Interference No. 104,290
device. It is this qualitative difference that would demand an
in vivo test.
Hansen also stated, and we find credible, that in vitro
testing can be useful for comparing performance of a prior art
device, whose ablation characteristics are known, to a new device
whose ablation characteristics are not known, before clinical
testing. However such an in vitro test must approximate the
impedance characteristics of a living organism. EX-5153, 114.
Hansen testified that one medically acceptable manner of testing
that approximates impedance is to place the organ of choice on an
insulated plate and immerse the plate in an electrolyte solution
buffered to the approximate impedance of a human body. Id.
Hansen also testified that the in vitro tests of a
static explanted liver neglected to account for the heat
sink/blood circulation cooling effects of an organ in a living
organism. This effect results from the fact that blood flowing
through the heated tissue carries away the rf generated heat,
much as an automobile's coolant carries heat from the engine
block to the radiator. Hansen mentioned that this effect was
recognized in the prior art including the McGahan publication.
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