X ray tubes are designed and constructed to maximize x ray production and to dissipate heat as rapidly as possible. Xray tube design filament is heated, releasing electrons via thermionic emission v f 10v, i f 4a, resulting in t2000oc x rays are produced by highspeed electrons bombarding the target typically modern x ray tubes come in many shapes and sizes, normally they are of the glass or metalceramic tube envelope style. Increasing rates of patient obesity mean that the size of the average patient is an added. Development of xray tubes fundamentals of xray physics. Why is heat conduction cooling used in modern high performance x ray tubes. Xrays are produced in the xray tube by accelerating electrons to a high velocity by an electrostatic field and then suddenly stopping them by collision with a solid body, the socalled target, interposed in their path. The modern techniques of tube design have allowed for smaller tubes, extended tube life, and more efficient and stable operation. Bone xrays are the fastest and easiest way for your doctor to view. Incident xray air kerma rateat the input phosphor typically 927 cd. A schematic diagram of an x ray tube is shown in figure 2. The uniform x ray beam emitted from the source is modulated as it passes through the human body and these changes are recorded on the film. Supplies power to the x ray tube so that x rays are produced. Xray tube and generator basic principles and construction indico. Stipulate the x ray tube heat unit storage capacity.
Production of xrays x rays were discovered by roentgen in 1895 while studying cathode rays stream of electrons in a gas discharge tube. Xray tube, also called roentgen tube, evacuated electron tube that produces x rays by accelerating electrons to a high velocity with a highvoltage field and causing them to collide with a target, the anode plate. The limits and achievements of modern xray tube constructions. For the love of physics walter lewin may 16, 2011 duration.
Most x ray tubes in use today are filled with a vacuum. Xray tube design filament is heated, releasing electrons via thermionic emission v f 10v, i f 4a, resulting in t2000oc x rays are produced by highspeed electrons bombarding the target typically pdf literature. Modern generators provide control of the anode temperature by. In contrast to other sources of ionizing radiation, xrays are only produced as long as the xray tube is energized. The availability of this controllable source of x rays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. Tungsten is the dominating anode material and is in modern xray tubes often mixed with renium zw 74.
The availability of this controllable source of xrays created the field of radiography, the imaging of partly opaque objects with penetrating radiation. Consequently, one major step in the development of x ray tubes was to place a metallic target inside the tube and direct the electrons to it instead of allowing them to interact with the glass wall. The most current ct scanning techniques place a high heat load on the ct scanner xray tube, due to the need for high tube current values to provide enough photons in the image, when scanning with fast rotations and fine slices. X ray collimator must be of high quality to minimize radiation outside the selected field of radiation. The diagram on the right shows the xray tube by itself. The patient could then be placed into the beam while others were kept away from it. A remote control device that permits current to flow through the circuit. On the other hand, teledyne dalsa will show its remote radeye hr detector, a slim 33 x 22 mm 20 m detector ideal for inspections in tight or. This entirely new variety of x ray tube was invented in 19 by the american electrical engineer william coolidge 18731975. Xray radiography bone bone xray uses a very small dose of ionizing radiation to produce pictures of any bone in the body. Theory the subdiscipline of xray physics involves a certain amount of nomenclature and notation that you.
A schematic diagram of a typical therapy x ray tube is shown in fig. Bone xrays are the fastest and easiest way for your doctor to view and assess bone fractures, injuries and joint abnormalities. A powder xray diffractometer consists of an xray source usually an xray tube, a sample stage, a detector and a way to vary angle the xray is focused on the sample at some angle. Incorporate appropriate circuitry to increase x ray production efficiency.
Jan 19, 2017 externalparts tube support glassmetal envelop protective housing 4. The xray tube is a relatively simple electrical device typically containing two principle elements. An xray tube is a vacuum tube that converts electrical input power into xrays. The anode can be made smaller while maintaining high performance 4.
The tube consists of a source of electrons, the cathode, which is usually a heated filament, and a thermally rugged anode, usually of tungsten, which is enclosed in an evacuated. This animation shows the function of the components of a modern xray tube. Medical xrays come from a machine that is designed to emit radiation on command. This was good from a maintenance view but as the x ray target cannot be rotated or changed the. X ray tube, evacuated electron tube that produces x rays by accelerating electrons to a high velocity with a highvoltage field and causing them to collide with a target, the anode plate. The rest is a menu of possible studies you can pursue as time permits. The type of x ray tube used most widely in all fields is the sealedoff hotcathode tube with a watercooled anode and an electrostatic electronfocusing system figure 1. Schematic diagram of an entirely new variety of x ray tube from william coolidges 19 patent application. Chapter 5 treatment machines for external beam radiotherapy. Xrays are produced whenever highspeed electrons are suddenly brought to rest, some of their kinetic energy, at least, being converted into the electromagnetic radiation. In the late 1800s there were many scientists of that era hat were experimenting with electricity which at that time was a new phenomena. An xray tube functions as a specific energy converter, receiving the electrical energy and converting it into two other forms of energy. Consequently, one major step in the development of xray tubes was to place a metallic target inside the tube and direct the electrons to it instead of allowing them to interact with the glass wall. Closed or sealed x ray tube early x ray systems used within the electronics industry had a closed or sealed x ray tube.
Modern diagnostic xray sources, technology, manufacturing, reliability. History of development of modern xray tube presented by. Although a modern xray tube bears no very obvious resemblance to the discharge tube of rontgens apparatus, the basic mechanism of x ray production remains the same. In conventional radiography, x rays passed through the human body are absorbed, which causes attenuation of the incident beam. In fact, there is a danger in supplying alternating current because if a flow of electrons occurs in the wrong direction the tube may be damaged beyond repair. The history of how xrays were discovered is interesting. This very specific energy conversion takes place in the xray. There are three major components that we will be discussing.
An x ray tube functions as a specific energy converter, receiving the electrical energy and converting it into two other forms of energy. The x ray beam used in the medical field which contains a broad band of frequencies. Anode and cathode of an xray tube are enclosed in a vacuum glass tube or. Modern improvements on the xray tube, introduced by william coolidge, include using a hot cathode and vacuum tube to increase efficiency, water cooling to prevent overheating the anode, and lead pb shielding to absorb xrays except at the beryllium be windows, which transmit them outward. Apr 21, 2018 for the love of physics walter lewin may 16, 2011 duration. Characteristic xrays are emitted when outershell electrons fill a vacancy in the inner shell of an atom, releasing xrays in a pattern that is characteristic to each element. It is commonly used to diagnose fractured bones or joint dislocation. Xrays make up xradiation, a form of highenergy electromagnetic radiation. In contrast to other sources of ionizing radiation, x rays are only produced as long as the x ray tube is. Device used to end the exposure at an accurately measured preset time. It was a fit and forget item with the tube sealed for life.
Modern xray imaging requires a small focal spot and high xray fluence rates number. An x ray tube is a vacuum tube that converts electrical input power into x rays. The x ray tube is a relatively simple electrical device typically containing two principle elements. In that same year coolidge developed the technique for making fine wire out of tungsten a notoriously nonductile metal.
Permit the radiographer to adjust technical factors. Teledyne icm will highlight the cp200d, the lightest 200 kv portable xray generator on the market, as well as the cp160b, a compact 160 kv battery operated portable xray source with small focal spot. Most modern xray machines are provided with two filaments mounted side by. Photon energy ev 705 710 715 720 725 730 normalized intensity a. History of xray tube development types of xray tube components of xray tube. The early x ray tube of rsntgen, the crookes tube, was greatly improved by campbellswinton through the introduction of a platinum target and by jackson, who turned to account a former discovery of crookes and used a concave cathode. For special purpose rooms such as those used for cardiovascular imaging, extra heat capacity is needed to allow angiographic runs, sequences of higherdose radiographic. X ray tubes operates best when recieving direct current from the cathode to the anode. As compared to early gas filled x ray tubes, modern tubes are of the high vacuum style. The main components of a radiotherapeutic x ray machine are. He observed that another type of radiation was produced presumably by the interaction of electrons with the glass walls of the tube that could be detected outside the tube. Xray tubes are designed and constructed to maximize xray production and to dissipate heat as rapidly as possible.
Heat is considered the undesirable product of this conversion process. The tube consists of a source of electrons, the cathode, which is usually a heated filament, and a thermally. This entirely new variety of xray tube was invented in 19 by the american electrical engineer william coolidge 18731975. The publication of jens alsnielsen and des mcmorrows elements of modern xray physics is a defining moment in the field of synchrotron radiation a welcome addition to the bookshelves of synchrotronradiation professionals and students alike the text is now my personal choice for teaching xray physics physics today, 2002. She is manipulating the field size by adjusting a device called the collimator which is attached to the xray tube housing. The vacuum tube that utilizes this phenomenon in the generation of xrays is called an xray tube. Some current, low cost systems still use this technology. In modern xray systems, heat loading is monitored by a system computer. The highvoltage generator and xray tube used in most fluoroscopy systems is similar in design and construction to tubes used for general radiographic applications. To get a high relative amount of xray energy, the anode material should be of high atomic number. Stipulate the heat unit and anode storage capacity. X ray tubes are used in x ray diffraction analysis, x ray spectral analysis, flaw detection, roentgen diagnosis, roentgenotherapy, x ray microscopy, and microradiography. The rectangular looking device just above the collimator is the housing for the xray tube. Xrays definition block diagram and working of xray.
The switch that generates the power to the xray tube. Xray tube and generator basic principles and construction. It is intended to familiarize you with the equipment and some of the basic physics of x rays. Xray wavelengths are shorter than those of uv rays and typically longer than those of gamma rays. Xray tubes operates best when recieving direct current from the cathode to the anode. Although a modern xray tube bears no very obvious resemblance to the discharge tube of rontgens apparatus, the basic mechanism of xray production remains the same. Jun, 2005 x rays are produced by bombarding a metal target by high energy electrons. Thus, to produce sufficient xray output for diagnostic imaging, the xray tube must. Most xray tubes in use today are filled with a vacuum. Oct 20, 2016 although a modern x ray tube bears no very obvious resemblance to the discharge tube of rontgens apparatus, the basic mechanism of x ray production remains the same. The electrons producing the x ray beams in the x ray tube coolidge.
Nearly all contemporary x ray tubes are variations of the coolidge tube. With modern xray diffractometers the signals are converted into peaks intensity 2. Xrays emerged from coolidges tubes only through an aperture in the lead shielding. Heat radiation is not effective at high temperatures 3. Without a doubt, the single most important event in the progress of radiology was the invention by william coolidge in 19 of what came to be known as the coolidge xray tube. As the electrical current flows through the tube from cathode to.
Theory the subdiscipline of x ray physics involves a certain amount of nomenclature and notation that you. Boost the voltage to the necessary range of x ray production. The vacuum tube that utilizes this phenomenon in the generation of x rays is called an x ray tube. Improved technologies lead to challenging tasks for ct scanner xray tubes.
Advances in xray tube technology by igmar grewar and keith bryant closed or sealed xray tube early xray systems used within the electronics industry had a closed or sealed xray tube. An electronic device used for the generation of xrays. Later, beam limiting devices like the modern one depicted in figure 15. X rays are produced whenever highspeed electrons are suddenly brought to rest, some of their kinetic energy, at least, being converted into the electromagnetic radiation. X ray tube and housing assembly are quite heavy,and therefore require a support mechanism so that the radiologic technologist can position it. The rediscovery of velocity modulation at stanford would probably have been no more successful than heils initial research in russia, except for the rumbatron.
918 173 1224 324 228 246 1251 862 577 887 735 1047 458 842 1143 596 1201 697 1291 114 1368 1048 48 1149 990 819 274 1343 58 1193 989 1344 977