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Cone-beam CT (CBCT) imaging is heavily being utilized in radiotherapy treatment as means of treating cancer patients. One of the platforms is the Varian On-Board Imager (oBI) where kilo-volts (kV) CBCT imaging is used. In this study, a model of the OBI is developed to simulate the two scan modes that are available, namely: Full-Fan (FF) and Half-Fan (HF) modes. By shifting the same set of 1024×768...
While other studies into sensing the thickness of subcutaneous fat have configured the axes of both the source and detector to be at a 90-degree angle to the surface being measured, we introduce a source-detector set up at 45-degree angle. We apply Gamos computer simulation and ex-vivo phantom experiment to compare the near infrared response between 90-degree and 45-degree position angles at 930 nm...
It is essential to have properly tuned PET scanner and data correction methods to obtain accurate quantitative images. Quality control (QC) procedure ensures reproducible performance of a clinical PET scanner. The scope of this study is to observe the stability of a PET scanner by monitoring the 511keV photopeak during a phantom/patient scan at the crystal level. In addition, during the histogramming...
Dose reduction is particularly important for pediatric imaging because children are more susceptible and sensitive to radiation exposure. This work reports on a design of a dual-energy dual-source versatile pediatric imaging system based on CMOS flat-panel detectors. To improve flexibility and usability, a fully-wireless control and data transfer platform based on Wi-Fi technology was implemented...
Flat-Panel C-arm Computed Tomography (CT) suffers from pixel saturation due to the detector's limited dynamic range. We describe a novel approach of analog, non-linear tone mapping (TM) for preventing detector saturation. An analog TM operator (TMO) applies a non-linear transformation in a CMOS (complementary metal-oxide semiconductor) sensor and its inverse TMO based on 14-bit digital raw data. This...
The OrthoCT (standing for orthogonal computed tomography) imaging technique consists in detecting radiation scattered in the patient and emitted at right angles with respect to the incident beam axis. Since photon scattering in the patient occurs with higher intensity in tissues of higher density, a detection system (constituted by a multi-slice collimator and a photon detector) positioned perpendicularly...
X-ray fluorescence CT (XFCT) imaging is a promising molecular imaging modality with high spatial resolution and non-radioactive high atomic number tracers for medical imaging. While dozens of bench-top experiments proofed the concept of the approach, scalability for clinical systems with high molecular sensitivity at acceptable doses is not yet accomplished. This study compares a spectroscopic CdTe...
Delivering precisely the desired dose distribution to the patient during radiotherapy is of crucial importance for treatment success and monitoring the actual distributed dose opens the possibility to correct for deposition inaccuracies and thus achieve better conformance to the treatment plan. Positron emission tomography has already been successfully used to measure the residual radioactivity from...
Measuring system response matrix (SRM) by Monte Carlo method is time and resource consuming, even with high performance computer nodes. In this paper, we exploited symmetry properties available to drastically reduce the complexity in computing SRM of panel PET, which has two parallel panel detectors. By extending the original system and simulating 4 voxels every slice parallel to the PET detector,...
In compact systems, precise measurement in the projection space may be compromised due to minification. The objective of this work is to investigate the impact of the magnification factor in a model-based calibration procedure. This has direct relevance to the geometrical calibration of the clinical INSERT camera. Projection data from three point sources were simulated for a single pinhole collimator...
The benefit of time-of-flight (TOF) in PET reconstruction has been established for clinical imaging, and the signal-to-noise benefit with TOF has been demonstrated to increase with higher randoms fractions. TOF information mitigates and reduces image artifacts arising from errors in the corrections, but it may not account for all changes with count rate. Standard performance measures of image quality...
Within the German Plant Phenotyping Network (DPPN), we developed a novel PET scanner based on Philips Digital Photon Counters (DPCs, or dSiPMs = digital Silicon Photomultipliers). The scanner is dedicated for plant research and provides functional information on carbon transport within the plant. To this end the detector ring is oriented horizontally. It provides a Field-of-View of 18 cm dia. and...
In this work we perform a preliminary investigation of a discretized natural pixel expansion set for image representation in optimization-based image reconstruction for X-ray computed tomography. In particular, we focus our attention on total variation regularized image reconstruction in pixel and discrete natural pixel expansion sets. The work is motivated by two observations: (1) under certain conditions,...
XFCT is a promising new molecular imaging modality which is able to measure non-radioactive tracer molecules even in deep tissues. Unrestricted spatial resolution imaging with pencil beam x-ray excitation is possible but cannot be translated easily to clinical applications as scanning times are at least several hours. The spatial information accessed with Compton cameras (CCs) overcomes this drawback...
The sensitivity of ion therapy to inaccuracies in treatment planning and delivery procedures demands the development of imaging techniques capable of accurate assessment of the Relative (to water) ion Stopping Power (RSP). The investigated tomographic carbon ion CT (iCT) imaging setup consists of a prototype integration-mode detector working as range telescope using active scanning ion beam delivery...
In this work, a direct image reconstruction algorithm for PET is proposed. This method follows naturally from the concept of LOR, and easily admits depth of interaction and time of flight information. In addition, this algorithm does not require the computation of sinograms or a system matrix. Thus, it is not restricted in the formation of high pixel density images and allows the image formation in...
A new imaging technique, called orthogonal ray imaging, has been proposed to assist external-beam radiation therapy treatments. This technique consists in detecting radiation scattered in the patient and emitted perpendicularly to the incident beam axis. Since photon scattering in the patient occurs with higher intensity in tissues of higher density, a detection system (constituted by a multi-slice...
The moving blocker method is economic and effective for scatter correction (SC) of cone-beam computed tomography (CBCT). However, at the regions with large intensity transition in the projection images in the axial blocker moving direction, the estimation of scatter signal from blocked regions in a single projection view can produce large errors, which can cause significant artifacts in reconstructed...
From the point of view of the image quality, the contrast-to-noise ratio (CNR) is a crucial parameter. In case of the scintillation detectors, which are widely used in X-ray radiography and computed tomography, CNR is determined by the static image noise caused mainly by the non-uniformity of the response of particular pixels, and by the stochastic noise, composed of the inherent noise of the detector...
The noninvasive detection of inhomogeneities in biological tissues is studies using phantoms. The proposed reflectance systems consist of a scanning probe with four units. Each unit equipped with a photon injection port, and these ports are arranged in a straight line fashion to collect the backscattered photons from different depths. The inhomogeneities are placed in three different depths like 7mm,...
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