Multiple Tomographic Images Research Articles

Crosstalk-free for multi-plane holographic display using double-constraint stochastic gradient descent.

Multi-plane crosstalk is a key issue affecting the quality of holographic three-dimensional (3D) displays. The time-multiplexing stochastic gradient descent (TM-SGD) method has been applied to solve the inter-plane crosstalk problem in multi-plane reconstruction. However, the inter-plane crosstalk increases greatly as the inter-plane interval decreases, and the optimization time increases greatly as the number of planes increases. In this paper, we propose a double-constraint stochastic gradient descent method to suppress inter-plane crosstalk in multi-plane reconstruction. In the proposed method, we use the mask to make the optimization process focus more on the signal region and improve the reconstruction quality. Meanwhile, we adopt a constraint strategy of phase regularization to reduce the phase randomness of the signal region and suppress inter-plane crosstalk. Numerical simulation and optical experiment results confirm that our method can effectively suppress the inter-plane crosstalk and improve the quality of the reconstructed planes at a lower inter-plane interval. Moreover, the optimization time of our method is almost 4 times faster than that of TM-SGD. The proposed method can contribute to the realization of tomographic 3D visualization in the biomedical field, which requires the reconstruction of multiple tomographic images without inter-plane crosstalk.

Cole-Cole analysis of thrombus formation in an extracorporeal blood flow circulation using electrical measurement

A Cole-Cole analysis of electrical impedance of blood was performed to explore the possibility of monitoring thrombus formation in extracorporeal blood circulation. Thrombus formation experiments were conducted in both static and flowing conditions by changing the coagulability of the bovine and swine blood. Among the four Cole-Cole parameters which are the relaxation frequency fc, the resistance at zero frequency R0, the resistance at infinite frequency R∞, shape factor α, the relaxation frequency fc first increased, reached to the characteristic peak and then decreased during thrombus formation. Other Cole-Cole parameters were either monotonically increasing or decreasing throughout the time without any characteristic point. Additionally, change of pattern followed the same increasing/decreasing pattern for all red blood cells (RBCs) concentrations. Simulations were made on the basis of Hanai's mixture formula to evaluate the results. On the basis of evaluation, the peak time is considered as the time to form the RBCs aggregation. Hence, the monitoring of the relaxation frequency fc is the appropriate strategy form thrombus detection. It provides the possibility of visualizing thrombus formation based on the single tomographic image of relaxation frequency distribution instead of multiple tomographic images of impedance at various frequencies in multifrequency electrical tomography.

Postoperative follow-up of olecranon fracture by digital tomosynthesis radiography

Digital tomosynthesis with flat-panel detector radiography is a novel application that allows easy, swift volume data acquisition of any anatomical site of interest with arbitrary patient posture. A single sweep of the X-ray tube provides multiple tomographic images of high resolution. We present the first patient with olecranon fracture who underwent internal fixation and 1-year postoperative follow-up with tomosynthesis. The minimal metallic artifact by this modality successfully provided detailed information regarding the healing process of the fracture.

Real-time three-dimensional echocardiography: technological gadget or clinical tool?

The complex anatomy of cardiac structures requires three-dimensional spatial orientation of images for a better understanding of structure and function, thereby improving image interpretation. Real-time three-dimensional echocardiography is a recently developed technique based on the design of an ultrasound transducer with a matrix array that rapidly acquires image data in a pyramidal volume. The simultaneous display of multiple tomographic images allows three-dimensional perspective and the anatomically correct examination of any structure within the volumetric image. As a consequence, it is less operator-dependent and hence more reproducible. Dedicated software systems and technologies are based on high-performance computers designed for graphic handling of three-dimensional images by providing possibilities beyond those obtainable with echocardiography. This methodology allows simultaneous display of multiple superimposed planes in an interactive manner as well as a quantitative assessment of cardiac volumes and ventricular mass in a three-dimensional format without a pre-established assumption of cardiac chamber geometry. In addition, myocardial contraction and/or perfusion abnormalities are clearly identified. Finally, real-time three-dimensional colour Doppler flow mapping enables complete visualisation of the regurgitant jet and new ways of assessing regurgitant lesion severity. Thus, this technique expands the abilities of non-invasive cardiology and may open new doors for the evaluation of cardiac diseases. In this article, current and future clinical applications of real-time three-dimensional echocardiography are reviewed.

Flow distribution and velocity measurement in a radial flow fixed bed reactor using electrical resistance tomography

Electrical resistance tomography is a relatively simple and inexpensive technique for imaging electrically conducting systems. It has been applied to visualise the flow pattern and distribution inside a radial flow packed bed of novel design for improving reactor performance with lower pressure drop. The density of information yielded by electrical tomography is suitable for validation of Computational fluid dynamics. Sets of tomographic images representing slices through a packed bed have been obtained for a 8-plane × 16-electrode sensor configuration which produces of the order 10 3 conductivity measurements in three-dimensions. Pulse injections of high conductivity tracer, both uniformly in the feed and localised, can be imaged as multiple tomographic images or 3D solid-body images, revealing the internal flow pattern. Differentiation of the motion of the tracer peak conductivity within pixels in the sensing planes and between the planes allows the local flow velocities and directions to be determined. This quantifies the flow pattern for uniformity and radial distributive properties.

Real-time three-dimensional echocardiography: an overview.

Conventional echocardiography and its representation of the heart in a two-dimensional format only provide partial information about cardiac function. Real-time three-dimensional echocardiography is a recently developed technique based on the design of an ultrasound transducer with a matrix array that instantaneously acquires the image contained in a pyramidal volume. The simultaneous display of multiple tomographic images allows the anatomically correct examination of any structure contained within the volumetric image. Software and technologies based on high performance computers designed for graphic handling of three-dimensional images permit the rapid mapping of the volumetric image and provide possibilities beyond those of the echograph. Using this methodology, it is possible to simultaneously visualize multiple superimposed planes in an interactive manner. Real-time three-dimensional echocardiography also allows a quantitative assessment of cardiac volumes, ventricular mass, and myocardium with contraction and/or perfusion abnormalities. This technique thus expands the abilities of non-invasive cardiology and may open new doors for the evaluation of cardiac disease.

High-speed ultrasound volumetric imaging system. II. Parallel processing and image display

For pt.I see ibid., vol.38, no.2, p.100-8 (1991). The authors describe the design, application, and evaluation of parallel processing to the high-speed volumetric ultrasound imaging system. The scanner produces images analogous to an optical camera or the human eye and supplies more information than conventional sonograms. Potential medical applications include improved anatomic visualization, tumor localization, and better assessment of cardiac function. The system uses pulse-echo phased array principles to steer a 2-D array transducer of 289 elements in a pyramidal scan format. Parallel processing in the receive mode produces 4992 scan lines at a rate of approximately 8 frames/s. Echo data for the scanned volume is presented online as projection images with depth perspective, stereoscopic pairs, or multiple tomographic images. The authors also describe the techniques developed for the online display of volumetric images on a conventional CRT oscilloscope and show preliminary volumetric images for each display mode.

Real time volumetric ultrasound imaging system

A real time volumetric ultrasound imaging system has been developed for medical diagnosis. The scanner produces images analogous to an optical camera and supplies more information than conventional sonograms. Potential medical applications include improved anatomic visualization, tumor localization, and better assessment of cardiac function. The system uses pulse-echo phased array principles to steer a two-dimensional array transducer of 289 elements in a pyramidal scan format. Parallel processing in the receive mode produces 4992 scan lines at a rate of approximately 8 frames/second. Echo data for the scanned volume is presented as projection images with depth perspective, stereoscopic pairs, multiple tomographic images, or C-mode scans.

Digital TV tomography: Description and physical assessment

A digital TV tomography system, capable of retrospective reconstruction of multiple digital tomographic images, has been developed and its basic physical characteristics have been evaluated. The multiple tomographic images were formed through retrospective reconstruction of digital data acquired on a linear tomographic x-ray unit and an image intensifier-television system. Digital data were obtained with a series of 30 pulsed exposures during linear motion of the system. A distortion correction algorithm for the convex surface of the image intensifier was developed in order to reduce image distortion. A phantom study showed that the square-wave response at the fulcrum plane was slightly inferior to that in conventional tomography. There was also a slight decrease in the square-wave response away from the fulcrum plane and upon application of a correction algorithm, as compared with the response of the original reconstructed image at the fulcrum plane. The exposure dose for a single image was approximately half that in conventional tomography. Because of many advantages, including low exposure, short examination time, digital image manipulation, and applicability to picture archiving and communication systems, this is likely to become an important method in radiology when further technical refinements have been made.

Replacement of amiodarone by sotalol for repetitive ventricular premature beats

ability to obtain multiple tomographic type images of the heart can confirm the location of the object. In this case the echocardiographic position of the wire was quite certain while the radiographic position was more questionable. Failure to visualize pacemaker wires or catheters is quite possible, however, if the plane of the 2DE beam does not cut across the path of the catheter or wire. The spatial orientation available from 2DE along with the ability to obtain multiple tomographic images of the heart make the technique very useful for the detection of intracavitary structures. Previous reports have documented detection of transvenous pacemaker perforation and in this case the detection of epicardial pacemaker perforation is confirmed. 2DE should be considered complementary to the usual studies available for the analysis of malfunctioning pacemaker leads.

Focal-Plane Tomography Image Reconstruction

Two different tomographic scanning instruments have been interfaced to a digital computer. Digital backprojection is used to produce multiple tomographic images of radioactive distributions. Backprojection results in blur artifacts due to off-plane contributions which obscures the detail in images. The method of Chang, Macdonald, and Perez-Mendez has been applied to phantom data from both instruments, resulting in substantial blur removal and improved signal-to-noise ratios. Clinical images derived from digital back-projection of data from the Searle PHO/CON-192 Multiplane Imager are presented and compared with images from the Searle Microdot imager.