Radiography
ultrasonography, mammography, fluoroscopy | |
Specialist | Radiographer |
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Radiography is an
Medical uses
Radiography | |
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ICD-9-CM | 87, 88.0-88.6 |
MeSH | D011859 |
OPS-301 code | 3–10...3–13, 3–20...3–26 |
Since the body is made up of various substances with differing densities, ionising and non-ionising radiation can be used to reveal the internal structure of the body on an image receptor by highlighting these differences using
Projectional radiography
The creation of images by exposing an object to
Computed tomography
Dual energy X-ray absorptiometry
Fluoroscopy
Fluoroscopy is a term invented by Thomas Edison during his early X-ray studies. The name refers to the fluorescence he saw while looking at a glowing plate bombarded with X-rays.[2]
The technique provides moving projection radiographs. Fluoroscopy is mainly performed to view movement (of tissue or a contrast agent), or to guide a medical intervention, such as angioplasty, pacemaker insertion, or joint repair/replacement. The last can often be carried out in the operating theatre, using a portable fluoroscopy machine called a C-arm.[3] It can move around the surgery table and make digital images for the surgeon. Biplanar Fluoroscopy works the same as single plane fluoroscopy except displaying two planes at the same time. The ability to work in two planes is important for orthopedic and spinal surgery and can reduce operating times by eliminating re-positioning.[4]
Angiography
Angiography is the use of fluoroscopy to view the cardiovascular system. An iodine-based contrast is injected into the bloodstream and watched as it travels around. Since liquid blood and the vessels are not very dense, a contrast with high density (like the large iodine atoms) is used to view the vessels under X-ray. Angiography is used to find aneurysms, leaks, blockages (thromboses), new vessel growth, and placement of catheters and stents. Balloon angioplasty is often done with angiography.
Contrast radiography
Contrast radiography uses a radiocontrast agent, a type of
Other medical imaging
Although not technically radiographic techniques due to not using X-rays, imaging modalities such as
Industrial radiography
Image quality
Image quality will depend on resolution and density. Resolution is the ability an image to show closely spaced structure in the object as separate entities in the image while density is the blackening power of the image. Sharpness of a radiographic image is strongly determined by the size of the X-ray source. This is determined by the area of the electron beam hitting the anode. A large photon source results in more blurring in the final image and is worsened by an increase in image formation distance. This blurring can be measured as a contribution to the
Radiation dose
The dosage of radiation applied in radiography varies by procedure. For example, the effective dosage of a chest x-ray is 0.1 mSv, while an abdominal CT is 10 mSv.[7] The American Association of Physicists in Medicine (AAPM) have stated that the "risks of medical imaging at patient doses below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent." Other scientific bodies sharing this conclusion include the International Organization of Medical Physicists, the UN Scientific Committee on the Effects of Atomic Radiation, and the International Commission on Radiological Protection. Nonetheless, radiological organizations, including the Radiological Society of North America (RSNA) and the American College of Radiology (ACR), as well as multiple government agencies, indicate safety standards to ensure that radiation dosage is as low as possible.[8]
Shielding
X-rays generated by peak voltages below |
Minimum thickness of lead |
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75 kV | 1.0 mm |
100 kV | 1.5 mm |
125 kV | 2.0 mm |
150 kV | 2.5 mm |
175 kV | 3.0 mm |
200 kV | 4.0 mm |
225 kV | 5.0 mm |
300 kV | 9.0 mm |
400 kV | 15.0 mm |
500 kV | 22.0 mm |
600 kV | 34.0 mm |
900 kV | 51.0 mm |
Lead is the most common shield against X-rays because of its high density (11,340 kg/m3), stopping power, ease of installation and low cost. The maximum range of a high-energy photon such as an X-ray in matter is infinite; at every point in the matter traversed by the photon, there is a probability of interaction. Thus there is a very small probability of no interaction over very large distances. The shielding of photon beam is therefore exponential (with an attenuation length being close to the radiation length of the material); doubling the thickness of shielding will square the shielding effect.
Table in this section shows the recommended thickness of lead shielding in function of X-ray energy, from the Recommendations by the Second International Congress of Radiology.[9]
Campaigns
In response to increased concern by the public over radiation doses and the ongoing progress of best practices, The Alliance for Radiation Safety in Pediatric Imaging was formed within the Society for Pediatric Radiology. In concert 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 developed and launched the Image Gently campaign which is designed to maintain high quality imaging studies while using the lowest doses and best radiation safety practices available on pediatric patients.[10] This initiative has been endorsed and applied by a growing list of various professional medical organizations around the world and has received support and assistance from companies that manufacture equipment used in radiology.
Following upon 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 a similar campaign to address this issue in the adult population called Image Wisely.[11] The World Health Organization and International Atomic Energy Agency (IAEA) of the United Nations have also been working in this area and have ongoing projects designed to broaden best practices and lower patient radiation dose.[12][13][14]
Provider payment
Contrary to advice that emphasises only conducting radiographs when in the patient's interest, recent evidence suggests that they are used more frequently when dentists are paid under fee-for-service.[15]
Equipment
Sources
In medicine and dentistry,
A number of other sources of
are used.Grid
An anti-scatter grid may be placed between the patient and the detector to reduce the quantity of scattered x-rays that reach the detector. This improves the contrast resolution of the image, but also increases radiation exposure for the patient.[16]
Detectors
Detectors can be divided into two major categories: imaging detectors (such as
Side markers
A radiopaque anatomical side marker is added to each image. For example, if the patient has their right hand x-rayed, the radiographer includes a radiopaque "R" marker within the field of the x-ray beam as an indicator of which hand has been imaged. If a physical marker is not included, the radiographer may add the correct side marker later as part of digital post-processing.[20]
Image intensifiers and array detectors
As an alternative to X-ray detectors, image intensifiers are analog devices that readily convert the acquired X-ray image into one visible on a video screen. This device is made of a vacuum tube with a wide input surface coated on the inside with caesium iodide (CsI). When hit by X-rays material phosphors which causes the photocathode adjacent to it to emit electrons. These electrons are then focused using electron lenses inside the intensifier to an output screen coated with phosphorescent materials. The image from the output can then be recorded via a camera and displayed.[21]
Digital devices known as array detectors are becoming more common in fluoroscopy. These devices are made of discrete pixelated detectors known as thin-film transistors (TFT) which can either work indirectly by using photo detectors that detect light emitted from a scintillator material such as CsI, or directly by capturing the electrons produced when the X-rays hit the detector. Direct detectors do not tend to experience the blurring or spreading effect caused by phosphorescent scintillators or by film screens since the detectors are activated directly by X-ray photons.[22]
Dual-energy
History
Radiography's origins and
There are conflicting accounts of his discovery because Röntgen had his lab notes burned after his death, but this is a likely reconstruction by his biographers:
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 ever photograph of a human body part using X-rays. When she saw the picture, she said, "I have seen my death."[28]
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 also became the first to use X-rays in a surgical operation.[29]
The United States saw its first medical X-ray obtained using a
X-rays were put to diagnostic use very early; for example,
See also
- Autoradiograph
- Background radiation
- Computer-aided diagnosis
- GXMO
- Imaging science
- List of civilian radiation accidents
- Medical imaging in pregnancy
- Radiation
- Digital radiography
- Radiation contamination
- Radiographer
- Thermography
References
- PMID 26908984.
- ISBN 9780398080976.
- ISBN 9781284117714.
- PMID 10903700.
- ISBN 978-1-4612-7039-3.
- ISBN 9780781761352.
- ^ "Reducing Radiation from Medical X-rays". FDA.gov. Retrieved 9 September 2018.
- ^ Goldberg J (September–October 2018). "From the Spectral to the Spectrum". Skeptical Inquirer. 42 (5).
- ^ Alchemy Art Lead Products – Lead Shielding Sheet Lead For Shielding Applications. Retrieved 7 December 2008.
- ^ "IG new: The Alliance | image gently". Pedrad.org. Archived from the original on 9 June 2013. Retrieved 16 August 2013.
- ^ "Radiation Safety in Adult Medical Imaging". Image Wisely. Retrieved 16 August 2013.
- ^ "Optimal levels of radiation for patients – Pan American Health Organization – Organización Panamericana de la Salud". New.paho.org. 24 August 2010. Archived from the original on 25 May 2013. Retrieved 16 August 2013.
- ^ "Radiation Protection of Patients". Rpop.iaea.org. 14 March 2013. Retrieved 16 August 2013.
- ^ "World Health Organisation: Global Initiative on Radiation Safety in Healthcare Settings: Technical Meeting Report" (PDF). Who.int. Archived (PDF) from the original on 29 October 2013. Retrieved 16 August 2013.
- PMID 29408150.
- ISBN 9780683301182.
- PMID 10194791.
- PMID 10028632.
- ISBN 978-3-642-38660-2.
- PMID 27648278.
- ISBN 9780471461135.
- PMID 16862412.
- ^ Cochrane Miller J (2015). "Dual Energy CT Imaging for Suspected Pulmonary Embolism Using a Lower Dose of Contrast Agent". Radiology Rounds. 13 (7). Archived from the original on 10 May 2017. Retrieved 5 February 2018.
- ^ "History of Radiography". NDT Resource Center. Iowa State University. Retrieved 27 April 2013.
- ^ Karlsson EB (9 February 2000). "The Nobel Prizes in Physics 1901–2000". Stockholm: The Nobel Foundation. Retrieved 24 November 2011.
- ^ "5 unbelievable things about X-rays you can't miss". vix.com. Archived from the original on 24 December 2020. Retrieved 23 October 2017.
- ISBN 978-0930405229.
- ^ a b Markel H (20 December 2012). "'I Have Seen My Death': How the World Discovered the X-Ray". PBS NewsHour. PBS. Archived from the original on 20 August 2020. Retrieved 27 April 2013.
- ^ "Major John Hall-Edwards". Birmingham City Council. Archived from the original on 28 September 2012. Retrieved 17 May 2012.
- PMID 7998549.
- .
Further reading
- Oakley, PA; Harrison, DE (2020). X-Ray Hesitancy: Patients' Radiophobic Concerns Over Medical X-rays. Dose-Response. Specific Safety Guide No. SSG-11 (Report). Vienna: International Atomic Energy Agency. PMC 7503016.
- Seliger HH (November 1995). "Wilhelm Conrad Röntgen and the Glimmer of Light". Physics Today. 48 (11): 25–31. .
- Shroy Jr RE (1995). "X-Ray equipment". In Bronzino JD (ed.). The Biomedical Engineering handbook. CRC Press and IEEE Press. pp. 953–960. ISBN 978-0-8493-8346-5.
- ISBN 978-1-85233-617-2.
- Yu SB, Watson AD (September 1999). "Metal-Based X-ray Contrast Media". Chemical Reviews. 99 (9): 2353–78. PMID 11749484.
External links
- MedPix Medical Image Database
- Video on X-ray inspection and industrial computed tomography, Karlsruhe University of Applied Sciences
- NIST's XAAMDI: X-Ray Attenuation and Absorption for Materials of Dosimetric Interest Database
- NIST's XCOM: Photon Cross Sections Database
- NIST's FAST: Attenuation and Scattering Tables
- A lost industrial radiography source event
- RadiologyInfo - The radiology information resource for patients: Radiography (X-rays)