Table 5 presents medical device categorization by body contact and contact duration. The tissue contact categories and subcategories, as well as the contact duration categories, have been derived from standards, protocols, and guidelines utilized in the past for safety evaluation of medical devices. Certain devices may fall into more than one category, in which case testing appropriate to each category should be considered. The ISO10,993 standard and the FDA guidance document present a structured program for biocompatibility evaluation in which matrices are presented that indicaterequiredtestsaccordingtospecifictypesoftissuecontactandcontactduration. These matrices are not presented here but the in vivo tests are indicated in Table 6.