Fluoroscopic X-Ray Systems

Fluoroscopic X-Ray Systems. All fluoroscopic x-ray systems shall be image intensified and meet the following requirements: 1. Limitation of Useful Beam. a. Primary Barrier. i. The fluoroscopic imaging assembly used shall be provided with a primary protective barrier which intercepts the entire cross section of the useful beam at any SID. ii. The x-ray tube used for fluoroscopy shall not produce x-rays unless the barrier is in position to intercept the entire useful beam. b. Fluoroscopic Beam Limitation. i. For certified fluoroscopic systems, neither the length nor the width of the x-ray field in the plane of the image receptor shall exceed that of the visible area of the image receptor by more than 3 percent of the SID. The sum of the excess length and the excess width shall be no greater than 4 percent of the SID. ii. For uncertified fluoroscopic systems with a spot film device, the x-ray beam with the shutters fully opened (during fluoroscopy or spot filming) shall be no larger than the largest spot film size for which the device is designed. Measurements shall be made at the minimum SID available but at no less than 20 centimeters table top to the film plane distance. iii. For uncertified fluoroscopic systems without a spot film device, the requirements of 1.6.5(1)(b)(i) apply. iv. Other requirements for fluoroscopic beam limitation: i. Means shall be provided to permit further limitation of the field. Beam-limiting devices manufactured after May 22, 1979, and incorporated in equipment with a variable SID and/or a visible area of greater than 300 square centimeters shall be provided with means for stepless adjustments of the x-ray field. ii. All equipment with a fixed SID and a visible area of 300 square centimeters or less shall be provided with either stepless adjustment of the x-ray field or with means to further limit the x-ray field size at the plane of the image receptor to 125 square centimeters or less. iii. If provided, stepless adjustment shall provide continuous field sizes from the maximum obtainable to a field size of 5 centimeters by 5 centimeters or less. iv. For equipment manufactured after February 25, 1978, when the angle between the image receptor and beam axis is variable, means shall be provided to indicate when the axis of the x-ray beam is perpendicular to the plane of the image receptor; compliance shall be determined with the beam axis indicated to be perpendicular to the plane of the image receptor. v. For rectangular x-ray fields used with circular image reception, the error in alignment shall be determined along the length and width dimensions of the x-ray field which pass through the center of the visible area of the image receptor. c. Spot Film Beam Limitation. Spot-film devices which are certified components shall meet the following additional requirements: i. Means shall be provided between the source and the patient for adjustment of the x-ray field size in the plane of the film to the size of that portion of the film which has been selected on the spot film selector. Such adjustment shall be automatically accomplished except when the x-ray field size in the plane of the film is smaller than that of the selected portion of the film. For spot film devices manufactured after June 21, 1979, if the x-ray field size is less than the size of the selected portion of the film, the means for adjustment of the field size shall be only at the operator's option. d. It shall be possible to adjust the x-ray field size in the plane of the film to a size smaller than the selected portion of the film. The minimum field size at the greatest SID shall be equal to, or less than, 5 centimeters by 5 centimeters. e. The center of the x-ray field in the plane of the film shall be aligned with the center of the selected portion of the film to within 2 percent of the SID. f. On spot-film devices manufactured after February 25, 1978, if the angle between the plane of the image receptor and beam axis is variable, means shall be provided to indicate when the axis of the x-ray beam is perpendicular to the plane of the image receptor, and compliance shall be determined with the beam axis indicated to be perpendicular to the plane of the image receptor. g. Override. If a means exists to override any of the automatic x-ray field size adjustments required in 1.6.5(1)(b), and (c) that means: i. shall be designed for use only in the event of system failure; ii. shall incorporate a signal visible at the fluoroscopist's position which will indicate whenever the automatic field size adjustment is overridden; and iii. shall be clearly and durably labeled as follows: FOR X-RAY FIELD LIMITATION SYSTEM FAILURE 2. Activation of the Fluoroscopic Tube. X-ray production in the fluoroscopic mode shall be controlled by a device which requires continuous pressure by the fluoroscopist for the entire time of any exposure. When recording serial fluoroscopic images, the fluoroscopist shall be able to terminate the x-ray exposure(s) at any time, but means may be provided to permit completion of any single exposure of the series in process. 3. Exposure Rate Limits. a. Entrance Exposure Rate Allowable Limits. i. Fluoroscopic equipment which is provided with automatic exposure rate control shall not be operable at any combination of tube potential and current which will result in an exposure rate in excess of 10 roentgens (2.58 mC/kg) per minute at the point where the center of the useful beam enters the patient, except: i. During recording of fluoroscopic images, or ii. When an optional high level control is provided. When so provided, the equipment shall not be operable at any combination of tube potential and current which will result in an exposure rate in excess of 5 roentgens (1.29 mC/kg) per minute at the point where the center of the useful beam enters the patient unless the high level control is activated. Special means of activation of high level controls shall be required. The high level control shall only be operable when continuous manual activation is provided by the operator. A continuous signal audible to the fluoroscopist shall indicate that the high level control is being employed. ii. Fluoroscopic equipment which is not provided with automatic exposure rate control shall not be operable at any combination of tube potential and current which will result in an exposure rate in excess of 5 roentgens (1.29 mC/kg) per minute at the point where the center of the useful beam enters the patient, except: i. During recording of fluoroscopic images, or ii. When an optional high level control is activated. Special means of activation of high level controls shall be required. The high level control shall only be operable when continuous manual activation is provided by the operator. A continuous signal audible to the fluoroscopist shall indicate that the high level control is being employed. iii. Compliance with the requirements of 1.6.5(3) shall be determined as follows: i. If the source is below the x-ray table, the exposure rate shall be measured 1 centimeter above the tabletop or cradle. ii. If the source is above the x-ray table, the exposure rate shall be measured at 30 centimeters above the tabletop with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement. iii. For a C-arm type of fluoroscope, the exposure rate shall be measured 30 centimeters from the input surface of the fluoroscopic imaging assembly, with the source positioned at any available SID, provided that the end of the beam-limiting device or spacer is no closer than 30 centimeters from the input surface of the fluoroscopic imaging assembly. iv. For a lateral type fluoroscope, the exposure rate shall be measured at a point 15 centimeters from the center line of the x-ray table and in the direction of the x-ray source with the end of the beam-limiting device or spacer positioned as closely as possible to the point of measurement. If the tabletop is movable, it shall be positioned as closely as possible to the lateral x-ray source, with the end of the beam limiting device or spacer no closer than 15 centimeters to the center line of the x-ray table. b. Periodic measurement of entrance exposure rate shall be performed by a qualified expert for both maximum and typical values, as follows.4 i. Such measurements shall be made annually or after any maintenance of the system which might affect the exposure rate. ii. Results of these measurements shall be posted where any fluoroscopist may have ready access to such results while using the fluoroscope and in the record required in 1.6.3(1)(l)(iii) The measurement results shall be stated in roentgens per minute and include the technique factors used in determining such results. The name of the person performing the measurements and the date the measurements were performed shall be included in the results. 4 Materials should be placed in the useful beam to protect the imaging system when conducting these periodic measurements. iii. Conditions of periodic measurement of maximum entrance exposure rate are as follows: i. the measurement shall be made under the conditions that satisfy the requirements of 1.6.5(3)(a)(iii); ii. the kVp, mA, and/or other selectable parameters shall be adjusted to those settings which give the maximum entrance exposure rate; and iii. the x-ray system that incorporates automatic exposure rate control shall have sufficient attenuative material placed in the useful beam to produce the maximum output of that system. iv. Conditions of periodic measurement of typical entrance exposure rate are as follows: i. the measurement shall be made under the conditions that satisfy the requirements of 1.6.5(3)(a)(iii); ii. the kVp and mA shall be typical of clinical use of the x-ray system; and iii. the x-ray system(s) that incorporates automatic exposure rate control shall have an appropriate phantom placed in the useful beam to produce a milliamperage and/or kilovoltage typical of the use of the x-ray system. 4. Barrier Transmitted Radiation Rate Limits. a. The exposure rate due to transmission through the primary protective barrier with the attenuation block in the useful beam, combined with radiation from the image intensifier shall not exceed 2 milliroentgens (0.516 µC/kg) per hour at 10 centimeters from any accessible surface of the fluoroscopic imaging assembly beyond the plane of the image receptor for each roentgen per minute of entrance exposure rate. b. Measuring Compliance of Barrier Transmission. i. The exposure rate due to transmission through the primary protective barrier combined with radiation from the image intensifier shall be determined by measurements averaged over an area of 100 square centimeters with no linear dimension greater than 20 centimeters. ii. If the source is below the tabletop, the measurement shall be made with the input surface of the fluoroscopic imaging assembly positioned 30 centimeters above the tabletop. iii. If the source is above the tabletop and the SID is variable, the measurement shall be made with the end of the beam-limiting device or spacer as close to the tabletop as it can be placed, provided that it shall not be closer than 30 centimeters. iv. Compression devices and movable grids shall be removed from the useful beam during the measurement. 5. Indication of Potential and Current. During fluoroscopy and cinefluorography, the kV and the mA shall be continuously indicated. 6. Source-to-Skin Distance. The SSD shall not be less than: a. 38 centimeters on stationary fluoroscopic systems manufactured on or after August 1, 1974; b. 35.5 centimeters on stationary fluoroscopic systems manufactured prior to August 1, 1974; c. 30 centimeters on all mobile fluoroscopes; and d. 20 centimeters for all mobile fluoroscopes used for specific surgical procedures. 7. Fluoroscopic Timer. a. Means shall be provided to preset the cumulative on-time of the fluoroscopic x-ray tube. The maximum cumulative time of the timing device shall not exceed 5 minutes without resetting. b. A signal audible to the fluoroscopist shall indicate the completion of any preset cumulative on-time. Such signal shall continue to sound while x-rays are produced until the timing device is reset. 8. Control of Scattered Radiation. a. Fluoroscopic table designs when combined with procedures utilized shall be such that no unprotected part of any staff or ancillary individual's body shall be exposed to unattenuated scattered radiation which originates from under the table. The attenuation required shall be not less than 0.25 millimeter lead equivalent. b. Equipment configuration when combined with procedures shall be such that no portion of any staff or ancillary individual's body, except the extremities, shall be exposed to the unattenuated scattered radiation emanating from above the table top unless that individual: i. is at least 120 centimeters from the center of the useful beam; or ii. the radiation has passed through not less than 0.25 millimeter lead equivalent material including, but not limited to, drapes, Bucky-slot cover panel, or self-supporting curtains, in addition to any lead equivalency provided by the protective apron referred to in 1.6.3(1)(h)(vii). c. The Agency may grant exemptions to 1.6.5(8)(b) where a sterile field will not permit the use of the normal protective barriers. Where the use of prefitted sterilized covers for the barriers is practical, the Agency shall not permit such exemption. See Appendix C for a suggested list of fluoroscopic procedures where such exemptions will be automatically granted. 9. Spot Film Exposure Reproducibility. Fluoroscopic systems equipped with spot film (radiographic) mode shall meet the exposure reproducibility requirements of 1.6.6(4) when operating in the spot film mode. 10. Radiation Therapy Simulation Systems. Radiation therapy simulation systems shall be exempt from all the requirements of 1.6.5(1), 1.6.5(3), 1.6.5(4), and 1.6.5(7) provided that: a. such systems are designed and used in such a manner that no individual other than the patient is in the x-ray room during periods of time when the system is producing x-rays; and b. systems which do not meet the requirements of 1.6.5(7) are provided with a means of indicating the cumulative time that an individual patient has been exposed to x-rays. Procedures shall require in such cases that the timer be reset between examinations.