离体龋齿的光热锁相成像检测试验

牙齿龋损是人类一种广泛存在的口腔疾病,如何能够尽早的发现早期龋齿,对患者牙齿龋损的预防与治疗具有重要意义。介绍了基于光热效应的光热锁相热成像技术,光热锁相热成像技术具有无损伤、高效率及探测面积大等优势被广泛应用于各类材料的无损检测。基于光热锁相热成像技术原理对人为模拟龋损的人类离体牙齿组织进行成像检测试验研究。首先开展了对不同模拟龋损位置离体牙齿的光热锁相成像试验,采用防酸指甲油对牙齿组织测试面进行开窗受控龋损(开窗大小为5 mm×5 mm),其中模拟龋损部位分别选择在牙齿组织的邻接面及牙颌面。试验结果显示,牙齿组织模拟龋损位置热波幅值增大,相位滞后增大且光热锁相成像的幅值图与相位图与X射线成像相比对模拟龋损部位表现出高敏感及高特异性;光热锁相成像技术对邻接面龋损比牙颌面龋损具有较高特异性。其次开展了对平滑面牙齿组织样本的多天(0,1,2,4及6 d)模拟龋损光热锁相成像跟踪试验研究,牙齿组织龋损程度采用X射线方法进行量化。试验结果表明,当龋损时间小于6 d时,X射线方法无法对龋损位置进行有效识别,而采用光热锁相热成像技术检测模拟龋损1 d的牙齿组织时,幅值差为3.82,相位差为10.57°,证明光热锁相热成像方法对牙齿组织龋损具有较高敏感性。提取的光热锁相成像幅值与相位与龋损时间具有良好的相关性。     

Equivalent cross-relaxation rate imaging positively correlates with pathological grade and cell density of adipocytic tumors

Objective

Equivalent cross-relaxation rate imaging (ECRI) is an MRI technique used to evaluate qualitative changes in protein-water interactions. We aimed to prospectively evaluate the utility of ECRI for classification of adipocytic tumors.

Materials and Methods

Institutional Review Board approval was obtained and all patients provided informed consent. Study participants included 40 patients with adipocytic tumors who were diagnosed with lipomas (n = 22), atypical lipomatous tissue/well-differentiated liposarcoma (ALT/WDL; n = 9), myxoid/round cell liposarcoma (MyL; n = 6), and dedifferentiated liposarcoma (DDL; n = 3), and 20 control patients for whom subcutaneous fat in the buttock or thigh was analyzed.

Results

Mean ECR values of lipomas, ALT/WDL, and subcutaneous fat were low, and those of MyL and DDL were high. Mean ECR values of MyL and DDL were significantly higher than those of ALT/WDL. The cut-off value was 5.1%. There was a positive correlation between ECR value, pathological grade, and cell density in adipocytic tumors.

Conclusion

The ECR value positively correlates with pathological grade and cell density of adipocytic tumors. Our findings suggest that ECRI is a useful method for preoperative evaluation of adipocytic tumors.     

Non-Gaussian water diffusion kurtosis imaging of prostate cancer

Purpose

To evaluate the non-Gaussian water diffusion properties of prostate cancer (PCa) and determine the diagnostic performance of diffusion kurtosis (DK) imaging for distinguishing PCa from benign tissues within the peripheral zone (PZ), and assessing tumor lesions with different Gleason scores.

Materials and Methods

Nineteen patients who underwent diffusion weighted (DW) magnetic resonance imaging using multiple b-values and were pathologically confirmed with PCa were enrolled in this study. Apparent diffusion coefficient (ADC) was derived using a monoexponential model, while diffusion coefficient (D) and kurtosis (K) were determined using a DK model. Differences between the ADC, D and K values of benign PZ and PCa, as well as those of tumor lesions with Gleason scores of 6, 7 and ≥ 8 were assessed. Correlations between parameters D and K in PCa were analyzed using Pearson’s correlation coefficient. ADC, D and K values were correlated with Gleason scores of 6, 7 and ≥ 8, respectively.

Results

ADC and D values were significantly (p < 0.001) lower in PCa (0.79 ± 0.14 μm²/ms and 1.56 ± 0.23 μm²/ms, respectively) compared to benign PZ (1.23 ± 0.19 μm²/ms and 2.54 ± 0.24 μm²/ms, respectively). K values were significantly (p < 0.001) greater in PCa (0.96 ± 0.20) compared to benign PZ (0.59 ± 0.08). D and K showed fewer overlapping values between benign PZ and PCa compared to ADC. There was a strong negative correlation between D and K values in PCa (Pearson correlation coefficient r = − 0.729; p < 0.001). ADC and K values differed significantly in tumor lesions with Gleason scores of 6, 7 and ≥ 8 (p < 0.001 and p = 0.001, respectively), although no significant difference was detected for D values (p = 0.325). Significant correlations were found between the ADC value and Gleason score (r = − 0.828; p < 0.001), as well as the K value and Gleason score (r = 0.729; p < 0.001).

Conclusion

DK model may add value in PCa detection and diagnosis. K potentially offers a new metric for assessment of PCa.     

Improved l1-SPIRiT using 3D walsh transform-based sparsity basis

l1-SPIRiT is a fast magnetic resonance imaging (MRI) method which combines parallel imaging (PI) with compressed sensing (CS) by performing a joint l1-norm and l2-norm optimization procedure. The original l1-SPIRiT method uses two-dimensional (2D) Wavelet transform to exploit the intra-coil data redundancies and a joint sparsity model to exploit the inter-coil data redundancies. In this work, we propose to stack all the coil images into a three-dimensional (3D) matrix, and then a novel 3D Walsh transform-based sparsity basis is applied to simultaneously reduce the intra-coil and inter-coil data redundancies. Both the 2D Wavelet transform-based and the proposed 3D Walsh transform-based sparsity bases were investigated in the l1-SPIRiT method. The experimental results show that the proposed 3D Walsh transform-based l1-SPIRiT method outperformed the original l1-SPIRiT in terms of image quality and computational efficiency.     

Evaluation of aortic stenosis severity using 4D flow jet shear layer detection for the measurement of valve effective orifice area

Aims

The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.

Methods and Results

An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOA_JSLD-2D and EOA_JSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOA_CE) with the 2D PC-MRI velocity field and compared to the EOA_JSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA = 0.78 cm²) and experimental measurement (EOA_JSLD-4D = 0.78 ± 0.01 cm²) for peak velocities ranging from 0.9 to 3.7 m/s. In-vivo results showed good correlation and agreement between EOA_JSLD-2D and EOA_CE (r = 0.91, p < 0.001; bias: − 0.01 ± 0.38 cm²; agreement limits: 0.75 to − 0.77 cm²), and between EOA_JSLD-4D and EOA_CE (r = 0.95, p < 0.001; bias: − 0.09 ± 0.26 cm²; limits: 0.43 to − 0.62 cm²).

Conclusion

This study demonstrates the feasibility of measuring EOA_JSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOA_CE measurement variability.     

Correction strategy for diffusion-weighted images corrupted with motion: application to the DTI evaluation of infants' white matter

Objective

Diffusion imaging techniques such as DTI and HARDI are difficult to implement in infants because of their sensitivity to subject motion. A short acquisition time is generally preferred, at the expense of spatial resolution and signal-to-noise ratio. Before estimating the local diffusion model, most pre-processing techniques only register diffusion-weighted volumes, without correcting for intra-slice artifacts due to motion or technical problems. Here, we propose a fully automated strategy, which takes advantage of a high orientation number and is based on spherical-harmonics decomposition of the diffusion signal.

Material and methods

The correction strategy is based on two successive steps: 1) automated detection and resampling of corrupted slices; 2) correction for eddy current distortions and realignment of misregistered volumes. It was tested on DTI data from adults and non-sedated healthy infants.

Results

The methodology was validated through simulated motions applied to an uncorrupted dataset and through comparisons with an unmoved reference. Second, we showed that the correction applied to an infant group enabled to improve DTI maps and to increase the reliability of DTI quantification in the immature cortico-spinal tract.

Conclusion

This automated strategy performed reliably on DTI datasets and can be applied to spherical single- and multiple-shell diffusion imaging.     

高光谱技术结合CARS算法的库尔勒香梨可溶性固形物定量测定

由于高光谱数据量大、维数高,光谱噪声明显、散射严重等特征导致光谱建模时关键变量提取较为困难,同时,高光谱图像的获取会受非单色光、杂散光、温度等多种因素的影响,从而使高光谱数据与待测性质之间有一定非线性关系。为此,提出采用正自适应加权算法(CARS)对可见-近红外高光谱高维数据进行关键变量筛选,并与全光谱和经典变量提取方法SPA,MC-UVE,GA和GA-SPA方法进行比较。以200个库尔勒香梨为研究对象,采用SPXY方法将样本划分为校正集和预测集,校正集和预测集分别包含150个和50个样本。基于不同方法筛选的变量,分别建立线性PLS模型及非线性LS-SVM模型,r2,RMSEP和RPD用于模型性能的评估。综合比较发现,GA,GA-SPA和CARS变量筛选方法能够有效地筛选出原始高光谱数据中具有强信息且对外界影响因素不敏感的变量,适用于高光谱数据关键变量的提取,其中CARS变量筛选效果最佳,基于CARS获取的关键变量构建的非线性LS-SVM库尔勒香梨SSC含量预测模型获得了最优的预测结果,r2_pre,RMSEP和RPD分别为0.851 2,0.291 3和2.592 4。研究表明,CARS方法是一种有效的高光谱关键变量筛选方法,利用高光谱数据,非线性LS-SVM模型比线性PLS模型更适合于香梨品质的定量预测。     

旋转对称椭球颗粒沿轴脉冲光声波波形的几何计算

针对旋转对称椭球颗粒脉冲光声波的产生,推导沿其对称轴方向的波形的解析表达式.结果表明,无论是长椭球还是扁椭球颗粒,沿轴波形相对于球形颗粒所产生的N形波都有一定的形变,并且在近场条件下显示出能反映椭球颗粒形状与大小的明显特征.因此通过对脉冲光声波的测量和分析,能对旋转对称椭球颗粒进行形貌判定.     

小鼠卵母细胞染色体三维双光子荧光图像的轴向衰减

双光子荧光显微镜作为一种高分辨光学仪器,已经被广泛应用于生物样品的非侵入式三维光学成像中。相比共聚焦显微镜,双光子荧光显微镜拥有更深的探测深度。然而,即便如此,在对较厚的生物样品进行非侵入式光学三维成像时,样品的成像质量也往往会随着探测深度的增加而下降。在临床和生物学领域对研究母性遗传起重要作用的小鼠卵母细胞拥有较大的直径(80～100 μm),吸收和散射效应较为明显。本文研究小鼠卵母细胞染色体的三维双光子荧光图像随探测深度增加图像质量的衰减程度。通过对所得图像进行轴向衰减矫正,利用体积作为参数,将矫正前后小鼠卵母细胞内染色体三维双光子荧光图像进行对比。结果表明,由于吸收和散射效应,卵母细胞存在较严重的光学轴向衰减问题,因此,对用双光子荧光三维成像手段获得的小鼠卵母细胞图像进行衰减矫正是有必要的。这为进一步精确定量的研究卵母细胞内染色体的三维构像打下良好的基础。     

高成像质量Offner成像光谱仪的理论分析与研制

以双镜系统为基础构建了Offner成像光谱仪,并利用光程函数来获得一种Offner成像光谱仪的初始结构.通过光学设计软件Code V对该初始结构进行了仿真与优化,优化后的光谱仪具有高成像质量,其均方根点列图直径明显降低,调制传递函数曲线在子午像与弧矢像上都获得了好的成像效果.该研究免去了过于复杂的像差推导过程,并在宽光谱400~1 300nm条件下获得了具有高成像质量的Offner光谱仪结构,为光谱仪的搭建提供了理论基础.