White Paper: Radial Force

Radial Force Testing
Radial force testing is used to determine the stiffness (hoop strength) of a medical device when placed under radial compressive forces, both loading and unloading. Devices that are commonly tested include balloons, stents, stent grafts, and feminine hygiene products, among other devices that are required to apply a chronic outward force. The importance of radial force testing in the medical device development process is perhaps best illustrated with an example. The following case study shows the importance of radial force in the functionality of a self-expandable stent.

Case Study: The Self-Expandable Stent
Accurate stent sizing is crucial. If a stent does not exert enough radial force to stay lodged in its desired position, it may migrate. Stent migration can cause a number of different problems, paravalvular leakage being one of them [1]. When paravalvular leakage occurs, blood flows through the stent and proceeds through cardiac tissue. Paravalvular leakage can cause heart failure, hemolytic anemia, and infectious endocarditis. [2]

Conversely, a stent that exerts too much force on its host vessel can cause vessel wall degeneration and damage. [1] Self-expandable stents, in particular, can be difficult to match to the proper vessel size. Self-expandable stents show a chronic outward radial force once they are deployed in the body. This can result in negative chronic recoil. Negative chronic recoil causes the vessel to expand outward, becoming larger than it naturally was. Other adverse reactions that may occur from improper stent sizing include: in-stent restenosis, thrombosis, and neo intimal proliferation.

Performing radial force testing on your device can help quantitatively characterize device functionality and performance, in turn allowing you to accurately assess the safety and effectiveness of your product.

Our Method
Our lab is ISO 17025 accredited in regards to radial force testing per ASTM 3067-14 and ISO 25539. Additionally, with over 30 years of experience developing test methods and evaluating a wide variety of medical devices, we have the ability to develop unique test methods tailored to your needs.

Radial ForceFigure 1. MSI RX550 Radial Force Tester at MED Institute.

Our Services
At MED Institute, we have the tools and experience to help with your radial force needs. Contact us so that we can help you make products and therapies that will improve patient outcomes.

If you have any questions or need any additional information, please contact:

Justin Metcalf, Director of Engineering Services


[1] M. S. Cabrera, C. W. Oomens and F. P. Baaijens, “Understanding the requirements of self-expandable stents for heart valve replacement: Radial force, hoop force and equilibrium,” Journal of the Mechanical Behavior of Biomedical Materials, vol. 68, pp. 252-264, 2017.
[2] D. Smolka and M. W. Wojakowski, “Paravalvular leak – important complication after implantation of prosthetic valve,” European Society of Cardiology, 8 November 2010. [Online]. Available: https://www.escardio.org/Journals/E-Journal-of-Cardiology-Practice/Volume-9/Paravalvular-leak-important-complication-after-implantation-of-prosthetic-valv. [Accessed 30 August 2017].

How Mobile Health Technology can Lead to Clinical Trial Success


Mobile Health Technology (mHealth) is a general term for the use of mobile phones or other communication devices in medical care. The use of mHealth has received significant attention recently, with good reason. mHealth is making a strong case for its ability to improve clinical trial management and participant engagement. For a technology to be effective in this area, it must provide necessary features and benefits and fit effortlessly into the patient’s daily schedule.

mHealth may help to improve data quality and participant trial adherence. Sponsors/CROs can equip participants with mobile devices and tablets to capture health data from home. Participants can complete diaries and surveys on mobile applications (apps) and submit the information from home versus onsite at the research center. Such convenience increases the likelihood of patients’ full participation in the trial and decreases the likelihood of noncompliances in the participants’ performance. Data can be captured real-time using mHealth which generally improves data fidelity. Timely data capture also allows for prompt identification of participant noncompliance. Action can then be taken to swiftly address any issues and ensure participant compliance going forward—correcting potential problems before they become widespread.  Some apps are developed to assist sponsors/CROs with patient recruitment for clinical trials. For example, Novartis Oncology developed a mobile app, Clinical Trial Seek, where patients and physicians can look for trial information.

In addition to more effectively and conveniently capturing trial data, mHealth may also increase participant engagement in a trial by making it easier to communicate information. If a participant has a trial-related question, it may be possible to check the mobile app and get the answer when needed, either through documentation available on the app or by direct communication with trial staff. Additionally, using mHealth, trial protocols can be set up with flexible schedules that can be fixed, randomized, or event-triggered. Schedules can be set up for daily, weekly, or monthly events and could even be customized with personalized instructions for an individual participant. Educational programs with web-based content can be scheduled on mobile apps to provide the latest information to participants in the trial. Solid participant engagement is key to minimizing the incidence of noncompliance with the trial protocol. mHealth could also increase the reach of certain trials by encouraging patients to participate from a greater distance, as burdensome patient travel requirements of trials are reduced.

As mentioned above, mHealth has a number of potential uses in the clinical research space, and could help make your trial more participant-centric. It could also provide solutions to two of the biggest challenges: participant recruitment and continued participant engagement. Although these technologies may not be appropriate for every trial, they should be considered in trial design as a tool to help optimize chances for success and participants’ best interests.  Despite the expected benefits of using mHealth in clinical trials, the regulatory status with the FDA is not yet entirely clear. Evolving acceptance by regulators will help drive implementation of mHealth in clinical research.

MED Institute has decades of experience in designing and executing clinical trials, and would be pleased to discuss with you how we can help you achieve success in your clinical trial objectives.

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