Jennifer A. Griffiths

A non-free-space propagation x-ray phase contrast imaging method sensitive to phase effects in two directions simultaneously

We present an x-ray phase contrast imaging method based on coded apertures sensitive to phase effects in two directions simultaneously. To date, this is the only non-free-space propagation approach with this capability. Whereas the use of free-space propagation methods is limited to synchrotron radiation or microfocal x-ray sources, which impose severe limits in terms of practical applicability, coded-aperture based methods have been shown to provide synchrotronlike phase contrast enhancements with conventional x-ray sources. A two-directional sensitive method working with conventional sources could create a breakthrough in medical imaging, where two-directional sensitivity is often a mandatory requirement.

Correlation of energy dispersive diffraction signatures and microCT of small breast tissue samples with pathological analysis

Identification of specific tissue types in conventional mammographic examinations is extremely limited. However, the use of x-ray diffraction effects during imaging has the potential to characterize the tissue types present due to the fact that each tissue type produces its own unique diffraction signature. Nevertheless, the analysis and categorization of these diffraction signatures by tissue type can be hampered by the inhomogeneous nature of breast tissue, leading to categorization errors where several types are present. This work aims to reduce sample categorization errors by combining spectral diffraction signature collection with sample imaging, giving more detailed data on the composition of each sample. Diffraction microCT was carried out on 19 unfixed breast tissue samples using an energy resolving translate-rotate CT system. High-resolution transmission microCT images were also recorded for comparison and sample composition analysis. Following imaging, the samples were subjected to histopathological analysis. Reconstructing on various momentum transfer regions allows different tissue types to be identified in the diffraction images. Results show a correlation between measured x-ray diffraction images and stained histopathological tissue sections. X-ray diffraction signatures generated from the measured data were categorized and analysed, with a t-test indicating that they have the potential for use in tissue type identification.

Preliminary estimates of the calcium/phosphorus ratio at different cortical bone sites using synchrotron microCT.

The Ca/P ratio was measured in cortical bone samples from the femoral neck, front and rear tibia of female rats (1.5 years of age), using synchrotron radiation microtomography. The use of a monoenergetic x-ray beam, as provided by the synchrotron facility, generates accurate 3D maps of the linear attenuation coefficient within the sample and hence gives the ability to map different chemical components. Data sets were taken at 20 keV for each bone sample and calibration phantoms. From the 3D data sets, multiple 2D slices were reconstructed with a slice thickness of approximately 28 microm and converted to Ca/P ratios using the calibration phantom results. Mean values (M +/- SD) for cortical femoral, front and rear tibias are 2.12 +/- 0.08, 1.75 +/- 0.06 and 1.94 +/- 0.07 respectively. These values were compared with those derived from different animals. Differences between the same bone sites from different animals are not significant (0.1 < p < or = 0.9) while those between different bone sites are highly significant (p < 10(-3)) demonstrating a dependence upon life style and bone use.

Diffraction enhanced breast imaging: preliminary results from the Elettra synchrotron source

Biological tissues cause X-ray diffraction effects indicative of the tissue being Irradiated. These effects can be used as the physical mechanism to obtain images of the tissues. In our work at UCL we have demonstrated that there is a detectable difference in the shape of the X-ray diffraction profile from healthy and diseased breast tissue. We are currently working towards translating this concept into a feasible clinical imaging system, which will take transmission images and diffraction enhanced images of the breast simultaneously.. A prototype diffraction enhanced imaging system has been developed and undergone preliminary testing at the Elettra synchrotron radiation source at Trieste, Italy. The imaging system is based upon new low light level CCD (L3 Vision) technology, which exhibits low noise characteristics and a greatly improved sensitivity The camera consists of a suitably collimated, cooled L3Vision sensor coated with a Gd/sub 2/O/sub 2/S:Eu phosphor screen. Results demonstrated that the camera could detect single X-ray photons. A 4 cm thick phantom, consisting of excised normal and cancerous human breast tissue, was imaged at the Elettra SYRMEP beamline by diffraction and transmission techniques. Diffraction images were obtained at the momentum transfer value optimal for tissue discrimination. Additional momentum transfer values were also investigated. Results demonstrated a significant increase in image contrast in the diffraction images compared to the transmission images. It is also suggested that the use of additional momentum transfer values could further increase contrast and improve discrimination among tissue types.

Illicit drug detection using energy dispersive x-ray diffraction

Illicit drugs are imported into countries in myriad ways, including via the postal system and courier services. An automated system is required to detect drugs in parcels for which X-ray diffraction is a suitable technique as it is non-destructive, material specific and uses X-rays of sufficiently high energy to penetrate parcels containing a range of attenuating materials. A database has been constructed containing the measured powder diffraction profiles of several thousand materials likely to be found in parcels. These include drugs, cutting agents, packaging and other innocuous materials. A software model has been developed using these data to predict the diffraction profiles which would be obtained by X-ray diffraction systems with a range of suggested detector (high purity germanium, CZT and scintillation), source and collimation options. The aim of the model was to identify the most promising system geometries, which was done with the aid of multivariate analysis (MVA). The most promising systems were constructed and tested. The diffraction profiles of a range of materials have been measured and used to both validate the model and to identify the presence of drugs in sample packages.

Diffraction enhanced breast imaging: assessment of realistic system requirements to improve the diagnostic capabilities of mammography

A detectable difference in X-ray diffraction data of healthy and diseased breast tissues has been observed. This information can be used to generate images with a higher contrast than that of conventional transmission mammography. A diffraction enhanced breast imaging (DEBI) system that simultaneously combines transmission and diffraction breast images is currently being developed. This paper presents the imaging system requirements for a clinical DEBI system. The DEBI imaging system employs a phosphor coated L3Vision CCD camera. The DEBI principle has been assessed at the SYRMEP synchrotron beamline (Elettra, Trieste) and with a purpose built mammographic X-ray imaging unit. Diffraction enhanced images have been obtained of realistic breast tissue phantoms, consisting of 4 cm thick slabs of excised breast tissue containing embedded carcinomas. The images were obtained at pre-determined momentum transfer values, allowing some tissue characterization to be achieved during imaging, as well as optimizing image contrast This paper presents the current state of the project. The spatial resolution of the diffraction images have been studied using test phantoms and suggestions are made for the collimation systems necessary for a clinical system. A correction procedure applied to the diffraction images is also presented.

X-ray diffraction CT of excised breast tissue sections: first results from Elettra

The scattering properties of breast tissue have been suggested as a diagnostic tool in the early detection of breast cancer. To aid in the development of a clinical imaging system based upon these properties, a series of breast tissue samples have been subjected to diffraction microCT using the SYRMEP beamline at Elettra, Italy. Using 18 keV photons, both transmission and diffraction CT data sets were collected using a specially designed microCT system. This system was based around a finely collimated, X-ray sensitive L3Vision CCD camera and a simple rotary stage controlled using Lab View software. The images were reconstructed using routines developed in IDL. This paper presents both transmission and diffraction CT images of three samples. The samples were excised breast tissue sections known to contain either tumour, normal tissue adjacent to the tumour or a mixture of each. The results demonstrate that diffraction microCT can be used to evaluate the structure of breast tissue tumours. Registration of the transmission and diffraction CT images demonstrated that both techniques showed the same principle features in the sample and allowed the main components to be identified. However, the diffraction images demonstrated an average increase in image contrast over the transmission images. Further improvements in the collimator design used in the experiments will need to be made if detailed structure is to be seen.

Proposal of a novel Diffraction Enhanced Imaging setup based on polycapillary X-ray optics

Diffraction Enhanced Imaging (DEI) is a recent technique developed to improve the diagnostic capabilities of radiography by exploiting coherently scattered X-rays to generate images that provide higher contrast than conventional transmission imaging. Earlier experiments, carried out in the synchrotron environment using a mechanical parallel-hole collimator coupled to a 2D X-ray imager, confirmed the potential of this technique in mammography. The main limitations of DEI come from the detection system, the requirement of the synchrotron source and the use of a mechanical multi-hole collimator, which limits the achievable spatial resolution and also increases the acquisition time. New developments in polycapillary optics technology and in 2D detectors enable a significant upgrade of DEI setups. In order to handle the above mentioned limitations, a microfocus X-ray tube coupled to a polycapillary semi-lens, was used to deliver a collimated X-ray beam. A second polycapillary lens for the angle selection was coupled to the detector to achieve high spatial resolution. The detector was upgraded to the Controlled Drift-Detector (CDD), a novel 2D X-ray imager with energy resolving capability of spectroscopic quality. This paper introduces this novel setup and presents the results of its experimental qualification. Images of phantoms both in transmission and in diffraction modes will be presented to evaluate the system performance.

Adaptive Imaging Using the I-ImaS X-Ray Imaging System

The I-ImaS (intelligent imaging sensors) is an European Union project whose objective is to design and develop intelligent imaging sensors and evaluate their use within an adaptive imaging system. The system employs an in-line scanning technology approach and use of CMOS active pixel sensors developed specifically for high spatial resolution, efficient light collection and large dynamic range. This paper discusses the principle of the data acquisition (DAQ) system and the characterisation of the I-ImaS sensors, both optically and using mono-energetic X-rays.

A Multi-Element Detector System for Intelligent Imaging: I-ImaS

I-ImaS is a European project aiming to produce new, intelligent X-ray imaging systems using novel APS sensors to create optimal diagnostic images. Initial systems concentrate on mammography and encephalography. Later development will yield systems for other types of radiography such as industrial QA and homeland security. The I-ImaS system intelligence, due to APS technology and FPGAs, allows real-time analysis of data during image acquisition, giving the capability to build a truly adaptive imaging system with the potential to create images with maximum diagnostic information within given dose constraints. A companion paper deals with the DAQ system and preliminary characterization. This paper considers the laboratory X-ray characterization of the detector elements of the I-ImaS system. The characterization of the sensors when tiled to form a strip detector will be discussed, along with the appropriate correction techniques formulated to take into account the misalignments between individual sensors within the array. Preliminary results show that the detectors have sufficient performance to be used successfully in the initial mammographic and encephalographic I-ImaS systems under construction and this paper will further discuss the testing of these systems and the iterative processes used for intelligence upgrade in order to obtain the optimal algorithms and settings.