WSR 08-01-135



[ Filed December 19, 2007, 10:08 a.m. ]

Original Notice.

Preproposal statement of inquiry was filed as WSR 06-07-033.

Title of Rule and Other Identifying Information: Adopting new chapter 246-225A WAC, Radiation safety and diagnostic image quality standards for dental facilities, and repealing WAC 246-225-110 Intraoral dental radiographic systems.

Hearing Location(s): DOH Marketing Center, Creekside Three at CenterPoint, 20435 72nd Avenue South, Suite 200, Conference Room 1, Kent, WA 98032, on February 6, 2008, at 2:00 p.m.

Date of Intended Adoption: February 7, 2008.

Submit Written Comments to: Ellen Haars, Office of Radiation Protection, P.O. Box 47827, Olympia, WA 98504-7827, web site, fax (360) 236-2266 by February 6, 2008.

Assistance for Persons with Disabilities: Contact Phyllis Hurtado by February 1, 2008, TTY (800) 833-6388 or 711.

Purpose of the Proposal and Its Anticipated Effects, Including Any Changes in Existing Rules: This rule revision will create a separate, user-friendly chapter for dentists using X-ray machines. This rule is needed to make it easier for the dental community to find and comply with pertinent regulations and incorporates outcome-based regulations as appropriate. Specific changes include requiring quality assurance for X-ray film processing and disallowing use of low kilovolts peak (kVp) (higher exposure) dental X-ray machines. These changes, along with reinforcing the current prohibition of hand-held X-ray units, will limit unnecessary higher radiation exposure to patients.

Reasons Supporting Proposal: This chapter defines the regulatory standards for dental X-ray radiation safety. Adopting clear language and specific requirements will improve operator and patient safety. Adding quality assurance requirements for X-ray film processing will improve the quality of the X-ray film and reduce the need for unnecessary exposure to radiation due to X-ray retakes. Disallowing use of the older, low kVp dental X-ray machines, which deliver higher doses of radiation, will limit unnecessary higher radiation exposure to patients.

Statutory Authority for Adoption: RCW 70.98.050 and 70.98.080.

Statute Being Implemented: RCW 70.98.050 and 70.98.080.

Rule is not necessitated by federal law, federal or state court decision.

Name of Proponent: Department of health, governmental.

Name of Agency Personnel Responsible for Drafting, Implementation and Enforcement: Ellen Haars, P.O. Box 47827, Olympia, WA 98504-7827, (360) 236-3231.

A small business economic impact statement has been prepared under chapter 19.85 RCW.

Small Business Economic Impact Statement

1. Briefly Describe the Proposed Rule: The current chapter 246-225 WAC contains rules and standards for all professions using X-ray machines in the healing arts. As such, it has been difficult for practitioners to get a clear understanding of the rules applying to their specific practice type. This rule making will create a separate user-friendly chapter for dentists with emphasis placed on improved patient safety and quality assurance. In addition, the department of health (department) proposes to:

a. Disallow the use of low fifty kVp machines that unnecessarily increase radiation exposure to patients and staff; and

b. Require periodic monitoring of image processors in dental X-ray so that consistent, high quality radiographic quality is achieved. This is expected to reduce the number of X-ray retakes and unnecessary exposure to patients and dental staff.

The proposed rule also repeals WAC 246-225-110 Intraoral dental radiographic systems.

2. Is a Small Business Economic Impact Statement (SBEIS) Required for this Rule? Yes. Washington state has approximately 2,950 dental facilities using around 11,000 X-ray machines, and all of them qualify as small businesses according to the definition (less than fifty employees). It should be noted that even though all dental facilities are categorized as "small businesses," some are smaller than others. For example, one might find a rural dentist practicing with only one X-ray machine, or larger facilities staffed with a few dentists, a large number of assistants and hygienists, and six to ten machines. There will be an impact on some facilities that have fifty kVp X-ray units since they will have to dispose of these and purchase newer equipment of higher kVp. In addition, all facilities will have to implement the periodic monitoring of film processors whether they have one machine or many, but the cost of implementing this quality control is so small that there will be little impact on a small dental facility versus a large one.

3. Which Industries Are Affected by this Rule? Dentists, SIC code 8021.

4. What are the costs of complying with this rule for small businesses (those with fifty or fewer employees) and for the largest 10% of businesses affected?

a. Proposed WAC 246-225A-080, prohibiting low kVp X-ray machines. For the machines that operate at fifty kVp, 128 out of 2,900 facilities have such a machine. Each machine replacement would cost about $4,500 if purchased new; however, many higher kVp machines are available on the used equipment market and are reasonable options. Used machines would cost around $2,500. It is estimated that most affected dental businesses will be able to amortize this equipment over at least three years, so the highest annual cost would be between $833 (used) to $1,500 (new) per year. Note that most fifty kVp machines have been in use for over twenty years, so their initial cost has been recovered many times over, and a new machine's cost can be amortized over several years.

b. Proposed WAC 246-225A-110, requiring weekly monitoring of image processors. For the requirement of quality control on image processing, all facilities would have to devote some staff time to making the required periodic tests. The estimated time for this activity is fifteen minutes per week. The department assumes that the duties would be performed by a dental assistant. The average salary of a dental assistant is $16.64 per hour plus payroll taxes and benefits; therefore, each facility would be expected to spend $4.16 per week, or $213.32 plus payroll taxes and benefits per year. This would be the case for around 80% of dental facilities that use traditional film and chemical-based film processors. Several options are available for performing the required image quality control tests; one is a small test tool that costs $30. A more expensive option is a combination of a densitometer and a sensitometer that together cost approximately $2,000. These options would both be one-time costs. The remaining 20% of dental offices use digital imaging and a standard quality control test is not available at this time.

5. Does the Rule Impose a Disproportionate Impact on Small Businesses? There is no disproportionate impact because all the businesses regulated by this proposed rule are small. However, because all the businesses are small and yet vary in size, the impact upon them was considered while developing the rule and efforts were made to limit that impact. Establishing performance based regulation for periodic quality control testing of image processors that allow the use of inexpensive devices is included in the proposed rule to limit the impact to small businesses. Therefore, not even the very small facilities regulated by this proposed rule will have a disproportionate burden placed upon them.

6. If the Rule Imposes a Disproportionate Impact on Small Businesses, What Efforts Were Taken to Reduce That Impact (or Why Is it Not "Legal and Feasible" to Do So) By:

a) Reducing, modifying, or eliminating substantive regulatory requirements? Not applicable.

b) Simplifying, reducing, or eliminating record-keeping and reporting requirements? Not applicable.

c) Reducing the frequency of inspections? Not applicable.

d) Delaying compliance timetables? Because we recognize all dental facilities are small businesses, we delayed compliance for replacement of the low kVp dental X-ray units as well as periodic monitoring of image processors until July 1, 2008.

e) Reducing or modifying fine schedules for noncompliance? Not applicable.

f) Any other mitigation techniques? Not applicable.

7. Will Compliance with the Proposed Rule Cause Affected Businesses to Create or Lose Jobs? An estimated one hundred twenty-eight dental businesses would need to replace old fifty kVp X-ray machines under this proposed rule, at an estimated cost for a new seventy kVp machine of $4,500, or about $2,500 for a used seventy kVp machine. It is estimated that most affected dental businesses will be able to amortize this equipment over at least three years, so the highest annual cost would be between $833 (used) to $1,500 (new) per year. These costs would not be expected to cause an affected business to create or lose jobs.

Some dental businesses may choose to pay cash for a new seventy kVp X-ray machine. In those cases, it is possible that those businesses may need to consider reducing employment by 0.15 to 0.25 full-time positions, depending on the affected position(s) for one year to offset the one-time cost of a seventy kVp X-ray machine.

Quality improvement testing costs under the proposed rule are low, and are not expected to cause affected businesses to create or lose jobs.

8. How Are Small Businesses Involved in the Development of this Rule? A fifteen-member workgroup reviewed an initial staff proposal. Department of health, office of radiation protection staff held meetings with members of the dental quality assurance commission and the Washington state dental association. Proposed changes were also posted on the dental quality assurance commission listserv for review and comment. Dental X-ray registrants, the University of Washington Dental School, X-ray stakeholders, and interested parties were invited to participate in an ad-hoc workgroup for comments and discussion on the informal rule draft. Comments received as a result of these activities were considered and incorporated as appropriate.

A copy of the statement may be obtained by contacting Phyllis Hurtado, Office of Radiation Protection, X-ray Program, P.O. Box 47827, Olympia, WA 98504-7827, phone (360) 236-3239, fax (360) 236-2266, e-mail

A cost-benefit analysis is required under RCW 34.05.328. A preliminary cost-benefit analysis may be obtained by contacting Phyllis Hurtado, Office of Radiation Protection, X-ray Program, P.O. Box 47827, Olympia, WA 98504-7827, phone (360) 236-3239, fax (360) 236-2266, e-mail

December 19, 2007

Mary C. Selecky




     The following section of the Washington Administrative Code is repealed:
WAC 246-225-110 Intraoral dental radiographic systems.


Chapter 246-225A WAC


WAC 246-225A-001   Purpose and scope.   This chapter establishes facility design and operation requirements for the use of dental X-ray equipment according to chapter 70.98 RCW. The scope of this chapter pertains to dental intra-oral and extra-oral radiography and establishes radiation safety requirements for patients, dental employees, and the public; and establishes optimal diagnostic image processing requirements.


WAC 246-225A-010   Definitions.   As used in this chapter, the following definitions apply:

"Barrier" (see "protective barrier").

"Beam" (see "X ray").

"Beam-limiting device," sometimes called a collimator or cone, means a device that controls the size of the X-ray field.

"Cephalometric" means X-ray imaging specific to the human head and jaw.

"Computed radiography (CR)" means creating an X-ray image using plates consisting of a special phosphor that when exposed to radiation and then processed by a scanner, provides the information to a computer for display and manipulation.

"Computed tomography (CT)" means creating a cross-sectional X-ray image generated by an X-ray source and detector moving around the patient's body.

"Control panel" means the part of the X-ray system where the switches, knobs, pushbuttons, and other hardware necessary to operate the X-ray system are located.

"Dead-man switch or button" means a switch designed so that it can only be operated by continuous pressure on the switch by the operator, and when released before the preset exposure time will stop the exposure.

"Department" means the department of health, which is the state radiation control agency under chapter 70.98 RCW.

"Detector" means a device capable of receiving and recording an X-ray image.

"Direct digital radiography (DR)" means creating an X-ray image by sending signals directly from a solid state detector to a computer for display and manipulation.

"Diagnostic source assembly" means the combination of the tube housing assembly and the collimator.

"Direct scattered radiation" means radiation discharged in a straight line from the object being radiographed.

"Exposure," as the context implies, means:

(a) The number of electrons, measured in coulombs per kilogram of air, released through the ionization of air molecules by electromagnetic radiation; and

(b) An occupational worker or patient being subjected to radiation either directly or indirectly.

"Extra-oral radiography" means creating a film or digital X-ray image on an image receptor placed outside the mouth. Examples include panoramic and cephalometric X rays.

"Filter" means material, such as copper or aluminum, placed in the useful beam of the X ray to block selected energies, and in a safelight to block light that could fog the X-ray film.

"Focal spot" means the area on the anode end of the X-ray tube bombarded by the electrons accelerated from the cathode and from which the useful X-ray beam begins.

"Grid" means a device placed between the patient and the image receptor in extra-oral radiography that reduces scattered radiation that would decrease the quality of the image being created.

"Half-value layer (HVL)" means the thickness of material that reduces the intensity of radiation to one-half of its original value.

"Healing arts screening" means using X-ray equipment without an order by a licensed practitioner on an individual who does not have a known or diagnosed disease or symptom to learn if the individual may have an indication of ill health.

"Image receptor" means a device that transforms an X-ray beam into a visible film or digital image.

"Intra-oral radiography" means creating a film or digital X-ray image on an image receptor placed inside the mouth.

"Kilovolt (kV)" means the unit used to measure electrical energy.

"Kilovolts peak (kVp)" means the highest possible voltage across the X-ray tube during an exposure (see also "peak tube potential").

"Leakage radiation" means radiation coming from the X-ray tube, other than the main X-ray beam.

"Leakage technique factors" means the technique factors associated with the tube housing assembly that are used to measure leakage radiation. They are defined as the maximum rated peak tube potential and the maximum rated continuous tube current at the maximum peak tube potential.

"Licensed practitioner" means an individual who holds a license to practice dentistry under chapter 18.32 RCW.

"Milliampere (mA)" means the unit used to measure electrical current in an X-ray tube.

"Milliampere second (mAs)" means the product of the electrical current in the X-ray tube in milliamperes and the time of exposure in seconds.

"Mobile equipment" (see "X-ray system").

"Operator" means a person working under the direction of a licensed practitioner to operate X-ray equipment and who has been properly trained according to WAC 246-225A-020.

"Operatory" means a room in which dental health care procedures are performed.

"Peak tube potential" means the maximum voltage in the X-ray tube during an exposure.

"Portable equipment" (see "X-ray equipment").

"Position-indicating device" means a device on X-ray equipment that shows where the X-ray beam will be directed and establishes the distance from the X-ray tube to the patient's body. The device may or may not incorporate or serve as a beam-limiting device.

"Primary beam" (see "useful beam").

"Primary protective barrier" means the material placed in the useful beam, beyond the patient and image receptor, to reduce remnant primary beam exposure.

"Protected area" means a space for X-ray equipment operators that is shielded so that X-ray exposures are reduced enough to meet the exposure limits of WAC 246-221-010 (Occupational dose limits for adults) and WAC 246-220-007 (Statement of philosophy). In addition, the space must have no exposure to direct scattered radiation.

"Protective apron" means a garment made of radiation absorbing materials used to reduce a person's radiation exposure.

"Protective barrier" means a structure made of radiation absorbing material used to reduce radiation exposure.

"Quality assurance" means a program designed to produce high quality X-ray images at minimal cost and with minimal patient exposure to radiation.

"Quality control" means the regular testing of X-ray equipment and associated equipment, such as processors, to verify that the equipment is working properly. Controls include performing routine tests of the diagnostic X-ray imaging system such as X-ray beam output, viewing X-ray test images, and continually adjusting the performance of the X-ray equipment and processor to an optimal and consistent level.

"Radiation safety" means ways to protect patients and staff from unnecessary radiation exposure. Safety measures may include patient exposure reduction, image quality improvement, diagnostic imaging system quality assurance, radiation measurements, dose evaluations, compliance with state and federal regulations, and related issues.

"Radiographic" means the production of an image created when an X-ray pattern exits an X-rayed object.

"Radiography" means a way of creating a permanent film or digital image using X rays.

"Recording" means creating a permanent image, on film or in a computer, from an X-ray exposure.

"Registrant" means the owner or controller of the radiation equipment who is responsible for the safe operation of the radiation equipment in accordance with this chapter and chapter 70.98 RCW.

"Registration" means providing required information and continuing contact with the department.

"Remnant primary beam" means the part of the useful beam that completely passes through the patient and image receptor.

"Safelight" means a lamp with a filter that is used in an X-ray darkroom to provide enough light to see, but not enough to over-expose the film.

"Scattered radiation" means radiation that has changed direction as it passes through matter (see also "direct scattered radiation").

"Secondary protective barrier" means an object or material sufficient to reduce stray radiation to the required degree as stated in chapter 246-221 WAC (Radiation protection standards).

"Source-to-image-receptor distance (SID)" means the distance from the focal spot in the X-ray tube to the center of the surface of the image receptor.

"Source" means the focal spot of the X-ray tube.

"Source-to-skin distance (SSD)" means the distance between the focal spot of the X-ray tube and the nearest point on the patient's skin where the primary beam enters.

"Stationary equipment" (see "X-ray system").

"Stray radiation" means the sum of leakage and scattered radiation.

"Technique chart" means a written instruction or guide that X-ray equipment operators use to determine which radiation technique factors to select for each type of radiographic examination.

"Technique factors" means the X-ray system settings selected for a given radiographic examination. They are specified as the peak tube potential in kilovolts and either:

(a) Tube current measured in milliamperes and exposure time in seconds or pulses; or

(b) The product of tube current and exposure time expressed in milliampere seconds.

"Tube" means a glass tube that produces an X ray when high-voltage electricity is passed between the cathode at one end and the anode at the other.

"Tube housing assembly" means the X-ray tube and its housing. It includes high-voltage and/or filament transformers and other appropriate elements when they are contained within the tube housing.

"Tube housing port" means the portion of the tube housing assembly that the X rays pass through.

"Useful beam" means the radiation that passes through the tube housing port and the opening of the beam-limiting device.

"Variance" means a department-authorized alternative to a requirement of this chapter.

"X ray" means a beam of ionizing radiation produced by a machine.

"X-ray control" means a device that controls how much electricity enters the X-ray high-voltage generator and/or the X-ray tube. It includes equipment that controls the technique factors for an exposure.

"X-ray equipment" means the entire X-ray system or parts of the system.

"X-ray exposure switch or button" means the part of the X-ray system that when engaged generates the production of an X ray. (See also "dead-man switch or button.")

"X-ray high-voltage generator" means a device that supplies electrical energy to the X-ray tube to create an X-ray beam.

"X-ray system" means all of the components of a machine used for the controlled production of X rays. It includes minimally an X-ray high-voltage generator, an X-ray control, a tube housing assembly, a beam-limiting device, and the necessary supporting structures. Additional components which function with the system, such as the image receptor, are considered integral parts of the system. Types of X-ray systems are:

(a) "Mobile" means X-ray equipment mounted on a permanent base with wheels and/or casters for moving the X-ray equipment fully assembled. It is intended to be taken from one geographical location to another or from one room to another.

(b) "Portable" means X-ray equipment designed to be hand-carried, but not hand-held during use.

(c) "Stationary" means X-ray equipment that is installed in a fixed location, such as bolted to a floor or wall.

"X-ray tube" means any electron tube which is designed to be used primarily for the production of X rays.


WAC 246-225A-020   General requirements and administrative controls.   The registrant is responsible for directing the operation of the X-ray system and assuring the provisions of WAC 246-222 (Radiation protection -- Worker rights) are met. In addition, the registrant shall:

(1) Verify that any operator of the X-ray equipment is trained and able to show that he or she can correctly and safely operate the X-ray equipment used by the registrant. The department may determine compliance by observation, interview, and/or testing in these subject areas:

(a) Knowledge of the X-ray system controls and their function;

(b) Knowledge of radiation safety and shielding methods for both operators and patients;

(c) Proper image processing.

(2) Post a technique chart at each X-ray system's control panel that specifies the following information for the examinations being performed by that system:

(a) Patient's teeth, jaw, or head anatomy versus technique factors to be used;

(b) If applicable, settings for automatic exposure devices; and

(c) The type and size of screen-film combination or other imaging system to be used.

(3) Require that all individuals, other than the patient being examined:

(a) Be positioned so that no part of the body, including the extremities, will be struck by the useful beam;

(b) Be protected from stray radiation by wearing protective aprons or by being positioned behind protective barriers of not less than 0.25 millimeters lead equivalent; and

(c) Not be present in the room during the X-ray exposure, except as described in subsection (4)(b) of this section.

(4) Use mechanical holding devices when a patient, film, or image receptor needs to be supported during an X-ray exposure when the technique permits.

(a) No individual shall be allowed to routinely hold a patient, film, or image receptor; and

(b) Holding a patient, film, or image receptor shall only be allowed in very unusual and rare situations. In these cases the patient's name, the date, and the name of the person holding the patient must be recorded in writing and maintained by the registrant for at least five years.

(5) Comply with the occupational exposure limits and the requirements for the determination of prior occupational dose stated under WAC 246-221-020 (Determination of prior occupational dose) for all individuals associated with the operation of the registrant's X-ray system. In addition, when protective clothing or devices are worn on portions of the body and a dosimeter is required, at least one dosimeter shall be used and documented as follows:

(a) When an apron is worn, the dosimeter shall be worn at the collar outside the apron;

(b) The dose to the whole body based on the maximum dose attributed to the most critical organ must be recorded on the reports required under WAC 246-221-230 (Records important to radiation safety). If more than one dosimeter is worn, each dose must be identified with the area where the dosimeter was worn on the body.

(6) Require personnel dosimetry monitoring of an operator when:

(a) Mobile or portable X-ray systems are used, i.e., when X-ray exposure buttons or X-ray exposure switch cords are used that allow the operator to stand in an unprotected area during exposures; or

(b) Measurements by the department show ten percent of the exposure limits as specified under WAC 246-221-010 (Occupational dose limits for adults) are exceeded.

(7) Use only X-ray equipment, and the accessories used in connection with making X rays, that meet the requirements of this chapter.

(8) Not allow anyone in the dental office to operate X-ray equipment for diagnostic purposes when the X-ray equipment:

(a) Does not meet the provisions of this chapter; or

(b) Is malfunctioning or threatens the health or safety of a patient, dental employee, or the public.

(9) Not allow patients to be exposed to the useful X-ray beam except for healing arts purposes. Only a licensed practitioner may authorize an exposure to the useful beam. Deliberate exposure of an individual for the following purposes is prohibited:

(a) Training, demonstration, or other purposes unless there are also healing arts requirements and proper prescription provided; or

(b) Except for exposure required under Medicare provisions, any exposure for which the sole purpose is satisfying a third party's prerequisite for reimbursement under any health care plan.


WAC 246-225A-025   X-ray system radiation safety procedure.   If required by the department, the registrant shall adopt a written X-ray system radiation safety procedure.

(1) The department may require an X-ray system radiation safety procedure if there is reason to believe the registrant needs increased attention because of:

(a) Poor operator staff training;

(b) Extremely high workload;

(c) Increased risk of exposure due to staff supporting patients during radiography;

(d) Increased risk of exposure to scattered radiation;

(e) Unnecessarily high patient exposure values; or

(f) Other similar conditions.

(2) The X-ray system radiation safety procedures shall:

(a) Address patient and occupationally exposed personnel safety; and

(b) Define any restrictions of the operating technique required for safe operation of the X-ray system.


WAC 246-225A-026   Healing arts screening program.   Any individual proposing to conduct a healing arts screening program shall obtain approval from the state health officer as required in WAC 246-225-99930 before conducting the screening program.


WAC 246-225A-030   Prohibited equipment.   Registrants shall use only mobile or stationary X-ray equipment as defined in WAC 246-225A-010 for intra-oral or extra-oral radiography. Registrants shall not use:

(1) X-ray systems designed to be hand-held during exposures of human patients; or

(2) Dental fluoroscopy without electronic amplification.


WAC 246-225A-040   Dental X-ray rule variance request.   A registrant may submit a written request to the department for a variance from the applicable regulations. The registrant shall not use X-ray equipment on patients until the department approves the variance request.

(1) The written request shall be addressed to: X-ray Supervisor, Office of Radiation Protection, Department of Health, P.O. Box 47827, Olympia, Washington 98504-7827, and must include:

(a) The specific WAC reference or references of the rule for which the variance is requested;

(b) An explanation of the circumstances involved, and the reason why the rule cannot be followed;

(c) A description of how the proposed alternative meets the intent of the rule and how the registrant shall protect patients, dental employees, and the public;

(d) A description of the X-ray system to be used with supporting pictures or documents; and

(e) The time period for which the variance is requested.

(2) The department may impose conditions that may be necessary to protect human health and safety during the term of the variance.

(3) If necessary, the department may require the registrant to submit additional information.

(4) The department may conduct an on-site variance inspection to verify the information provided or if it determines that an inspection is necessary.

(5) As determined by the department, variances can be permanent or temporary.

(6) The department may at any time revoke a variance if it is determined that the conditions of the variance are not being followed.


WAC 246-225A-050   Dental X-ray facility design.   All registrants proposing to use X-ray equipment designed to produce computed tomography images using a "ring detector" type CT, or where medical X-ray systems are used for dental imaging, shall submit shielding and floor plans to the department for review. The submittal shall be based on the criteria and methods found in National Council on Radiation Protection and Measurements (NCRP) report #147, issued November 19, 2004. The intent of this requirement is to assure protection of patients, dental employees, and the public. A copy of this report is available for review at Department of Health, Office of Radiation Protection, 111 Israel Road S.E., Tumwater, Washington. Shielding and floor plans shall meet the following requirements:

(1) Each X-ray exposure switch or button shall be located to meet the following criteria:

(a) For stationary X-ray systems, the X-ray exposure switch or button shall be permanently mounted in a protected area (such as a corridor outside the room) so that the operator can make an exposure only from the protected area; and

(b) Mobile X-ray systems shall have an X-ray exposure switch or button located at the end of a cord at least twelve feet (3.7 meters) long.

(2) Shielding for cephalometric X ray shall meet the following criteria:

(a) Be at least one foot (30.5 centimeters) larger, in both the horizontal and vertical directions, than the area of the primary beam where it strikes the nearest wall; and

(b) Shielding between the nearest wall struck by the primary beam and the next occupied area shall have two-pound lead or equivalent installed in the wall (based on 20 films per week). Exterior walls or concrete block walls need no additional shielding.

(3) Acceptable shielding materials for dental X-ray facilities are as follows:

(a) The minimum shielding for intra-oral stray radiation protection is standard gypsum wallboard/sheetrock construction (two layers each of five-eighths inch thickness).

(b) Where windows are provided to observe patients during radiography, the windows are at least one-half inch plate glass, or equivalent ability to reduce exposure.

(c) All other materials used for shielding between operatories and for operator protection areas are equivalent to 0.2 millimeters of lead.

(4) Barriers between dental X-ray rooms and dental operatories where intra-oral X-ray equipment is installed shall meet the following criteria:

(a) Be at least six feet (1.83 meters) high and composed of materials capable of reducing scattered radiation as required under subsection (3) of this section;

(b) There shall be no line of sight between workers or patients in one operatory and the X-ray tube housing assembly in the next operatory when that X-ray tube housing assembly is in its operating position;

(c) X-ray tube housing assemblies shall not be mounted between operatories on top of barriers less than six feet (1.83 meters) high, unless those barriers are at the foot end of the patient couches, and there is no line of sight between operatories.


WAC 246-225A-060   General requirements for all dental X-ray systems.   Registrants shall use only dental X-ray systems and medical X-ray systems for dental imaging that meet the following requirements:

(1) The leakage radiation from the tube housing assembly, measured at a distance of one meter in any direction from the source, shall not exceed 100 milliroentgens in one hour when the X-ray tube is operated at its leakage technique factors. The department will determine compliance by measuring leakage averaged over an area of 100 square centimeters with no dimension of that area greater than 20 centimeters.

(2) The half-value layer of the useful beam for a given X-ray tube potential shall not be less than the values shown in Table 1 of this section. To determine a half-value layer at an X-ray tube potential which is not listed in Table 1 of this section, linear interpolation or extrapolation may be made.

Table 1

Design operating range (kilovolts peak) Measured potential (kilovolts peak) Half-value layer (millimeters of aluminum equivalent)
70 and below 70 and below 1.5
Above 70 71 2.1
80 2.3
90 2.5
100 2.7

(3) If two or more X-ray tubes are controlled by one X-ray exposure switch or button, the tube or tubes in operation shall be clearly marked before an exposure, on both the X-ray control panel and near or on the selected tube housing assembly.

(4) The tube housing assembly supports shall be adjusted so that the tube housing assembly remains stable and does not drift during an exposure unless the tube housing movement during exposure is a designed function of the X-ray system. The X-ray system and/or tube housing assembly shall not be hand-held during exposure.

(5) Each X-ray control shall have a dead-man switch or button.

(6) Technique indicators shall be set as follows:

(a) All exposure technique factors shall be set on the control panel before the exposure begins, except when automatic exposure controls are used. When automatic exposure controls are used, any preselected settings for each exposure shall be indicated.

(b) On equipment having fixed technique factors, the requirement in (a) of this subsection may be met by permanent markings or labels.

(7) Linearity shall be measured as follows:

(a) The difference between the ratio of milliroentgens (mR) exposure to milliampere second (mAs) at one milliampere (mA) or mAs setting and the ratio of mR exposure to milliampere second (mAs) at another milliampere (mA) or mAs setting must not exceed 0.1 times the sum of the ratios. This is written as:

X1 - X2 ≤ 0.10 (X1 + X2)

Where X1 and X2 are the ratios (mR/mAs) for each mA or mAs setting.

(b) The measurement shall be performed at any selection of mA or mAs without regard to focal spot size, provided neither focal spot size is less than 0.45 millimeters.

(8) When four exposures are made at identical operating settings, the difference between the maximum exposure (Emax) and the minimum exposure (Emin) must be less than or equal to ten percent of the average exposure (E). This is written as:

(Emax - Emin) ≤ 0.1E

(9) The difference between the kVp indicated on an X-ray system and the measured kVp shall not be greater than ten percent of the indicated kVp.

(10) Timers shall be able to:

(a) Stop the exposure at a preset time interval, a preset product of current and time, a preset number of pulses, or a preset radiation exposure to the image receptor; and

(b) Reset automatically to the initial setting or to zero when the exposure is stopped.

(11) X-ray equipment shall not be operated when the timer is set to the zero or off position if either position is provided.

(12) Each X-ray control shall have a visual indicator (such as a light) or audible signal so that the operator knows that X rays are being produced or the exposure is occurring or has ended.


WAC 246-225A-070   Special requirements for dental extra-oral radiography.   Registrants shall use X-ray systems for extra-oral radiography that meet the following requirements for:

(1) Beam limitation.

(a) X-ray equipment designed for only one image receptor size at a fixed source-to-image-receptor distance (SID) shall be able to limit the size of the beam at the plane of the image receptor to no larger than the image receptor, and to align the center of the X-ray beam with the center of the image receptor to within two percent of the SID. In the case of extra-oral imaging systems where the image receptor can be turned vertically or horizontally, the beam-limiting device must also be able to be turned so that the dimensions of the beam match the image receptor dimensions at the image receptor plane.

(b) Intra-oral radiography systems used to perform cephalometric projections, including trans-cranial exams, must be equipped with a stable means to:

(i) Set the source-to-skin distance;

(ii) Comply with the beam size dimensions in subsection (1)(a) of this section; and

(iii) Center the beam to the image receptor as required in subsection (1)(a) of this section.

(c) General purpose medical X-ray equipment used to perform cephalometric exams must:

(i) Have stepless adjustment of the dimensions of the X-ray beam so that the width and height of the X-ray beam are independently adjustable. The minimum beam size at a SID of 100 centimeters must be equal to or less than 10 by 10 centimeters.

(ii) Have a means for operators to visually set the width and height of the X-ray beam. The misalignment of the edges of the visually set light field with the respective edges of the X-ray beam along either the length or width of the visually set light field must not be more than two percent of the distance from the source to the center of the visually defined light field when the surface upon which it appears is perpendicular (at a 90 degree angle) to the central axis of the X-ray beam.

(iii) Have a way to indicate on the X-ray equipment when the axis of the X-ray beam is perpendicular to the plane of the image receptor and to align the center of the X-ray beam to the center of the image receptor to within two percent of the SID (five percent for equipment manufactured before August 1974). Dental lateral jaw examinations are excluded from this requirement.

(iv) Have a beam-limiting device that shows the X-ray beam size in centimeters or inches at the plane of the image receptor to which the beam-limiting device is adjusted.

(v) Have beam size dimension settings that are able to produce X-ray beam dimensions at the plane of the image receptor to within two percent of the SID when the beam axis is perpendicular to the plane of the image receptor.

(vi) Have SID displayed in inches and/or centimeters.

(2) Source-to-skin distance.

(a) Dental extra-oral radiography systems must have a durable, securely fastened means to limit the source-to-skin distance to not less than 23 centimeters. The requirement may be met when the beam-limiting device provides the required limits.

(b) Dental extra-oral radiography systems in which the SID is not fixed must have a device or reference that will indicate the actual SID distance to within two percent of the indicated SID.

(3) Viewing device.

Dental extra-oral radiography installations must provide a viewing device (mirror or glass window or video designed to reduce exposure) so that operators of the X-ray equipment may observe the patient during the exposure without being exposed to the primary beam or stray radiation.

(4) Scattered radiation suppressing grids.

When using scattered radiation suppressing grids, the grids shall be:

(a) Clearly labeled with the SID for which the grids are designed to be used; and

(b) Used at the proper SID.


WAC 246-225A-080   Special requirements for dental intra-oral radiography.   (1) Registrants using an X-ray system designed for use with an intra-oral image receptor shall use equipment that:

(a) Limits the source-to-skin distance to not less than 18 centimeters;

(b) Limits the X-ray beam so that the beam diameter at the minimum SSD is no greater than 7 centimeters in diameter;

(c) Has an open-ended position-indicating device; and

(d) Has shielding included in the beam-limiting device or position-indicating device equivalent to that required for the diagnostic source assembly under WAC 246-225A-060(1).

(2) After January 1, 2009, registrants shall not use diagnostic dental X-ray systems with a fixed, nominal kilovolts peak of less than 55.


WAC 246-225A-090   X-ray image processing requirements.   Standards in this section are designed to assure that optimal X-ray image quality and diagnostic information are produced so that fewer retakes are needed, and associated patient and operator exposure are minimal.

(1) When performing manual film processing, also known as hand tank processing, registrants or an operator working under the registrant's direction shall:

(a) Use appropriate chemicals for manual film processing as indicated in chemical and film manufacturer's labels and recommendations.

(b) Mix chemicals in accordance with the chemical manufacturer's recommendations.

(c) Periodically add film developer/fixer replenisher based on the recommendations of the chemical or film manufacturer. Solution may be removed from the tank to permit the addition of an adequate volume of replenisher.

(d) Completely replace all manual processing chemicals at least every two months, or follow the manufacturer's recommendations for periodic chemistry replenishment and maintenance, whichever is shorter.

(e) Post and keep the most recent twelve months of a log that shows when each chemistry change was done and by whom for department inspection.

(f) Process film to achieve the best image quality by either:

(i) Following the film manufacturer's published temperature and time recommendations for X-ray film development; or

(ii) Developing film according to the temperature-time chart in (g) of this subsection.

(g) For standard developer solution, follow the X-ray film developing time specified for the appropriate developer solution temperature in Table 1 of this section:

Table 1

27 80 2
79 2
78 2 1/2
77 2 1/2
24 76 3
75 3
74 3 1/2
73 3 1/2
22 72 4
71 4
70 4 1/2
69 4 1/2
20 68 5
67 5 1/2
66 5 1/2
65 6
18 64 6 1/2
63 7
62 8
61 8 1/2
16 60 9 1/2

(h) Use X-ray film developing devices that give:

(i) The actual temperature of the developer solution;

(ii) The developing time in minutes and seconds; and

(iii) An audible or visible signal when developing is complete.

(2) When performing automatic film processing, registrants or an operator working under the registrant's direction shall:

(a) Set up and maintain automatic film processors so that X-ray image density and contrast are optimal;

(b) Follow the film manufacturer's published specifications for time and temperature, and the processor manufacturer's recommendations for type of developer chemistry used. If manufacturer's specifications are not available, the film must be developed using the developer temperatures and immersion times specified in Table 2 of this section:

Table 2


C F Seconds
35 95 20
34.5 94 21
34 93 22
33.5 92 23
33 91 24
32 90 25
31.5 89 26
31 88 27
30.5 87 28
30 86 29
29.5 85 30
* Immersion time only, no cross-over time included.

(c) Replenish the developer chemistry to create optimal X-ray images by:

(i) Replacing all automatic processor chemicals at least every month, or follow the manufacturer's recommendations for periodic chemistry replenishment and maintenance, whichever is shorter.

(ii) Posting and maintaining a log that shows when each chemistry change was performed and by whom. The most recent twelve months of the log shall be kept for department inspection.

(iii) Verifying that the processor delivers an adequate rate of developer replenishment; and

(iv) Verifying that standby replenishment, flood replenishment, or prefixed film processing is done periodically as necessary for facilities with a low X-ray workload.

(3) When developing film, registrants or an operator working under the registrant's direction shall:

(a) Set up darkrooms and daylight film loaders so that film being processed, handled, or stored will be exposed only to light passed through a safelight filter. The filter must be of the type specified by the film manufacturer and must not cause excess fog (evidence of light exposure) on X-ray-exposed film. Fog greater than 0.1 optical density is considered unacceptable.

(b) Use bulbs in the darkroom's safelight of fifteen watts or less.

(c) Mount the safelight in the darkroom at least four feet (1.2 meters) above work areas.

(d) Use daylight loaders in darkened areas or where light is dimmed so that the fog standard in (a) of this subsection is met.

(4) When processing digital images, registrants or an operator working under the registrant's direction shall:

(a) Follow the computed radiography (CR) and direct digital radiography (DR) sensor or detector manufacturer's recommendations to achieve adequate diagnostic image quality for the least possible patient exposure.

(b) Process CR phosphor plates using the longest processing time recommended by the manufacturer of the plate processor.

(5) The department may make X-ray film development and darkroom tests as necessary to determine compliance with this section.


WAC 246-225A-110   Image processing quality assurance.   Beginning January 1, 2009, registrants making images on film shall comply with the following quality assurance requirements for X-ray image processing:

(1) Conduct an acceptable quality assurance program that includes weekly tests of manual and automatic film processing to include:

(a) Density and contrast on test films; and

(b) Action taken when test film density or contrast falls below 15 percent of initial reference levels.

(2) Keep a written or computer log of all periodic quality assurance testing covered in subsection (1) of this section, including test films, from the proceeding twelve months for inspection by the department.


Washington State Code Reviser's Office