X-ray CT Scanner

Conventional x-raying of materials is a well known technique in soil and geosciences. Nevertheless, the preparation of appropriate slabs for this type of investigation is laborious - and what is more important - destructive.
Computerised Tomography (CT), originally developed for medical purposes, has several advantages:

• it is non-destructive
• it is rapid
• it provides a digital dataset of the density variations in the sample/core
• it has high-resolution capabilities in the range of mm to cm

Applications of Computerised Tomography include:

• Cored or sub-sampled sediments and soils
• Pressurized cores in autoclave vessels, which are translucent for X-ray
• Samples of carbonate, either drilled or chunks
• Samples that are deep frozen
• Offers many additional opportunities for novel insights into samples

At the MARUM the opportunity to use a General Electric CT Prospeed SX scanner mounted in a road semi trailer is available:

• Scout scan (single radiographic plane/overview scan) up to 500 mm length
• 1, 3, 5 or 10 mm slice thickness
• 25, 35, 42 or 50 cm scan fields of view
• Single slice and helical scanning
• Data output DICOM compatible
• Data storage via LAN on CD or hard disk

X-ray computerized tomography data are imaged with the professional visualization software AMIRA®. It is a professional general-purpose visualization and 3D reconstruction software. The software is capable of displaying large data sets (on the range of tens of Gigabytes), notably 3D image data, vector fields, and finite element data. With the software Marum scientists are able to create polygonal 3D reconstructed surface models as well as tetrahedral grids from 3D image data.

The sediment core data analyzed by computer tomography can be quickly explored, analyzed, compared, and quantified. 3D objects can be represented as image volumes or geometrical surfaces and grids suitable for numerical simulations, notably as triangular surface and volumetric tetrahedral grids. AMIRA® provides methods to generate such grids from voxel data representing an image volume, and it includes a general-purpose interactive 3D viewer. The 3D reconstruction is carried out in close collaboration with the department of Geosciences at the University of Mainz, Germany.
Scientists are able to display discrete elements of a sediment core or any other composite material, as the absorption of different materials can be displayed individually. That allows for imaging the distribution of certain compounds, such as carbonates (e.g., corals) in a sediment matrix of a different mineralogical composition.

The DICOM data format is widely used to exchange medical image data, and is also used at the Marum CT scanner. DICOM stands for Digital Imaging in Communications and Medicine, and it was originally designed as pure transfer format between imaging modalities and image retrieval. The data files have a so-called tagged format, with a variable amount of tags (DICOM data elements), which means that a sediment core can be segmented into several small parts and later be integrated to large data sets. Each element is defined by a unique group-element identifier, such as IODP codes or GeoB numbers, referring to cruises, legs or sampling stations. These group-element pairs are always sorted in ascending order within the DICOM data stream.