In addition to the provisions of ss. DHS 157.74
, the requirements in this section apply to x-ray equipment and associated facilities used for dental radiography. Requirements for extraoral dental radiographic systems are contained in s. DHS 157.77
(2) Source-to-skin distance.
X-ray systems designed for use with an intraoral image receptor shall be provided with means to limit source-to-skin distance to not less than either one of the following:
20 centimeters (8 inches) if operable above 50 kVp. Beam-limiting devices shall be lead lined.
10 centimeters (4 inches) if operable at 50 kVp only. Beam-limiting devices shall be lead lined.
(3) Beam limitation.
Radiographic systems designed for use with an intraoral image receptor shall be provided with means to limit the x-ray beam such that the beam at the minimum SSD shall be contained in a circle having a diameter of no more than 7 centimeters.
(4) Radiation exposure control.
Intraoral radiographic systems shall meet all of the following exposure control requirements:
Means shall be provided to initiate the radiation exposure by a deliberate action on the part of the operator, such as the depression of a switch. Radiation exposure may not be initiated without such an action. An exposure may not be made when the timer is set to a "zero" or "off" position if either position is provided.
Means shall be provided for visual exposure indication observable at or from the operator's protected position whenever x-rays are produced. In addition, a signal audible to the operator shall indicate that the exposure has terminated.
Means shall be provided to terminate the exposure at a preset time interval, preset product of current and time, a preset number of pulses or a preset radiation exposure to the image receptor. Termination of an exposure shall cause automatic resetting of the timer to its initial setting or to "zero" except for panoramic systems that may pause during the exposure cycle.
Exposure control location and operator protection.
An x-ray system shall meet all the following requirements, as applicable, to ensure operator protection during use of the system:
A stationary x-ray system shall have an x-ray exposure control that may be moved to a protected area so that the operator is required to remain in that protected area during the entire exposure. The exposure cord shall be of sufficient length to allow the operator to be at least 2 meters (6.5 feet) from the x-ray tube head and not in the direction the tube is pointed. The operator shall be able to determine when the exposure has completed either by audible tone or by visible signal.
A mobile or portable x-ray system that is used for greater than one week in the same location, which is a room or suite, shall meet the requirements of stationary dental equipment.
A mobile or portable x-ray system that is used for less than one week in the same location shall be provided with either a protective barrier at least 2 meters (6.5 feet) high for operator protection or means to allow the operator to be at least 2 meters (6.5 feet) from the tube housing assembly while making exposures.
When the equipment is operated on an adequate power supply as specified by the manufacturer, the estimated coefficient of variation of air kerma may be no greater than 0.05 for any specific combination of selected technique factors.
(6) mA/mAs linearity.
X-ray equipment that is operated on a power supply as specified by the manufacturer for any fixed x-ray tube potential within the range of 40% to 100% of the maximum rated shall meet all of the following requirements:
Equipment having independent selection of x-ray tube current.
The average ratios of air kerma to the indicated milliampere-seconds product, in units of .001 mGy/mAs (mR/mAs), obtained at any 2 consecutive tube current settings may not differ by more than 0.10 times their sum:
X1 - X2 < 0.10 (X1+X2)
where X1 and X2 are the average values obtained at each of 2 consecutive tube current settings, or at 2 settings differing by no more than a factor of 2 where the tube current selection is continuous.
Equipment having a combined x-ray tube current-exposure time product selector but not a separate tube current selector.
The average ratios of air kerma to the indicated milliampere-seconds product, in units of .001 mGy/mAs (mR/mAs), obtained at any 2 consecutive mAs selector settings may not differ by more than 0.10 times their sum:
X1 - X2 < 0.10 (X1 +X2)
where X1 and X2 are the average values obtained at any 2 consecutive mAs selector settings, or at 2 settings differing by no more than a factor of 2 where the mAs selector provides continuous selection.
Determination of compliance shall be based on 10 exposures taken within a time period of one hour at each of the 2 settings. The 2 settings may include any 2 focal spot sizes except where one is equal to or less than 0.45 millimeters and the other is greater than 0.45 millimeters. For purposes of this requirement, focal spot size is the nominal focal spot size specified by an x-ray tube manufacturer.
Deviation of technique factors from indicated values for kVp and exposure time, if time is independently selectable, may not exceed the limits specified for that system by its manufacturer. In the absence of manufacturer's specifications the deviation may not exceed 10% of the indicated value for kVp and 10% for time.
(8) Kvp limitations.
Dental x-ray machines with a nominal fixed kVp of less than 50 kVp may not be used to make diagnostic dental radiographs of humans.
The tube housing and the cone may not be hand-held during an exposure.
The tube shall be stationary during exposure, except for panoramic systems. Any oscillation of the tube head shall cease before exposure is made.
DHS 157.78 History
History: CR 01-108
: cr. Register July 2002 No. 559
, eff. 8-1-02.
Veterinary medicine x-ray systems. DHS 157.79(1)(1)
The requirements of this section apply to all animal use x-ray systems used in veterinary practice and are in addition to other provisions in subchs. I
The tube housing shall be electrically shock proof and of a diagnostic type. The x-ray tube may not be hand-held during exposures.
A device shall be provided to terminate the exposure after a preset time or exposure.
A dead-man type of exposure switch shall be provided with an electrical cord of sufficient length so that the operator or the assistant, may stand out of the useful beam and at least 2 meters (6.5 feet) from the table during all x-ray exposures. A foot operated exposure switch may be used and this switch may be integrated into the table base or the foot switch may be on a 2 meter (6.5 feet) cord.
The operator shall stand at least 2 meters (6.5 feet) from the tube housing and the animal during radiographic exposures. The operator may not stand in the useful beam. Hand-held fluoroscopic screens may not be used. The tube housing may not be held by the operator. No person other than the operator may be in an x-ray room while exposures are being made unless another person's assistance is required.
During any application in which the operator is not located behind a protective barrier, the operator and any other persons in the room during exposures shall wear protective clothing consisting of a protective apron having a lead equivalent of not less than 0.5 millimeter unless measurements indicate otherwise.
Any person holding or supporting an animal or the film during radiation exposure shall wear protective gloves that surround the hand and a protective apron having a lead equivalent of not less than 0.5 millimeter. Devices that only partially shield the hands are prohibited.
Veterinary fluoroscopy systems shall be operated only under the direct supervision of the licensed veterinarian.
(4) Animal support.
Mechanical restraints shall be used to restrict movement of the animal unless the restraints interfere with the examination of the animal. No persons may be regularly utilized to hold or support animals during radiation exposures. Operating personnel may not perform this service except in cases where no other person is available.
Computed tomography x-ray systems. DHS 157.80(1)(1)
A computed tomography (CT) x-ray system shall meet all of the following requirements, as applicable:
Means shall be provided to terminate the x-ray exposure automatically by either de-energizing the x-ray source or shuttering the x-ray beam in the event of equipment failure affecting data collection. The termination shall occur within an interval that limits the total scan time to no more than 110% of its preset value through the use of either a back-up timer or devices which monitor equipment function. A visible signal shall indicate when the x-ray exposure has been terminated. The operator shall be able to terminate the x-ray exposure at any time during a scan, or series of scans under CT x-ray system control, of greater than one-half second duration.
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 mGy (100mR) 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 dimension greater than 20 centimeters.
Tomographic plane indication and alignment.
A computed tomography x-ray system shall meet all of the following plane indication and alignment requirements, as applicable:
A single tomogram system shall allow for visual determination of the tomographic plane or a reference plane offset from the tomographic plane.
A multiple tomogram system shall allow for visual determination of the location of a reference plane.
DHS 157.80 Note
Note: The reference plane may be offset from the location of the tomographic planes.
If a device using a light source is used to satisfy the requirements in subd. 2.
, the light source shall provide illumination levels sufficient to permit visual determination of the location of the tomographic plane or reference plane under ambient light conditions of up to 500 lux.
Beam-on and shutter status indicators and control switches. DHS 157.80(1)(c)1.1.
The CT x-ray control and gantry shall provide visual indication whenever x-rays are produced and, if applicable, whether the shutter is open or closed. Each emergency button or switch shall be clearly labeled as to its function.
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 mGy (100 mRem) in one 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 averaged over an area of 100 square cm with no linear dimension greater than 20 cm.
Indication of CT conditions of operation.
A CT x-ray system shall be designed such that the CT conditions of operation to be used during a scan or a scan sequence shall be indicated prior to the initiation of the scan or a scan sequence. On equipment having all or some of these conditions of operation at fixed values, this requirement may be met by permanent markings. Indication of CT conditions of operation shall be visible from any position from which scan initiation is possible.
Maximum surface CTDI100 identification.
The angular position where the maximum surface CTDI100 occurs shall be identified to allow for reproducible positioning of a CT dosimetry phantom.
CT x-ray systems containing a gantry manufactured after September 3, 1985.
A computed tomography x-ray system containing a gantry that was manufactured after September 3, 1985, shall meet all the following requirements:
The total error in the indicated location of the tomographic plane or reference plane may not exceed 5 millimeters.
If the x-ray production period is less than one-half second, the indication of x-ray production shall be actuated for at least one-half second. Indicators at or near the gantry shall be discernible from any point external to the patient opening where insertion of any part of the human body into the primary beam is possible.
The deviation of indicated scan increment versus actual increment may not exceed plus or minus one millimeter with any mass from 0 to 100 kilograms resting on the support device. The patient support device shall be incremented from a typical starting position to the maximum incremented 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 patient support device movement distance.
Premature termination of the x-ray exposure by the operator shall necessitate resetting of the CT conditions of operation prior to the initiation of another scan.
A CT x-ray system for human use may only be operated for diagnostic procedures by an American registry of radiologic technologists certified person who has been specifically trained in its operation.
A CT x-ray system for veterinary use may only be operated for diagnostic procedures by a person who is certified by the American registry of radiological technologists or has completed training equivalent to the requirements of Appendix L and has been specifically trained in its operation.
Combination systems which combine CT with another imaging device that uses radioactive material shall be operated by a person qualified by training in the safe use of radioactive materials and who meets the training requirements of Appendix L.
Information shall be available at the control panel regarding the operation and calibration of the system. The information shall include all of the following components:
Dates of the latest calibration and spot checks and the location within the facility where the results of those tests may be obtained.
Instructions on the use of the CT dosimetry phantom including a schedule of spot checks appropriate for the system, allowable variations for the indicated parameters and the results of at least the most recent spot checks conducted on the system.
The distance in millimeters between the tomographic plane and the reference plane if a reference plane is utilized.
A current technique chart available at the control panel, which specifies for each routine examination the CT conditions of operation and the number of scans per examination including body part size and correct kV/mA for that body part. The technique chart shall be used to adjust techniques based on the body part being examined.
Calibration and spot check measurements shall be made at a frequency recommended by the manufacturer. If the calibration or spot check of the CT x-ray system identifies that a system operating parameter has exceeded a tolerance established by the medical physicist, use of the CT x-ray system on patients shall be limited to those uses permitted by established written instructions of the medical physicist.
A facility shall follow the manufacturer's daily start up routines and preventative maintenance schedules for a specific computed tomography x-ray system.
DHS 157.80 History
History: CR 01-108
: cr. Register July 2002 No. 559
, eff. 8-1-02; CR 06-021
: renum. (1) (a) and (c) to be (1) (a) 1. and (c) 1., cr. (1) (a) 2. and 3. and (c) 2. and 3., am. (2) (a) Register October 2006 No. 610
, eff. 11-1-06; CR 09-062
: renum. (2) (a) to be (2) (a) 1. and 3. and am., cr. (2) (a) 2. Register April 2010 No. 652
, eff. 5-1-10.
Plan review and approval.
Prior to construction, the floor plans, shielding specifications and equipment arrangement of all new installations, or modifications of existing installations, utilizing ionizing radiation machines, including dental CT and dental cephalometric machines, shall be submitted to the department for review and approval.
DHS 157.81 Note
Note: Plans may be mailed to the department at: Department of Health Services, Radiation Protection Section, P.O. Box 2659, Madison WI 53701-2659 or package delivery to: Department of Health Services, Radiation Protection Section, Room 150, 1 West Wilson St, Madison WI 53702-0007.
Dental intraoral and panoramic, mammography, and bone density devices are exempt from this section.
A shielding plan for a facility with two or more x-ray rooms shall include a medical physicist or person approved by a medical physicist recommendation for shielding.
A shielding plan submitted for department review shall include all of the following:
A scale drawing of the room in which a stationary radiation machine system is located with such drawing indicating the use of areas adjacent to the room and an estimation of the extent of occupancy by a person in such areas. In addition, the drawing shall include all of the following:
The type and thickness of materials, or lead equivalency, of each protective barrier.
The use and occupancy of the areas surrounding an x-ray room, including occupied areas above or below an x-ray room.