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86 Cards in this Set
- Front
- Back
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absorbed dose
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The amount of energy (x-rays) per unit mass absorbed by the irradiated tissue
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Acute
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Having a short and relatively severe course
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air kerma
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represents a measurement of the radiation intensity in the air. Kinetic Energy Released in Air
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array beam collimation
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Dual energy x ray absoptiometry system that uses a narrow slit x ray collimator and a multielement detector. The motion is in one direction only, which greatly reduces scan time and permits supine lateral spine scans. it introduces a slight geometric distortion at the outer edges, which necessitates careful centering of the object of interest.
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Atomic number
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represents the number of protons in the nucleus of an atom
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attenuation
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absorption of the x ray beam in matter, usually the human body
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automatic exposure control (AEC)
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An electronic circuit within the x ray machine that automatically terminates the exposure time when a predetermined quantity of x rays has been detected.
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bone densitometry
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The art and science of measuring the bone mineral content, area, and density of specific anatomic sites or the whole body.
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bone mass
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a general term for the amount of mineral in a bone
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bone mineral content (BMC)
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a measure of bone mineral in tge total area of a reason of interest
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bone mineral density (BMD)
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a measure of bone mineral outer unit area of a region of interest
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bremsstrahlung radiation
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one of two types of x rays. created when an electron enters the tungsten anode of the x ray tube, misses the tungsten electrons, and gets very near the nucleus. the electron suddenly slows down and deviates, and the loss of energy creates an x ray photon.
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brightness
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the digital term for density. describes the overall radiographic image appearance on the display monitor.
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bucky
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a device that contains a moving grid
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characteristic radiation
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created when an electron enters the tungsten anode of the X ray tube and knocks out a k shell elwcteon. This interaction produces an X ray photon
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collimation
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restricting the size and shape of the radiation beam as it exits the X ray tube
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Compton Effect
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The X ray photon is scattered from the body rather than going directly through to expose the dilm. This effect is undesirable in radiographic imaging.
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Computed Radiography (CR)
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cassette bases digital imaginh. The image of the body part is obtained using storage phosphor plates
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contrast resolution
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The ability to distinguish anatomical structures of similar subject contrast such as liver-spleen and gray matter-white matter
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CR reader
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unit used in computed Radiography to scan and process the latent image. A laser scan is used to release the stored image, which is collected and converted to an electrical signal and is then sent to the computer for viewing
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densitometer
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device that measures the optical density on a film
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digital imaging
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the process of acquiring images of the body using x rays, displaying them digitally, and viewing and storing them on a computer and in computer files
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Digital Imaging and Communications in Medicine (DICOM)
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The universally accepted standard for the storage, transmision, and display of medical images
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digital Radiography (DR)
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cassetteless. do not use a cassette with phosphors. The phosphor is bonded to a flat panel detector built into the X ray table
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diode
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an electronic device that permits current to flow in one direction only
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dual energy x ray asorptiometry (DXA)
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a bone density measurement technique using an X ray source separated into two energies. it has good accuracy and precision and can scan essentially any anatomic site, which makes it the most versatile of the bone density techniques
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dynamic range
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The number of gray shades that an imaging system can reproduce
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effective dose (EfD)
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This value is the limiting system used to calculate the upper limits of occupational exposure permissible
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electromagnetic energy
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has both electric and magnetic properties
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equivalent dose (EqD)
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The absorbed dose multiplied by a radiation weighting factor. For diagnostic X rays, the weighting factor is 1; therefore the absorbed dose and equivalent dose will be the same for diagnostic X rays.
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exposure indicator number
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a manufacturer-specific number that correlates to the amount of radiation that reaches the digital image receptor
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flat panel detector
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a detector under the table of a digital Radiography table that allows direct conversion of the x rays to electrical signals, which are then converted to an image
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flourescence
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the emission of light from the screen inside the cassette after exposure to x rays.
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Gray (Gy)
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the SI unit of measure for radiation absorbed dose. It is subdivided into air exposure and tissue exposure.
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image receptor (IR)
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The device that receives the energy of the x ray beam and forms the image of the body part. The IR may be a screen film cassette, a computed Radiography (CR) imaging plate, or a solid-state digital receptor.
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imaging plate
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a plate with special phosphors used in digital imaging. The plate is housed inside a cassette and stores the x ray image until it is processed
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ionizing radiation
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radiation that, when passing through the body tissues, produces positively or negatively charged particles.
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latent image
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the image contained in the film before it is processed
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morphometriv x ray abdorptiometry (MXA)
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Lateral scans of the thoracic and lumbar spine using single or dual x ray absorptiometry to determine vertebral abnormalities or fractures from the shapes of the vertebrae
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object-image receptor distance (OID)
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The distance from the patient to the image receptor. must be kept to a minimum to reduce magnification and increase spatial resolution.
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PACS (Picture Archival and Communications System)
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systems used in the radiology department to transmit images to transmit images to remote locations and to store images for long term use.
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peak bone mass
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maximum bone mass, usually achieved between 30 and 35 years of age. population mean peak bone mass is used as a reference point for the T score
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pencil-beam collimation
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dual energy x ray absorptiometry system using a circular pinhole x ray collimator that produces a narrow x ray stream, which is received by a single detevtor. it has a serpentine motion across or along the length of the body. modern systems have improved scan time and image quality. off centering of the object does not cause geometric distortion.
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percent coefficient of variation (%CV)
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a statistic used to compare standard deviations from different data sets that may have different means; also a measure of precision. it is calculated as the standard deviation divided by the mean, times 100. A smaller %CV indicates better precision.
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photoelectric effect
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One of three interactions of radiation with the human body tissues. In this effect, the x ray photon is totally absorbed in the body tissues.
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photostimulable phosphor (PSP)
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a phosphor used in computed Radiography (CR) plates to absorb the x ray energy and store it until it is processed by the special unit and laser light
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potential difference
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the force or strength of the electrons flowing within an electric circuit. sane as volt
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prime factors of exposure
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milliamperage (mA), exposure time (s), kilovoltage (kVp), and source image receptor distance (SID)
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quantum mottle
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a grainy or mottled appearance of the image, usually caused by the use of an insufficient radiation exposure for the body part or for the requirements of the image receptor. quantum mottle Is not desirable in creating x ray images
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radiographic absorptiometry (RA)
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a technique in which hand x ray density in an image is visually compared with that of a known standard in the exposure field
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radiolucent
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referring to a substance that is easily penetrated by x rays. The term also refers to an area of the film through which a moderate amount of light from the view box is transmitted
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recorded detail
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The sharpness of the structures in the image. The terms sharpness, detail and resolution are often used to describe recorded detail. spatial resolution
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rectification
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The process of changing alternating current into direct current to produce x rays.
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roentgen
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a unit measuring the amount of radiation intensity in the air. The amount of radiation measured before it hits the body
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shewhart control Chart rules
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classic quality control rules based on comparing a data value to the mean and standard deviation of a set of similar values
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sievert (Sv)
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a unit measuring the effective radiation dose to a patient.
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signal to noise ratio (SNR)
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The ability of the digital system to convert the x ray input electric signal into a useful radiographic image
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single energy x ray absorptiometry (SXA)
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a technique for measuring bone density in the peripheral skeleton using single energy x ray source and an external medium
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source image receptor distance (SID)
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the distance from the focal spot of the x ray tube to the image receptor.
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spatial resolution
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The ability to distinguish between adjacent structures. amount of detail or sharpness as seen on the computer monitor
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thermionic emission
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The process by which electrons are are "boiled off" from the tungsten filament in the x ray tube. This occurs when the filament is heated during the x ray exposure. These electrons are then forced into the anode during the x ray exposure, creating x rays
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T score
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bone mineral density differs from the average bone mineral density of young, normal, sex matched individuals with peak bone mass
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z score
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The number of standard deviations by which an individual bone mineral density differs from the average bone mineral density of a sex and age matched reference group.
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Contrast is primarily controlled by..
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kVp. As kVp is decreased, contrast increases
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What makes the anatomy more visible?
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contrast
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density is primarily controlled by..
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mAs.
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What is the primary controller of the penetration of x rays?
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kVp
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What is the primary controller of radiographic contrast?
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kVp
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The quantity of exposure and the patient dose are directly proportional to..
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The mAs
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What controls radiographic density?
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milliamperes (mA)
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What controls quantity of x rays produced?
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milliamperes (mA)
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What is controlled by adjusting the filament heat?
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milliamperes (mA)
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What quantity of exposure is directly proportional to mA
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milliamperes (mA)
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What controls radiographic density?
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exposure time
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What controls quantity of x rays produced ?
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exposure time
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What is controlled by adjusting the timer in x ray circuit?
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exposure time
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What controls duration of exposure?
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exposure time
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What controls radiographic contrast?
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kilovolts (kVp)
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What controls x ray penetration?
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kilovolts (kVp)
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increased kVp results in __________ quantity of photons
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increased
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increased kVp results in ___________ penetration of the body part
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increased
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What affects the density and intensity of the x ray beam?
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source image receptor distance (SID)
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quantity of exposure is _________ proportional to the square of the distance
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inversely
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What are the prime factors that affect x ray quantity?
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mAs, kVp, SID, and filtration
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What factors affect x ray quality?
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kilovoltage and filtration
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What is the primary purpose of the rectifier unit?
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to change alternating current into direct current
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