Policy Clarification and Premarket Notification [510(k)] Submissions for Ultrasonic Diathermy Devices: Guidance for Industry and Food and Drug Administration Staff

Administrative guidance, not enacted legislation. This captured publisher edition preserves the listed document and attachments; later developments are not independently consolidated.

On June 14, 2023, FDA issued a guidance titled “Content of Premarket Submissions for Device
Software Functions.”1 This final guidance supersedes the Guidance for the Content of Premarket
Submissions for Software Contained in Medical Devices, issued on May 11, 2005. The final
guidance issued on June 14, 2023, provides information regarding the recommended
documentation sponsors should include in premarket submissions for FDA’s evaluation of the
safety and effectiveness of device software functions. In particular, the final guidance includes
information to help determine a device’s Documentation Level (formerly known as Level of
Concern). The purpose of the Documentation Level is to help identify the minimum amount of
information that would support a premarket submission that includes device software functions.
Within the framework of the superseded guidance, ultrasonic diathermy devices were considered
a device with a Major Level of Concern. Based on the device’s risk in the context of the device’s
intended use, as discussed in the final guidance “Content of Premarket Submissions for Device
Software Functions,” ultrasonic diathermy devices should generally address the
recommendations for an Enhanced Documentation Level. The actual Documentation Level for
your device may vary based on the specifics of your device. For more information about the
Documentation Level and recommended documentation for a premarket submission, sponsors
are encouraged to review the guidance “Content of Premarket Submissions for Device Software
Functions.”
1 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/content-premarket-
submissions-device-software-functions.

Premarket Notification [510(k)]
Submissions for Ultrasonic
Diathermy Devices
Guidance for Industry and Food and
Drug Administration Staff
Document issued on February 21, 2023.
Document originally issued on April 16, 2018.
For questions about this document, contact OHT5: Office of Neurological and Physical Medicine
Devices at CDRH-Neuro-PhysMed-Guidance@fda.hhs.gov.
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Devices and Radiological Health

Contains Nonbinding Recommendations
Preface
Public Comment
You may submit electronic comments and suggestions at any time for Agency consideration to
https://www.regulations.gov. Submit written comments to the Dockets Management Staff,
Food and Drug Administration, 5630 Fishers Lane, Room 1061, (HFA-305), Rockville, MD
20852-1740. Identify all comments with the docket number FDA-2017–D–4764. Comments
may not be acted upon by the Agency until the document is next revised or updated.
Additional Copies
Additional copies are available from the Internet. You may also send an e-mail request to
CDRH-Guidance@fda.hhs.gov to receive a copy of the guidance. Please include the
document number GUI01500003 and complete title of the guidance in the request.

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Table of Contents
I. INTRODUCTION .....................................................................................................................................1
II. SCOPE ........................................................................................................................................................ 2
III. 510(K) SUBMISSION RECOMMENDATIONS .................................................................................... 2
A. DEVICE DESCRIPTION ...................................................................................................................................2
B. PREDICATE COMPARISON ............................................................................................................................. 4
C. SOFTWARE ................................................................................................................................................... 6
D. BIOCOMPATIBILITY ...................................................................................................................................... 7
E. ELECTRICAL SAFETY AND ELECTROMAGNETIC COMPATIBILITY (EMC) ...................................................... 8
F. WIRELESS TECHNOLOGY .............................................................................................................................. 9
G. LABELING..................................................................................................................................................... 9
(1) Contraindications ............................................................................................................................. 10
(2) Warnings ........................................................................................................................................... 11
(3) Precautions ....................................................................................................................................... 11
H. CLEANING AND REPROCESSING .................................................................................................................. 11
APPENDIX A ..................................................................................................................................................... 13

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Premarket Notification [510(k)] Submissions
for Ultrasonic Diathermy Devices
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
This guidance document provides recommendations for 510(k) submissions for ultrasonic
diathermy devices, also known as physiotherapy devices. Ultrasonic diathermy devices are
devices under section 201(h) of the Federal Food, Drug and Cosmetic Act (the FD&C Act). This
guidance includes recommendations on the use of certain International Electrotechnical
Commission (IEC) standards in generating information that can support 510(k) submissions for
these devices. This guidance also supplements other FDA documents regarding the specific
content requirements and recommendations of a premarket notification (510(k)) submission (also
refer to 21 CFR 807.87).
For the current edition of the FDA-recognized consensus standards referenced in this document,
see the FDA Recognized Consensus Standards Database.1 For more information regarding use of
consensus standards in regulatory submissions, please refer to the FDA guidance “Appropriate
Use of Voluntary Consensus Standards in Premarket Submissions for Medical Devices.”2
This guidance supplements other FDA documents regarding the specific content requirements
and recommendations of a premarket notification (510(k)) submission. You should also refer to
21 CFR 807.87 and FDA’s guidance, “Format for Traditional and Abbreviated 510(k)s.”3
In general, FDA’s guidance documents do not establish legally enforceable responsibilities.
Instead, guidances describe the Agency’s 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.
1 Available at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfStandards/search.cfm.
2 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/appropriate-use-
voluntary-consensus-standards-premarket-submissions-medical-devices
3 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/format-traditional-and-
abbreviated-510ks

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II. Scope
The scope of this document is limited to ultrasonic diathermy devices regulated under 21 CFR
890.5300(a), product codes IMI and PFW, which are class II devices.
This guidance is applicable to ultrasonic diathermy (physiotherapy) devices for use in applying
therapeutic deep heat for selected medical conditions such as relief of pain, muscle spasms, and
joint contractures. This guidance only relates to equipment employing ultrasonic energy at a
frequency beyond 20 kilohertz, using a single plane circular transducer per treatment head, and
producing non-convergent beams perpendicular to the face of the treatment head (i.e., collimated
or divergent).
Other medical devices that include the use of ultrasound are regulated outside of 21 CFR
890.5300(a) and are excluded from the scope of this guidance. Excluded medical devices
include, but are not limited to:
· devices in which ultrasound waves are intended to destroy conglomerates (for example,
stones in the kidneys or the bladder) or tissue of any type;
· devices in which a tool is driven by ultrasound (for example, surgical scalpels,
phacoemulsifiers, dental scalers, or intracorporeal lithotripters);
· devices in which ultrasound waves are intended to sensitize tissue to further therapies (for
example, radiation or chemotherapy);
· devices in which ultrasound waves are intended to treat cancerous (i.e., malignant) or pre-
cancerous tissue, or benign masses, such as High Intensity Focused Ultrasound (HIFU) or
High Intensity Therapeutic Ultrasound (HITU); and
· devices in which ultrasound is intended for aesthetic purposes.
III. 510(k) Submission Recommendations
A. Device Description
Per 21 CFR 890.5300(a), an ultrasonic diathermy device for use in applying therapeutic deep
heat for selected medical conditions is a device that applies to specific areas of the body
ultrasonic energy at a frequency beyond 20 kilohertz and that is intended to generate deep heat
within body tissues for the treatment of selected medical conditions such as relief of pain, muscle
spasms, and joint contractures, but not for the treatment of malignancies. Ultrasonic diathermy
devices for therapy produce high-frequency sound waves that travel deep into tissue and create
mild therapeutic heat. Generally, therapeutic deep heat is generated if a sustained temperature

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increase to 41°C – 45°C is achieved.4 The sound waves are transmitted through a treatment head
that the therapist applies to the skin with gentle, circular movements in most cases. A
hypoallergenic gel aids in the transmission of the ultrasonic energy. This gel, along with
continuous movement of non-stationary applicators, mitigates overheating at the skin surface.
There are three general beam types for ultrasonic devices: convergent (or focusing), collimated,
and divergent. The treatment head of an ultrasonic diathermy device should produce a beam that
is either collimated or divergent. Please see Appendix A for definitions of these and other terms
used in this guidance. Also, for additional relevant definitions, please see the currently FDA-
recognized versions of IEC 61689 and IEC 60601-2-5.
You should provide a general description of the subject device in your 510(k) submission,
including (but not limited to) model designation, design, patient contact materials, and control
panel and system operation. For those who submit a declaration of conformity to the IEC
standards, the following information, based on the IEC consensus standards definitions and
terminology, should be included (as applicable) in your 510(k) submission:
· Quantitative indicators should be included for the output power and effective
intensity in continuous wave mode of operation and temporal-maximum intensity and
temporal-maximum output power in amplitude-modulated mode. The output power
indication should not differ from the actual value by more than ±20% of the actual
value. Generator labeling should include a unique serial number, the acoustic working
frequencies, and waveform type (continuous or amplitude modulated (pulsed)). If the
amplitude is modulated or pulsed, the generator labeling also should include a
description or picture of the output waveform, along with values for the pulse
duration, pulse repetition period, and duty factor. If multiple modulation settings are
possible, then the description or picture should be for the minimum duty factor.
· Adequate description of the spatial distribution of the ultrasonic radiation field and
the orientation of the field with respect to the treatment head should be provided.
This can include a textual discussion with diagrams, plots, or photographs
representative of the beam pattern. If there is more than one ultrasonic transducer,
they are intended to operate simultaneously and their positions are not fixed relative
to each other, then the description must specify the spatial distribution of the
ultrasonic radiation field emitted by each ultrasonic transducer and present adequate
examples of the combination field of the ultrasonic transducers with regard to safe
use.
· Generators that operate in the pulsed mode and have controls to vary the pulse width
and/or pulse repetition period should provide the user with an indication of the
magnitude of these quantities. This indication could be provided by a meter or by
markings on the control itself.
· Generators for which the ultrasonic frequency is variable should provide the user with
an indication of the frequency being used at the time of treatment.
4 Guy, A.W., J.F. Lehmann, and J.B. Stonebridge, Therapeutic applications of electromagnetic power. Proceedings
of the IEEE, 1974. 62(1): p. 55-75.

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· Treatment head labeling should include its rated output power, the effective radiating
area, the beam non-uniformity ratio, the beam type, a unique serial number, acoustic
working frequency, and a designation of the specific generator for which the
treatment head is intended. If a treatment head has been designed for
interchangeability such that it is not possible to specify a particular generator unit,
this should be stated and the method by which interchangeability is achieved should
be described.
· An adjustable timer that de-energizes the output after a preselected operating period
should be incorporated into the device. The timer should have a range not exceeding
30 min and an accuracy of better than ±10% of setting.
· The spatial-peak temporal-average intensity of unwanted ultrasound radiation from a
treatment head intended for hand-held use should be less than 100 mW/cm2, when
measured as described in IEC 60601-2-5.
· Any unique features or technological characteristics of the subject device should be
described, including, for example, but not limited to, descriptions of the types of
applicators (e.g., hand-held applicators, stationary applicators enabling hands-free
operation, etc.), multiple modes, or frequencies.
· Adequate description of the possible range of temperature rise should be provided for
a fixed applicator with, if relevant to the device, an explanation that moving the
applicator could lower spatial peak temperatures (hot spots) and raise spatial
minimum temperatures (cold spots).
· A description (or picture) of the ultrasound field(s) should be provided.
B. Predicate Comparison
For devices reviewed under the 510(k) process, manufacturers must compare their new device to
a similar legally marketed predicate device to support its substantial equivalence (section 513(i)
of the FD&C Act; 21 CFR 807.87(f)). This comparison should provide information to show how
your device is similar to and different from the predicate. Side by side comparisons, whenever
possible, are desirable. See below for examples of how this information could be organized.
This type of information should be provided for each treatment head and each acoustic working
frequency available. In addition, you should identify and compare any accessories intended for
use with the device.
Table 1A. Device Description
Description Subject Device Predicate Device
(Kxxxxxx)
Indications for Use
Manufacturer
Console/Generator Dimensions (L x W x H
cm)
Treatment Head Dimensions (L x W x H cm)
Console/Generator Weight (kg)
Treatment Head Weight (kg)

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Description Subject Device Predicate Device
(Kxxxxxx)
Power Supply
Leakage Current
Crystal Material
Technology of ultrasound generation (e.g.,
piezoelectric, magnetostrictive)
Treatment Mode(s)
Beam Type (collimated or divergent)
Transducer Diameter (cm)
Acoustic Working Frequency and Accuracy
(MHz)
Effective Radiating Area and Accuracy (cm2)
Beam Nonuniformity Ratio (not to exceed
8*) and Accuracy
Output Mode (Continuous Wave/Amplitude –
Modulated Wave)
Maximum Timer Setting and Accuracy (not
to exceed 30 min*)
Beam Maximum Intensity and Accuracy
(W/cm2)
* Per the IEC 60601-2-5 standard
Table 2B. Maximum Values of Powers and Intensities (Max Settings)
Subject Device Predicate Device
(Kxxxxxx)
Maximum Value of the Output Power (Rated
Output Power) and Accuracy (W)
Maximum Value of the Effective Intensity and
Accuracy (Not to exceed 3 W/cm2*)
* Per the IEC 60601-2-5 standard
Table 3C. Information for Amplitude Modulated Waves
Subject Device Predicate Device
(Kxxxxxx)
Pulse Duration and Accuracy (s)
Pulse Repetition Period and Accuracy (s)
Duty Factor and Accuracy (%)
Maximum Value of the Temporal-Maximum
Output Power and Accuracy (W)
Maximum Value of the Temporal-Maximum
Intensity and Accuracy (W/cm2)
Ratio of Temporal Maximum Output Power to
the Output Power

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Table 4D. Temperature Specifications
Subject Device Predicate Device
(Kxxxxxx)
Peak Temperature Rise vs. Time and Tissue
Depth to Maximum Treatment Time (for fixed
Treatment Head Placement) (deg C)
Maximum Patient Contact Surface
Temperature of Treatment Head under
Simulated or Actual Use Conditions for all
Operating Conditions (Continually operated
for maximum treatment time) (deg C)
C. Software
Software in ultrasonic diathermy devices ensures that appropriate energy is delivered to the
patient. Adequate software performance testing provides assurance that the device is operating as
intended and within safe parameters.
Refer to FDA’s “Guidance for the Content of Premarket Submissions for Software Contained in
Medical Devices,”5 for a discussion of the software documentation that you should provide in
your submission. The software guidance outlines the type of documentation to be provided based
on the “level of concern” associated with the device. FDA generally considers the software for
ultrasonic diathermy devices to present a “Major” level of concern. You should also refer to
FDA’s guidance “General Principles of Software Validation”6 for software development
practices.
We recommend that you provide a full description of the software/firmware supporting the
operation of the subject device, following the software guidance, commensurate with the
appropriate level of concern. This recommendation applies to original devices as well as to any
software/firmware changes made to already-marketed devices. Changes to software must be
revalidated and reverified in accordance with 21 CFR 820.30(f), (g), and (i), and documented in
the Design History File in accordance with 21 CFR 820.30(j). Some software changes might
warrant the submission of a new 510(k). For further information on this topic, refer to the FDA
guidance “Deciding When to Submit a 510(k) for a Software Change to an Existing Device.”7
If appropriate, you should also provide information on the Cybersecurity aspects of your device.
For more information on this topic, please see FDA’s guidance “Content of Premarket
Submissions for Management of Cybersecurity in Medical Devices.”8
5 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/guidance-content-
premarket-submissions-software-contained-medical-devices
6 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/general-principles-
software-validation
7 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/deciding-when-submit-
510k-software-change-existing-device
8 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/content-premarket-
submissions-management-cybersecurity-medical-devices

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If the device includes off-the-shelf software, you should provide the additional information
recommended in the FDA documents titled “Off-the-Shelf Software Use in Medical Devices”9
and “Cybersecurity for Networked Medical Devices Containing Off-The-Shelf (OTS)
Software,”10 which provide additional information regarding medical devices utilizing off-the-
shelf software.
Overall, the documentation related to the software contained in the medical device should,
among other things, provide sufficient evidence to describe the role of the software included in
the device, and performance testing to demonstrate that the software functions as designed.
D. Biocompatibility
Ultrasonic diathermy devices contain patient-contacting materials, which, when used for their
intended purpose (i.e., contact type and duration), could induce a harmful biological response.
You should determine the biocompatibility of all patient-contacting materials present in your
device. If the device is identical in composition and processing to a legally marketed predicate
device with a history of successful use, you may reference previous testing experience or
literature, if appropriate.
If you are unable to identify a legally marketed predicate device with a similar location/duration
of contact and intended use that uses the same materials as used in your device, we recommend
that you conduct and provide within the 510(k) submission a biocompatibility risk assessment.
The assessment should explain the relationship between the identified biocompatibility risks, the
information available to mitigate the identified risks, and any knowledge gaps that remain. You
should then provide any biocompatibility testing or other evaluations that were conducted to
mitigate any remaining risks.
We recommend that you follow FDA’s guidance “Use of International Standard ISO-10993,
‘Biological evaluation of medical devices - Part 1: Evaluation and testing within a risk
management process,’”11 which identifies the types of biocompatibility assessments that should
be considered and includes recommendations regarding how to conduct related tests.
Per ISO 10993-1 and FDA’s guidance (Attachment A), ultrasonic diathermy devices are
considered “Surface device,” “Intact skin,” “A – limited” contact duration. Therefore, the
following endpoints should be addressed in your biocompatibility evaluation:
· Cytotoxicity
· Skin sensitization
9 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/shelf-software-use-
medical-devices
10 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/cybersecurity-
networked-medical-devices-containing-shelf-ots-software
11 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/use-international-
standard-iso-10993-1-biological-evaluation-medical-devices-part-1-evaluation-and

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· Irritation testing
Differences in formulation, processing, sterilization, or device surface properties (e.g., nano
structuring) that could affect biocompatibility of the final device might warrant additional
biocompatibility evaluation and testing.
In addition, ultrasonic diathermy device 510(k) submissions should include the following
information about the transmission media used with the ultrasonic diathermy device.
Transmission media such as an acoustic coupling gel is used to acoustically couple the
transducer to the body surface. Such gel is considered a device under the FD&C Act, and thus,
the gel must have marketing clearance.12 If the gel already has received marketing clearance, the
510(k) number should be provided. If the gel has not received marketing clearance, an
appropriate predicate device(s) must be identified. In general, to establish substantial
equivalence, as required by section 513(f) of the FD&C Act, you must identify a predicate
device with the same intended use and technological characteristics (such as measured sound
velocity, acoustic impedance, and sound attenuation) to compare with the subject coupling gel
(see section 513(i) of the FD&C Act). In addition, the gel formulation, biocompatibility
evaluation, labeling (including instructions for use), and shelf life/expiration information, should
be provided.
E. Electrical Safety and Electromagnetic Compatibility
(EMC)
Ultrasonic diathermy devices are medical electrical equipment and therefore may fail to operate
properly in the presence of electromagnetic disturbance. Ultrasonic diathermy devices should be
tested to demonstrate that they perform as anticipated in their intended use environment. We
recommend that this testing be performed as described in the currently FDA-recognized versions
of the following standards for medical electrical equipment safety and electromagnetic
compatibility:
· ANSI/AAMI ES60601-1: Medical electrical equipment - Part 1: General requirements
for basic safety and essential performance.
· IEC 60601-1-2: Medical electrical equipment - Part 1-2: General requirements for basic
safety and essential performance - Collateral standard: Electromagnetic disturbances -
Requirements and tests.
If submitting a declaration of conformity to the above standards, we recommend that appropriate
supporting documentation, such as an assessment of the results and how conformity was
determined be included, along with information regarding test methods used, should be provided
because this series of standards includes general methods with multiple options and, in some
cases, does not include specific acceptance criteria or address assessment of results. For
additional information on providing electromagnetic compatibility information in a premarket
12 It should be noted that ultrasound coupling media are cleared under 21 CFR 892.1570, product code MUI.

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submission, please see FDA’s guidance “Electromagnetic Compatibility (EMC) of Medical
Devices.”13
F. Wireless Technology
If your ultrasonic diathermy device incorporates radiofrequency wireless technology such as
Bluetooth, IEEE 802.11 (Wi-Fi™) or RFID (radio frequency identification) technology, testing
beyond what is specified in the IEC 60601 standards (referenced in section III.E. above) is
recommended to demonstrate that the wireless device functions will perform as intended in
environments with other wireless products. In the design, testing, and use of wireless medical
devices, the correct, timely, and secure transmission of medical data and information is essential
for the safe and effective use of both wired and wireless medical devices and systems. Particular
points to address include quality of service needed, data integrity, coexistence, security, and
EMC of the wireless signals. Due to the increased use of RF wireless technology that operates in
the same frequency range, you should carefully address RF wireless coexistence through testing
of the device with other common applications of RF wireless technology that can be expected to
be present in the environment of use. If your device or system is expected to have two or more
like devices operating wirelessly in close proximity to one another (e.g., mobile or body worn
devices located in a waiting room or the same room of a home), the ability to so operate should
also be tested. We recommend that you consult FDA’s guidance “Radio-Frequency Wireless
Technology in Medical Devices”14 for additional recommendations on this topic.
G. Labeling
The premarket notification must include proposed labeling in sufficient detail to satisfy the
requirements of 21 CFR 807.87(e). Proposed labels and labeling, sufficient to describe the
ultrasonic diathermy device, its intended use, and the instructions for use must be provided.
As prescription devices, ultrasonic diathermy devices are exempt from having adequate
instructions for use under section 502(f)(1) of the FD&C Act, as long as the conditions in 21
CFR 801.109 are met. For instance, labeling must include adequate information for practitioner
use of the device, including indications, effects, routes, methods, frequency, and duration of
administration, as well as any relevant hazards, contraindications, side effects, and precautions
(21 CFR 801.109(d)).
In addition to the labeling requirements in 21 CFR part 801, we recommend that the following
information be included in the labeling:
1) The generator housing should include a legible or clearly visible tag or label permanently
affixed or inscribed with the following information:
a) the full name and address of the manufacturer of the device;
13 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/information-support-
claim-electromagnetic-compatibility-emc-electrically-powered-medical-devices
14 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/radio-frequency-
wireless-technology-medical-devices-guidance-industry-and-fda-staff

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b) the place and month and year of manufacture (e.g., Manufactured: <Insert Month and
Year of Manufacture>);
c) the brand name, model designation, and unique serial number or other unique
identification so that it is individually identifiable;
d) the acoustic working frequencies (unless there is an operation control for varying this
quantity);
e) the type of waveform (e.g., continuous wave or amplitude modulated); and
f) for amplitude modulated waveforms, a description or picture of the output waveform,
along with values for the pulse duration, pulse repetition period, and duty factor. If
multiple modulation settings are possible, then the description or picture should be for the
minimum duty factor.
2) Each applicator should bear the following information: its rated output power in watts, the
acoustic working frequencies, the effective radiating area in square centimeters, the beam
non-uniformity ratio, the beam type, and a designation of the specific generator of the
equipment for which the treatment head is intended. In addition, the brand name, model
designation, and unique serial number or other unique identification should be included so
that it is individually identifiable.
3) Each operation control should be clearly labeled identifying the function controlled and,
where appropriate, the units of measure of that function. If a separate control and indicator
are associated with the same function, then the labeling for the indicator should include the
appropriate units of measure of that function.
4) Each service control that is accessible without displacement or removal of any part of the
ultrasonic diathermy device should be clearly labeled, identifying the function controlled,
and include the phrase "for service adjustment only."
(1) Contraindications
Based on known risks associated with this device type, we recommend including the following
information in the contraindications section, as applicable, in the instructions for use. Sample
language is provided in italics. If you believe that any of these contraindications are not
applicable to your device, you should provide a justification for each omission in your 510(k)
submission.
1. Patients with an implanted medical device other than a pacemaker such as implanted deep
brain stimulation device.
2. Near brain, cervical ganglia, spine, laminectomy sites (can cause spinal-cord heating).
3. Near the reproductive organs.
4. Total hip arthroplasties with methylmethacrylate or high-density polyethylene. These have a
high coefficient of absorption, more than soft tissue, and the prosthesis could loosen due to
unstable cavitation in the cement.
5. Arthroplasties—the effect on bony ingrowth arthroplasties is not well defined; for this
reason, the most prudent course is avoiding ultrasonic diathermy over these areas.
6. Over or near bone growth centers until bone growth is complete.
7. Over the thoracic area if the patient is using a cardiac pacemaker.
8. In an area of the body where a malignancy is known to be present.
9. In an area of the body where infectious disease is present.

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10. Blood vessels in poor condition should not be treated, as the vessel walls could rupture as a
result of the treatment.
11. Patients suffering from cardiac disease should not receive treatment over the cervical
ganglia, the stellate ganglion, the thorax in the region of the heart, or the vagus nerve, as a
reflex coronary vasospasm might result. Only low intensities and short treatment times
should be used if these patients are treated in other areas because the stimulation of
practically any afferent autonomic nerve (especially the vagus nerve) in the body could cause
a change in cardiac rate.
12. Patients with thrombophlebitis or other potentially thromboembolic diseases should not be
treated because a partially disintegrated clot could result in an obstruction of the arterial
supply to the brain, heart or lungs.
13. Over a healing fracture.
14. Over the eye.
15. Over the pregnant uterus.
16. Over ischemic tissues in individuals with vascular disease where the blood supply would be
unable to follow the increase in metabolic demand.
17. Over areas of recent bleeding or hemorrhage.
18. Over areas of active tuberculosis.
(2) Warnings
We recommend including the following information in the warnings section of the
instructions for use:
1. The treatment head should be moved continuously during treatment to avoid discomfort and
burns.
2. An appropriate coupling medium should be used in order to ensure energy transmission to
the tissue.
(3) Precautions
We recommend including the following information in the precautions section of the
instructions for use regarding use of the device over these areas or on patients with these
conditions:
1. Over anesthetized areas.
2. On patients with hemorrhagic diatheses.
3. Over areas where there is sensory impairment or sensory loss.
4. Over acute skin conditions such as eczema, dermatitis, etc.
5. Over the anterior aspect of the neck.
6. On patients who are febrile.
H. Cleaning and Reprocessing
Under section 502(f)(1) of the FD&C Act and its implementing regulations found in 21 CFR Part
801, a device must have adequate instructions for use, which include directions on preparing a
device for use. See 21 CFR 801.5(g). Prescription devices are exempt from this adequate

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instructions for use requirement, as long as certain conditions are met, including that the labeling
bears “information for use, including indications, effects, routes, methods, and frequency and
duration of administration, and any relevant hazards, contraindications, side effects, and
precautions under which practitioners licensed by law to administer the device can use the device
safely and for the purpose for which it is intended…” 21 CFR 801.109(d). Instructions on how to
reprocess a reusable device are critical to ensure that a device is appropriately prepared for its
initial and subsequent uses; and thus, such directions are considered a condition for exemption
from adequate instructions for use under 21 CFR 801.109. For recommendations regarding the
development and validation of reprocessing instructions in your proposed device labeling, please
refer to FDA guidance “Reprocessing Medical Devices in Health Care Settings: Validation
Methods and Labeling.”15
15 Available at https://www.fda.gov/regulatory-information/search-fda-guidance-documents/reprocessing-medical-
devices-health-care-settings-validation-methods-and-labeling

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APPENDIX A
Glossary of Terms
For the purposes of this guidance, the following terminology and definitions are provided to
facilitate consistency.
Active Area Coefficient
Quotient of the active area gradient, m, and the beam cross-sectional area at 0.3 cm from the face
of the treatment head, ABCS(0.3).
Active Area Gradient
Gradient of the line connecting the beam cross-sectional area at 0.3 cm from the face of the
treatment head, ABCS(0.3), and the beam cross-sectional area at the position of the last axial
maximum acoustic pressure, ABCS(zN), versus distance.
Amplitude Modulated Wave
Wave in which the ratio pp / √2prms at any point in the far field on the beam alignment axis is
greater than 1.05, where pp is the temporal-peak acoustic pressure and prms is the r.m.s. acoustic
pressure.
Acoustic Working Frequency
Frequency of an acoustic signal based on the observation of the output of a hydrophone placed in
an acoustic field. The signal is analyzed using the zero-crossing frequency technique.
Attachment Head
Accessory intended to be attached to the treatment head for the purpose of modifying the
ultrasonic beam characteristics.
Beam Axis
Straight line joining two points of spatial-peak temporal-peak acoustic pressure on two plane
surfaces parallel to the faces of the treatment head. One plane is at a distance of approximately
ERA/(πλ) where ERA is the Effective Radiating Area of the treatment head and λ is the
wavelength of the ultrasound corresponding to the nominal value of the acoustic-working
frequency. The second plane surface is at a distance of either 2ERA/(πλ) or ERA/(3πλ),
whichever is more appropriate. For the purposes of alignment, this line may be projected to the
face of the treatment head.
Beam Maximum Intensity
Product of the beam non-uniformity ratio and effective intensity.
Note 1: Beam maximum intensity is expressed in watt per square meter (W/m2).
Beam Non-uniformity Ratio (BNR)
Ratio of the square of the maximum r.m.s. acoustic pressure to the spatial average of the square
of the r.m.s. acoustic pressure, where the spatial average is taken over the effective radiating
area.

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Beam Type
Descriptive classification for the ultrasonic beam in one of three types: collimated, convergent,
or divergent.
Collimated
Beam for which the active area coefficient, Q, obeys the following inequality: – 0.05 cm-1 ≤ Q ≤
0.1 cm-1.
Continuous Wave
Wave in which the ratio pp/√2prms, at any point in the far field on the beam alignment axis, is less
than or equal to 1.05, where pp is the temporal-peak acoustic pressure and prms is the r.m.s.
acoustic pressure.
Divergent
Beam for which the active area coefficient, Q, obeys the following inequality: Q > 0.1 cm-1.
Duty Factor
Ratio of the pulse duration to the pulse repetition period.
Effective Intensity
Intensity given by Ie = P/AER where P is the output power and AER is the effective radiating area.
Effective Radiating Area (ERA)
Beam cross-sectional area determined at a distance of 0.3 cm from the front of the treatment
head, ABCS(0.3), multiplied by a dimensionless factor, equal to 1.354.
Note 1: Beam cross-sectional area is expressed in centimeter squared (cm2).
Note 2: This may be thought of as the area of the face of the treatment head which transmits
100% of the total output power.
Last Axial Maximum Acoustic Pressure
The last spatial relative maximum r.m.s. acoustic pressure measured outward from the
transducer, along the Beam Axis.
Output Power
Time-average ultrasonic power emitted by a treatment head of ultrasonic physiotherapy
equipment into an approximately free field under specified conditions in a specified medium,
preferably in water.
Note: Output power is expressed in watts (W).
Pulse Duration
Time interval beginning at the first time the pressure amplitude exceeds a reference value and
ending at the last time the pressure amplitude returns to that value. The reference value is equal
to the sum of the minimum pressure amplitude and 10% of the difference between the maximum
and minimum pressure amplitude.
Note: Pulse duration is expressed in seconds (s).

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Pulse Repetition Period
Time interval between two equal moments in time of successive pulses or tone-bursts.
Note: Pulse repetition period is expressed in seconds (s).
Rated Output Power
Maximum output power of the ultrasonic physiotherapy equipment at the rated value of the
mains voltage, with control settings configured to deliver maximum output power.
Note: Rated output power is expressed in watts (W).
Temporal-Maximum Intensity
In the case of an amplitude modulated wave, the ratio of the temporal-maximum output power to
the effective radiating area.
Temporal-Maximum Output Power
In the case of an amplitude modulated wave, a function of the actual output power, the temporal-
peak acoustic pressure and the r.m.s. acoustic pressure. (It is equal to the output power divided
by the duty factor.)
Treatment Head
Assembly comprising an ultrasonic transducer and associated parts for local application of
ultrasound to the patient.
Note: A treatment head is also referred to as an applicator.
Ultrasound
Acoustic oscillation whose frequency is above the high-frequency limit of audible sound (about
16 kHz).
Ultrasonic Physiotherapy Equipment (also referred to as equipment)
Equipment for the generation and application of ultrasound to a patient for therapeutic purposes.
Note: Essentially the equipment comprises a generator of electric high-frequency power and a
transducer for converting this to ultrasound.
Ultrasonic Transducer
Device component capable of converting electrical energy to mechanical energy within the
ultrasonic frequency range and/or reciprocally of converting mechanical energy to electrical
energy.