Section 157.80. Computed tomography x-ray systems.

 

(1)   Equipment requirements. A computed tomography (CT) x-ray system shall meet all of the following requirements, as applicable:

(a) Termination of exposure.

1. 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.

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 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.

3. Compliance shall be determined by measurements averaged over an area of 100 square centimeters with no linear dimension greater than 20 centimeters.

(b) Tomographic plane indication and alignment. A computed tomography x-ray system shall meet all of the following plane indication and alignment requirements, as applicable:

1. A single tomogram system shall allow for visual determination of the tomographic plane or a reference plane offset from the tomographic plane.

2. A multiple tomogram system shall allow for visual determination of the location of a reference plane.

3. 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.

(c) Beam-on and shutter status indicators and control switches.

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.

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 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.

3. Compliance shall be determined by measurements averaged over an area of 100 square cm with no linear dimension greater than 20 cm.

(d) 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.

(e) 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.

(f) 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:

1. The total error in the indicated location of the tomographic plane or reference plane may not exceed 5 millimeters.

2. 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.

3. 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.

4. 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.

(2)   Operating procedures.

(a)

1. 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.

2. 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.

3. 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.

(b) 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:

1. Dates of the latest calibration and spot checks and the location within the facility where the results of those tests may be obtained.

2. 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.

3. The distance in millimeters between the tomographic plane and the reference plane if a reference plane is utilized.

4. 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.

(c) 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.

(d) A facility shall follow the manufacturer's daily start up routines and preventative maintenance schedules for a specific computed tomography x-ray system.

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.

Note

The reference plane may be offset from the location of the tomographic planes. Microsoft Windows NT 6.1.7601 Service Pack 1