Medical Devices; Performance Standard for Diagnostic X-Ray Systems; Amendment

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Food and Drug Administration

21 CFR Part 1020

[Docket No. 98N-0877]

Medical Devices; Performance Standard for Diagnostic X-Ray

Systems; Amendment

AGENCY: Food and Drug Administration, HHS.

ACTION: Final rule.

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SUMMARY: The Food and Drug Administration (FDA) is issuing a final rule

that amends the diagnostic x-ray systems performance standard for

dental panoramic systems and mammography systems. This rule exempts

panoramic dental x-ray units from the requirement that they be

manufactured with exposure timers that automatically reset to zero upon

premature termination of an exposure. Removing the automatic timer

reset requirement will not compromise the quality of the radiographic

image and will protect patients from being subject to unnecessary

radiation due to repeat radiographs. This action also is intended to

align the performance standard for mammography systems with the

equipment requirements issued under the Mammography Quality Standards

Act of 1992 (the MQSA).

EFFECTIVE DATE: September 30, 1999.

FOR FURTHER INFORMATION CONTACT: Richard V. Kaczmarek, Center for

Devices and Radiological Health (HFZ-240), Food and Drug

Administration, 1350 Piccard Dr., Rockville, MD 20850, 301-594-0865.

SUPPLEMENTARY INFORMATION:

I. Background

A. Panoramic Dental Radiograph

The requirements in Sec. 1020.31 (21 CFR 1020.31) apply to

diagnostic x-ray systems, including those used for dental radiography

and mammography. Based on information from manufacturers, FDA had

determined that the timer requirement in Sec. 1020.31(a)(2)(i) should

not apply to panoramic dental units. As a result of that determination,

FDA exercised its enforcement discretion and did not apply the timer

requirement to panoramic dental units. Some States had adopted local

standards that were identical in language to FDA's regulation, but did

not exempt panoramic dental units from the timer requirement because

those units were not expressly exempted in the Federal regulation.

Those States were applying the timer requirement to dental panoramic

units. To correct this inconsistency, FDA has amended the regulations

to expressly exempt panoramic dental units from the timer requirement

in Sec. 1020.31(a)(2)(i). This change should lead to consistency among

government requirements.

B. Mammography X-Ray Devices

The recent passage of the MQSA (Pub. L. 102-539) and issuance of

the interim and final MQSA regulations have focussed attention on the

mammography equipment requirements contained in 21 CFR part 1020.

Although the MQSA is directed to facility requirements for maintaining

mammography quality, both the interim and the final MQSA regulations

address x-ray equipment that is also subject to the performance

standard for diagnostic x-ray systems (58 FR 67558 and 58 FR 67565,

December 21, 1993; and 62 FR 55976, October 28, 1997). The MQSA and

FDA's regulations governing mammography establish quality standards for

facilities performing mammography to ensure safe, reliable, and

accurate mammography nationwide. FDA wanted to ensure that the

standards applying to radiation emitting electronic products, including

mammography equipment, and those applying to the facilities that use

such equipment were in accord. To bring the standards into harmony, FDA

has amended its performance standard for diagnostic x-ray systems.

The MQSA standards also address the proper viewing of mammography

films. The standard practice is that these films be read on view boxes

(light boxes) with the ambient room light levels reduced. Unexposed

film areas and parts of the light box not covered by exposed film

should be masked to prevent the bright light surrounding the radiograph

from interfering with reading the film.

Extending the x-ray field to expose the borders of the film

simplifies the work of the radiologist and accreditation bodies because

they have to create only one mask size, rather than having to create

individualized masks for each facility. With the current practice being

to irradiate the same area of the same sized film for all patients,

there is little evidence that allowing the x-ray field to completely

darken the film will significantly raise the radiation safety risk to

the patient. FDA has amended the diagnostic x-ray systems standard to

allow fixed aperture and variable aperture beam-limiting device (BLD)

systems, to open up or adjust the field size to cover the entire film

and thus reduce the need to provide a different mask for each film. In

certain instances, limiting the x-ray field to the size of the breast

may be considered to be advantageous. Practitioners still retain this

option, which may result in improved imaging quality due to the

reduction of scattered radiation.

To reduce unnecessary radiation exposure to the patient beyond the

plane of the image receptor, FDA has requirements for x-ray field

limitation and alignment. In the past, all systems in use for

mammography had fixed aperture plates for x-ray field limitation. The

advent of the variable aperture BLD for mammography is potentially a

problem with respect to the primary barrier requirement if a BLD is

opened so that the useful beam extends beyond the primary barrier

provided by the image receptor support device. To prevent this problem,

a variable aperture BLD must provide some restriction on the maximum

field size to ensure that the entire useful beam at the plane of the

image receptor is contained within the image receptor support device,

which is also a primary barrier. In other words, for a fixed aperture

or a variable aperture BLD with the collimator opened as wide as

possible, the entire useful beam should not extend beyond the barrier,

at any available source-image receptor distance (SID), except at the

chest wall side, and the exposure level 5 centimeters beyond this

barrier should not exceed 2.58X10-8 coulombs per kilogram

(C/k) (0.1 milliroentgen (mR)) per exposure. This requirement is in

agreement with the International Electrotechnical Commission (IEC)

draft standard for mammography systems (IEC 62B/60601-2-45).

II. The Final Rule

FDA believes that the final rule establishes reasonable

requirements that can be implemented by the regulated industry without

unnecessary burden. None of the comments on the proposed rule requested

that FDA revise any of the changes proposed.

A. Panoramic Dental Radiograph

The final rule exempts panoramic dental x-ray units from the

requirement in Sec. 1020.31(a)(2)(i) that they be

[[Page 35925]]

manufactured with exposure timers that automatically reset to zero upon

premature termination of an exposure. This change incorporates into

regulation current FDA policy and should lead to consistency among

Federal, State, and local requirements.

B. Mammography X-Ray Devices

The MQSA requires that only x-ray equipment specifically designed

for mammography can be used for mammography. Therefore, FDA has removed

the reference in Sec. 1020.31(f)(3), which allowed the use of general

purpose x-ray equipment with special attachments for mammography. This

change harmonizes this regulation with the MQSA equipment requirements.

Section 1020.31 permits the x-ray irradiation field at the plane of

the image receptor to extend to the edges of the x-ray film. However,

to protect the patient from unnecessary exposure to radiation, the

mammographic field alignment requirement restricts the irradiation beam

from extending beyond the edge of the receptor by no more than 2

percent of the SID. The limit on x-ray transmission through the primary

barrier (except on the chest wall edge) remains unchanged. FDA has

added the words ``for transmission'' to Sec. 1020.31(m)(4) to further

clarify the section.

The definition for ``image receptor support device'' replaces the

definition of ``image receptor support'' and clarifies that image

receptor support devices must provide a primary protective barrier for

any orientation of the x-ray tube and the image receptor support device

(except the chest wall side). This revision maintains the requirement

in the current Sec. 1020.31(m) that the image receptor support device

must serve to provide a primary protective barrier that intercepts the

useful beam. Equipment manufactured prior to the effective date of this

rule has always been, and will continue to be, subject to the

requirement that the primary barrier must intercept the useful beam.

Unlike fixed aperture systems, which meet the established primary

barrier requirement, with variable aperture collimation there is the

possibility that the dimensions of the x-ray beam may be adjusted to

exceed the area of the image receptor. This requirement confines the x-

ray beam to the dimensions of the primary barrier provided by the image

receptor support device, except on the chest wall side.

FDA has clarified the requirement that patient exposures not be

permitted without an appropriate primary barrier in place, by stating

the requirement explicitly. FDA further clarifies the requirement by

adding the word appropriate prior to primary barrier. FDA wants to

clarify that it is not appropriate for a mammographic x-ray system to

generate x-rays with an inappropriate image receptor support device in

place. To reduce radiation exposure to the patient, the rule provides

that the image receptor support device, acting as the primary barrier,

must be in place before a mammographic x-ray system can generate x-

rays. This requirement requires the image receptor support device be

interlocked with the system so that an exposure cannot be made with the

image receptor support device removed.

C. Effective Date

This rule will be effective in 90 days. Usually, amendments to

performance standards for electronic products become effective 1 year

after the date of publication of the final rule to allow sufficient

time for manufacturers to implement the changes in design or production

practices (21 U.S.C. 360kk(c)). In the proposed rule, FDA explained its

good cause basis for proposing a shorter timeframe, namely that the

amendments were codifying current industry practice, making regulatory

requirements consistent, or relaxing requirements, and requested

comments on the proposed shortening of the timeframe. No comments were

received. Consequently, this rule becomes effective September 30, 1999.

III. The Proposed Rule

In the Federal Register of October 29, 1998 (63 FR 57957), FDA

published a proposed rule to amend the performance standard for

diagnostic x-ray systems (dental and mammographic systems

requirements). The proposed rule contained the reasons for the proposed

amendment, summarized the Technical Electronic Product Radiation Safety

Standards Committee's recommendation regarding dental and mammographic

systems, and delineated the statutory authority under which FDA issues

this rule. The proposed rule also stated FDA's grounds showing good

cause for prescribing an earlier effective date than 1 year after the

date of publication of the final rule for these amendments to the

performance standard and solicited specific comment on the timeframe

for implementation of the final rule. Written comments were due January

27, 1999.

FDA received three comments, one each from a manufacturer, a

professional society, and a State agency. All three comments supported

the actions proposed in the rule. None of the comments commented on the

timeframe for implementation of the final rule.

IV. Response to Comments

All three comments supported the actions proposed in the rule. One

of the comments requested clarification concerning Sec. 1020.31(m)(2),

which would require that the x-ray tube shall not permit exposure

unless the barrier is in place to intercept the useful beam. The

concern was whether the manufacturer would be held responsible if an

individual equipment owner chose to partially dismantle the system or

bypass interlocks so that the x-ray tube could be operated with the

primary barrier removed. The comment stated that such action would

violate Sec. 1020.30(q)(2), which prohibits the owner of the equipment

from modifying the equipment such that it would no longer comply with

Sec. 1020.31. In such a case, the comment argued that FDA should cite

the owner, not the manufacturer, for noncompliance.

FDA agrees that a manufacturer should not be held responsible

should an owner circumvent the interlocks to operate the system with

the primary barrier removed. The regulation does not require the

manufacturer to design an interlock that cannot be defeated. A

modification by the owner that makes the unit noncompliant with

Secs. 1020.31(m)(2) and 1020.30(q) may cause the device to be

misbranded and adulterated. FDA could bring an action against the

person who caused the misbranding and adulteration and also seek to

enjoin use of the device.

None of the comments include any recommendations on the timeframe

for implementation of the final rule or suggest that FDA does not have

good cause for shortening the customary 1-year period. FDA believes

that unneeded delay in the implementation of these amendments could

lead to difficulties for mammography facilities because of confusion

over the requirements of the x-ray performance standard and standards

issued under the MQSA. In addition, because the amendments clarify a

provision of the Federal standard, FDA believes it is in the best

interests of patients, facilities, and manufacturers to implement the

dental x-ray equipment amendment expeditiously. For these reasons, the

effective date of the final rule will be 90 days after date of

publication in the Federal Register.

V. Environmental Impact

The agency has determined under 21 CFR 25.30(a) and (i) and

25.34(c) that

[[Page 35926]]

this action is of a type that does not individually or cumulatively

have a significant effect on the human environment. Therefore, neither

an environmental assessment nor an environmental impact statement is

required.

VI. Analysis of Impacts

FDA has examined the impact of this final rule under Executive

Order 12866 and the Regulatory Flexibility Act (5 U.S.C. 601-612) (as

amended by subtitle D of the Small Business Regulatory Fairness Act of

1996 (Pub. L. 104-121)), and the Unfunded Mandates Reform Act of 1995

(Pub. L. 104-4). Executive Order 12866 directs agencies to assess all

costs and benefits of available regulatory alternatives and, when

regulation is necessary, to select regulatory approaches that maximize

net benefits (including potential economic, environmental, public

health and safety, and other advantages; distributive impacts; and

equity). The agency believes this final rule is consistent with the

regulatory philosophy and principles identified in the Executive Order.

In addition, the final rule is not a significant regulatory action as

defined by the Executive Order and therefore is not subject to review

under the Executive Order.

The Regulatory Flexibility Act requires agencies to analyze

regulatory options that would minimize any significant impact of a rule

on small entities. Because this final rule increases the flexibility of

the performance standard and codifies current interpretations of

Federal regulations in order to prevent inconsistent interpretations by

State and local governments, and because none of the domestic

manufacturers of panoramic dental units or mammography x-ray systems

would be considered small entities, the agency certifies that the final

rule will not have a significant economic impact on a substantial

number of small entities engaged in manufacturing. Because dental and

mammography facilities will buy machines with the changes to the

performance standard allowed in this final rule only if it is

economically advantageous to do so, the agency certifies that the final

rule will not have a significant economic impact on a substantial

number of small entities that are facilities (most, if not all, of

which would be considered small entities). Therefore, under the

Regulatory Flexibility Act, no further analysis is required.

In the proposed rule, FDA conducted and published an initial

regulatory flexibility analysis to ensure that impacts on small

entities were assessed and to alert any potentially impacted entities

to the opportunity to submit comments to this agency. No comments on

the initial regulatory flexibility analysis were submitted. This final

rule will not impose costs of $100 million or more in either the

private sector or State, local, and tribal governments in the

aggregate. Consequently, a summary statement of analysis under section

202(a) of the Unfunded Mandates Reform Act of 1995 is not required.

In part, the final rule codifies the equipment performance

standards established under the MQSA by requiring only x-ray systems

designed specifically for mammography be marketed for mammography. This

rule updates the x-ray performance standard to reflect a standard

already enforced under the MQSA. Consequently, FDA expects no economic

impact from this portion of the final rule.

The final rule also permits the x-ray irradiation field to extend

to the edges of the x-ray film but not beyond the primary barrier

provided by the image receptor support device. It further changes the

definition of an image receptor support device, clarifying that it must

provide a primary protective barrier and that exposures not be possible

without the image receptor support device being in place, acting as the

primary barrier. Exposing all of the film allows one size of film mask

to be used for proper viewing of mammography films using light boxes

and prohibiting extension of the beam beyond the primary barrier

protects the patient from unnecessary exposure to radiation. The

amendment to relax the field edge alignment criteria will not require

any changes to x-ray mammography systems that are currently compliant;

these systems will remain compliant after the effective date. The

amendment will, however, allow the user to modify or purchase a

collimator that has the ability to provide films without light borders

as a convenience in simplifying viewing conditions. FDA believes that

most of the image receptor support devices that are currently in use

meet the requirements in the amendments to Secs. 1020.30(b) and

1020.31(m). In addition, when the manufacturer's design of the cassette

holder provides the primary barrier attenuation itself, then the

cassette holder is considered a part of the image receptor support

device. Therefore, FDA estimates that the amendments to

Secs. 1020.30(b) and 1020.31(m) will impose minimal new costs. This

rule also allows more flexibility for mammography facilities and

accreditation bodies without compromising the public health and may

reduce costs to mammography facilities and accreditation bodies by

simplifying the masking of images.

The final rule exempts panoramic x-ray dental units from the

requirement that they be manufactured with exposure timers that

automatically reset to zero or the initial setting upon premature

termination of an exposure. For panoramic dental exposures,

interrupting the exposure does not affect the quality of images already

taken. Consequently, restarting the exposure at the initial starting

point exposes patients to unnecessary radiation. This rule removes a

regulatory requirement, while still protecting the public health, and

may reduce costs to dental facilities and patients. FDA has identified

no new reporting, recordkeeping, or other compliance requirements

associated with this rule.

The Safe Medical Devices Act of 1990 (Pub. L. 101-629) enacted on

November 28, 1990, transferred the provisions of the Radiation Control

for Health and Safety Act of 1968 (Pub. L. 90-602) from Title III of

the Public Health Service Act (42 U.S.C. 201 et seq.) to Chapter V of

the Federal Food, Drug, and Cosmetic Act (21 U.S.C. 201 et seq.). These

provisions regulate electronic products that emit radiation. On October

27, 1992, the MQSA was enacted to establish uniform, national quality

standards for mammography. The MQSA (42 U.S.C. 263b(f)(1)(B)) requires

the use of radiological equipment specifically designed for mammography

to be used for mammography. Similarly, 21 CFR 900.12(b)(1) of the

interim and final mammography regulations prohibits the use of

conventional radiographic equipment for mammography.

There are approximately 10,000 mammography facilities in the United

States. Because this change in the performance standard only applies to

components manufactured after the effective date of the final rule, the

associated cost does not apply to those machines manufactured prior to

that date. FDA estimates that approximately 10 percent of facilities

replace their mammography machines in any one year. At this time, FDA

is unable to estimate the demand for the modifications to systems

currently in use. As discussed previously, the change concerning x-ray

beam collimation is less restrictive than the present standard. FDA

estimates the cost per system to be between $0 and $5,000, if the

system modification is made during production.

There are approximately 138,500 dental facilities in the United

States of

[[Page 35927]]

which 40 percent provide access to panoramic dental x-ray units. An

uncertain number of these facilities may request the manufacturer to

remove the automatic reset of the exposure timer on their panoramic

machines; however, they are not required to do so. FDA believes that

the facility will only make this change if it is economically or

clinically advantageous to do so. FDA estimates it will cost a facility

an amount equal to what would be assessed for a routine service call

(approximately $150.00 or less) to remove the automatic reset function

for premature termination of an exposure for existing systems. FDA

believes that manufacturers no longer manufacture panoramic dental x-

ray units with automatic reset exposure times.

Most, if not all, of the mammography facilities and dental

facilities would be considered small under the criteria establishment

by the Small Business Administration. FDA's registration system shows

five manufacturers of panoramic dental units. Of the domestic

manufacturers, none would be considered small entities. There are

approximately 10 manufacturers of mammography x-ray systems. Of these

manufacturers, none would be considered small entities.

For the mandatory changes to image receptor support devices, FDA

believes that most of the image receptor support devices that are

currently in use provide a primary barrier that is capable of meeting

the requirements in the amendments to Secs. 1020.30(b) and 1020.31(m).

There are approximately 10,000 mammography facilities in the United

States. Because this change in the performance standard only applies to

systems manufactured after the effective date of a final rule, the

costs associated with any changes that may need to be made, would not

apply to those machines manufactured prior to that date. FDA estimates

that approximately 10 percent of facilities replace their mammography

systems in any one year (10 percent of 10,000 = 1,000). FDA estimates

the cost per system to be between $0 and $2,000 in the event that any

manufacturers are required to implement design or production changes to

ensure that exposures not be permitted on their systems without a

primary barrier being in place. FDA estimates approximately 95 percent

of systems currently being marketed already meet this requirement. With

an annual mammography system replacement rate of 10 percent (i.e.,

1,000 new systems purchased per year), FDA estimates only approximately

5 percent of these 1,000 systems may increase the cost to meet the

requirement. To calculate the annual cost, FDA estimates a cost of $0

to $2,000 per system multiplied by 50 systems (5 percent of 1,000 =

50). Using this estimate, the costs are expected to be approximately $0

to $100,000.

Under these changes to the performance standard, FDA allows

manufacturers and facilities to decide whether to implement any device

modifications in response to the greater flexibility in these

mammography collimation requirements. If the benefits associated with

the flexibility in this rulemaking are outweighed by the costs to the

facility, the facility can choose to not purchase a device that has

been modified in response to the greater flexibility in this

rulemaking. With regard to the mandatory change, FDA believes that the

great majority of the image receptor support devices that are currently

being manufactured provide a primary barrier that is capable of meeting

the requirements in the amendment to Sec. 1020.31(m). Therefore, FDA

does not anticipate that the amendment to Sec. 1020.31(m) will impose

any significant costs.

Because most of these changes to the mammography performance

standard and the change to the timer requirement for panoramic dental

systems do not increase regulatory burdens, FDA considered no

alternatives to accomplish the stated objectives of the applicable

statutes. For the primary barrier standard in Sec. 1020.31(m), FDA

considered not requiring the primary barrier to be in place to

intercept the useful beam. This alternative was rejected because

without the primary barrier in place, patients would be exposed to

unnecessary radiation.

VII. Paperwork Reduction Act of 1995

This final rule contains no collections of information. Therefore,

clearance by the Office of Management and Budget under the Paperwork

Reduction Act of 1995 is not required.

List of Subjects in 21 CFR Part 1020

Electronic products, Medical devices, Radiation protection,

Reporting and recordkeeping requirements, Television, X-rays.

Therefore, under the Federal Food, Drug, and Cosmetic Act and under

authority delegated to the Commissioner of Food and Drugs, 21 CFR part

1020 is amended as follows:

PART 1020--PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING

PRODUCTS

1. The authority citation for 21 CFR part 1020 continues to read as

follows:

Authority: 21 U.S.C. 351, 352, 360e-360j, 360gg-360ss, 371, 381.

2. Section 1020.30 is amended in paragraph (b) by removing the

definition of ``image receptor support'' and adding a new definition in

alphabetical order to read as follows:

Sec. 1020.30 Diagnostic x-ray systems and their major components.

* * * * *

(b) * * *

Image receptor support device means, for mammography x-ray systems,

that part of the system designed to support the image receptor during a

mammographic examination and to provide a primary protective barrier.

* * * * *

3. Section 1020.31 is amended by revising paragraphs (a)(2)(i),

(f)(3), and (m) to read as follows:

Sec. 1020.31 Radiographic equipment.

* * * * *

(a) * * *

(2) * * *

(i) Except during serial radiography, the operator shall be able to

terminate the exposure at any time during an exposure of greater than

one-half second. Except during panoramic dental radiography,

termination of exposure shall cause automatic resetting of the timer to

its initial setting or to zero. It shall not be possible to make an

exposure when the timer is set to a zero or off position if either

position is provided.

* * * * *

(f) * * *

(3) Systems designed for mammography. (i) Mammographic beam-

limiting devices manufactured after September 30, 1999, shall be

provided with means to limit the useful beam such that the x-ray field

at the plane of the image receptor does not extend beyond any edge of

the image receptor by more than 2 percent of the SID. This requirement

can be met with a system that performs as prescribed in paragraphs

(f)(4)(i), (f)(4)(ii), and (f)(4)(iii) of this section. For systems

that allow changes in the SID, the SID indication specified in

paragraphs (f)(4)(ii) and (f)(4)(iii) of this section shall be the

maximum SID for which the beam-limiting device or aperture is designed.

(ii) Each image receptor support device intended for installation

on a system designed for mammography shall have clear and permanent

markings to indicate the maximum image receptor size for which it is

designed.

* * * * *

[[Page 35928]]

(m) Primary protective barrier for mammography x-ray systems. For

mammography x-ray systems manufactured after September 30, 1999:

(1) At any SID where exposures can be made, the image receptor

support device shall provide a primary protective barrier that

intercepts the cross section of the useful beam along every direction

except at the chest wall edge.

(2) The x-ray tube shall not permit exposure unless the appropriate

barrier is in place to intercept the useful beam as required in

paragraph (m)(1) of this section.

(3) The transmission of the useful beam through the primary

protective barrier shall be limited such that the exposure 5

centimeters from any accessible surface beyond the plane of the primary

protective barrier does not exceed 2.58X10-8 C/kg (0.1 mR)

for each activation of the tube.

(4) Compliance for transmission shall be determined with the x-ray

system operated at the minimum SID for which it is designed, at the

maximum rated peak tube potential, at the maximum rated product of x-

ray tube current and exposure time (mAs) for the maximum rated peak

tube potential, and by measurements averaged over an area of 100 square

centimeters with no linear dimension greater than 20 centimeters. The

sensitive volume of the radiation measuring instrument shall not be

positioned beyond the edge of the primary protective barrier along the

chest wall side.

Dated: June 16, 1999.

Margaret M. Dotzel,

Acting Associate Commissioner for Policy Coordination.

[FR Doc. 99-16835 Filed 7-1-99; 8:45 am]

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