Journal of X-Ray Science and Technology - Volume 27, issue 5

Authors: Ben, Ren-Jy | Jao, Jo-Chi | Chang, Chiung-Yun | Tzeng, Jiun-Siang | Hwang, Lain-Chyr | Chen, Po-Chou

Article Type: Research Article

Abstract: BACKGROUND: Arterial embolism is a major cause of ischemic stroke. Currently, digital subtraction angiography (DSA) is the gold standard in clinical arterial embolization examinations. However, it is invasive and risky. OBJECTIVE: This study aims to longitudinally assess the progression of carotid artery embolism in middle cerebral artery occlusion animal model (MCAO) using magnetic resonance imaging (MRI) techniques. METHODS: Turbo spin echo (TSE), time of flight magnetic resonance angiography (TOF-MRA) and diffusion weighted magnetic resonance imaging (DWI) were used to evaluate the image characteristics of cerebral tissues at 1, 2, 3, 7, 14, 21 and 28 days …after MCAO microsurgery on Sprague-Dawley (SD) rats. Quantitative analysis was performed and compared in MCAO hemisphere and contralateral normal hemisphere. Furthermore, pathologic section using triphenyl tetrazolium chloride (TTC) stain was performed as well. RESULTS: TOF-MRA showed carotid signal void in the embolism side, which is evidence of artery occlusion. The used MRI techniques showed that edema gradually dissipated within one week, but there was no significant change afterwards. The time-varying signal intensity of MRI techniques in MCAO hemisphere changed significantly, but there were no significant changes in contralateral normal hemisphere. Cerebral injury was also confirmed by analysis of pathology images. CONCLUSIONS: The MCAO animal model was successfully established on SD rats using the microsurgery to assess arterial embolization of intracranial tissue injury. Show more

Keywords: Time of flight magnetic resonance angiography, diffusion weighted magnetic resonance imaging, apparent diffusion coefficient, Sprague-Dawley rat, middle cerebral artery occlusion animal model, ischemic stroke

DOI: 10.3233/XST-190538

Citation: Journal of X-Ray Science and Technology, vol. 27, no. 5, pp. 935-947, 2019

Authors: Gao, Juan | Zhang, Qiyang | Liu, Qiegen | Zhang, Xuezhu | Zhang, Mengxi | Yang, Yongfeng | Liang, Dong | Liu, Xin | Zheng, Hairong | Hu, Zhanli

Article Type: Research Article

Abstract: PURPOSE: To reduce the cost of positron emission tomography (PET) scanning systems, image reconstruction algorithms for low-sampled data have been extensively studied. However, the current method based on total variation (TV) minimization regularization nested in the maximum likelihood-expectation maximization (MLEM) algorithm cannot distinguish true structures from noise resulting losing some fine features in the images. Thus, this work aims to recover fine features lost in the MLEM-TV algorithm from low-sampled data. METHOD: A feature refinement (FR) approach previously developed for statistical interior computed tomography (CT) reconstruction is applied to PET imaging to recover fine features in this study. …The proposed method starts with a constant initial image and the FR step is performed after each MLEM-TV iteration to extract the desired structural information lost during TV minimization. A feature descriptor is specifically designed to distinguish structure from noise and artifacts. A modified steepest descent method is adopted to minimize the objective function. After evaluating the impacts of different patch sizes on the outcome of the presented method, an optimal patch size of 7×7 is selected in this study to balance structure-detection ability and computational efficiency. RESULTS: Applying MLEM-TV-FR algorithm to the simulated brain PET imaging using an emission activity phantom, a standard Shepp-Logan phantom, and mouse results in the increased peak signal-to-noise ratio (PSNR) and structural similarity (SSIM) as comparing to using the conventional MLEM-TV algorithm, as well as the substantial reduction of the used sampling numbers, which improves the computational efficiency. CONCLUSIONS: The presented algorithm can achieve image quality superior to that of the MLEM and MLEM-TV approaches in terms of the preservation of fine structure and the suppression of undesired artifacts and noise, indicating its useful potential for low-sampled data in PET imaging. Show more

Keywords: Positron emission tomography (PET), maximum likelihood-expectation maximization (MLEM), low-sampled data, total variation (TV), feature extraction

DOI: 10.3233/XST-190527

Citation: Journal of X-Ray Science and Technology, vol. 27, no. 5, pp. 949-963, 2019

Authors: Yang, Fuqiang | Zhang, Dinghua | Zhang, Hua | Huang, Kuidong

Article Type: Research Article

Abstract: Based on the structural tensor of projection, this study aims to address and test a new improved algorithm applying to the distort projection data to generate a high qualified image by reducing the artifacts and noise from scattering in the cone-beam computed tomography (CBCT). Since the scattering information has a large relationship with the structure of the object, which is reflected by the projection, regional model knowledge for scattering is accomplished by finding the relationship between projection and scattering. As the tensor, the gradient of projection is first calculated in the process for estimating the direction and structural edge of …the object. Then, the Determinant and Traces of the tensor map with different characteristics are computed to determine the different regions. By modeling and fitting the regions of scattering distribution, the knowledge of scattering parameters corresponding to a different region is obtained. Based on the similarity of scattering distribution in adjacent angles, the scatterings with angle sequence are completed by interpolating the prior knowledge obtained through the sparse sampling. By performing the studies on polychromatic X-ray to test the performance of the scattering estimation algorithm, the results show a significant improvement in the images that are reconstructed from the corrected projection. The root mean square error (RMSE) of the proposed method is reduced by 21.8% and 39.8%, respectively. Peak signal to noise ratio (PSNR), and universal quality index (UQI) also indicate better uniformity, where the PSNR is increased by 7.4% and 56.7%, UQI is increased by 70.8% and 262.3% for experimental #Wheel and #Cylinder , respectively. Show more

Keywords: Scattering estimation, angular sequence, structural tensor, cone-beam computed tomography, corrected projection

DOI: 10.3233/XST-190528

Citation: Journal of X-Ray Science and Technology, vol. 27, no. 5, pp. 965-979, 2019

Authors: Zhao, Yongxia | Geng, Xue | Zhang, Tianle | Wang, Xiuzhi | Xue, Yize | Dong, Kexin

Article Type: Research Article

Abstract: OBJECTIVE: To compare image quality, radiation dose, and iodine intake of head-neck CT angiography (CTA) acquired by wide-detector with the gemstone spectral imaging (GSI) combination with low iodine intake or routine scan protocol. METHODS: Three hundred patients who had head-neck CTA were enrolled and divided into three groups according to their BMI values: group A (18.5 kg/m2 ≦ BMI <24.9 kg/m2 ), group B (24.9 kg/m2 ≦ BMI <29.9 kg/m2 ) and group C (29.9 kg/m2 ≦ BMI ≦ 34.9 kg/m2 ) with 100 patients in each group. Patients in each group were randomly divided into two subgroups (n  = 50) …namely, A1, A2, B1, B2, C1 and C2. The patients in subgroups A1, B1 and C1 underwent GSI with low iodine intake (270 mgI/ml, 50 ml) and combined with the ASiR-V algorithm. Other patients underwent three dimensional (3D) smart mA modulation with routine iodine intake (350 mgI/ml, 60 ml). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of all images were calculated after angiography. Images were then subjectively assessed using a 5-point scale. CT dose index of volume and dose-length product (DLP) was converted to the effective dose (ED) and then compared. RESULTS: The mean CT values, SNR, CNR and subjective image quality in subgroups A2, B2 and C2 are significantly lower than in subgroups A1, B1, and C1 (P  < 0.01), respectively. The ED values in subgroup A1, B1, and C1 are 55.18%, 61.89%, and 69.64% lower than those in A2, B2, and C2, respectively (P  < 0.01). The total iodine intakes in subgroups A1, B1, and C1 are 35.72% lower than those in subgroups A2, B2, and C2. CONCLUSIONS: The gemstone spectral imaging with monochromatic images at 53–57 keV combined with ASiR-V algorithm allows significant reduction in iodine load and radiation dose in head-neck CT angiography than those yielded in routine scan protocol. It also enhances signal intensity of head-neck CTA and maintains image quality. Show more

Keywords: Gemstone spectral imaging, radiation dose, image quality, low iodine intake, head-neck CT angiography

DOI: 10.3233/XST-190541

Citation: Journal of X-Ray Science and Technology, vol. 27, no. 5, pp. 981-993, 2019