Xianping Sun

Image enhancement based on intuitionistic fuzzy sets theory

Enhancement of images with weak edges faces great challenges in imaging applications. In this study, the authors propose a novel image enhancement approach based on intuitionistic fuzzy sets. The proposed method first divides an image into sub-object and sub-background areas, and then successively implements new fuzzification, hyperbolisation, and defuzzification operations on each area. In this way, an enhanced image is obtained, where the visual quality of region of interest (ROI) is significantly improved. Several types of images are utilised to validate the proposed method with respect to the enhancement performance. Experimental results demonstrate that the proposed algorithm not only works more stably for different types of images, but also has better enhancement performance, in comparison to conventional methods. This is a great merit of such design for discerning specific ROIs.

Detection of the mild emphysema by quantification of lung respiratory airways with hyperpolarized xenon diffusion MRI.

To demonstrate the feasibility to quantify the lung respiratory airway in vivo with hyperpolarized xenon diffusion magnetic resonance imaging (MRI), which is able to detect mild emphysema in the rat model.

NMR experimental realization of seven-qubit D-J algorithm and controlled phase-shift gates with improved precision

In this study, we report the experimental realization of seven-qubit Deutsch-Jozsa (D-J) algorithm and controlled phase-shift gates with improved precision using liquid state nuclear magnetic resonance (NMR). The experimental results have shown that transformationsUf in the seven-qubit D-J algorithm have been implemented with different pulse sequences, and whetherf is constant or balanced is determined by using only a single function call (Uf). Furthermore, we propose an experimental method to measure and correct the error in the controlled phase-shift gate that is simple and feasible in experiments, and can have precise phase shifts. These may offer the possibility of surmounting the difficulties of low signal-to-noise ratio (SNR) in multi-qubit NMR quantum computers, more complicated experimental techniques, and the increase of gate errors due to using a large number of imperfect selective pulses. These are also applied to more complicated quantum algorithms with more qubits, such as quantum Fourier transformation and Shor’s algorithm.

Experiment and dynamic simulations of radiation damping of laser-polarized liquid129Xe at low magnetic field in a flow system

Radiation damping is generally observed when a sample with high spin concentration and high gyromagnetic ratio is placed in a high magnetic field. However, we firstly observed liquid-state129Xe radiation damping with laser-enhanced nuclear polarization at low magnetic field in a flow system in which the polarization enhancement factor for the liquid-state129Xe was estimated to be 5000, and, furthermore, theoretically simulated the envelopes of the129Xe free induction decay and spectral lineshape in the presence of both relaxation and radiation damping with different pulse flip angles and ratios ofT2*/Trd. The radiation damping time constantTrd of 5 ms was derived on the basis of the simulations. The reasons of depolarization and the further possible improvements were also discussed.

Realization of a decoherence-free subspace using multiple quantum coherences

This Letter presents a two-dimensional nuclear magnetic resonance (NMR) approach for constructing a two-logical-qubit decoherence-free subspace (DFS) by using four multiple-quantum coherences of a CH3 spin system as logical qubits. The three protons in this spin system are magnetically equivalent and can only be used as a single qubit in one-dimensional NMR. We have experimentally demonstrated that our DFS can protect against more types of decoherences than those of the one composed of four noisy physical qubits all with different chemical shifts. This idea may provide new insights into extending qubit systems in the sense that it effectively utilizes the magnetically equivalent nuclei.

Simultaneous assessment of both lung morphometry and gas exchange function within a single breath‐hold by hyperpolarized 129Xe MRI

During the measurement of hyperpolarized 129Xe magnetic resonance imaging (MRI), the diffusion‐weighted imaging (DWI) technique provides valuable information for the assessment of lung morphometry at the alveolar level, whereas the chemical shift saturation recovery (CSSR) technique can evaluate the gas exchange function of the lungs. To date, the two techniques have only been performed during separate breaths. However, the request for multiple breaths increases the cost and scanning time, limiting clinical application. Moreover, acquisition during separate breath‐holds will increase the measurement error, because of the inconsistent physiological status of the lungs. Here, we present a new method, referred to as diffusion‐weighted chemical shift saturation recovery (DWCSSR), in order to perform both DWI and CSSR within a single breath‐hold. Compared with sequential single‐breath schemes (namely the ‘CSSR + DWI’ scheme and the ‘DWI + CSSR’ scheme), the DWCSSR scheme is able to significantly shorten the breath‐hold time, as well as to obtain high signal‐to‐noise ratio (SNR) signals in both DWI and CSSR data. This scheme enables comprehensive information on lung morphometry and function to be obtained within a single breath‐hold. In vivo experimental results demonstrate that DWCSSR has great potential for the evaluation and diagnosis of pulmonary diseases.

Detection of smoke-induced pulmonary lesions by hyperpolarized (129) Xe diffusion kurtosis imaging in rat models.

To demonstrate that hyperpolarized (HP) xenon diffusion kurtosis imaging (DKI) is able to detect smoke‐induced pulmonary lesions in rat models.

Quantitative evaluation of pulmonary gas-exchange function using hyperpolarized 129Xe CEST MRS and MRI

Hyperpolarized 129Xe gas MR has been a powerful tool for evaluating pulmonary structure and function due to the extremely high enhancement in spin polarization, the good solubility in the pulmonary parenchyma, and the excellent chemical sensitivity to its surrounding environment. Generally, the quantitative structural and functional information of the lung are evaluated using hyperpolarized 129Xe by employing the techniques of chemical shift saturation recovery (CSSR) and xenon polarization transfer contrast (XTC). Hyperpolarized 129Xe chemical exchange saturation transfer (Hyper‐CEST) is another method for quantifying the exchange information of hyperpolarized 129Xe by using the exchange of xenon signals according to its different chemical shifts, and it has been widely used in biosensor studies in vitro. However, the feasibility of using hyperpolarized 129Xe CEST to quantify the pulmonary gas exchange function in vivo is still unclear. In this study, the technique of CEST was used to quantitatively evaluate the gas exchange in the lung globally and regionally via hyperpolarized 129Xe MRS and MRI, respectively. A new parameter, the pulmonary apparent gas exchange time constant (Tapp), was defined, and it increased from 0.63 s to 0.95 s in chronic obstructive pulmonary disease (COPD) rats (induced by cigarette smoke and lipopolysaccharide exposure) versus the controls with a significant difference (P = 0.001). Additionally, the spatial distribution maps of Tapp in COPD rats pulmonary parenchyma showed a regionally obvious increase compared with healthy rats. These results indicated that hyperpolarized 129Xe CEST MR was an effective method for globally and regionally quantifying the pulmonary gas exchange function, which would be helpful in diagnosing lung diseases that are related to gas exchange, such as COPD.

Lung morphometry using hyperpolarized 129Xe multi‐b diffusion MRI with compressed sensing in healthy subjects and patients with COPD

Purpose To demonstrate the feasibility of compressed sensing (CS) to accelerate the acquisition of hyperpolarized (HP) 129Xe multi‐b diffusion MRI for quantitative assessments of lung microstructural morphometry. Methods Six healthy subjects and six chronic obstructive pulmonary disease (COPD) subjects underwent HP 129Xe multi‐b diffusion MRI (b = 0, 10, 20, 30, and 40 s/cm2). First, a fully sampled (FS) acquisition of HP 129Xe multi‐b diffusion MRI was conducted in one healthy subject. The acquired FS dataset was retrospectively undersampled in the phase encoding direction, and an optimal twofold undersampled pattern was then obtained by minimizing mean absolute error (MAE) between retrospective CS (rCS) and FS MR images. Next, the FS and CS acquisitions during separate breath holds were performed on five healthy subjects (including the above one). Additionally, the FS and CS synchronous acquisitions during a single breath hold were performed on the sixth healthy subject and one COPD subject. However, only CS acquisitions were conducted in the rest of the five COPD subjects. Finally, all the acquired FS, rCS and CS MR images were used to obtain morphometric parameters, including acinar duct radius (R), acinar lumen radius (r), alveolar sleeve depth (h), mean linear intercept (Lm), and surface‐to‐volume ratio (SVR). The Wilcoxon signed‐rank test and the Bland–Altman plot were employed to assess the fidelity of the CS reconstruction. Moreover, the t‐test was used to demonstrate the effectiveness of the multi‐b diffusion MRI with CS in clinical applications. Results The retrospective results demonstrated that there was no statistically significant difference between rCS and FS measurements using the Wilcoxon signed‐rank test (P > 0.05). Good agreement between measurements obtained with the CS and FS acquisitions during separate breath holds was demonstrated in Bland–Altman plots of slice differences. Specifically, the mean biases of the R, r, h, Lm, and SVR between the CS and FS acquisitions were 1.0%, 2.6%, −0.03%, 1.5%, and −5.5%, respectively. Good agreement between measurements with the CS and FS acquisitions was also observed during the single breath‐hold experiments. Furthermore, there were significant differences between the morphometric parameters for the healthy and COPD subjects (P < 0.05). Conclusions Our study has shown that HP 129Xe multi‐b diffusion MRI with CS could be beneficial in lung microstructural assessments by acquiring less data while maintaining the consistent results with the FS acquisitions.

Considering low-rank, sparse and gas-inflow effects constraints for accelerated pulmonary dynamic hyperpolarized 129 Xe MRI

Dynamic hyperpolarized (HP) 129Xe MRI is able to visualize the process of lung ventilation, which potentially provides unique information about lung physiology and pathophysiology. However, the longitudinal magnetization of HP 129Xe is nonrenewable, making it difficult to achieve high image quality while maintaining high temporal-spatial resolution in the pulmonary dynamic MRI. In this paper, we propose a new accelerated dynamic HP 129Xe MRI scheme incorporating the low-rank, sparse and gas-inflow effects (Lu202f+u202fSu202f+u202fG) constraints. According to the gas-inflow effects of HP gas during the lung inspiratory process, a variable-flip-angle (VFA) strategy is designed to compensate for the rapid attenuation of the magnetization. After undersampling k-space data, an effective reconstruction algorithm considering the low-rank, sparse and gas-inflow effects constraints is developed to reconstruct dynamic MR images. In this way, the temporal and spatial resolution of dynamic MR images is improved and the artifacts are lessened. Simulation and in vivo experiments implemented on the phantom and healthy volunteers demonstrate that the proposed method is not only feasible and effective to compensate for the decay of the magnetization, but also has a significant improvement compared with the conventional reconstruction algorithms (P-values are less than 0.05). This confirms the superior performance of the proposed designs and their ability to maintain high quality and temporal-spatial resolution.