  Two-Photon Laser-Scanning Microscopy is a powerful tool for exploring
biological structure and function because of its ability to optically section
through a sample with a tight focus. While it is possible to obtain 3D image
stacks by moving a stage, this perframe imaging process is time consuming.
Here, we present a method for an easy to implement and inexpensive modification
of an existing two-photon microscope to rapidly image in 3D using an
electrically tunable lens to create a tessellating scan pattern which repeats
with the volume rate. Using appropriate interpolating algorithms, the
volumetric imaging rate can be increased by a factor up to four-fold. This
capability provides the expansion of the two-photon microscope into the third
dimension for faster volumetric imaging capable of visualizing dynamics on
timescales not achievable by traditional stage stack methods.
