Journal of X-Ray Science and Technology - Volume 21, issue 4

Article Type: Other

DOI: 10.3233/XST-130404

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 451-451, 2013

Authors: Wang, Qian | Zhao, Xinming | Song, Junfeng | Guo, Ning | Zhu, Ying | Liu, Jianxin | Qi, Weiwei | Wu, Jing | Liang, Yuan | Feng, Shichao | Hu, Mancang | Zhou, Chunwu | Wang, Xiaoying | Hong, Nan

Article Type: Research Article

Abstract: Multi-phase spiral Computed tomography (CT) of abdomen has been widely used as an effective imaging modality to diagnose variety of diseases. As a result, the accumulated radiation exposure on the abdomen is substantially higher than other human organ regions. According to ALARA (as low as reasonably achievable) principle, how to control radiation dose without compromising imaging quality becomes a research topic of high interest. However, how to achieve dose optimization of the abdomen CT examinations in …Chinese patients have not been fully investigated in previous studies. In this study, we develop an abdomen-equivalent tissue model made by well-known CTP579 auxiliary testing model and the real CT data acquired from 68 Chinese male subjects. Combining with catphan600, we simulated the visibility of low and high contrast objects at adult abdomen under variety of x-ray dose levels. Using the automatic tube current modulation (ATCM) technique, we reduced the total radiation dose and identified a proper noise index (NI) for Chinese patients to maintain low or high contrast detectability of abdominal CT image. Our numerical experiments showed that in the phantom study for Chinese patients, when a NI was set at 10, the radiation dose reduced by 34.3% with low contrast objects detectable, while setting NI at 14 the dose level decreased by 65.1% without change the detectability of high contrast targets. The subjective ratings from three radiologists also yielded high consistence with Kappa > 0.75. This study demonstrated the feasibility of performing the CT dose optimization studies through a unique phantom with the ATCM method. Show more

Keywords: Abdomen, phantom, MSCT, image quality, radiation dose

DOI: 10.3233/XST-130403

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 453-464, 2013

Authors: Yang, Min | Duan, Shengling | Duan, Jinghui | Wang, Xiaolong | Li, Xingdong | Meng, Fanyong | Zhang, Jianhai

Article Type: Research Article

Abstract: Fast-continuous-rotation is an effective measure to improve the scanning speed and decrease the radiation dose for cone-beam CT. However, because of acceleration and deceleration of the motor, as well as the response lag of the scanning control terminals to the host PC, uneven-distributed and redundant projections are inevitably created, which seriously decrease the quality of the reconstruction images. In this paper, we first analyzed the aspects of the theoretical sequence chart of the fast-continuous-rotation mode. …Then, an optimized sequence chart was proposed by extending the rotation angle span to ensure the effective 2π-span projections were situated in the stable rotation stage. In order to match the rotation angle with the projection image accurately, structure similarity (SSIM) index was used as a control parameter for extraction of the effective projection sequence which was exactly the complete projection data for image reconstruction. The experimental results showed that SSIM based method had a high accuracy of projection view locating and was easy to realize. Show more

Keywords: Cone-beam CT, fast-continuous-rotation scanning, data redundancy, structural similarity

DOI: 10.3233/XST-130402

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 467-479, 2013

Authors: Zhang, Hua | Sonke, Jan-Jakob

Article Type: Research Article

Abstract: Cone-beam (CB) computed tomography (CT) is widely used in the field of medical imaging for guidance. Inspired by Betram's directional interpolation (BDI) methods, directional sinogram interpolation (DSI) was implemented to generate more CB projections by optimized (iterative) double-orientation estimation in sinogram space and directional interpolation. A new CBCT was subsequently reconstructed with the Feldkamp algorithm using both the original and interpolated CB projections. The proposed method was evaluated on both phantom and …clinical data, and image quality was assessed by correlation ratio (CR) between the interpolated image and a gold standard obtained from full measured projections. Additionally, streak artifact reduction and image blur were assessed. In a CBCT reconstructed by 40 acquired projections over an arc of 360 degree, streak artifacts dropped 20.7% and 6.7% in a thorax phantom, when our method was compared to linear interpolation (LI) and BDI methods. Meanwhile, image blur was assessed by a head-and-neck phantom, where image blur of DSI was 20.1% and 24.3% less than LI and BDI. When our method was compared to LI and DI methods, CR increased by 4.4% and 3.1%. Streak artifacts of sparsely acquired CBCT were decreased by our method and image blur induced by interpolation was constrained to below other interpolation methods. Show more

Keywords: Cone-beam CT, streak artifacts, sparse acquisition, sinogram interpolation, directional interpolation

DOI: 10.3233/XST-130401

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 481-496, 2013

Authors: He, Peiheng | Zhu, Qi | Zhang, Zhaohui | Zou, Xuenong | Xu, Dongliang

Article Type: Research Article

Abstract: OBJECTIVE: To investigate relationship between the tibial mechanical axis and bony landmarks of the calf and foot by developing a new laser-calibrated position for radiography of the lower limb. MATERIALS AND METHODS: A total of 120 volunteers were randomly divided into two groups. All subjects were marked with skin projection of the hypothetical axis of the calf on the frontal and sagittal planes. Radiographs of weight-bearing full-length lower-limb were obtained by the laser-calibrated positioning …in the experimental group, and by the use of conventional technique in the control group. To consider the rotation of the calf, radiological features of the knee and ankle were investigated. The relationship between the tibial mechanical axis and the bony landmarks of the calf and foot were also measured. RESULTS: Anteroposterior view depicted a tangential projection on the superior/inferior tibiofibular syndesmosis and between lateral malleolus and talus in ankle mortise in the experimental group. Bony overlap on the superior/inferior tibiofibular syndesmosis and between lateral malleolus and talus was seen in control group. On the tangential projection, it also presented a clear wheel-like contour of the medial femoral condyle, but a partial overlap between medial femoral condyle and tibial plateau. The femoral joint angle between the connecting line at the lowest point of the medial and lateral femoral condyles and the tibial mechanical axis was 83.6° ± 2.49° in the experimental group and 85.3° ± 2.18° in the control group (P < 0.001). The tibial tubercle-axis distance from the center of the medial and middle one-third of the tibial tubercle to the tibial mechanical axis was 1.5 mm in the experimental group and 3.7 mm in the control group (P < 0.05). The malleoli-axis distance from the midpoint of the bimalleolar line joining the tips of the medial and lateral malleoli to the tibial mechanical axis was 1.9 mm in the experimental group and 6.9 mm in the control group (P < 0.001). Lateral view showed no difference between the tibial mechanical axis and the fibular reference line within two groups. CONCLUSION: In the new radiographic position, our data indicate that the hypothetical tibial mechanical axis and fibular reference line, obtained by marking the specified anatomic landmarks of the calf and foot, are located more closely to the tibial mechanical axis by correcting the rotation of the calf and foot during the radiography. On anteroposterior view, the tibial mechanical axis was approximately 2 mm medial to the center of the ankle. This indicates that the hypothetical tibial mechanical axis marked on the skin could be referred to guide the tibial osteotomy in total knee arthroplasty. Show more

Keywords: Anatomical position, lower-limb radiography, anatomical landmark, tibial mechanical axis, laser calibration

DOI: 10.3233/XST-130400

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 497-506, 2013

Authors: Lau, Andy | Chen, Yong | Ahmad, Salahuddin

Article Type: Research Article

Abstract: In-vivo range verification systems for incident protons recently utilize positron emission tomography (PET) based on the phenomenon of positron-emitting nuclei (PEN). However, recent investigations are suggesting that the range can be verified also from the prompt gamma (PG) photon emissions generated from proton interactions. In this work we investigate using the Geant4 Monte Carlo toolkit the clinical viability of a theoretical sequential detector system to verify the range of protons in proton radiotherapy by the PG …method for simple geometries and beam configurations. The results show a correlation between selected emitted PG rays and the incident protons range and suggest that our detector system is capable of in-vivo range monitoring for energies typical of radiation oncology applications. Future work will include implementing more realistic scenarios and optimizing current detector parameters. Show more

Keywords: Prompt gamma, Geant4 simulation, radiation therapy

DOI: 10.3233/XST-130399

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 507-514, 2013

Authors: Zou, Xiaobing | Yu, Hengyong | Zeng, Li

Article Type: Research Article

Abstract: To reconstruct images from truncated projections collected along a spiral trajectory, the most common approach is to smoothly extrapolate each projection to suppress truncation artifacts. Based on the work of Dennerlein, a local reconstruction algorithm is developed for spiral cone beam computed tomography (CT), which does not need explicit projection extrapolation. This algorithm is a filtered-backprojection (FBP) format and contains three major steps: cosine weight, filtration, and backprojection. While the cosine weight …and backprojection steps are the same as the classical Feldkamp – Davis – Kress (FDK) scheme, the filtering step contains two steps: Laplace filtering and Radon transform-based filtering. Numerical simulation results show that the proposed algorithm has a better performance than FDK algorithm for region-of-interest (ROI) reconstruction of spiral cone-beam CT. Show more

Keywords: Computed tomography, spiral cone beam computed tomography, truncated projection, region-of-interest reconstruction, local filtration, Laplace operator

DOI: 10.3233/XST-130398

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 515-526, 2013

Authors: Qin, Zhuanping | Cui, Shanshan | Zhao, Huijuan | Zhou, Xiaoqing | Jia, Mengyu | Yang, Yanshuang | Fan, Ying | Gao, Feng

Article Type: Research Article

Abstract: Endoscopic diffuse optical tomography (DOT) is a new medical imaging modality with the potential applications in functional imaging of the internal organs. To cut down the measurement time and the computation burden of image reconstruction, in this paper, we developed the image reconstruction algorithm with the partial measurement in the effective detection range (EDR) of a tubular tissue and the corresponding endoscopic imaging system with a novel endoscopic probe for flexibly selecting the detection sites. For …a typical inner size and optical properties of the cervix, it is found that EDR is less than half of the inner circumference. Comparing to the traditional method, the adoption of EDR results in a reduction of more than a factor of two in the time cost for a measurement cycle and for the total iteration reconstruction. Images reconstructed from the simulation data demonstrate that the proposed method achieves equivalent image quality to that obtained from the complete data set. The images reconstructed from the EDR measurements on cervix-like solid phantoms show that both the location and size of the targets are reconstructed correctly. The proposed method will be useful to the development of endoscopic DOT technologies for cancer detection in tubular organs including cervix. Show more

Keywords: Endoscopic diffuse optical tomography, partial measurement, effective detection range, frequency-domain, image reconstruction algorithm

DOI: 10.3233/XST-130397

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 527-543, 2013

Authors: Zou, Yongning | Wang, Jue | Li, Jianwei

Article Type: Research Article

Abstract: Segmentation of CT volume data is important and useful in non-destructive testing and evaluating. To eliminate the artifacts influence, we propose a new approach of 3D defect segmentation using two steps. First of all, an initial segmentation using 3D morphological method is performed. The initial segmentation results include false defects. Secondly, resample in polar coordinates method is performed. The experimental results prove that our method is effective to correctly segment 3D defects and eliminate false segmentation. …Some experiments on CT volume data with noise are made, the results show that our method is also useful. Show more

Keywords: CT volume data, segmentation, morphology, 3D defect

DOI: 10.3233/XST-130396

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 545-556, 2013

Authors: Krishnananda, | Niranjana, K.M. | Badiger, N.M.

Article Type: Research Article

Abstract: The real and imaginary form factors of silver atom have been determined by using EDXRF method. The K x-ray photons in the energy range from 8.62 keV to 52.18 keV are generated by sending 59.56 keV gamma photons from ^{241} Am radioactive source on various targets. These K x-ray photons are transmitted through silver foils of suitable thickness. The incident and transmitted K x-ray photon intensities have been measured with a high resolution HPGe detector …which is coupled to 16K MCA. The photoelectric cross sections at different K x-ray energies have been determined by measuring the intensities of the incident and transmitted x-ray photons. From these photoelectric cross section values, the imaginary form factors and the real form factors have been determined at various photon energies. Measured imaginary and real form factor values have been compared with theoretical values predicted by XCOM [23] and FFAST [24]. Show more

Keywords: Mass attenuation coefficient, HPGe detector, photoelectric cross-section, real and imaginary form factors

DOI: 10.3233/XST-130388

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 557-565, 2013

Authors: Alivov, Yahya | Feng, Jun | Molloi, Sabee

Article Type: Research Article

Abstract: We studied in details the effect of various X-ray tube parameters (cathode size, anode size, anode – lens distance, etc.) on TiO_{2} nanotube field emission electron-beam focal spot size (FSS) and lens voltages for a single electrode lens system. The simulations were performed using commercially available SIMION 8.1 software. A wide range of parameters was simulated to determine conditions when FSS and lens focusing voltage had minimum values. In particular, the dependence of FSS …and lens voltages on cathode size (d_{S} ) was studied for different size lens apertures (d_{L} ) and different anode voltages. The cathode size d_{S} was varied in the range from 0.1 mm to d_{L} ; the d_{L} was changed from 4 to 24 mm in 4 mm increments. The simulations were performed for two different V_{A} values 60 kV and 120 kV. It was found that for 20 mm and 24 mm diameter lens apertures the maximum cathode size when the resulting FSS was not greater than 1600 μm (the focal spot size in clinical X-ray CT) were 17.5 mm and 16.2 mm, respectively. The lens voltages V_{f} corresponding to 17.5 mm and 16.2 mm cathode size in 20 mm and 24 mm aperture diameter x-ray tubes are 1850 V and −1550 V, respectively. Show more

Keywords: Nanotubes, field emitters, X-ray source, electron beam, electrostatic electron lens, focal spot size

DOI: 10.3233/XST-130387

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 567-577, 2013

Authors: Liu, Fenglin | Wang, Ge | Cong, Wenxiang | Hsieh, Scott S. | Pelc, Norbert J.

Article Type: Research Article

Abstract: A bowtie is a filter used to shape an x-ray beam and equalize its flux reaching different detector channels. For development of spectral CT with energy discriminating photon-counting (EDPC) detectors, here we propose and evaluate a dynamic bowtie for performance optimization based on a patient model or a scout scan. With a mechanical rotation of a dynamic bowtie and an adaptive adjustment of an x-ray source flux, an x-ray beam intensity profile can be modulated. First, …a mathematical model for dynamic bowtie filtering is established for an elliptical section in fan-beam geometry, and the contour of the optimal bowtie is derived. Then, numerical simulation is performed to compare the performance of the dynamic bowtie in the cases of an ideal phantom and a realistic cross-section relative to the counterparts without any bowtie and with a fixed bowtie respectively. Our dynamic bowtie can equalize the expected numbers of photons in the case of an ideal phantom. In practical cases, our dynamic bowtie can effectively reduce the dynamic range of detected signals inside the field of view. Although our design is optimized for an elliptical phantom, the resultant dynamic bowtie can be applied to a real fan-beam scan if the underlying cross-section can be approximated as an ellipse. Furthermore, our design methodology can be applied to specify an optimized dynamic bowtie for any cross-section of a patient, preferably using rapid prototyping technology. Show more

Keywords: Dynamic bowtie, tube current modulation, elliptical phantom, computed tomography (CT)

DOI: 10.3233/XST-130386

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 579-590, 2013

Article Type: Other

Citation: Journal of X-Ray Science and Technology, vol. 21, no. 4, pp. 591-599, 2013