NSLS-II Seminar

Imaging of biological material, such as a whole cell, in three dimensions will deepen our
insight into cellular biology. This requires high-resolution imaging of samples as close as
possible to their natural state without introducing structural artifacts by staining or
sectioning, or by radiation damage. Currently, x-ray microscopy based on a zone plate
(scanning transmission x-ray microscopy (STXM) and transmission x-ray microscopy
(TXM)) provides high-resolution imaging that benefits from the short wave length and
high penetration length of x-rays. Due to this direct imaging using a lens, x-ray
microscopy yields high throughput as well as spectroscopy and elemental mapping of the
sample. However, as higher resolution lenses are sought in the future, the intrinsic
limitations of optical lenses, such as short depth of field, will become problematic with
biological samples of a-few-micron thickness. Coherent diffraction imaging (CDI), where
image reconstruction is done through a computational lens (reconstruction algorithm),
can be complementary to current x-ray microscopy. The resolution of the microscope is
determined not by a lens, but by the largest angles at which scattered radiation from the
sample can be detected and the convergence of the reconstruction algorithm. Currently
the CDI method in biological imaging is still under development since obtaining highquality
data for reconstruction is hindered by the fact that biological samples are weak
scattering. In this talk, I will present the progress of biological CDI using soft and hard xrays
with challenges and possible solutions. The future of x-ray biological imaging might
be found in the combination of two methods, for example, STXM and CDI, to provide
direct imaging and improved resolution.