ASTM F640-79(2000)
(Test Method)Standard Test Methods for Radiopacity of Plastics for Medical Use
Standard Test Methods for Radiopacity of Plastics for Medical Use
SCOPE
1.1 These test methods cover the determination, by radiography, of the radiopacity of plastic in the form of film, sheet, rod, tube, and moldings. The results of these measurements are an indication of the likelihood of locating the plastic part within the human body.
1.2 Types of Tests -There are three methods of tests described, differing in the method of calculating radiopacity.
1.2.1 Method A -Radiopacity is determined as a specific difference in optical density between the image of the plastic and the background on the X-ray film or equivalent.
1.2.2 Method B - Radiopacity is determined by comparing the images of the test piece and of a standard piece simulating the medical device.
1.2.3 Method C -The intrinsic radiopacity of a plastic is determined by measurements made on the image of a slab of a specific thickness of the formulation.
1.3 The values stated in SI units are to be regarded as the standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:F640–79 (Reapproved 2000)
Standard Test Methods for
Radiopacity of Plastics for Medical Use
This standard is issued under the fixed designation F 640; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope E 7 Terminology Relating to Metallography
E 94 Guide for Radiographic Testing
1.1 These test methods cover the determination, by radiog-
E 135 Terminology Relating to Analytical Chemistry for
raphy, of the radiopacity of plastic in the form of film, sheet,
Metals, Ores, and Related Materials
rod, tube, and moldings.The results of these measurements are
E 142 Test Method for Controlling Quality of Radiographic
an indication of the likelihood of locating the plastic part
Testing
within the human body.
F 647 Practice for Evaluating and Specifying Implantable
1.2 Types of Tests— There are three methods of tests
Shunt Assemblies for Neurosurgical Application
described, differing in the method of calculating radiopacity.
1.2.1 Method A—Radiopacity is determined as a specific
3. Terminology
difference in optical density between the image of the plastic
3.1 Definitions—For definitions of terms relating to X-ray
and the background on the X-ray film or equivalent.
procedures, refer to Guide E 94 and Test Method E 142.
1.2.2 Method B—Radiopacity is determined by comparing
3.2 Descriptions of Terms:
the images of the test piece and of a standard piece simulating
3.2.1 optical density—in photographic photometry, the
the medical device.
logarithm to the base 10 of the ratio of the incident light to the
1.2.3 Method C—The intrinsic radiopacity of a plastic is
transmitted light (seeTerminology E 135).The range of values
determined by measurements made on the image of a slab of a
of optical density expected in this test method is 0.5 to 1.5.
specific thickness of the formulation.
3.2.2 contrast—inthistestmethod,contrastisthedifference
1.3 The values stated in SI units are to be regarded as the
between optical density measurements made on the back-
standard.
ground (nominally 1.0 optical density) and on the test speci-
1.4 This standard does not purport to address all of the
men.
safety concerns, if any, associated with its use. It is the
3.2.3 penetrameter—a device employed to obtain evidence
responsibility of the user of this standard to establish appro-
on a radiograph that the technique used is satisfactory. It is not
priate safety and health practices and determine the applica-
intended for use in judging the size of discontinuities nor for
bility of regulatory limitations prior to use.
establishing acceptance limits for materials or products.
2. Referenced Documents 3.2.4 intrinsic radiopacity—for this application, where the
plastic is part of a medical device, the X-ray linear absorption
2.1 ASTM Standards:
coefficient is important. The following definition is excerpted
B 209 Specification for Aluminum and Aluminum-Alloy
from Terminology E 7:
Sheet and Plate
3 absorption coefficient—specific factor characteristic of a
D 1898 Practice for Sampling of Plastics
substance on which its absorption radiation depends. The rate
D 3182 Practice for Rubber—Materials, Equipment, and
ofdecreaseofthenaturallogarithmoftheintensityofaparallel
Procedures for Mixing Standard Compounds and Prepar-
beam per unit distance traversed in a substance. For X rays, the
ing Standard Vulcanized Sheets
linearabsorptioncoefficientisthenaturallogarithmoftheratio
of the incident intensity of an X-ray beam incident intensity of
These test methods are under the jurisdiction of ASTM Committee F04 on
Medical and Surgical Materials and Devices and are the direct responsibility of
Subcommittee F04.15 on Material Test Methods. Annual Book of ASTM Standards, Vol 03.01.
Current edition approved Oct. 26, 1979. Published January 1980. Annual Book of ASTM Standards, Vol 03.03.
2 7
Annual Book of ASTM Standards, Vol 02.02. Annual Book of ASTM Standards, Vol 03.05.
3 8
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 03.03.
4 9
Annual Book of ASTM Standards, Vol 09.01. Annual Book of ASTM Standards, Vol 13.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F640
a beam of X rays, I the transmitted intensity, and X the num in accordance with Specification B 209 (typically, 1100
t
thickness of the absorbing material, then: alloy). The comparison standard of Method B (7.1) shall be of
the same metal, unless otherwise specified.
I 5 I exp ~2µX!.
t e
6.4.2 Aluminum Sheet—A10.0 60.15-mmthickaluminum
Here µ is the linear absorption coefficient. The mass absorp-
sheet shall be used on top of the test specimen for all tests. If
tion is given by µ/r where r is the density.
so specified in the standard for the medical device, a 15.0 6
3.2.5 attenuation—loss of energy per unit distance.
0.15-mm thick sheet shall be placed on top of the test
specimen.
4. Summary of Test Methods
6.4.3 Step Wedge—Astepwedgemaybeusedinsteadofthe
4.1 The plastic specimen is laid on the cassette in the Xray
aluminum sheet specified in 6.4.2, if it has the requisite
apparatus and a 10-mm thick sheet of aluminum is placed on
thickness steps.
top of the specimen (or 15-mm thick, if so specified). The
6.5 Rubber Blankets— Blankets incorporating X-ray ab-
apparatus is equivalent to that used in a hospital. Radiographs
sorbers may be used to mask areas outside that covered by the
are made at specified voltages, times, and currents that are
penetrameter (this prevents undercutting). Lead sheets may
typical of those used in the X-ray diagnosis of humans. The
also be used for masking.
radiopacity of the material or medical device is evaluated in
6.6 Back-Scatter Protection, as described in Guide E 94.
terms of the criteria described for the test method selected.
6.7 Densitometer— The densitometer shall be capable of
Calibration is achieved by using both a standard specimen and
measuring the optical density over the range from 0.0 to 3.0
an X-ray optical density standard.
optical density units, minimum. It shall have a measuring
accuracy of 6 0.02 optical density units or better. The
5. Significance and Use
densitometer shall have been calibrated within 6 months
5.1 Plastics, being composed principally of chemical ele-
previously by a method and calibration standard traceable to
ments of low atomic weight, have little opacity to X rays.
the U.S. National Bureau of Standards.
Compounds of elements of higher atomic weight are deliber-
6.8 Step Tablet, for calibrating densitometers.
ately mixed into plastics to obtain radiopacity.
5.2 These methods are intended to determine whether the
7. Comparison Standards
plastic part has the degree of radiopacity specified for its
application as a medical device in the human body. 7.1 Method B—The comparison standard shall be of similar
5.3 Degree of Contrast: dimensions to the medical device. Its exact dimensions and
5.3.1 Using Method A, it is recommended that a specific composition (see 6.4.1) shall be specified in the standard for
difference in optical density between the background of 0.8 to the medical device.
1.2 optical density (3.2.1) and the image of the test specimen 7.2 Method C—The material of the comparison standard
be required in any specification for a radiopaque medical
shall be Type 1100 aluminum (6.4.1), 2.0 mm thick, 25 mm
device. wide, and 150 mm long.
5.3.2 Method B requires that the image of the medical
device, or the image of the section of the medical device that
8. Sampling
is radiopaque, give as much contrast (same background optical
8.1 Sample fabricated stock shapes or molded items in
density as above) as the image of a comparison standard
accordance with Practice D 1898.
simulating the medical device.
9. Test Specimens
NOTE 1—It is expected that the dimensions and composition of the
comparison standard will be specified in the standard for the medical
9.1 Film or Sheet— The specimen shall be at least 150 mm
device (see Appendix X1).
long and 25 6 1 mm wide. (For this specimen and the
5.3.3 In Method C, the intrinsic radiopacity of a plastic is
following it is assumed that the penetrameter covers an area of
determined by comparison with an equal thickness of alumi-
approximately 150 by 50 mm.)
num, and by the calculation of the relative linear X-ray
9.2 Rod or Tubing—The specimen shall be at least 150 mm
attenuation (3.2.5) of the plastic based on measurements of
long.
optical density of the image of the sample, and of the image of
9.3 MoldedParts—Ifthemoldedparthasdimensionssmall
the comparison aluminum piece.
with respect to the area covered by the penetrameter, then
several moldings shall be placed under the penetrameter.
6. Apparatus
9.4 Slab for Method C—The dimensions of the specimen of
6.1 X-Ray Machine, a medical-type (minimally full wave
the pl
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