1、Designation:F207909(Reapproved 2013)Standard Test Method forMeasuring Intrinsic Elastic Recoil of Balloon-ExpandableStents1This standard is issued under the fixed designation F2079;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the
2、year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 The purpose of this test method is to quantify thepercentage by which the diameter of a stent decreases from itsexp
3、anded diameter while still on the delivery balloon to itsrelaxed diameter after deflating the balloon.This test method isappropriate for stents manufactured from a material that isplastically deformed when the stents diameter is increasedfrom its predeployed size to its postdeployed size by mechani-
4、cal means.This test method may be performed in air at roomtemperature unless there is a known temperature dependence ofthe material,in which case,the temperature at which the test isconducted shall be stated in the report.1.2 The values stated in SI units are to be regarded asstandard.No other units
5、 of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulator
6、y limitations prior to use.2.Terminology2.1 Definitions:2.1.1 labeled diameter,nthe nominal deployed size of astent as indicated on its manufacturers label.2.1.2 stent recoil,nthe amount,expressed as a percentage,by which the diameter of a stent changes from the expandeddiameter measured with the st
7、ent on the inflated deliveryballoon to the final value measured after deflating the balloon.3.Summary of Test Method3.1 A sample device representative of product that will bemarketed is either premounted or mounted on the deliveryballoon at the time of use.The delivery balloon is inflated tothe nomi
8、nal expansion pressure indicated for the labeled stent.The outer diameter of the stent is measured in at least threeaxial locations while the stent is still on the inflated deliveryballoon.At each axial location,measurements are taken in twoapproximately orthogonal rotational positions.The balloon i
9、sdeflated and the outer diameter of the stent is remeasured in thesame positions at approximately the same locations.4.Significance and Use4.1 Minimal stent recoil is a desirable feature of a stentbecause it minimizes the maximum diameter to which a stentmust be expanded to achieve its final relaxed
10、 diameter.A stenthaving a high recoil must be expanded to a greater diameter toachieve its final relaxed diameter than a stent having lowrecoil.Practically,excessive expansion of the vessel into whichthe stent is to be implanted may cause tissue damage resultingin a poor immediate result or poor lon
11、g-term outcome.Stentrecoil is affected by intrinsic properties of the material used toconstruct the stent and the specific geometric design of thestent;therefore,measuring stent recoil is an essential part ofevaluating the design.5.Apparatus5.1 A means to inflate with noncompressible fluid,typically
12、water,the delivery balloon on which the stent is mounted.Themeans used must be capable of achieving the pressure requiredto maintain the expanded diameter of the stent until it can bemeasured and may include a device to monitor pressure.5.2 A means to measure the outer diameter of the stentwithout d
13、eforming the stent.Typically,a calibrated opticalsystem,which does not require contact with the stent,is used.The resolution of the measurement system shall be 0.01 mm orbetter.The accuracy of the system shall be 2%of reading orbetter.6.Sampling,Test Specimens,and Test Units6.1 Unless otherwise just
14、ified,all samples selected fortesting should be taken from fully processed,clinical qualityproduct.It is not required that these devices undergo terminalsterilization.Cosmetic rejects or other nonclinical samples maybe used if the cause for rejection has been shown not to affectstent recoil.1This te
15、st method is under the jurisdiction ofASTM Committee F04 on Medicaland Surgical Materials and Devices and is the direct responsibility of SubcommitteeF04.30 on Cardiovascular Standards.Current edition approved March 1,2013.Published March 2013.Originallyapproved in 2001.Last previous edition approve
16、d in 2009 as F2079 09.DOI:10.1520/F2079-09R13.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.2 The number of specimens tested for each unique stentgeometry should be sufficient to meet sampling requirementsfor desired specification limits.In general,a minimum of tenspecimens is recommended.If a single stent geometry isintended to be used for more than one labeled diameter,recoilshall be evaluated for test specimens expanded to the