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Restricted by the hardware, the projection number at a single phase for 4D-CBCT imaging is very low or even less than 10, thus the associated reconstruction by using conventional reconstruction algorithms will be constrained by serious streak artifacts and noises. To address this problem, in this paper, we are aiming to develop an approach to reconstruct the 4D-CBCT image with multi-phase projections,...
Dual energy computed tomography (DECT) has improved capability of differentiating different materials compared to conventional CT. However, due to non-negligible radiation exposure to patients, dose reduction has recently become a critical concern in CT imaging field. Moreover, direct material decomposition techniques such as numerical inversion can yield significantly amplified noise in the basic...
Cerebral perfusion computed tomography (CPCT) provides functional information about capillary-level hemody-namic of brain parenchyma, which is an important tool for evaluating acute stroke, vasospasm and other neurovascular disorders. Meanwhile, the side effect of accumulated radiation, relating to genetic or cancerous diseases due to repeated dynamic scans at the same site, has caused great public...
Low-dose computed tomography (LdCT) has been widely used in clinical applications including image-guided biopsy needle and lung screening. With the low radiation dose in data acquiring during the scans, the image quality will degrade due to the excessive quantum noise if there is no adequate noise treatment in processing the data for image reconstruction. For conventional low-dose CT (LdCT) reconstruction,...
Four dimensional cone-beam computed tomography (4D-CBCT) has great clinical value because its ability to describe tumor and organ motion. But the challenge in 4D-CBCT reconstruction is the limited number of projections at each phase, which resulting in the reconstruction full of noise and streak artifacts with the conventional FDK algorithm. To address the problem, in this work, we propose a novel...
Low-dose x-ray computed tomography (CT) scan is clinically desired. However, the quality of low-dose CT image is severely degraded due to excessive photon quantum noise and electronic noise. To improve the quality of CT image with lower milliampere-seconds (mAs), in this study, we developed an iterative image reconstruction algorithm based on the maximum a posterior (MAP) principle. To preserve the...
High radiation dose during x-ray computed tomography (CT) examinations can increase the risk of cancer and has become major concerns to patient. Accordingly, minimizing the radiation exposure without sacrificing image quality is a meaningful research topic. In this work, with the aim to reduce radiation during data acquisition, we propose a penalized weighted least-squares (PWLS) scheme to retain...
Spectral computed tomography (CT) with energy-resolved detector has gained considerable interests in recent years due to its remarkable abilities in yielding high energy resolution and material differentiation. However, because of the limited photon counts using narrow energy bin, spectral CT images usually suffer from poor SNR and strong streak artifacts. In this work, to restore each energy-specific...
Ring artifacts often appear in flat-panel detector based CT images due to the malfunction and mis-calibration of detector elements resulting in stripe artifacts in the sinogram data. In this paper, we propose an improved ring artifacts removal (IRAR) approach by combining multi-resolution analysis and weighted moving average filter methods. Specifically, the multi-resolution analysis method can suppress...
The purpose of this study is to validate the application of GATE (Geant4 Application for Tomographic Emission) Monte Carlo simulation toolkit to model the performance characteristics of Siemens Inveon small animal PET system. GATE has been utilized to accurately create a complete PET imaging system model, including system geometry, physics process, signal processing and time-dependent effects. The...
Dynamic positron emission tomography (PET) imaging provides important quantitative information of physiological and biochemical processes in humans and animals. However, due to short-time acquisitions to obtain a time sequence of images for parametric imaging, the signal-to-noise ratio of measurement data in each time frame is often very low, which leads the dynamic PET image reconstruction to be...
Statistical iterative reconstruction (SIR) approaches have shown great potential in x-ray computed tomographic (CT) reconstruction in the case of low-dose protocol. For yielding high quality image, an edge-preserving regularization should be incorporated into the objective function of SIR approaches. A typical example is the Huber regularization with an edge-preserving non-quadratic potential function...
Ultra-low-dose x-ray computed tomography (CT) imaging is needed in CT fields. Through a scan protocol by lowering the milliampere-seconds (mAs) and reducing the number of projections per rotation around the body, we can realize low-dose CT imaging. However, the resulting noisy and insufficient measurements will unavoidably cause the degradation of desired-image. To solve this problem, iterative image...
Due to the noisy measurement of the voxel-wise time activity curve (TAC), parametric imaging for dynamic positron emission tomography (PET) is a challenging task. To address this problem, some spatial filters, such as Gaussian filter, bilateral filter, wavelet-based filter, and so on, are often performed to reduce the noise of each frame. However, these filters usually just consider local properties...
In X-ray computed tomography (CT) reconstruction, accurate statistical modeling of the measurement after linearity/nonlinearity calibration is essential to yield high quality diagnostic images, especially for low-dose CT. Due to the complicate noise distribution of after-log projection data or sinogram data, direct image reconstruction by filtered back-projection (FBP) approach is a very challenging...
Repeated X-ray cone beam computed tomography (CBCT) scans are frequently entailed in some clinical cases, such as CT-guided lung lesions puncture examination, image-guided intervention and radiotherapy, which result in individual patient doses soaring due to the associative volume scanning. Sparse-views based image reconstruction, as an effective method for reducing the radiation dose in CBCT scans,...
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