Scatter correction in single photon emission computed tomography (SPECT) has been focused on either using multiple-window acquisition technique or the scatter modeling technique in iterative image reconstruction. We propose a technique that uses only the emission data for scatter correction in SPECT. We assume that the scatter data can be approximated by convolving the primary data with a scatter kernel followed by the normalization using the scatter-to-primary ratio (SPR). Since the emission da...

The iterative reconstruction algorithms for X-ray CT image reconstruction suffer from their high computational cost. Recently Nvidia releases common unified device architecture (CUDA), allowing developers to access to the processing power of Nvidia graphical processing units (GPUs), in order to perform general purpose computations. The use of the GPU, as an alternative computation platform, allows decreasing processing times, for parallel algorithms. This paper aims to demonstrate the feasibilit...

A direct filtered-backprojection (FBP) reconstruction algorithm is presented for circular cone-beam computed tomography (CB-CT) that allows the filter operation to be applied efficiently with shift-variant band-pass characteristics on the kernel function. Our algorithm is derived from the ramp-filter based FBP method of Feldkamp et al. and obtained by decomposing the ramp filtering into a convolution involving the Hilbert kernel (global operation) and a subsequent differentiation operation (loca...

In this paper we propose a new method for evaluating image recording strategies for limited angle tomography. In limited angle tomography exact three-dimensional (3-D) reconstruction is not achievable. With this method a metric for the reachable reconstruction quality by defined X-ray source trajectories is calculated. The result of our method is independent of reconstruction algorithms. Our approach is based on the gradients of the scanned volume and their grade of determinability. Compared to ...

Iterative methods are popular choices in image reconstruction fields due to their capability of recovering object information from incomplete acquisition data. However, the computation process involves frequent uses of forward and backward projections that are computationally expensive. Past research has proved that a forward projector that can produce high quality images is crucial to achieve a good convergence rate. In this paper a high performance iterative reconstruction framework is introdu...

We present a theoretically-exact and stable computed tomography (CT) reconstruction algorithm that is capable of handling interrupted illumination and therefore of using all measured data at arbitrary pitch. This algorithm is based on a differentiated backprojection (DBP) on M-lines. First, we discuss the problem of interrupted illumination and how it affects the DBP. Then we show that it is possible to take advantage of some properties of the DBP to compensate for the effects of interrupted ill...

The goal of this paper is to investigate different reconstruction methods for solving the limited angle problem in reconstructing the projection data from a stationary multi-pinhole system based on a three-head clinical single photon emission computed tomography (SPECT) camera. Three iterative reconstruction approaches were studied including maximum likelihood expectation maximization (MLEM), maximum a posteriori expectation maximization (MAPEM) with a smoothing prior, and an alternatin...

The ability to correctly quantify activity concentration with single photon emission computed tomography (SPECT) is limited by its spatial resolution. Blurring of data between adjacent structures, which is known as partial volume effects, can be compensated for by utilizing high resolution structural information from other imaging modalities such as CT or MRI. Previously developed partial volume correction (PVC) methods normally assume a spatially invariant point spread function. In SPECT this i...

A consistency condition is developed for computed tomography (CT) projection data acquired from a straight-line X-ray source trajectory. The condition states that integrals of normalized projection data along detector lines parallel to the X-ray path must be equal. The projection data is required to be untruncated only along the detector lines parallel to the X-ray path, a less restrictive requirement compared to Fourier conditions that necessitate completely untruncated data. The condition is i...

We utilize the Novikov-Natterer algorithm for non-uniform attenuation to invert the backscatter projections formed by the scatter of X-rays. The backscatter signal is treated as an emitter in a non-uniformly attenuating medium. This type of tomography has applications in radiology and dentistry for which metals effectively block the transmission of X-rays. Scanning for metals also has applications in security/baggage screening. The results show that when the forward scattering angle is zero, the...

The back-projection-filtration (BPF) algorithm has been applied to image reconstruction for cone-beam configurations with general source trajectories. The BPF algorithm can reconstruct 3-D region-of-interest (ROI) images from data containing truncations. However, like many other existing algorithms for cone-beam configurations, the BPF algorithm involves a back-projection with a spatially varying weighting factor, which can result in the non-uniform noise levels in reconstructed images and incre...

There has been a renewed interest in algorithm development for image reconstruction from highly incomplete data in computed tomography (CT). Such algorithms may lead to reduced imaging dose and time, and to the design of innovative configurations tailored to specific imaging tasks. In recent years, a carbon-nanotube (CNT)-based field-emission x-ray source has been developed, which offers easy electronic control of radiation and thus can be an ideal candidate for gated imaging. We have recently p...

We investigate the feasibility of dual-energy method for image contrast enhancement in small animal studies using a low kV X-ray radiographic system. A robust method for X-ray spectrum estimation from transmission measurements, based on expectation-maximization (EM) method, is applied to an X-ray specimen radiographic system for dual energy imaging of a mouse. From transmission measurements of two known attenuators at two different X-ray tube voltages, the X-ray energy spectra are reconstructed ...

This paper investigates a reconstruction method for helical computed tomography which compensates for the motion artifacts in the thorax caused by patient breathing. The method takes into account a motion vector field determined from a four-dimensional (4-D) uncompensated image data set. Surface models of the lung and the ribs are tracked through the 4-D data set to create motion information within the entire thorax. Finally, an image is reconstructed using motion compensated back-projection. Th...

Accurate geometrical calibration is critical to obtaining high resolution and artifact free reconstructed images for modern animal single photon emission computed tomography (SPECT) systems. Although there have been many published works on the calibration of various SPECT systems, few studies have been done to evaluate the efficacy of the proposed calibration methods in a quantitative manner. This paper presents a numerical method to assess both the uniqueness and the quantitative accuracy of SP...

In line X-ray phase contrast micro-computed tomography (IL-XPCT), which can be implemented at third generation synchrotron radiation sources or by using a micro-focus X-ray tube, is a powerful technique for non-destructive, high-resolution investigations of a broad variety of materials. At the Shanghai Synchrotron Radiation Facility (SSRF), the X-ray Imaging and Biomedical Applications Beamline was built and started regular user operation in May 2009. Both qualitative (without phase retrieval) a...

This paper presents an optimized implementation of the FDK algorithm on a single fixed-point TMS320C6455 digital signal processor (DSP). Software pipelining and proper configuration of the data transfer enables a 2563 volume to be reconstructed in about 42 seconds from 360 projections with very good accuracy. This implementation reveals the potential of modern high-performance DSPs in accelerating image reconstruction, especially when cost and power consumption are emphasized.

Axial scan along circular trajectory has been the most desirable in clinical and preclinical applications. However, due to the violation of the data sufficiency condition, the reconstruction accuracy of axial scan deteriorates rapidly with increasing detector z-dimension. A number of algorithms have been proposed thus far to improve the reconstruction accuracy. It is well understood that, the larger the radius of circular trajectory, the more accurate the reconstruction. Ultimately, the...

This paper gives an efficient approach to reconstruct moving multiple objects (multi-object). Each object has independently rigid motion which includes translation and rotation. The traditional FBP algorithm can resolve the one-object motion problem rather well. However, it suffers from perceptible motion artifacts in multi-object cases. This paper proposes a new motion-compensated reconstruction approach with a priori knowledge of the rigid motion model. Both an FBP-type and an ART-typ...

A three-dimensional (3-D) phantom for the density distribution of the plasmasphere is established. The imaging processes of the extreme ultraviolet (EUV) Imager are computer-simulated, in which the Earth shelter is treated as a main problem. A modified ART method is devised to resolve the incomplete data reconstruction problem to validate and evaluate the proposed methods. The cone-beam EUV data are simulated based on the 3-D phantom from both a circular and semi-circular trajectories. Quantitat...