Glossary

This glossary is adapted from ACR (1999) with permission, AHCPR (1994), and other sources.

abnormal screening examination: Mammography examination resulting in the recommendation of further imaging evaluation, short-interval follow-up or biopsy. absorbed dose (D): The energy imparted to matter by ionizing radiation per unit mass of irradiated material at the point of interest. The special name for the unit of absorbed dose is the gray (Gy), where 1 Gy =

aliasing: The false frequency information (or alias) detected when the signal being detected is grater than the Nyquist frequency. areola: The pigmented ring of tissue that surrounds the nipple. artifact: Any structure visible in the image that is not part of the object being imaged.

automatic exposure control (AEC) systems: Automatic exposure control systems, often referred to as phototimers, are designed to automatically determine and provide the exposure needed to produce an adequate optical density image by sampling the x-ray intensity after passage through the patient and image receptor. axilla: The underarm area containing lymph nodes and channels, blood vessels, nerves, muscle, and fat; anterior border is the pectoralis major muscle and posterior border is the latissimus dorsi muscle. axillary tail: Anatomical projection of breast tissue that extends into axilla (axillary tail of Spence). base density: The optical density due to the supporting base of the film alone. The base density of a film is the optical density that would result if an unexposed film were processed through the fixer, wash and dryer, without first passing through the developer. base-plus-fog density: The optical density of a film due to its base density plus any action of the developer on the unexposed silver halide crystals. The base-plus-fog density can be measured by processing an unexposed film through the entire processing cycle and measuring the resultant optical density. A low base-plus-fog density is desirable. Factors such as exposure of the film to heat or high humidity can cause an undesirable increase in the base-plus-fog density. benign: A noncancerous condition that does not spread to other parts of the body.

biopsy: Removal of an entire abnormality (excisional biopsy) or a sampling or portion of an abnormality (core biopsy and incisional biopsy) for microscopic examination in order to diagnose a problem. breast carcinoma in situ: Breast change in which malignant cells are localized and confined to breast ducts or lobules and may press against adjoining breast tissue but have not penetrated or spread beyond the breast (also called noninvasive breast cancer or noninfil-trating breast cancer). breast conservation: A surgical procedure for removing a cancerous tumor, lesion, or lump along with a rim of normal tissue around it (also called a lumpectomy). breast self-examination: Inspection and palpation of her breasts by the woman herself.

bucky: A component of the mammography x-ray unit that contains a moving grid, holds the x-ray film cassette, and supports the breast during imaging. calcifications: (see microcalcifications).

cancer: A general term for more than 100 diseases characterized by abnormal and uncontrolled growth of cells. cancer detection rate: The overall number of cancers detected per

1,000 patients examined by mammography. cassette: A light-tight case, usually made of thin, low x-ray absorption plastic, for holding x-ray film. Intensifying screens for the conversion of x rays to visible light photons are mounted inside the cassette so that they are in close contact with the film. Almost all mammography cassettes today are equipped with single screens. clinical breast examination (CBE): A complete examination of the breasts and axilla with palpation by a health care professional, including examination of the breasts with the woman upright and supine. compression: Involves pressing the breast between the compression device and the platform holding the film during mammography. compression device: A plastic paddle used to reduce blurring due to motion by holding the breast stationary, to help separate structures within the breast, and to decrease the thickness of breast tissue, minimizing the amount of radiation used and the amount of scattered radiation reaching the film. Ideally, the compression device is made of rigid, thin plastic and has a flat bottom surface that is parallel to the plane of the image receptor and with edges perpendicular to the plane of the image receptor to assist in moving breast tissue away from the chest wall and into the field of view. confidence interval: A measure of the extent to which an estimate of risk, dose or other parameter is expected to lie within a specified interval (e.g., a 90 percent confidence interval of a risk estimate means that, based on available information, the probability is 0.9 that the true but unknown risk lies within the specified interval). contact mammography: Usual mammography, with the breast in direct contact with the Bucky (unlike magnification technique).

contralateral: Originating in or affecting the opposite side of the body. correlative physical examination: Directed palpation of the breast performed by either the radiologic technologist or the interpreting physician to improve interpretation and ensure that a palpable abnormality is included on the film. craniocaudal (CC) view: One of two routine views for mammography. The image receptor is placed caudad to (below) the breast and the vertical x-ray beam is directed from cranial to caudad (downward) through the breast. cyst: A fluid-filled sac that may be felt on physical examination or depicted by mammography or ultrasonography. darkroom fog: Added optical density on a film due to light leaks or safe lights in a darkroom. It degrades image contrast and must be tested and eliminated to ensure image quality. dedicated mammography equipment: X-ray systems designed specifically for breast imaging. Such a unit provides a specialized imaging geometry and a device for breast compression and can consistently produce mammographic images of high quality. densitometer: An instrument that measures the optical density or degree of blackening of film. detents: Mechanical settings that limit or prevent the motion or rotation of an x-ray tube, cassette assembly, or image-receptor system or that allow exposures with specified tube orientations. deterministic effects: Biological effects for which the severity of the effect in affected individuals varies with the dose, and for which a threshold usually exists. developer: A chemical solution that changes the film latent image to a visible image composed of black metallic silver. developer replenishment: The process whereby fresh developer is added in small amounts to the solution in the developer tank of the processor. The purpose is to maintain the proper chemical activity and level of solution in the developer tank that would otherwise decrease through use.

diagnostic mammography: A radiologic examination used to evaluate a patient with a breast mass or masses, other breast signs or symptoms (spontaneous nipple discharge, skin changes, etc.), an abnormal or questionable screening mammogram, or special cases such as a history of breast cancer with breast conservation or augmented breasts. diaphanography: A noninvasive breast imaging technique that uses visible or near-visible light in an attempt to visualize breast masses. digital mammography: Mammography performed with an image detector that converts the x-ray signal into electronic form. The acquisition and display operations are separated. dose: Often used generically when not referring to a specific quantity such as mean glandular dose. dose equivalent (H): A quantity used in measurement of radiation at a point that expresses the biological effect of all kinds of radiation on a common scale. Dose equivalent is defined as the product of the absorbed dose (D) and the quality factor (Q) for the particular radiation (i.e., H = D x Q). The special name for the unit of dose equivalent is the sievert (Sv) where 1 Sv = 1 J kg-1. duct: A channel for transporting fluid from the lobules (breast glands that produce milk) to the nipple. ductal carcinoma in situ (DCIS): A form of breast carcinoma in situ confined to the breast ducts; often reveals itself with microcalcification on mammography (also called noninvasive breast carcinoma or intra-ductal breast carcinoma). effective dose (E): The sum of the equivalent doses (HT) to individual organs or tissues multiplied by their respective tissue weighting factors (wT). The special name for the unit of effective dose is the sievert (Sv) where 1 Sv = 1 J kg-1. equivalent dose (HT): A quantity used for radiation protection purposes that is the product of the mean absorbed dose (DT) in a tissue or organ and the radiation weighting factor (wR). The equivalent dose allows for differences in the detriment to tissue from identical absorbed doses of various forms of ionizing radiation. The special name for the unit of equivalent dose is the sievert (Sv) where 1 Sv =

exposure: The amount of x-ray irradiation, quantitated by measuring the amount of ionization in air caused by the radiation. fibroadenoma: A benign breast condition common in young adult women in which the breast develops a solid lump, usually firm but movable in the breast. filtration: A metal absorber placed in the path of the x-ray beam just after the x-ray tube to absorb very low-energy x rays to produce an x-ray beam with a narrow energy range. Molybdenum is the most common metal for use as filtration in mammography. fine-needle aspiration biopsy: A diagnostic technique used to sample cells from breast lumps. Cells from lumps are aspirated with a thin needle, smeared on a glass slide, stained, and evaluated by a pathologist.

first-degree relative: Mother, daughter or sister.

fixer: A chemical solution that removes the undeveloped silver halide crystals from film. Fixer also helps to harden the gelatin containing the black metallic silver so the film may be dried more readily. fixer retention: The inadequate removal of fixer from the film by the water in the wash tank of the processor. Retained fixer causes brown discoloration of the radiograph (often within a year or less). focal spot: The focal spot is the area of the target or anode that is bombarded by electrons from the cathode of the x-ray tube to produce x rays. The smaller the focal spot, the better the limiting spatial resolution of the x-ray system, especially in magnification mammography. fog: The unwanted density added to a radiograph by the action of the developer on the unexposed silver halide crystals or by exposure of the film to light, radiation or heat during storage, handling and processing.

gray (Gy): The special name for the SI unit of absorbed dose, 1 Gy =

grid: A set of thin, closely spaced lead strips interspaced by fiber or aluminum. In mammography the grid is placed between the breast and the screen-film image receptor to reduce scattered radiation reaching the image receptor. Scattered radiation reduces image contrast in mammography and limits the detection of low-contrast structures such as fibers and masses. half-value layer (HVL): The thickness of a specified substance that, when introduced into the path of a beam of radiation, reduces the exposure rate by one-half. HVL is a measure of beam quality and is usually specified in millimeters of aluminum for diagnostic x-ray equipment. The higher the HVL, the more penetrating the x-ray beam.

image contrast: The optical density difference between adjacent areas in a radiographic image resulting from an attenuation difference in the imaged object. image noise: (see radiographic noise).

image quality: The overall clarity of a radiographic image. Image sharpness, image contrast, and image noise are three common measures of image quality.

image sharpness: How well the margins of linear structures, masses and calcifications are depicted in the radiograph. in situ: Confined to site of origin, not having invaded adjoining tissues or metastasized to other parts of the body (e.g., intraductal). invasive breast cancer: Disease in which breast cancer cells have penetrated surrounding breast tissue and can spread into distant organs. ipsilateral: Originating in or affecting the same side of the body. kilovolt (kV): A unit of electrical potential difference equal to 1,000 volts. kilovolt peak (kVp): (also see operating potential). The crest value in kilovolts of the potential difference of a pulsating potential generator. When only one-half of the voltage wave cycle is used, the value refers to the useful half of the cycle. latent period: The period of time between exposure to ionizing radiation and the appearance of the radiation effect. lateral view: A 90 degree view performed medial to lateral or lateral to medial; used for triangulation with the craniocaudal and to demonstrate gravity-dependent calcifications. lateromedial: A 90 degree view performed with the x-ray beam directed from the outer aspect of the breast to the inner aspect of the breast. lateromedial oblique: Performed with the x-ray beam directed from the lower-outer to the upper-inner aspect of the breast; the exact reverse of the mediolateral-oblique view; improves visualization of medial breast tissue (also called true reverse oblique).

lobe: A portion of the breast that contains a complete unit for producing, transporting and delivering milk. lobular carcinoma in situ (LCIS): A high-risk condition in which multiple atypical cells fill and distend the lobules. Because it is a risk factor and not a direct precursor of invasive cancer, LCIS is considered a marker for increased risk of development of breast cancer in any location in either breast (also called lobular neoplasia). localization: Prebiopsy localization provides a method for biopsy of non-palpable mammographic abnormalities; can be performed by needle placement alone, spot dye injection, or needle-hookwire methods. lux: A unit of illumination equal to the direct illumination on a surface that is everywhere 1 m from a uniform point source of one candle intensity or equal to one lumen per square meter. lymph nodes: Kidney bean-shaped structures scattered along vessels of the lymphatic system seen in the axilla or sometimes in the breast itself; act as filters, collecting bacteria or cancer cells that may travel through the lymph system (also called lymph glands). magnetic resonance imaging (MRI): An imaging modality using a strong magnetic field and radiofrequency signals to produce multipla-nar images of the body. Image contrast is based on the hydrogen concentration, molecular response to radiofrequency signals, and flow of structures within the part of the body being imaged. magnification view: A technique for producing an enlarged image with greater detail of a small area of suspicious breast tissue. malignant: Cancerous; a growth of cancer cells.

mammogram: An x-ray image of the breast recorded on film, paper or digital receptor.

mammography: An x-ray examination of the breast (see screening mammography and diagnostic mammography). Mammography Quality Standards Act (MQSA): MQSA went into effect in 1994 and required all mammography facilities in the United States to be accredited by an approved body and undergo annual inspections by state or federal inspectors. The Food and Drug Administration is responsible for implementing MQSA and developing national mammography regulations. mean glandular dose: Calculated from values of entrance exposure (free-in-air), the x-ray beam quality (half-value layer), and compressed breast thickness, mean glandular dose is the energy deposited per unit mass of glandular tissue (by far the most radiosensitive tissue in the breast) averaged over all the glandular tissue in the breast (i.e., the mean absorbed dose to glandular tissue). The mean glandular dose should be <3 mGy for a single screen-film craniocaudal view of a standard (4.2 cm thick, 50 percent glandular, 50 percent adipose) breast. The mean glandular dose is the value used to estimate the radiation risk of the exposure.

medical audit: Systematic collection and analysis of mammography results, comparing those results with outcomes data.

mediolateral-oblique (MLO) view: Now one of the standard two views of the breast. The image receptor is angled 30 to 60 degrees from horizontal so that the cassette assembly is parallel to the pectoral muscle and the corner of the cassette holder fits comfortably into the axilla. The x-ray beam is directed from the superomedial to the inferolateral aspect of the breast. mediolateral view: Previously, one of the more common routine views for mammography in addition to the craniocaudal view. The image receptor is placed lateral to the breast, and the horizontal x-ray beam is directed from medial to lateral aspect through the breast. metastasis: The spread of cancer from the place where it arises to another part of the body. microcalcifications: Tiny white specks of calcium salts that can sometimes be seen on a mammogram. In clusters, they can be the only sign of ductal carcinoma in situ or early invasive cancer, or they can be associated with benign breast changes (also called calcifications). milliampere seconds (mAs): The product of electron current (milliampere) and the exposure time (in seconds). For a fixed operating potential, total x-ray output is linearly proportional to milliampere seconds. milliampere (mA) setting: The electron current (milliampere) passing from the cathode to the anode in an x-ray tube. For a fixed operating potential, the output of x rays per unit time from the tube is linearly proportional to the milliampere setting. nipple discharge: Secretion of fluid from the nipple, either spontaneously or elicited from the nipple area. Nipple discharge (other than milk in a lactating woman) often results from benign breast changes or minor hormonal irregularities but, if spontaneous, needs to be checked by a health professional. nodularity: General lumpiness of normal textured tissue consistency, often bilateral.

nodule: A discrete small lump as opposed to normal nodularity. Nyquist frequency: Equal to one-half the sampling frequency (Nyguist theorem). Frequencies higher than the Nyquist frequency cannot be accurately reproduced. operating level: The central value about which we expect day-to-day measurements to fluctuate: for example, the empirically determined mid-density on a sensitometric film. operating potential: (see also kilovolt peak). The potential difference between the anode and cathode of an x-ray tube. palpation: Generally, examination by touch; the part of breast examination during which the breast tissue and structures are felt with the finger pads.

phantom: A test object that simulates the average composition of and various structures within the patient. A "good breast phantom" should simulate the breast, should allow objective rather than subjective analysis, and should be sensitive to small changes in mammographic image quality.

positioning: The maneuvers the radiologic technologist uses to place the breast in the desired position on the film for a specific mammographic view.

positron emission tomography (PET): A nuclear medicine procedure that utilizes a positron emitting radionuclide to visualize various tissue and/or organ abnormalities. processor: An automated device that transports film at a constant speed by a system of rollers through developing, fixing, washing and drying cycles.

processor artifact: Any unwanted or artificial image feature appearing on a radiograph due to malfunction or misuse of the film processor. projection: The direction of the central ray (e.g., mediolateral, craniocau-

dal) in an x-ray exam. provider: Referring physician or other health care professional who refers women for mammography (e.g., family practice physician, nurse practitioner, physician's assistant). quality assurance (QA): A management tool that includes policies and procedures (including quality control tests and tasks) designed to optimize the performance of facility personnel and equipment. quality control (QC): The routine performance of tests and tasks and the interpretation of data from the tests of equipment function and the corrective actions taken. quality control technologist: The technologist assigned the task of QC testing and maintaining QC records for radiographic imaging systems. radiation weighting factor: A factor used for radiation-protection purposes that accounts for differences in biological effectiveness between different radiations. The radiation weighting factor (wR) is independent of the tissue weighting factor (wT). radiographic noise: Unwanted fluctuations in optical density on the mammographic image. radiographic sharpness: The distinctness or perceptibility of the edge or boundary of the structure in a radiograph. radiopaque: Not penetrable by x rays or other forms of radiant energy;

radiopaque areas appear light or white on the exposed film. relative risk (RR): The mortality rate in women who have a risk factor divided by the mortality rate due to breast cancer in women who do not have the risk factor. repeat analysis: A systematic approach to determine the number of and causes for radiographs being repeated. Analysis of data on repeats helps identify ways to improve mammography quality. replenishment rate: The amount of chemicals added per sheet of film processed in order to maintain the proper chemical activity of developer and fixer solutions. safelight: A lighting fixture used to provide a minimal amount of working light in a darkroom. A safelight has appropriate filters and produces light that will not fog exposed radiographic film within a specified period of time. The filter removes most of the light to which the radiographic film is sensitive. Most safelights will fog film if the amount of light (wattage of the bulb) is excessive, if the filter is damaged or of the wrong type, or if the time a film is exposed to the safelight is too long. screen: Phosphor crystals coated on a plastic support that emit light when exposed to radiation. The light emitted by the screen exposes the film that is in contact with the screen creating a latent image on x-ray film.

screen-film combination: A particular intensifying screen used with a particular type of film. Care must be taken to match the number of screens (one or two) to the number of sides of the film on which emulsion is coated and to match the light output spectrum of the screen to the light sensitivity of the film. screen-film contact: The close proximity of the intensifying screen to the emulsion of the film. Good screen-film contact is essential in order to achieve a sharp image on the film. screen-film mammography. Mammography performed with a highdetail intensifying screen(s) that is in close contact with matched film in the cassette, both of which are designed for breast imaging. screening mammography: X-ray breast examination of asymptomatic women in an attempt to detect breast cancer when it is small, nonpal-pable and confined to the breast. sensitivity: The probability of detecting a cancer when a cancer exists, otherwise defined as the fraction of all patients found to have breast cancer within 1 y of screening who were correctly diagnosed as being suspicious for breast cancer at the screening session. sensitometer: A device used to reproducibly expose film to a number of different known levels of light intensity. The film produced by the use of a sensitometer is used to check the consistency of performance of a film processor.

sensitometric strip: A sheet of film exposed to a series of different light intensities by a sensitometer. Such strips are used to measure the range of densities, from minimum to maximum, resulting from a reproducible exposure. sensitometry: A quantitative measurement of the response of film to light exposure and photographic processing. Sestamibi scintimammography: Sestamibi (cardiolite) labeled with 99mTc. Scintimammography is used to visualize some types of breast cancer utilizing a gamma camera. sievert (Sv): The special name for the SI units of dose equivalent (H) and equivalent dose (H^)-spatial resolution: The ability to image two separate objects and visually detect one from the other. specificity: The probability of a normal mammogram report when no cancer exists, otherwise defined as the fraction of all patients found not to have breast cancer within 1 y of screening who were correctly identified as normal at the time of screening.

specimen radiography: The technique for examining a biopsy specimen by x-ray imaging.

spot compression: Allows for greater reduction in thickness of the localized area of interest and improved separation of breast tissues by the use of a small compression device; requires collimation to the area of interest (also called coned compression). sterotactic breast biopsy: Breast biopsy performed with location of the area to be biopsied determined by utilizing two x-ray images in parallax.

stochastic effects: Effects, the probability of which, rather than their severity is a function of dose without threshold. thermography: A breast imaging technique that measures body heat at the skin surface to identify hot spots caused by inflammation or cancer.

thermoluminescent dosimeter (TLD): A radiation exposure measurement device using a chip or powder that absorbs radiation and when subsequently heated produces light whose intensity is proportional to the amount of radiation absorbed. "Film" badges worn by x-ray personnel typically contain TLDs. tissue weighting factor (wT): A factor for a particular tissue representing the fraction of the detriment (cancer) plus hereditary effects attributed to that tissue when the whole body is irradiated uniformly. transillumination: A noninvasive breast imaging technique that uses visible or near-visible light in an attempt to visualize breast masses. ultrasonography: The use of sonic energy (sound) to produce a pictorial representation of the internal structure of the breast. The image is produced by pulse-echo techniques, with detection and display of tissue interfaces rather than densities. unsharpness: The inability of an x-ray imaging system to clearly define an edge on the final image (also called blur). view: The image of the breast on the film resulting from projection of the x-ray beam and the breast-positioning maneuvers performed by the radiologic technologist; usually named according to the direction of the x-ray beam relative to the breast (e.g., mediolateral, craniocaudal). viewbox: A device providing a relatively uniform surface luminance for viewing mammographic films. Mammographic viewboxes should have a luminance level of at least 3,000 candela per square meter (cd m-2 or nit).

x rays: The electromagnetic radiations emitted in the de-excitation of bound atomic electrons referred to as characteristic x rays, or the electromagnetic radiation produced in the deceleration of energetic charged particles in passing through matter such as continuous x rays from the deceleration of electrons in a cathode-ray tube (x-ray tube) or bremsstrahlung from the deceleration of high-energy beta particles.

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