Tomography – imaging by sections
Greek – tomos means section/slice/cutting
Radiation source
Type of tomograph
X-rays
CT (computed tomography)
gamma rays
SPECT (single photon emission
tomography)
electron-positron annihilation
PET (positron emission tomog.)
nuclear magnetic resonance
MRI (magnetic resonance
imaging)
ultrasound
ultrasonography
electrons
3D TEM
ions
atom probe
Three dimensional imaging in TEM
Serial
Sectioning
Alignment of adjacent
sections is one of the
most difficult aspects of
serial reconstruction
Registration points are
often used to assist
alignment (registration)
Electron Tomography
Electron Tomography
An object viewed from many different angles
will generate slightly different images.
Object creates multiple images so
the inverse is also possible
These images can be recorded and analyzed to
create a tomographic rendering of the
specimen.
It is computationally
easier to carry out the
calculations in Fourier
space than it is in
image space.
Single reverse FFT
-can enhance symmetry
M.ultiple images can be
generated in one of two
ways:
1) A single object can tilted
and viewed from many
different angles.
2) A field of randomly
oriented identical objects
can be image in a tilt
pair.
Electron Tomography
Double tilt holder
Gatan cryo-holder allows samples to be
placed into the TEM while being kept
frozen at LN temperatures
Solid models
constructed from
various views