1、Designation: F 2079 09Standard Test Method forMeasuring Intrinsic Elastic Recoil of Balloon-ExpandableStents1This standard is issued under the fixed designation F 2079; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of la
2、st 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 itsexpanded
3、 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-cal
4、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 regula
6、tory 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
7、 the stent 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 t
8、othe nominal 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. T
9、he balloon isdeflated 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
10、final relaxed 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 re
11、sult or poor long-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 noncompress
12、ible fluid, typicallywater, 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 diamete
13、r of the stentwithout deforming 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 Te
14、st Units6.1 Unless otherwise justified, 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 sho
15、wn not to affectstent recoil.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 ten1This test method is under the jurisdiction of ASTM Committee F04 on Medicaland Surgical Mater
16、ials and Devices and is the direct responsibility of SubcommitteeF04.30 on Cardiovascular Standards.Current edition approved Aug. 1, 2009. Published August 2009. Originallyapproved in 2001. Last previous edition approved in 2008 as F 2079 02(2008).1Copyright ASTM International, 100 Barr Harbor Drive
17、, PO Box C700, West Conshohocken, PA 19428-2959, United States.specimens 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 smallestand largest diameters intended for that geometry.6.3 Most
18、stents are comprised of a repetitious continuouspattern or of repeating subunits. If stents are made longer byadditional repetition of the basic geometric pattern or byadding identical subunits, then recoil need be measured on onlya single length of each diameter stent. If, however, dimensionsof the
19、 substructure of the repeating pattern or of the subunits isaltered to change the length, then recoil must be measured foreach unique geometry.7. Procedure7.1 Corresponding paired outer diameter measurements,(that is, Diameterinflatedand Diameterfinal) shall be obtainedwith the stent in approximatel
20、y the same rotational positionwith respect to the measurement system.7.2 The number of locations along the length of the stent atwhich recoil is measured should be determined by initialassessment of the stent geometry. Measurements should bemade at multiple axial locations, including one location ne
21、armidlength and locations near either end of the stent. Additionalmeasurements may be warranted by the stent design. Forexample, if the stent is specifically designed to recoil differ-ently at specific locations along its length, additional measure-ments should be taken at these locations.7.3 Inflat
22、e the balloon to the nominal expansion pressureindicated on the stent labeling. To allow for full expansion ofthe stent, maintain the expansion pressure for 15 to 30 s beforetaking diameter measurements.7.4 For each axial measurement location identified in 7.2,measure the outer diameter of the stent
23、 in two approximatelyorthogonal rotational positions.7.5 Deflate the balloon.7.6 Measure the outer diameter of the stent at the samelocations and in the same rotational positions with respect tothe measurement system as in 7.4. These measurements shouldbe taken no sooner than 10 s after deflating th
24、e balloon.8. Calculation8.1 Calculate the stent recoil for the locations measured in7.4 for each stent using the following equation:Stent Recoil %!5S1SDiameterfinalDiameterinflatedDD* 100 (1)where:Diameterinflated= outer diameter of stent while on inflateddelivery balloon andDiameterfinal= outer dia
25、meter of stent after deflatingdelivery balloon.8.2 Calculate the average and standard deviation of stentrecoil for each axial location at which recoil is measured.9. Report9.1 Report the following information for each labeled diam-eter of each unique stent geometry:9.1.1 Labeled stent diameter, in m
26、illimetres.9.1.2 Labeled stent length.9.1.3 Number of samples measured.9.1.4 Locations at which measurements were taken.9.1.5 Diameterinflated(mean 6 standard deviation, to thenearest 0.01 mm).9.1.6 Diameterfinal(mean 6 standard deviation, to the near-est 0.01 mm).9.1.7 Stent recoil average (mean 6
27、standard deviation, tothe nearest 0.5 %) for each location measured.9.1.8 Temperature at which test is performed.10. Precision and Bias10.1 PrecisionThe precision of this test method has notyet been established. An interlaboratory comparison to deter-mine the precision is being planned.10.2 BiasNo i
28、nformation can be presented on the bias ofthis test method because no material having an acceptablereference value is available.11. Keywords11.1 recoil; stentAPPENDIXES(Nonmandatory Information)X1. RATIONALEX1.1 Balloon-expandable stents typically are deployed forpermanent implant by plastically def
29、orming the material ofconstruction. Upon release of the balloon pressure, the diam-eter will decrease, the exact amount of which depends on thematerial used to construct the stent and the specific design ofthe stent. For optimal clinical results, it is critical that the finaldeployed diameter be app
30、ropriate for the exact location ofdeployment. Moreover, a stent with excessive recoil must beinflated to a larger diameter to achieve the desired finaldiameter. This larger required initial inflation diameter maycause more damage to the vessel than would the lower inflationdiameter required for a st
31、ent with a lower recoil. The implant-ing physician must have guidance as to how much any givenstent design will recoil so that the balloon may be inflated tothe expanded diameter required to achieve the desired finaldiameter. This test method provides a standardized procedureto determine the recoil
32、characteristics of stents so that consis-tent labeling can be written. Note that this test methodmeasures the intrinsic recoil of the stent and may not predicthow the stent will perform when implanted in a vessel in whichstent recoil, stent stiffness, and vessel stiffness interact todetermine the fi
33、nal diameter.F2079092X2. REVISION HISTORYX2.1 This standard was originally approved in 2001. It wasrevised in 2002 to clarify terminology, measurement proce-dures, and reporting requirements.ASTM International takes no position respecting the validity of any patent rights asserted in connection with
34、 any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible techni
35、cal committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideratio
36、n at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harb
37、or Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F2079093
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