Journal of X-Ray Science and Technology - Volume 11, issue 3
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Journal of X-Ray Science and Technology is an international journal designed for the diverse community (biomedical, industrial and academic) of users and developers of novel x-ray imaging techniques. The purpose of the journal is to provide clear and full coverage of new developments and applications in the field.
Areas such as x-ray microlithography, x-ray astronomy and medical x-ray imaging as well as new technologies arising from fields traditionally considered unrelated to x rays (semiconductor processing, accelerator technology, ionizing and non-ionizing medical diagnostic and therapeutic modalities, etc.) present opportunities for research that can meet new challenges as they arise.
Abstract: The phase ordering with automatic window selection (PAWS) algorithm for respiratory gating in magnetic resonance imaging is improved by further smoothing motion distribution in k-space. This is achieved by requiring that the displacement discontinuities in k-space and the range of displacement during the acquisition of the center 30% region of k-space are limited to a fraction (1/3 in this study) of the gating window. Simulation results and in vivo imaging experiments suggest…that these modifications reduce the amount of artifacts at a reasonable cost of additional scan time as compared to the original PAWS algorithm.
Abstract: Vascular gene therapy is a potential promising treatment for atherosclerotic disease. Imaging of vascular gene therapy is essential for the assessment of the success of the therapeutic strategy. Several imaging techniques, including MRI, ultrasound, and optical imaging, have been evaluated to monitor, enhance, and track vascular gene delivery, transfection/transduction, and expression. This review summarizes the current status of applying these techniques in the imaging of vascular gene therapy.
Keywords: gene therapy, arteries, magnetic resonance imaging, ultrasonography, optical imaging
Abstract: This article reviews the physics fundamentals in cardiovascular imaging using ultrasound and discusses the current technology and advances in clinical practices. Challenges in future development are included at the end of the article.
Abstract: Purpose: To evaluate recessed elliptical centric ordering of k-space in renal magnetic resonance (MR) angiography. Methods: All imaging was performed on the same 1.5 T MR imaging system (GE Signa CVi) using the body coil for signal transmission and a phased array coil for reception. Gd, 30 ml, was injected manually at 2 ml/sec timed with automatic triggering (SmartPrep). In thirty patients using standard elliptical centric ordering, the scanner paused 8 seconds between detection of…the leading edge of the Gd bolus and initiation of scanning beginning with the center of k-space. For the recessed-elliptical centric ordering in 20 consecutive patients, this delay was reduced to 4 seconds but the absolute center of k-space recessed in by 4 seconds such that in all patients the absolute center of k-space was acquired 8 seconds after detecting the leading edge of the bolus. On the arterial phase images signal-to-noise ratio (SNR) was measured in the aorta, each renal artery and vein and contrast-to-noise ratio (CNR) was measured relative to subcutaneous fat. The standard deviation of signal outside the patient was considered to be "noise" for calculation of SNR and CNR. Incidence of ringing artifact in the aorta and renal veins was noted. Results: Aorta SNR and CNR was significantly higher with the recessed technique (p = 0.02) and the ratio of renal artery signal to renal vein signal was higher with the recessed technique, 4 ± 2, compared to standard elliptical centric, 3 ± 2 (p = 0.03). Ringing artifact was also reduced with the recessed technique in both the aorta and renal veins. Conclusion: Gadolinium-enhanced renal MR angiography is improved by recessing the absolute center of k-space.
Keywords: magnetic resonance angiography, renal artery stenosis, gadolinium, Fourier
Abstract: About two million peripheral angiographies are performed annually in the United States, hence a reduction in exposure would yield significant healthcare benefits. The synchronization of bolus traveling, the table motion, and the fluoroscopic imaging chain can be highly effective for dose reduction in Digital Subtraction Angiography (DSA) by minimizing the field-of-view according to the vascular anatomy of the region traveled by the bolus. The goal of this paper is to demonstrate the feasibility of adjusting the…field-of-view while tracking the contrast bolus, thus reducing the dosage of both the bolus and the radiation. The speed of the bolus is respectively estimated in the systole and diastole stages. An EKG-gated Hammerstein model is used to predict the bolus chasing speed. A real-time algorithm is designed to extract the bolus dynamics, and define the field of view transversely and longitudinally. A limb stabilization technique is also presented to suppress any significant image misalignment. Our simulation results show that the proposed techniques are promising for clinical applications.
Keywords: digital subtraction angiography, real-time imaging
Abstract: Multislice computed tomography (MSCT) is an emerging technique which has an enormous potential to improve the current practice of coronary artery imaging. This article reviews the current status of coronary MSCT angiography (MSCTA) with emphasis on the imaging techniques and clinical utilities of 16-slice CTA. Results and experiences gained from coronary MSCTA in the past few years have taught us that accurate diagnosis of coronary artery disease relies on good technical studies and can be achieved…by optimizing image parameters including image timing and image reconstruction ECG-trigger delay. Current clinical applications of coronary MSCTA include: quantitative assessment of coronary artery stenosis, characterization of coronary atherosclerotic plaques, and follow-up of coronary artery stent and bypass graft. Furthermore, MSCT has brought an increasing awareness to the amount of radiation used in CT. This has prompted CT researchers and manufacturers to improve various techniques and develop new strategies to reduce radiation dose. It is anticipated that MSCT will become a sensitive and accurate tool for detecting coronary artery disease and monitoring outcomes after treatment for coronary artery disease.