Imprint: Saunders. Published Date: 18th March Page Count: Support Center. Free Shipping Free global shipping No minimum order. Comprehensively covers CT at just the right depth for technologists — going beyond superficial treatment to accommodate all the major advances in CT.
One complete CT resource covers what you need to know! The latest information on advances in CT imaging , including: advances in volume CT scanning; CT fluoroscopy; multi-slice applications like 3-D imaging, CT angiography, and virtual reality imaging endoscopy — all with excellent coverage of state-of-the-art principles, instrumentation, clinical applications, and quality control.
Additionally, I must acknowledge the work of the 16 reviewers of this book listed separately who offered constructive comments to help improve the quality of the chapters. Their efforts are very much appreciated. The people at Elsevier, Health Professions Division, deserve special thanks for their hard work, encouragement, and support of this project. They have all offered sound and good advice in bringing this book to fruition.
I must also thank the individuals in the production department at Elsevier for doing a wonderful job on the manuscript to bring it to its final form. In particular, I am grateful to members of the production team who have worked exceptionally hard during the production of this book, especially in the page-proof stage. My family deserves special mention for their love, support, and encouragement while I worked into the many hours of the day on this manuscript.
Thanks for everything, especially for thinking that I am the greatest husband and Dad. Dave and Priscilla are now caring and devoted parents to my beautiful, smart, and overall cute and witty granddaughter Claire. This book is dedicated to her with all my love. They have honored me by writing the Foreword. Both Patrick and Rob have also been instrumental in getting me honorary senior lecturer and adjunct professor appointments at the University of Sydney and Charles Sturt University, respectively.
I am also grateful to the thousands of students who have diligently completed my CT Physics course. Thanks for all the challenging and stimulating questions. Keep on learning and enjoy the pages that follow. Palmer, Ph. Innovations are commonplace in the radiology department, and today the introduction of new ideas, methods, and refinements in existing techniques is clearly apparent. The goal of these developments is to optimize the technical parameters of the examination to provide the acceptable image quality at reduced radiation doses needed for diagnostic interpretation and, more importantly, to provide improved patient care management.
One such development, computed tomography CT , is a revolutionary tool of medicine, particularly in medical imaging. This chapter explores the meaning of CT through a brief description of its fundamental principles and historical perspectives.
It can be traced back to the early s, when a number of investigators were developing methods to image a specific layer or section of the body. A conventional tomogram is an image of a section of the patient that is oriented parallel to the film.
In , Watson developed another tomographic technique in which the sections were transverse cross sections ; this technique was referred to as transverse axial tomography. However, these images lacked enough detail and clarity to be useful in diagnostic radiology, preventing the technique from becoming fully realized as a clinical tool. Similarly, images of the human body can be reconstructed by using a large number of projections from different locations Fig. In simplified terms, radiation passes through each cross section in a specific way and is projected onto a detector that sends signals to a computer for processing.
The computer produces clear, sharp images of the internal structure of the object. Image reconstruction from projections finally found practical application in medicine in the s through the work of investigators such as Oldendorf, X-radiation Slices of object being imaged Detector Detector Detector signal Image Reconstruction from Projections CT overcomes limitations in detail and clarity by using the mathematical construct of image reconstruction from projections to produce sharp, clear images of cross-sectional anatomy.
Image reconstruction from projections had its theoretic roots in when the Austrian mathematician Radon proved it possible to reconstruct or build up an image of a 2D or 3D object from a large number of its projections from different directions. From many different locations, radiation passes through each slice or cross section of the object being imaged.
This radiation is projected onto a detector that sends signals to a computer for processing into an image that reveals the internal structure of the object.
These studies resulted in two types of CT systems: emission CT, in which the radiation source is inside the patient e. Both involve image reconstruction. Image reconstruction has also been used in diagnostic medical sonography and magnetic resonance imaging MRI. This book discusses only the fundamental principles and technology of x-ray transmission CT. In addition, the American Journal of Roentgenology accepted this term, which has now gained widespread acceptance within the radiologic community.
Throughout the remainder of this book the term computed tomography and its acronym, CT, are used. He called the technique computerized transverse axial scanning tomography in his description of the system, which was first published in the British Journal of Radiology in Since then a number of The formation of CT images by a CT scanner involves three steps: data acquisition; image reconstruction; and image display, image post processing, image storage, and communication Fig.
The term data acquisition refers to the collection of x-ray transmission measurements from the patient. Once x rays have passed through the patient, they fall onto special electronic detectors that measure the transmission values, or attenuation values. Enough transmission measurements or data must be recorded to meet the requirements of the reconstruction process. See text for further explanation. This process of translate-rotate-stop-rotate, referred to as scanning, is repeated over degrees.
The fundamental problem with this method of data collection was the length of time required to obtain enough data for image reconstruction. Later, more efficient schemes for scanning the patient were introduced see Chapter 4.
These schemes involve rotating the x-ray tube and detectors continuously as the patient moves through the scanner simultaneously. This process results in scanning a volume of tissue rather than a single slice of tissue, which was characteristic of the early CT scanners.
Acquiring a volume of tissue during the scanning is now referred to as volume scanning. The goal of volume scanning is not only to improve the volume coverage speed but to provide new tools for clinical applications. Data acquisition also involves the conversion of the electrical signals obtained from the electronic detectors to digital data, which the computer can use to process the image.
Image Reconstruction After enough transmission measurements have been collected by the detectors, they are sent to the computer for processing. For example, the image reconstruction algorithm used by Hounsfield to develop the first CT scanner was called the algebraic reconstruction technique, belonging to a class of algorithms referred to as iterative reconstruction algorithms.
Today, all new CT scanners use iterative reconstruction algorithms. These algorithms will be described in Chapter 6. A computer is central to the CT process. In general, this involves a minicomputer and associated microprocessors for performing a number of specific functions.
In some CT scanners, array processors perform high-speed calculations, and specific microprocessors perform image-processing operations. Therefore, in this regard, computers are described briefly in Chapter 7.
Image Display, Processing, Storage, Recording, and Communications After the computer has performed the image reconstruction process, the reconstructed image can be displayed and recorded for subsequent viewing and stored for later analysis.
The image is usually displayed on a cathode ray tube, although other display technologies are now available; for example, touch screen technology is used for scan setup and control in some scanners.
However, the cathode ray tube remains the best device for the display of grayscale imagery, although LCDs are now used. Image manipulation or digital image processing see Chapter 2 , as it is often referred to by some authors, has become popular in CT, and many computer software packages are now available.
Images can be modified through image post processing to make them more useful to the observer for diagnostic interpretation; for example, transverse axial images can be reformatted into coronal, sagittal, and paraxial sections. In addition, images can also be subjected to other image-processing operations such as image smoothing, edge enhancement, grayscale manipulation, and 3D image processing. Images can be recorded and subsequently stored in some form of archive.
In the past, images were recorded on x-ray film because of its wider Computed Tomography: Physical Principles, Clinical Applications, and Quality Control grayscale compared with that of instant film. Such recording is accomplished by multiformat video cameras, although laser cameras are now common in radiology departments. It is important to note, however, that film-based recording has become obsolete. CT images can be stored on magnetic tapes and magnetic disks. More recently, optical storage technology has added a new dimension to the storage of information from CT scanners.
In optical storage the stored data are read by optical means such as a laser beam. In this case, storage is referred to as laser storage. Optical storage media include at least three formats: disk, tape, and card see Chapter 7. In CT, communications refers to the electronic transmission of text data and images from the CT scanner to other devices such as laser printers; diagnostic workstations; display monitors in the radiology department, intensive care unit, and operating and trauma rooms in the hospital; and computers outside the hospital.
Electronic communications in CT require a standard protocol that facilitates connectivity networking among multimodalities CT, MRI, digital radiography, and fluoroscopy and multivendor equipment.
CT departments now operate in a PACS environment that allows the flow of CT data and images among devices and people not CT gantry and patient table CT computer 5 only in the radiology department but throughout the hospital as well. The patient is in place in the scanner opening, with appropriate positioning for the particular examination.
The technologist sets up the technical factors at the control console. Scanning can now begin. When x rays pass through the patient, they are attenuated and subsequently measured by the detectors. The x-ray tube and detectors are inside the gantry of the scanner and rotate around the patient during scanning. The detectors convert the x-ray photons attenuation data into electrical signals, or analog signals, which in turn must be converted into digital numerical data for input into the computer.
The computer then performs the image reconstruction process. The reconstructed image is in numerical form and must be converted into electrical signals for the technologist to view on a television monitor.
The data communications component is not shown. Finally, the image can be stored on optical disks. CT is so remarkable that in many cases it generates a dramatic increase in diagnostic information compared with that obtained by conventional x-ray techniques. This extraordinary invention was made possible through the work of several individuals, most notably Godfrey Newbold Hounsfield and Allan MacLeod Cormack Bates et al. He studied electronics and electrical and mechanical engineering. Godfrey Hounsfield.
In , Hounsfield was investigating pattern recognition and reconstruction techniques by using the computer. In image processing, pattern recognition involves techniques for the observer to identify, describe, and classify various features represented in an image or a signal.
From this work, he deduced that, if an x-ray beam was passed through an object from all directions and measurements were made of all the x-ray transmission, information about the internal structures of that body could be obtained. This information would be presented to the radiologist in the form of pictures that would show 3D representations. With encouragement from the British Department of Health and Social Security, an experimental apparatus was constructed to investigate the clinical feasibility of the technique Fig.
The radiation used was from an americium gamma source coupled with a crystal detector. Because of the low radiation output, the apparatus took about 9 days to scan the object. The computer needed 2. Because this procedure was too long, various modifications were made and the gamma radiation source was replaced by a powerful x-ray tube.
The results of these experiments were more accurate, but it took 1 day to produce a picture Hounsfield, To evaluate the usefulness of this machine, Dr.
Together, Hounsfield and Ambrose obtained readings from a specimen of human brain. Experiments were also done with kidney sections from pigs. The processing time for the picture was reduced to about 20 minutes.
Later, with the introduction of minicomputers, the processing time was reduced further to 4. In the first patient was scanned by this machine. The patient was a woman with a suspected brain lesion, and the picture showed clearly in detail a dark circular cyst in the brain. Hounsfield was appointed Commander of the British Empire. Hounsfield in response to several questions. After receiving this prestigious prize, he was knighted by her majesty Queen Elizabeth and became an Honorary Fellow of the Royal Academy of Engineering.
Hounsfield died on August 12, , at age 84 Isherwood, By developing the first practical CT 7 scanner, Dr. Hounsfield opened up a new domain for technologists, radiologists, medical physicists, engineers, and other related scientists. Courtesy Tufts University, Medford, Mass. Godfrey Hounsfield to the author, Euclid Seeram. He subsequently studied nuclear physics at Cambridge University before returning to the University of Cape Town as a physics lecturer.
He later moved to the United States and was on sabbatical at Harvard University before joining the physics department at Tufts University in Professor Cormack developed solutions to the mathematical problems in CT. Later, in and , he published two papers in the Journal of Applied Physics on the subject, but they received little interest in the scientific community at that time.
Cormack died at age 74, in Massachusetts on May 7, Additionally, back in South Africa, Dr. Growth First 10 Years Between and the number of CT units installed worldwide increased dramatically. Perhaps the first significant technical development came in when Dr.
Robert Ledley Fig. He holds more than 60 patents on medical instrumentation and has written several books on the use of computers in biology and medicine. Ledley won the National Medal of Technology, an honor awarded by the President of the United States for outstanding contributions to science and technology Ledley, These pioneering works were followed by the introduction of three generations a term used to refer to the method of scanning of CT scanners.
In a fourth-generation CT system was developed Fig. Robert Ledley developed the first whole-body CT scanner, the automatic computed transverse axial CT scanner. A computer capable of performing multiple functions is central to the CT system. The CT computer has undergone several changes over time see Chapter 7. Image quality is another significant development as a result of technological changes. Improvements in image quality included improved spatial resolution, decreased scan time, increased density resolution, and changes to the x-ray tube to facilitate the increased loadability required of whole-body scanners.
Increased loadability resulted in scanners capable of dynamic CT examinations that took a series of scans in rapid succession. Later-model CT scanners could operate in several modes such as the prescan localization mode, which produced a survey scan of the region of interest. Rapid reformatting of the axial scans into coronal, sagittal, and oblique sections also became possible. The goal of the DSR was to perform dynamic volume scanning to accommodate imaging of the dynamics of organ systems and the functional aspects of the cardiovascular and pulmonary systems with high temporal resolution as well as imaging anatomic details Ritman et al.
Research on this unit has since been discontinued. The difference in image quality is apparent. From Schwierz, G. Electromedica, 63, 2—7. The scanner was invented to image the cardiovascular system without artifacts caused by motion. At that time the scanner was called the cardiovascular CT scanner.
At that time, the EBCT scanner was capable of acquiring multislice images in as little as 50 and ms. The U. As of , the EBCT scanner is marketed by General Electric GE Healthcare under the name e-Speed and it now features proprietary technologies that play a significant role in imaging the heart. In October , the e-Speed CT scanner received FDA clearance and it is now capable of ms, ms, and ms true temporal resolution to produce images at up to 30 frames per second GE Healthcare, personal communication, Because nearly 20 manufacturers made CT scanners between and , a number of developments unique to particular manufacturers were also introduced.
The evolution of CT continued after , with nearly 10 manufacturers competing for the CT market. The x-ray tube and detectors rotate for degrees or less to scan one slice while the table and patient remain stationary. This slice-by-slice scanning is time-consuming; therefore, efforts were made to increase the scanning of larger volumes in less time. This notion led to the development of a technique in which a volume of tissue is scanned by moving the patient continuously through the gantry of the scanner while the x-ray tube and detectors rotate continuously for several rotations.
As a result, the x-ray beam traces a path around the patient Fig. Although some manufacturers call this beam geometry spiral CT the beam tracing a spiral path around the patient , others refer to it as helical CT the beam tracing a helical path around the patient. This book uses both terms synonymously. The idea of this approach to scanning can be traced to three sources Kalender, Willi Kalender Fig. Kalender has made significant contributions to the technical development and practical implementation of this approach to CT scanning.
His main research interests are in the areas of diagnostic imaging, particularly the development and introduction of volumetric spiral CT. His work is documented in more than scientific papers, more than original publications among these, and more than 30 patents Kalender, personal communications, , , Kalender was born in and studied medical physics in Germany. Subsequently, he continued his studies at the University of Wisconsin in the United States.
As a result, the x-ray beam traces a path beam geometry around the patient. This method of scanning the patient is referred to as helical or spiral CT.
Future CT Scanners with more than two x-ray tubes? Willi Kalender has made significant contributions to the introduction and development of volume spiral CT scanning. These scanners are called multislice CT MSCT scanners because they are based on the use of multidetector technology to scan four or more slices per revolution of the x-ray tube and detectors, thus increasing the volume coverage speed of single-slice and dualslice volume CT scanners.
The number of slices per revolution has been increasing at a steady pace, as outlined in Figure In , a slice prototype CT scanner was undergoing clinical tests and, more recently, a comparison of the doses from the slice CT scanner and a slice CT scanner has been reported Mori et al.
The number of detectors is transverse x cranio-caudal and the cone angle is about , and a gantry rotation time of 1 sec. The Human Respiratory System. Radiologic technologists must understand the technology well enough to optimize dose and image quality and provide excellent patient care.
Refresh and try again. Would you like to tell us about a lower price? Saunders- Medical — pages 0 Reviews https: Computdd added second color aids in helping you read and retain pertinent information. Statistical Atlases and Computational Models of the Heart. I purchased the Computed Tomography for Technologists book by Romans to use as a supplement and the content in that book is very well laid out and also MUCH easier to understand.
It depends on the book. What I needed and in great condition. Therapeutic Modalities in Rehabilitation, Fifth Edition. This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are as essential for the working of basic functionalities of the website.
We also use third-party cookies that help us analyze and understand how you use this website.
0コメント