Radiography is an imaging technique that uses X-rays to see the internal shape of an object. To create an image, a beam of X-rays, a form of electromagnetic radiation, is produced by an X-ray generator and projected toward the object. A number of X-rays are absorbed by the object, depending on its density and structural composition. The X-rays passing through the object are captured behind the object by the detector (either a photographic film or a digital detector). The formation of two-dimensional flat images with this technique is called projection radiography. Computed tomography (CT scan) is where two-dimensional images from different angles undergo computer processing to produce a 3D representation.
Radiographic applications include medical radiography (or "diagnostics") and industrial radiography. Similar techniques are used in airport security (where "body scanners" generally use X-ray backscatter).
Video Radiography
Medical use
Because the body is composed of a variety of substances of different densities, X-rays can be used to reveal the body's internal structure in film by highlighting these differences using attenuation, or the absorption of X-ray photons by solids (such as calcium-rich bone). Disciplines involving anatomical studies through the use of radiographic films are known as radiographic anatomy. The acquisition of medical radiography is generally performed by radiographers, whereas image analysis is generally performed by radiologists. Medical radiography includes a variety of modalities that produce different types of imagery, each of which has different clinical applications.
Radiographic projection
The creation of the image by exposing the object to X-rays or other high-energy electromagnetic radiation form and capturing the resulting (or "shadow") file as a latent image is known as "projection radiography." The "shadow" can be turned into light using a fluorescent screen, which is then captured on a photographic film, it can be captured by a phosphor screen to be "read" later by laser (CR), or perhaps directly activate a solid-state detector matrix (DR - a very large CCD version in a digital camera). Bones and some organs (such as the lungs) primarily lend themselves to projection radiography. This is a relatively low cost investigation with high diagnostic results. The difference between soft and hard body parts comes largely from the fact that carbon has a very low X-ray cross section compared to calcium.
Computed tomography
Computed tomography or CT scan (formerly known as CAT scan, "A" which stands for "axial") uses a large amount of ionizing radiation (in the form of X-rays) in conjunction with the computer to create soft, hard-tissue images. These images look as if the patient is sliced ​​like bread (thus, "tomography" - "tomo" means "slice"). Trials are generally short, most lasting only during breath resistance. Contrast agents are often used, depending on which network to view. Radiographers perform this examination, sometimes in conjunction with radiologists (eg, when a radiologist performs a CT-guided biopsy).
X-ray energy absorber
DEXA, or bone densitometry, is used primarily for osteoporosis tests. This is not radiographic projection, because X-rays are emitted in 2 narrow beams that are scanned across patients, 90 degrees from each other. Usually the hip (femur head), lower back (lumbar spine) or heel (calcaneum) are imaged, and bone density (calcium amount) is determined and numbered (T-score). This is not used for bone imaging, as the image quality is not good enough to make accurate diagnostic images for fractures, inflammation etc. It can also be used to measure total body fat, although this is not common. The radiation dose received from the DEXA scan is very low, much lower than the projection radiographic examination.
Fluoroscopy
Fluoroscopy is a term invented by Thomas Edison during the initial X-ray study. His name refers to the fluorescence he sees upon seeing the glowing plates bombarded with X-rays.
This technique provides mobile projection radiography. Fluoroscopy is primarily performed to view movement (tissue or contrast agent), or to guide medical interventions, such as angioplasty, pacemaker insertion, or joint repair/replacement. The latter can often be done in the operating room, using a portable fluorescope machine called C-arm. Can move around the operating table and create a digital image for the surgeon. Biplanar fluoroscopy works in conjunction with a single aircraft fluoroscopy except to display two planes at the same time. The ability to work on two aircraft is important for orthopedic and spinal surgery and can reduce operating time by eliminating repositioning.
Angiography
Angiography is the use of fluoroscopy to look at the cardiovascular system. Iodine-based contrast is injected into the bloodstream and supervised as it travels. Since the blood is liquid and the vessels are not very dense, high-density contrasts (such as large iodine atoms) are used to see the vessels under X-rays. Angiography is used to locate aneurysms, leaks, thrombosis, growth of new vessels, and the placement of catheters and stents. Balloon angioplasty is often done with angiography.
Contrast radiography
Radiographic contrast using radiocontrast agents, a type of contrast medium, to make attractive structures stand out visually from their backgrounds. Contrast agents are required in conventional angiography, and can be used in both projection radiography and computed tomography (called "CT contrast").
Other medical imaging
Although not technically radiographic techniques because they do not use X-rays, imaging modalities such as PET and MRI are sometimes grouped in radiography because the hospital's radiology department handles all forms of imaging. Treatment using radiation is known as radiotherapy.
Maps Radiography
Industrial radiography
Industrial radiography is a non-destructive testing method in which many types of manufactured components can be checked to verify the internal structure and integrity of the specimen. Industrial radiography can be done by using X-rays or gamma rays. Both are forms of electromagnetic radiation. The difference between the various forms of electromagnetic energy is related to the wavelength. X and gamma rays have the shortest wavelength and these properties lead to the ability to penetrate, travel through, and exit from various materials such as carbon steel and other metals. Specific methods include industrial computer tomography.
Image quality
The sharpness of the radiographic image is largely determined by the size of the x-ray source. This is determined by the area of ​​the electron beam that is concerned with the anode. Large photon sources produce much more opaque in the final image and are aggravated by increasing the distance of image formation. This blurring can be measured as a contribution to the modulation transfer function of the imaging system.
Radiation dose
Protect
Lead is the most common shield against X-rays due to its high density (11340 kg/m 3 ), stop power, easy installation and low cost. The maximum range of high-energy photons such as X-rays in the material is unlimited; at any point in which the photons pass, there is the possibility of interaction. So there is a very small chance of no interaction in a great distance. Therefore protecting the photon beam is exponential (with the length of attenuation close to the length of the material radiation); doubling the thickness of the shield will signal the shield effect.
The following table shows the recommended lead coat thickness in X-ray energy functions, from Recommendations by the Second International Congress of Radiology.
Campaign
In response to increased public awareness of radiation doses and ongoing best practice progress, The Alliance for Radiation Safety in Pediatric Imaging was formed within the Society for Pediatric Radiology. Together with the American Society of Radiologic Technologists, The American College of Radiology and the American Association of Physicists in Medicine, the Society for Pediatric Radiology develops and launches an Image Gently Campaign designed to sustain high quality imaging studies using the lowest dose. and best radiation safety practices available in pediatric patients. This initiative has been supported and implemented by a growing list of Professional Medical organizations worldwide and has received support and assistance from companies that produce equipment used in Radiology.
Following the success of the Image Gently campaign, the American College of Radiology, the Radiological Society of North America, the American Association of Physicists in Medicine and the American Society of Radiologic Technologists have launched similar campaigns to address this problem in the adult population. called the Wise Pictures. The World Health Organization and the International Atomic Energy Agency (IAEA) of the United Nations have also worked in this field and have ongoing projects designed to extend best practice and reduce patient radiation doses.
Provider payment
Contrary to suggestions that emphasize only doing radiography when in the patient's interest, recent evidence suggests that they are used more frequently when dentists are paid under a fee-for-service
Tools
Source
In medicine, projection radiographs and computed tomography images generally use X-rays made by X-ray generators, which produce X-rays from X-ray tubes.
A number of other sources of X-ray photons are possible, and may be used in industrial or research radiography; these include betatron, and linear accelerators (linacs) and synchrotrons. For gamma rays, radioactive sources such as 192 Ir, 60 Co or 137 Cs are used.
Grid
The Bucky-Potter grid can be placed between the patient and the detector to reduce the number of scattered X-rays that reach the detector. This increases the image contrast resolution, but also increases the radiation exposure for the patient.
Detector
Detectors can be divided into two main categories: imaging detectors (such as photographic plates and X-ray films, now largely replaced by various digitalization devices such as picture plates or flat panel detectors) and dose-measuring devices (such as ionization chambers, Counters Geiger, and dosimeters used to measure local radiation exposure, dose, and/or dose rate, for example, to verify that radiation protection equipment and procedures are effective on an ongoing basis).
Intensive image and array detector
As an alternative to the X-ray detector, the image intensifier is an analog device that is ready to convert the acquired X-ray image into one visible on the video screen. This tool is made of a vacuum tube with a wide input surface coated on the inside with cesium iodide (CsI). When exposed to an X-ray beam material that causes a photocathode adjacent to it emits an electron. These electrons then focus on using the electron lenses inside the intensifier to the output screen coated with a fluorescent material. Images from the output can then be recorded through the camera and displayed.
Digital devices known as array detectors are becoming more common in fluoroscopy. This device is made of a discrete pixelated detector known as a thin film transistor (TFT) that can work indirectly using a photo detector that detects light emitted from a synthesizer such as CsI, or directly. by capturing the electrons generated when X-rays hit the detector. Direct detectors are not likely to experience any blurry or diffuse effects caused by fluorescent scintillators or screen films because the detector is activated directly by X-ray photons.
Dual-energy
Dual-energy radiography is where the image is obtained using two separate tube voltages. This is the standard method for bone densitometry. It is also used in lung angiography CT to reduce the required dose of contrast iodination.
History
The origins of radiographs and the origin of fluoroscopy can be traced to 8 November 1895, when the German physics professor Wilhelm Conrad RÃÆ'¶ntgen discovered X rays and noted that, although it can pass through human tissue, it can not pass through bone or metal. RÃÆ'¶ntgen refers to radiation as "X", to indicate that it is an unknown type of radiation. He received the first Nobel Prize in Physics for his invention.
There are contradictory accounts of his invention because RÃÆ'¶ntgen has his burned lab records after his death, but this is a possible reconstruction by his biography: RÃÆ'¶ntgen is investigating cathode rays using a fluorescent screen painted with barium platinocyanide and Crookes tubes that he wraps around a black cardboard to protect the fluorescent light. He saw a faint green glow from the screen, about 1 meter. RÃÆ'¶ntgen is aware of some invisible rays coming from the tube past the cardboard to make the screen shine: they pass through a blurred object to influence the movie behind it.
RÃÆ'¶ntgen discovered the medical use of X-rays when he made his wife's hand drawing on an X-ray photography plate. The photo of his wife's hand is the first photo of a human body part that uses X-rays. When he saw the picture, he said, "I have seen my death."
The first use of X-rays in clinical conditions was by John Hall-Edwards in Birmingham, England on January 11, 1896, when he meramografi needles attached to the hands of a colleague. On February 14, 1896, Hall-Edwards was also the first person to use X-rays in surgery.
The United States saw the first medical X-ray obtained using a tube release Ivan Pulyui. In January 1896, when reading the discovery of RÃÆ'¶ntgen, Frank Austin of Dartmouth College tested all the exhaust tubes in a physics laboratory and found that only Pulyui tubes produce X-rays. This is the result of the pulyui inclusion of the "target" oblique mica, which is used to store the fluorescent material sample, inside the tube. On February 3, 1896, Gilman Frost, professor of medicine at college, and his brother Edwin Frost, professor of physics, exposed the wrists of Eddie McCarthy, whom Gilman had treated weeks earlier due to fractures, to X-rays and collected images produced from bone which was broken on a plate of gelatin photography obtained from Howard Langill, a local photographer also interested in the work of RÃÆ'¶ntgen.
X-rays are used very early diagnostically; for example, Alan Archibald Campbell-Swinton opened a radiographic laboratory in England in 1896, before the dangers of ionizing radiation were discovered. Indeed, Marie Curie encouraged the radiography to be used to treat wounded soldiers in World War I. Initially, many types of staff performed radiography at the hospital, including Physicists, Photographers, Doctors, Nurses, and Engineers. Medical radiology expertise grew over the years around new technologies. When new diagnostic tests are developed, it is natural for radiographers to be trained and adopt this new technology. Radiographers are now doing fluoroscopy, computed tomography, mammography, ultrasound, nuclear medicine and magnetic resonance imaging as well. Although nonspecific dictionaries may define fairly narrow radiographs as "taking X-ray images", this has long been part of the work of "X-ray Departments", Radiographers, and Radiologists. Initially, radiographs were known as roentgenograms, while <<> Skiagrapher (from the Ancient Greek word for "shadow" and "author") was used until about 1918 for the purposes of Radiographers.
See also
- Autoradiograph
- Radiation background
- Computer-assisted diagnosis
- Imagery science
- List of civil radiation accidents
- Medical imaging in pregnancy
- Radiation
- Radiation contamination
- Radiographers
- Thermography
References
External links
- MedPix Medical Image Database
- Videos about X-ray and industrial computer tomography, Karlsruhe University of Science
- XAAMDI NIST: X-ray Destruction and Absorption of Dosimetric Data Bases Data
- NIST's XCOM: Photon Cross Sections Database
- NIST QUICKLY: Attenuation and Table Obstacles
- Incidence of lost industrial radiographs
- RadiologyInfo - Radiology information source for patients: Radiography (X-ray)
Further reading
- Radiation Security in Industrial Radiography , Special Security Guideline No. SSG-11, International Atomic Energy Agency, Vienna, 2011.
- Howard H. Seliger: Wilhelm Conrad RÃÆ'¶ntgen and Glimmer of Light . Physics Today, November 1995, 25-31, http://hdl.handle.net/10013/epic.43596.d001
- Shroy, Jr., Robert E. (1995). "X-Ray Equipment". In Bronzino, J.D. Biomedical Engineering Handbook . Press CRC and IEEE Press. pp. 953-960. ISBNÃ, 0-8493-8346-3. Ã ,
- Herman, Gabor T. (2009). Fundamentals of Computerized Tomography: Image Reconstruction from Projection (2nd ed.). Jumper. ISBN: 978-1-85233-617-2.
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Yu, Shi-Bao; Alan D. Watson (1999). "Overview of medical X-ray examination problems and metal-based contrast agents". Chemical Reviews . 99 (9): 2353-2378. doi: 10.1021/cr980441p. PMID 11749484.
Source of the article : Wikipedia
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