| Ultrasound is a unique
quantitative and qualitative tool for evaluating a cosmetic's effect on the skin. With
this technology it is possible to calculate changes in skin thickness and relate this to
product performance. Ultrasound uses high
frequency sound waves to create an image of the skin and its immediate substrate. A high
frequency signal is sent out from the emitting source into the skin. When the sound wave
strikes a tissue it sends out an "echo" and for each tissue layer another
"echo" is created. The size or amplitude of each of these "echoes" in
conjunction with the difference in time it takes for the "echoes" to return to
the emitting source provide the information needed to produce a two dimensional
representation of the skin.
The scanning field of the transducer is 22.4 mm x
22.4 mm and the resolution is, in theory, 0.05 mm axially and 0.3 mm laterally; however,
in reality, due to variations in curvature and thickness in the transducer element the
resolution is slightly less. Once the graph or two dimensional picture has been created it
is possible to see abnormalities in the skin as well as measure the thickness of the
epidermis or for that matter the dermis or subcutaneous fat.
In measuring skin thickness the computer calculates
the distance between two points and provides a measurement of this distance to 0.01 mm.
The thickness of the epidermis and the dermal juncture is determined by matching up and
evaluating the distance between two distinct "echoes" or A scan peaks in the
area that one wants to calculate skin thickness. The skin thickness is calculated for the
test panelists at baseline and various times during product usage. These values are then
compared and the effect of the product on skin thickness and firmness established. I
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