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We propose nonlocal-means (NLM) approaches to incorporating prior anatomical information into PET image reconstruction. In our NLM approaches, adaptive smoothing is performed on the PET image by using the weights that reflect the self-similarity property of the underlying PET image with the aid of the additional information obtained from the anatomical image. Unlike conventional anatomy-based reconstruction...
Including anatomical information during emission tomography reconstruction with resolution modeling can enhance the image quality. Often accurate segmentation of the anatomical image is required, being a major challenge for most applications. Recently, we studied a segmentation-free MAP algorithm proposed by Bowsher et al, that encourages similar activity in a selection of neighboring voxels that...
Many researchers have been studying on the noise properties and image quality influence on system performance for tomographic imaging in recent years. Most of the works are focused on 2D nuclear medicine imaging. Since X-ray CT dosage has been pushed to a lower level and 3D imaging has been a trend, it is necessary to study the performance of 3D X-ray CT systems. In this work, we presented a new theoretical...
A well known limitation of the multi-pinhole system is that the reconstructed images may suffer from artifacts due to truncated and/or overlapping projections. A previous study showed that these artifacts can be strongly suppressed by using prior knowledge about the object boundary, which is typically obtained from a CT- or MRI-scan acquired in the same pose. Forcing the reconstructed activity outside...
The current study aimed to derive accurate estimates of regional cerebral blood flow (rCBF) from noisy dynamic [15O]H2O PET images acquired on the High Resolution Research Tomograph (HRRT), whilst retaining the high spatial resolution of this scanner (2-3 mm) in parametric images. We compared the PET autoradiographic and the generalised linear least squares (GLLS) methods to the non-linear least squares...
Energy sensitive photon counting x-ray detectors (PCXD) [1] have many advantages over energy-integrating x-ray detectors (EIXD) in x-ray computed tomography (CT), such as the ability to measure the spectrum of x-ray beams. When such PCXDs are operated under a high count rate in clinical scanners, coincident photons would distort the recorded energy spectrum due to the limited speed of the detector...
Reconstruction algorithm based on total variation (TV) minimization has become a hot topic in CT field. In order to make a better balance between suppressing noise and preserving edge, an improved variation is proposed in this paper. An anisotropic strategy is developed to effectively preserve the edges of imaging objects. Simultaneously, the unity weight in the original variation is substituted by...
We propose an experimental methodology that facilitates practical assessment of low-contrast detectability maps in real CT images. Specifically, we explain how one may efficiently estimate the area under the ROC curve for a channelized Hotelling observer applied to signal-known-exactly/background-known-exactly lesion detection tasks at multiple points in the imaging field-of-view. Our approach builds...
We present an adaptive acquisition protocol design technique with the goal of improving local contrast-to-noise ratios (CNR) for flexible SPECT and PET scanners in which the data acquisition parameters at each view can be modulated. Such flexible scanners include rotating SPECT scanners, dual head coincidence imagers, SPECT scanners with variable collimators and those where collimators move in relation...
Denoising low signal-to-noise-ratio (SNR) images is a significant challenge since the intensity gradient due to noise elements may compete with or even exceed the intensity gradient due to features in the images. This situation can often be encountered in photon-limited medical imaging applications such as MLEM reconstructed Positron Emission Tomography (PET) images. In this study, we propose a median...
The new generation of dedicated cardiac SPECT systems achieve high detection efficiency by focusing onto a small field of view (FOV) that encloses a patient's heart. They also generally use a relatively small number of views for angular sampling. The objective of this study is to use simulations to investigate the relationship between number of views and image quality when iterative reconstruction...
The pharmacokinetics extracted from PET images in the brain is relied to the physiological mechanisms that describe the processing of the tracer by the brain structures. These processes can be described through a multi-compartments model detailing the different states of the tracer and the transfer rate between these states. Numerous work have been proposed for the estimation of the input function...
In this paper we propose a novel method for collimator design in single photon emission tomography (SPECT). The challenge here is to find a practical collimator design that allows good recovery and good sensitivity. Instead of working on the collimator's shape, the problem is addressed by optimizing the point spread function (PSF) with respect to the performance of the reconstruction algorithm in...
Double-gated in-vivo small animal cone-beam micro-CT scans provide five-dimensional information about the object: the three volume dimensions plus the temporal dimensions of the respiratory motion and the heart motion, respectively. Double gating is typically performed to separate respiratory from cardiac motion when imaging the animal's lung or heart.
Multi-Harmonic Phase Analysis (MHPA) has been developed for heart failure prognosis by reliably measuring left-ventricular (LV) dyssynchrony from conventional gated single photon emission tomography (GSPECT) myocardial perfusion imaging (MPI). Although MHPA has been evaluated in multiple clinical studies, its accuracy can be limited under highly noisy conditions. The purpose of this study is to develop...
Partial volume effect (PVE) in PET generates under-estimation of radiotracer concentration in small size structures. Consequently, the image contrast is qualitatively degraded and, quantitatively, the reduced signal intensity leads to erroneous physiological parameter estimation. The most popular approach to correct for PVE is based on recovery factors (RF). RFs are first estimated from objects of...
Multi-Harmonic Phase Analysis (MHPA) has been developed to quantify left-ventricular (LV) mechanical dyssynchrony with gated single photon emission tomography (SPECT) myocardial perfusion imaging (MPI). Although MHPA has shown promising clinical results, it needs to be optimized technically. The purpose of this study is to develop a tool to simulate LV mechanical dyssynchrony in gated SPECT MPI using...
Synthetic CT noise emulation in the raw data domain is reported. A method that synthetically adds noise directly in the raw data domain (i.e., before the negative log and associated pre processing) is presented. Initial results are obtained for a noise simulation method that lowers the effective tube current for a CT data set while considering quantum noise, electronic noise, bowtie filtration, and...
We have developed a CsI(Tl)/PIN detector module for high resolution SPECT and low dose photon-counting CT imaging. Using the detector modules with 6.1mm pixels, we built a cardiac SPECT system with three detector heads. The detector heads form a triple-head (each 20×15cm), geometry for emission scans and reconfigure to form a large transaxial field-of-view (FOV) geometry for transmission scans using...
In SPECT the collimator and reconstruction algorithm both control image quality. For a given task, one might naturally seek that combination of collimator and algorithm parameters that maximizes task performance. Here, we use a brute force method to compute task performance over a joint space of collimator and algorithm parameters. Our interest is the task. We perform our brute force computation for...
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