Ct is based on the fundamental principle that the density of the tissue passed by the xray beam can be measured from the calculation of the attenuation coefficient. Ct computed tomography ct is a technique that uses an xray beam to generate images that have a very good resolution to demonstrate anatomy. Ct was introduced into clinical practice into 1971 with a scan of a cystic frontal lobe tumor on a patient at atkinson morley hospital in wimbledon united kingdom. The reader will gain a complete understanding of how a ct scanner functions and will become familiar with the terms and definitions important to a working understanding of the science of computed tomography. Physics of imaging systems basic principles of magnetic.
Basic principles of computed tomography physics and. The term computed tomography, or ct, refers to a computerized xray imaging procedure in which a narrow beam of xrays is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machines computer to generate crosssectional imagesor slicesof the body. For example, ct has become a useful screening tool for detecting possible tumors or lesions within the abdomen. Spiral computed tomography, or helical computed tomography, is a computed tomography ct technology in which the source and detector travel along a helical path relative to the object. Computed tomography is a specific use of ionizing radiation that plays an important diagnostic role in pregnancy, and its use increased by 25% per year from 1997 to 2006 1. Basic interpretation of ct scans most of the ct pictures are nonspecific ct pictures are depending on the density of the structures. Since its introduction in 1972, xray computed tomography ct has evolved into an essential diagnostic imaging tool for a continually increasing variety of clinical applications. An introduction to petct imaging1 vibhu kapoor, md barry m. Pet ct integrated pet with ct in a single unit pet. Ct image is a product of complex calculation based on backprojection reconstruction algorithm. This book provides an overview of the evolution of ct, the mathematical and physical aspects of the technology, and the fundamentals of image reconstruction using algorithms. The basic principles of computed tomography and magnetic.
This is an illustration of a patient moving into the bore of a ct scanner. Whiting introduction slightly more than three decades old, computed tomography ct continues to advance rapidly in both imaging performance and widening clinical applications. Ct offers very good contrast of bone to soft tissue and thus can have novel. Using this principle, ct allows the reconstruction of the density of the body, by twodimensional section perpendicular to the axis of the acquisition system. Ct scans are created using a series of xrays, which are a form of radiation on the electromagnetic spectrum. By moving the xray tube and the film such that the central ray from the tube passesthrough a single point in the imageplane fulcrum plane, information from the fulcrum plane aa would be imaged sharply o the film, but data from other planes bb would be blurred. Basic principles of ct scanners and image reconstruction.
Basic principle of mri the hydrogen 1h atom inside body possess spin in the absence of external magnetic field, the spin directions of all atoms are random and cancel each other. In modern 3rdgeneration ct systems with fanbeam geometry, the minimum amount of scan data needed for reconstruction of axial slices is a socalled partial scan. Ct scans can be used to identify disease or injury within various regions of the body. On the opposite side of the volume is a dosimeter which measures the amount of ionising radiation reaching it. Basic principles and applications of 18 ffdgpet ct in oral and maxillofacial imaging. This book provides an overview of the evolution of ct. The maximum energy of the photons is defined by the voltage, whereas the mean energies are significantly lower and their differences smaller than one may expectfor 76 and 56kev mean energy, keywords. Tabakov, 1999 ct scan is a type of medical examination that uses xrays and computer processing to create sectional images of the body to provide more efficient results than xrays. Basic principles of petct inspector of electromedic.
Here is a description about image acquisition and the image formation processes. Positron emission tomography pet is a nuclear medical imaging technique for quantitative measurement of physiologic parameters in vivo an overview of principles and applications can be. In clinical practice the interslice distance generally lies in the range between 0 and 10mm, and the pitch factor between 1 and 2. It is hoped that this pet ct book will serve as an invaluable educational tool for all professionals working in pet ct departments and that it will contribute to the quality of their daily work. This was the impetus for the development of combined pet ct tomographs see e. The term computed tomography derives from computed with computer, tomo to cut, and graphy pictures. The ct x ray tube typically with energy levels between 20 and 150 kev, emits n photons monochromatic per unit of time. Computed tomography, more commonly known as a ct or cat scan, is a diagnostic medical imaging test. The ct image is not a real shade like in classical radiography, but a picture which represents with some probability 95% the similarity between the real object and its calculated ct image.
The ct scanner computed tomography is an imaging technique that produces crosssectional images, representing in each pixel the local xray attenuation properties of the body. Pet ct has particular value in cancer diagnosis and manage ment but it does have value in many other pathologies, too. By moving the xray tube and the film such that the central ray from the tube passesthrough a single point in the imageplane fulcrum plane, information. The goal of this book was not simply to summarize currently available ct. Xray computed tomography ct has experienced tremendous growth in recent years, in terms of both basic technology and new clinical applications. This allows extraction of accurate information from pet images. Digital imaging science and technology to enhance healthcare in the developing countries slavik tabakov september 1 october, 2010 kings college london united kingdom basic principles of ct. Ct the pitch factor is the ratio of the couch increment per rotation to the nominal slice thickness at the axis of rotation. Branstetter 3 1 department of oral diagnosis and polyclinics, faculty of dentistry, the hong kong university.
Torok, md cancer is one of the leading causes of morbidity and mortality in developed countries such as the united states. Ct offers very good contrast of bone to soft tissue and thus can. When placed in an external magnetic field, the spins align with the external field. Like traditional xrays, it produces multiple images or pictures of the inside of the body. Basic ct scanner components gantry xray tube detector control. History 1924 mathematical theory of thomographic image reconstructions johann radon 1930 conventional tomography a. Ct can detect tissue density differences as low as what. I also hope that this book will bene%t those with no or limited pet ct experience, helping them to start to develop their understanding of the %eld. By applying an rotating magnetic field in the direction. Basic principles in computed tomography ct springerlink.
Basic principles of computed tomography flashcards quizlet. Computed tomography ct donut shaped machine uses xray energy and computer generation of images advantages sensitive to slight density difference cross sectional anatomy attenuation. Computed tomography ct and magnetic resonance imaging mri are the most widely used crosssectional imaging methods used in medicine. Tissue density differences as low as 1% or less can be detected with ct. Basic principles of ct ct imaging system moves around the body part at a fixed location attenuation information obtained in multiple planes reconstruct of this attenuation information into a simple grid. Computed tomography ct scans can detect pathology that may be missed on a conventional chest radiograph. Ct scanning techniques and applications intechopen. Jun 28, 2014 this video presentation explains the basic principle of ct scan. The combination of pet and ct not only eliminates the requirement to perform a lengthy pet transmission scan, but also provides accurately registered anatomical and functional images. To minimize radiation dose and generation of background scatter, the xray beam is collimated by an aperture into a thin fan beam.
A ct scan is a form of xraying that involves a large xray machine. In these devices, a pet scanner and an xray ct are built in the same gantry, allowing the acquisition of pet as well as ct data with minimum time delay. Computed tomography ct is a noninvasive imaging tool that provides 3dimensional 3d images of the internal organs. The scanner emits xrays towards the patient from a variety of angles and the detectors in the scanner. Computed tomography ct and magnetic resonance imaging mri are the most wide ly used crosssectional imaging methods used in medicine. For ct scanners, the beam is typically a few millimeters thick in the. Ct scans allow doctors to see crosssectional ct scan images slices of your body. Ct uses multiple pencil or fan beams of kilovoltage photons that pass through a desired volume from multiple angles usually over 180 degrees. The basics of ct ct imaging chain system components acquisition methods image quality applications 632014 hareesha n g, dept of aero engg, dsce 2 3. The term computed tomography, or ct, refers to a computerized xray imaging procedure in which a narrow beam of xrays is aimed at a patient and quickly. Guidelines for diagnostic imaging during pregnancy and. Basic principles of computed tomography physics and technical. Petct medical imaging technique both systems in one gantry aquired image combined into a coregistered image functional imaging by pet anatomical imaging by ctscanner by eng. Only minute amounts of imaging substrate need to be injected tracer principle.
This presentation gives an information about basic principles of ct scanning covering the syllabus of non destructive testing slideshare uses cookies to improve functionality and performance. A pictorial essay galal omami, 1 dania tamimi, 2 and barton f. Ct uses xrays to generate crosssectional, twodimensional images of the body. The emitted xrays form a beam which passes through the layer of. Feb 26, 2019 computed tomography ct is a noninvasive imaging tool that provides 3dimensional 3d images of the internal organs.
Bohrs correspondence principle lim qm classical physics n 8 m0 proton correspondence principle. A computerized tomography ct scan combines a series of xray images taken from different angles around your body and uses computer processing to create crosssectional images slices of the bones, blood vessels and soft tissues inside your body. Petct scanprinciples and basics linkedin slideshare. The historical background, developments, and innovations in ct are presented from the general perspective of medical imaging. Complex clinical decisions about treatment of oncologic patients are largely guided by imaging. How ct scans work using only basic high school mathematics. A ct scan shows your bodys organs, bones, and tissues in greater detail than regular xrays do. To understand the basic principles of ct, one may begin with the operation of this original emi mark i firstgeneration ct scanner.
Basic principle of ct and ct generations linkedin slideshare. For your ct scan, you will receive a contrast enhancing agent by intravenous line iv, which helps produce an even clearer image. Basic principles of ct scanners and image reconstruction indico. The interslice distance can be negative for overlapping scans which in helical ct. Imaging before ct entire body areas were inaccessible to radiography brain, mediastinum, retroperitoneum diagnostic procedures showing better detail in these areas were potentially harmful. This first article covers the fundamental principles of ct, including the basic geometry of the ct scan process, the nature of the measurements made by ct detectors, a qualitative explanation of the image reconstruction process, the evolution of ct technology the 4 generations of ct from the emi firstgeneration scanner through modern slip. Use of ct and associated contrast material should not be withheld if clinically indicated, but a thorough discussion of risks and benefits should take. The ct image is not a real shade like in classical radiography, but a picture which represents with some probability 95% the similarity between the real object and its calculated ct. The focus of our discussion will be the principles of 2. Basic principles of ct scanning linkedin slideshare. Referral forms and ct scan reports were obtained for 460 mhi patients from a sample of 497 patients, calculated by using the equation for estimating a single proportion from a large.
The crosssectional images generated during a ct scan can be reformatted in multiple planes. The first experimental setup of hounsfield in 1970 worked with the socalled translationrotation principle. Clinicians need to be aware of the potentially harmful radiation that patients are exposed to, with each individual ct scan that is performed. A ct scan, or computed tomography scan is a medical imaging procedure that uses computerprocessed combinations of many xray measurements taken from different angles to produce crosssectional tomographic images virtual slices of specific areas of a scanned object, allowing the user to see inside the object without cutting. Basic principles of computed tomography physics and technical considerations kyongtae t. Typical implementations involve moving the patient couch through the bore of the scanner whilst the gantry rotates. Ct is short for computed tomography ct uses xrays and a computer to make an image of sections of your body. The goal of this book was not simply to summarize currently available ct imaging techniques but also to provide clinical perspectives, advances in hybrid technologies, new applications other than medicine and an. Ct mri ct transmission tomography mri direct tomography xray tube detector. Physical principles and technology of clinical pet imaging. Basic principles and applications of 18ffdgpetct in. Classical longitudinal tomography used this principle.
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