Journal of X-Ray Science and Technology - Volume 12, issue 2

Authors: Ye, Chang | Luo, Qingming | Chen, Wei R. | Liang, Wenxi | Luo, Weihua | Zhong, Aijun

Article Type: Research Article

Abstract: The thickness of the surrounding tissue is a crucial factor in distinguishing the internal blood vessels in digital X-ray images, because enough contrast between vessels and tissues must be generated. We investigated the X-ray attenuations of fat, liver, and muscle tissues, using a digital X-ray imaging system specially designed for small animal studies and the contrast between these tissues and blood vessels. The fat, muscle and the liver tissues were collected from the abdomen, the back …and the liver of an adult crossbred swine, respectively. The blood vessels were from mesentery of a Wistar rat. The attenuation coefficients of different tissues and blood vessels of different sizes were measured under different X-ray exposures. Also quantified was the contrast between the tissues and the blood vessels when the diameter of the blood vessel and the thickness of the tissues were the same. The limiting thickness of various tissues at different X-ray exposures was obtained for detecting internal blood vessels of a given size, using the CCD detecting limit, the contrast resolution of the imaging system and the tissue-vessel configuration. The results provided herein could be used for optimization of the parameters of digital X-ray imaging in detecting internal blood vessels. Show more

Keywords: digital X-ray imaging, charge-coupled device (CCD), small blood vessel, image contrast, detection limitation

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 2, pp. 59-71, 2004

Authors: Zeng, Kai | Chen, Zhiqiang | Zhang, Li | Wang, Ge

Article Type: Research Article

Abstract: The most popular Feldkamp algorithm for cone-beam image reconstruction assumes a scanning circle, and performs well only with a small cone angle. In this report, we propose a Feldkamp-type algorithm to increase the cone angle by several folds at a radiation dose comparable to that required by the classic Feldkamp algorithm. In our scheme, two half-scans of different radii are used. Then, approximate reconstructions from two half-scans are combined to produce a superior image volume by …utilizing a relationship between the half-scan reconstruction error and the scanning locus radius. The merit of this half-scan error reduction based (HERB) algorithm is demonstrated in numerical simulation with the 3D Shepp-Logan phantom. Show more

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 2, pp. 73-82, 2004

Authors: Bomsdorf, H. | Müller, T. | Strecker, H.

Article Type: Research Article

Abstract: During the past decade methods for non-destructive identification and imaging of materials within bulk objects have been developed based on the measurement of coherent X-ray scatter. Their applicability to a given medical or industrial problem, however, strongly depends on the individual system design since the key features resolution, sensitivity and spatial resolution are strongly interrelated. In this paper quantitative simulation is presented as a means for system optimization without the requirement for time consuming experiments. …By means of a full 3D model of the scatter geometry, which holds for rotationally symmetric collimator arrangements, possible photon scatter paths are evaluated using a Monte Carlo algorithm. This enables simulation of energy resolved scatter patterns based on powder diffraction (PDF) literature data. In addition, the influence of the attenuation caused by the object is taken into account by calculating the transmission spectrum. For quantitative assessment of sensitivity, scatter count rates and thus signal-to-noise ratios are calculated based on a calibration procedure combining the result of a simulation with that of a corresponding measurement. The results of the simulation are shown to be in very good agreement with experimental data. Taking various examples of application as a basis, the usability of the simulation program for the assessment and individual optimization of system performance is demonstrated. Show more

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 2, pp. 83-96, 2004

Authors: Yu, Hengyong | Wang, Ge

Article Type: Research Article

Abstract: Recently, Katsevich proposed the first exact helical cone-beam reconstruction algorithm that takes longitudinally truncated data collected from part of a scanning turn. A key theoretical basis is that any point inside the scanning helix belongs to one and only one PI-line. Unfortunately, he only provided a general formulation and did not describe the implementation details. To make this complicated algorithm more transparent, we report here specifically how to program the Katsevich algorithm in the planar detector …geometry. As an important component, we also analyze the effects of various implementation parameters on the image quality. Our results are intended to be valuable for those who are interested in evaluating, improving and extending the Katsevich approach. Show more

Keywords: computed tomography (CT), spiral cone-beam, Katsevich algorithm, filtered backprojection (FBP), image artifacts

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 2, pp. 97-116, 2004

Authors: Athiraman, Hemanth | Wolf, Roman F. | Bartels, Kenneth E. | Shivakoti, Suman | Liu, Hong | Chen, Wei R.

Article Type: Research Article

Abstract: Laser tissue welding has the potential to become an effective method for wound closure and healing without sutures and staples. Laser light has the ability to control the volume of tissue being exposed. It can also cause selective tissue fusion by activating light-absorbing dye in the target tissue without significantly affecting the surrounding normal tissue. Temperature is a crucial factor in tissue welding. Too high a temperature causes irreversible tissue damage, while too low a temperature …fails to form a strong tissue bond. To effectively control tissue temperature, an 805-nm laser was used in conjunction with in situ application of indocyanine green (ICG) as the light-absorbing dye. In vivo laser tissue welding using rat skin was performed with the laser-dye combination. Using different power densities, ranging from 0.4 W/cm^2 to 1.2 W/cm^2 , the skin temperature could be increased from body temperature to a range of 40°C to 72°C, with the enhancement of ICG solution. The long-term effect of laser welding was studied by measuring the tensile strength of the welded tissue at different times after the welding, in comparison with that of the tissue closure using conventional suturing. Our results showed that the welded tissue provided a stronger tissue holding power at the early stage than the sutured tissue and provided almost the same strength as the sutured tissue 30 days after the welding. Show more

Keywords: 805-nm laser, indocyanine green, laser tissue welding, temperature measurement, wound healing, tissue tensile strength

Citation: Journal of X-Ray Science and Technology, vol. 12, no. 2, pp. 117-126, 2004