Journal of X-Ray Science and Technology - Volume 21, issue 2

Authors: Harimoto, Takashi | Ohno, Seiichiro | Hattori, Kengo | Hirosue, Miyuki | Miyai, Masahiro | Shibuya, Koichi | Kuroda, Masahiro | Kanazawa, Susumu | Kato, Hirokazu

Article Type: Research Article

Abstract: In proton density-weighted (PDW) MR imaging, the patterns of signal intensity vary depending on the imaged material, and change with the flip angle (FA) applied to the imaged material. The correlation between the pre-determined FA and the actual FA applied to imaged objects was investigated using 4 types of phantoms having different dielectric properties. PDW images were acquired using the spin-echo (SE) method and different pre-determined FA. Dependency of the signal intensity distribution in the phantom …on the pre-determined FA differed among phantoms: patterns for water and 0.402 w/w% saline solution phantoms changed with the pre-determined FA, whereas those for olive oil and 4.02 w/w% saline solution phantoms were barely affected by the pre-determined FA. Causes of these phenomena were considered to be the differences between the pre-determined FA and the actual FA among the phantoms; differences were also influenced by the positioning of the phantom. Our study showed that the actual FA in the phantom is greater than the pre-determined FA in high permittivity media, whereas it is reduced by an increased conductivity of the media. Show more

Keywords: MRI, flip angle, signal intensity distribution, permittivity, conductivity, RF magnetic field, finite element method

DOI: 10.3233/XST-130375

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 147-159, 2013

Authors: Chang, Ming | Li, Liang | Chen, Zhiqiang | Xiao, Yongshun | Zhang, Li | Wang, Ge

Article Type: Research Article

Abstract: In recent years, the total variation (TV) minimization method has been widely used for compressed sensing (CS) based CT image reconstruction. In this paper, we propose a few-view reweighted sparsity hunting (FRESH) method for CT image reconstruction, and demonstrate the superior performance of this method. Specifically, the key of the purposed method is that a reweighted total variation (RwTV) measure is used to characterize image sparsity in the cost function, outperforming the conventional TV counterpart. To …solve the RwTV minimization problem efficiently, the Split-Bregman method and other state-of-the-art L1 optimization methods are compared. Inspired by the fast iterative shrinkage/thresholding algorithm (FISTA), a predication step is incorporated for fast computation in the Split-Bregman framework. Extensive numerical experiments have shown that our FRESH approach performs significantly better than competing algorithms in terms of image quality and convergence speed for few-view CT. High-quality images were reconstructed by our FRESH method after 250 iterations using only 15 few-view projections of the Forbild head phantom while other competitors needed more than 800 iterations. Remarkable improvements in details in the experimental evaluation using actual sheep thorax data further indicate the potential real-world application of the FRESH method. Show more

Keywords: Few-view, reweighted TV, Split-Bregman, FISTA, reconstruction

DOI: 10.3233/XST-130370

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 161-176, 2013

Authors: Choi, Kihwan | Fahimian, Benjamin P. | Li, Tianfang | Suh, Tae-Suk | Lei, Xing

Article Type: Research Article

Abstract: In four-dimensional (4D) cone-beam computed tomography (CBCT), there is a spatio-temporal tradeoff that currently limits the accuracy. The aim of this study is to develop a Bregman iteration based formalism for high quality 4D CBCT image reconstruction from a limited number of low-dose projections. The 4D CBCT problem is first divided into multiple 3D CBCT subproblems by grouping the projection images corresponding to the phases. To maximally utilize the information from the under-sampled projection data, a …compressed sensing (CS) method with Bregman iterations is employed for solving each subproblem. We formulate an unconstrained optimization problem based on least-square criterion regularized by total-variation. The least-square criterion reflects the inconsistency between the measured and the estimated line integrals. Furthermore, the unconstrained problem is updated and solved repeatedly by Bregman iterations. The performance of the proposed algorithm is demonstrated through a series of simulation studies and phantom experiments, and the results are compared to those of previously implemented compressed sensing technique using other gradient-based methods as well as conventional filtered back-projection (FBP) results. The simulation and experimental studies have shown that artifact suppressed images can be obtained with as small as 41 projections per phase, which is adequate for clinical 4D CBCT reconstruction. With such small number of projections, the conventional FDK failed to yield meaningful 4D CBCT images, and CS technique using conjugate gradient was not able to recover sharp edges. The proposed method significantly reduces the radiation dose and scanning time to achieve the high quality images compared to the 4D CBCT imaging based on the conventional FDK technique and the existing CS techniques. Show more

Keywords: Four dimensional cone beam computed tomography, compressed sensing, Bregman iteration, fast first-order method

DOI: 10.3233/XST-130371

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 177-192, 2013

Authors: Mouton, Andre | Megherbi, Najla | Van Slambrouck, Katrien | Nuyts, Johan | Breckon, Toby P.

Article Type: Research Article

Abstract: We present a survey of techniques for the reduction of streaking artefacts caused by metallic objects in X-ray Computed Tomography (CT) images. A comprehensive review of the existing state-of-the-art Metal Artefact Reduction (MAR) techniques, drawn predominantly from the medical CT literature, is supported by an experimental comparison of twelve MAR techniques. The experimentation is grounded in an evaluation based on a standard scientific comparison protocol for MAR methods, using a software generated medical phantom …image as well as a clinical CT scan. The experimentation is extended by considering novel applications of CT imagery consisting of metal objects in non-tissue surroundings acquired from the aviation security screening domain. We address the shortage of thorough performance analyses in the existing MAR literature by conducting a qualitative as well as quantitative comparative evaluation of the selected techniques. We find that the difficulty in generating accurate priors to be the predominant factor limiting the effectiveness of the state-of-the-art medical MAR techniques when applied to non-medical CT imagery. This study thus extends previous works by: comparing several state-of-the-art MAR techniques; considering both medical and non-medical applications and performing a thorough performance analysis, considering both image quality as well as computational demands. Show more

Keywords: Medical CT, security CT, Metal Artefact Reduction (MAR)

DOI: 10.3233/XST-130372

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 193-226, 2013

Authors: Huang, Tzung-Chi | Wu, Tung-Hsin | Lin, Yang-Hsien | Guo, Wan-Yuo | Huang, Wei-Chien | Lin, Chung-Jung

Article Type: Research Article

Abstract: OBJECTIVE: We analyzed intracranial regional blood flows using an optical flow method (OFM) and digital subtraction angiography in patients with internal carotid artery (ICA) stenosis. We also retrospectively explored the correlation between the patients' diagnoses and the severity of the ICA stenoses. MATERIALS AND METHODS: OFM, an image-processing algorithm to estimate motion, was applied to determine the mean velocity V_{mean} in the vessels. A group of 40 patients without vascular anomalies acted …as the control group. The patients were classified as having either moderate stenosis (< 80%, n=14) or severe stenosis (> 80%, n=23). RESULTS: The V_{mean} of the ICAs was significantly lower in the stenotic group compared with the control group (p< 0.01). The V_{mean} of the ICAs was inversely correlated with the severity of the stenosis (p< 0.05). The receiver operating characteristic curve of the V_{mean} in an AP view showed substantial discriminatory power, with an optimal cutoff value of 3.48 pixels/frame for the detection of patients with carotid stenosis. The sensitivity and specificity were 84% and 50%, respectively. On a lateral view, the best cutoff for the V_{mean} was 4.01 pixels/frame, and the sensitivity and specificity were 92% and 43%, respectively. CONCLUSIONS: Digital subtraction angiography combined with the OFM is a feasible parametric method for intracranial blood flow measurements in patients with moderate to severe carotid stenosis. Show more

Keywords: Stenosis, blood flow, optical flow method

DOI: 10.3233/XST-130373

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 227-235, 2013

Authors: Amato, Ernesto | Italiano, Antonio | Leotta, Salvatore | Pergolizzi, Stefano | Torrisi, Lorenzo

Article Type: Research Article

Abstract: Gold nanoparticles (GNPs) are a promising radiosensitizer agent in radiotherapy. Through a simulation performed with the Geant4 Monte Carlo code, we evaluated the dose enhancement effect of GNPs during therapies with an x-ray tube operating at 150 kV (E=55 keV and E_{max} = 150 keV) and we studied the impact of GNP diffusion out of the tumour vessels, in terms of antiangiogenic and cytotoxic effects. Firstly, a single x-ray beam was assumed to irradiate a …parallelepiped volume of soft tissue, in which a GNP-doped "target" volume was placed at different depths. Average dose enhancement factors (DEF) in presence of GNPs were obtained as a function of the target depth and GNP concentration, uniformly distributed; values ranging between 1.6 for 10 mg Au/g at 0 cm and 7.2 for 200 mg Au/g at 5 cm were determined. Furtherly, a second geometry was adopted, in which a blood capillary vessel (10 μm thick and 10 μm of inner radius) was placed at the centre of a cubic volume of soft tissue; doses and DEFs to the capillary endothelium as well as to the surrounding viable tumour were evaluated, for different models of GNP diffusion. Our results indicate that the radial DEF profiles around the vessel are in close relationship with the radial profiles of GNP concentration assumed, except for at sharp gradients of concentration. DEFs at the endothelium ranged from 1.6 to 6.5, for GNP concentrations in the blood of 10 and 200 mg/ml, respectively. These data can be helpful for the development of new and more specific GNP-based radiosensitizers of potential interest in radiotherapy, exploiting the combined benefit of anti-angiogenic and cytotoxic dose enhancement effects. Show more

Keywords: Gold nanoparticle, radiotherapy, radiosensitization, angiogenesis, Monte Carlo simulation

DOI: 10.3233/XST-130374

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 237-247, 2013

Authors: Chang, Yu-Bing | Xia, James J. | Yuan, Peng | Kuo, Tai-Hong | Xiong, Zixiang | Gateno, Jaime | Zhou, Xiaobo

Article Type: Research Article

Abstract: Recent advances in cone-beam computed tomography (CBCT) have rapidly enabled widepsread applications of dentomaxillofacial imaging and orthodontic practices in the past decades due to its low radiation dose, high spatial resolution, and accessibility. However, low contrast resolution in CBCT image has become its major limitation in building skull models. Intensive hand-segmentation is usually required to reconstruct the skull models. One of the regions affected by this limitation the most is the thin bone images. This …paper presents a novel segmentation approach based on wavelet density model (WDM) for a particular interest in the outer surface of anterior wall of maxilla. Nineteen CBCT datasets are used to conduct two experiments. This mode-based segmentation approach is validated and compared with three different segmentation approaches. The results show that the performance of this model-based segmentation approach is better than those of the other approaches. It can achieve 0.25 ± 0.2 mm of surface error from ground truth of bone surface. Show more

Keywords: 3D segmentation, active shape model (ASM), statistical shape model (SSM), craniomaxillofacial (CMF) surgeries, cone-beam computed tomography (CBCT)

DOI: 10.3233/XST-130369

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 251-282, 2013

Authors: Shao, Hongda | Li, Baoping | Zhang, Xiao | Xiong, Zhaoming | Liu, Yong | Tang, Guangyu

Article Type: Research Article

Abstract: To compare the respective diagnostic efficiency for breast cancer in Chinese women with x-ray mammography (XRM), ultrasound (US), magnetic resonance imaging (MRI; standard dynamic contrasted-enhanced MRI with diffusion-weighted imaging), and different combinations of these imaging modalities, ninety Chinese women patients with clinically suspected breast cancer underwent prospective breast XRM, US, and MRI. The diagnostic performance of each imaging method and different combinations of methods was compared, with the pathological report serving as …the gold standard. In this cohort study 54.4% cases with age of 53.2 ± 7.6 years old were categorized as ACR 3 or 4 tissue density. In the diagnosis of breast cancer, sensitivity and diagnostic accuracy [area under the Receiver Operating Characteristic curve (AUC)] were significantly higher for MRI alone than for either XRM alone or US alone (P< 0.05). Of the misdiagnosed cases on XRM, up to 86.7% cancers were located in dense breasts. US and MRI can play important role in screening young Chinese women. The diagnostic sensitivity was significantly higher for combined MRI+US+XRM (98.2%, χ^2 =25.9, P< 0.001), MRI+US (94.5%, χ^ 2 53.3, P=0.002) and MRI+XRM (92.9% combination of two or three methods significantly improved the diagnostic sensitivity for breast cancer in Chinese women. When the results based on different imaging modalities or their combinations are inconsistent, further pathological diagnosis is very important for arriving at a correct diagnosis. Show more

Keywords: Breast cancer, magnetic resonance imaging, ultrasound, X-ray mammography, diagnosis

DOI: 10.3233/XST-130376

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 283-292, 2013

Authors: Tu, Xiang-An | Zhuang, Jin-Tao | Zhao, Liang | Zhao, Liang-Yun | Zhao, Ji-Quan | Lü, Kun-Long | Sun, Xiang-Zhou | Qiu, Shao-Peng | Zhang, Yuanyuan | Deng, Chun-Hua

Article Type: Research Article

Abstract: To evaluate the efficacy of transurethral bipolar plasma kinetic resection of ejaculatory duct for ejaculatory duct obstruction. The clinical information of 42 cases of ejaculatory duct obstruction was analyzed between July 2008 and June 2012. The diagnostic criteria included semen analysis, fructose and neutral α-glucosidase measurement in seminal plasma, transrectal ultrasonography, magnetic resonance imaging and vasography necessarily. Endoscopic procedure with bipolar plasma kinetic resection of ejaculatory duct was performed in all patients. …Among these cases followed up 6∼24 months after operation, 38 patients (90.5%) had improved semen parameters, 23 azoospermic patients (60.5%) had sperm in the semen and 13 patients' wife (31%) achieved pregnancies in 42 cases of bipolar plasma kinetic resection of ejaculatory duct. Postoperative complications ensued as epididymitis in 1 case, watery ejaculate in 1, but no serious complication was observed. Bipolar plasma kinetic resection of ejaculatory duct appears to represent a promising endoscopic treatment alternative for ejaculatory duct obstruction patients, with high efficacy, less complications, quicker recovery and satisfactory follow-up parameters. Show more

Keywords: Ejaculatory duct obstruction, bipolar, electrosurgery, transurethral resection of ejaculatory duct

DOI: 10.3233/XST-130377

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 293-302, 2013

Authors: Zhang, Yong | Tong, Zang | Zhang, Yuanyuan

Article Type: Research Article

Abstract: Splenogonadal fusion is a rare congenital anomaly where the spleen is attached to either testicular or ovarian tissues. In present case, splenogonadal fusion presents as a large mass consciously connected to atrophic testis in left scrotum. The diagnosis of splenic gonadal fusion relies on radiologic and pathologic findings. Uniform density and vessels connection originating from splenic hilum between principle spleen and let testicle were observed with ultrasound and X-ray computed tomography (CT). Surgical …exploration ruled out malignancy, extratesticular scrotal mass with affected testicle was removed. Pathologic examination demonstrated that ectopic spleen tissue and ipsilateral atrophic testis. Our data suggested that orchiectomy should be performed when contralateral testicle is normal and the affected testicular appeared significantly atrophy. Show more

Keywords: Splenogonadal fusion, ectopic spleen, testis

DOI: 10.3233/XST-130378

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 2, pp. 303-308, 2013