Showing papers on "Imaging technology published in 1988"

The Physics of Medical Imaging

Abstract: Introduction - and some challenging questions. In the beginning. Diagnostic radiology with x-rays: Introduction The imaging system and image formation Photon interactions Important physical parameters X-ray tubes Image receptors Digital radiology. Quality assurance and image improvement in diagnostic radiology with x-rays. Introduction to quality assurance: Basic quality-assurance tests for x-ray sets Specific quality-assurance tests Data collection and presentation of the results Summary of quality assurance Improvement in radiographic quality Scatter removal Contrast enhancement Summary of methods of image enhancement. X-ray transmission computed tomography: The need for sectional images The principles of sectional imaging Fourier-based solutions: The method of convolution and backprojection Iterative methods of reconstruction Other considerations. Clinical applications of X-ray computed tomography in radiotherapy planning: X-ray computed tomography scanners and their role in planning Non-standard computed tomography scanners. The physics of radioisotope imaging: Introduction Radiation detectors Radioisotope imaging equipment Radionuclides for imaging The role of computers in radioisotope imaging Static and dynamic planar scintigraphy Emission computed tomography Quality control and performance assessment of radioisotope imaging equipment Clinical applications of radioisotope imaging. Diagnostic Ultrasound: Introduction Basic physics Engineering principles of ultrasonic imaging Clinical applications and biological aspects of diagnostic ultrasound Research topics. Spatially localised nuclear magnetic resonance: Introduction The development of nuclear magnetic resonance Principles of nuclear magnetic resonance Nuclear magnetic resonance pulse sequences Relaxation processes and their measurement Nuclear magnetic resonance image acquisition and reconstruction Spatially localised spectroscopy Instrumentation Nuclear magnetic resonance safety. Physical aspects of infrared imaging: Introduction Infrared photography Transilluminaton Infrared imaging Liquid-crystal thermography Microwave thermography. Imaging of tissue electrical impedance: The electrical behaviour of tissue Tissue impedance imaging Suggested clinical applications of applied potential tomography. Imaging by diaphanography: Clinical applications Physical basis of transillumination Experimental arrangements. The mathematics of image formation and image processing: The concept of object and image The relationship between object and image The general image processing problem Discrete Fourier representation and the models for imaging systems The general theory of image restoration Image sampling Two examples of image processing from modern clinical practice Iterative image processing. Perception and interpretation of images. Introduction The eye and brain as a stage in an imaging system Spatial and contrast resolution Perception of moving images Quantitative measures of investigative performance. Computer requirements of imaging systems: Single- versus multi-user systems Generation and transfer of images Processing speed Display of medical images Three-dimensional image display: methodology Three-dimensional image display: clinical applications. Epilogue: Introduction The impact of radiation hazard on medical imaging practice Attributes and relative roles of imaging modalities References. Index.

Three Dimensional X-Ray Computed Tomography in Materials Science

Abstract: Imaging is the cornerstone of materials characterization. Until the middle of the present century, visible light imaging provided much of the information about materials. Though visible light imaging still plays an extremely important role in characterization, relatively low spatial resolution and lack of chemical sensitivity and specificity limit its usefulness.The discovery of x-rays and electrons led to a major advance in imaging technology. X-ray diffraction and electron microscopy allowed us to characterize the atomic structure of materials. Many materials vital to our high technology economy and defense owe their existence to the understanding of materials structure brought about with these high-resolution methods.Electron microscopy is an essential tool for materials characterization. Unfortunately, electron imaging is always destructive due to the sample preparation that must be done prior to imaging. Furthermore, electron microscopy only provides information about the surface of a sample. Three dimensional information, of great interest in characterizing many new materials, can be obtained only by time consuming sectioning of an object.The development of intense synchrotron light sources in addition to the improvements in solid state imaging technology is revolutionizing materials characterization. High resolution x-ray imaging is a potentially valuable tool for materials characterization. The large depth of x-ray penetration, as well as the sensitivity of absorption crosssections to atomic chemistry, allows x-ray imaging to characterize the chemistry of internal structures in macroscopic objects with little sample preparation. X-ray imaging complements other imaging modalities, such as electron microscopy, in that it can be performed nondestructively on metals and insulators alike.

The value of imaging technology to patients' health

Abstract: The ultimate goal of imaging research, indeed, all medical research, is the improvement of human health. However, the technologic nature of our discipline often results in research that assesses a technology or the application of a technology in terms of the information it provides rather than its relationship to care of patients. Dr. Rosenquist’s paper [i ] describes an example of how assessing a technology solely on the basis of the information it provides can be misleading with regard to the effects of that technology on patients’ health. In a broad sense, nearly all of our literature deals with imaging technology assessment. An unfortunate proportion of imaging publications are retrospective, without suitable controls or verification of diagnoses, and they employ dubious or irreproducible measures of efficacy. In evaluating the other publications, we can consider a five-stage hierarchy of imaging technology assessment: imaging efficacy, diagnostic efficacy, therapeutic efficacy, evaluation of the patients’ outcomes, and cost-effectiveness assessment. Imaging efficacy is the level of assessment most commonly encountered in prospective imaging research. Evaluation of imaging efficacy is typified by the work of Abu-Yousef et al. [2], who sought to determine the potential of sonography in identifying patients with appendicitis. This level of assessment is an important and necessary first step in assessing the value of an imaging technology. However, as Dr. Rosenquist has shown, little relationship may exist between imaging efficacy and providing benefits to patients. Indeed, only a few imaging studies have sought to develop a link between advances in imaging technology and benefits to patients. This lack of data has provided a rationale for often misguided technology regulation and reimbursement conmisguided technology regulation and reimbursement constraints. Moreover, the absence of reliable information puts radiologists at a disadvantage in selecting and using technology, especially in an environment that increasingly puts us and our associates at financial risk for applying technologies that do not result in cost-effective care. Levels two through five of the assessment hierarchy potentially could contribute to an information base that would correct these deficiencies. Level two is diagnostic efficacy. Studies dealing with diagnostic efficacy seek to determine the importance of the use of a technology in establishing or ruling out a diagnosis. An example of a measure of diagnostic efficacy that has been used successfully in assessing applications of imaging technology is the log likelihood ratio [3]:

The determination of death and the changing role of medical imaging.

Abstract: Laws and standards of medical practice with respect to the determination of death have changed dramatically as knowledge of the human body and its detailed cellular functions have increased. This article describes legal and medical advances in the determination of death emphasizing the role of modern imaging technology in this critical determination.

Measure theoretic imaging, with an example employing magnetic resonance input

Abstract: We present a new medical imaging principle which allows reconstruction of images (from the output of a general digital imaging technology) whose contrast is based on a fundamentally different mathematical mechanism than that of standard images. These images have the useful property that they are capable of exhibiting high contrast between tissues which in currently produced images necessarily have low contrast. The meaning of these images, and their general place in the context of present image generation techniques, is most naturally expressed in the formalism of measure theory. The property actually imaged is derived from a probability measure associated with the mapping which expresses the output of the imaging technology. It also has a nonprobabilistic interpretation as a generalization of the Jacobian, specifically, the Radon-Nikodym derivative. In particular, unlike standard images, contrast is independent of the metric in the space of physical signals that the imaging technology associates with points of the region to be imaged. Images based on this approach using magnetic resonance input are presented.