Radiography

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For the medical specialty covering all imaging modes, see Radiology. Radiography_sentence_0

For treatment using radiation, see Radiotherapy. Radiography_sentence_1

Radiography_table_infobox_0

RadiographyRadiography_table_caption_0
SystemRadiography_header_cell_0_0_0 MusculoskeletalRadiography_cell_0_0_1
SubdivisionsRadiography_header_cell_0_1_0 Interventional, Nuclear, Therapeutic, PaediatricRadiography_cell_0_1_1
Significant diseasesRadiography_header_cell_0_2_0 Cancer, bone fracturesRadiography_cell_0_2_1
Significant testsRadiography_header_cell_0_3_0 screening tests, X-ray, CT, MRI, PET, bone scan, ultrasonography, mammography, fluoroscopyRadiography_cell_0_3_1
SpecialistRadiography_header_cell_0_4_0 RadiographerRadiography_cell_0_4_1

Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Radiography_sentence_2

Applications of radiography include medical radiography ("diagnostic" and "therapeutic") and industrial radiography. Radiography_sentence_3

Similar techniques are used in airport security (where "body scanners" generally use backscatter X-ray). Radiography_sentence_4

To create an image in conventional radiography, a beam of X-rays is produced by an X-ray generator and is projected toward the object. Radiography_sentence_5

A certain amount of the X-rays or other radiation is absorbed by the object, dependent on the object's density and structural composition. Radiography_sentence_6

The X-rays that pass through the object are captured behind the object by a detector (either photographic film or a digital detector). Radiography_sentence_7

The generation of flat two dimensional images by this technique is called projectional radiography. Radiography_sentence_8

In computed tomography (CT scanning) an X-ray source and its associated detectors rotate around the subject which itself moves through the conical X-ray beam produced. Radiography_sentence_9

Any given point within the subject is crossed from many directions by many different beams at different times. Radiography_sentence_10

Information regarding attenuation of these beams is collated and subjected to computation to generate two dimensional images in three planes (axial, coronal, and sagittal) which can be further processed to produce a three dimensional image. Radiography_sentence_11

Medical uses Radiography_section_0

Radiography_table_infobox_1

RadiographyRadiography_header_cell_1_0_0
ICD-9-CMRadiography_header_cell_1_1_0 , -Radiography_cell_1_1_1
MeSHRadiography_header_cell_1_2_0 Radiography_cell_1_2_1
OPS-301 codeRadiography_header_cell_1_3_0 ,Radiography_cell_1_3_1

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 attenuation, or in the case of ionising radiation, the absorption of X-ray photons by the denser substances (like calcium-rich bones). Radiography_sentence_12

The discipline involving the study of anatomy through the use of radiographic images is known as radiographic anatomy. Radiography_sentence_13

Medical radiography acquisition is generally carried out by radiographers, while image analysis is generally done by radiologists. Radiography_sentence_14

Some radiographers also specialise in image interpretation. Radiography_sentence_15

Medical radiography includes a range of modalities producing many different types of image, each of which has a different clinical application. Radiography_sentence_16

Projectional radiography Radiography_section_1

Main article: Projectional Radiography Radiography_sentence_17

The creation of images by exposing an object to X-rays or other high-energy forms of electromagnetic radiation and capturing the resulting remnant beam (or "shadow") as a latent image is known as "projection radiography." Radiography_sentence_18

The "shadow" may be converted to light using a fluorescent screen, which is then captured on photographic film, it may be captured by a phosphor screen to be "read" later by a laser (CR), or it may directly activate a matrix of solid-state detectors (DR—similar to a very large version of a CCD in a digital camera). Radiography_sentence_19

Bone and some organs (such as lungs) especially lend themselves to projection radiography. Radiography_sentence_20

It is a relatively low-cost investigation with a high diagnostic yield. Radiography_sentence_21

The difference between soft and hard body parts stems mostly from the fact that carbon has a very low X-ray cross section compared to calcium. Radiography_sentence_22

Computed tomography Radiography_section_2

Main article: Computed tomography Radiography_sentence_23

Computed tomography or CT scan (previously known as CAT scan, the "A" standing for "axial") uses ionizing radiation (x-ray radiation) in conjunction with a computer to create images of both soft and hard tissues. Radiography_sentence_24

These images look as though the patient was sliced like bread (thus, "tomography"-- "tomo" means "slice"). Radiography_sentence_25

Though CT uses a higher amount of ionizing x-radiation than diagnostic x-rays (both utilising X-ray radiation), with advances in technology, levels of CT radiation dose and scan times have reduced. Radiography_sentence_26

CT exams are generally short, most lasting only as long as a breath-hold, Contrast agents are also often used, depending on the tissues needing to be seen. Radiography_sentence_27

Radiographers perform these examinations, sometimes in conjunction with a radiologist (for instance, when a radiologist performs a CT-guided biopsy). Radiography_sentence_28

Dual energy X-ray absorptiometry Radiography_section_3

Main article: Dual energy X-ray absorptiometry Radiography_sentence_29

DEXA, or bone densitometry, is used primarily for osteoporosis tests. Radiography_sentence_30

It is not projection radiography, as the X-rays are emitted in 2 narrow beams that are scanned across the patient, 90 degrees from each other. Radiography_sentence_31

Usually the hip (head of the femur), lower back (lumbar spine), or heel (calcaneum) are imaged, and the bone density (amount of calcium) is determined and given a number (a T-score). Radiography_sentence_32

It is not used for bone imaging, as the image quality is not good enough to make an accurate diagnostic image for fractures, inflammation, etc. Radiography_sentence_33

It can also be used to measure total body fat, though this is not common. Radiography_sentence_34

The radiation dose received from DEXA scans is very low, much lower than projection radiography examinations. Radiography_sentence_35

Fluoroscopy Radiography_section_4

Main article: Fluoroscopy Radiography_sentence_36

Fluoroscopy is a term invented by Thomas Edison during his early X-ray studies. Radiography_sentence_37

The name refers to the fluorescence he saw while looking at a glowing plate bombarded with X-rays. Radiography_sentence_38

The technique provides moving projection radiographs. Radiography_sentence_39

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. Radiography_sentence_40

The latter can often be carried out in the operating theatre, using a portable fluoroscopy machine called a C-arm. Radiography_sentence_41

It can move around the surgery table and make digital images for the surgeon. Radiography_sentence_42

Biplanar Fluoroscopy works the same as single plane fluoroscopy except displaying two planes at the same time. Radiography_sentence_43

The ability to work in two planes is important for orthopedic and spinal surgery and can reduce operating times by eliminating re-positioning. Radiography_sentence_44

Angiography Radiography_section_5

Main article: Angiography Radiography_sentence_45

Angiography is the use of fluoroscopy to view the cardiovascular system. Radiography_sentence_46

An iodine-based contrast is injected into the bloodstream and watched as it travels around. Radiography_sentence_47

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. Radiography_sentence_48

Angiography is used to find aneurysms, leaks, blockages (thromboses), new vessel growth, and placement of catheters and stents. Radiography_sentence_49

Balloon angioplasty is often done with angiography. Radiography_sentence_50

Contrast radiography Radiography_section_6

Main article: Radiocontrast agent Radiography_sentence_51

Contrast radiography uses a radiocontrast agent, a type of contrast medium, to make the structures of interest stand out visually from their background. Radiography_sentence_52

Contrast agents are required in conventional angiography, and can be used in both projectional radiography and computed tomography (called "contrast CT"). Radiography_sentence_53

Other medical imaging Radiography_section_7

Although not technically radiographic techniques due to not using X-rays, imaging modalities such as PET and MRI are sometimes grouped in radiography because the radiology department of hospitals handle all forms of imaging. Radiography_sentence_54

Treatment using radiation is known as radiotherapy. Radiography_sentence_55

Industrial radiography Radiography_section_8

Main article: Industrial radiography Radiography_sentence_56

Industrial radiography is a method of non-destructive testing where many types of manufactured components can be examined to verify the internal structure and integrity of the specimen. Radiography_sentence_57

Industrial Radiography can be performed utilizing either X-rays or gamma rays. Radiography_sentence_58

Both are forms of electromagnetic radiation. Radiography_sentence_59

The difference between various forms of electromagnetic energy is related to the wavelength. Radiography_sentence_60

X and gamma rays have the shortest wavelength and this property leads to the ability to penetrate, travel through, and exit various materials such as carbon steel and other metals. Radiography_sentence_61

Specific methods include industrial computed tomography. Radiography_sentence_62

Image quality Radiography_section_9

Image quality will depend on resolution and density. Radiography_sentence_63

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. Radiography_sentence_64

Sharpness of a radiographic image is strongly determined by the size of the X-ray source. Radiography_sentence_65

This is determined by the area of the electron beam hitting the anode. Radiography_sentence_66

A large photon source results in more blurring in the final image and is worsened by an increase in image formation distance. Radiography_sentence_67

This blurring can be measured as a contribution to the modulation transfer function of the imaging system. Radiography_sentence_68

Radiation dose Radiography_section_10

The dosage of radiation applied in radiography varies by procedure. Radiography_sentence_69

For example, the effective dosage of a chest x-ray is 0.1 mSv, while an abdominal CT is 10 mSv. Radiography_sentence_70

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." Radiography_sentence_71

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. Radiography_sentence_72

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. Radiography_sentence_73

Shielding Radiography_section_11

Lead is the most common shield against X-rays because of its high density (11340 kg/m), stopping power, ease of installation and low cost. Radiography_sentence_74

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. Radiography_sentence_75

Thus there is a very small probability of no interaction over very large distances. Radiography_sentence_76

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. Radiography_sentence_77

Radiography_table_general_2

X-rays generated by peak voltages belowRadiography_header_cell_2_0_0 Minimum thickness
of leadRadiography_header_cell_2_0_1
75 kVRadiography_cell_2_1_0 1.0 mmRadiography_cell_2_1_1
100 kVRadiography_cell_2_2_0 1.5 mmRadiography_cell_2_2_1
125 kVRadiography_cell_2_3_0 2.0 mmRadiography_cell_2_3_1
150 kVRadiography_cell_2_4_0 2.5 mmRadiography_cell_2_4_1
175 kVRadiography_cell_2_5_0 3.0 mmRadiography_cell_2_5_1
200 kVRadiography_cell_2_6_0 4.0 mmRadiography_cell_2_6_1
225 kVRadiography_cell_2_7_0 5.0 mmRadiography_cell_2_7_1
300 kVRadiography_cell_2_8_0 9.0 mmRadiography_cell_2_8_1
400 kVRadiography_cell_2_9_0 15.0 mmRadiography_cell_2_9_1
500 kVRadiography_cell_2_10_0 22.0 mmRadiography_cell_2_10_1
600 kVRadiography_cell_2_11_0 34.0 mmRadiography_cell_2_11_1
900 kVRadiography_cell_2_12_0 51.0 mmRadiography_cell_2_12_1

The following table shows the recommended thickness of lead shielding in function of X-ray energy, from the Recommendations by the Second International Congress of Radiology. Radiography_sentence_78

Campaigns Radiography_section_12

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. Radiography_sentence_79

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. Radiography_sentence_80

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. Radiography_sentence_81

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. Radiography_sentence_82

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. Radiography_sentence_83

Provider payment Radiography_section_13

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 Radiography_sentence_84

Equipment Radiography_section_14

Credits to the contents of this page go to the authors of the corresponding Wikipedia page: en.wikipedia.org/wiki/Radiography.