Rhode Island Code of Regulations › Title 216 - Department of health › Chapter 40 - Professional licensing and facility regulation › Subchapter 20 - Radiation › Part 4 - Medical Diagnostic and Interventional X-Ray and Imaging Systems › Section 216-RICR-40-20-4.2 - Definitions

Current through June 14, 2024
A. Whenever used in this Part, the following
				  terms shall be construed as follows:
1.
				  "Accessible surface" means the external surface of the enclosure or housing of
				  the radiation producing machine as provided by the manufacturer.
2. "Act" means R.I. Gen. Laws Chapter
				  23-1.3, entitled "Radiation
				  Control."
3. "Agency" means Rhode
				  Island Radiation Control Agency (RCA), Center for Health Facilities Regulation
				  - Radiation Control Program, Rhode Island Department of Health.
4. "Air kerma" means kerma in air (see
				  definition of Kerma).
5. "Air kerma
				  rate" or "AKR" means the air kerma per unit time.
6. "Alert value" means a dose 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.
7. "Aluminum equivalent" means the thickness
				  of type 1100 aluminum alloy affording the same attenuation, under specified
				  conditions, as the material in question. [The nominal chemical composition of
				  type 1100 aluminum is ninety-nine percent (99.00%) minimum aluminum, twelve one
				  hundredths of one percent (0.12%) copper.]
8. "Articulated joint" means a joint between
				  two (2) separate sections of a tabletop which joint provides the capacity of
				  one (1) of the sections to pivot on the line segment along which the sections
				  join.
9. "Attenuation block" means
				  a block or stack of type 1100 aluminum alloy, or aluminum alloy having
				  equivalent attenuation, with dimensions twenty centimeters (20 cm) or larger by
				  twenty centimeters (20 cm) or larger by three and eight tenths centimeters (3.8
				  cm), that is large enough to intercept the entire X-ray beam.
10. "Automatic exposure control" or "AEC)"
				  means a device which automatically controls one (1) or more technique factors
				  in order to obtain at a preselected location(s) a required quantity of
				  radiation.
11. "Automatic exposure
				  rate control" or "AERC)" means a device which automatically controls one (1) or
				  more technique factors in order to obtain, at a preselected location(s), a
				  required quantity of radiation per unit time.
12. "Barrier" (See "Primary protective
				  barrier").
13. "Beam axis" means a
				  line from the source through the centers of the X-ray fields.
14. "Beam-limiting device" means a device
				  which provides a means to restrict the dimensions of the X-ray field.
15. "Bone densitometry" means 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.
16. "Bone densitometer" means 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.
17. "C-arm
				  fluoroscope" means a fluoroscopic X-ray system in which the image receptor and
				  the X-ray tube housing assembly are connected or coordinated to maintain a
				  spatial relationship. Such a system allows a change in the direction of the
				  beam axis with respect to the patient without moving the patient.
18. "Cantilevered tabletop" means a tabletop
				  designed such that the unsupported portion can be extended at least one hundred
				  centimeters (100 cm) beyond the support.
19. "Cassette holder" means a device, other
				  than a spot-film device, that supports and/or fixes the position of the image
				  receptor during a radiographic exposure.
20. "Coefficient of variation (C)" means the
				  ratio of the standard deviation to the mean value of a population of
				  observations. It is estimated using the following equation:
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21.
				  "Computed radiography" or "CR" (also see "DR") means a digital X-ray imaging
				  method in which a photo-stimulable 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.
22. "Computed tomography" or "CT" means the
				  production of a tomogram by the acquisition and computer processing of X-ray
				  transmission data.
23. "Computed
				  tomography dose index" or "CTDI" means the average absorbed dose, along the
				  z-axis, from a series of contiguous irradiations. It is measured from one (1)
				  axial CT scan (one (1) 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 (2) (sixteen (16) and thirty-two
				  (32) centimeters in diameter) polymethylmethacrylate (PMMA, e.g., acrylic or
				  Lucite) cylinders of fourteen centimeters (14 cm) length. 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 (1) data channel. In multiple-detector-row (multislice) CT
					 scanners, several detector elements may be grouped together to form one (1)
					 data channel. In single-detector-row (single-slice) CT, the z-axis collimation
					 (T) is the nominal scan width.
24. "CTDI100" means
				  the accumulated multiple scan dose at the center of a one hundred millimeter
				  (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 + fifty
				  millimeters (50 mm), which corresponds to the one hundred millimeters (100 mm)
				  length of the commercially available "pencil" ionization chamber.
				  CTDI100 is acquired using a one hundred millimeter (100
				  mm) long, three (3) cc active volume CT "pencil" ionization chamber and one (1)
				  of the two (2) standard CTDI acrylic phantoms (sixteen (16) and thirty-two (32)
				  centimeters diameter) and a stationary patient table. The equation is:
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25. "Cone
				  beam computed tomography" or "CBCT" means a volumetric imaging modality.
				  Volumetric data are acquired using two-dimensional digital detector arrays, and
				  a cone-shaped X-ray beam (instead of fanshaped) that rotates around the
				  patient. Reconstruction algorithms can be used to generate images of any
				  desired plane.
26. "Control panel"
				  means 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.
27. "Cradle" means:
a. A removable device which supports and may
				  restrain a patient above an X-ray table; or
b. A device:
(1) Whose patient support structure is
				  interposed between the patient and the image receptor during normal
				  use;
(2) Which is equipped with
				  means for patient restraint; and
(3) Which is capable of rotation about its
				  long (longitudinal) axis.
28. "CT conditions of operation" means all
				  selectable parameters governing the operation of a CT X-ray system including
				  nominal tomographic section thickness, filtration, and the technique factors as
				  defined in §
											4.2   of this Part.
29. "CT gantry" means tube housing
				  assemblies, beam-limiting devices, detectors, and the supporting structures,
				  frames, and covers which hold and/or enclose these components within a computed
				  tomography system.
30. "CT number"
				  means the number used to represent the X-ray attenuation associated with each
				  elemental area of the CT image:
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where: k = A constant, a normal value of one thousand
					 (1,000) when the Hounsfield scale of CT number is used;
ux = Linear attenuation coefficient
					 of the material of interest; and
uw = Linear attenuation coefficient
					 of water.
31. "Cumulative
				  air kerma" means the total air kerma accrued from the beginning of an
				  examination or procedure and includes all contributions from fluoroscopic and
				  radiographic irradiation.
32.
				  "Detector" (See "Radiation detector").
33. "Diagnostic reference level" or "DRL"
				  means 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.
34. "Diagnostic source assembly" means the
				  tube housing assembly with a beam-limiting device attached.
35. "Diagnostic X-ray system" means an X-ray
				  system designed for irradiation of any part of the human [or animal] body for
				  the purpose of diagnosis or visualization.
36. "Digital radiography" or "DR" means an
				  X-ray imaging method (or radiography) which produces a digital rather than
				  analog image. DR includes both computed radiography and direct digital
				  radiography.
37. "Direct digital
				  radiography" or "DDR" (also see "CR" and "DR") means 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.
38.
				  "Direct scattered radiation" means that scattered radiation which has been
				  deviated in direction only by materials irradiated by the useful beam (See
				  "Scattered radiation").
39. "Direct
				  supervision" means a qualified licensed practitioner must exercise general
				  supervision and be 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 must be present in the room when the
				  procedure is being performed.
40.
				  "Dose" means 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).
41. "Dose area product,"
				  "DAP," a/k/a "kerma-area product," or "KAP" means 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.
42. "Dose length product" or "DLP" means 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).
43. "Dose profile" means the dose as a
				  function of position along a line.
44. "Effective dose" or "E" means the sum of
				  the tissue-weighted equivalent doses for the radiosensitive tissues and organs
				  of the body. It is given by the expression E = [SIGMA]T (wT HT), in which HT is
				  the equivalent dose in tissue or organ T and w t is the tissue weighting factor
				  for tissue or organ T. The unit of E and H t is joule per kilogram
				  (J·kg-1), with the special name sievert (Sv).
45. "Equipment" (See "X-ray equipment") means
				  X-ray equipment.
46. "Exposure" or
				  "X" means 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. A second meaning of exposure is
				  the process or condition during which the X-ray tube produces X-ray
				  radiation.
47. "Field emission
				  equipment" means equipment which uses an X-ray tube in which electron emission
				  from the cathode is due solely to the action of an electric field.
48. "Filter" means material placed in the
				  useful beam to preferentially absorb selected radiations.
49. "Fluoroscopic imaging assembly" means 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.
50. "Fluoroscopic
				  irradiation time" means 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.
51. "Fluoroscopically-guided interventional
				  procedures" or "FGI procedures" means 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.
52.
				  "Fluoroscopy" means 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.
53.
				  "Focal spot (actual)" means 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.
54.
				  "General purpose radiographic X-ray system" means any radiographic X-ray system
				  which, by design, is not limited to radiographic examination of specific
				  anatomical regions.
55. "General
				  supervision" means the procedure is performed under the overall direction and
				  control of the qualified licensed practitioner but who is not required to be
				  physically present during the performance of the procedure.
56. "Half-value layer" or "HVL" means the
				  thickness of specified material which attenuates the beam of radiation to an
				  extent such that the AKR is reduced by one half (1/2) of its original value. In
				  this definition, the contribution of all scattered radiation, other than any
				  which might be present initially in the beam concerned, is deemed to be
				  excluded.
57. "Healing arts
				  screening" means 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.
58. "Heat
				  unit" means a unit of energy equal to the product of the peak kilovoltage,
				  milliamperes, and seconds, i.e., kVp x mA x second.
59. "Image intensifier" means a device,
				  installed in its housing, which instantaneously converts an X-ray pattern into
				  a corresponding light image of higher intensity.
60. "Image receptor" means any device, such
				  as a fluorescent screen, radiographic film, X-ray image intensifier tube,
				  solid-state detector, or gaseous detector which transforms incident X-ray
				  photons either into a visible image or into another form which 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.
61. "Irradiation" means the exposure of
				  matter to ionizing radiation.
62.
				  "Isocenter" means 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.
63. "Kerma" means
				  the quantity 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."
64. "Kerma-area product" or "KAP" (See "dose
				  area product").
65. "Kilovolts
				  peak" (See "Peak tube potential").
66. "kV" means kilovolts.
67. "kWs" means kilowatt second.
68. "Last-image hold radiograph" or "LIH
				  radiograph" means an image obtained either by retaining one (1) 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.
69. "Lead
				  equivalent" means the thickness of lead affording the same attenuation, under
				  specified conditions, as the material in question.
70. "Leakage radiation" means radiation
				  emanating from the diagnostic source assembly except for:
a. The useful beam; and
b. Radiation produced when the exposure
				  switch or timer is not activated.
71. "Leakage technique factors" means the
				  technique factors associated with the diagnostic source assembly which are used
				  in measuring leakage radiation. They are defined as follows:
a. For diagnostic source assemblies intended
				  for capacitor energy storage equipment, the maximum-rated peak tube potential
				  and the maximum-rated number of exposures in an hour for operation at the
				  maximum-rated peak tube potential with the quantity of charge per exposure
				  being ten (10) millicoulombs (or ten (10) mAs) or the minimum obtainable from
				  the unit, whichever is larger;
b.
				  For diagnostic source assemblies intended for field emission equipment rated
				  for pulsed operation, the maximum-rated peak tube potential and the
				  maximum-rated number of X-ray pulses in an hour for operation at the
				  maximum-rated peak tube potential; and
c. For all other diagnostic source
				  assemblies, the maximum-rated peak tube potential and the maximum-rated
				  continuous tube current for the maximum-rated peak tube potential.
72. "Light field" means that area
				  of the intersection of the light beam from the beam-limiting device and one (1)
				  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 illumination is one fourth
				  (1/4) of the maximum in the intersection.
73. "Line-voltage regulation" means the
				  difference between the no-load and the load line potentials expressed as a
				  percent of the load line potential; that is, Percent line-voltage regulation =
				  100 (Vn-Vl)/Vl, where: Vn = Noload line potential; and Vl = Load line
				  potential.
74. "mA" means
				  milliampere.
75. "mAs" means
				  milliampere second.
76. "Mode of
				  operation" means, 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. Examples of 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.
77.
				  "Multiple tomogram system" means a computed tomography X-ray system which
				  obtains X-ray transmission data simultaneously during a single scan to produce
				  more than one tomogram.
78. "Noise"
				  means 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 µx = Linear attenuation coefficient of the
					 material of interest, µw = Linear attenuation coefficient of water, and s
					 = Estimated standard deviation of the CTN of picture elements in a specified
					 area of the CT image.
79.
				  "Nominal tomographic section thickness" means the full width at halfmaximum of
				  the sensitivity profile taken at the center of the crosssectional volume over
				  which X-ray transmission data are collected.
80. "Notification value" means a
				  protocol-specific dose index (e.g., CTDIvol(mGy) or of DLP(mGy-cm)) that is set
				  by the registrant to trigger a notification to the CT operator prior to
				  scanning when the dose index exceeds the established range for the
				  examination.
81. "Patient" means an
				  individual or animal subjected to healing arts examination, diagnosis or
				  treatment.
82. "Picture element"
				  means an elemental area of a tomogram.
83. "PBL" (See "Positive beam
				  limitation").
84. "Peak tube
				  potential" means the maximum value of the potential difference across the X-ray
				  tube during an exposure.
85.
				  "Personal supervision" means a qualified practitioner must exercise General
				  Supervision and be present in the room or adjacent control area during the
				  performance of the procedure.
86.
				  "Phantom" means 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.
87. "Photostimulable
				  storage phosphor" or "PSP" means a material used to capture and store
				  radiographic images in computed radiography systems.
88. "Pitch" means the table incrementation,
				  in CT, per X-ray tube rotation, divided by the nominal X-ray beam width at
				  isocenter.
89. "Position indicating
				  device" or "PID" means 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.
90. "Positive beam limitation" means the
				  automatic or semi-automatic adjustment of an X-ray beam to the size of the
				  selected image receptor, whereby exposures cannot be made without such
				  adjustment.
91. "Primary protective
				  barrier" means the material, excluding filters, placed in the useful beam to
				  reduce the radiation exposure (beyond the patient and cassette holder) for
				  protection purposes.
92.
				  "Protective garment" means a garment made of radiation absorbing materials used
				  to reduce radiation exposure.
93.
				  "Protocol" means a collection of settings and parameters that fully describe an
				  examination.
94. "Pulsed mode"
				  means 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 (1/2) second.
95.
				  "Quality assurance" means 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.
96. "Qualified medical physicist" or "QMP"
				  (for activities authorized pursuant to this Part) means an individual
				  registered to provide Radiation Physics Services (Diagnostic X-ray Physics
				  Services) in accordance with §
											3.6   of this
				  Subchapter.
97. "Radiation
				  detector" means a device which in the presence of radiation provides a signal
				  or other indication suitable for use in measuring one (1) or more quantities of
				  incident radiation.
98. "Radiation
				  medical event" means an event that meets the criteria in §4.4.14(A)
				  of this Part.
99. "Radiation
				  protocol committee" or "RPC" means 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.
100. "Radiation therapy
				  simulation system" means 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.
101. "Radiograph" means an image receptor on
				  which the image is created directly or indirectly by an X-ray pattern and
				  results in a permanent record.
102.
				  "Radiography" means 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.
103. "Recording" means
				  producing a retrievable form of an image resulting from X-ray
				  photons.
104. "Reference plane"
				  means a plane which is parallel to and which can be offset (as specified in
				  manufacturer information provided to users) from the location of the
				  tomographic plane(s).
105.
				  "Registrant" means any person who is registered with the Agency and is legally
				  obligated to register with the Agency pursuant to this Subchapter and the
				  Act.
106. "Registration" means
				  registration with the Agency pursuant to this Subchapter and the Act.
107. "Scan" means the complete
				  process of collecting X-ray transmission data for the production of a tomogram.
				  Data may be collected simultaneously during a single scan for the production of
				  one (1) or more tomograms.
108.
				  "Scan increment" means 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.
109. "Scan sequence" means a pre-selected set
				  of two (2) or more scans performed consecutively under pre-selected CT
				  conditions of operation.
110. "Scan
				  time" means the time elapsed during the accumulation of X-ray transmission data
				  for a single scan.
111. "Scattered
				  radiation" means radiation that, during passage through matter, has been
				  deviated in direction (See "Direct scattered radiation").
112. "Sensitivity profile" means the relative
				  response of the CT X-ray system as a function of position along a line
				  perpendicular to the tomographic plane.
113. "Single tomogram system" means a CT
				  X-ray system which obtains X-ray transmission data during a scan to produce a
				  single tomogram.
114. "Shutter"
				  means a device attached to the tube housing assembly which can intercept the
				  entire cross-sectional area of the useful beam and which has a lead equivalency
				  not less than that of the tube housing assembly.
115. "Size-specific dose estimate" or "SSDE"
				  means 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.
116. "Source" means
				  the focal spot of the X-ray tube.
117. "Source-image receptor distance" or
				  "SID" means the distance from the source to the center of the input surface of
				  the image receptor.
118.
				  "Source-skin distance" or "SSD" means the distance from the source to the
				  center of the entrant X-ray field in the plane tangent to the patient skin
				  surface.
119. "Spot-film" means a
				  radiograph which is made during a fluoroscopic examination to permanently
				  record conditions which exist during that fluoroscopic procedure. Digital image
				  receptors used in place of film with spot-film devices should be considered
				  "spot-film."
120. "Spot-film
				  device" means a device intended to transport and/or position a radiographic
				  image receptor between the X-ray source and fluoroscopic image receptor. It
				  includes a device intended to hold a cassette over the input end of the
				  fluoroscopic image receptor for the purpose of producing a
				  radiograph.
121. "Stray radiation"
				  means the sum of leakage and scattered radiation.
122. "Substantial radiation dose level" or
				  "SRDL" means an appropriately-selected dose used to trigger additional
				  dose-management actions during a procedure and medical follow-up for a
				  radiation level that might produce a clinically-relevant injury in an average
				  patient.
123. "Technique factors"
				  means the following conditions of operation:
a. For capacitor energy storage equipment,
				  peak tube potential in kilovolts (kV) and quantity of charge in
				  milliampere-seconds (mAs);
b. For
				  field emission equipment rated for pulsed operation, peak tube potential in kV,
				  and number of X-ray pulses;
c. For
				  CT X-ray systems designed for pulsed operation, peak tube potential in kV, scan
				  time in seconds, and either tube current in mA, X-ray pulse width in seconds,
				  and the number of X-ray pulses per scan, or the product of tube current, X-ray
				  pulse width, and the number of X-ray pulses in mAs;
d. For CT X-ray systems not designed for
				  pulsed operation, peak tube potential in kV, and either tube current in mA and
				  scan time in seconds, or the product of tube current and exposure time in mAs
				  and the scan time when the scan time and exposure time are equivalent;
				  and
e. For all other equipment, peak
				  tube potential in kV, and either tube current in mA and exposure time in
				  seconds, or the product of tube current and exposure time in mAs.
124. "Tomogram" means the
				  depiction of the X-ray attenuation properties of a section through the
				  body.
125. "Tomographic plane"
				  means that geometric plane which the manufacturer identified as corresponding
				  to the output tomogram.
126.
				  "Tomographic section" means the volume of an object whose X-ray attenuation
				  properties are imaged in a tomogram.
127. "Tube" means an X-ray tube, unless
				  otherwise specified.
128. "Tube
				  housing assembly" means 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.
129. "Unintended" (radiation dose in
				  diagnostic or interventional X-ray) means a patient radiation dose resulting
				  from a human error or equipment malfunction during the procedure.
130. "Useful beam" means 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.
131. "Visible area" means that portion of the
				  input surface of the image receptor over which incident X-ray photons are
				  producing a visible image.
132.
				  "Volume computed tomography dose index" or "CTDIvol"
				  means a radiation dose parameter derived from the CTDIw
				  (weighted or average CTDI given across the field of view). The formula 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). Thus,
				  CTDIvol = CTDIw/pitch.
133. "Weighted computed tomography dose
				  index" or "CTDIwa" means the estimated average CTDI100 across the field of view
				  (FOV). The equation is: CTDIw = 1/3
				  CTDI100,center + 2/3 CTDI100,edge
				  Where one third (1/3) and two thirds (2/3) approximate the relative areas
				  represented by the center and edge values derived using the sixteen (16) or
				  thirty-two (32) centimeters acrylic phantom. CTDIw uses
				  CTDI100 and an f-factor for air (0.87 rad/R or 1.0
				  mGy/mGy).
134. "X-ray control"
				  means a device which 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.
135. "X-ray exposure control" means 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.
136. "X-ray equipment" means an X-ray system,
				  subsystem, or component thereof. Types of X-ray equipment are as follows:
a. "Mobile X-ray equipment" means X-ray
				  equipment mounted on a permanent base with wheels and/or casters for moving
				  while completely assembled;
b.
				  "Portable X-ray equipment" means X-ray equipment designed to be hand-carried;
				  and
c. "Stationary X-ray equipment"
				  means X-ray equipment which is installed in a fixed location.
d. "Hand-held X-ray equipment" means X-ray
				  equipment that is designed to be hand-held during
				  operation.
137. "X-ray
				  field" means that area of the intersection of the useful beam and any one of a
				  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 (1/4) of the
				  maximum in the intersection.
138.
				  "X-ray high-voltage generator" means a device which 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.
139. "X-ray system" means
				  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 which function with the system are considered
				  integral parts of the system.
140.
				  "X-ray table" means 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.
141. "X-ray tube" means any electron tube
				  which is designed for the conversion of electrical energy into X-ray
				  energy.