activity in the IR-T1 Tokamak. For this purpose we …used the magnetic diagnostics and a hard x-ray spectroscopy in IR-T1 tokamak. A hard x-ray emission is produced by collision of the runaway electrons with the plasma particles or limiters. The mean energy was calculated from the slope of the energy spectrum of hard x-ray photons. Show more

Keywords: Tokamak, energetic electrons

DOI: 10.3233/XST-150486

Citation: Journal of X-Ray Science and Technology, vol. 23, no. 2, pp. 267-274, 2015