Performance Standard for
Diagnostic X-Ray Systems and
Their Major Components
(21CFR 1020.30, 1020.31, 1020.32,
1020.33);
Small Entity Compliance Guide
Guidance for Industry and
Food and Drug Administration Staff
Document issued on February 21, 2023.
Document originally issued on June 7, 2007.
For questions about this document, contact Office of Health Technology 8 (OHT8): Office of 
Radiological Health at RadHealth@fda.hhs.gov 
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Devices and Radiological Health
1 Preface
Public Comment
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acted upon by the Agency until the document is next revised or updated.
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2 Performance Standard for
Diagnostic X-Ray Systems and
Their Major Components
(21 CFR 1020.30, 1020.31, 1020.32,
1020.33);
Small Entity Compliance Guide 
Guidance for Industry and
Food and Drug Administration Staff
This guidance represents the current thinking of the Food and Drug Administration (FDA or 
Agency) on this topic.  It does not establish any rights for any person and is not binding on 
FDA or the public.  You can use an alternative approach if it satisfies the requirements of the 
applicable statutes and regulations.  To discuss an alternative approach, contact the FDA staff 
or Office responsible for this guidance as listed on the title page. 
I.  Introduction
On June 10, 2005, the Food and Drug Administration (FDA) published a final rule entitled 
Electronic Products; Performance Standard for Diagnostic X-Ray Systems and Their Major 
Components (70 FR 33997; subsequently referred to as the rule), which amended the 
performance standard for diagnostic x-ray systems and their major components. FDA has 
prepared this Small Entity Compliance Guide in accordance with section 212 of the Small 
Business Regulatory Enforcement Fairness Act (Public Law 104-121, as amended by Public Law 
110-28) to assist small entities to comply with these changes in the performance standard, which 
became effective June 10, 2006.1 A subsequent amendment to the Radiological Health 
1 For further clarification on aspects of the performance standards for diagnostic x-ray equipment (21 CFR 1020.30 
and 21 CFR 1020.32), see FDAs guidance entitled, Policy Clarification for Certain Fluoroscopic Equipment 
Requirements (available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/policy-
clarification-certain-fluoroscopic-equipment-requirements ).
3 Regulations (88 FR 3638;2 January 20, 2023), removed certain reporting requirements for 
diagnostic x-ray systems and their major components and the current version of this guidance 
reflects these changes. 
In general, FDAs guidance documents do not establish legally enforceable responsibilities. 
Instead, guidances describe the Agencys current thinking on a topic and should be viewed only 
as recommendations, unless specific regulatory or statutory requirements are cited. The use of 
the word should in Agency guidances means that something is suggested or recommended, but 
not required.
II.  Questions and Answers on the Rule
1.  To which products does this rule (21 CFR 1020.30; 1020.31; 1020.32; 
1020.33) apply?
The rule applies to all medical diagnostic x-ray systems and their major 
components. This scope of application includes radiographic, fluoroscopic, and 
computed tomography (CT) diagnostic x-ray systems. The amendments added 
coverage of Image Receptors that are electrically powered or connected with the 
x-ray system manufactured on or after June 10, 2006 and fluoroscopic Air Kerma 
Display Devices manufactured on or after June 10, 2006 to the list of components 
of a diagnostic x-ray system.
2.  What new definitions were added to 21 CFR 1020.30(b)?
a)  Air kerma means kerma in air (see definition of Kerma).
b)  Air kerma rate (AKR) means the air kerma per unit time.
c)  Automatic exposure rate control (AERC) means a device which automatically 
controls one or more technique factors in order to obtain at a preselected 
location(s) a required quantity of radiation per unit time.
d)  C-arm fluoroscope means a fluoroscopic x-ray system in which the image 
receptor and the 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.
e)  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.
f)  Fluoroscopic air kerma display device means a device, subsystem, or 
component that provides the display of AKR and cumulative air kerma 
2 https://www.govinfo.gov/content/pkg/FR-2023-01-20/pdf/2023-00922.pdf 
4 required by section 1020.32(k). It includes radiation detectors, if any, 
electronic and computer components, associated software, and data displays.
g)  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.
h)  Fluoroscopy means a technique for generating 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.
i)  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.
j)  Kerma means the quantity as defined by the International Commission on 
Radiation Units and Measurements. The kerma, K, is the quotient of dE  by 
tr
dm, where dE  is the sum of the initial kinetic energies of all the charged 
tr
particles liberated by uncharged particles in a mass dm of material; thus 
K=dE /dm, in units of J/kg, where the special name for the unit of kerma is 
tr
gray (Gy). When the material is air, the quantity is referred to as air kerma.
k)  Last-image-hold (LIH) radiograph means an image obtained either by 
retaining one or more fluoroscopic images, which may be temporally 
integrated, at the end of a fluoroscopic exposure or by initiating a separate and 
distinct radiographic exposure automatically and immediately in conjunction 
with termination of the fluoroscopic exposure.
l)  Lateral fluoroscope means the x-ray tube and image receptor combination in a 
biplane system dedicated to the lateral projection. It consists of the lateral x-
ray tube housing assembly and the lateral image receptor that are fixed in 
position relative to the table with the x-ray beam axis parallel to the plane of 
the table.
m) 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, 
5 source-image receptor distance (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.
n)  Non-image-intensified fluoroscopy means fluoroscopy using only a 
fluorescent screen.
o)  Radiography means a technique for generating and recording an x-ray pattern 
for the purpose of providing the user with an image(s) after termination of the 
exposure.
p)  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 intensity 
over the area of the imaging device. The electronic signal is then used to 
create an image for display and/or storage.
q)  Source-skin distance (SSD) means the distance from the source to the center 
of the entrant x-ray field in the plane tangent to the patient skin surface.
3.  What additional information is required by 21 CFR 1020.30(h)(5) to be 
provided to users regarding the imaging systems?
Imaging system information. For x-ray systems manufactured on or after June 10, 
2006, that produce images using the fluoroscopic image receptor, the following 
information shall be provided in a separate, single section of the users instruction 
manual or in a separate manual devoted to this information:
i.  For each mode of operation, a description of the mode and detailed 
instructions on how the mode is engaged and disengaged. The 
description of the mode shall identify those technique factors and 
system controls that are fixed or automatically adjusted by 
selection of the mode of operation, including the manner in which 
the automatic adjustment is controlled. This information shall 
include how the operator can recognize which mode of operation 
has been selected prior to initiation of x-ray production.
ii.  For each mode of operation, a descriptive example(s) of any 
specific clinical procedure(s) or imaging task(s) for which the 
mode is recommended or designed and how each mode should be 
used. Such recommendations do not preclude other clinical uses.
4.  How has the warning label (21 CFR 1020.30(j)) on the control panel 
changed?
6 Warning label. The control panel containing the main power switch shall bear the 
warning statement, legible and accessible to view: 
Warning: This x-ray unit may be dangerous to patient and operator 
unless safe exposure factors, operating instructions and maintenance 
schedules are observed.
5.  How have the minimum HVL requirements (21 CFR 1020.30(m)) changed?
The minimum HVL requirements for all x-ray systems (except dental systems 
designed for use with intraoral image receptors) manufactured on or after June 10, 
2006, have been increased as specified according to 21 CFR 1020.30(m), Table 1.
The column titled II-Other X-Ray Systems in Table 1 shows the increased values.
TABLE 1
X-Ray Tube Voltage Minimum HVL
(kilovolt peak) (mm of aluminum)
Designed  Measured  Specified  IOther  IIOther 
Operating  Operating  Dental  X-Ray  X-Ray 
Range Potential Systems1 Systems2 Systems3
Below 51 30 1.5 0.3 0.3
40 1.5 0.4 0.4
50 1.5 0.5 0.5
51 to 70 51 1.5 1.2 1.3
60 1.5 1.3 1.5
70 1.5 1.5 1.8
Above 70 71 2.1 2.1 2.5
80 2.3 2.3 2.9
90 2.5 2.5 3.2
100 2.7 2.7 3.6
110 3.0 3.0 3.9
120 3.2 3.2 4.3
130 3.5 3.5 4.7
140 3.8 3.8 5.0
150 4.1 4.1 5.4
1Dental x-ray systems designed for use with intraoral image receptors and 
manufactured after December 1, 1980.
2Dental x-ray systems designed for use with intraoral image receptors and 
manufactured before or on December 1, 1980, and all other x-ray systems subject 
to this section and manufactured before June 10, 2006. 
3All x-ray systems, except dental x-ray systems designed for use with intraoral 
image receptors, subject to this section and manufactured on or after June 10, 
2006.
7 6.  What is the new requirement (21 CFR 1020.30(m)(2)) for optional filtration 
for certain fluoroscopic systems?
Optional filtration. Fluoroscopic systems manufactured on or after June 10, 2006, 
incorporating an x-ray tube(s) with a continuous output of 1 kilowatt or more and 
an anode heat storage capacity of 1 million heat units or more shall provide the 
option of adding x-ray filtration to the diagnostic source assembly in addition to 
the amount needed to meet the HVL provisions of section 1020.30(m)(1). The 
selection of this additional x-ray filtration shall be either at the option of the user 
or automatic as part of the selected mode of operation. A means of indicating 
which combination of additional filtration is in the x-ray beam shall be provided.
7.  How has the requirement (21 CFR 1020.30(n)) for the maximum aluminum 
equivalent of material between the patient and image receptor changed?
For systems manufactured on or after June 10, 2006, the allowable amount of 
aluminum equivalent material between the patient and image receptor has been 
increased as specified in 21 CFR 1020.30(n), Table 2. The HVL for the x-ray 
beam used to determine the aluminum equivalent material is specified in Table 1 
of 21 CFR 1020.30(m)(1).
TABLE 2
Item Maximum Aluminum 
Equivalent 
(Millimeters)
1. Front panel (s) of cassette holders (total of all) 1.2
2. Front panel (s) of film changer (total of all) 2.3
3. Cradle 2.3
4. Tabletop, stationary, without articulated joints 1.2
5. Tabletop, movable, without articulated joint(s)  1.7
(including stationary subtop)
6. Tabletop, with radiolucent panel having one articulated  1.7
joint
7. Tabletop, with radiolucent panel having two articulated  2.3
joints
8. Tabletop, cantileverd 2.3
9. Tabletop, radiation therapy simulator 5.0
8.  What are the new requirements (21 CFR 1020.30(q)(2)) regarding 
documentation of owner modification of certified diagnostic x-ray 
components or systems?
8 The owner of a diagnostic x-ray system who uses the system in a professional or 
commercial capacity may modify the system, provided the modification does not 
result in the failure of the system or component to comply with the applicable 
requirements of this section or of sections 1020.31, 1020.32, or 1020.33. The 
owner should record the date and the details of the modification in the system 
records and maintain this information, provided the modification of the x-ray 
system does not result in a failure to comply with sections 1020.31, 1020.32, or 
1020.33.
9.  Has the applicability of the rule to Radiographic equipment (21 CFR 
1020.31) changed?
Yes. The provisions of 21 CFR 1020.31 apply to equipment for radiography, 
except equipment for fluoroscopic imaging or for recording images from the 
fluoroscopic image receptor, or computed tomography x-ray systems 
manufactured on or after November 29, 1984.
10.  Has the applicability of the rule to Fluoroscopic equipment (21 CFR 1020.32) 
changed?
Yes. The provisions of this section apply to equipment for fluoroscopic imaging 
or for recording images from the fluoroscopic image receptor, except computed 
tomography x-ray systems manufactured on or after November 29, 1984.
11.  Has the field-limitation requirement (21 CFR 1020.32(b)(4)(ii)) for 
fluoroscopic imaging assemblies with inherently circular image receptors 
been changed for equipment manufactured on or after June 10, 2006?
Yes. For fluoroscopy and radiography using fluoroscopic imaging assemblies 
with inherently circular image receptors, other than radiation therapy simulation 
systems, that are manufactured on or after June 10, 2006, the maximum area of 
the x-ray field in the plane of the image receptor shall conform with one of the 
following requirements:
A.  When any linear dimension of the visible area of the image receptor 
measured through the center of the visible area is less than or equal to 34 
cm in any direction, at least 80 percent of the area of the x-ray field 
overlaps the visible area of the image receptor, or
B.  When any linear dimension of the visible area of the image receptor 
measured through the center of the visible area is greater than 34 cm in 
any direction, the x-ray field measured along the direction of greatest 
misalignment with the visible area of the image receptor does not extend 
beyond the edge of the visible area of the image receptor by more than 2 
cm.
9 12.  Has the field-limitation requirement (21 CFR 1020.32(b)(5)) for fluoroscopic 
imaging assemblies with inherently rectangular image receptors been 
changed for equipment manufactured on or after June 10, 2006?
Yes. For fluoroscopy and radiography using fluoroscopic imaging assemblies 
with inherently rectangular image receptors, other than radiation therapy 
simulation systems, that are manufactured on or after June 10, 2006, the following 
applies:
i.  Neither the length nor the width of the x-ray field in the plane of 
the image receptor shall exceed that of the visible area of the image 
receptor by more than 3 percent of the SID. The sum of the excess 
length and the excess width shall be no greater than 4 percent of 
the SID.
ii.  The error in alignment shall be determined along the length and 
width dimensions of the x-ray field which pass through the center 
of the visible area of the image receptor.
13.  What are the new requirements (21 CFR 1020.32(g)(2)) regarding the 
minimum source-skin distance for source-image receptor distances of less 
than 45 cm?
For stationary, mobile, or portable C-arm fluoroscopic systems manufactured on 
or after June 10, 2006, having a maximum source-image receptor distance of less 
than 45 cm, means shall be provided to limit the source-skin distance to not less 
than 19 cm. Such systems shall be labeled for extremity use only. In addition, for 
those systems intended for specific surgical application that would be prohibited 
at the source-skin distances specified in this paragraph, provisions may be made 
for operation at shorter source-skin distances but in no case less than 10 cm. 
When provided, the manufacturer must set forth precautions with respect to the 
optional means of spacing, in addition to other information as required in section 
1020.30(h).
14.  May fluoroscopic equipment be modified to comply with the new 
requirements (21 CFR 1020.32(h)(2)) for fluoroscopic irradiation-time 
display and signals?
Fluoroscopic equipment may be modified in accordance with 1020.30(q) to 
comply with the requirements of section 1020.32(h)(2). When the equipment is 
modified, it shall bear a label indicating the statement: 
Modified to comply with 21 CFR 1020.32(h)(2).
10 15.  For x-ray controls manufactured on or after June 10, 2006, what are the new 
requirements (21 CFR 1020.32(h)(2)) regarding fluoroscopic irradiation-time 
display and signals?
For x-ray controls manufactured on or after June 10, 2006, there shall be provided 
for each fluoroscopic tube:
i.  A display of the fluoroscopic irradiation time at the fluoroscopists working 
position. This display shall function independently of the audible signal 
described in 1020.32(h)(2)(ii). The following requirements apply:
A.  When the x-ray tube is activated, the fluoroscopic irradiation time in 
minutes and tenths of minutes shall be continuously displayed and updated 
at least once every 6 seconds.
B.  The fluoroscopic irradiation time shall also be displayed within 6 seconds 
of termination of an exposure and remain displayed until reset.
C.  Means shall be provided to reset the display to zero prior to the beginning 
of a new examination or procedure.
ii.  A signal audible to the fluoroscopist shall sound for each passage of 5 minutes 
of fluoroscopic irradiation time during an examination or procedure. The 
signal shall sound until manually reset or, if automatically reset, for at least 2 
second.
16.  For fluoroscopic equipment manufactured on or after June 10, 2006, what is 
the new requirement (21 CFR 1020.32(j)) regarding display of last-image-
hold?
Display of last-image-hold (LIH). Fluoroscopic equipment manufactured on or 
after June 10, 2006, shall be equipped with means to display LIH image following 
termination of the fluoroscopic exposure.
1)  For an LIH image obtained by retaining pretermination fluoroscopic images, 
if the number of images and method of combining images are selectable by 
the user, the selection shall be indicated prior to initiation of the fluoroscopic 
exposure.
2)  For an LIH image obtained by initiating a separate radiographic-like exposure 
at the termination of fluoroscopic imaging, the techniques factors for the LIH 
image shall be selectable prior to the fluoroscopic exposure, and the 
combination selected shall be indicated prior to initiation of the fluoroscopic 
exposure.
3)  Means shall be provided to clearly indicate to the user whether a displayed 
image is the LIH radiograph or fluoroscopy. Display of the LIH radiograph 
shall be replaced by the fluoroscopic image concurrently with re-initiation of 
11 fluoroscopic exposure, unless separate displays are provided for the LIH 
radiograph and fluoroscopic images.
4)  The predetermined or selectable options for producing the LIH radiograph 
shall be described in the information required by section 1020.30(h). The 
information shall include a description of any technique factors applicable for 
the selected option and the impact of the selectable options on image 
characteristics and the magnitude of radiation emissions
17.  For systems manufactured on or after June 10, 2006, what is the new 
requirement (21 CFR 1020.32(k)) for display of values of the air kerma rate 
(AKR) and the cumulative air kerma at the fluoroscopists working position?
Displays of values of AKR and cumulative air kerma. Fluoroscopic equipment 
manufactured on or after June 10, 2006, shall display at the fluoroscopists 
working position the AKR and cumulative air kerma. The following requirements 
apply for each x-ray tube used during an examination or procedure:
1)  When the x-ray tube is activated and the number of images produced per unit 
time is greater than six images per second, the AKR in mGy/min shall be 
continuously displayed and updated at least once every second.
2)  The cumulative air kerma in units of mGy shall be displayed either within 5 
seconds of termination of an exposure or displayed continuously and updated 
at least once every 5 seconds.
3)  The display of the AKR shall be clearly distinguishable from the display of 
the cumulative air kerma.
4)  The AKR and cumulative air kerma shall represent the value for conditions of 
free-in-air irradiation at one of the following reference locations specified 
according to the type of fluoroscope. The reference location shall be identified 
and described specifically in the information provided to users according to 
section 1020.30(h)(6)(iii).
i.  For fluoroscopes with x-ray source below the x-ray table, x-ray source 
above the table, or of lateral type, the reference locations shall be the 
respective locations specified in 1020.32(d)(3)(i), (d)(3)(ii), or 
(d)(3)(v) for measuring compliance with air-kerma rate limits.
ii.  For C-arm fluoroscopes, the reference location shall be 15 cm from the 
isocenter toward the x-ray source along the beam axis. Alternatively, 
the reference location shall be at a point specified by the manufacturer 
to represent the location of the intersection of the x-ray beam with the 
patients skin.
12 5)  Means shall be provided to reset to zero the display of cumulative air kerma 
prior to the commencement of a new examination or procedure.
6)  The displayed AKR and cumulative air kerma shall not deviate from the 
actual values by more than 35 percent over the range of 6 mGy/min and 100 
mGy to the maximum indication of AKR and cumulative air kerma, 
respectively. Compliance shall be determined with an irradiation time greater 
than 3 seconds.
18.  What additional information is required by 21 CFR 1020.30(h)(6) to be 
provided to users regarding the display of values of the air kerma rate 
(AKR) and the cumulative air kerma?
Displays of values of AKR and cumulative air kerma. For fluoroscopic x-ray 
systems manufactured on or after June 10, 2006, the following shall be provided:
i.  A schedule of maintenance for any system instrumentation associated with 
the display of air kerma information necessary to maintain the displays of 
AKR and cumulative air kerma within the limits of allowed uncertainty 
specified by 1020.32(k)(6) and, if the capability for user calibration of 
the display is provided, adequate instructions for such calibration.
ii.  Identification of the distances along the beam axis:
A.  From the focal spot to the isocenter, and 
B.  From the focal spot to the reference location to which displayed values 
of AKR and cumulative air kerma refer according to section 
1020.32(k)(4).
iii.  A rationale for specification of a reference irradiation location alternative 
to 15 cm from the isocenter toward the x-ray source along the beam axis 
when such alternative specification is made according to section 
1020.32(k)(4)(ii).
19.  Who may I contact for further information on this rule?
For questions about this document, contact Office of Health Technology 8 
(OHT8): Office of Radiological Health at RadHealth@fda.hhs.gov.
13