Biomedical Engineering Reference
In-Depth Information
• Part 3: Guidance on Dosimetric Aspects provides guidance on dosim-
etry for radiation sterilization of health-care products and dosimetric
aspects of establishing the maximum dose (product qualification);
establishing the sterilization dose; installation qualification; opera-
tional qualification; and performance qualification.
ANSI/AAMI/ISO standards describe two methodologies for sterilization
validation:
• Dose setting methods (Method 1 or Method 2, ANSI/AAMI/ISO 11137),
which take into account distribution and radiation resistance of prod-
uct bioburden, and to a limited extent, the end use of the product
• Dose substantiation methods (VDmax methods), which entail exper-
imentation designed to qualify predetermined gamma dosages as a
sterilization dose (1-3)
Table 11.3
summarizes the similarities and differences of the various methods.
Sterility testing of bioprocess systems or components presents significant
challenges because of their large size that may not fit ordinary biosafety cab-
inets for incubation testing. There is also a problem in assuring that the outer
surface does not contaminate the inner surface. Several common approaches
can lessen the difficulties posed by these situations. The Sample Item Portion
(SIP) approach allows for manufacturing and testing a reduced-scale prod-
uct. SIP multipliers can be determined through experimentation or simply
by taking a ratio of the model to the largest system manufactured. The Fluid
Path (FP) testing may be simpler than testing an entire product because a
product acts as its own barrier to contamination. This entails partially filling
the product with a sterile buffer to ensure that all surfaces are wetted, then
agitating the article by hand to promote suspension of organisms into the
buffer. The buffer then is removed and tested for bioburden load through
standard microbiological methods. To aid in handling, a large article can
be split into parts that are more easily manipulated in the laboratory before
testing or irradiation.
