Journal of X-Ray Science and Technology - Volume 19, issue 1

Authors: Li, Zongjian | Zeng, Li | Zou, Xiaobing | Xiang, Caibing

Article Type: Research Article

Abstract: As an advanced nondestructive testing (NDT) technology, industrial computed tomography (ICT) has been widely applied to diversified areas. In modern industry, ICT is especially useful for analyzing inner defects of complex and close work pieces. The common defects of work pieces include gas cavities, slag inclusions, cracks and shrinking cavities. Only cracks are often caused by fatigue usage. Precisely extracting a crack is important to estimate the remaining secure service time of the work piece. This …paper presents a crack surface extraction method of ICT volume data based on finite plane integral transform (FPIT) and planelet. FPIT and planelet, as new methods of multiscale geometric analysis (MGA), have distinct discrimination for different plane singularities. Within the paper, firstly the definitions of FPIT and planelet are introduced. Secondly, after analyzing the components and relationship of planelet at monoscale, a fast performance of planelet transform is designed. Thirdly, the steps of the proposed crack surface extraction method are described. In numeric experiment, compared with the method of 3D facet model, C-V model and 3D wavelet respectively, the proposed method can extract the crack surface full and continuously, which,is robust to noise. Show more

Keywords: Crack surface extraction, planelet, finite plane integral transform (FPIT), volume data, industrial computed tomography (ICT)

DOI: 10.3233/XST-2010-0275

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 1-12, 2011

Authors: Han, I. | Demir, L.

Article Type: Research Article

Abstract: L_{3} -subshell alignment of Th and U ionized by 59.5 keV photons has been investigated by evaluating the angular dependence of L_{i} (i=l, α, η, β and γ) X-ray lines. The angular dependence measurements were performed by measuring the fluorescence cross section, σ_{Li} (i=1, η, α, β and γ) and σ_{Ll} /σ_{Lγ} , σ_{Lη} /σ_{Lγ } , σ_{Lα} …/σ_{Lγ } and σ_{Lβ} /σ_{Lγ} ratios at different angles. It was observed from the measurements that L_{i} (i=l and α) X rays for the L_{3} -subshell depended on the emission angle and had an anisotropic spatial distribution. On the other hand, there was no dependence of emission angle and any significant anisotropy for other L X rays. The both Ll and Lα X-rays originate from the filling of vacancies in states L_{3} -subshell with J =3/2. The results of measurements indicate that the L_{3} -subshell vacancy states with J = 3/2 are aligned, whereas L_{1} , and L_{2} vacancy states with J =1/2 are non-aligned. Integral cross-sections for the L_{i} (i=l, η, α, β and γ) X-rays and L subshell fluorescence yields ω_{i} (i= 1, 2 and 3) were also determined and results were compared with theoretically calculated values and results of others and fairly good correspondence was observed. Show more

Keywords: Angular dependence, angular distribution, cross section, alignment, fluorescence yields

DOI: 10.3233/XST-2010-0276

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 13-21, 2011

Authors: Yang, Wanneng | Xu, Xiaochun | Bi, Kun | Zeng, Shaoqun | Liu, Qian | Chen, Shangbin

Article Type: Research Article

Abstract: The real-time imaging is important in automatic successive inspection with micro-computerized tomography (micro-CT). Generally, the size of the detector is chosen according to the most probable size of the measured object to acquire all the projection data. Given enough imaging area and imaging resolution of X-ray detector, the detector is larger than specimen projection area, which results in redundant data in the Sinogram. The process of real-time micro-CT is computation-intensive because of the large amounts of …source and destination data. The speed of the reconstruction algorithm can't always meet the requirements of real-time applications. A preprocessing method called adaptive region of interest (AROI), which detects the object's boundaries automatically to focus the active Sinogram regions, is introduced into the analytical reconstruction algorithm in this paper. The AROI method reduces the volume of the reconstructing data and thus directly accelerates the reconstruction process. It has been further shown that image quality is not compromised when applying AROI, while the reconstruction speed is increased as the square of the ratio of the sizes of the detector and the specimen slice. In practice, the conch reconstruction experiment indicated that the process is accelerated by 5.2 times with AROI and the imaging quality is not degraded. Therefore, the AROI method improves the speed of analytical micro-CT reconstruction significantly. Show more

Keywords: Adaptive region of interest (AROI), Analytical micro-computerized tomography, Filter backprojection (FBP) algorithm, Feldkamp-type (FDK) algorithm

DOI: 10.3233/XST-2010-0274

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 23-33, 2011

Authors: Alpuche Aviles, Jorge E. | Pistorius, Stephen | Gordon, Richard | Elbakri, Idris A.

Article Type: Research Article

Abstract: This work presents a first generation incoherent scatter CT (ISCT) hybrid (analytic-iterative) reconstruction algorithm for accurate ρ_{e} imaging of objects with clinically relevant sizes. The algorithm reconstructs quantitative images of ρ_{e} within a few iterations, avoiding the challenges of optimization based reconstruction algorithms while addressing the limitations of current analytical algorithms. A 4π detector is conceptualized in order to address the issue of directional dependency and is …then replaced with a ring of detectors which detect a constant fraction of the scattered photons. The ISCT algorithm corrects for the attenuation of photons using a limited number of iterations and filtered back projection (FBP) for image reconstruction. This results in a hybrid reconstruction algorithm that was tested with sinograms generated by Monte Carlo (MC) and analytical (AN) simulations. Results show that the ISCT algorithm is weakly dependent on the ρ _{e} initial estimate. Simulation results show that the proposed algorithm reconstruct ρ _{e} images with a mean error of −1% ± 3% for the AN model and from −6% to −8% for the MC model. Finally, the algorithm is capable of reconstructing qualitatively good images even in the presence of multiple scatter. The proposed algorithm would be suitable for in-vivo medical imaging as long as practical limitations can be addressed. Show more

Keywords: Compton scatter, computed tomography, scatter CT, scatter imaging, X-rays

DOI: 10.3233/XST-2010-0277

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 35-56, 2011

Authors: Zhao, Huijuan | Zhou, Xiaoqing | Fan, Ying | Gao, Feng

Article Type: Research Article

Abstract: A near infrared diffuse reflectance system for endoscopic measurement and an inverse algorithm for extracting optical properties of tubular tissues were developed in this paper. The measurement system worked in the frequency domain mode and a custom probe was employed for endoscopic detection of cervical cancer. Experiments for evaluating the measurement accuracy indicate that the model-to-data mismatch for the AC amplitude and phase lag is less than 3.7% and 6.7%, respectively. To facilitate the …extraction of the optical properties in tubular tissues and to minimize the influence of the initial guess on the reconstruction accuracy, a fast inverse Monte Carlo simulation algorithm with cluster analysis method was proposed. Simulation results showed that the relative errors of the absorption coefficient recovered using the proposed inverse algorithm are less than 5.8% and those of the sacttering coefficient are less than 10.2%. Endoscopic measurement on two tubular solid phantoms were also carried out to evaluate the system and the inversion scheme. The results demonstrated that less than 20% relative error can be achieved. Show more

Keywords: Near-infrared diffuse reflectance, frequency domain, inverse monte carlo simulation, endoscopic measurement

DOI: 10.3233/XST-2010-0278

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 57-68, 2011

Authors: Zhao, Shuangren | Yang, Kang | Jiang, Dazong | Yang, Xintie

Article Type: Research Article

Abstract: Truncated projections can arise from a detector with a limited field of view (LFOV). Truncation artifacts can be reduced through extrapolation methods; however the reconstructed images with extrapolation are often over-corrected or under-corrected. Recently, an iterative reconstruction-reprojection algorithm was developed, which incorporated extrapolation with iterative algorithm. It gave the possibility to better reduce truncation artifacts compared to using the extrapolation method alone. This article builds a theoretic foundation for the above iterative …reconstruction-reprojection algorithm. The theoretic foundation is suitable to parallel-beam, fan-beam and cone-beam computed tomography(CT). Two assumptions are summarized from the CT system. Then, a truncation-artifact-free solution for the problem of LFOV is derived from these assumptions. The solution contains a "local inverse" of matrix. The local inverse of a matrix is defined using the sub-matrix and its general inverse. The solution can be approximately implemented as the iterative reconstruction-reprojection algorithm which is just the algorithm mentioned above. Show more

Keywords: Artifact, truncation, image, reconstruction, projection, extrapolation, LFOV, tomography, local, inverse, CT, SPECT, PET

DOI: 10.3233/XST-2010-0279

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 69-90, 2011

Authors: Cai, Weixing | Ning, Ruola | Conover, David

Article Type: Research Article

Abstract: In flat-panel detector-based cone beam CT breast imaging (CBCTBI) systems, scattering is an important factor that degrades image quality. It is not practical to measure the scattering profiles of a breast for all view angles in a patient study, but it is possible to develop a method to estimate the scattering profiles based on information acquired from breast phantom studies. A new scattering correction method is proposed for clinical CBCTBI in this study. The scattering profiles …of three anthropomorphic uncompressed breast phantoms of different sizes were thoroughly investigated, and the results indicated that though phantom size differed, the scattering profiles were mainly determined by local breast diameters, which are the approximate diameters of coronal slices that are perpendicular to the nipple-to-chestwall direction. Thus for scattering correction purposes it is possible to establish a relationship between location breast diameters and local scattering profiles, namely the fitted smooth curves of scatter-to-primary ratios (SPR) and normalized scattered radiations (NSR). In clinical CBCTBI studies, after the local breast diameters are sampled and measured on projection images, the scattering image for every projection image can be generated based on the established relationship, and the projection images can be corrected using either the SPR based method or the NSR based method. Phantom studies and clinical studies showed that both the SPR and NSR methods are able to correct cupping artifacts and reduce reconstruction error. The SPR method does not increase tissue contrast or noise while the NSR method increases both. Show more

Keywords: Cone beam CT, scatter correction, breast imaging

DOI: 10.3233/XST-2010-0280

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 91-109, 2011

Authors: Dong, Di | Tian, Jie | Dai, Yakang | Yan, Guorui | Yang, Fei | Wu, Ping

Article Type: Research Article

Abstract: Various types of advanced imaging technologies have significantly improved the quality of medical care available to patients. Corresponding medical image reconstruction algorithms, especially 3D reconstruction, play an important role in disease diagnosis and treatment assessment. However, these increasing reconstruction methods are not implemented in a unified software framework, which brings along lots of disadvantages such as breaking connection of different modalities, lack of module reuse and inconvenience to method comparison. This …paper discusses reconstruction process from the viewpoint of data flow and implements a free, accelerated, extensible Unified Reconstruction Software Framework (URSF). The software framework is an abstract solution that supports multi-modal image reconstruction. The goal of this framework is to capture the common processing work flow for different modalities and different methods, make the development of reconstruction for new devices much easier, and implement a set of popular reconstruction algorithms, so that it is convenient for researchers to compare against. The overall design and certain key technologies are introduced in detail. Presented experiment examples and practical applications commendably demonstrate the validity of this framework. Show more

Keywords: Unified Reconstruction Software Framework, work flow, CT, freehand 3D ultrasound imaging, acceleration schemes

DOI: 10.3233/XST-2010-0281

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 111-126, 2011

Authors: Chen, Xiaodong | Li, Ming | Li, Yan | Wang, Yi | Yu, Daoyin

Article Type: Research Article

Abstract: A new approach for synthetic aperture focusing (SAF) to enhance both signal to noise ratio (SNR) and resolution in endoscopic ultrasonography is presented in this paper. The technique uses the rotation feature of single element transducer probe, and transmits and receives the echoes at different time and locations during the rotary scanning. Based on theoretical simulation, axial and lateral matched-filters are developed according to the coded and linear frequency modulated characteristics of the echoes to implement …axial and lateral compression. The effects of SNR and resolution enhancements by the new SAF approach are demonstrated by both Field II simulation and sample experiment. Data for 6 point targets are simulated and the performance of SAF is compared with those from conventional imaging method and Delay-and-Sum (DS) method. Pigskin samples are examined by a single element transducer at 8 MHz. The effects of sound speed errors and rotary scanning speed errors on both SNR and resolution are calculated to show the robustness of SAF algorithm. Both simulation and experimental results indicated that new SAF can improve SNR and resolution of ultrasound images by 9.38 dB and 51% respectively as compared with the conventional method. It therefore has potential for future clinical and research applications. Show more

DOI: 10.3233/XST-2010-0282

Citation: Journal of X-Ray Science and Technology, vol. 19, no. 1, pp. 127-137, 2011