Methods for specimen thickness determination in electron microscopy.

A new method is described for specimen thickness determination in transmission electron microscopy. This is carried out by marking specimens with gold particles and analysing the images of a tilt series by computer. The method makes it possible to distinguish populations of particles on different planes and calculate the distance between the planes with statistical variation. We have applied it to carbon films as test objects and compared the results with those obtained by transverse sectioning, STEM mass measurement, optical density and frequency change of a quartz crystal oscillator. We have then used the method for thickness measurement of multilayered protein crystals and thin sectioned cells.