9 research outputs found
Monte Carlo Simulation for Polychromatic X-ray Fluorescence Computed Tomography with Sheet-Beam Geometry
X-ray fluorescence computed tomography based on sheet-beam can save a huge
amount of time to obtain a whole set of projections using synchrotron. However,
it is clearly unpractical for most biomedical research laboratories. In this
paper, polychromatic X-ray fluorescence computed tomography with sheet-beam
geometry is tested by Monte Carlo simulation. First, two phantoms (A and B)
filled with PMMA are used to simulate imaging process through GEANT 4. Phantom
A contains several GNP-loaded regions with the same size (10 mm) in height and
diameter but different Au weight concentration ranging from 0.3% to 1.8%.
Phantom B contains twelve GNP-loaded regions with the same Au weight
concentration (1.6%) but different diameter ranging from 1mm to 9mm. Second,
discretized presentation of imaging model is established to reconstruct more
accurate XFCT images. Third, XFCT images of phantom A and B are reconstructed
by fliter backprojection (FBP) and maximum likelihood expectation maximization
(MLEM) with and without correction, respectively. Contrast to noise ratio (CNR)
is calculated to evaluate all the reconstructed images. Our results show that
it is feasible for sheet-beam XFCT system based on polychromatic X-ray source
and the discretized imaging model can be used to reconstruct more accurate
images
Design, Development and Investigations of a Novel X-ray Fluorescence and X-ray Luminescence Computed Tomography System for Theranostic Applications
Il presente lavoro di tesi riguarda il progetto, la costruzione, lo sviluppo e la sperimentazione di un sistema innovativo di imaging tramite tomografia computerizzata per fluorescenza a raggi X e luminescenza a raggi X (XFCT/XLCT). Tale sistema ha lo scopo di indagare su possibili applicazioni di tale tecnologia a scopi teragnostici, ovvero combinando diagnostica e trattamento terapeutico. Un esempio di tali applicazioni è la terapia fotodinamica a raggi X. I principali agenti teragnostici indagati con tale sistema si basano su nanotecnologia medica. L’utilizzo di raggi X per stimolare l’emissione di fluorescenza e luminescenza a raggi X permette un tipo di terapia selettiva e altamente localizzata, con la possibilità di usare tali radiazioni anche per monitorare il trattamento in tempo reale. Il sistema XFCT/XLCT dimostra eccellenti capacità di risoluzione spaziale (200 micron), sensitività (300 microgrammi/mL) e imaging multicolore e multimodale, altamente promettenti per sviluppi commerciali futuri e applicazioni precliniche.
The current thesis work regards the design, the development, the construction and the investigations on a novel imaging system implementing X-ray Fluorescence and X-ray Luminescence Computed Tomography (XFCT/XLCT). Such system has the main purpose of investigating on potential applications of such technology for theranostics, i.e. the combination of diagnosis and therapeutic treatment. An example of such applications is X-ray Photodynamic Therapy. The primary theranostics agents tested with such system are based on medical nanotechnology. The use of x-rays for stimulating the emission of x-ray fluorescence and x-ray luminescence would permit a kind of selective and highly localized therapy, with the possibility to employ such radiation also for the monitoring of the treatment in real-time. The XFCT/XLCT system demonstrates excellent capabilities of spatial resolution (200 micron), sensitivity (300 micrograms/mL), and multimodal and multi-coloured imaging, which are highly promising for future commercial developments and preclinical applications
A feasibility evaluation of x-ray fluorescence emission tomography and x-ray luminescence tomography for real-time assessment of photodynamic therapy
Photodynamic Therapy (PDT) has found use in a wide-array of clinical applications such as in
cancer and acne treatment. Photodynamic therapy, uses a photosensitive compound activated by a
specific wavelength photon to produce cytotoxic oxygen species (either in free radical form or in
singlet form). However, weak penetration of visible, infrared, and UV light into the body to
activate the photosensitive compound significantly limits the use of PDT in cancer treatment.
Additionally, PDT current lacks an effective dosimetry technique or means of quantifying the
number of activated photosensitizers for investigative studies has proven difficult as well. Many
researchers have delved into investigating x-ray induced PDT, which in combination of x-ray
fluorescence computed tomography (XFCT), can produce a quantifiable therapeutic effect at
greater bodily depths. This work demonstrates a novel combinatorial system of X-ray Fluorescence
and X-ray Luminescence Computed Tomography (XLCT) to image LaF3 and Y2O3 nanoparticles.
A 3D XFCT/CT image of a mouse phantom conjugated with a NMR tube containing bromide and
Y2O3 was produced. Additionally, a cross sectional imaging in XFCT/XLCT/CT of a mouse
phantom with microcapillaries filled with LaF3:Tb3+ and Y2O3:Eu3+ attached. The results
demonstrated the plausibility of using a XFCT/XLCT/CT setup for monitoring therapeutic
nanoparticles, but acquisition time and penetration depth issues will need to be addressed first
Quantitative imaging of gold nanoparticle distribution for preclinical studies of gold nanoparticle-aided radiation therapy
Gold nanoparticles (GNPs) have recently attracted considerable interest for use in radiation therapy due to their unique physical and biological properties. Of interest, GNPs (and other high-atomic-number materials) have been used to enhance radiation dose in tumors by taking advantage of increased photoelectric absorption. This physical phenomenon is well-understood on a macroscopic scale. However, biological outcomes often depend on the intratumoral and even intracellular distribution of GNPs, among other factors. Therefore, there exists a need to precisely visualize and accurately quantify GNP distributions. By virtue of the photoelectric effect, x-ray fluorescence (XRF) photons (characteristic x-rays) from gold can be induced and detected, not only allowing the distribution of GNPs within biological samples to be determined but also providing a unique molecular imaging option in conjunction with bioconjugated GNPs. This work proposes the use of this imaging modality, known as XRF imaging, to develop experimental imaging techniques for detecting and quantifying sparse distributions of GNPs in preclinical settings, such as within small-animal-sized objects, tissue samples, and superficial tumors. By imaging realistic GNP distributions, computational methods can then be used to understand radiation dose enhancement on an intratumoral scale and perhaps even down to the nanoscopic, subcellular realm, elucidating observed biological outcomes (e.g., radiosensitization of tumors) from the bottom-up. Ultimately, this work will result in experimental and computational tools for developing a better understanding of GNP-mediated dose enhancement and associated radiosensitization within the scope of GNP-aided radiation therapy.Ph.D
X-RAY SPECTRAL ANALYSIS IN X-RAY FLUORESCENCE IMAGING FOR BREAST CANCER DETECTION
The knowledge of X-ray spectrum plays a major role in exploiting and optimizing the X-ray utilizations, especially in biomedical application fields. Over the past decades, extensive research efforts have been made in better characterizing the X-ray spectral features in experimental and simulation studies. The objectives of this dissertation are to investigate the applications of X-ray spectral measurement and analysis in X-ray fluorescence (XRF) and micro-computed tomography (micro-CT) imaging modalities, to facilitate the development of new imaging modalities or to optimize the imaging performance of currently available imaging systems.
The structure and primary discoveries of this dissertation are as follows: after a brief introduction of the objectives of this dissertation in Chapter 1, Chapter 2 gives a comprehensive background including electromagnetic properties, various applications, and different generation mechanisms of X-rays and their interactions with matter, X-ray spectral measurement and analysis methods, XRF principles and applications for cancer detection, and micro-CT system. Considering relatively high fluorescence production probability and sufficient penetrability of gold Kα fluorescence signals, Chapter 3 establishes a theoretical model of a gold nanoparticle (GNP) K-shell XRF imaging prototype consisting of a pencil-beam X-ray for excitation and a single collimated spectrometer for XRF detection. Then, the optimal energy windows of 66.99±0.56keV and 68.80±0.56keV for two gold Kα fluorescence peaks are determined in Chapter 4. Also, the linear interpolation method for background estimation under the Kα fluorescence peaks is suggested in this chapter. Chapters 5 and 6 propose a novel XRF based imaging modality, X-ray fluorescence mapping (XFM) for the purpose of breast cancer detection, especially emphasizing on the detection of breast tumor located posteriorly, close to the chest wall musculature. The mapping results in these two chapters match well with the known spatial distributions and different GNP concentrations in 2D/3D reconstructions. Chapter 7 presents a method for determining the modulation transfer function (MTF) in XRF imaging modality, evaluating and improving the imaging performance of XFM. Moreover, this dissertation also investigates the importance of X-ray spectral measurement and analysis in a rotating gantry based micro-CT system. A practical alignment method for X-ray spectral measurement is first proposed using 3D printing technology in Chapter 8. With the measured results and corresponding spectral analysis, Chapter 9 further evaluates the impact of spectral filtrations on image quality indicators such as CT number uniformity, noise, and contrast to noise ratio (CNR) in the micro-CT system using a mouse phantom comprising 11 rods for modeling lung, muscle, adipose, and bones (various densities). With a baseline of identical entrance exposure to the imaged mouse phantom, the CNRs are degraded with improved beam quality for bone with high density and soft tissue, while are enhanced for bone with low density, lung, and muscle. Finally, Chapter 10 summarizes the whole dissertation and prospects the future research directions
MULTIFUNCTIONAL NANOPHOSPHORS FOR TISSUE IMAGING AND DRUG DELIVERY
X-rays have been used for non-invasive high-resolution imaging of thick biological specimens since their discovery in 1895. They are widely used for structural imaging of bone, metal implants, and cavities in soft tissue. Recently, a number of new contrast methodologies have emerged which are expanding X-ray\u27s biomedical applications to functional as well as structural imaging. However, traditional X-ray imaging provides high spatial resolution imaging through tissue but do not measure chemical concentrations. In this dissertation, we describe an X-ray excited optical luminescence (XEOL) technique which uses a scanning X-ray beam to irradiate Gd2O2S phosphors and detect the resulting visible luminescence through the tissue. The amount of light collected is modulated by optical absorption in close proximity to the luminescence source. The ability to specifically target biological processes in vivo makes nanophosphors promising molecular imaging agents for XEOL. We also describe versatile techniques to design and fabricate multifunctional X-ray nanophosphors. The addition of pH-triggred drug release on our X-ray nanophosphors make it possible to monitor pH-triggered drug release rate in real time. The iron oxide encapsulated X-ray nanosctintillators offer promising multimodal MRI/fluorescence/X-ray luminescence contrast agents
Efficient architectures of heterogeneous fpga-gpu for 3-d medical image compression
The advent of development in three-dimensional (3-D) imaging modalities have generated a massive amount of volumetric data in 3-D images such as magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET), and ultrasound (US). Existing survey reveals the presence of a huge gap for further research in exploiting reconfigurable computing for 3-D medical image compression. This research proposes an FPGA based co-processing solution to accelerate the mentioned medical imaging system. The HWT block implemented on the sbRIO-9632 FPGA board is Spartan 3 (XC3S2000) chip prototyping board. Analysis and performance evaluation of the 3-D images were been conducted. Furthermore, a novel architecture of context-based adaptive binary arithmetic coder (CABAC) is the advanced entropy coding tool employed by main and higher profiles of H.264/AVC. This research focuses on GPU implementation of CABAC and comparative study of discrete wavelet transform (DWT) and without DWT for 3-D medical image compression systems. Implementation results on MRI and CT images, showing GPU significantly outperforming single-threaded CPU implementation. Overall, CT and MRI modalities with DWT outperform in term of compression ratio, peak signal to noise ratio (PSNR) and latency compared with images without DWT process. For heterogeneous computing, MRI images with various sizes and format, such as JPEG and DICOM was implemented. Evaluation results are shown for each memory iteration, transfer sizes from GPU to CPU consuming more bandwidth or throughput. For size 786, 486 bytes JPEG format, both directions consumed bandwidth tend to balance. Bandwidth is relative to the transfer size, the larger sizing will take more latency and throughput. Next, OpenCL implementation for concurrent task via dedicated FPGA. Finding from implementation reveals, OpenCL on batch procession mode with AOC techniques offers substantial results where the amount of logic, area, register and memory increased proportionally to the number of batch. It is because of the kernel will copy the kernel block refer to batch number. Therefore memory bank increased periodically related to kernel block. It was found through comparative study that the tree balance and unroll loop architecture provides better achievement, in term of local memory, latency and throughput
Molecular Imaging
The present book gives an exceptional overview of molecular imaging. Practical approach represents the red thread through the whole book, covering at the same time detailed background information that goes very deep into molecular as well as cellular level. Ideas how molecular imaging will develop in the near future present a special delicacy. This should be of special interest as the contributors are members of leading research groups from all over the world
Optimising the benefits of spectral x-ray imaging in material decomposition
The extra energy information provided by spectral x-ray imaging using novel photon counting x-ray detectors may allow for improved decomposition of materials compared to conventional and dual-energy imaging. The information content of spectral x-ray images, however, depends on how the photons are grouped together. This thesis deals with the theoretical aspect of optimising material discrimination in spectral x-ray imaging. A novel theoretical model was developed to map the confidence region of material thicknesses to determine the uncertainties in thickness quantification. Given the thickness uncertainties, photon counts per pixel can be optimised for material quantification in the most dose efficient manner. Minimisation of the uncertainties enables the optimisation of energy bins for material discrimination.
Using Monte Carlo simulations based on the BEAMnrc package, material decomposition of up to 3 materials was performed on projection images, which led to the validation of the theoretical model. With the inclusion of scattered radiation, the theoretical optima of bin border energies were accurate to within 2 keV. For the simulated photon counts, excellent agreement was achieved between the theoretical and the BEAMnrc models regarding the signal-to-noise ratio in a decomposed image, particularly for the decomposition of two materials.
Finally, this thesis examined the implementation of the Medipix detector. The equalisation of pixel sensitivity variations and the processing of photon counting projection images were studied. Measurements using the Medipix detector demonstrated promising results in the charge summing and the spectroscopic modes of acquisition, even though the spectroscopic performance of the detector was relatively limited due to electronic issues known to degrade the equalisation process.
To conclude, the theoretical model is sufficient in providing guidelines for scanning parameters in spectral x-ray imaging and may be applied on spectral projection measurements using e.g. the redesigned MedipixRX detector with improved spectroscopic performance, when it becomes available