La. Admin. Code tit. 33, § XV-602 - Definitions
Accessible Surface- the external surface of the enclosure or housing provided by the manufacturer.
Added Filtration- any filtration that is in addition to the inherent filtration.
Air Kerma (K)-the kinetic energy released in air by ionizing radiation. Kerma is determined as the quotient of dE by dM, where dE is the sum of the initial kinetic energies of all the charged ionizing particles liberated by uncharged ionizing particles in air of mass dM. The SI unit of air kerma is joule per kilogram and the special name for the unit of kerma is the gray (Gy).
Air Kerma Rate (AKR)-air kerma per unit time.
Alert Value-a dose rate index (e.g. of CTDIvol(mGy) or DLP(mGy-cm)) that is set by the registrant to trigger an alert to the CT operator prior to scanning within an ongoing examination. The alert value represents a universal dose index value well above the registrant's established range for the examination that warrants more stringent review and consideration before proceeding.
Aluminum Equivalent-the thickness of type 1100 aluminum alloy affording the same attenuation, under specified conditions, as the material in question.
Articulated Joint-a joint between two separate sections of a tabletop which joint provides the capacity of one of the sections to pivot on the line segment along which the sections join.
Assembler- any person engaged in the business of assembling, replacing, or installing one or more components into an X-ray system or subsystem. The term includes the owner of an X-ray system or his or her employee or agent who assembles components into an X-ray system that is subsequently used to provide professional or commercial services.
Attenuation Block- a block or stack, having dimensions 20 centimeters by 20 centimeters by 3.8 centimeters, of type 1100 aluminum alloy or other materials having equivalent attenuation.
Automatic Exposure Control- a device that automatically controls one or more technique factors in order to obtain at a preselected location or locations a required quantity of radiation (see also Phototimer).
Attenuation Block-a block or stack of type 1100 aluminum alloy, or aluminum alloy having equivalent attenuation, with dimensions 20 centimeters or larger by 20 centimeters or larger by 3.8 centimeters, that is large enough to intercept the entire X-ray beam.
Automatic Exposure Control (AEC)-a device which automatically controls one or more technique factors in order to obtain at a preselected location(s) a required quantity of radiation (see also Phototimer).
Automatic Exposure Rate Control (AERC)-a device which automatically controls one or more technique factors in order to obtain, at a preselected location(s), a required quantity of radiation per unit time.
Barrier-(See Protective Barrier)
Beam Axis- a line from the source through the centers of the X-ray fields.
Beam-Limiting Device- a device that provides a means to restrict the dimensions of the X-ray field.
Beam Monitoring System- a system designed to detect and measure the radiation present in the useful beam.
Bone Densitometer-a device intended for medical purposes to measure bone density and mineral content by X-ray or gamma ray transmission measurements through the bone and adjacent tissues. This generic type of device may include signal analysis and display equipment, patient and equipment supports, component parts, and accessories.
Bone Densitometry-a noninvasive measurement of certain physical characteristics of bone that reflect bone strength. Test results are typically reported as bone mineral content or density and are used for diagnosing osteoporosis, estimating fracture risk, and monitoring changes in bone mineral content.
C Arm X-Ray System- an X-ray system in which the image receptor and X-ray tube housing assembly are connected by a common mechanical support system in order to maintain a desired spatial relationship. This system is designed to allow a change in the projection of the beam through the patient without a change in the position of the patient.
Cantilevered Tabletop-a tabletop designed such that the unsupported portion can be extended at least 100 cm beyond the support.
Cassette Holder-a device, other than a spot-film device, that supports and/or fixes the position of the image receptor during a radiographic exposure.
Cephalometric Device- a device intended for the radiographic visualization and measurement of the dimensions of the human head.
Certified Components-components of X-ray systems that are certified by the U.S. Food and Drug Administration (FDA).
Changeable Filters- any filter, exclusive of inherent filtration, that can be removed from the useful beam through any electronic, mechanical, or physical process.
Coefficient of Variation or "C"-Repealed.
Coefficient of Variation (C)-the ratio of the standard deviation to the mean value of a population of observations. It is estimated using the following equation:
where:
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s = estimated standard deviation of the population;
x = mean value of observations in sample;
xi = ith observation in sample; and
n = number of observations sampled.
Computed Radiography (CR; also see DR)-a digital X-ray imaging method in which a photostimulable phosphor is used to capture and store a latent image. The latent image is read out by stimulating the phosphor with a laser. Computed radiography systems may use cassettes to house the phosphor, or it may be integrated into a digital radiography system.
Computed Tomography (CT)-the production of a tomogram by the acquisition and computer processing of X-ray transmission data.
Computed Tomography Dose Index (CTDI)-the average absorbed dose, along the z-axis, from a series of contiguous irradiations. It is measured from one axial CT scan (one rotation of the X-ray tube), and is calculated by dividing the integrated absorbed dose by the nominal total beam collimation. The scattering media for CTDI consist of two (16 and 32 cm in diameter) polymethylmethacrylate (PMMA, e.g., acrylic or Lucite) cylinders. The equation is:
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where:
D(z) = the radiation dose profile along the z-axis;
N = the number of tomographic sections imaged in a single axial scan. This is equal to the number of data channels used in a particular scan. The value of N may be less than or equal to the maximum number of data channels available on the system; and
T = the width of the tomographic section along the z-axis imaged by one data channel. In multiple-detector-row (multislice) CT scanners, several detector elements may be grouped together to form one data channel. In single-detectorrow (single-slice) CT, the z-axis collimation (T) is the nominal scan width.
CTDI100-the accumulated multiple scan dose at the center of a 100-mm scan and underestimates the accumulated dose for longer scan lengths. It is thus smaller than the equilibrium dose. The CTDI100, requires integration of the radiation dose profile from a single axial scan over specific integration limits. In the case of CTDI100, the integration limits are +50 mm, which corresponds to the 100-mm length of the commercially available "pencil" ionization chamber. CTDI100 is acquired using a 100-mm long, 3-cc active volume CT "pencil" ionization chamber and one of the two standard CTDI acrylic phantoms (16 and 32 cm diameter) and a stationary patient table. The equation is:
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CTDIvol-see volume Computed Tomography Dose Index (CTDIvol)/
CTDIw-see Weighted Computed Tomography Dose Index (CTDIw).
Cone Beam Computed Tomography (CBCT)-a volumetric imaging modality. volumetric data are acquired using two dimensional digital detector arrays, and a coneshaped (instead of fan-shaped) X-ray beam that rotates around the patient. Reconstruction algorithms can be used to generate images of any desired plane.
Contact Therapy System- an X-ray system used for therapy with the X-ray tube port placed in contact with or within 5 centimeters of the surface being treated.
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where:
[MICRO] x = linear attenuation coefficient of the material of interest;
[MICRO] w = linear attenuation coefficient of water;
(CTN)x = CTN of the material of interest; and
(CTN)w = CTN of water.
Control Panel-that part of the X-ray control upon which are mounted the switches, knobs, pushbuttons, keypads, touchscreens, and other hardware necessary for manually setting the technique factors.
Cooling Curve- the graphical relationship between heat units stored and cooling time.
Cradle-a removable device which supports and may restrain a patient above an X-ray table; or a device:
CS-see Contrast Scale.
CT-see Computed Tomography.
CT Conditions of Operation-all selectable parameters governing the operation of a CT X-ray system including, but not limited to, nominal tomographic section thickness, filtration, and the technique factors as defined in LAC 33:XV.602.
CT Gantry-the tube housing assemblies, beam-limiting devices, detectors, and the supporting structures and frames that hold these components.
CTN-see CT Number.
CT Number-the number used to represent the X-ray attenuation associated with each elemental area of the CT image. The equation is:
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where:
k = a constant. The constant has a normal value of 1,000 when the Hounsfield unit of CTN is used;
[MICRO] x = linear attenuation coefficient of the material of interest; and
[MICRO] w = linear attenuation coefficient of water.
Cumulative Air Kerma-the total air kerma accrued from the beginning of an examination or procedure and includes all contributions from fluoroscopic and radiographic irradiation.
Dead-Man Switch- a switch so constructed that a circuit closing contact can be maintained only by continuous pressure on the switch by the operator.
Detector-(See Radiation Detector)
Diagnostic Reference Level (DRL)-an investigational level used to identify unusually high radiation doses or dose rates for common medical X-ray imaging procedures. DRLs are suggested action levels above which a facility should review its methods and determine if acceptable image quality can be achieved at lower doses. DRLs should not be applied to an individual patient.
Diagnostic Source Assembly- the tube housing assembly with a beam-limiting device attached.
Diagnostic-Type Tube Housing- a tube housing so constructed that the leakage radiation measured at a distance of 1 meter from the source does not exceed 100 mR in one hour when the tube is operated at its leakage technique factors.
Diagnostic X-Ray Imaging System- an assemblage of components for the generation, emission, and reception of X-rays and the transformation, storage, and visual display of the resultant X-ray image.
Diagnostic X-Ray System- an X-ray system designed for irradiation of any part of the human or animal body for the purpose of diagnosis or visualization.
Digital Radiography (DR)-an X-ray imaging method (or radiography) which produces a digital rather than analog image. DR includes both computed radiography and direct digital radiography.
Direct Digital Radiography (DDR; also see CR and DR)-an X-ray imaging method in which a digital sensor, usually incorporating a thin-film transistor, is used to capture an X-ray image. Some DDR systems use a scintillator to convert X-rays to light and a photodiode array to convert light to charge, while others use a photoconductor to convert X-rays directly to charge, which is stored on the thin-film transistor.
Direct Scattered Radiation-that scattered radiation which has been deviated in direction only by materials irradiated by the useful beam. (See Scattered Radiation)
Direct Supervision-general supervision by a qualified practitioner present in the facility and immediately available to furnish assistance and direction throughout the performance of the procedure. It does not mean that the licensed practitioner shall be present in the room when the procedure is being performed.
Dose-the absorbed dose as defined by the International Commission on Radiation Units and Measurements. The absorbed dose, D, is the quotient of de by dm, where de is the mean energy imparted to matter of mass dm; thus D=de/dm, in units of J/kg, where the special name of the unit of absorbed dose is gray (Gy).
Dose Area Product (DAP) (aka Kerma-Area Product (KAP))-the product of the air kerma and the area of the irradiated field and is typically expressed in Gy-cm2, so it does not change with distance from the X-ray tube.
Dose Length Product (DLP)-the indicator of the integrated radiation dose from a complete CT examination. It addresses the total scan length by the formula:
DLP (mGy-cm) = CTDIvol (mGy) x scan length (cm)
Dose Profile-the dose as a function of position along a line.
Effective Dose (E)-the sum of the tissue-weighted equivalent doses for the radiosensitive tissues and organs of the body. It is given by the expression E = ÎT (wT HT), in which HT is the equivalent dose in tissue or organ T and wT is the tissue weighting factor for tissue or organ T. The unit of E and HT is joule per kilogram (J/kg), with the special name sievert (Sv).
Elemental Area-the smallest area within a tomogram for which the X-ray attenuation properties of a body are depicted. (See also Picture Element)
Entrance Exposure Rate- the exposure free in air per unit time at the point where the center of the useful beam enters the patient.
Equipment-(See X-Ray Equipment)
Exposure (X)-the quotient of dQ by dm where "dQ" is the absolute value of the total charge of the ions of one sign produced in air when all the electrons and positrons liberated or created by photons in air of mass "dm" are completely stopped in air; thus X=dQ/dm, in units of C/kg. Exposure is also the process or condition during which the X-ray tube produces X-ray radiation.
Field Emission Equipment- equipment that uses an X-ray tube in which electron emission from the cathode is due solely to the action of an electric field.
Filter- material placed in the useful beam to absorb preferentially selected radiations.
Fluoroscopic Imaging Assembly-a subsystem in which X-ray photons produce a set of fluoroscopic images or radiographic images recorded from the fluoroscopic image receptor. It includes the image receptor(s), electrical interlocks, if any, and structural material providing linkage between the image receptor and diagnostic source assembly.
Fluoroscopic Irradiation Time-the cumulative duration during an examination or procedure of operator-applied continuous pressure to the device, enabling X-ray tube activation in any fluoroscopic mode of operation.
Fluoroscopically-Guided Interventional (FGI) Procedures-an interventional diagnostic or therapeutic procedure performed via percutaneous or other access routes, usually with local anesthesia or intravenous sedation, which uses external ionizing radiation in the form of fluoroscopy to localize or characterize a lesion, diagnostic site, or treatment site, to monitor the procedure, and to control and document therapy.
Fluoroscopy-a technique for generating X-ray images and presenting them simultaneously and continuously as visible images. This term has the same meaning as the term "radioscopy" in the standards of the International Electrotechnical Commission.
Focal Spot (actual)-the area projected on the anode of the X-ray tube bombarded by the electrons accelerated from the cathode and from which the useful beam originates.
General Purpose Radiographic X-Ray System- any radiographic X-ray system that, by design, is not limited to radiographic examination of specific anatomical regions.
General Supervision-supervision of a procedure under the overall direction and control of the qualified practitioner but who is not required to be physically present during the performance of the procedure.
Gonad Shield-Repealed.
Half-Value Layer-the thickness of specified material that attenuates the beam of radiation to an extent that the exposure rate is reduced by one half. In this definition, the contribution of all scattered radiation, other than any that might be present initially in the beam concerned, is deemed to be excluded.
Hand-Held X-Ray Equipment-X-ray equipment that is designed to be hand-held during operation.
Healing Arts Screening- the testing of human beings using X-ray machines for the detection or evaluation of health indications when such tests are not specifically and individually ordered by a licensed practitioner of the healing arts legally authorized to prescribe such X-ray tests for the purpose of diagnosis or treatment.
Heat Unit-a unit of energy equal to the product of the peak kilovoltage, milliamperes, and seconds, i.e., kVp x mA x second.
HVL-(See Half-Value Layer)
Image Intensifier-a device, installed in its housing, that instantaneously converts an X-ray pattern into a corresponding light image of higher intensity.
Image Receptor-any device, such as a fluorescent screen, radiographic film, X-ray image intensifier tube, solid-state detector, or gaseous detector, that transforms incident X-ray photons either into a visible image or into another form that can be made into a visible image by further transformations. In those cases where means are provided to preselect a portion of the image receptor, the term image receptor shall mean the preselected portion of the device.
Image Receptor Support- for mammographic systems, that part of the system designed to support the image receptor during mammography.
Inherent Filtration- the filtration of the useful beam provided by the permanently installed components of the tube housing assembly.
Irradiation- the exposure of matter to ionizing radiation.
Isocenter-the center of the smallest sphere through which the beam axis passes when the equipment moves through a full range of rotations about its common center.
Kerma-a measurement defined by the International Commission on Radiation Units and Measurements. The kerma, K, is the quotient of dEtr by dm, where dEtr is the sum of the initial kinetic energies of all the charged particles liberated by uncharged particles in a mass dm of material; thus K=dEtr/dm, in units of J/kg, where the special name for the unit of kerma is gray (Gy). When the material is air, the quantity is referred to as "air kerma."
Kerma-Area Product (KAP)-see Dose Area Product.
Kilovolts Peak-(See Peak Tube Potential)
kVp-see Peak Tube Potential.
Kw*s- kilowatt second.
Last-Image Hold (LIH) Radiograph-an image obtained either by retaining one or more fluoroscopic images, which may be temporarily integrated, at the end of a fluoroscopic exposure or by initiating a separate and distinct radiographic exposure automatically and immediately in conjunction with termination of the fluoroscopic exposure.
Lead Equivalent-the thickness of the material in question affording the same attenuation, under specified conditions, as lead.
Leakage Radiation- radiation emanating from the diagnostic or therapeutic source assembly except for:
Leakage Technique Factors- the technique factors associated with the diagnostic or therapeutic source assembly that are used in measuring leakage radiation. They are defined as follows:
Licensed Practitioner-a person licensed or otherwise authorized by law to practice medicine, dentistry, chiropractic, osteopathy or podiatry, or a licensed nurse practitioner, or physician assistant.
Light Field- that area of the intersection of the light beam from the beam-limiting device and one of the sets of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the illumination is 1/4 of the maximum in the intersection.
Line-voltage Regulation- the difference between the no-load and the load line potentials expressed as a percentage of the load line potential. It is calculated using the following equation.
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where:
Vn = no-load line potential; and
V1 = load line potential.
mA-milliampere.
mAs-milliampere second.
Mammography Physicist- an individual who has submitted credentials to the department and who satisfies one or more of the following criteria:
Maximum Line Current- the root-mean-square current in the supply line of an X-ray machine operating at its maximum rating.
Medical Event-one or more of the criteria that are listed in LAC 33:XV.613 have occurred.
Mobile X-Ray Equipment-(See X-Ray Equipment)
Mode of Operation-for fluoroscopic systems, a distinct method of fluoroscopy or radiography provided by the manufacturer and selected with a set of several technique factors or other control settings uniquely associated with the mode. The set of distinct technique factors and control settings for the mode may be selected by the operation of a single control. Distinct modes of operation include normal fluoroscopy (analog or digital), high-level control fluoroscopy, cineradiography (analog and digital), digital subtraction angiography, electronic radiography using the fluoroscopic image receptor, and photospot recording. In a specific mode of operation, certain system variables affecting kerma, AKR, or image quality, such as image magnification, X-ray field size, pulse rate, pulse duration, number of pulses, source-image receptor distance (SID), or optical aperture, may be adjustable or may vary; their variation per se does not comprise a mode of operation different from the one that has been selected.
Multiple Tomogram System-a computed tomography X-ray system that obtains X-ray transmission data simultaneously during a single scan to produce more than one tomogram.
Noise-the standard deviation of the fluctuations in CTN expressed as a percentage of the attenuation coefficient of water. Its estimate (Sn) is calculated using the following expression:
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where:
CS = contrast scale;
[MICRO] w = linear attenuation coefficient of water; and
s = estimated standard deviation of the CTN of picture elements in a specified area of the CT image.
Nominal Tomographic Section Thickness-the full width at half-maximum of the sensitivity profile taken at the center of the cross-sectional volume over which X-ray transmission data are collected.
Operator- an individual who, under the supervision of a practitioner of the healing arts, physically positions patients or animals, determines exposure parameters, and applies the radiation for the diagnostic or therapeutic purposes intended. See the definition of supervision in LAC 33:XV.110.E.
Patient- an individual or animal subjected to healing arts examination, diagnosis, or treatment.
PBL-see Positive Beam Limitation.
Peak Tube Potential (kVp)-the maximum value of the potential difference across the X-ray tube during an exposure.
Personal Supervision-general supervision by a qualified practitioner present in the room or adjacent control area during the performance of the procedure.
Phantom- a volume of material behaving in a manner similar to tissue with respect to the attenuation and scattering of radiation. This requires that both the atomic number (Z) and the density of the material be similar to that of tissue.
Photostimulable Storage Phosphor (PSP)-a material used to capture and store radiographic images in computed radiography systems.
Phototimer- a method for controlling radiation exposures to image receptors by measuring the amount of radiation that reaches a radiation monitoring device or devices. The radiation monitoring device or devices are part of an electronic circuit that controls the duration of time the tube is activated (see Automatic Exposure Control).
PID-see Position Indicating Device.
Picture Element-an elemental area of a tomogram.
Pitch-the table incrementation, in CT, per X-ray tube rotation, divided by the nominal X-ray beam width at isocenter.
Portable X-Ray Equipment-(See X-Ray Equipment)
Position Indicating Device (PID)-a device on dental X-ray equipment used to indicate the beam position and to establish a definite source-surface (skin) distance. It may or may not incorporate or serve as a beam-limiting device.
Positive Beam Limitation (PBL)-the automatic or semiautomatic adjustment of an X-ray beam to the selected image receptor size, whereby exposures cannot be made without such adjustment.
Protected Area-an area shielded with primary or secondary protective barriers or an area removed from the radiation source such that the exposure rate within the area due to normal operating procedures and workload does not exceed any of the following limits:
Protective Apron-an apron made of radiation absorbing or lead equivalent materials used to reduce radiation exposure.
Protective Barrier (Primary Protective Barrier)-a barrier of radiation absorbing material(s) used to reduce radiation exposure. The types of protective barriers are as follows:
Protocol-a collection of settings and parameters that fully describe an examination.
Protective Glove- a glove made of radiation absorbing materials used to reduce radiation exposure.
Pulsed Mode-operation of the X-ray system such that the X-ray tube current is pulsed by the X-ray control to produce one or more exposure intervals of duration less than one-half second.
Qualified Expert-an individual who meets one of the following criteria:
Qualified Medical Physicist (QMP)-an individual who meets each of the following credentials:
Qualified Practitioner-an individual who is qualified by education, training, licensure/regulation (when applicable), and facility privileging (when applicable) who performs a professional service within his/her scope of practice and independently reports that professional service.
Quality Assurance (QA)-a program providing for verification by written procedures such as testing, auditing, and inspection to ensure that deficiencies, deviations, defective equipment, or unsafe practices, or a combination thereof, relating to the use, disposal, management, or manufacture of radiation devices are identified, promptly corrected, and reported to the appropriate regulatory authorities as required.
Quality Control (QC)-the routine measurement of image quality and the performance of the diagnostic X-ray imaging system, from X-ray beam output to the viewing of radiographs, and the continual adjustment of that performance to an optimal and consistent level.
Qualified Expert- an individual who has demonstrated to the satisfaction of the department that such individual possesses the knowledge, training, and experience to measure ionizing radiation, to evaluate safety techniques, and to advise regarding radiation protection needs.
Radiation Detector- a device that in the presence of radiation provides a signal or other indication suitable for use in measuring one or more quantities of incident radiation.
Radiation Protocol Committee (RPC)-the representative group of qualified individuals in a CT or FGI facility responsible for the ongoing review and management of CT or FGI protocols to ensure that exams being performed achieve the desired diagnostic image quality at the lowest radiation dose possible while properly exploiting the capabilities of the equipment being used.
Radiation Therapy Simulation System- a radiographic or fluoroscopic X-ray system intended for localizing the volume to be exposed during radiation therapy and confirming the position and size of the therapeutic irradiation field.
Radiography-a technique for generating and recording an X-ray pattern for the purpose of providing the user with an image(s) after termination of the exposure.
Radiographic Imaging System- any system whereby a permanent or temporary image is recorded on an image receptor by the action of ionizing radiation.
Rating- the operating limits as specified by the component manufacturer.
Recording-producing a permanent or retrievable form of an image resulting from X-ray photons.
Reference Plane-a plane that is displaced from and parallel to the tomographic plane.
Registrant- as used in this Chapter, any person who owns or possesses and administratively controls an X-ray system that is used to deliberately expose humans or animals to the useful beam of the system and is required by the provisions contained in LAC 33:XV.Chapters 1 and/or 2 to register with the administrative authority.
Scan-the complete process of collecting X-ray transmission data for the production of a tomogram. Data can be collected simultaneously during a single scan for the production of one or more tomograms.
Scan Increment-the amount of relative displacement of the patient with respect to the CT X-ray system between successive scans measured along the direction of such displacement.
Scan Sequence-a preselected set of two or more scans performed consecutively under preselected CT conditions of operation.
Scan Time-the period of time between the beginning and end of X-ray transmission data accumulation for a single scan.
Scattered Radiation- radiation that, during passage through matter, has deviated in direction (see Direct Scattered Radiation).
Sensitivity Profile-the relative response of the CT X-ray system as a function of position along a line perpendicular to the tomographic plane.
Secondary Dose Monitoring System- a system that will terminate irradiation in the event of failure of the primary system.
Secondary Protective Barrier-(See Protective Barrier)
SID-see Source-Image Receptor Distance.
Single Tomogram System-a CT X-ray system that obtains X-ray transmission data during a scan to produce a single tomogram.
Size-Specific Dose Estimate (SSDE)-a patient dose estimate which takes into consideration corrections based on the size of the patient, using linear dimensions measured on the patient or patient images.
Shutter- a device attached to the tube housing assembly that can intercept the entire cross sectional area of the useful beam and that has a lead equivalency not less than that of the tube housing assembly.
Source-the focal spot of the X-ray tube or the region and/or material from which the radiation emanates.
Source-Image Receptor Distance (SID)- the distance from the source to the center of the input surface of the image receptor.
Spot Check- a procedure performed to assure that a previous calibration continues to be valid.
Spot Film- a radiograph made during a fluoroscopic examination to permanently record conditions that exist during that fluoroscopic procedure.
Spot Film Device- a device intended to transport and/or position a radiographic image receptor between the X-ray source and fluoroscopic image receptor. The term includes a device intended to hold a cassette over the input end of an image intensifier for the purpose of making a radiograph.
Source-Skin Distance (SSD)-the distance from the source to the center of the entrant X-ray field in the plane tangent to the patient skin surface.
Spot Film Device-a device intended to transport and/or position a radiographic image receptor between the X-ray source and fluoroscopic image receptor. The term includes a device intended to hold a cassette over the input end of the fluoroscopic image receptor for the purpose of producing a radiograph.
Stationary X-Ray Equipment-(See X-Ray Equipment)
Stray Radiation- the sum of leakage and scattered radiation.
Substantial Radiation Dose Level (SRDL)-an appropriately-selected dose used to trigger additional dosemanagement actions during a procedure and medical follow up for a radiation level that might produce a clinically-relevant injury in an average patient.
Technique Factors- the following conditions of operation:
Termination of Irradiation- the stopping of irradiation in a fashion that will not permit continuance of irradiation without the resetting of operating conditions at the control panel.
Therapeutic-Type Protective Tube Housing- the tube housing with tube installed. It includes high voltage and/or filament transformers and other appropriate elements when they are contained within the tube housing.
Tomographic Plane-that geometric plane identified as corresponding to the output tomogram.
Tomographic Section-the volume of an object whose X-ray attenuation properties are imaged in a tomogram.
Traceable to a National Standard- refers to a quantity or a measurement that has been compared to a national standard directly or indirectly through one or more intermediate steps, and all comparisons have been documented.
Tube- an X-ray tube, unless otherwise specified.
Tube Housing Assembly- the tube housing with tube installed. It includes high-voltage and/or filament transformers and other appropriate elements when such are contained within the tube housing.
Tube Rating Chart- the set of curves that specify the rated limits of operation of the tube in terms of the technique factors.
Unintended-a radiation dose received by a patient in diagnostic or interventional X-ray resulting from human error or equipment malfunction during a procedure.
Unprotected Area- any area in which the exposure rate, due to the use of the radiation machine under normal operating procedures and workloads, exceeds any of the following limits:
Useful Beam-the radiation which passes through the tube housing port and the aperture of the beam-limiting device when the exposure switch or timer is activated.
Variable-Aperture Beam-Limiting Device- a beam-limiting device that has the capacity for stepless adjustment of the X-ray field size at a given SID.
Visible Area- that portion of the input surface of the image receptor over which incident X-ray photons are producing a visible image.
volume Computed Tomography Dose Index (CTDI vol)-a radiation dose parameter derived from the CTDIw (weighted or average CTDI given across the field of view). The equation is:
CTDIvol = (N)(T)(CTDIw)/I, where
N = number of simultaneous axial scans per X-ray source rotation;
T = thickness of one axial scan (mm); and
I = table increment per axial scan (mm).
Or, for helical scans,
CTDIvol = CTDIw / pitch
Wedge Filter-an added filter effecting continuous progressive attenuation on all or part of the useful beam.
Weighted Computed Tomography Dose Index (CTDIw)-the estimated average CTDI100 across the field of view (FOV). The equation is:
CTDIw = 1/3CTDI100, center + 2/3CTDI100, edge.
Where 1/3 and 2/3 approximate the relative areas represented by the center and edge values derived using the 16 or 32 cm acrylic phantom. CTDIw uses CTDI100 and an f-factor for air (0.87 rad/R or 1.0 mGy/mGy).
X-Ray Control- a device that controls input power to the X-ray high-voltage generator and/or the X-ray tube. It includes equipment such as timers, phototimers, automatic brightness stabilizers, and similar devices, which control the technique factors of an X-ray exposure.
X-Ray Equipment-an X-ray system, subsystem, or component thereof. Types of X-ray equipment are as follows:
X-Ray Exposure Control-a device, switch, button or other similar means by which an operator initiates and/or terminates the radiation exposure. The X-ray exposure control may include such associated equipment as timers and back-up timers.
X-Ray Equipment- an X-ray system, subsystem, or component thereof. Types of X-ray equipment are as follows:
X-Ray Field-that area of the intersection of the useful beam and any one of the set of planes parallel to and including the plane of the image receptor, whose perimeter is the locus of points at which the AKR is one-fourth of the maximum in the intersection.
X-Ray High-voltage Generator- a device that transforms electrical energy from the potential supplied by the X-ray control to the tube operating potential. The device may also include means for transforming alternating current to direct current, filament transformers for the X-ray tube(s), high-voltage switches, electrical protective devices, and other appropriate elements.
X-Ray Subsystem- any combination of two or more components of an X-ray system.
X-Ray System- an assemblage of components for the controlled production of X-rays. It includes minimally an X-ray high-voltage generator, an X-ray control, a tube housing assembly, a beam-limiting device, and the necessary supporting structures. Additional components that function with the system are considered integral parts of the system.
X-Ray Table-a patient support device with its patient support structure (tabletop) interposed between the patient and the image receptor during radiography and/or fluoroscopy. This includes, but is not limited to, any stretcher equipped with a radiolucent panel and any table equipped with a cassette tray (or bucky), cassette tunnel, fluoroscopic image receptor, or spot-film device beneath the tabletop.
X-Ray Tube-any electron tube which is designed for the conversion of electrical energy into X-ray energy.
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.