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In vivo imaging techniques applied to small animals are important tools in basic research. Scintigraphic planar and tomographic images allow in vivo functional expression of the protocol's effect on the animal's organs to be assessed. In that way, long term dynamical studies can be developed on the same animal, which can be used as its own control, helping to reduce statistical uncertainties, to cut...
Pulse pile-up at high count rates is one factor that degrades spatial resolution of PET images. Most PET scanners with block detector designs suffer misidentification of event position, moving events from the edge to block center at high count rates. For the HRRT with LSO-LYSO phoswich detectors, there is an extra dimension of pile-up, i.e., inter-layer pile-up, which tends to push events to the LYSO...
A multiple-wavelength near-infrared (NIR) imaging device has been constructed. The scanner utilizes transmitted through the objects NIR light at five different wavelengths in the interval of 900nm-1600nm. The scanning is realized by a consecutive positioning of Hamamatsu G9203-256D InGaAs linear image sensor sliding close to the scanned object and results in a set of five object's images. The scanned...
Simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) can provide both functional and structural information about disease. However, for quantitative PET measurements all sources of scatter and absorption that photons undergo on their trajectory between source and detector must be assessed. In simultaneous PET/MR, this includes the scatter and absorption undergone in...
As the dimensions of crystal elements in modern PET systems is getting smaller, the fraction of events undergoing inter-crystal scattering (ICS) and penetration increases. This has deteriorative impact on the spatial resolution of images. However, with the utilization of statistical image reconstruction methods in PET, compensation for ICS and penetration impacts is feasible by accurately modeling...
We are developing a high resolution and quantitative SPECT for the human brain. The SPECT has two types of detector, a large FOV detector with a parallel collimator and a small FOV detector with a pinhole collimator. A quantitative and high resolution image is reconstructed by the small FOV detector using a supporting image obtained by the large FOV detector. The large FOV detector consists of a Nal(Tl)...
Positron range depends on the materials in which positron propagates and on positron emitter isotope. As positron range limits the spatial resolution of PET images, good quantitative estimates of it should be included in any realistic simulation of PET acquisitions. In this work we compare positron range estimates obtained with PeneloPET to previous available simulations and experimental data. PeneloPET...
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...
High spatial resolution of multi-pinhole SPECT is often hampered by physical effects including collimator response, and pinhole edge penetration. The collimator response is related to the blurring effect varying with distance from source to the aperture, and caused by the non-ideal aperture diameter. Pinhole edge penetration is referred to penetration of gamma rays through the thin edge of the collimator,...
Several improvements of the k-nearest neighbor (k-NN) method for the determination of the entry point (x, y) of a gamma photon in a monolithic scintillator PET detector have been investigated with the aim to obtain better spatial resolution and/or to enable faster detector calibration by reducing the amount of required reference data and by allowing for calibrating with a line source. These methods...
High temporal resolution and high spatial resolution are required to image the coronary arteries without motion artifacts. Several approaches have been pursued to achieve better temporal resolution including faster rotational speeds, and dual tube systems. In this paper, we present an alternative approach using motion estimation and compensation. The results demonstrate that the proposed methods can...
With the advance in PET technology and especially scintillating detectors, spatial resolution in the order of 2 mm FWHM are becoming a reality, allowing a more in-depth exploration of complex organs such as the human brain. Subject movement during imaging has always been a factor contributing to image degradation, but is becoming a major limitation in the achievement of the full spatial resolution...
The goal of the HICAM project, supported by the European Community, is the development of a new Anger camera for clinical and research environments and specific applications where high overall spatial resolution and system compactness are required. The camera is based on a matrix of Silicon Drift Detectors (SDDs) coupled to a CsI(Tl) crystal. Two prototypes were developed during the project, with...
We showed that multidimensional parametric modeling is an interesting method to improve the spatial resolution of ultrasound images. The major issue is to estimate simultaneously the model parameters and orders. We recently proposed a least-square-based technique which is able to estimate both orders and parameters of a general N-dimensional auto-regressive (AR) model. This method has been extended...
Background: The spatial resolution of conventional imaging examinations is mostly millimeter level, which is difficult to implement the imaging of small hepatic tumors, thus the best time for treatment is bungled. The synchrotron radiation X-ray in-line phase-contrast imaging (IL-PCI) uses the phase information carried by X-rays after passing through the objects to image, and the spatial resolution...
Four-dimensional (4D) computed tomography (CT) can be used in radiation treatment planning to account for respiratory and organ motion. Current 4D CT techniques have limitations in either spatial or temporal resolution. In addition, 4D CT increases the radiation dose to the patients. The purpose of this study is to accurately predict images using 4D CT scan with the contour and projection imaging...
A prototype of photoacoustic standard CT(PSCT) has been designed for high resolution quasi-3D photoacoustic tomography with a focused digital phased array transducer. To realize photoacoustic computed tomography, each element of the transducer array possess a thin cylinder ultrasonic lens to select 2D image plane and suppress the out-of-plane signals. The modified LFBP algorithm is utilized to reconstruct...
In clinical applications, images with high resolution are often desired and required which may provide more details for doctors to make precise diagnosis. In this paper, an approach is proposed to increase image resolution of parallel magnetic resonance imaging. Since different receiver coils have different sensitivity profiles, different receiver channel models are constructed to map the original...
Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is commonly performed using 2D single-shot echo-planar imaging (EPI). However, recent studies have suggested that 3D multi-shot sequences such as PRESTO may offer comparable BOLD contrast-to-noise ratio with increased volume coverage and decreased geometric distortions. A four-way comparison was performed between...
High-quality mammography is the most effective technology presently available for breast cancer screening. High resolution mammograms usually lead to more accurate diagnoses; however, they require large doses of radiation, which may have harmful effects. In this paper, we present a method to synthesize high-resolution mammograms from low-resolution inputs, which offers the potential of allowing accurate...
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