Electronic Products; Performance Standard for Diagnostic X-Ray Systems and Their Major Components, 33998-34042 [05-11480]

Agencies

• Food and Drug Administration
• DEPARTMENT OF HEALTH AND HUMAN SERVICES

[Federal Register Volume 70, Number 111 (Friday, June 10, 2005)]
[Rules and Regulations]
[Pages 33998-34042]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-11480]



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Part III





Department of Health and Human Services





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Food and Drug Administration



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21 CFR Part 1020



Electronic Products; Performance Standard for Diagnostic X-Ray Systems 
and Their Major Components; Final Rule

Federal Register / Vol. 70, No. 111 / Friday, June 10, 2005 / Rules 
and Regulations

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DEPARTMENT OF HEALTH AND HUMAN SERVICES

Food and Drug Administration

21 CFR Part 1020

[Docket No. 2001N-0275]
RIN 0910-AC34


Electronic Products; Performance Standard for Diagnostic X-Ray 
Systems and Their Major Components

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 
to amend the Federal performance standard for diagnostic x-ray systems 
and their major components (the performance standard). The agency is 
taking this action to update the performance standard to account for 
changes in technology and use of radiographic and fluoroscopic x-ray 
systems and to fully utilize the International System of Units to 
describe radiation-related quantities and their units when used in the 
performance standard. For clarity and ease of understanding, FDA is 
republishing the complete contents, as amended, of three sections of 
the performance standard regulations and is amending a fourth section 
without republishing it in its entirety. This action is being taken 
under the Federal Food, Drug, and Cosmetic Act (the act), as amended by 
the Safe Medical Devices Act of 1990 (SMDA).

DATES: This rule is effective June 10, 2006.

FOR FURTHER INFORMATION CONTACT: Thomas B. Shope, Center for Devices 
and Radiological Health (HFZ-140), Food and Drug Administration, 9200 
Corporate Blvd., Rockville, MD 20850, 301-443-3314, ext. 132.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background
II. Highlights of the Final Rule
III. Summary and Analysis of Comments and FDA's Responses
    A. General Comments
    B. Comments on Proposed Changes to Sec.  1020.30
    1. Definitions (Sec.  1020.30(b))
    2. Information to Be Provided to Users (Sec.  1020.30(h))
    3. Beam Quality--Increase in Minimum Half-Value Layer (Sec.  
1020.30(m))
    4. Aluminum Equivalent of Material Between Patient and Image 
Receptor (Sec.  1020.30(n))
    5. Modification of Certified Diagnostic X-Ray Components and 
Systems (Sec.  1020.30(q))
    C. Comments on Proposed Changes to Sec.  1020.31--Radiographic 
Equipment
    1. Field Limitation and Post Exposure Adjustment of Digital Image 
Size
    2. Policy Regarding Disabled Positive Beam Limitation Systems
    D. Comments on Proposed Changes to Sec.  1020.32--Fluoroscopic 
Equipment
    1. Testing for Attenuation By the Primary Protective Barrier
    2. Field Limitation for Fluoroscopic Systems
    3. Air Kerma Rates
    4. Minimum Source-Skin Distance
    5. Display of Cumulative Irradiation Time
    6. Audible Signal of Irradiation Time
    7. Last-Image-Hold (LIH) Feature
    8. Display of Values of Air Kerma Rate and Cumulative Air Kerma
IV. Additional Revisions of Applicability Statements and Other 
Corrections
V. Environmental Impact
VI. Paperwork Reduction Act of 1995
    A. Summary
    B. Estimate of Burden
VII. Analysis of Impacts
    A. Introduction
    B. Objective of the Rule
    C. Risk Assessment
    D. Constraints on the Impact Analysis
    E. Baseline Conditions
    F. The Amendments
    G. Benefits of the Amendments
    H. Estimation of Benefits
    I. Costs of Implementing the Regulation
    1. Costs Associated With Requirements Affecting Equipment Design
    2. Costs Associated With Additional Information for Users
    3. Costs Associated With Clarifications and Adaptations to New 
Technologies
    4. FDA Costs Associated With Compliance Activities
    5. Total Costs of the Regulation
    J. Cost-Effectiveness of the Regulation
    K. Small Business Impacts
    1. Description of Impact
    2. Analysis of Alternatives
    3. Ensuring Small Entity Participation in Rulemaking
    L. Reporting Requirements and Duplicate Rules
    M. Conclusion of the Analysis of Impacts
VIII. Federalism
IX. References

I. Background

    The SMDA (Public Law 101-629) transferred the provisions of the 
Radiation Control for Health and Safety Act of 1968 (RCHSA) (Public Law 
90-602) from title III of the Public Health Service Act (PHS Act) (42 
U.S.C. 201 et seq.) to chapter V of the act (21 U.S.C. 301 et seq.). 
Under the act, FDA administers an electronic product radiation control 
program to protect the public health and safety. As part of that 
program, FDA has authority to issue regulations prescribing radiation 
safety performance standards for electronic products, including 
diagnostic x-ray systems (sections 532 and 534 of the act (21 U.S.C. 
360ii(a) and 360kk)).
    The purpose of the performance standard for diagnostic x-ray 
systems is to improve the public health by reducing exposure to and the 
detriment associated with unnecessary ionizing radiation while assuring 
the clinical utility of the images produced.
    In order for mandatory performance standards to continue to provide 
the intended public health protection, the standards must be modified 
when appropriate to reflect the changes in technology and product 
usage. When the performance standard was originally developed, the only 
means of producing a fluoroscopic image was either a screen of 
fluorescent material or an x-ray image intensifier tube. Therefore, the 
standard was written with these two types of image receptors in mind. A 
number of technological developments have been implemented for 
radiographic and fluoroscopic x-ray systems, such as solid-state x-ray 
imaging (SSXI) and new modes of image recording (e.g., digital 
recording to computer memory or other media). These developments have 
made the application of the current standard to systems incorporating 
these new technologies cumbersome and awkward. FDA is therefore 
amending the performance standard for diagnostic x-ray systems and 
their major components in Sec. Sec.  1020.30, 1020.31, and 1020.32 (21 
CFR 1020.30, 1020.31, and 1020.32) to address the recent changes in 
technology. In addition, we are amending Sec.  1030.33(h) (21 CFR 
1030.33(h)) to reflect the change in the quantity used to describe 
radiation.
    These amendments will require that newly-manufactured x-ray systems 
include additional features that physicians may use to minimize x-ray 
exposures to patients. Advances in technology have made several of 
these new features feasible at minimal additional cost.
    In the Federal Register of August 15, 1972 (37 FR 16461), FDA 
issued a final rule for the performance standard, which became 
effective on August 1, 1974. Since then, FDA has made several 
amendments to the performance

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standard to incorporate new technology, to clarify misinterpreted 
provisions, or to incorporate additional requirements necessary to 
provide for adequate radiation safety of diagnostic x-ray systems. 
(See, e.g., amendments published on October 7, 1974 (39 FR 36008); 
February 25, 1977 (42 FR 10983); September 2, 1977 (42 FR 44230); 
November 8, 1977 (42 FR 58167); May 22, 1979 (44 FR 29653); August 24, 
1979 (44 FR 49667); November 30, 1979 (44 FR 68822); April 25, 1980 (45 
FR 27927); August 31, 1984 (49 FR 34698); May 3, 1993 (58 FR 26386); 
May 19, 1994 (59 FR 26402); and July 2, 1999 (64 FR 35924)).
    In the Federal Register of December 11, 1997 (62 FR 65235), FDA 
issued an advance notice of proposed rulemaking (ANPRM) requesting 
comments on the proposed conceptual changes to the performance 
standard. The agency received 12 comments from State and local 
radiation control agencies, manufacturers, and a manufacturer 
organization. FDA considered these comments in developing the proposed 
amendments. In addition, the concepts embodied in the amendments were 
discussed on April 8, 1997, during a public meeting of the Technical 
Electronic Product Radiation Safety Standards Committee (TEPRSSC). 
TEPRSSC is a statutory advisory committee that FDA is required to 
consult before the agency may prescribe any electronic product 
performance standard under the act (21 U.S.C. 360kk(f)(1)(A)). The 
proposed amendments themselves were discussed in detail with the 
TEPRSSC during a public meeting held on September 23 and 24, 1998. At 
that meeting, TEPRSSC approved the content of the proposed amendments 
and concurred with their publication for public comment.
    FDA proposed the amendments for public comment in the Federal 
Register of December 10, 2002 (67 FR 76056). Interested persons were 
given until April 9, 2003, to comment on the proposal. FDA received 
comments from 12 organizations and individuals in response to the 
proposed amendments. These comments were generally supportive of the 
proposed changes to the performance standard, although some expressed 
concern about specific aspects of some of the proposed amendments.

II. Highlights of the Final Rule

    In this final rule, FDA is making a number of changes to the 
performance standard for diagnostic x-ray systems and their components, 
including the following:
     In Sec.  1020.30 of the performance standard, the final 
rule makes the following changes:
    Adds a number of new definitions to address new technologies and to 
further clarify the regulations. One notable amendment to the 
definitions is the addition of the terms air kerma and kerma to reflect 
a change in the quantity used to describe radiation emissions from 
diagnostic x-ray systems (Sec.  1020.30(b));
    Requires manufacturers to provide users (e.g., physicians) with 
certain information regarding the new features of fluoroscopic systems 
in order to better protect their patients from unnecessary x-radiation 
exposure (Sec.  1020.30(h));
    Requires additional warning label language designed to alert users 
and facility administrators to the need to properly maintain and 
calibrate their diagnostic x-ray systems (Sec.  1020.30(j)); and
    Modifies existing beam quality requirements by increasing the 
required minimum half-value layer (HVL) values for radiographic and 
fluoroscopic equipment. This increase in HVL values will bring FDA 
requirements into agreement with the performance already provided by 
systems that are compliant with corresponding international standards. 
Therefore, manufacturers currently complying with the international 
standards should not be impacted by this change (Sec.  1020.30(m)).
     In Sec.  1020.31 of the performance standard, which 
addresses radiographic x-ray equipment, the following changes are being 
made:
    A number of minor, technical corrections to sections applicable to 
mammographic x-ray systems that were made necessary by an oversight 
that occurred when this performance standard was amended in July 1999 
(Sec.  1020.31(f)(3) and (m)).
     The provisions in Sec.  1020.32 pertain to fluoroscopic 
equipment. Key changes being made to this section of the performance 
standard include the following:
    Amending the x-ray field limitation and alignment requirements to 
promote the addition of features designed to reduce the amount of 
radiation falling outside the visible area of the image receptor, 
thereby preventing unnecessary patient exposure (Sec.  1020.32(b));
    Amending the requirement concerning maximum limits on entrance air 
kerma rates (AKR) in order to clarify the circumstances under which the 
maximum limits would apply (Sec.  1020.32(d) and (e));
    Establishing a minimum source-skin distance requirement for certain 
small ``C-arm'' type fluoroscopic systems. FDA traditionally has 
granted variances from minimum source-skin distance requirements for 
small, portable C-arm systems when such systems were intended only for 
the limited use of imaging extremities. The amendment establishes the 
conditions under which variances have been granted as part of the 
standard and removes the need for manufacturers to continue to request 
variances of this type and makes explicit the requirements for these 
systems (Sec.  1020.32(g));
    Requiring the incorporation of a feature that will continuously 
display the last fluoroscopic image taken prior to termination of 
exposure (last-image-hold feature). This permits the user to 
conveniently view fluoroscopic images without continuously irradiating 
the patient (Sec.  1020.32(j)); and
    Requiring the incorporation of a feature that will display critical 
information to the fluoroscopist regarding patient irradiation, 
including the duration, rate (AKR), and amount (cumulative air kerma) 
of exposure (Sec.  1020.32(k));
     Section 1020.33 addresses computed tomography (CT) 
equipment. With regard to CT systems, the final rule makes the 
following changes:
    Amends the requirements pertaining to beam-on and shutter status 
indicators to reflect the change in quantity used to describe x-
radiation from exposure to air kerma. This modification does not alter 
the level of radiation protection provided by the existing standard 
(Sec.  1020.33(h)).

III. Summary and Analysis of Comments and FDA's Responses

A. General Comments

    (Comment 1) FDA received 12 comments on the proposed amendments to 
the performance standard, many of which addressed multiple issues. In 
general tone and content all 12 individuals or organizations that 
commented supported the need for amendments and the approach proposed 
by FDA. A number of the comments provided suggestions or critiques 
regarding specific aspects of the proposed changes or suggested 
additional changes or additions for FDA consideration that were not 
part of the FDA proposal. The specific comments and FDA's responses 
will be discussed in the following paragraphs for each section of the 
performance standard.
    Seven of the comments provided general comments that did not 
address specific proposed changes. Some of

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them addressed the impact analysis or the estimate of the potential 
benefits that would likely result from the amendments. All seven 
comments were generally supportive of the changes proposed by FDA. Two 
comments suggested that the benefits of the proposed changes would be 
greater than estimated by FDA. One comment, from a State agency, 
suggested that the patient dose reductions would be greater than 
estimated by FDA, based on the State agency's experience with programs 
that have improved the information provided to facilities regarding 
patient radiation doses. Another comment suggested that the benefit of 
any dose reduction resulting from the amendments would greatly exceed 
FDA's estimates and criticized FDA for suggesting that the risk from x-
ray radiation is much less than the comment believes it to be. Two of 
the comments complimented FDA on its analysis of the potential impact 
of the regulation.
    (Response) We acknowledge and appreciate the supportive comments. 
This rule includes important modifications to the Federal performance 
standard for diagnostic x-ray systems to address recent changes in the 
technology and usage of radiographic and fluoroscopic x-ray systems. 
These modifications will help ensure that the performance standard will 
continue to protect and improve the public health by reducing exposure 
to unnecessary ionizing radiation while assuring the continued clinical 
utility of images produced where these new technologies are in use.
    (Comment 2) Two comments questioned the need to apply several of 
the requirements to all fluoroscopic x-ray systems, noting that the 
benefit of the requirements such as for display of dose information and 
a last-image-hold feature would largely result from fluoroscopic 
equipment used for interventional procedures. At least five other 
comments explicitly supported application of the requirements to all 
fluoroscopic systems.
    (Response) FDA notes that performance requirements must be tied to 
equipment characteristics and not to the potential manner in which the 
equipment may be used. Because interventional procedures may be 
performed using many types of fluoroscopic equipment, and because the 
added costs of the requirements are not expected to be overly 
burdensome, FDA has determined that the requirements should apply to 
all fluoroscopic equipment as proposed.
    (Comment 3) Two comments supported the change in the quantity 
proposed for the description of radiation in the standard from exposure 
to air kerma. One of these comments was fairly general, while the other 
expressed specific support for the approach taken in the proposal that 
will maintain all of the various limits on radiation contained in 
different requirements of the standard at the same effective level as 
in the limits in the current standard where they were expressed using 
the quantity roentgen.
    (Response) FDA believes that the radiation limits contained in the 
existing requirements remain appropriate. Although the change from 
exposure to air kerma will result in different numerical values that 
may no longer be integer numbers or multiples of 5 or 10 as was 
previously the case, the level of radiation protection will effectively 
be the same.
    (Comment 4) FDA received comments in response to questions posed by 
the agency in the preamble of the proposed rule. FDA invited comments 
on several questions regarding approaches that could be taken to assure 
the radiation safety of fluoroscopic systems through performance 
requirements. These questions, which were not associated with specific 
proposed amendments, were intended to gather information that might 
guide FDA in considering any future modifications to the performance 
standard. Among the questions FDA presented for comment was whether 
there are any clinical situations that could require entrance AKRs 
greater than those currently permitted. FDA also invited comment on 
whether limits should be established for the entrance AKR at the 
entrance surface of the fluoroscopic image receptor and, if so, how 
these limits might be determined and established.
    FDA received three comments in response to the questions about 
entrance air kerma rates. Two comments recommended that limits should 
not be established for the entrance air kerma rate at the entrance 
surface of the fluoroscopic image receptor. A third comment suggested 
that a mode of operation that would permit momentary imaging with 
entrance air kerma rates exceeding current limits should be considered 
if limits were to be established for the entrance air kerma rate at the 
entrance to the fluoroscopic image receptor. This comment also noted 
that any consideration of limits should involve the corresponding 
fluoroscopic image quality, and suggested that this is an area for 
further consideration by FDA in collaboration with interested parties. 
However, these comments did not make specific suggestions for 
requirements or provide data or evidence regarding such requirements.
    (Response) FDA appreciates these suggestions. Although FDA has 
decided not to implement them at this time, FDA will involve interested 
parties in discussions about such requirements if modifications such as 
these are undertaken in the future.
    (Comment 5) Two comments supported the need to modify the 
performance standard to address newly-evolving technologies. Although 
both comments agreed with FDA's proposed approach, they suggested that 
any future efforts to further address new technology with additional 
performance requirements, beyond the current proposed changes, would 
benefit from additional consultations between FDA and interested or 
affected parties. One of these comments suggested that consideration of 
further requirements to address additional characteristics of digital 
detectors or solid state x-ray imaging devices would benefit from 
interactive consultations with professional and scientific 
organizations. The other comment suggested that these areas could be 
addressed through the International Electrotechnical Commission's (IEC) 
standards development process.
    (Response) FDA agrees with these suggestions and will encourage and 
facilitate such discussions should the future development of additional 
amendments be undertaken.

B. Comments on Proposed Changes to Sec.  1020.30

1. Definitions (Sec.  1020.30(b))
    As discussed in the preamble to the proposed rule, FDA proposed the 
inclusion of a number of new definitions in Sec.  1020.30(b) to address 
new technologies and to further clarify the regulations. In addition to 
the changes to definitions proposed by FDA, a number of comments 
suggested modifications of additional, existing definitions or noted 
that new definitions were needed for clarity.
    (Comment 6) One comment suggested that the definitions in the 
standard be harmonized to the extent possible with those used by the 
IEC.
    (Response) FDA declines to make this change. The definitions in the 
U.S. standard were developed and finalized before the development of 
the IEC standards for x-ray equipment. Complete adoption of the IEC 
definitions would require FDA to overhaul the entire U.S. standard to 
bring it in line with the different structure and approach used in the 
IEC standards. In addition, the U.S. standard

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reflects differences in common usage. For example, the IEC standard 
uses the term ``radioscopy'' instead of the term ``fluoroscopy'' as 
commonly used in the United States. For these reasons, FDA does not 
believe that such wholesale revisions are warranted at this time.
    (Comment 7) FDA received a comment concerning the definition of 
attenuation block that noted that the current size specified is not 
large enough to accommodate the large x-ray field sizes used in 
conjunction with some current fluoroscopic image receptors that are 
significantly larger than earlier image receptors.
    (Response) In response to this comment, FDA has modified the 
definition to indicate that an attenuation block with dimensions larger 
than currently specified is allowed. The new definition reads:
    Attenuation block means a block or stack of type 1100 aluminum 
alloy or aluminum alloy having equivalent attenuation with 
dimensions 20 centimeters or larger by 20 centimeters or larger by 
3.8 centimeters. When used, the attenuation block shall be large 
enough to intercept the entire x-ray beam.
    (Comment 8) One comment suggested the need for clarification of 
what the term C-arm fluoroscope means as used in the standard.
    (Response) FDA agrees that clarification would be useful and has 
included a new definition for this term in the final rule. The new 
definition reads:
    C-arm fluoroscope means a fluoroscopic x-ray system in which the 
image receptor and x-ray tube housing assembly are connected or 
coordinated to maintain a spatial relationship. Such a system allows 
a change in the direction of the beam axis with respect to the 
patient without moving the patient.
 Note that this definition will include some systems in which the x-ray 
tube and the fluoroscopic imaging assembly are not connected by a C-
shaped mechanical connection. The distinguishing feature of a C-arm 
fluoroscope is the capability to change the orientation of the x-ray 
beam.
    (Comment 9) In the preamble to the proposed rule, FDA noted that 
the word ``exposure'' is used in the standard with two different 
meanings. One comment suggested adding the second meaning of exposure 
to the definition for clarity.
    (Response) FDA agrees with this comment. Accordingly, the 
definition of exposure is revised to read:
    Exposure (X) means the quotient of dQ by dm, where dQ is the 
absolute value of the total charge of the ions of one sign produced 
in air when all the electrons and positrons liberated or created by 
photons in air of mass dm are completely stopped in air; thus X=dQ/
dm, in units of C/kg. Exposure is also used with a second meaning to 
refer to the process or condition during which the x-ray tube 
produces x-ray radiation.
    (Comment 10) One comment suggested that the definition of image 
intensifier be modified to add a comparison to a simple fluorescent 
screen.
    (Response) FDA has concluded that such a change is not warranted. 
However, this comment prompted further review of the definition of 
fluoroscopy. As a result of this further review, FDA believes the 
proposed definition of fluoroscopy should be modified to remove the 
description that the images are presented instantaneously to the user. 
The word ``instantaneously'' is unnecessarily restrictive and 
ambiguous. It could result in confusion in certain situations such as 
when some short but finite time is required to process digital images 
before displaying them to the user. A further clarification has been 
added to note that, whereas ``fluoroscopy'' conforms to common usage in 
the United States, it has the same meaning as ``radioscopy'' in the IEC 
standards. Therefore, the definition of fluoroscopy is changed to read:
    Fluoroscopy means a technique for generating a sequence of x-ray 
images and presenting them simultaneously and continuously as 
visible images. This term has the same meaning as the term 
`radioscopy' in the standards of the International Electrotechnical 
Commission.
    (Comment 11) One comment suggested that FDA clarify the meaning of 
the term ``C-arm gantry'' as used in the proposed definition of 
isocenter.
    (Response) FDA agrees that clarification of this term would be 
useful and has revised the proposed definition of isocenter to read:
    Isocenter means the center of the smallest sphere through which 
the beam axis passes when the equipment moves through a full range 
of rotations about its common center.
    (Comment 12) Several comments suggested that FDA clarify the 
proposed definition of mode of operation.
    (Response) FDA agrees that clarification is needed and has modified 
this definition. Mode of operation is defined for the purpose of 
assuring that adequate instructions are provided to the user on how to 
operate the fluoroscopic system. A mode of operation is intended to 
describe the state of system operation in which a set of several 
technique factors or other control settings are selected to perform a 
specific type of imaging task or procedure. Within a specific mode of 
operation, a variety of anatomical or examination-specific technique 
selections may be provided, either pre-programmed, under automatic 
control, or manually-selected.
    (Comment 13) One comment suggested that the proposed definition of 
mode of operation would allow wide variations in AKR within a given 
mode of operation and that such variations would cause conflict with 
several items in Sec.  1020.30(h). The comment suggested that FDA 
consider using the definition and information requirements of the IEC 
standard IEC 60601-2-43, ``Particular Requirements for the Safety of X-
Ray Equipment for Interventional Radiology'' (Ref. 1).
    (Response) FDA disagrees that the proposed definition will conflict 
with items of information required by Sec.  1020.30(h). It is true that 
specification of a mode of operation does not in itself determine the 
AKR produced by the mode, as variations of technique factors or other 
controls within a given mode of operation can produce wide variations 
in the amount of radiation emitted by the system. Such variation, 
however, does not conflict with Sec.  1020.30(h). Proposed Sec.  
1020.30(h)(5) would require a description of each mode of operation, 
and Sec.  1020.30(h)(6) would require information about the AKR and 
cumulative air kerma displays. These sections do not require dose data 
for each mode in the information to be provided to users under Sec.  
1020.30(h). The IEC standard IEC 60601-2-43 does require providing 
certain dose information regarding some of the operating modes for 
fluoroscopic systems intended for interventional uses, but this IEC 
requirement would not conflict with the proposed changes to the 
performance standard.
    FDA notes that the definition it is adopting for ``mode of 
operation'' differs from the definition used in paragraph 2.107 of the 
IEC standard IEC 60601-2-43. The IEC standard defines a mode of 
operation for interventional x-ray equipment as ``* * * the technical 
state defined by a configuration of several predetermined loading 
factors, technique factors or other settings for radioscopy or 
radiography, selectable simultaneously by the operation of a single 
control.'' FDA does not think it necessary to limit a mode of operation 
to system operation selected by operation of a single control. The 
definition in this final rule includes methods of system operation that 
have specific or unique features or intended purposes about which the 
user should be informed in detail. The term mode of operation in this 
rule addresses only the information that must be provided to the user 
under Sec.  1020.30(h)(5), which requires that users receive complete 
instructions regarding the operation and intended function of each mode 
of operation.

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    FDA does not require information related to the reference AKR for 
modes of operation as does the IEC standard. FDA notes that the 
required display of AKR will directly inform users regarding actual 
entrance AKRs during use. FDA has determined that it is important that 
users receive complete descriptions in the user's manual of all the 
different modes of operation and their intended purposes or types of 
imaging procedures for which they are designed.
    The definition of mode of operation has therefore been modified to 
read:
    Mode of operation means, for fluoroscopic systems, a distinct 
method of fluoroscopy or radiography provided by the manufacturer 
and selected with a set of several technique factors or other 
control settings uniquely associated with the mode. The set of 
distinct technique factors and control settings for the mode may be 
selected by the operation of a single control. Examples of distinct 
modes of operation include normal fluoroscopy (analog or digital), 
high-level control fluoroscopy, cineradiography (analog or digital), 
digital subtraction angiography, electronic radiography using the 
fluoroscopic image receptor, and photospot recording. In a specific 
mode of operation, certain system variables affecting air kerma, 
AKR, or image quality, such as image magnification, x-ray field 
size, pulse rate, pulse duration, number of pulses, SID, or optical 
aperture, may be adjustable or may vary; their variation per se does 
not comprise a mode of operation different from the one that has 
been selected.
    (Comment 14) One comment suggested that FDA change the definition 
of a solid-state x-ray imaging device to make it less specific and 
therefore more likely to accommodate changes in technology.
    (Response) FDA agrees. The definition has been modified to read:
    Solid-state x-ray imaging device means an assembly, typically in 
a rectangular panel configuration, that intercepts x-ray photons and 
converts the photon energy into a modulated electronic signal 
representative of the x-ray image. The electronic signal is then 
used to create an image for display and/or storage.
    (Comment 15) One comment suggested that the existing definition of 
visible area needs clarification with respect to its use with solid-
state x-ray imaging devices. The comment suggested that the definition 
clarify that the visible area can include both active and inactive 
elements of the detector when inactive elements are within the outer 
borders of the overall area.
    (Response) FDA has determined that modification of this definition 
is not necessary. FDA notes that the ``area'' cited in this definition 
is the overall area defined by the external dimensions of the area over 
which photons are detected to form an image. It includes any inactive 
elements that might be located between active elements of the image 
receptor.
    (Comment 16) FDA also received comments suggesting changes to some 
of the existing definitions that were not proposed for modification in 
the proposed amendments, including the definitions for beam axis, 
cradle, pulsed mode, source-image receptor distance (SID), portable x-
ray equipment, and stationary x-ray equipment.
    (Response) FDA carefully reviewed the suggestions and has 
determined that no changes to these definitions are warranted at this 
time. However, as FDA reviewed the comments received regarding proposed 
changes to the definitions, it became apparent to the agency that 
several additional definitions would be useful to further clarify some 
of the terms used in the performance standard. Therefore, FDA has added 
new definitions for the terms air kerma rate, cumulative air kerma, and 
fluoroscopic irradiation time. These definitions are not intended to 
impose any new requirements.
    The new definitions read as follows:
     Air kerma rate (AKR) means the air kerma per unit time.
     Cumulative air kerma means the total air kerma accrued 
from the beginning of an examination or procedure and includes all 
contributions from fluoroscopic and radiographic irradiation.
     Fluoroscopic irradiation time means the cumulative 
duration during an examination or procedure of operator-applied 
continuous pressure to the device enabling x-ray tube activation in any 
fluoroscopic mode of operation.
2. Information to Be Provided to Users (Sec.  1020.30(h))
    (Comment 17) Three comments suggested an expansion of the scope of 
information required to be provided to users by manufacturers. These 
comments suggested that the manufacturer be required to provide: (1) A 
full set of system schematics to permit the user or a third party to 
troubleshoot electronic problems and perform repairs; (2) system-
specific hardware and software tools to permit a qualified individual 
to accomplish quality assurance tests without the need for service 
support; or (3) appropriate tools and instructions for their use, 
either as part of the system or as required accessories, to permit any 
``physics measurements'' needed to assure system performance.
    (Response) An expansion of existing information requirements was 
not contemplated in the proposed rule. Such requirements could have 
significant impact on manufacturers of diagnostic x-ray equipment and 
neither should be established without a full opportunity for affected 
parties to comment on specific proposals, nor should such requirements 
be established without a thorough assessment of the potential benefits 
and impacts of such requirements. Therefore, FDA is not incorporating 
the suggested requirements into the amendments at this time.
    (Comment 18) One comment supported the proposed requirement that 
manufacturers provide additional, detailed information regarding the 
variety of fluoroscopic system modes of operation. This comment 
suggested that manufacturers be required to provide data on the 
entrance AKR for each mode of operation and further suggested that such 
a requirement could be less costly than the proposed requirement for a 
display of air kerma information on fluoroscopic systems. The comment 
suggested that users could infer approximate patient doses from such 
information with a degree of accuracy comparable to that of the 
displayed air kerma information.
    (Response) FDA considered the approach described in this comment 
when developing the proposal and determined that providing the user 
with information on patient doses through data on typical entrance air 
kerma rates for each mode of operation was not practical and would not 
have the benefits associated with a real-time display of AKR and 
cumulative air kerma information. In FDA's opinion, either the entrance 
AKR is highly variable within a given mode of operation or there are so 
many different modes of operation, which would require separate AKR 
data, as to make this approach ineffective in informing physicians 
about the doses delivered to a patient in a procedure. For systems with 
a number of operating modes, it would be difficult for the user to 
remember all of the various entrance AKRs. The real-time display 
provides this information on a continuous basis for every patient, 
independent of the specific mode selected. For example, interventional 
procedures, with their associated long exposure times, may be 
undertaken on a variety of types of fluoroscopic systems. It does not 
appear feasible to distinguish the type of system that should have the 
real-time display from those for which such a display would not be 
useful.
    The real-time displays are anticipated to have dose-reduction 
benefits even in noninterventional procedures. Providing users with 
immediate information related to patient doses is expected to have an 
impact on use of

[[Page 34003]]

the equipment. In addition, the uncertainty in estimating an individual 
patient's specific radiation dose from a reference AKR provided for a 
mode of operation is expected, typically, to be much greater than the 
uncertainty in the real-time values displayed. This increased 
uncertainty is due to the wide variation in AKR possible within a given 
mode of operation because of variations in technique factors or other 
control factors, patient size and attenuation, and the specific beam 
orientations of an individual procedure.
    (Comment 19) One comment suggested that the current wording of 
Sec.  1020.30(h)(1)(i) be modified to emphasize that the adequate 
instructions required by the section be suitably written for physician 
operators.
    (Response) FDA does not believe that modification of the current 
wording is needed. The requirement for adequate instructions embodies 
the concept of being adequate for the intended audience. Since 
diagnostic x-ray systems are prescription devices, there is a presumed 
level of knowledge regarding the use of x-ray equipment on the part of 
the users.
    (Comment 20) A comment questioned the preamble statement regarding 
unique features of equipment that require adequate instructions 
regarding radiological safety procedures and the precautions needed 
because of these features. FDA noted that any mode of operation that 
yields an entrance AKR greater than 88 mGy/min should be considered a 
unique mode, and sufficient information should be provided to enable 
the user to understand the patient dose implications of using that 
mode. The comment questioned whether an 88 mGy/min threshold should be 
applied to radiographic modes and further suggested that there be a 
requirement that any fluoroscopic mode capable of delivering more than 
88 mGy/min be explicitly listed as a mode of operation and that 
standardized information regarding entrance AKR be provided for each 
such mode.
    (Response) FDA disagrees with this comment. As noted in the 
preamble of the proposed rule, data regarding the doses from specific 
modes of operation are not being required in the information for users. 
Rather, the newly-required AKR and cumulative air kerma displays will 
be relied on to provide users real-time information on air kerma at the 
reference location which can be related to patient dose. Values of the 
AKR and cumulative air kerma displayed in real-time do not necessitate 
adjustments for particular imaging technique factors or patient size as 
would standardized tabulations of AKR information printed as user 
information for each mode.
    (Comment 21) The same comment also suggested that manufacturers be 
required to provide standardized AKR data for fluoroscopic modes of 
operation as required in IEC standard IEC 60601-2-43, including 
information regarding the AKR for each available frame rate possible 
during the normal mode of operation.
    (Response) FDA did not accept this suggestion, which is also 
addressed in the discussion in the previous paragraphs about the 
definition of mode of operation. FDA notes that proposed Sec.  
1020.32(k) is being revised as described in the following paragraphs to 
clarify the conditions under which the display of AKR is required. 
Proposed Sec.  1020.30(h)(5) has been revised to require that 
information be provided to users for all modes of operation that 
produce images using the fluoroscopic image receptor regarding the 
impact of the mode selected on the resulting technique factors. This 
includes any mode that produces radiographic images from the 
fluoroscopic image receptor.
    (Comment 22) One comment suggested several changes to the 
performance standard that were not included in the proposed rule. These 
suggestions were that in several sections of the performance standard, 
where specification of the maximum kilovolts peak (kVp) or a specified 
kVp is stated, there should be a specification of the characteristics 
of the kV waveform. In particular, the comment suggested that a 
waveform having a voltage ripple of less than or equal to 10 percent be 
required. One of these sections is 1020.30(h)(2)(i), which requires the 
specification of the peak tube potential at which the aluminum 
equivalent of the minimum filtration in the beam is determined. The 
other is the requirement in Sec.  1020.30(m) for the kVp at which the 
minimum HVL values are determined. The comment addresses the 
requirement that manufacturers provide information regarding the peak 
tube potential at which the aluminum equivalent of the beam filtration 
provided by the tube housing assembly or permanently in the beam is 
determined. The comment points out the fact that the determination of 
the aluminum equivalent is also dependent on the voltage waveform as 
well as the peak tube potential.
    (Response) FDA will further consider this comment and if it 
determines that such a modification to the standard is warranted, a 
proposal will be published for public comment. Without specification of 
the waveform, uncertainty can be introduced into the specification of 
the aluminum equivalence of the filtration because this determination 
depends on the voltage waveform and the resulting energy spectrum of 
the beam. FDA notes that the IEC standard IEC 60601-1-3 (Ref. 2) that 
establishes the minimum HVL requirements for diagnostic x-ray systems 
does not specify the voltage waveform as part of the test method for 
determining the aluminum equivalence. Rather, the requirement is 
specified as a function of the selected operating x-ray tube voltage 
over the normal range of use and is therefore dependent on the waveform 
of the specific x-ray generator being tested.
    When the method for determining HVL was initially established, 
there were fewer generator designs and voltage waveforms than there are 
currently. It is correct that a complete specification of equivalent 
filtration would require a specification of the voltage waveform with 
which it was determined, as well as peak tube potential. However, there 
are no tolerances or specifications given in the standard regarding the 
accuracy with which the filtration equivalent is to be specified. FDA 
notes that one might conclude that since no requirements exist in the 
standard for the accuracy of the statement regarding filtration 
equivalent, it does not need to be so precise as to require description 
of or limitation on the waveform used. Note that a similar requirement 
exists in 1020.30(h)(4)(ii) for beam-limiting devices.
    (Comment 23) One comment strongly supported the consolidation of 
instructions for use of the various modes of operation of fluoroscopic 
systems into a single section of the user's instructions. The comment 
further suggested that the instructions be required to include a 
description of all of the controls accessible to the operator at the 
normal working position.
    (Response) FDA does not believe that such a requirement is 
necessary, as FDA expects that any user's instructions will include a 
complete description of all controls, including any controls available 
at the operator's working position.
    (Comment 24) Three comments expressed concern regarding the 
requirement in proposed Sec.  1020.30(h)(5) that manufacturers describe 
specific clinical procedures or uses for which a specific mode of 
operation is designed or intended. The concern expressed was that the 
clinical use of the fluoroscopic system should not be limited by any 
statements required of the manufacturer

[[Page 34004]]

regarding the purposes of any mode of operation.
    (Response) FDA agrees that clinical use of the system should not be 
limited to the examples provided by the manufacturer. The manner of use 
and the decision to use a particular mode of operation are medical 
decisions. In addition, the requirements of the performance standard 
apply only to manufacturers and do not impose requirements on the users 
of such systems. The requirement at Sec.  1020.30(h)(5)(ii) has been 
modified to reflect that a manufacturer's descriptions of particular 
clinical procedures exemplifying the use of specific modes of operation 
do not limit when or how any mode may be used in actual clinical 
practice.
    In addition, FDA has revised Sec.  1020.30(h)(5)(i) to further 
elaborate the type of information required to be provided to users with 
respect to the description of modes of operation. FDA believes it is 
important for users to understand the manner in which a given mode of 
operation controls the system technique factors and that this 
information should be included in the description of the mode of 
operation.
    (Comment 25) An error in the proposed rule, which was detected by 
FDA following publication, was pointed out by one of the comments. 
Proposed Sec.  1020.30(h)(6)(i) would have required a statement by the 
manufacturer of the maximum deviations of the values of AKR and 
cumulative air kerma from their displayed values.
    (Response) This requirement should have been removed from the 
proposed rule as it was replaced by the requirement in proposed Sec.  
1020.32(k)(7) specifying the maximum deviation allowed. Proposed Sec.  
1020.30(h)(6)(i) has been removed and Sec.  1020.32(k)(7) has been 
revised to be Sec.  1020.32(k)(6). This revision of Sec.  1020.32(k) is 
described in section III.D.8 of this document.
    (Comment 26) One comment suggested that, in addition to requiring 
instructions and schedules for calibrating and maintaining any 
instrumentation required for measurement or evaluation of the AKR and 
cumulative air kerma, Sec.  1020.30(h)(6)(ii) should also require 
manufacturers to provide any hardware or software tools or accessories 
necessary to accomplish such calibration or maintenance.
    (Response) FDA is not adding such a requirement to the standard at 
this time, but will consider it along with the other suggestion 
regarding information or equipment features that should be included in 
the performance standard.
3. Beam Quality--Increase in Minimum Half-Value Layer (Sec.  
1020.30(m))
    (Comment 27) One comment objected to the revision of the 
requirements for minimum half-value of the x-ray beam in Sec.  
1020.30(m)(1) on the grounds that the new minimum requirements for all 
systems should not be based on what the comment considered to be state-
of-the-art equipment. The comment suggested a set of reduced minimum 
values.
    (Response) It appears that the comment misunderstood the basis for 
the FDA proposal and the intent of the increased HVL values. Currently, 
to comply with paragraph 29.201.5 of the IEC standard IEC 60601-1-3, 
all x-ray systems other than mammographic and some dental x-ray systems 
must contain total filtration material in the x-ray beam that provides 
a quality equivalent filtration (using IEC terminology) of not less 
than 2.5 millimeters of aluminum (mm Al). Thus, all currently 
manufactured x-ray systems should be manufactured in a manner that 
assures this amount of filtration in the beam if compliance with the 
IEC standard is claimed. The proposal to increase the HVL requirements 
in the FDA standard, which must be expressed as a performance standard 
rather than as a design standard for a given thickness of filtration, 
is intended to provide HVL values that correspond to those that result 
from the use of a filtration corresponding to the 2.5 mm Al required by 
the current IEC standard. Therefore, the changes proposed for HVL will 
simply bring FDA's requirements into agreement with the performance 
provided by systems complying with the IEC standards IEC 60601-1-3 and 
IEC 60601-2-43. Manufacturers currently complying with the IEC standard 
should experience no impact from this change as all of their production 
should already meet the requirement. Therefore, the change suggested by 
the comment is not necessary.
    FDA notes that several values in table 1 in proposed Sec.  
1020.30(m)(1) are being revised in order to fully agree with existing 
and proposed IEC standards that address the minimum HVL for diagnostic 
x-ray systems. The values of HVL in table 1 in proposed Sec.  
1020.30(m)(1) for several tube voltages in the column heading ``II--
Other X-Ray Systems''are being changed. The changes will have no 
significant impact on the radiation safety provided by the amendment.
    (Comment 28) In conjunction with the proposed revision of the 
requirements for the minimum HVL of the x-ray beam, one comment 
suggested a 60 kVp lower limit for intraoral dental x-ray systems. The 
comment suggested that systems with lower kVp capabilities are not dose 
efficient.
    (Response) FDA notes that a previous amendment to the performance 
standard in 1979 increased the beam quality requirements for x-ray 
systems manufactured after December 1, 1980. The increased beam quality 
required of these systems was intended to preclude systems from 
operating below 70 kVp, while complying with the beam quality 
requirements. FDA believes that the modified requirements that became 
effective in 1980 limited the ability of dental intraoral x-ray systems 
to operate at lower voltages. FDA is not aware of information 
indicating that there are significant numbers of newly-manufactured 
systems that operate with such low voltage capability. Should FDA 
become aware that the current requirements are not effective in 
limiting the beam quality of intraoral dental x-ray systems to 
appropriate values, future consideration will be given to proposing an 
appropriate amendment.
    (Comment 29) Two comments suggested that Sec.  1020.30(m)(2) 
contain a requirement that the system provide an indication to the user 
of the amount of additional filtration that is in the beam at any time 
during system use. The comments did not express a preference for the 
location for this display, indicating that it could be at the system 
control console or at the operator's location. A third comment 
supported the addition of Sec.  1020.30(m)(2), noting the impact of the 
requirement in reducing patient dose and maintaining image quality.
    (Response) FDA agrees that there should be a requirement for a 
display of the amount of additional filtration in use because it is 
important that the operator of the system be able to easily determine 
the added filtration that is currently in use during any procedure. An 
active display of this information will assist the operator. 
Manufacturers of systems that currently do not provide such a feature 
will be required to redesign to implement the capability to select and 
add filtration.
    Accordingly, FDA has modified proposed Sec.  1020.30(m)(2) to 
require an indication of the additional filtration in the beam. FDA has 
also clarified the requirement to state that the selection or insertion 
of the additional filtration can be either at the option of the user or 
automatically accomplished as part of the selected mode of operation. 
FDA notes that automatic selection and concurrent modification of the

[[Page 34005]]

technique factors to maintain image quality is the preferred method of 
operation. Efficient manual use of additional filtration requires that 
the user make appropriate technique changes to preserve optimum image 
quality.
    FDA notes that, through an oversight, no effective date was 
proposed for the new requirement in Sec.  1020.30(m)(2). This new 
requirement was intended to become effective, along with all of the 
other new requirements, 1 year after the date of publication of the 
amendments in the Federal Register. FDA has modified proposed Sec.  
1020.30(m)(2) to reflect the effective date.
4. Aluminum Equivalent of Material Between Patient and Image Receptor 
(Sec.  1020.30(n))
    (Comment 30) One comment noted that the values given in table 2 in 
Sec.  1020.30(n) need to be revised as a result of the revision of 
Sec.  1020.30(m)(1). According to the comment, if the values of the 
maximum aluminum equivalence given in table 2 are not revised to 
reflect the increased beam quality required by Sec.  1020.30(m)(1) for 
the test voltage of 100 kVp for determining compliance with Sec.  
1020.30(n), the current requirements of table 2 in Sec.  1020.30(n) 
would in effect require that items between the patient and the image 
receptor provide less attenuation than currently required.
    (Response) The comment is correct that FDA's proposal was not 
intended to reduce the limits on the maximum allowed aluminum 
equivalence of materials between the patient and the image receptor. 
The comment is also correct that the values in table 2 in Sec.  
1020.30(n) were based on the beam qualities associated with the current 
values in table 1 in Sec.  1020.30(m)(1), reflecting a beam quality of 
2.7 mm of aluminum HVL, and not the beam quality described in the 
proposed revision of Sec.  1020.30(n), which is an HVL of 3.6 mm Al at 
100 kVp. However, the comment's reference to the values in table 2 in 
Sec.  1020.30(n) as HVL values was incorrect, although that does not 
invalidate the concern raised by the comment. Therefore, FDA is 
revising the values in table 2 in Sec.  1020.30(n) for the maximum 
aluminum equivalent of materials between the patient and image receptor 
to reflect requirements that are met by current products that comply 
with the present standard. These revised limits are consistent with the 
maximum limits used in current IEC standard IEC 60601-1-3 (Ref. 2). 
This change continues the current requirement for maximum aluminum 
equivalence, but has no impact on current products and will not require 
changes in design.
5. Modification of Certified Diagnostic X-Ray Components and Systems 
(Sec.  1020.30(q))
    (Comment 31) Two comments suggested that a party other than the 
owner be required to certify the continued compliance of any certified 
system that is modified in accordance with Sec.  1020.30(q).
    (Response) The current requirement was not proposed for change and 
no change is considered necessary by FDA. As discussed in the preamble 
to the proposed rule, the requirement in Sec.  1020.30(q)(2) states 
that the owner of an x-ray system may modify the system, provided that 
the modification does not result in a failure of the system to comply 
with an applicable requirement of the performance standard. In 
accomplishing such a modification, the owner may employ a third party 
with the requisite skills and knowledge to accomplish the modification 
in a manner that does not result in noncompliance. As the responsible 
party, the owner should assure that any modifications are accomplished 
appropriately. This can be done through contractual arrangements with 
the party performing the modifications to assure compliance is 
maintained or through any other means that satisfies the owner that 
compliance has not been compromised by the modification. Section 
1020.30(q) does not require that owners themselves perform the 
modification, but rather that owners be responsible for assuring the 
compliance of the modified system.
    (Comment 32) One comment suggested that the party performing the 
modification be required to certify and report the modification in a 
manner similar to that required of an assembler of a new x-ray system. 
Another recommended that the party performing the modification submit a 
report as required by subpart B of 21 CFR part 1002 to the owner of the 
x-ray system.
    (Response) FDA does not see a need for the reporting of such a 
modification. The reporting of the assembly of an x-ray system is 
required to provide a mechanism for the assembler of the system to 
complete the certification that the system has been assembled according 
to the manufacturer's instructions and therefore complies with the 
standard. The compliance of any modified system can be verified during 
a routine inspection by Federal or state authorities. FDA also notes 
that the contractual arrangement between the owner and a party engaged 
by the owner to perform a modification can be structured to provide the 
owner with the necessary assurances that the party performing the 
modifications is responsible to the owner for assuring the continued 
compliance of the system. FDA concludes that there is no need to 
describe these arrangements in the standard beyond the requirement that 
the owner be responsible for assuring the continued compliance of any 
modifications to its system.
    Upon reviewing the comments relating to Sec.  1020.30(q), FDA 
decided, on its own initiative, to add a phrase to Sec.  1020.30(q)(2) 
that was not described in the proposed rule. This phrase clarifies 
where the recorded information regarding an owner-initiated 
modification is to be maintained. The phrase specifies that the 
information is to be maintained with the system records.

C. Comments on Proposed Changes to Sec.  1020.31--Radiographic 
Equipment

1. Field Limitation and Post Exposure Adjustment of Digital Image Size
    (Comment 33) One comment suggested a change in the requirement for 
beam limitation on radiographic x-ray systems that was not proposed. 
This comment recommended that automatic collimation be required for 
digital radiographic systems to preclude what it referred to as 
``digital masking'' of images obtained with the x-ray beam limiting 
device (collimator) adjusted to produce an x-ray field larger than the 
sensitive area of the digital image receptor. This comment expressed a 
concern about the operation of digital radiographic systems and the 
manner in which the x-ray field size is adjusted. Because digital 
radiographic systems permit the opportunity for post-exposure image 
manipulation, the comment expressed concern that adjustment following 
image acquisition of the area imaged or ``image cropping'' might occur, 
obscuring the fact that the x-ray field was not adjusted appropriately 
and therefore not limited to the clinical area of interest.
    (Response) FDA agrees that digital image cropping in lieu of 
appropriate x-ray field limitation could be a concern for systems that 
produce digital radiographic images with a digital image receptor used 
in place of a film/screen cassette, or for fluoroscopic systems when 
used to produce a radiographic image via the fluoroscopic image 
receptor, analogous to use of a photospot camera for analog images. For 
fluoroscopy and radiography using the fluoroscopic imaging assembly, 
proposed Sec.  1020.32(b)(4) and (b)(5) require that the x-ray field 
not exceed

[[Page 34006]]

the visible area of the image receptor by more than specific 
tolerances. These requirements for the fluoroscopic imaging assembly 
are intended to prevent imaging with the x-ray field adjusted to a size 
greater than the selected visible area of the image receptor. However, 
it may not be clear how this requirement applies to radiographic images 
at the time of later storage or display.
    For radiographic images, obtained directly using a digital 
radiographic image receptor, such as a solid-state x-ray imaging 
device, or from the fluoroscopic image receptor, the comment raised the 
question of whether some control is needed to assure that x-ray fields 
are not used when they are larger than necessary for the ultimate size 
of the either stored or displayed image.
    Neither the current standard nor the proposed amendments address 
the issue of post-exposure image cropping of the original image at the 
time of image display or image storage. In the case of a radiographic 
system, including a purely digital system, the current standard 
requires that the x-ray field size not exceed the size of the image 
receptor, meaning that portion of the image receptor area that has been 
preselected during imaging such as when using a spot-film device.
    The comment addresses the concern that the x-ray field might be 
larger than necessary to capture the area of clinical interest and that 
the individual obtaining the image could ``hide'' this fact by 
electronically cropping the digital image for storage and display. 
Thus, it would not be possible for someone reviewing the image later to 
determine that the image was obtained with an x-ray field size larger 
than necessary, resulting in unnecessary patient exposure. The comment 
suggests some type of automatic collimation to prevent this 
possibility, but does not describe the automatic system envisioned. If 
electronic cropping of digital imaging is available post exposure, it 
does not appear possible to have an automatic collimation system that 
could anticipate how such cropping might be done to the exposure.
    FDA notes that the question of electronic image cropping is a 
question that requires further exploration and discussion with the 
equipment users to determine if a requirement to address this issue is 
needed. The agency will review this issue and determine what the 
current equipment design and usage practices are. If FDA determines 
that a limitation on the ability to crop digital images is warranted 
and feasible, it will be addressed in a future proposed amendment.
2. Policy Regarding Disabled Positive Beam Limitation Systems
    (Comment 34) One State radiation control agency submitted a comment 
expressing disappointment that FDA did not propose an amendment that 
would have codified its policy regarding application of the standard to 
x-ray systems that are reassembled and that contain positive beam 
limitation systems that may have previously been disabled by the owner 
of the system.
    (Response) FDA did not propose amending the standard to include 
this clarification because it is not a performance requirement and the 
standard clearly states the performance required of stationary, 
general-purpose systems and the obligations of assemblers to install 
certified components according to the manufacturer's instructions. The 
performance standard originally required that stationary, general-
purpose x-ray systems be equipped with beam limiting devices that 
provided positive beam limitation (PBL). The standard was amended in 
1993 (58 FR 26386) to remove the requirement that stationary, general-
purpose systems be equipped with a beam limiting device providing PBL 
and permitting instead beam limiting device that provides continuous 
adjustment of the x-ray field. Questions arose regarding the 
performance required of beam limiting devices that were designed and 
certified to provide PBL when assembled into x-ray systems that were no 
longer required to provide PBL.
    The standard requires, in Sec.  1020.30(d), that assemblers of 
diagnostic x-ray systems must install certified components according to 
the instructions of the component manufacturer when these certified 
components are installed in an x-ray system. Thus, the standard 
requires that, when an assembler installs a beam limiting device, 
including one designed to provide PBL, the beam limiting device must be 
installed according to the manufacturer's instructions. That is, the 
beam limiting device must be installed such that the PBL system 
functions as designed and according to the manufacturer's instructions. 
FDA clarified this issue via communications to manufacturers, State 
radiation control agencies and others that emphasized the continuing 
requirement that any certified component be installed according to the 
manufacturer's instructions. Although the installation of a beam 
limiting device providing PBL became optional for stationary general-
purpose systems, FDA noted that the requirement to install any 
certified component according to manufacturer's instructions remained. 
Thus, a PBL system, if instal