2013, 2(5):1-6. DOI: 10.12146/j.issn.2095-3135.201309001
Abstract:Partially separability (PS) model is a sparse sampling imaging model which can achieve high spatiotemporal resolution for dynamic magnetic resonance imaging. However, the PS model needs a long scan time to collect enough data for image reconstruction, which hinders its applications in clinic. To address this issue, a novel approach based on parallel sampling and image reconstruction algorithm was introduced to shorten the PS scan time in this paper. Numerical simulation and in vivo cardiac experiment results demonstrate that the proposed method can accelerate the PS sampling speed by 2-3 times without any penalty of the reconstructed image quality.
2013, 2(5):7-10. DOI: 10.12146/j.issn.2095-3135.201309002
Abstract:At 3T, conventional breath-hold T2-weighted imaging in the abdomen by HASTE is limited by SAR constraint and B1 inhomogeneity. This work shows that PSIF offers good T2 contrast in abdomen under 3T with a flip angle around 30 to 40 degrees, drastically reducing SAR and is more robust than HASTE. For 2D PSIF in healthy volunteers, the SNR of liver is around 17 and spleen-liver CNR is around 18, which is sufficient for diagnostic purpose. The short TR in PSIF shortens the scan time to 1s per slice, and eliminates the need for breath holding or respiratory triggering.
2013, 2(5):11-17. DOI: 10.12146/j.issn.2095-3135.201309003
Abstract:Hemispheric asymmetry is believed to increase the efficiency of information processing, especially for the multitask performance. Regional variation of cerebral lateralization was observed in healthy elderly as well as in patients with Alzheimer’s disease (AD). However, the extent and degree of the alterations in the cerebral lateralization in AD patients remained controversial. In the current study, high-resolution T1-weighted magnetic resonance images (T1WI) and diffusion tensor images (DTI) were retrieved consecutively for a total of 78 AD patients and healthy elderly from the open database of ADNI (http://adni.loni.ucla.edu/). The entire brain of each subject was parcellated into 34 regions of interest (ROIs) for each hemisphere. Five variables including cortical surface area, curvature index, cortical thickness, subjacent white matter volume, and fractional anisotropy (FA) of white matter fiber tracts were calculated for each ROI. Inter-hemisphere difference of the aforementioned parameters was analyzed using univariate and multivariate models for each ROI. The statistics parametric images were mapped on the anatomy template to facilitate visual inspection. Significant morphological variation between hemispheres was identified mainly in the lateral prefrontal cortex and temporal lobe, medial parietal lobe and limbic system which were vulnerable in both healthy aging and AD. Cerebral lateralization reduced significantly in AD patient in comparison with healthy elderly, especially in the entorhinal cortex , the gray matter lateralization and white matter lateralization both vanished. Univariate and multivariate analyses of the alterations in the cerebral lateralization might add extra values of the morphological information in evaluating the disease dynamic of AD and other dementia disorders.
2013, 2(5):18-21. DOI: 10.12146/j.issn.2095-3135.201309004
Abstract:A series of multi-contrast MR images are usually required in various MR applications, such as T1 and T2 mappings, which provide quantitative information of inherent tissue properties for diagnosis purpose. However, its clinical application is limited by the long scanning time. The emerging theory of compressed sensing has shown great potential in accelerating MR acquisitions. Recently, a principal component analysis based method has been proposed exploiting the temporal sparsity via truncated PCs based on the knowledge of the analytic model and possible parameter range. However, it may generate model errors when such prior information is not accurate. In this work, the support of the PC coefficients were detected in a more adaptive way using iterative support detection. Reconstructions based on two knee data sets were conducted to demonstrate the effectiveness of the proposed method.
2013, 2(5):22-29. DOI: 10.12146/j.issn.2095-3135.201309005
Abstract:Two dimensional turbo spin echo (2DTSE) has been the work-horse in routine MR examinations. With the combination of the slice interleaving, 2DTSE is applied to the whole brain imaging rapidly in a short time. Yet, the sampling efficiency of TSE is limited by high specific absorption rate (SAR) and strong T2 decay when it is used for 3D imaging where interleaving cannot be used. SPACE (Sampling Perfection with Application-optimized Contrasts by using different flip angle Evolutions) is a TSE variant that dramatically reduces the SAR and T2 blurring by using ultra-long echo train acquisition and non-spatially-selective refocusing RF-pulses with variable flip angles. In this paper, the basic principles of SPACE are introduced and its clinical applications are discussed.
2013, 2(5):30-33. DOI: 10.12146/j.issn.2095-3135.201309006
Abstract:Cardiac magnetic resonance cine imaging is more commonly used in clinical imaging method for cardiac function analysis. A real-time free breathing cardiac magnetic resonance cine imaging data processing method, which is an effective way for rapid detection of end-diastolic (ED) and end-systolic (ES) phases at end-expiration graphically, was proposed in this paper. By placing the appropriate reference line in the frames, respiratory motion and cardiac motion could be observed during the entire data collection process of subjects. According to the movements of chest wall/diaphragm and other organs to obtain respiratory motion, the time period of end-expiration could be quickly determined; and then in the time period, cardiac end-diastolic and end-systolic as two important cardiac phases for cardiac function analysis were automatically identified according to the size of the left ventricle chamber. Finally, in accordance with specified requirements, automatically detected images were saved to facilitate subsequent cardiac function analysis. This method significantly reduces data processing time and therefore it has good clinical values and prospects.
2013, 2(5):34-41. DOI: 10.12146/j.issn.2095-3135.201309007
Abstract:Noninvasive visualization of living tissues is in great demand in the field of medical and biological studies. High resolution ultrasound imaging has made it possible to image small structures with fine spatial resolution and been widely used in the biomedical field including the dermatology, ophthalmology, intravascular imaging, and small animal imaging. The individual study is unique in nature and requires different utilization of the imaging system, such as different transducer characteristics, data acquisition strategies, signal processing methods, and image reconstruction, display and storage. Therefore, there is a demand for a flexible and open imaging system to allow users to customize the system for various studies and have full access to experimental data. In this paper, a real-time compact and open system is developed for customized high resolution ultrasound imaging studies. The system was based on high-speed field programmable gate array (FPGA) embedded in compact printed circuit board (PCB) to achieve flexible ultrasound imaging. The system structure could easily be modified by the users for customized applications. Testing results show that the system can offer a very flexible setting with B-mode imaging, modulated excitation imaging, Doppler imaging, intravascular imaging, and multi-modality imaging for high resolution biomedical applications.
2013, 2(5):42-47. DOI: 10.12146/j.issn.2095-3135.201309008
Abstract:Micro-scale manipulation is a technology of manipulating micro/nanoparticles precisely including trapping, filtering, moving and sorting particles like cells, biomacromolecules and nano drugs, with a vast array of potential uses in biomedicine, chemical analysis, materials science and other fields. By applying acoustic waves, acoustic manipulation has some advantages including non-contact, penetrability and versatility, no biochemical decorations to particles. In recent years, the manipulation of particles based on surface acoustic wave (SAW) has attracted wide attention with the development of MEMS technology and microfluidics science. Due to the advantages such as high frequency, localization of the energy and easy integration with other on-chip units, the microfluidic chip is an excellent tool to observe the manipulation of cells, microbubbles and other bioparticles. In this paper, recent advancements in acoustic manipulation using acoustic steaming and radiation force were discussed. In addition, some perspectives on the future development of this dynamic field were proposed as well.
2013, 2(5):48-52. DOI: 10.12146/j.issn.2095-3135.201309009
Abstract:Recently several ultrasound-based techniques for the estimation of soft tissue elasticity are widely used in clinical, but these methods are usually based on the theory that the organization is pure elastic and neglect the viscosity of the organization. To calculate the displacement and strain profiles based on the theory of mechanics of viscoelasticity, the finite element analysis method is applied. This method plays an important assistant role in theoretical analysis of viscoelastic imaging, different condition of soft tissues and effects of mechanical parameters on soft tissues. Using this method, different viscoelastic parameters of soft tissues and various acoustic stimulus can be studied. Finite element analysis results show that the organization’s viscosity can’t be ignored in the study of elasticity imaging.
2013, 2(5):53-59. DOI: 10.12146/j.issn.2095-3135.201309010
Abstract:Photoacoustic tomography (PAT), emerging approximately one decade ago, is a novel biomedical imaging modality based on the use of laser-generated ultrasound. PAT combines the high contrast and spectroscopic specificity of optical imaging with the high spatial resolution and large penetration depth (7-10 cm) of ultrasonography. With the capability to image important physiological parameters such as the total hemoglobin concentration, oxygen saturation, and even the metabolic rate of oxygen, it is highly complementary to conventional ultrasonography, and has opened up many new opportunities for novel clinical applications. Up to now, PAT has demonstrated a wide array of applications in both the clinic and basic biomedical research, in particular, for the diagnosis and therapy guidance of cancer, cardiovascular diseases, and abnormalities related to the microcirculation. In this article, we summarize the progress on some new PAT techniques developed by us during the past few years, including blind deconvolution, compressed sensing, and novel molecular imaging techniques. In addition, we briefly review the state of the art of the technology development of PAT, with particular emphases on its applications in breast cancer diagnosis, noninvasive sentinel lymph node mapping, and intravascular imaging.
2013, 2(5):60-63. DOI: 10.12146/j.issn.2095-3135.201309011
Abstract:A visible nanoparticle was constructed via recombination of stearic acid modified polyethyleneimine (stearic-PEI) and superparamagnetic iron oxide (SPIO) to combine with DNA. Then through tail vein injection, the stearic-PEI/SPIO/DNA nanoparticles were efficiently delivered to BABL/c female mice that were visualized by MRI (Magnetic Resonance Imaging) and confirmed by histology. The MRI results showed that the experimental group’s T2 signal intensities significantly decrease at 0.5 h after injection, just 35% of that in the control group. Although the experimental group’s T2 signal intensities slightly recovered at 48 h after injection, there were still obvious differences between the control group and experimental group. The histological staining showed that the visible gene deliver nanocomplexes could pass through vascular endothelial cell into liver tissues and release DNA into cells, but with low gene expression effect. From the foregoing results, the nanoparticles have excellent magnetic resonance imaging performance, but low gene transfection efficiency via tail vein injection.
2013, 2(5):64-66. DOI: 10.12146/j.issn.2095-3135.201309012
Abstract:Carbon nanotube (CNT) cathode based X-ray source is a leading field of X-ray CT technology in recent years. Compared with traditional thermal emission X-ray source, CNT X-ray source has characteristics of miniaturization, high resolution of time and programmable emission. Multi-beam X-ray source for stationary X-ray scanner is one of the most important applications of CNT X-ray source. In this paper, the development of CNT cathode based multi-beam X-ray source were introduced.
2013, 2(5):67-72. DOI: 10.12146/j.issn.2095-3135.201309013
Abstract:This paper proposes a generic scheme for dental CT image segmentation, which is based on mathematical morphology. The implementation of morphological reconstruction and filtering techniques is used to process the image, with the aim of identifying teeth within the oral cavity from a human specimen. Initial studies using dental CT images have demonstrated the feasibility of the proposed scheme for segmenting teeth from the surrounding biological matter.
2013, 2(5):73-82. DOI: 10.12146/j.issn.2095-3135.201309014
Abstract:Dental CT as a dedicated CT of human maxillofacial is widely used in clinical procedures including preoperative evaluation of impacted teeth in bone, dental implants, diagnosis of temporomandibular joint disease, jaw cysts and tumors, orthodontics, and teeth marrow disease, etc. Although there are some Dental CT machines abroad, they are expensive and there are some shortcomings in their functions and technical indexes. Dental CT has the following advantages: as no destruction, high resolution, no image overlapping, no image distortion and low dose. By virtue of high resolution and no image distortion, this CT system can be widely applied in a number of dental treatments such as filling, tooth-planting, periodontal disease, dental surgery etc.
2013, 2(5):83-86. DOI: 10.12146/j.issn.2095-3135.201309015
Abstract:The research on 3-D tracking and positioning based on C-arm is mainly completed by the prediction algorithm. This paper mainly introduces some popular prediction algorithms caused by respiration motion which can change the targets position irregularly. Meanwhile, this paper has made a summary and induction about the prediction algorithms. And we discuss the development trends as well.