5.0 Diagnostic X-ray EquipmentThe following rules are to ensure the safe use of human-use and veterinary-use diagnostic X-ray equipment at Virginia Tech. These rules are in conformity with the radiation safety standards recommended by the Commonwealth of Virginia. Show
Back To Top 5.1 Personnel MonitoringAll individuals working with diagnostic X-ray equipment shall wear a whole-body personnel monitoring device. Operators of fluoroscopic units shall wear a ring badge and a whole-body badge. When a lead apron or thyroid shield is worn, the whole-body monitoring device shall be worn at the collar outside the apron or shield. Declared pregnant radiation workers shall wear a second whole-body monitoring device under the lead apron at waist level. Back To Top 5.2 Patient ProtectionThe following rules are to protect patients from exposure to ionizing radiation, except that which is intended for diagnostic purposes.
Back To Top 5.3 Personnel ProtectionThe following rules are to protect operators, holders, and other people from exposure to ionizing radiation. 5.3.1 Stationary Units
5.3.2 Portable and Mobile Units
5.3.3 HoldersWhen a patient, animal, or film cassette must be provided with auxiliary support during an X-ray exposure:
Back To Top 5.5 Equipment RequirementsThe control panel shall contain the following legible and accessible warning statements:
The total filtration permanently mounted in the useful beam shall not be less than:
The tube housing assembly support shall ensure that the tube housing remains stable during the X-ray exposure. The technique factors to be used during an exposure shall be visible before the exposure begins. On battery-powered equipment, visual means shall be provided on the control panel to show the charge of the battery. A source-to-image distance (SID) indicator must be provided and be accurate to within 2% of the indicated SID. 5.5.1 Stationary, Portable, and Mobile UnitsA means for stepless adjustment (e.g. variable aperture collimator) of the size of the X-ray field shall be provided. Means shall be provided to visually define the perimeter of the X-ray field. The X-ray field shall not exceed the visually defined field by greater than 2%. A method shall be provided to show when the axis of the X-ray beam is perpendicular to the plane of the image receptor. The exposure shall be ended at a preset time interval, product of current and time, number of pulses, or radiation exposure to the image receptor. The X-ray control shall provide a visual indication of X-ray production and an audible signal when the exposure is finished. The X-ray control for stationary systems shall be permanently mounted in a protected area. 5.5.2 Fluoroscopic SystemsX-ray production shall be controlled by a dead-man switch. The on-time of the fluoroscopic tube shall be controlled by a timing device, which ends the exposure after 5 minutes. An audible signal shall signal the completion of the preset on-time. This signal will remain on until the timing device is reset. Protective barriers of at least 0.25 mm lead equivalency shall be used to attenuate scatter radiation from above the table top (e.g. drapes, bucky-slot covers). This shielding is in addition to the lead apron worn by personnel. Scattered radiation from under the table shall be attenuated by at least 0.25 mm lead equivalency. The fluoroscopic imaging assembly shall be provided with a primary protective barrier, which intercepts the entire cross section of the useful beam. The X-ray tube used for fluoroscopy shall not produce X-rays unless the barrier is in position to intercept the entire useful beam. Back To Top 5.6 Operator's BoothThe operator's booth shall have at least 7.5 square feet of unobstructed floor space in the booth. The booth may be of any shape with no dimension less than 2 feet. The booth is to be located or constructed so that the direct beam and unattenuated direct scatter radiation cannot reach the operator. 5.6.1 Structural RequirementsThe booth walls shall be at least 78 inches high and permanently fixed. A door or panel that is permanently part of the booth must be interlocked. Sufficient shielding shall be provided to prevent occupational limits from being exceeded. 5.6.2 Control PlacementThe X-ray control shall be fixed within the booth at least 40 inches from the edge of the booth wall closest to the examining table. The placement of the control shall allow the operator to use most of the viewing window. 5.6.3 Viewing requirementsThe booth must have a window that will allow the operator to view any occupant in the room and any entry into the room. Access doors that cannot be viewed by the operator must be interlocked. The window shall have an area of at least 1 square foot with the lower edge at least 4.5 feet from the floor. The edge of the window shall be at least 18 inches from the edge of the booth. The glass shall have the same lead equivalency as the walls of the booth. Back To Top 5.7 RecordsThe Laboratory Authority shall maintain the following records and information:
Back To Top 5.8 Surveys and InspectionsRadiation safety and equipment performance surveys shall be performed by a Qualified Expert annually on human-use units and at least every 3 years on bone densitometers or veterinary-use units. A survey for leakage radiation shall be performed following any maintenance, modification or relocation of the system. Radiation surveys of areas adjacent to the X-ray producing facility and in the booth will be performed after installation of new equipment or the relocation of a unit.
Reports of all surveys and inspections will be maintained in the Radiation Safety Office. Back To Top How thick should lead shielding be?The radiation protection provided by a lead apron is approximately the same as 0.25- to 1-mm thick lead. An apron with 0.5-mm thickness can attenuate approximately 90% or more of the scatter radiation. Lead glasses with 0.5- or 0.75-mm thickness can reduce more than 95% of scatter radiation [32].
What is the minimum lead thickness?It is common for states to require a minimum of 0.25 mm of lead, while others require 0.5 mm.
What is the thickness of a thyroid shield that should be worn during fluoroscopy?Studies have recommended that surgeons and others in the radiation field wear 0.5 mm lead-equivalent aprons during fluoroscopy. Since thyroid is very sensitive to ionizing radiation, thyroid shields should be worn anytime fluoroscopy is used.
What is the minimum thickness of the protective curtain when using fluoroscopic equipment?- A lead vinyl protective curtain with no less than 0.25 mm of lead equivalent must be placed between the patient and the person performing and fluoroscopic procedure (tech or radiologist).
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