Ali Atharifard
A5083438350- Advanced X-ray and CT Imaging
- Medical Imaging Techniques and Applications
- Radiation Dose and Imaging
- Electrical and Bioimpedance Tomography
- Photoacoustic and Ultrasonic Imaging
- Dental Radiography and Imaging
- Advanced Optical Sensing Technologies
- Digital Radiography and Breast Imaging
- Nuclear Physics and Applications
- Medical Image Segmentation Techniques
- Radiation Detection and Scintillator Technologies
- Orthopedic Infections and Treatments
- Advanced Neural Network Applications
- Particle Detector Development and Performance
- Adversarial Robustness in Machine Learning
- Advanced Image Fusion Techniques
University of Otago
2014-2018
This paper discusses methods for reducing beam hardening effects and metal artefacts using spectral x-ray information in biomaterial samples. A small-animal scanner was operated the 15 to 80 keV energy range this study. We use photon-processing features of a CdTe-Medipix3RX ASIC charge summing mode reduce associated artefacts. present data collected alloy samples, its analysis algebraic 3D reconstruction software volume visualisation custom rendering software. The cupping effect streak are...
This study demonstrates the translation of small-bore MARS photon-counting CT technology to live human spectral imaging within a clinical radiation dose level. We used same platform (hardware and software) for acquisition data, image reconstruction, material decomposition visualisation as in CT. Small-bore has been produce promising results fields cancer, bone cartilage health, cardio-vascular diseases. With development large-bore CT, small-animal studies can now be translated humans, sheep,...
This paper outlines image domain material decomposition algorithms that have been routinely used in MARS spectral CT systems. These (known collectively as MARS-MD) are based on a pragmatic heuristic for solving the under-determined problem where there more materials than energy bins. contains three parts: (1) splitting into number of possible sub-problems, each containing fewer materials; (2) sub-problem; and (3) applying rejection criteria to eliminate all but one sub-problem's solution. An...
Energy resolving performance of spectral CT systems is influenced by the accuracy detector's energy calibration. Global calibration maps a given threshold to average response all pixels detector. Variations arising from CMOS manufacturing processes and properties sensor cause different respond differently photons same energy. Threshold dispersion adversely affects imaging degrading resolution, which contributes blurring information. In this paper, we present technique for per-pixel...
This study aims to demonstrate that spectral CT imaging can identify and quantify inflammatory components of unstable plaque such as iron, calcium lipid in phantoms excised human atherosclerotic plaques. Spectral acquisition protocol was optimised using the MARS scanner. A phantom with multiple concentrations ferric nitrate (25, 50, 100, 200 400 mg/ml), hydroxyapatite (104.3, 402.3, 603.3 mg/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML"...
The aim is to perform qualitative and quantitative assessment of metal induced artefacts small titanium biomaterials using photon counting spectral CT. energy binning feature some detectors enables the measured spectrum be segmented into low, mid high bins in a single exposure. In this study, solid porous implants submerged different concentrations calcium solution were scanned animal MARS scanner equipped with polyenergetic X-ray source operated at 118 kVp. Five narrow (7-45 keV, 45-55...
Images from MARS spectral CT scanners show that there is much diagnostic value using small pixels and good energy data. use energy-resolving photon-counting CZT Medipix3RX detectors measure the of photons on a five-point scale with spatial resolution 110 microns. The information gives material discrimination quantification. 3D reconstruction voxel size 70 We present images pre-clinical specimens, including excised atheroma, bone joint samples, nanoparticle contrast agents along living...
In this paper, we present a method that uses combination of experimental and modeled data to assess properties x-ray beam measured using small-animal spectral scanner. The spatial the profile are characterized by shape, angular offset along rotational axis, photon count difference between at central axis. Temporal stability is assessed measuring intra- interscan variations. assessment was evaluated on several CT scanners equipped with Medipix3RX-based detectors. On well-calibrated scanner,...
Assessment of disease burden and drug efficacy is achieved preclinically using high resolution micro computed tomography (CT). However, micro-CT not applicable to clinical human imaging due operating at dose. In addition, the technology differences between standard CT prevent direct translation preclinical applications. The current proof-of-concept study presents spectral photon-counting as a clinically translatable, molecular tool by assessing contrast uptake in an <italic...
Treatment failure in cancer is often due to variation tumour characteristics within the same tumour, or across sites, over time. At present, most cancers are staged with imaging; treatment selected, then patient re-imaged see if working. We intend transform that approach by using a novel non-invasive spectral imaging technology together targeted and non-targeted gold nanoparticles measure burden as well drug delivery. In this study, we report CT of four different cell types (ovarian, breast,...
The latest version of the MARS small bore scanner makes use Medipix3RX ASIC, bonded to a CdTe or CZT semi-conductor layer, count x-ray photons and create spectroscopic CT data set. imaging chain uses energy-resolved 2D transmission images construct quantitative 3D spectral material images. To improve performance system it is important that energy response detector well calibrated. A common methodology for calibration fluorescence (XRF), due its effective monochromatic nature. Oblique...
Spectral computed tomography (CT) systems are employed with energy-resolving photon counting detectors. Incorporation of a spectrally accurate x-ray beam model in image reconstruction helps to improve material identification and quantification by these systems. Using an inaccurate spectral can lead severe artifacts, one the extreme cases this is well-known beam-hardening artifacts. An often overlooked feature beams models angular dependence spectrum reference central axis. To address...
The aim of the present study is to show that non-invasive MARS imaging can differentiate between infected and healthy pulmonary tissue using an iodine-based contrast agent at high resolution. One C57BL/6J mouse with chronic tuberculosis (TB) was euthanized CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> excised. TB lungs were incubated in 3% iodine solution. Mouse free also excised solution for control purposes. Calibration scanner...
We describe a CMS-Medipix3RX neutron camera developed by adapting and modifying detector readout electronics at the University of Canterbury. The are part MARS x-ray scanner used for imaging applications [1]. cameras will be precise evaluation complex radiation fields in around Compact Muon Solenoid (CMS) on Large Hadron Collider (LHC) CERN. This help to ascertain performance various sub-systems installed cavern as well predict their useful lifetimes. Medipix3RX can deliver real-time images...
In this article, we propose a slice-based interactive segmentation of spectral CT datasets using bag features method. The data are acquired from MARS scanner that divides up the X-ray spectrum into multiple energy bins for imaging. literature, most existing methods limited to performing specific task or tied particular imaging modality. Therefore, when applying generalized datasets, additional information cannot be sufficiently utilized. We describe new approach circumvents problem by...