Micro-Computed Tomography Core

Research

Introduction

The micro-computed tomography (microCT) core provides high-resolution assessments of geometry, architecture, and material of mineralized tissues such as bones and teeth or of soft tissues stained with radiographic contrast media. Resolutions are typically less than 40 microns.  MicroCT has been used successfully in many research studies including the following: phenotype characterization in mouse models, animal and human specimens from disease states, and interventional studies.


Figure 1: Human iliac crest biopsies

Instrumentation

The primary equipment consists of an Enhanced Vision Systems (EVS) Model MS-8 In Vitro MicroCT Scanner (GE Healthcare, Pre-Clinical Imaging).  This equipment has the following specifications: 8 to 100 microns isotropic resolutions, up to (30 mm)3 imaging volume, volumetric conebeam acquisition, and quantitative image analysis. Volumetric conebeam scanning captures the entire volume of a sample in one rotation rather than slice-by-slice. It produces data sets with isotropic resolutions, in which the slice thickness equals the axial resolution. In addition, it is much faster than conventional single slice computed tomography. Scan times depend on the resolution; typical scans for an isotropic resolution of 40 microns take approximately 1 hour. Quantitative image analysis allows the determination of not only architecture but also density.  Linearity and quantitative values are established by scanning a phantom containing several densities of a given calibration material. The mean CT numbers within each calibration material are plotted with their corresponding densities.  Our phantom is composed of air, saline, and SB3 - a cortical bone mineral reference standard.


Figure 2: Micro-Computed Tomography Equipment

Specimen Preparation

Specimens must be less than 30 mm in diameter and 30 mm in length to fit in the holder of the scanner. This restriction is typically not a difficulty in studies of small laboratory animal specimens or human biopsies. If a specimen is larger than these dimensions, dissection or machining is necessary.  Scanning is performed on specimens in solutions (e.g., saline, alcohol) or embedded in resins.  The main requirement is that the embedding media have X-ray attenuation properties different from mineralized tissue so that mineralized tissue can be segmented from background.  Holders are available for mouse and rat bones and for human iliac crest biopsies. Other holders can be designed and manufactured on request.

Measurements

Cancellous bone volume fraction:  Reconstructed grayscale images are thresholded to separate mineralized tissue and background voxels. The threshold approach depends on the research question and is decided on by consultation with the core director and staff.  For example, the threshold technique could employ one of the following: a threshold defined for each individual data set based on the underlying attenuation histograms; a threshold determined in a subset of ashed specimens; or a single global threshold. The volume fraction of mineralized tissue is calculated as the number of voxels above the threshold divided by the total number of voxels.


Figure 3: Thresholded image of human iliac crest biopsy

Mineral content and density:  Attenuation values are converted to mineral content (in mg) and density (in mg/cc) based on the linear relationship from the phantom and integrated to obtain the mineral content or density of a volume of interest.


Figure 4: MicroCT image of mouse tooth demonstrating volume of interest used to determine mineral content

Whole long bone and diaphyseal properties: Bone length and total mineral content can be determined for small animal bones that fit within the scanner. Cross-sectional area and moments of inertia of cortical bone are determined from microCT of small animal long bones such as the ulna, femur, and tibia. Principal area moments of inertia are directly computed for every cross-section by integration of the product of each bone pixel area and the square of pixel distance about orthogonal axes of a given cross-section. Custom software that uses MatLab is available to obtain geometric properties. 


Figure 5: MicroCT analysis of rodent femur showing diaphysis and cross section

Additional measurements:  New measurements can be developed as part of the Core activities on an as-needed basis.


Figure 6: Experimental analysis of engineered mineralized tissue in a bone chamber

Fee Schedule

  • NIH-funded Users
    Instrument: $75/hour (Computer usage for Data Analysis is free of change)

  • Core Services for NIH-funded Users
    Instrument: $75/hour
    Data Analysis: $75/hour
    Instrument and Data Analysis Training: $125/hour

  • Non-NIH funded Academic Users
    Instrument: $100/hour (Computer usage for Data Analysis is free of change)

  • Core Services for non-NIH funded Academic Users
    Instrument: $100/hour
    Data Analysis: $100/hour
    Instrument and Data Analysis Training: $150/hour

  • Industry Users
    Please inquire!

Contact Information

Note: Publications that include data generated using the services of the Imaging Core must acknowledge support through NIH AR046121.

General Inquiries and New Users
Philipp Mayer-Kuckuk, PhD
email: mayerkuckukp@hss.edu
Phone: 212.606.1082

Technical Assistance and Scheduling
Lyudmila Lukashova
Email: lukashoval@hss.edu
Phone: 212.606.1740
Fax: 212.774.7877

Link to MicroCT Calendar

http://groups.yahoo.com/group/microct_users/
You must become a member before access is available. Contact Core personnel.