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(18) Tomographic plane means that scanning mechanism or other readily eometric plane which the manufac- identifiable feature of the CT X-ray urer identifies as corresponding to the system in such a manner as to permit utput tomogram.
placement of the dosimetry phantom in (19) Tomographic section means the this orientation. rolume of an object whose x-ray at (ii) The CTDI in the center location enuation properties are imaged in a of the dosimetry phantom for each seomogram.
lectable CT condition of operation that (c) Information to be provided for users. varies either the rate or duration of xDach manufacturer of a CT x-ray sys- ray exposure. This CTDI shall be preem shall provide the following tech- sented as a value that is normalized to lical and safety information, in addi- the CTDI in the center location of the ion to that required under $1020.30(h), dosimetry phantom from paragraph io purchasers and, upon request, to (c)(2)(i) of this section, with the CTDI Others at a cost not to exceed the cost of paragraph (c)(2)(i) of this section of publication and distribution of such having a value of one. As each indinformation. This information shall be vidual CT condition of operation is dentified and provided in a separate changed, all other independent CT conjection of the user's instruction man- ditions of operation shall be mainial or in a separate manual devoted tained at the typical values described only to this information.
in paragraph (c)(2)(i) of this section. (1) Conditions of operation. A state- These data shall encompass the range ment of the CT conditions of operation of each CT condition of operation statused to provide the information re ed by the manufacturer as appropriate quired by paragraph (c) (2) and (3) of for CT of the head or body. When more this section.
than three selections of a CT condition (2) Dose information. The following of operation are available, the normallose information obtained by using the ized CTDI shall be provided, at least, CT dosimetry phantom. For any CT X- for the minimum, maximum, and midray system designed to image both the range value of the CT condition of ophead and body, separate dose informa- eration. tion shall be provided for each applica (iii) The CTDI at the location coincition. All dose measurements shall be dent with the maximum CTDI at 1 cenperformed with the CT dosimetry phan timeter interior to the surface of the tom placed on the patient couch or dosimetry phantom for each selectable support device without additional at peak tube potential. When more than tenuating materials present.
three selections of peak tube potential (i) The CTDI at the following loca are available, the normalized CTDI tions in the dosimetry phantom:
shall be provided, at least, for the min(a) Along the axis of rotation of the imum, maximum, and a typical value phantom.
of peak tube potential. The CTDI shall (6) Along a line parallel to the axis of be presented as a value that is normalrotation and 1.0 centimeter interior to ized to the maximum CTDI located at 1 the surface of the phantom with the centimeter interior to the surface of phantom positioned so that CTDI is the the dosimetry phantom from paragraph maximum obtainable at this depth.
(c)(2)(i) of this section, with the CTDI (C) Along lines parallel to the axis of of paragraph (c)(2)(i) of this section rotation and 1.0 centimeter interior to having a value of one. the surface of the phantom at positions (iv) The dose profile in the center lo90, 180, and 270 degrees from the posi- cation of the dosimetry phantom for tion in paragraph (c)(2)(i)(b) of this sec- each selectable nominal tomographic tion. The CT conditions of operation section thickness. When more than shall be the typical values suggested by three selections of nominal tomothe manufacturer for CT of the head or graphic section thicknesses are availbody. The location of the position able, the information shall be provided, where the CTDI is maximum as speci at least, for the minimum, maximum, fied in paragraph (c)(2)(i)(b) of this sec- and midrange value of nominal tomotion shall be given by the manufac- graphic section thickness. The dose turer with respect to the housing of the profile shall be presented on the same graph and to the same scale as the cor- nominal tomographic section thickresponding sensitivity profile required ness, the spatial resolution capability by paragraph (c)(3)(iv) of this section. of the system for low and high contrast
(v) A statement of the maximum de- objects, and measuring the mean CT viation from the values given in the in- number of water or a reference mateformation provided according to para rial. graph (c)(2) (i), (ii), (iii), and (iv) of this
(2) Instructions on the use of the section. Deviation of actual values may phantom(s) including a schedule of not exceed these limits.
testing appropriate for the system, al(3) Imaging performance information.
lowable variations for the indicated paThe following performance data shall
rameters, and a method to store as be provided for the CT conditions of op records, quality assurance data eration used to provide the information
(3) Representative images obtained required by paragraph (c)(2)(i) of this
with the phantom(s) using the same section. All other aspects of data col
processing mode and CT conditions of lection, including the x-ray attenu
operation as in paragraph (c)(3) of this ation properties of the material in the
section for a properly functioning sys tomographic section, shall be similar
tem of the same model. The represettto those used to provide the dose infor
ative images shall be of two forms as mation required by paragraph (c)(2)(i)
follows: of this section. For any CT x-ray sys
(i) Photographic copies of the images tem designed to image both the head
obtained from the image display deand body, separate imaging perform
vice. ance information shall be provided for
(ii) Images stored in digital form on a each application. (i) A statement of the noise.
storage medium compatible with the (ii) A graphical presentation of the
CT x-ray system. The CT X-ray system modulation transfer function for the
shall be provided with the means to same image processing and display
display these images on the image dismode as that used in the statement of
play demi the noise.
(e) [Reserved] (iii) A statement of the nominal (f) Control and indication of conditiofs tomographic section thickness(es). of operation–(1) Visual indication. The
(iv) A graphical presentation of the CT conditions of operation to be used sensitivity profile, at the location cor during a scan or a scan sequence shall responding to the center location of be indicated prior to initiation of a the dosimetry phantom, for each se- scan or a scan sequence. On equipment lectable nominal tomographic section having all or some of these conditions thickness for which the dose profile is of operation at fixed values, this regiven according to paragraph (c)(2)(iv) quirement may be met by permanent of this section.
markings. Indication of the CT condi(v) A description of the phantom or tions of operation shall be visible from device and test protocol or procedure any position from which scan initiused to determine the specifications ation is possible. and a statement of the maximum devi (2) Timers. (i) Means shall be provided ation from the specifications provided to terminate the x-ray exposure autoin accordance with paragraphs (c)(3) matically by either deenergizing the s(i), (ii), (iii), and (iv) of this section ray source or shuttering the X-ray Deviation of actual values may not ex- beam in the event of equipment failure ceed these limits.
affecting data collection. Such termi(d) Quality assurance. The manufac nation shall occur within an interval turer of any CT X-ray system shall pro- that limits the total scan time to no vide the following with each system. more than 110 percent of its preset All information required by this sub value through the use of either a section shall be provided in a separate backup timer or devices which monitor section of the user's instructional man equipment function. A visible signal ual.
shall indicate when the x-ray exposure (1) A phantom(s) capable of providing has been terminated through these an indication of contrast scale, noise, means and manual resetting of the CT
conditions of operation shall be required prior to the initiation of another scan.
(ii) Means shall be provided so that che operator can terminate the x-ray exposure at any time during a scan, or series of scans under x-ray system control, of greater than one-half second duration. Termination of the x-ray exposure shall necessitate resetting of the CT conditions of operation prior to the initiation of another scan.
(g) Tomographic plane indication and alignment. (1) For any single tomogram system, means shall be provided to permit visual determination of the tomographic plane or a reference plane offset from the tomographic plane.
(2) For any multiple tomogram system, means shall be provided to permit visual determination of the location of a reference plane. The relationship of the reference plane to the planes of the tomograms shall be provided to the user in addition to other information provided according to $ 1020.30(h). This reference plane can be offset from the location of the tomographic planes.
(3) The distance between the indicated location of the tomographic plane or reference plane and its actual location may not exceed 5 millimeters.
(4) For any offset alignment system, the manufacturer shall provide specific instructions with respect to the use of this system for patient positioning, in addition to other information provided according to S 1020.30(h).
(5) If a mechanism using a light source is used to satisfy the requirements of paragraphs (g) (1) and (2) of this section, the light source shall allow visual determination of the location of the tomographic plane or reference plane under ambient light conditions of up to 500 lux.
(h) Beam-on and shutter status indicators. (1) Means shall be provided on the control and on or near the housing of the scanning mechanism to provide visual indication when and only when x rays are produced and, if applicable, whether the shutter is open or closed. If the x-ray production period is less than one-half second, the indication of X-ray production shall be actuated for one-half second. Indicators at or near the housing of the scanning mechanism shall be discernible from any point ex
ternal to the patient opening where insertion of any part of the human body into the primary beam is possible.
(2) For systems that allow high voltage to be applied to the x-ray tube continuously and that control the emission of x rays with a shutter, the radiation emitted may not exceed 100 milliroentgens (2.58x10-5 coulomb/kilogram) in 1 hour at any point 5 centimeters outside the external surface of the housing of the scanning mechanism when the shutter is closed. Compliance shall be determined by measurements averaged over an area of 100 square centimeters with no linear dimensions greater than 20 centimeters.
(i) Scan increment accuracy. The deviation of indicated scan increment from actual scan increment may not exceed 1 millimeter. Compliance shall be measured as follows: The determination of the deviation of indicated versus actual scan increment shall be based on measurements taken with a mass 100 kilograms or less, on the patient support device. The patient support device shall be incremented from a typical starting position to the maximum incrementation distance or 30 centimeters, whichever is less, and then returned to the starting position. Measurement of actual versus indicated scan increment may be taken anywhere along this travel.
(j) CT number mean and standard deviation. (1) A method shall be provided to calculate the mean and standard deviation of CT numbers for an array of picture elements about any location in the image. The number of elements in this array shall be under user control.
(2) The manufacturer shall provide specific instructions concerning the use of the method provided for calculation of CT number mean and standard deviation in addition to other information provided according to § 1020.30(h). (49 FR 34712, Aug. 31, 1984; 49 37381, Sept. 24, 1984, as amended at 49 FR 47388, Dec. 4, 1984; 56 FR 36098, Aug. 1, 1991; 67 FR 9587, Mar. 4, 2002]
EFFECTIVE DATE NOTE: At 70 FR 34042, June 10, 2005, 81020.33 was amended by revising paragraph (h)(2), effective June 10, 2006. For the convenience of the user, the revised text is set forth as follows:
$ 1020.33 Computed tomography (CT) equip
(h)* * *
(2) For systems that allow high voltage to be applied to the x-ray tube continuously and that control the emission of x-ray with a shutter, the radiation emitted may not exceed 0.88 milligray (vice 100 milliroentgen exposure) in 1 hour at any point 5 cm outside the external surface of the housing of the scanning mechanism when the shutter is closed. Compliance shall be determined by measurements average over an area of 100 square cm with no linear dimension greater than 20 cm.
$ 1020.40 Cabinet x-ray systems.
(a) Applicability. The provisions of this section are applicable to cabinet xray systems manufactured or assembled on or after April 10, 1975, except that the provisions as applied to x-ray systems designed primarily for the inspection of carry-on baggage are applicable to such systems manufactured or assembled on or after April 25, 1974. The provisions of this section are not applicable to systems which are designed exclusively for microscopic examination of material, e.g., X-ray diffraction, spectroscopic, and electron microscope equipment or to systems for intentional exposure of humans to x-rays.
(b) Definitions. As used in this section the following definitions apply:
(1) Access panel means any barrier or panel which is designed to be removed or opened for maintenance or service purposes, requires tools to open, and permits access to the interior of the cabinet.
(2) Aperture means any opening in the outside surface of the cabinet, other than a port, which remains open during generation of x radiation.
(3) Cabinet x-ray system means an xray system with the x-ray tube in stalled in an enclosure (hereinafter termed cabinet) which, independently of existing architectural structures except the floor on which it may be placed, is intended to contain at least that portion of a material being irradiated, provide radiation attenuation, and exclude personnel from its interior
during generation of x radiation. Included are all x-ray systems designed primarily for the inspection of carry-on baggage at airline, railroad, and bus terminals, and in similar facilities. An x-ray tube used within a shielded part of a building, or x-ray equipment which may temporarily or occasionally incorporate portable shielding is not considered a cabinet x-ray system.
(4) Door means any barrier which is designed to be movable or opened for routine operation purposes, does not generally require tools to open, and permits access to the interior of the cabinet. For the purposes of paragraph (C)(4)(i) of this section, inflexible hardware rigidly affixed to the door shall be considered part of the door.
(5) Exposure means the quotient of dQ by dm where do is the absolute value of the total charge of the ions of one sign produced in air when all the electrons (negatrons and positrons) liberated by photons in a volume element of air having mass dm are completely stopped in air.
(6) External surface means the outside surface of the cabinet x-ray system, including the high-voltage generator, doors, access panels, latches, control knobs, and other permanently mounted hardware and including the plane across any aperture or port.
(7) Floor means the underside external surface of the cabinet.
(8) Ground fault means an accidental electrical grounding of an electrical conductor.
(9) Port means any opening in the outside surface of the cabinet which is designed to remain open, during generation of x-rays, for the purpose of conveying material to be irradiated into and out of the cabinet, or for par tial insertion for irradiation of an object whose dimensions do not permit complete insertion into the cabinet.
(10) Primary beam means the x radiation emitted directly from the from the target and passing through the window of the x-ray tube.
(11) Safety interlock means a device which is intended to prevent the generation of x radiation when access by any part of the human body to the interior of the cabinet x-ray system through a door or access panel is possible.
(12) X-ray system means an assemlage of components for the controlled ceneration of x-rays.
(13) X-ray tube means any electron ube which is designed for the conversion of electrical energy into x-ray energy.
(c) Requirements—(1) Emission limit. (i) Radiation emitted from the cabinet xay system shall not exceed an exposure of 0.5 milliroentgen in one hour at any point five centimeters outside the
ve centimeters outside the external surface.
(ii) Compliance with the exposure limit in paragraph (c)(1)(i) of this section shall be determined by measurements averaged over a cross-sectional area of ten square centimeters with no linear dimension greater than 5 centimeters, with the cabinet x-ray system operated at those combinations of xray tube potential, current, beam orientation, and conditions of scatter radiation which produce the maximum xray exposure at the external surface, and with the door(s) and access panel(s) fully closed as well as fixed at any other position(s) which will allow the generation of x radiation.
(2) Floors. A cabinet X-ray system shall have a permanent floor. Any support surface to which a cabinet x-ray system is permanently affixed may be deemed the floor of the system.
(3) Ports and apertures. (i) The insertion of any part of the human body through any port into the primary beam shall not be possible.
(ii) The insertion of any part of the human body through any aperture shall not be possible.
(4) Safety interlocks. (i) Each door of a cabinet x-ray system shall have a minimum of two safety interlocks. One, but not both of the required interlocks shall be such that door opening results in physical disconnection of the energy supply circuit to the high-voltage generator, and such disconnection shall not be dependent upon any moving part other than the door.
(ii) Each access panel shall have at least one safety interlock.
(iii) Following interruption of x-ray generation by the functioning of any safety interlock, use of a control provided in accordance with paragraph (c)(6)(ii) of this section shall be nec
essary for resumption of x-ray generation.
(iv) Failure of any single component of the cabinet x-ray system shall not cause failure of more than one required safety interlock.
(5) Ground fault. A ground fault shall not result in the generation of x-rays.
(6) Controls and indicators for all cabinet x-ray systems. For all systems to which this section is applicable there shall be provided:
(i) A key-actuated control to insure that x-ray generation is not possible with the key removed. .
(ii) A control or controls to initiate and terminate the generation of x-rays other than by functioning of a safety interlock or the main power control.
(iii) Two independent means which indicate when and only when x-rays are being generated, unless the x-ray generation period is less than one-half second, in which case the indicators shall be activated for one-half second, and which are discernible from any point at which initiation of x-ray generation is possible. Failure of a single component of the cabinet x-ray system shall not cause failure of both indicators to perform their intended function. One, but not both, of the indicators required by this subdivision may be a milliammeter labeled to indicate x-ray tube current. All other indicators shall be legibly labeled “X-RAY ON".
(iv) Additional means other than milliammeters which indicate when and only when x-rays are being generated, unless the x-ray generation period is less than one-half second in which case the indicators shall be activated for one-half second, as needed to insure that at least one indicator is visible from each door, access panel, visible from eas and port, and is legibly labeled “XRAY ON”.
(7) Additional controls and indicators for cabinet x-ray systems designed to admit humans. For cabinet x-ray systems designed to admit humans there shall also be provided:
(i) A control within the cabinet for preventing and terminating x-ray generation, which cannot be reset, overridden or bypassed from the outside of the cabinet.