Radial Force Measurement
The force-diameter curves of stent like structures are determined while loading and unloading the sample according to a specified profile.
RX550 temperature is set to the defined test temperature
Before and after testing, test samples length and diameter are measured with a micrometric gauging machine
The test samples are selected randomly.
The sample is introduced in the head and profile is started: the RX bench decreases and/or increases the diameter according to specified loading and unloading profile and the radial force vs diameter is recorded.
Pictures of the sample during the test are taken if required by the sponsor
At the end of the test, RX head is opened and the sample is retrieved from the system then placed within its corresponding container.
In order to obtain the result ‘by unit of length’, the force is divided by the measured length (in mmThis procedure describes 5 possible ways of generating a radial force-diameter curve according to a desired loading and unloading profile:
1- Measurement in compression only: the device is compressed from an initial diameter to smaller diameter at a set head speed (balloon expandable or self-expanding structures).
2- Measurement in expansion only: the device is either deployed in the RX head preset at a small initial diameter, or compressed, at a low speed, from an initial diameter at rest to a smaller final diameter. Then, the diameter is gradually increased at a set speed to the final target diameter (self-expanding structures).
3- Measurement over one or more compression / expansion cycles: The device is compressed and released over several cycles to assess its hysteresis behavior (for self-expanding devices).
Note: ASTM 3067 recommends to test balloon expandable stent over a complete cycle (initial balloon deployment and RX compression)
4- Measurement according to customized loading and unloading profiles: Compression and expansion measurement are conducted using a user predefined diameter variation profile generated from specific file (time; diameter)
5- Force measurement: The maximum force to be reached is specified and the head of the RX closes on the device until it reaches a set force.
The RX550/650 from Machine Solutions Inc. is used to measure both the radial force and the diameter while loading or unloading the device according to a specified crushing profile. The RX head is composed of 12 segments which compress the sample uniformly, with very low friction force.
- Load under constant displacement
- Radial force vs. time
- Radial force vs. diameter
- Stent Hoop force
- Stent Radial force
- Stent Diameter
- Stent length
- Balloon expandable stent: CrCo, SS, Biores
- Self-expanding stent: NiTi, SS
- Coronary stent
- Peripheral stent: Carotid, renal, ilio-femoral
- Stent-Graft: AAA, TAA, PE covered, PTFE covered, tissue covered
- TAVI stent structure
- TMVR stent structure
- Vena Cava filters
- Occluders- LAA closure, PFO closure
- Oesophageal Stent
- Any stent like structure
FDA Guidance: Non-Clinical Engineering Tests and Recommended Labeling for Intravascular Stents and Associated Delivery Systems – Guidance for Industry and FDA Staff
FDA Guidance: Coronary and Carotid Embolic Protection Devices – Premarket Notification [510(k)] Submissions
Cardiovascular implants — Endovascular devices — Part 2: Vascular stents
ASTM F3067 – 14
Guide for Radial Loading of Balloon Expandable and Self Expanding Vascular Stents
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