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 FDAs evaluation of the 
safety and effectiveness of device software functions. In particular, the final guidance includes 
information to help determine a devices 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Within the framework of the superseded guidance, ultrasonic diathermy devices were considered 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 devices risk in the context of the devices 
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-2017D4764. 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. Contains Nonbinding Recommendations
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 Contains Nonbinding Recommendations 
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 FDAs guidance, Format for Traditional and Abbreviated 510(k)s.3
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.
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  
1 Contains Nonbinding Recommendations 
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 
2 Contains Nonbinding Recommendations 
increase to 41C  45C 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.
3 Contains Nonbinding Recommendations 
 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)
4 Contains Nonbinding Recommendations 
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 
5 Contains Nonbinding Recommendations 
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 FDAs 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 
FDAs guidance General Principles of Software Validation6 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 FDAs 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 
6 Contains Nonbinding Recommendations 
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 Devices9
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 areunable to identify a legally marketed predicate device withasimilar location/duration 
of contact and intended use that uses the same materials as used in yourdevice, we recommend 
that youconduct 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 FDAs 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 FDAs 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 
7 Contains Nonbinding Recommendations 
 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.
8 Contains Nonbinding Recommendations 
submission, please see FDAs 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-FiTM) 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 FDAs guidance Radio-Frequency Wireless 
Technology in Medical Devices14 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 
9 Contains Nonbinding Recommendations 
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.  Arthroplastiesthe 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.
10 Contains Nonbinding Recommendations 
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 
11 Contains Nonbinding Recommendations 
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 
12 Contains Nonbinding Recommendations 
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 p  / 2p  at any point in the far field on the beam alignment axis is 
p rms
greater than 1.05, where p  is the temporal-peak acoustic pressure and p  is the r.m.s. acoustic 
p rms
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/() where ERA is the Effective Radiating Area of the treatment head and  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/() or ERA/(3), 
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.
13 Contains Nonbinding Recommendations 
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 p /2p , at any point in the far field on the beam alignment axis, is less 
p rms
than or equal to 1.05, where p  is the temporal-peak acoustic pressure and p  is the r.m.s. 
p rms
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 I  = P/A  where P is the output power and A  is the effective radiating area.
e ER ER
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).
14 Contains Nonbinding Recommendations 
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.
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