A novel method for conformity assessment testing of therapeutic ultrasounds for post-market surveillance purposes

1. Introduction

Therapeutic ultrasounds are medical devices used for applying therapeutic deep heat for selected medical conditions to specific areas of the body using ultrasound energy [1]. Ultrasound energy is a type of mechanical energy characterized by vibrating or moving particles within a medium. Typically, a frequency between 20 and 40 kilo (k) hertz (Hz) is used for medical purposes to generate deep heat within body tissues. This has healing effects and serves as the treatment of selected medical conditions such as relief of pain, muscle spasms, and joint contractures. As this type of medical device involves transfer of energy to human body, an appropriate classification based on associated risk is performed.

According to the Medical Device Regulation (MDR) 2017 [2], therapeutic ultrasounds are classified as Class IIb which corresponds to a medical device with a moderate to high risk. This classification determines regulatory scrutiny to which these devices are subject to before placing to the market. These devices are considered as active therapeutic devices as they administer or exchange energy with the human body in a potentially hazardous way, taking account of the nature, the density and site of application of the energy [3].

Each predetermined value of power used by therapeutic ultrasound has a specific function. Dangerous adverse events can occur when therapeutic ultrasound fails to detect a patient’s various musculoskeletal problems, such as tissue injury or muscle spasms, undermining their purpose. As the essence of therapeutic ultrasound lies in the power they deliver, post-marketing surveillance is aimed at inspecting the accuracy of the delivered values of the specified measurement quantity.

The classification suggests that this device is a moderate to high-risk category as it uses heat and energy to increase circulation, reduce pain, increase flexibility and accelerate healing. For this reason, it is crucial that there are no limiting irregularities that disrupt its reliable operation. An extensive set of standards is used to demonstrate compliance with the essential safety and performance requirements of therapeutic [4]during the premarketing phase. These standards can be grouped into three categories, general quality standards, electrical safety standards, special standards for therapeutic sounds. However, no standards are imposed onto the post-market oversight of therapeutic ultrasounds.

This paper presents a novel methodology for conformity assessment of therapeutic ultrasounds during usage taking into account the metrological characteristics of the device and utilizing the approach defined for other types of medical devices with measuring functions. The presented method can be used by national regulators as a standard in defining the regulatory framework for post-market conformity assessment of devices used in healthcare.

2. Method

To present the novel methodology, the accepted concept of OIML guidelines for other medical devices with measuring functions such as thermometers or sphygmomanometer was followed [5]. The method, developed under OIML recommendations, is reported as a coherent structure, through the following parts:

Definition of technical requirements for therapeutic sounds

During method validation, the performance assessment testing of therapeutic sounds was done by using two etalons, Fluke Biomedical ESA 620 electrical safety analyser [6] and Ohmic Instrument UPM-DT-100 Ultrasound Power meter [7]. Both of these devices were periodically calibrated in EN ISO 17025 accredited laboratories [8]. The novel method was validated during the 2018–2021 time period. The presented data was analysed using a statistical approach.

3. Results and discussion

The results are presented in two parts. The first part consists of reporting the novel methodology for conformity assessment testing of therapeutic sounds and the second part consists of the validation report of this methodology done in real-time by inspection bodies in Bosnia and Herzegovina and Republic of Serbia.

4. Conclusion

Access to health is fundamental human right. However, various adverse event involving medical devices pose a risk to patients safety and well-being. The importance of safe and compliant medical devices has been especially demonstrated during COVID-19 pandemics [10]. Lately, regulators have been working in improving post-market surveillance of medical devices to ensure that number of incidents and adverse events including medical devices is lowered. Specifically, in the European Union, Medical Device Regulation (MDR) introduces the EUDAMED database [11, 12] containing all information regarding the adverse events associated with medical devices and reported by the end users that may be physicians, medical technicians or patients themselves. However, current databases collect information for each database from both voluntary sources and mandatory reports. Judging by the number of reported incidents involving medical devices it can be concluded that the limitations of the databases are that the data submitted include “incomplete, inaccurate, untimely, unverified, or biased data.” In addition, many use errors stay underreported and data format unknown. Moreover, current databases are limited to administrative data only including manufacturers and distributor data, vigilance and clinical studies data, hence the surveillance is not taking its full capacity. Also, baseline evidence for medical device safety and performance cannot be established due to lack of traceable data.

This paper lays out a novel methodology for conformity assessment testing of therapeutic ultrasound for post-market surveillance purposes. The novel methodology was developed based on OIML guidelines for technical and metrological characteristics and performance evaluation. Developed methodology has been validated by the work of two inspection bodies for medical devices working under the legal metrology framework which has been adopted for medical devices in Bosnia and Herzegovina and Republic of Serbia [13, 14]. The introduction of standardized conformity assessment method for testing of safety and performance of therapeutic ultrasound produced traceable, accurate, complete, verified, nonbiased and standardized data. All data resulting from the inspection carried out by independent appointed inspection bodies has been entered in database specially developed for this purpose – eLab [15]. This practice showed that significant cost-effectiveness can be achieved in management of maintenance in healthcare institutions because standardized data showed certain patterns for healthcare institutions.

The work demonstrated how standardized method for conformity assessment testing produces complete, accurate, verified, traceable and unbiased data. Following the trend of digital transformation and application of artificial intelligence, the researchers investigated application of artificial intelligence on this database [16, 17, 18, 19, 20, 21]. The hypothesis of predictive management of maintenance of medical devices has been set up. Indeed, as medicine is shifting toward personalized medicine clinical engineering should follow the path of predictive approach.