The Grinding Imaging and Reconstruction Instrument

Tuesday, Jun 25, 2013

GIRI will be able to find hidden fossils in samples such as this one, collected from the Trezona Formation in South Australia. (Image courtesy of Adam Maloof.)Not far from the 100-year-old Guyot Hall geosciences building stands Princeton's newest construction project, the Grinding Imaging and Reconstruction Instrument (GIRI) lab. Funded by the National Science Foundation, the GIRI lab opened in Feb. 2013 and is dedicated to the digital reconstruction of objects hidden in solid materials.

GIRI automates the task of grinding and imaging materials such as stone and metal, allowing researchers to use the images to reconstruct 3D models of complex forms hidden in these materials.

The inspiration for GIRI arose in 2009 after Princeton geosciences professor Adam Maloof and graduate student Catherine Rose discovered strange red flecks and blobs in the Trezona Formation in South Australia. The researchers suspected that the red shapes were important, but because the fossils and the surrounding rock were of the same material, the researchers couldn't analyze the samples with typical techniques such as x-rays or acid-dissolutions. Instead, the investigators ground away a very thin layer of the fossil, took a picture of the surface, then removed another layer, and took another picture. After 500 repetitions of this process, Maloof and his colleagues combined the images to construct a three-dimensional model of the fossil, a sponge-like organism thought to be the oldest fossil animal ever discovered.

Three-dimensional reconstruction of a Trezona fossil, interpreted as a sponge-grade organism. (Image courtesy of Adam Maloof.)

With GIRI, which was developed in collaboration with the technology and design firm SITU Studio, this laborious process has been automated so that fossils can be quickly processed using serial sectioning and imaging. A precision grinder removes small layers of material, then an integrated 80-megapixel camera takes high resolution images of the layer. A computer then analyzes the color and textural information to find complex structures and objects, and combines hundreds of segmented slices to create 3D models. From the models, researchers can deduce the porosity and permeability of the original sample. The models also can be used for hydrodynamic simulations, morphological analysis, and a variety of other computational simulations and analyses.

Some of the initial projects for GIRI include the digital reconstructions of early animal fossils, 3D sedimentary bedforms, chondritic meteorites and targets for geological carbon sequestration.

This video shows how serial grinding and imaging can review the internal structures hiddle in a sample of rock. (Image courtesy of Adam Maloof.)