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.     

Generalized total variation-based MRI Rician denoising model with spatially adaptive regularization parameters

Magnetic resonance imaging (MRI) is an outstanding medical imaging modality but the quality often suffers from noise pollution during image acquisition and transmission. The purpose of this study is to enhance image quality using feature-preserving denoising method. In current literature, most existing MRI denoising methods did not simultaneously take the global image prior and local image features into account. The denoising method proposed in this paper is implemented based on an assumption of spatially varying Rician noise map. A two-step wavelet-domain estimation method is developed to extract the noise map. Following a Bayesian modeling approach, a generalized total variation-based MRI denoising model is proposed based on global hyper-Laplacian prior and Rician noise assumption. The proposed model has the properties of backward diffusion in local normal directions and forward diffusion in local tangent directions. To further improve the denoising performance, a local variance estimator-based method is introduced to calculate the spatially adaptive regularization parameters related to local image features and spatially varying noise map. The main benefit of the proposed method is that it takes full advantage of the global MR image prior and local image features. Numerous experiments have been conducted on both synthetic and real MR data sets to compare our proposed model with some state-of-the-art denoising methods. The experimental results have demonstrated the superior performance of our proposed model in terms of quantitative and qualitative image quality evaluations.     

Semi-adiabatic Shinnar–Le Roux pulses and their application to diffusion tensor imaging of humans at 7T

The adiabatic Shinnar–Le Roux (SLR) algorithm for radiofrequency (RF) pulse design enables systematic control of pulse parameters such as bandwidth, RF energy distribution and duration. Some applications, such as diffusion-weighted imaging (DWI) at high magnetic fields, would benefit from RF pulses that can provide greater B₁ insensitivity while adhering to echo time and specific absorption rate (SAR) limits. In this study, the adiabatic SLR algorithm was employed to generate 6-ms and 4-ms 180° semi-adiabatic RF pulses which were used to replace the refocusing pulses in a twice-refocused spin echo (TRSE) diffusion-weighted echo planar imaging (DW-EPI) sequence to create two versions of a twice-refocused adiabatic spin echo (TRASE) sequence. The two versions were designed for different trade-offs between adiabaticity and echo time. Since a pair of identical refocusing pulses is applied, the quadratic phase imposed by the first is unwound by the second, preserving the linear phase created by the excitation pulse. In vivo images of the human brain obtained at 7 Testa (7 T) demonstrate that both versions of the TRASE sequence developed in this study achieve more homogeneous signal in the diffusion-weighted images than the conventional TRSE sequence. Semi-adiabatic SLR pulses offer a more B₁-insensitive solution for diffusion preparation at 7 T, while operating within SAR constraints. This method may be coupled with any EPI readout trajectory and parallel imaging scheme to provide more uniform coverage for diffusion tensor imaging at 7 T and 3 T.     

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.     

Three‐dimensional coherent diffractive imaging on non‐periodic specimens at the ESRF beamline ID10

The progress of tomographic coherent diffractive imaging with hard X‐rays at the ID10 beamline of the European Synchrotron Radiation Facility is presented. The performance of the instrument is demonstrated by imaging a cluster of Fe₂P magnetic nanorods at 59 nm 3D resolution by phasing a diffraction volume measured at 8 keV photon energy. The result obtained shows progress in three‐dimensional imaging of non‐crystalline samples in air with hard X‐rays.     

Tracking extended mucociliary transport activity of individual deposited particles: longitudinal synchrotron X‐ray imaging in live mice

To assess potential therapies for respiratory diseases in which mucociliary transit (MCT) is impaired, such as cystic fibrosis and primary ciliary dyskinesia, a novel and non‐invasive MCT quantification method has been developed in which the transit rate and behaviour of individual micrometre‐sized deposited particles are measured in live mice using synchrotron phase‐contrast X‐ray imaging. Particle clearance by MCT is known to be a two‐phase process that occurs over a period of minutes to days. Previous studies have assessed MCT in the fast‐clearance phase, ～20 min after marker particle dosing. The aim of this study was to non‐invasively image changes in particle presence and MCT during the slow‐clearance phase, and simultaneously determine whether repeat synchrotron X‐ray imaging of mice was feasible over periods of 3, 9 and 25 h. All mice tolerated the repeat imaging procedure with no adverse effects. Quantitative image analysis revealed that the particle MCT rate and the number of particles present in the airway both decreased with time. This study successfully demonstrated for the first time that longitudinal synchrotron X‐ray imaging studies are possible in live small animals, provided appropriate animal handling techniques are used and care is taken to reduce the delivered radiation dose.     

Assessment of different fixation protocols on the presence of membrane-bound vesicles in Caco-2 cells: A multidimensional view by means of correlative light and 3-D transmission electron microscopy

Herein, we present a comparative analysis of a variety of chemical and physical fixation protocols for the specific visualisation of the membrane-bound vesicles (MBVs) in the Caco-2 colorectal cancer (CRC) cell line. In so doing, we validated the applicability of specific specimen preparation protocols for the preservation and contrasting of membrane-associated vesicles. Next, by employing the best respective chemical (GOT) and physical (SHPF) fixation methods for the application of transmission electron tomography and modelling we were able to characterise MBVs in three-dimensions and at the nanometer scale. In the second part of this study, we employ a correlative light and electron microscopy (CLEM) approach in order to determine which vesicular compartments are implicated in the uptake of FITC-BSA as a model protein drug. In so doing, we provide a solid foundation for future studies investigating chemotherapeutic drug uptake, transport and fate in cancer cell lines.     

Preparation and Characterization of the Fluorescent Carbon Dots Derived from the Lithium‐Intercalated Graphite used for Cell Imaging

Zero‐dimensional fluorescent carbon dots (CDs) that are used as a cell‐imaging reagent are prepared by using a simple and effective route employing lithium‐intercalated graphite from lithium‐ion batteries as a carbon source. Under ultrasonic exfoliation, the interlayer space increases, while the layer distortion and remaining lithium of the lithium‐intercalated graphite are utilized to disrupt the graphitic structure and produce the CD suspension. Subsequently, after concentration and purification, the obtained colloidal CD suspension has a fluorescent yield of up to 1.2% and is therefore comparable to the CDs prepared in previous reports. These CD products are water‐soluble, nanosized (approximately 3.5 nm), and biocompatible and can easily enter into HeLa cells to act as a cell‐imaging reagent without any further functionalization. In addition, these CDs do not impose toxicity against HeLa cells and have high photostability with low photobleaching and demonstrate potential applications for bio‐labeling as well as solution state optoelectronics.     

纵向带状裂隙形貌的逆时偏移超声成像

传统的工业超声成像方法通常只能确定缺陷的位置与横向尺寸,无法获得缺陷的形貌信息.一些特殊的缺陷,如纵向裂纹,是典型的例子.基于多阵元技术,开展了固体介质缺陷逆时偏移超声成像方法的数值与实验研究.针对铝块平底纵裂纹及内部纵裂纹两种传统方法无法有效成像的缺陷,首先开展了单分量逆时偏移成像方法研究,给出了基于数值仿真的逆时偏移成像结果以及基于多阵元超声成像实验系统实验测试的逆时偏移成像结果.进一步开展了基于多分量位移检测与转换横波分离的逆时偏移成像方法研究,并提出了基于新型多分量激光干涉仪进行检测的思路.数值仿真结果证实了多分量逆时偏移图像重建结果可以克服单分量方式的缺点,得到明显优于单分量检测时的图像.     

基于多角度无透镜傅里叶变换数字全息的散斑噪声抑制成像研究

在数字全息成像中,散斑噪声严重影响了再现像的信噪比和成像分辨率,因此为了提高数字全息成像质量,迫切需要抑制再现像的散斑噪声.分析并给出了矩形散射光斑的强度协方差,定量计算了特定实验条件下产生退相关散斑图样的最小角度差.结合透镜的性质设计并搭建了多角度无透镜傅里叶变换数字全息成像系统,利用光纤端面在透镜焦平面的二维机械移动代替传统反射镜的旋转,使照明光束在不改变照明位置和大小的同时,可任意改变光束方向.移动光纤端面使多角度照明满足最小角度差,获取了81幅数字全息图.利用单次快速傅里叶逆变换实现数值再现,对多幅再现像的强度像求平均,实验结果表明散斑对比度降低为单幅再现像的14.6%,使图像信噪比提高了6.9倍.该抑制散斑的多角度数字全息成像方法有效的抑制了散斑噪声,且成像光路结构简单,可操作性强.