Traditional cell nucleus detection relies on pathologists with microscopes, which is a tedious, costly and time consuming progress. We develop a deep learning and stochastic processing method to auto-segment those microscopy images, named as Quick-in-process(Qip)-Net. Qip-Net was proposed as an automated method to detect cell nucleus under various conditions, such as randomized cell types, different magnifications, and varying image backgrounds. The network is constructed based on regions with convolution neural network features (RCNN). It is trained by 663 original images and their corresponding masks from Kaggle website. The results showed that Qip-Net could rapidly segment the cell nuclei from the testing dataset of complex and disruptive surroundings with better S-2 score around 3% compared to U-Net.
Many clinical scenarios involve the presence of metal objects in the CT scan field-of-view. Metal objects tend to cause severe artifacts in CT images such as shading, streaks, and a loss of tissue visibility adjacent to metal components, which is often the region-of-interest in imaging. Many existing methods depend on synthesized projections and classification of in-vivo materials whose results can sometimes be subject to error and miss details, while other methods require additional information such as an accurate model of metal component prior to reconstruction. Deep learning approaches have advanced rapidly in recent years and achieved tremendous success in many fields. In this work, we develop a deep residual learning framework that trains a deep convolution neural network to detect and correct for metal artifacts from image content. Training sets are generated from simulation that incorporates modeling of physical processes related to metal artifacts. Testing scenarios included the presence of a surgical screw within the transaxial plane and two rod implants in the craniocaudal direction. The proposed network trained by polychromatic simulation data demonstrates the capability to largely reduce or, in some cases, almost entirely remove metal artifacts caused by beam hardening effects. The proposed method also showed largely reduced metal artifacts on data collected from a multi-slice CT system. These findings suggest deep residual learning enabled methods present a new type of promising approaches for reducing metal artifacts and support further development of the method in more clinically realistic scenarios.
Purpose: Atherosclerosis detection remains challenging in coronary CT angiography for patients with cardiac implants. Pacing electrodes of a pacemaker or lead components of a defibrillator can create substantial blooming and streak artifacts in the heart region, severely hindering the visualization of a plaque of interest. We present a novel reconstruction method that incorporates a deformable model for metal leads to eliminate metal artifacts and improve anatomy visualization even near the boundary of the component.
Methods: The proposed reconstruction method, referred as STF-dKCR, includes a novel parameterization of the component that integrates deformation, a 3D-2D preregistration process that estimates component shape and position, and a polyenergetic forward model for x-ray propagation through the component where the spectral properties are jointly estimated. The methodology was tested on physical data of a cardiac phantom acquired on a CBCT testbench. The phantom included a simulated vessel, a metal wire emulating a pacing lead, and a small Teflon sphere attached to the vessel wall, mimicking a calcified plaque. The proposed method was also compared to the traditional FBP reconstruction and an interpolation-based metal correction method (FBP-MAR).
Results: Metal artifacts presented in standard FBP reconstruction were significantly reduced in both FBP-MAR and STF- dKCR, yet only the STF-dKCR approach significantly improved the visibility of the small Teflon target (within 2 mm of the metal wire). The attenuation of the Teflon bead improved to 0.0481 mm-1 with STF-dKCR from 0.0166 mm-1 with FBP and from 0.0301 mm-1 with FBP-MAR – much closer to the expected 0.0414 mm-1.
Conclusion: The proposed method has the potential to improve plaque visualization in coronary CT angiography in the presence of wire-shaped metal components.
Purpose: Previous work has demonstrated that structural models of surgical tools and implants can be integrated into
model-based CT reconstruction to greatly reduce metal artifacts and improve image quality. This work extends a
polyenergetic formulation of known-component reconstruction (Poly-KCR) by removing the requirement that a
physical model (e.g. CAD drawing) be known a priori, permitting much more widespread application.
Methods: We adopt a single-threshold segmentation technique with the help of morphological structuring elements
to build a shape model of metal components in a patient scan based on initial filtered-backprojection (FBP)
reconstruction. This shape model is used as an input to Poly-KCR, a formulation of known-component reconstruction
that does not require a prior knowledge of beam quality or component material composition. An investigation of
performance as a function of segmentation thresholds is performed in simulation studies, and qualitative comparisons
to Poly-KCR with an a priori shape model are made using physical CBCT data of an implanted cadaver and in patient
data from a prototype extremities scanner.
Results: We find that model-free Poly-KCR (MF-Poly-KCR) provides much better image quality compared to
conventional reconstruction techniques (e.g. FBP). Moreover, the performance closely approximates that of Poly-
KCR with an a prior shape model. In simulation studies, we find that imaging performance generally follows
segmentation accuracy with slight under- or over-estimation based on the shape of the implant. In both simulation and
physical data studies we find that the proposed approach can remove most of the blooming and streak artifacts around
the component permitting visualization of the surrounding soft-tissues.
Conclusion: This work shows that it is possible to perform known-component reconstruction without prior knowledge
of the known component. In conjunction with the Poly-KCR technique that does not require knowledge of beam
quality or material composition, very little needs to be known about the metal implant and system beforehand. These
generalizations will allow more widespread application of KCR techniques in real patient studies where the
information of surgical tools and implants is limited or not available.
In this paper, distance driven (DD) back projection image reconstruction was investigated for digital tomosysthesis. Digital tomosysthesis is an imaging technique to produce three dimensional information of the object with low radiation dosage. This paper is our new study of DD back projection for image reconstruction in digital tomosysthesis. Since DD considers that the image pixel and detector cell have width, the convolution operation is used to calculate DD coefficients. The approximation characteristics of some other methods such as ray driven method (RD) can be avoided. A computer simulation result of DD with Maximum Likelihood Expectation Maximization (MLEM) of tomosysthesis reconstruction algorithm was studied. The sequence of projection images were simulated with 25 projections and a total view angle of 48 degrees. DD with MLEM reconstruction results were demonstrated. Line profile along x direction was used to evaluate DD and RD methods. Compared with RD, the computation time in DD with MLEM to provide the reconstruction results was shorter, since the main loop of DD is over x-y plane intercepts, not over the image pixels or detectors cells. In clinical applications, both the accuracy and computation speed of implementation condition are necessary requirements. DD back projection may satisfy the required conditions.
In this paper, C-arm tomosynthesis with digital detector was investigated as a novel three dimensional (3D) imaging technique. Digital tomosythses is an imaging technique to provide 3D information of the object by reconstructing slices passing through the object, based on a series of angular projection views with respect to the object. C-arm tomosynthesis provides two dimensional (2D) X-ray projection images with rotation (∓20 angular range) of both X-ray source and detector. In this paper, four representative reconstruction algorithms including point by point back projection (BP), filtered back projection (FBP), simultaneous algebraic reconstruction technique (SART) and maximum likelihood expectation maximization (MLEM) were investigated. Dataset of 25 projection views of 3D spherical object that located at center of C-arm imaging space was simulated from 25 angular locations over a total view angle of 40 degrees. With reconstructed images, 3D mesh plot and 2D line profile of normalized pixel intensities on focus reconstruction plane crossing the center of the object were studied with each reconstruction algorithm. Results demonstrated the capability to generate 3D information from limited angle C-arm tomosynthesis. Since C-arm tomosynthesis is relatively compact, portable and can avoid moving patients, it has been investigated for different clinical applications ranging from tumor surgery to interventional radiology. It is very important to evaluate C-arm tomosynthesis for valuable applications.
Statistical iterative reconstruction exhibits particularly promising since it provides the flexibility of accurate
physical noise modeling and geometric system description in transmission tomography system. However, to solve
the objective function is computationally intensive compared to analytical reconstruction methods due to multiple
iterations needed for convergence and each iteration involving forward/back-projections by using a complex
geometric system model. Optimization transfer (OT) is a general algorithm converting a high dimensional
optimization to a parallel 1-D update. OT-based algorithm provides a monotonic convergence and a parallel
computing framework but slower convergence rate especially around the global optimal. Based on an indirect
estimation on the spectrum of the OT convergence rate matrix, we proposed a successively increasing factor-
scaled optimization transfer (OT) algorithm to seek an optimal step size for a faster rate. Compared to a
representative OT based method such as separable parabolic surrogate with pre-computed curvature (PC-SPS),
our algorithm provides comparable image quality (IQ) with fewer iterations. Each iteration retains a similar
computational cost to PC-SPS. The initial experiment with a simulated Digital Breast Tomosynthesis (DBT)
system shows that a total 40% computing time is saved by the proposed algorithm. In general, the successively
increasing factor-scaled OT exhibits a tremendous potential to be a iterative method with a parallel computation,
a monotonic and global convergence with fast rate.
KEYWORDS: X-rays, Digital breast tomosynthesis, 3D acquisition, 3D image processing, Denoising, X-ray detectors, Image resolution, Image quality, Modulation transfer functions, Iterative methods
Stationary Digital Breast Tomosynthesis (sDBT) is a carbon nanotube based breast imaging device with fast
data acquisition and decent projection resolution to provide three dimensional (3-D) volume information. To-
mosynthesis 3-D image reconstruction is faced with the challenges of the cone beam geometry and the incomplete
and nonsymmetric sampling due to the sparse views and limited view angle. Among all available reconstruction
methods, statistical iterative method exhibits particular promising since it relies on an accurate physical and
statistical model with prior knowledge. In this paper, we present the application of an edge-preserved regularizer
to our previously proposed precomputed backprojection based penalized-likelihood (PPL) reconstruction. By
using the edge-preserved regularizer, our experiments show that through tuning several parameters, resolution
can be retained while noise is reduced significantly. Compared to other conventional noise reduction techniques
in image reconstruction, less resolution is lost in order to gain certain noise reduction, which may benefit the
research of low dose tomosynthesis.
Digital tomosynthesis is an innovative imaging technology for early breast cancer detection by providing three-dimensional anatomical information with fast image acquisition and low-dose radiation. Most of current breast tomosynthesis systems utilize a design where a single x-ray tube moves along an arc above objects over a certain angular range. The mechanical movement and patient motion during the scan may degrade image quality. With a carbon nanotube–based multibeam x-ray source, a new breast tomosynthesis modality is innovated, which will potentially produce better image quality with stationary beam sources and faster scan and it enables a variety of beam distributions. In this study, several beam distributions, such as beam sources spanning along a one-dimensional (1-D) parallel configuration and sources over a two-dimensional (2-D) rectangle shape are investigated based on computer simulations. Preliminary results show that 2-D rectangle shapes outperform 1-D parallel shapes by providing better Z-resolution, enhanced image contrast, reduced out-of-plane blur and artifacts and lower reconstruction noise. These benefits may expand tomosynthesis applications to diagnostic and interventional procedures.
This paper presents a Pre-computed BackProjection (BP) based Penalized-likelihood (PPL) method for limited angle X-ray tomography based on the theory of resolution properties of regularized image reconstruction. Pre computed BP based penalty is a simplified version of the modified quadratic penalty proposed in the literature. 1
By inserting a BP equivalent estimation into a quadratic penalty, the data-related terms in the impulse response and noise reconstructed by PPL are absorbed, such that the effects of smoothing parameter of the penalty can be evaluated in advance through the simulated data. A simulation based two-step procedure is proposed to apply PPL method in real applications. It reconstructs images with predictable resolution properties by choosing a corresponding smoothing parameter. The effectiveness and robustness of the two-step strategy is validated through simulation based experiments.
KEYWORDS: Digital breast tomosynthesis, X-rays, Image restoration, Image resolution, Sensors, 3D acquisition, 3D image processing, Imaging systems, Modulation transfer functions, 3D image reconstruction
Stationary Digital Breast Tomosynthesis (s-DBT) is a carbon nanotube based breast imaging device with fast image acquisition and decent resolution. In this paper, we investigate several representative reconstruction methods with the recently improved s-DBT system and also introduce a two-step reconstruction strategy with Pre-computed Backprojection based penalized-likelihood (PPL). This strategy reconstructs three dimensional (3-D) images with a desired resolution properties by choosing the corresponding smoothing parameter, which is evaluated in advance by studying simulated data. Our experiments show that the current s-DBT system has been greatly improved with respect to the performance of image reconstructions. PPL method exhibits controllable pixel precision, high image contrast and low noise on reconstructed images. Therefore, the enhanced Contrast Noise Ratio (CNR) from PPL method benefits both micro-calcifications and mass of the breast-equivalent phantom.
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