The Technique of Iterative Local Thresholding |
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'TILT' stands for Technique of Iterative Local Thresholding. It is an image processing tool for analyzing 3D x-ray Computed Tomography (xCT) images of fractured media. TILT was designed to address the challenges of (i) characterizing very fine and highly variable apertures, (ii) distinguishing fracture from pores, and (iii) managing large 3D image datasets. TILT combines a novel method for dilation-based masking for local thresholding with a morphological filter for fracture isolation, in an automated and optimized iterative algorithm. For cm-sized samples, TILT is capable of processing images with micron-scale resolution within hours. TILT enables visualization of fractures and quantification of their geometric characteristics. Geometric quantifications such as aperture distribution, total void volume, surface area and roughness can be determined from the binary segmented images produced by TILT. Such characterization enables sound inferences from laboratory experiments.
TILT is presented in this manuscript, which is distributed freely through Open Access License:
H. Deng, J.P. Fitts, C.A. Peters, (2016) 'Quantifying Fracture Geometry with X-ray Tomography: Technique of Iterative Local Thresholding (TILT) for 3D Image Segmentation.' Computational Geosciences. DOI 10.1007/s10596-016-9560-9.
- Download from Springer Link.
- Download PDF.
As a testbed for developing TILT, we used two 3D image datasets from our investigation of permeability evolution in fractured cores of Indiana Limestone, which is a porous rock. In that work, we examined alterations in fracture geometry due to mineral dissolution caused by reactions with CO2-acidifed brine. Those experiments are reported in: Deng H, Fitts JP, Crandall D, McIntyre D, Peters CA. 'Alterations of Fractures in Carbonate Rocks by CO2-Acidified Brines'. Environ Sci Technol 2015;49:10226-10234. DOI: 10.1021/acs.est.5b01980. Through comparison with other image segmentation methods for fractured media, we have shown that the TILT routine is less susceptible to misclassifications and less likely to overestimate fracture void volume.
We welcome and encourage the scientific community to use TILT!
TILT Computational Elements and Workflow
The blue box is the initialization stage, with the dotted arrows illustrating the two steps of initialization: coarse segmentation and fracture isolation. The red box highlights the iterative stage for image segmentation. The red solid arrows illustrate three procedures in a single iteration, and the red dashed arrows show the conditions used to determine continuation or termination of the iterations. In some steps, multiple options are available. The gray box and arrows represent the step for the generation of the fracture template.
Environmental Geochemistry Lab
Department of Civil & Environmental Engineering
Princeton University
Contact: Prof. Catherine A. Peters, Send email to cap@princeton.edu
*Currently at Lawrence Berkeley National Lab
ACKNOWLEDGMENTS. The development of TILT was funded by the National Science Foundation (NSF) Grant CBET-1133849 and by the Department of Energy under Grant DE-FE0023354 to Princeton University (via Penn State University).
Use TILT !
STEP 1. TILT User Registration Form
STEP 2. Access TILT Application files to download Matlab code and example files.
- README file
- MATLAB scripts, functions and codes
- Example data files and mex files
- Example output figures
STEP 4. All use of this code should cite: H. Deng, J.P. Fitts, C.A. Peters, (2016) 'Quantifying Fracture Geometry with X-ray Tomography: Technique of Iterative Local Thresholding (TILT) for 3D Image Segmentation.' Computational Geosciences. DOI 10.1007/s10596-016-9560-9.