X-rays scanner

The scanner makes it possible to reconstruct a 3D image of a patient or sample subjected to an X-ray scan by analysing the attenuation of the rays as they pass through the object. X-rays are a form of high-frequency electromagnetic radiation, with wavelengths ranging between 5 picometers and 10 nanometers. They were discovered in 1895 by German physicist Wilhelm Röntgen. X-rays can be generated in several ways. In our scanner, they are produced through electron acceleration: electrons are extracted from a cathode and accelerated toward an anode by an electric potential inside a vacuum tube. When the electrons are decelerated upon striking the anode atoms, radiation is emitted.

Our equipment is a General Electric Brightspeed Exel X-ray scanner (4-slice).

Le statif est l'« anneau » constituant la partie mécanique du scanner associé à la table motorisée. Il pèse 1525kilos, dont plusieurs centaines de kilos en rotation à 2 tours/seconde lors des mesures. La table motorisée pèse 335 kg.
Les scans réalisés ont un diamètre allant de 9,6 cm à 50 cm, et la longueur maximale est d'environ 1,5 mètre.
La table accueillant les échantillons supporte un poids de 205 Kg en motorisation. Cependant, entre 180 et 205Kg, la précision des mesures se trouve réduite à +/- 1 mm, contre 0,25mm pour un poids inférieur à 180Kg.

The gantry — the “ring” forming the scanner’s mechanical structure — is paired with a motorized table. It weighs 1,525 kg, several hundred kilograms of which rotate at 2 revolutions per second during acquisition. The motorized table itself weighs 335 kg. Scans can be performed on diameters ranging from 9.6 cm to 50 cm, with a maximum sample length of about 1.5 meters. The table supports up to 205 kg in motorized mode. However, between 180 and 205 kg, measurement accuracy decreases to ±1 mm, compared to 0.25 mm for samples under 180 kg.

Two acquisition modes are available: 

• Axial mode: sectional images of the sample are acquired while the table remains still, moving only between scans. X-ray emission is intermittent
• Helical mode: the table moves continuously throughout acquisition, with constant X-ray emission
   

The table below summarizes the adjustable parameters and their ranges for both modes:

Acquisition time per slice influences image resolution: if too short, images may appear noisy. In axial mode, scanning speed is about one meter per minute (slower, but allowing more accurate volumetric reconstruction). Slice thickness affects spatial resolution and depends on detector configuration: 4×3.75 mm, 4×5.0 mm, 1×1.25 mm, and 2×0.625 mm. The first number indicates the number of detectors, the second their thickness. The interval corresponds to the distance between slices. Voltage determines the penetration power of X-rays, while current is related to flux.

Wood density is a fundamental and highly variable property, linked to dry biomass and water content in the tissue or material.

Analysing density variations across scales is a key expertise in all our activities. X-ray–based technologies enable reliable, high-throughput measurements. Tomography provides non-invasive 3D acquisition of structures, from cubic millimeters to whole logs.

Our service includes scan acquisition and data archiving. Results are delivered as image series in .dcm (Dicom) format, provided on your external hard drive, on a CD, or via a download link (depending on data volume).

Within our facility, study topics include wood density mapping, moisture distribution, and growth analysis through branch trace detection (branches, buds).

This investigation method applies to a wide range of non-metallic materials with density variations.

Examples of scanned study objects: statues and archaeological artefacts, soil samples, cheese wheels, mussel shells, composite materials.

Contact:

• Equipment coordinator: Charline Mola charline.mola@inrae.fr 
• Unit coordinator: Julien Ruelle julien.ruelle@inrae.fr