Safety Code 35: Safety Procedures for the Installation, Use and Control of X-ray Equipment in Large Medical Radiological Facilities

Section B: Facility and Equipment Requirements

4.0 Other Equipment

Consideration must be given to other equipment, such as those used for personnel protection and equipment testing, which are necessary for ensuring the radiation safety of a radiological facility. Personnel protective clothing must provide adequate protection without being unduly restrictive and heavy. All test equipment must be properly maintained and carefully stored.

4.1 Protective Equipment

1. Protective lead aprons must provide attenuation equivalent to at least
   1. 0.25 mm of lead, for examinations where the peak X-ray tube voltage is 100 kV or less,
   2. 0.35 mm of lead, for examinations where the peak X-ray tube voltage is greater than 100 kV and less than 150 kV, and
   3. 0.5 mm of lead, for examinations where the peak X-ray tube voltages is 150 kV or greater.
2. For interventional procedures, where no other protective devices are used, full wrap around type protective gowns of 0.50 mm Pb in the front panels and 0.25 mm Pb in the back panels are recommended.
3. For interventional procedures, protective thyroid shields with an equivalent of 0.50 mm Pb are recommended.
4. For interventional procedures, in the situation where scatter radiation to the lenses of eye could approach the annual equivalent dose limit of 150 mSv, the use of leaded glasses is recommended.
5. Protective gonad shields for patients must have a lead equivalent of at least 0.25 mm Pb and should have a lead equivalent thickness of 0.5 mm at 150 kVp. Gonad shields must be of sufficient size and shape to exclude the gonads completely from primary beam irradiation.
6. Protective gloves or gauntlets must possess at least a 0.25 mm Pb equivalency. Thess protections must be provided throughout the glove, including fingers and wrist.
7. The lead equivalent thickness of the protective material used must be permanently and clearly marked on all protective equipment and apparel.
8. Ceiling-mounted lead acrylic screens and moveable shields should provide protection equivalent to at least 0.50 mm Pb. The attenuation value must be marked on all protective screens and shields.
9. All protective equipment must be tested on a yearly basis for integrity and results must be included in the quality control test records.
10. Defective equipment must be removed from clinical use.
11. Protective equipment must be stored and maintained according to manufacturers' instructions.

4.2 Test Equipment

1. All equipment used for acceptance and quality control testing must be evaluated for their functioning and performance on a regular basis.
2. All sensitometric and densitometric equipment, dose meters, tube voltage meters should be calibrated on a regular basis according to manufacturers' recommendations.
3. All phantoms and other equipment used for the assessment of image quality, dose and system performance should be checked for damage or any condition which may affect their use.
4. Test equipment should be stored away from heat, direct sunlight, and high humidity. They must be operated following manufacturers' recommendations.

5.0 Radiation Protection Surveys

A radiation protection survey is an evaluation, conducted by an expert, of the radiation safety of a radiological facility. The survey is intended to demonstrate that the X-ray and auxiliary equipment function properly and according to applicable standards, and that the equipment is installed and used in a way which provides maximum radiation safety for operators, patients and others. Safety measures such as protective equipment and shielding are also examined to ensure that they are present and provide the required protection. It is important, therefore, that X-ray facilities are inspected at regular intervals.

5.1 General Procedures

Routine operation of any new installation or an installation which has undergone modifications should be deferred until a complete survey has been made by an expert. The expert is an individual who is qualified by education and experience to perform advanced or complex procedures in radiation protection that generally are beyond the capabilities of most personnel within the facility. These procedures include evaluation of the facility design to ensure adequate shielding is in place, inspection and evaluation of the performance of X-ray equipment and accessories, and evaluation and recommendation of radiation protection programs. The owner of the facility (or another delegated staff member such as the Radiation Protection/Safety Officer) must contact the appropriate regulatory agency to ascertain inspection and acceptance testing procedures in that jurisdiction. Some jurisdictions may require that the facility be declared in compliance with applicable governmental regulations prior to operations.

For a new facility, it is particularly advantageous to make visual inspections during construction, to ensure compliance with specifications and to identify faulty material or workmanship, since deficiencies can be remedied more economically at this stage than later. Such inspections should include determination of thickness of lead and/or concrete thickness and density, degree of overlap between lead sheets or between lead and other barriers, as well as thickness and density of leaded glass used in viewing windows.

For existing installations, a survey must be carried out after any changes are made, which might produce a radiation hazard. This includes alteration of protective barriers, equipment modification and replacement, changes in operating procedures, or increased workloads.

Finally, radiation protection surveys must be carried out at regularly scheduled intervals during routine operations to detect problems due to equipment failure or any long-term trends toward a decrease in the level of radiation safety. The frequency at which radiation protection surveys are to be conducted is dependant on the type of facility, the type of equipment used and the type of examinations performed. Facilities should contact the applicable regulatory authority to establish the survey schedule.

The results of such surveys, including conclusions drawn by the expert, must be submitted to the owner or responsible user in a written report. All such reports must be retained by the owner or responsible user. For federal facilities, radiation survey reports should be maintained for 5 years and personnel dosimetry records for the lifetime of the facility.

5.2 Survey Report

The survey report must present, in a clear systematic way, details and results of the measurements carried out, as well as the conclusions drawn and recommendations made by the surveyor. Any unusual findings about the equipment itself, the facility or operating procedures, which could affect the safety of operators or other persons in the vicinity of the X-ray facility must be clearly identified.

The survey report must include the following:

1. a sketch of the facility, showing the location of the X-ray equipment and control booth within the facility as well as the nature and occupancy of the areas adjoining the facility;
2. identification of the X-ray equipment (i.e., the name of the manufacturer, model designation and serial number of the generator, control, X-ray tube assembly, X-ray table, etc. as applicable) and the date, or at least approximate date manufactured;
3. the method of support of the X-ray tube assembly (i.e., floor-to-ceiling tube stand, ceiling suspended over-table tube, etc.);
4. observations of the operational conditions (both electrical and mechanical) of the X-ray equipment at the time of the survey;
5. the actual or estimated total workload of the facility, as well as the workload apportioned into various X-ray beam directions and procedures used, etc.;
6. results of radiation measurements carried out both inside and outside the controlled area under "typical" operating conditions. The locations at which the measurements are made;
7. an assessment of the condition of patient restraints, protective aprons, gloves, mobile protective barriers and other protective devices;
8. an estimate of potential exposures to personnel and general public in or around the facility;
9. an evaluation of the X-ray performance and the imaging or diagnostic performance (this may include performing applicable quality control tests from sections C3.1 to C3.6;
10. a summary of typical loading factors used and a measurement of the total filtration in the X-ray beam;
11. an assessment of radiological techniques from the point of view of radiation safety and an assessment of the Diagnostic Reference Levels for the facility. Attention must be drawn to any practices which are or could be detrimental to the patient or to personnel working in the facility. Recommendations of improved or safer techniques should be made in such cases;
12. results of investigations of any unusually high exposures from previous personnel dosimetry reports and recommendations on whether other persons should be included in the personnel dosimetry service;
13. a review of the facilities quality assurance program to ensure it exists and is maintained, including quality control testing records; and
14. recommendations regarding the need for a follow-up survey.

6.0 Disposal of X-ray Equipment

When X-ray equipment is considered for disposal, an assessment should be made as to whether the equipment can be refurbished and/or recycled. Communication with the manufacturer or supplier of the equipment should be made as to whether the equipment or components of the equipment can be recycled or returned. Once the decision has been made to dispose of X-ray equipment, an assessment must be made to determine if any equipment components contain hazardous materials. For example the X-ray tube may contain polychlorinated biphenyls (PCBs) and lead may be present in the X-ray tube housing. To ensure equipment is not unsafely operated after disposal, it should be made inoperable before disposing. The cables that power the equipment and other electrical connections should be disconnected and removed. It is recommended that radiological facilities, under provincial or territorial jurisdiction contact the responsible agency in their respective province or territory for further information. A listing of these responsible agencies is provided in Appendix V.