Digital radiography is a form of X-ray imaging, where digital X-ray sensors are used instead of traditional photographic film. Advantages include time efficiency through bypassing chemical processing and the ability to digitally transfer and enhance images. Less radiation can be used to produce an image of similar contrast to conventional radiography. Instead of X-ray film, digital radiography uses a digital image capture device; this gives advantages of immediate image availability. Flat panel detectors are the most common kind of direct digital detectors, they are classified in two main categories: 1. Indirect FPDs Amorphous silicon is the most common material of commercial FPDs. Combining a-Si detectors with a scintillator in the detector’s outer layer, made from caesium iodide or gadolinium oxysulfide, converts X-rays to light; because of this conversion the a-Si detector is considered an indirect imaging device. The light is channeled through the a-Si photodiode layer where it is converted to a digital output signal.
The digital signal is read out by thin film transistors or fiber-coupled CCDs.2. Direct FPDs. Amorphous selenium FPDs are known as “direct” detectors because X-ray photons are converted directly into charge; the outer layer of the flat panel in this design is a high-voltage bias electrode. X-ray photons create electron-hole pairs in a-Se, the transit of these electrons and holes depends on the potential of the bias voltage charge; as the holes are replaced with electrons, the resultant charge pattern in the selenium layer is read out by a TFT array, active matrix array, electrometer probes or microplasma line addressing. Detectors based on CMOS and charge coupled device have been developed, but despite lower costs compared to FPDs of some systems, bulky designs and worse image quality have precluded widespread adoption. A high-density line-scan solid state detector is composed of a photostimulable barium fluorobromide doped with europium or caesium bromide phosphor; the phosphor detector records the X-ray energy during exposure and is scanned by a laser diode to excite the stored energy, released and read out by a digital image capture array of a CCD.
Phosphor plate radiography resembles the old analogue system of a light sensitive film sandwiched between two x-ray sensitive screens, the difference being the analogue film has been replaced by an imaging plate with photostimulable phosphor, which records the image to be read by an image reading device, which transfers the image to a Picture archiving and communication system. It is called or photostimulable phosphor plate-based radiography or computed radiography. After X-ray exposure the plate is placed in a special scanner where the latent image is retrieved point by point and digitized, using laser light scanning; the digitized images are displayed on the computer screen. Phosphor plate radiography has been described as having an advantage of fitting within any pre-existing equipment without modification because it replaces the existing film. Phosphor plate radiography was the system of choice. Since there is no physical printout, after the readout process a digital image is obtained, CR has been known as an indirect digital technology, bridging the gap between x-ray film and digital detectors.
Digital radiography has existed in various forms in the security X-ray inspection field for over 20 years and has replaced the use of film for inspection X-rays in the Security and nondestructive testing fields. DR has opened a window of opportunity for the security NDT industry due to several key advantages including excellent image quality, high POD, environmental friendliness and immediate imaging. Nondestructive testing of materials is vital in fields such as aerospace and electronics where integrity of materials is vital for safety and cost reasons. Advantages of digital technologies include the ability to provide results in real time. Dental radiography Fluoroscopy X-ray detectors
Physiology is the scientific study of the functions and mechanisms which work within a living system. As a sub-discipline of biology, the focus of physiology is on how organisms, organ systems, organs and biomolecules carry out the chemical and physical functions that exist in a living system. Central to an understanding of physiological functioning is the investigation of the fundamental biophysical and biochemical phenomena, the coordinated homeostatic control mechanisms, the continuous communication between cells; the physiologic state is the condition occurring from normal body function, while the pathological state is centered on the abnormalities that occur in animal diseases, including humans. According to the type of investigated organisms, the field can be divided into, animal physiology, plant physiology, cellular physiology and microbial physiology; the Nobel Prize in Physiology or Medicine is awarded to those who make significant achievements in this discipline by the Royal Swedish Academy of Sciences.
Human physiology seeks to understand the mechanisms that work to keep the human body alive and functioning, through scientific enquiry into the nature of mechanical and biochemical functions of humans, their organs, the cells of which they are composed. The principal level of focus of physiology is at the level of systems within systems; the endocrine and nervous systems play major roles in the reception and transmission of signals that integrate function in animals. Homeostasis is a major aspect with regard to such interactions within plants as well as animals; the biological basis of the study of physiology, integration refers to the overlap of many functions of the systems of the human body, as well as its accompanied form. It is achieved through communication that occurs in a variety of both electrical and chemical. Changes in physiology can impact the mental functions of individuals. Examples of this would be toxic levels of substances. Change in behavior as a result of these substances is used to assess the health of individuals.
Much of the foundation of knowledge in human physiology was provided by animal experimentation. Due to the frequent connection between form and function and anatomy are intrinsically linked and are studied in tandem as part of a medical curriculum. Plant physiology is a subdiscipline of botany concerned with the functioning of plants. Related fields include plant morphology, plant ecology, cell biology, genetics and molecular biology. Fundamental processes of plant physiology include photosynthesis, plant nutrition, nastic movements, photomorphogenesis, circadian rhythms, seed germination and stomata function and transpiration. Absorption of water by roots, production of food in the leaves, growth of shoots towards light are examples of plant physiology. Although there are differences between animal and microbial cells, the basic physiological functions of cells can be divided into the processes of cell division, cell signaling, cell growth, cell metabolism. Microorganisms can be found everywhere on Earth.
Types of microorganisms include archaea, eukaryotes, protists and micro-plants. Microbes are important in human culture and health in many ways, serving to ferment foods, treat sewage, produce fuel and other bioactive compounds, they are essential tools in biology as model organisms and have been put to use in biological warfare and bioterrorism. They are a vital component of fertile soils. In the human body microorganisms make up the human microbiota including the essential gut flora, they are the pathogens responsible for many infectious diseases and as such are the target of hygiene measures. Most microorganisms can reproduce and bacteria are able to exchange genes through conjugation and transduction between divergent species; the study of human physiology as a medical field originates in classical Greece, at the time of Hippocrates. Outside of Western tradition, early forms of physiology or anatomy can be reconstructed as having been present at around the same time in China and elsewhere.
Hippocrates incorporated his belief system called the theory of humours, which consisted of four basic substance: earth, water and fire. Each substance is known for having a corresponding humour: black bile, phlegm and yellow bile, respectively. Hippocrates noted some emotional connections to the four humours, which Claudius Galenus would expand on; the critical thinking of Aristotle and his emphasis on the relationship between structure and function marked the beginning of physiology in Ancient Greece. Like Hippocrates, Aristotle took to the humoral theory of disease, which consisted of four primary qualities in life: hot, cold and dry. Claudius Galenus, known as Galen of Pergamum, was the first to use experiments to probe the functions of the body. Unlike Hippocrates, Galen argued that humoral imbalances can be located in specific organs, including the entire body, his modification of this theory better equipped doctors to make more precise diagnoses. Galen played off of Hippocrates idea that emotions were tied to the humours, added the notion of temperaments: sanguine corresponds with blood.
Galen saw the human body consisting of three connected systems: the brain and nerves, which are responsible for thoughts and sensations.
A transducer is a device that converts energy from one form to another. A transducer converts a signal in one form of energy to a signal in another. Transducers are employed at the boundaries of automation and control systems, where electrical signals are converted to and from other physical quantities; the process of converting one form of energy to another is known as transduction. Transducers that convert physical quantities into mechanical ones are called mechanical transducers. Examples are a thermocouple that changes temperature differences into a small voltage, or a Linear variable differential transformer used to measure displacement. Transducers can be categorized by which direction information passes through them: A sensor is a transducer that receives and responds to a signal or stimulus from a physical system, it produces a signal, which represents information about the system, used by some type of telemetry, information or control system. An actuator is a device, responsible for moving or controlling a mechanism or system.
It is controlled by a signal from a control manual control. It is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure, or pneumatic pressure, converts that energy into motion. An actuator is the mechanism; the control system can be software-based, a human, or any other input. Bidirectional transducers convert physical phenomena to electrical signals and convert electrical signals into physical phenomena. An example of an inherently bidirectional transducer is an antenna, which can convert radio waves into an electrical signal to be processed by a radio receiver, or translate an electrical signal from a transmitter into radio waves. Another example is voice coils, which are used in loudspeakers to translate an electrical audio signal into sound and in dynamic microphones to translate sound waves into an audio signal. Active sensors require an external power source to operate, called an excitation signal; the signal is modulated by the sensor to produce an output signal.
For example, a thermistor does not generate any electrical signal, but by passing an electric current through it, its resistance can be measured by detecting variations in the current or voltage across the thermistor. Passive sensors, in contrast, generate an electric current in response to an external stimulus which serves as the output signal without the need of an additional energy source; such examples are a photodiode, a piezoelectric sensor, thermocouple. Some specifications that are used to rate transducers Dynamic range: This is the ratio between the largest amplitude signal and the smallest amplitude signal the transducer can translate. Transducers with larger dynamic range are more "sensitive" and precise. Repeatability: This is the ability of the transducer to produce an identical output when stimulated by the same input. Noise: All transducers add some random noise to their output. In electrical transducers this may be electrical noise due to thermal motion of charges in circuits.
Noise corrupts small signals more than large ones. Hysteresis: This is a property in which the output of the transducer depends on not only its current input but its past input. For example, an actuator which uses a gear train may have some backlash, which means that if the direction of motion of the actuator reverses, there will be a dead zone before the output of the actuator reverses, caused by play between the gear teeth. Electromagnetic: Antennae – converts propagating electromagnetic waves to and from conducted electrical signals magnetic cartridges – converts relative physical motion to and from electrical signals Tape head, disk read-and-write heads – converts magnetic fields on a magnetic medium to and from electrical signals Hall effect sensors – converts a magnetic field level into an electrical signal Electrochemical: pH probes Electro-galvanic oxygen sensors Hydrogen sensors Electromechanical: Accelerometers Air flow sensors Electroactive polymers Rotary motors, linear motors Galvanometers Linear variable differential transformers or rotary variably differential transformers Load cells – converts force to mV/V electrical signal using strain gauges Microelectromechanical systems Potentiometers Pressure sensors String potentiometers Tactile sensors Vibration powered generators Vibrating structure gyroscopes Electroacoustic: Loudspeakers, earphones – converts electrical signals into sound Microphones – converts sound into an electrical signal Pickup – converts motion of metal strings into an electrical signal Tactile transducers – converts electrical signal into vibration Piezoelectric crystals – converts deformations of solid-state crystals to and from electrical signals Geophones – converts a ground movement into voltage Gramophone pickups – Hydrophones – converts changes in water pressure into an electrical signal Sonar transponders Ultrasonic transceivers, transmitt
X-rays make up X-radiation, a form of electromagnetic radiation. Most X-rays have a wavelength ranging from 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 100 eV to 100 keV. X-ray wavelengths are shorter than those of UV rays and longer than those of gamma rays. In many languages, X-radiation is referred to with terms meaning Röntgen radiation, after the German scientist Wilhelm Röntgen who discovered these on November 8, 1895, credited as its discoverer, who named it X-radiation to signify an unknown type of radiation. Spelling of X-ray in the English language includes the variants x-ray, X ray. Before their discovery in 1895 X-rays were just a type of unidentified radiation emanating from experimental discharge tubes, they were noticed by scientists investigating cathode rays produced by such tubes, which are energetic electron beams that were first observed in 1869. Many of the early Crookes tubes undoubtedly radiated X-rays, because early researchers noticed effects that were attributable to them, as detailed below.
Crookes tubes created free electrons by ionization of the residual air in the tube by a high DC voltage of anywhere between a few kilovolts and 100 kV. This voltage accelerated the electrons coming from the cathode to a high enough velocity that they created X-rays when they struck the anode or the glass wall of the tube; the earliest experimenter thought to have produced. In 1785 he presented a paper to the Royal Society of London describing the effects of passing electrical currents through a evacuated glass tube, producing a glow created by X-rays; this work was further explored by his assistant Michael Faraday. When Stanford University physics professor Fernando Sanford created his "electric photography" he unknowingly generated and detected X-rays. From 1886 to 1888 he had studied in the Hermann Helmholtz laboratory in Berlin, where he became familiar with the cathode rays generated in vacuum tubes when a voltage was applied across separate electrodes, as studied by Heinrich Hertz and Philipp Lenard.
His letter of January 6, 1893 to The Physical Review was duly published and an article entitled Without Lens or Light, Photographs Taken With Plate and Object in Darkness appeared in the San Francisco Examiner. Starting in 1888, Philipp Lenard, a student of Heinrich Hertz, conducted experiments to see whether cathode rays could pass out of the Crookes tube into the air, he built a Crookes tube with a "window" in the end made of thin aluminum, facing the cathode so the cathode rays would strike it. He found that something came through, that would cause fluorescence, he measured the penetrating power of these rays through various materials. It has been suggested that at least some of these "Lenard rays" were X-rays. In 1889 Ukrainian-born Ivan Pulyui, a lecturer in experimental physics at the Prague Polytechnic who since 1877 had been constructing various designs of gas-filled tubes to investigate their properties, published a paper on how sealed photographic plates became dark when exposed to the emanations from the tubes.
Hermann von Helmholtz formulated mathematical equations for X-rays. He postulated a dispersion theory before Röntgen made his announcement, it was formed on the basis of the electromagnetic theory of light. However, he did not work with actual X-rays. In 1894 Nikola Tesla noticed damaged film in his lab that seemed to be associated with Crookes tube experiments and began investigating this radiant energy of "invisible" kinds. After Röntgen identified the X-ray, Tesla began making X-ray images of his own using high voltages and tubes of his own design, as well as Crookes tubes. On November 8, 1895, German physics professor Wilhelm Röntgen stumbled on X-rays while experimenting with Lenard tubes and Crookes tubes and began studying them, he wrote an initial report "On a new kind of ray: A preliminary communication" and on December 28, 1895 submitted it to Würzburg's Physical-Medical Society journal. This was the first paper written on X-rays. Röntgen referred to the radiation as "X"; the name stuck.
They are still referred to as such in many languages, including German, Danish, Swedish, Estonian, Japanese, Georgian and Norwegian. Röntgen received the first Nobel Prize in Physics for his discovery. There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a reconstruction by his biographers: Röntgen was investigating cathode rays from a Crookes tube which he had wrapped in black cardboard so that the visible light from the tube would not interfere, using a fluorescent screen painted with barium platinocyanide, he noticed a faint green glow from the screen, about 1 meter away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow, he found they could pass through books and papers on his desk. Röntgen threw himself into investigating these unknown rays systematically. Two months after his initial discovery, he published his paper. Röntgen discovered their medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays.
The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said "I have seen my death."The discovery of X-rays stimul
X-ray image intensifier
An x-ray image intensifier is an image intensifier that converts x-rays into visible light at higher intensity than the more traditional fluorescent screens can. Such intensifiers are used in x-ray imaging systems to allow low-intensity x-rays to be converted to a conveniently bright visible light output; the device contains a low absorbency/scatter input window aluminum, input fluorescent screen, electron optics, output fluorescent screen and output window. These parts are all mounted in a high vacuum environment within glass or more metal/ceramic. By its intensifying effect, It allows the viewer to more see the structure of the object being imaged than fluorescent screens alone, whose images are dim; the XRII requires lower absorbed doses due to more efficient conversion of x-ray quanta to visible light. This device was introduced in 1948; the overall function of an image intensifier is to convert incident x-ray photons to light photons of sufficient intensity to provide a viewable image. This occurs in several stages.
The first is conversion of x-ray photons to light photons by the input phosphor. Sodium activated Cesium Iodide is used due to its high conversion efficiency thanks to high atomic number and mass attenuation coefficient; the light photons are converted to electrons by a photocathode. A potential difference created between the anode and photocathode accelerates these photoelectrons while electron lenses focus the beam down to the size of the output window; the output window is made of silver-activated zinc-cadmium sulfide and converts incident electrons back to visible light photons. At the input and output phosphors the number of photons is multiplied by several thousands, so that overall there is a large brightness gain; this gain makes image intensifiers sensitive to x-rays such that low doses can be used for fluoroscopic procedures. X-ray image intensifiers were viewed through a microscope. Viewing of the output was via mirrors and optical systems until the adaption of television systems in the 1960s.
Additionally, the output was able to be captured on systems with a 100mm cut film camera using pulsed outputs from an x-ray tube similar to a normal radiographic exposure. The input screens range from 15 -- 57 cm, with the 23 cm, 40 cm being among the most common. Within each image intensifier, the actual field size can be changed using the voltages applied to the internal electron optics to achieve magnification and reduced viewing size. For example, the 23 cm used in cardiac applications can be set to a format of 23, 17, 13 cm; because the output screen remains fixed in size, the output appears to "magnify" the input image. High-speed digitalisation with analogue video signal came about in the mid-1970s, with pulsed fluoroscopy developed in the mid-1980s harnessing low dose rapid switching x-ray tubes. In the late 1990s image intensifiers began being replaced with flat panel detectors on fluoroscopy machines giving competition to the image intensifiers. "C-arm" mobile fluoroscopy machines are colloquially referred to as image intensifiers, however speaking the image intensifier is only one part of the machine.
Fluoroscopy, using an x-ray machine with an image intensifier, has applications in many areas of medicine. Fluoroscopy allows live images to be viewed. Common uses include orthopedics and cardiology. Less common applications can include dentistry. A system containing an image intensifier may be used either as a fixed piece of equipment in a dedicated screening room or as mobile equipment for use in an operating theatre. A mobile fluoroscopy unit consists of two units, the X-ray generator and image detector on a moveable C-arm, a separate workstation unit used to store and manipulate the images; the patient is positioned between the two arms on a radiolucent bed. Fixed systems may have a c-arm mounted with a separate control area. Most systems arranged as c-arms can have the image intensifier positioned above or below the patient, although some static in room systems may have fixed orientations. From a radiation protection standpoint, under-couch operation is preferable as it reduces the amount of scattered radiation on operators and workers.
Smaller "mini" mobile c-arms are available used to image extremities, for example for minor hand surgery. Flat Detectors are an alternative to Image Intensifiers; the advantages of this technology include: lower patient dose and increased image quality because the X-rays are always pulsed, no deterioration of the image quality over time. Despite FPD being at a higher cost than II/TV systems, the noteworthy changes in the physical size and accessibility for the patients is worth it when dealing with paediatric patients. X-ray detector Rotational angiography
Interventional cardiology is a branch of cardiology that deals with the catheter based treatment of structural heart diseases. Andreas Gruentzig is considered the father of interventional cardiology after the development of angioplasty by interventional radiologist Charles Dotter. A large number of procedures can be performed on the heart by catheterization; this most involves the insertion of a sheath into the femoral artery and cannulating the heart under X-ray visualization. The radial artery may be used for cannulation. Downsides to this approach include spasm of the artery and pain, inability to use larger catheters needed in some procedures, more radiation exposure; the main advantages of using the interventional cardiology or radiology approach are the avoidance of the scars and pain, long post-operative recovery. Additionally, interventional cardiology procedure of primary angioplasty is now the gold standard of care for an acute myocardial infarction, it involves the extraction of clots from occluded coronary arteries and deployment of stents and balloons through a small hole made in a major artery, which has given it the name "pin-hole surgery".
Angioplasty is an intervention to dilate either veins. Percutaneous coronary intervention the use of angioplasty for the treatment of obstruction of coronary arteries as a result of coronary artery disease. A deflated balloon catheter is advanced into the obstructed artery and inflated to relieve the narrowing. Various other procedures can be performed at the same time. After a heart attack, it can be restricted to complete revascularization. PCI is used in people after other forms of myocardial infarction or unstable angina where there is a high risk of further events; the use of PCI in addition to anti-angina medication in stable angina may reduce the number of patients with angina attacks for up to 3 years following the therapy, but it does not reduce the risk of death, future myocardial infarction, or need for other interventions. Valvuloplasty It is the dilation of narrowed cardiac valves. Congenital heart defect correction Percutaneous approaches can be employed to correct atrial septal and ventricular septal defects, closure of a patent ductus arteriosus, angioplasty of the great vessels.
Percutaneous valve replacement An alternative to open heart surgery, percutaneous valve replacement is the replacement of a heart valve using percutaneous methods. This is performed on the aortic valve, pulmonary valve and the mitral valve Percutaneous valve repair An alternative to open heart surgery, percutaneous valve repair is performed on the mitral valve using the MONARC system or MitraClip system Coronary thrombectomy Coronary thrombectomy involves the removal of a thrombus from the coronary arteries. Open heart surgery of the heart is performed by a cardiothoracic surgeon; some interventional cardiology procedures are performed in conjuction with a cardiothoracic surgeon. In the US and Canada, interventional cardiology requires a minimum of 7 years of post-graduate medical education and up to 9 years of post-graduate medical education for those wanting to perform advanced structural heart procedures. Undergraduate degree Medical degree Internal Medicine residency Cardiology fellowship Interventional Cardiology fellowship Structural Heart Intervention fellowship Interventional radiology Vascular surgery Catheter Cannula Stent Restenosis Society for Cardiovascular Angiography & Interventions Angioplasty.
Org European Association of Percutaneous Cardiovascular Interventions Interventional Portal: Relevant links for interventional cardiologists Interventional Cardiology Review
Radiographers known as radiologic technologists, diagnostic radiographers and medical radiation technologists are healthcare professionals who specialise in the imaging of human anatomy for the diagnosis and treatment of pathology. Radiographers are infrequently, always erroneously, known as x-ray technicians. In countries that use the title radiologic technologist they are informally referred to as techs in the clinical environment; the term radiographer can refer to a therapeutic radiographer known as a radiation therapist. Radiographers work in both public healthcare and private healthcare and can be physically located in any setting where appropriate diagnostic equipment is located, most in hospitals; the practice varies from country to country and can vary between hospitals in the same country. Radiographers are represented by a variety of organizations worldwide, including the International Society of Radiographers and Radiologic Technologists which aims to give direction to the profession as a whole through collaboration with national representative bodies.
Radiography's origins and fluoroscopy's origins can both be traced to 8 November 1895, when German physics professor Wilhelm Röntgen discovered the X-ray and noted that, while it could pass through human tissue, it could not pass through bone or metal. Röntgen referred to the radiation as "X", he received the first Nobel Prize in Physics for his discovery. There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a reconstruction by his biographers: Röntgen was investigating cathode rays using a fluorescent screen painted with barium platinocyanide and a Crookes tube which he had wrapped in black cardboard to shield its fluorescent glow, he noticed a faint green glow from the screen, about 1 metre away. Röntgen realized some invisible rays coming from the tube were passing through the cardboard to make the screen glow: they were passing through an opaque object to affect the film behind it. Röntgen discovered X-rays' medical use when he made a picture of his wife's hand on a photographic plate formed due to X-rays.
The photograph of his wife's hand was the first photograph of a human body part using X-rays. When she saw the picture, she said, "I have seen my death."The first use of X-rays under clinical conditions was by John Hall-Edwards in Birmingham, England on 11 January 1896, when he radiographed a needle stuck in the hand of an associate. On 14 February 1896, Hall-Edwards became the first to use X-rays in a surgical operation; the United States saw its first medical X-ray obtained using a discharge tube of Ivan Pulyui's design. In January 1896, on reading of Röntgen's discovery, Frank Austin of Dartmouth College tested all of the discharge tubes in the physics laboratory and found that only the Pulyui tube produced X-rays; this was a result of Pulyui's inclusion of an oblique "target" of mica, used for holding samples of fluorescent material, within the tube. On 3 February 1896 Gilman Frost, professor of medicine at the college, his brother Edwin Frost, professor of physics, exposed the wrist of Eddie McCarthy, whom Gilman had treated some weeks earlier for a fracture, to the X-rays and collected the resulting image of the broken bone on gelatin photographic plates obtained from Howard Langill, a local photographer interested in Röntgen's work.
X-rays were put to diagnostic use early. Indeed, Marie Curie pushed for radiography to be used to treat wounded soldiers in World War I. Many kinds of staff conducted radiography in hospitals, including physicists, physicians and engineers; the medical speciality of radiology grew up over many years around the new technology. When new diagnostic tests were developed, it was natural for the radiographers to be trained in and to adopt this new technology. Radiographers now perform fluoroscopy, computed tomography, ultrasound, nuclear medicine and magnetic resonance imaging as well. Although a nonspecialist dictionary might define radiography quite narrowly as "taking X-ray images", this has long been only part of the work of "X-ray Departments", Radiologists. Radiographs were known as roentgenograms, while Skiagrapher was used until about 1918 to mean Radiographer; the history of magnetic resonance imaging includes many researchers who have discovered NMR and described its underlying physics, but it is regarded to be invented by Paul C.
Lauterbur in September 1971. The factors leading to image contrast had been described nearly 20 years earlier by Erik Odeblad and Gunnar Lindström. In 1950, spin echoes and free induction decay were first detected by Erwin Hahn and in 1952, Herman Carr produced a one-dimensional NMR spectrum as reported in his Harvard PhD thesis. In the Soviet Union, Vladislav Ivanov filed a document with the USSR State Committee for Inventions and Discovery at Leningrad for a Magnetic Resonance Imaging device, although this was not approved until the 1970s. By 1959, Jay Singer had studied blood flow by NMR relaxation time measurements of blood in living humans; such measurements were not introduced into common medical practice until the mid-1980s, although a patent for a whole-body NMR machine to measure blood flow in the human body was filed by Alexander Ganssen in early