Total variation and wavelet regularization methods in emission tomography

A pressure measurement sheet comprises a support and a layer containing microcapsules provided thereon, wherein the ratio of the number average wall thickness ( delta ) to the volume average particle diameter (D) of the microcapsules lies in the range: delta /D = about 1.5 x 10 3 to about 3.0 x 10 2. A method of measuring pressure by the use of the pressure measurement sheet described above comprising the steps of contacting the pressure measurement sheet with the area to be measured, applying pressure to form color and determining the applied pressure from changes in optical densities or hues, where the color is formed through contact under pressure between a layer containing microcapsules and a layer containing an adsorbent.