Penn State lab develops new procedures to improve high-quality scanning

Kevin Sliman
May 11, 2020

UNIVERSITY PARK, Pa. — In April, a high-resolution scan from Penn State’s Center for Quantitative Imaging (CQI) was chosen as the cover image for the journal Developmental Dynamics. The image is a 3D segmented rendering of a contrast-enhanced fetal mouse. It appears on the cover of the April 1 volume.

April 2020 Cover of Developmental Dynamics

A high-resolution scan from Penn State’s Center for Quantitative Imaging (CQI) was chosen as the cover image for the journal “Developmental Dynamics.” The image is a 3D segmented rendering of a contrast-enhanced fetal mouse. 

IMAGE: John Wiley and Sons

According to Tim Stecko, a laboratory scientist for CQI, the data for this image is a product of two procedures that CQI researchers, in collaboration with researchers in Joan Richtsmeier’s Lab, helped develop. One was a solution-based staining process that produced more tissue contrast, providing detail-rich images. The second was a wax-mounting protocol that protected and stabilized specimens. Both processes allow for the collection of high-quality, information-dense image data on small, delicate specimens.

Kate Lesciotto, a graduate student in the Richtsmeier Lab, was the researcher who made the illustration and was responsible for much of the wet lab work and image analysis that resulted in the figure.

CQI is home to the GE v|tome|x L300 multi-scale nano/microCT system. It uses X-rays to see inside an object, slice by slice, on an extremely small scale, considerably less than the average width of a human hair. To further enhance the image, the researchers used a solution on this specimen to better see the different parts of the mouse.

“The fetal mouse was stained with a phosphotungstic acid solution, which has varying affinity for different tissues,” said Stecko. “This allows the X-ray CT scans to ‘see’ different structures in the body of these developing mice that we would not otherwise be able to differentiate.”

Additionally, Stecko worked with his CQI colleague Whitney Yetter on a method of determining the progression of the stain in the specimen. By performing fast, low-resolution scans, the researchers could see this process was progressing.

“When you are working on a new procedure like this, you do not have any guidelines to follow, so you have to make your own,” Stecko said.

The other new process was the wax-mounting protocol, which keeps specimens fixed in a motionless position within the mount and prevents dehydration.

“We had the problem of very delicate, soft, wet biological samples,” said Stecko. “And we had to figure out how to handle them and prevent them from drying out. Drying and shrinkage is very real problem when a single scan can last up to 3 hours.”

Stecko said it is very important to maintain these specimens in a state as they are when they are alive because the dimensionality and tissue structures can change as they dehydrate.

The CQI and Richtsmeier Lab researchers started to explore different combinations of low-temperature melting waxes and found a mixture that set well, was good to handle and did not shrink too much. Susan Motch Perrine developed the wax protocol for embedding. 

The combination of staining and the wax process allowed the researchers to mount the mouse embryo and get extremely high-quality images of a digitally dissected specimen.

“This lab is not just using X-ray CT to solve problems for people or provide answers. It is a lab that figures out how to best use X-ray CT,” said Stecko. “That might mean developing new methods of handling and mounting, as we did with the fetal mouse specimens.”

Stecko said that the interdisciplinary nature of CQI allows them to work with experts from a wide variety of disciplines and in doing so, take solutions from one field and pass it along to another.

“There are a number of research labs that use contrast enhancement with X-ray CT,” Stecko said. “What makes CQI unique is the relationship that we have with clients allows us to work closely with each other to develop and improve methods.” 

Because of the broadly applicable CT services that CQI provides, it has clients in every college at Penn State. CQI is also providing X-ray CT solutions to private corporations throughout the U.S.

CQI is a part of the Energy and Environmental Sustainability Laboratories, the core research facilities of the Institutes of Energy and the Environment.

The published paper is titled "Phosphotungstic acid-enhanced microCT: Optimized protocols for embryonic and early postnatal mice" and includes the authors Kate M. Lesciotto, Susan M. Motch Perrine, Mizuho Kawasaki, Timothy Stecko, Timothy M. Ryan, Kazuhiko Kawasaki and  Joan T. Richtsmeier.

Last Updated May 21, 2020