P.M. Jenneson

An X-ray micro-tomography system optimised for the low-dose study of living organisms

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22keV.A 100mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems. Developing maize seeds (Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 microm, over a diameter of 25mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development.

Examining nanoparticle assemblies using high spatial resolution x-ray microtomography

An experimental system has been designed to examine the assembly of nanoparticles in a variety of process engineering applications. These applications include the harvesting from solutions of nanoparticles into green parts, and the subsequent sintering into finished components. The system is based on an x-ray microtomography with a spatial resolution down to 5μm. The theoretical limitations in x-ray imaging are considered to allow experimental optimization. A standard nondestructive evaluation type apparatus with a small focal-spot x-ray tube, high-resolution complementary metal oxide semiconductor flat-panel pixellated detector, and a mechanical rotational stage is used to image the static systems. Dynamic sintering processes are imaged using the same x-ray source and detector but a custom rotational stage which is contained in an environmental chamber where the temperature, atmospheric pressure, and compaction force can be controlled. Three-dimensional tomographic data sets are presented here for sample...

X-ray tomographic imaging in industrial process control

Abstract Optimisation is essential in modern industrial and chemical process industries to increase efficiency and decrease downtime and maintenance costs. X-ray tomography is being developed to address these issues both on the microscopic level to characterise and quantify unit cell parameters and the macroscopic level for real time measurement of multiphase flow. The behaviour of macroscopic flow can be predicted using finite element simulations. Three-dimensional X-ray micro-tomography with 100 micron resolution has been developed and could be used to determine, for example volume fractions, contact surface area and particle size distribution and used as basic data for modelling of macroscopic systems. Additionally, a high speed X-ray tomography instrument is being developed to measure on-line multiphase flow in fast moving systems. This system does not require moving parts and is expected to operate at up to 50 frames per second. In addition to a practical implementation of this system in an industrial environment it can also be used as a cross-validation of the macroscopic models. Details of each system will be described and the suitability of the applications discussed.

Optimisation of X-ray micro-tomography for the in situ study of the development of plant roots

X-ray micro-tomography is a well-established technique for non-invasive, three-dimensional imaging of heterogeneous materials. A new application for high resolution low-dose tomography is the study of the development of plant roots. A cone-beam tomography system has been designed specifically to image the early development of plant seeds after germination, with a cubic voxel linear dimension of 100 /spl mu/m, over a sample diameter of 25 mm. The X-ray source is a 50 kVp silver target X-ray tube which is quasi-monochromaticaly filtered about the 22 keV characteristic K/sub a/ silver peak. A 10 cm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotating sample table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with 3/sup rd/ generation tomography systems. Developing wheat seeds (Triticum aestivum) have been imaged using the system and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the development of plant root.

Optical CT scanning of PRESAGE™ polyurethane samples with a CCD-based readout system

This article demonstrates the resolution capabilities of the CCD scanner under ideal circumstances and describes the first CCD-based optical CT experiments on a new class of dosimeter, known as PRESAGE™ (Heuris Pharma, Skillman, NJ).

In situ x-ray imaging of nanoparticle agglomeration in fluidized beds

A high spatial (down to 400 nm) and temporal resolution (down to 1 ms) x-ray imaging apparatus has been designed to study the agglomeration of arc plasma synthesized zinc oxide nanoparticles (average diameter of 50 nm) in fluidized beds under different gas flow velocities. The mean volume distribution of the nanoparticle agglomerates was determined with x-ray microtomography and found to correspond to a lognormal distribution with a mean value of 0.70×109μm3 and a variance of 3.6×1021 (μm3)2. The average density of the agglomerates was found to be 2.9gcm−3 compared to 5.6gcm−3 for the individual nanoparticles. The powder assembly was then dynamically imaged using an x-ray image intensifier coupled to a digital camera using a field of view of 24.20 mm by 32.25 mm and a temporal resolution of 40 ms. Sequential frames were captured into computer memory for a range of gas flow velocities from 0.026ms−1 to 0.313ms−1. The breakup energy of the agglomerates was calculated to be approximately 2×10−8J using a comb...

Metal deposition at the bone-cartilage interface in articular cartilage

There is a growing interest being shown in the changes occurring in elemental distribution at the bone-cartilage interface, the changes either being a result of mechanical damage or disease. In particular, such investigations have tended to concern the elemental alterations associated with the osteoarthritic wear and tear damage occurring to the cartilage and subchondral bone of synovial joints or that associated with disease processes such as rheumatic arthritis. Present studies examine sections of femoral head obtained from total hip replacement surgery, use being made of micro-proton-induced X-ray emission (micro-PIXE) and the Rutherford back scattering (RBS) techniques. Enhancements of Zn, Ca and P have been observed at the bone-cartilage interface. Further, the concentration of Zn in spongy bone underlying the subchondral surface of a section of the femoral head has been measured, obtaining 136 microg g(-1) bone, the presence of Ca and P at the same position being 0.235 and 0.0451 g g(-1) bone, respectively. These values are slightly different to figures recently published by other authors using similar techniques.

Electronically gated multiemitter x-ray source for high-speed tomography

High speed X-ray tomography is being developed for on-line measurement of multiphase flow for well management in the oil industry. To reduce motion artifacts to acceptable levels a source is required that can scan about a 100 mm diameter pipe in approximately 20 ms, thus rendering a rotating source an impractical solution. In order to achieve a spatial resolution of 2 mm in the reconstructed image a total of 105 individual projections over a 210 degree arc are required. The large number of point sources means individual X-ray tubes are not practicable. Our solution is to use multiple electron beams where the active focal spot can be rapidly scanned across the target in an arc about the pipe with the use of electronic grids. This paper describes a prototype of such a tube designed, in the first instance, to cover a 30 degree arc and consisting of 13 individual emitters. Having proved the principle of operation a full system is now in the design stage and shall be briefly discussed.

RadBall: A new departure for 3-D dosimetry

This paper describes a new device, RadBall™ for mapping environmental radiation fields, as found in the area of nuclear decontamination. The system consists of a specially shaped PRESAGE™ dosimeter, which sits inside a custom-designed lead collimator. This is imaged using optical CT to yield data from which the position of either point sources or extended objects may be reconstructed. The principle of the technique is explained, simulations and preliminary data are given and the current design of the dosimeter and collimator are presented.

Three-dimensional optical tomography of dose distribution using radiation sensitive transparent gels

The ability to determine the absorbed dose distribution in tissue is essential for radiotherapy planning. A three-dimensional optical tomography system used to map dose distribution and the radiation sensitive transparent gel (Ferrous Sulphate Xylenol orange in Gelatin gel) used are described. The system is capable of collecting two-dimensional projections and hence able to reconstruct three-dimensional dose maps. The equipment used is inexpensive and readily available offering an alternative to the magnetic resonance imaging of three-dimensional dose distributions. The FXG gel used undergoes the greatest change in optical density at 590 nm (the wavelength produced by a sodium lamp) when exposed to an ionising radiation. We have shown the change in optical density is directly proportional to the absorbed dose up to 20 Gy. A three-dimensional dose map imaged by the system shows the expected cone-beam of dose produced by a 50 kVp silver anode X-ray tube.