Journal of X-Ray Science and Technology

BACKGROUND: Multi-phase CT images are obtained sequentially after the injection of contrast agents so that there is a large amount of local deformation between images due to the respiratory and heart motion. Therefore, a non-rigid registration technique is required in order to establish the anatomical correspondence between the multi-phase CT images for liver CAD (computer-aided diagnosis).

OBJECTIVE: In this paper, we propose the automatic detection method of hepatocellular carcinomas using the non-rigid registration method of multi-phase CT images.

METHODS: Global movements between multi-phase CT images are aligned by rigid registration based on normalized mutual information. Local deformations between multi-phase CT images are modeled by non-rigid registration based on B-spline deformable model. After the registration of multi-phase CT images, hepatocellular carcinomas are automatically detected by analyzing the original and subtraction information of the registered multi-phase CT images.

RESULTS: We applied our method to twenty five multi-phase CT datasets. Experimental results showed that the multi-phase CT images were accurately aligned. All of the hepatocellular carcinomas including small size ones in our 25 subjects were accurately detected using our method.

CONCLUSION: We conclude that our method is useful for detecting hepatocellular carcinomas.

A perfect knowledge of a defect shape is determinant for the analysis step in automatic radiographic inspection. Image segmentation is carried out on radiographic images and extract defects indications. This paper deals with weld defect delineation in radiographic images. The proposed method is based on a new statistics-based explicit active contour. An association of local and global modeling of the image pixels intensities is used to push the model to the desired boundaries. Furthermore, other strategies are proposed to accelerate its evolution and make the convergence speed depending only on the defect size as selecting a band around the active contour curve. The experimental results are very promising, since experiments on synthetic and radiographic images show the ability of the proposed model to extract a piece-wise homogenous object from very inhomogeneous background, even in a bad quality image.

Phase contrast imaging (PCI) is a new physical and biochemical technique. Practical biomedical applications combine PCI with computer tomography (CT), Phase contrast CT (PC-CT) can reconstruct 3D images of samples. How to reconstruct high quality image at a low radiation dose level is a hot topic for PC-CT. In order to reduce radiation dose, a strategy is to collect incomplete projection data by few-view projection data. This work presents a reconstruction method for incomplete data PC-CT. It is based on an algebraic iteration reconstruction algorithm and combined with an anisotropic diffusion model to reduce aliasing distortions.

To validate the availability of this method, the research carried out a computer-simulated and real experimental synchrotron data. The computer-simulated and real data results demonstrate that the presented method can improve the convergence speed of image reconstruction and reduce the aliasing distortions by incomplete projection data for PC-CT. However, there is no proof that this is true for all kinds of structures.

We found a way to optimize the image quality and reduce the exposure dose of patients through the proper activity combination of the automatic exposure control system chamber for the dose optimization when examining the pelvic anteroposterior side using the phantom of the human body standard model. We set 7 combinations of the chamber of automatic exposure control system. The effective dose was yielded by measuring five times for each according to the activity combination of the chamber for the dose measurement. Five radiologists with more than five years of experience evaluated the image through picture archiving and communication system using double blind test while classifying the 6 anatomical sites into 3-point level (improper, proper, perfect). When only one central chamber was activated, the effective dose was found to be the highest level, 0.287 mSv; and lowest when only the top left chamber was used, 0.165 mSv. After the subjective evaluation by five panel members on the pelvic image was completed, there was no statistically meaningful difference between the 7 chamber combinations, and all had good image quality. When testing the pelvic anteroposterior side with digital radiography, we were able to reduce the exposure dose of patients using the combination of the top right side of or the top two of the chamber.

BACKGROUND: The traditional Bayesian priors for maximum a posteriori (MAP) reconstruction methods usually incorporate local neighborhood interactions that penalize large deviations in parameter estimates for adjacent pixels; therefore, only local pixel differences are utilized. This limits their abilities of penalizing the image roughness.

OBJECTIVE: To achieve high-quality PET image reconstruction, this study investigates a MAP reconstruction strategy by incorporating a nonlocal means induced (NLMi) prior (NLMi-MAP) which enables utilizing global similarity information of image.

METHODS: The present NLMi prior approximates the derivative of Gibbs energy function by an NLM filtering process. Specially, the NLMi prior is obtained by subtracting the current image estimation from its NLM filtered version and feeding the residual error back to the reconstruction filter to yield the new image estimation.

RESULTS: We tested the present NLMi-MAP method with simulated and real PET datasets. Comparison studies with conventional filtered backprojection (FBP) and a few iterative reconstruction methods clearly demonstrate that the present NLMi-MAP method performs better in lowering noise, preserving image edge and in higher signal to noise ratio (SNR).

CONCLUSIONS: Extensive experimental results show that the NLMi-MAP method outperforms the existing methods in terms of cross profile, noise reduction, SNR, root mean square error (RMSE) and correlation coefficient (CORR).

Interior tomography as a promising X-ray imaging technique has received increasing attention in medical imaging field. In our previous works, we proposed a high-order total variation (HOT) minimization method for interior tomography and proved that the region of interest (ROI) can be reconstructed accurately by minimizing the HOT if the object image is piecewise polynomial within the ROI. In this paper, we propose a modified HOT (MHOT) and develop a fast MHOT minimization algorithm for interior tomography, based on split Bregman iteration and ordered-subset simultaneous algebraic reconstruction techniques (OS-SART). Numerical simulation demonstrates that our algorithm is computationally efficient and can be applied to obtain high-quality reconstructed image.

BACKGROUND: Technologies employing digital X-ray devices are developed for mobile settings.

OBJECTIVE: To develop a mobile digital X-ray fluoroscopy (MDF) for intraoperative guidance, using a novel flat panel detector to focus on diagnostics in outpatient clinics, operating and emergency rooms.

METHODS: An MDF for small-scale field diagnostics was configured using an X-ray source and a novel flat panel detector. The imager enabled frame rates reaching 30 fps in full resolution fluoroscopy with maximal running time of 5 minutes. Signal-to-noise (SNR), contrast-to-noise (CNR), and spatial resolution were analyzed. Stray radiation, exposure radiation dose, and effective absorption dose were measured for patients.

RESULTS: The system was suitable for small-scale field diagnostics. SNR and CNR were 62.4 and 72.0. Performance at 10% of MTF was 9.6 lp/mm (53 μ m) in the no binned mode. Stray radiation at 100 cm and 150 cm from the source was below 0.2 μ Gy and 0.1 μ Gy. Exposure radiation in radiography and fluoroscopy (5 min) was 10.2 μ Gy and 82.6 mGy. The effective doses during 5-min-long fluoroscopy were 0.26 mSv (wrist), 0.28 mSv (elbow), 0.29 mSv (ankle), and 0.31 mSv (knee).

CONCLUSIONS: The proposed MDF is suitable for imaging in operating rooms.

Radiation dose and image quality from a recently introduced mobile CT imaging system are presented. Radiation dose was measured using a conventional 100 mm pencil ionization chamber and CT polymethylmetacrylate (PMMA) body and head phantoms. Image quality was evaluated with a CATPHAN 500 phantom. Spatial resolution, low contrast resolution, Modulation Transfer Function (MTF), and Normalized Noise Power Spectrum (NNPS) were analyzed. Radiation dose and image quality were compared to those from a multi-detector CT scanner (Siemens Sensation 64). Under identical technique factors radiation dose (mGy/mAs) from the AIRO mobile CT system (AIRO) is higher than that from a 64 slice CT scanner. Based on MTF analysis, both Soft and Standard filters of the AIRO system lost resolution quickly compared to the Sensation 64 slice CT. The Siemens scanner had up to 7 lp/cm for the head FOV and H40 kernel and up to 5 lp/cm at body FOV for the B40f kernel. The Standard kernel in the AIRO system was evaluated to have 3 lp/cm and 4 lp/cm for the body and head FOVs respectively. NNPS of the AIRO shows low frequency noise due to ring-like artifacts which may be caused by detector calibration or lack of artifact reducing image post-processing. Due to a higher dose in terms of mGy/mAs at both head and body FOV, the contrast to noise ratio is higher in the AIRO system than in the Siemens scanner. However detectability of the low contrast objects is poorer in the AIRO due to the presence of ring artifacts in the location of the targets.

OBJECTIVE: The digital human modeling combines information technology with bioscience, applied to analog study from DNA molecule and protein to cell and tissue, as well as organ. It has been widely implemented in various fields such as aviation, national defense, film and television, sports and medical treatment. This paper sorts relative research achievements and progress in recent years and summarizes issues and challenges of research work. The purpose of this paper is to provide references for the development of Digital Human Modeling.

METHODS: Basing on the development plans proposed by Federation of American Scientists (FAS) and current theories, we sorted academic achievements and relative references since the beginning of the digital human concept until 2014 into four aspects, which were named as Visible Human, Virtual Physical Human, Virtual Physiological Human, and Intelligent Virtual Human. We collected information of data acquisition, data analysis and dataset establishment for Visible Human. We outlined the Virtual Physical Human references in four physical categories, including radiation, ultrasonic, electrics, and mechanics. For Virtual Physiological Human, relative researches related to the physiological and biochemical changes of human body were categorized in four aspects as gene molecules, cells, and organs. Relative researches of Virtual Brain Human were mainly concentrated on virtual human brain and virtual human control.

RESULTS: According to the differences in investigations and applications requirements of Digital Human in all aspects, we classified, analyzed and concluded extensive preference data. The overall plan of Digital Human, as well as technical routes, work plans, present states, goals, results and application value in each stage of research was summarized. We discussed the technical issues existing in each aspect of Digital Human, along with the urgent key technologies including data collection, data processing, and modeling.

CONCLUSION: Analyzing the core technologies and the general technical schemes in the field of Digital Human, this paper summarizes the technical solutions, research results and technical problems of major researchers. The future prospects of Digital Human are reviewed.

A complete investigation of urinary stone components could help to effectively evaluate and treat pathologies, and prevent recurrence. The choice of the most effective technique to use is not simple and depends on the type of sample analysed, cost and time of analysis and experience of the operator. An integrated technical approach is the best option for a stone analysis by choosing from the various techniques proposed on the basis of their characteristics, advantages and disadvantages.