First commissioning results of the coherent scattering and imaging endstation at the Shanghai soft X-ray free-electron laser facility

The Shanghai soft X-ray free-electron laser(SXFEL)user facility project started in 2016 and is expected to be open to users by 2022.It aims to deliver ultra-intense coherent femtosecond X-ray pulses to five endstations covering a range of 100–620 eV for ultrafast X-ray science.Two undulator lines are designed and constructed,based on different lasing modes:self-amplified spontaneous emission and echo-enabled harmonic generation.The coherent scattering and imaging(CSI)endstation is the first of five endstations to be commissioned online.It focuses on high-resolution single-shot imaging and the study of ultrafast dynamic processes using coherent forward scattering techniques.Both the single-shot holograms and coherent diffraction patterns were recorded and reconstructed for nanoscale imaging,indicating the excellent coherence and high peak power of the SXFEL and the possibility of‘‘diffraction before destruction’’experiments at the CSI endstation.In this study,we report the first commissioning results of the CSI endstation.

Free form deformation and symmetry constraint‐based multimodal brain image registration using generative adversarial nets

Multi‐modal brain image registration has been widely applied to functional localisation,neurosurgery and computational anatomy.The existing registration methods based on the dense deformation fields involve too many parameters,which is not conducive to the exploration of correct spatial correspondence between the float and reference images.Meanwhile,the unidirectional registration may involve the deformation folding,which will result in the change of topology during registration.To address these issues,this work has presented an unsupervised image registration method using the free form deformation(FFD)and the symmetry constraint‐based generative adversarial networks(FSGAN).The FSGAN utilises the principle component analysis network‐based structural representations of the reference and float images as the inputs and uses the generator to learn the FFD model parameters,thereby producing two deformation fields.Meanwhile,the FSGAN uses two discriminators to decide whether the bilateral registration have been realised simultaneously.Besides,the symmetry constraint is utilised to construct the loss function,thereby avoiding the deformation folding.Experiments on BrainWeb,high grade gliomas,IXI and LPBA40 show that compared with state‐of‐the‐art methods,the FSGAN provides superior performance in terms of visual comparisons and such quantitative indexes as dice value,target registration error and computational efficiency.

Free-breathing radial volumetric interpolated breathhold examination vs breath-hold cartesian volumetric interpolated breath-hold examination magnetic resonance imaging of the liver at 1.5T

AIM: To compare breath-hold cartesian volumetric interpolated breath-hold examination(cVIBE) and freebreathing radial VIBE(rVIBE) and determine whether rVIBE could replace cVIBE in routine liver magnetic resonance imaging(MRI).METHODS: In this prospective study, 15 consecutive patients scheduled for routine MRI of the abdomen underwent pre- and post-contrast breath-hold cVIBE imaging(19 s acquisition time) and free-breathing rVIBE imaging(111 s acquisition time) on a 1.5T Siemens scanner. Three radiologists with 2, 4, and 8 years post-fellowship experience in abdominal imaging evaluated all images. The radiologists were blinded to the sequence types, which were presented in a random order for each patient. For each sequence, the radiologists scored the cVIBE and rVIBE images for liver edge sharpness, hepatic vessel clarity, presence of artifacts, lesion conspicuity, fat saturation, and overall image quality using a five-point scale. RESULTS: Compared to rVIBE, cVIBE yielded significantly(P < 0.001) higher scores for liver edge sharpness(mean score, 3.87 vs 3.37), hepatic-vessel clarity(3.71 vs 3.18), artifacts(3.74 vs 3.06), lesion conspicuity(3.81 vs 3.2), and overall image quality(3.91 vs 3.24). cVIBE and rVIBE did not significantly differ in quality of fat saturation(4.12 vs 4.03, P = 0.17). The inter-observer variability with respect to differences between rVIBE and cVIBE scores was close to zero compared to random error and inter-patient variation. Quality of rVIBE images was rated as acceptable for all parameters. CONCLUSION: rVIBE cannot replace cVIBE in routine liver MRI. At 1.5T, free-breathing rVIBE yields acceptable, although slightly inferior image quality compared to breath-hold cVIBE.

Image quality and diagnostic performance of free-breathing diffusion-weighted imaging for hepatocellular carcinoma

AIM To retrospectively evaluate the diagnostic performance of free-breathing diffusion-weighted imaging(FB-DWI) with modified imaging parameter settings for detecting hepatocellular carcinomas(HCCs).METHODS Fifty-one patients at risk for HCC were scanned with both FB-DWI and respiratory-triggered DWI with the navigator echo respiratory-triggering technique(RTDWI).Qualitatively,the sharpness of the liver contour,the image noise and the chemical shift artifacts on each DWI with b-values of 1000 s/mm2 were independently evaluated by three radiologists using 4-point scoring.Wecompared the image quality scores of each observer between the two DWI methods,using the Wilcoxon signed-rank test.Quantitatively,we compared the signal-to-noise ratios(SNRs) of the liver parenchyma and lesion-to-nonlesion contrast-to-noise ratios(CNRs) after measuring the signal intensity on each DWI with a b-factor of 1000 s/mm2.The average SNRs and CNRs between the two DWI methods were compared by the paired t-test.The detectability of HCC on each DWI was also analyzed by three radiologists.The detectability provided by the two DWI methods was compared using Mc Nemar's test.RESULTS For all observers,the averaged image quality scores of FB-DWI were:Sharpness of the liver contour [observer(Obs)-1,3.08 ± 0.81;Obs-2,2.98 ± 0.73;Obs-3,3.54 ± 0.75],those of the distortion(Obs-1,2.94 ± 0.50;Obs-2,2.71 ± 0.70;Obs-3,3.27 ± 0.53),and the chemical shift artifacts(Obs-1,3.38 ± 0.60;Obs-2,3.15 ± 1.07;Obs-3,3.21 ± 0.85).The averaged image quality scores of RTDWI were:Sharpness of the liver contour(Obs-1,2.33 ± 0.65;Obs-2,2.37 ± 0.74;Obs-3,2.75 ± 0.81),distortion(Obs-1,2.81 ± 0.56;Obs-2,2.25 ± 0.74;Obs-3,2.96 ± 0.71),and the chemical shift artifacts(Obs-1,2.92 ± 0.59;Obs-2,2.21 ± 0.85;Obs-3,2.77 ± 1.08).All image quality scores of FB-DWI were significantly higher than those of RT-DWI(P < 0.05).The average SNR of the normal liver parenchyma by FB-DWI(11.0 ± 4.8) was not significantly different from that shown by RT-DWI(11.0 ± 5.0);nor were the lesion-to-nonlesion CNRs significantly different(FB-DWI,21.4 ± 17.7;RT-DWI,20.1 ± 15.1).For all three observers,the detectability of FB-DWI(Obs-1,43.6%;Obs-2,53.6%;and Obs-3,45.0%) was significantly higher than that of RT-DWI(Obs-1,29.1%;Obs-2,43.6%;and Obs-3,34.5%)(P < 0.05).CONCLUSION FB-DWI showed better image quality and higher detectability of HCC compared to RT-DWI,without significantly reducing the SNRs of the liver parenchyma and lesionto-nonlesion CNRs.

Wide/narrow azimuth acquisition footprints and their effects on seismic imaging

Acquisition footprint is a new concept to describe the seismic noise in three-dimensional seismic exploration and it is closely related to geometry and observation shuttering. At present, the study on acquisition footprints has become a hot spot. In partnership with the Dagang Oilfield, we used the channel sand body seismic physical model to study the characteristics of wide/narrow azimuth acquisition footprints and analyzed and compared the two types of footprints and their effects on target imaging. In addition, the footprints caused by data processing of the normal moveout offset （NMO） stretching aberration were discussed. These footprints are located only in the shallow or middle layer in the time slice, and possibly affect the imaging of shallow target layers, and have no influence on deep target imaging. Seismic physical modeling has its advantages in the study of acquisition footprints.

Visual and optical performance of eyes with different corneal spherical aberration implanted with aspheric intraocular lens

AIM: To compare the visual and optical performance of eyes with different corneal spherical aberration (SA) implanted with spherical aberration-free intraocular lens (IOLs). METHODS: Thirty-six patients with different corneal SA had phacoemulsification with implantation of spherical aberration-free IOLs. Patients were divided into 3 groups according to the value of preoperative corneal SA. Eyes with corneal SA <0.10 mu m were assigned to group A, those with 0.10 <= corneal SA <0.20 mu m to Group B, and those with 0.20 <= corneal SA <0.35 mu m to Group C. Best-corrected visual acuity (BCVA), contrast sensitivity, corneal SA, total ocular aberrations, and depth of focus were recorded 3 months postoperatively. Distance-corrected near and intermediate visual acuity was studied to measure depth of focus. RESULTS: BCVA and contrast sensitivity were similar between groups. There were no significant differences in distance-corrected near or intermediate visual acuity. Corneal SA was similar before and 3 months after surgery in the 3 groups. With a 5.0mm pupil diameter, root mean square values for total ocular higher-order aberrations (HOAs) were lower in groups A and B than in group C. Total ocular SA was lower in group A than in groups B and C. SA was also lower in group B than in group C. Coma and trefoil were similar between the groups. CONCLUSION: Implantation of spherical aberration-free IOLs in eyes with different corneal SA results in similar visual performance at BCVA, contrast sensitivity and depth of focus.

Advanced diffusion magnetic resonance imaging in patients with Alzheimer’s and Parkinson’s diseases

The prevalence of neurodegenerative diseases is increasing as human longevity increases. The objective biomarkers that enable the staging and early diagnosis of neurodegenerative diseases are eagerly anticipated. It has recently become possible to determine pathological changes in the brain without autopsy with the advancement of diffusion magnetic resonance imaging techniques. Diffusion magnetic resonance imaging is a robust tool used to evaluate brain microstructural complexity and integrity, axonal order, density, and myelination via the micron-scale displacement of water molecules diffusing in tissues. Diffusion tensor imaging, a type of diffusion magnetic resonance imaging technique is widely utilized in clinical and research settings;however, it has several limitations. To overcome these limitations, cutting-edge diffusion magnetic resonance imaging techniques, such as diffusional kurtosis imaging, neurite orientation dispersion and density imaging, and free water imaging, have been recently proposed and applied to evaluate the pathology of neurodegenerative diseases. This review focused on the main applications, findings, and future directions of advanced diffusion magnetic resonance imaging techniques in patients with Alzheimer's and Parkinson's diseases, the first and second most common neurodegenerative diseases, respectively.

SOFT IMAGE SEGMENTATION BASED ON CENTER-FREE FUZZY CLUSTERING

Image segmentation remains one of the major challenges in image analysis.And soft image segmentation has been widely used due to its good effect.Fuzzy clustering algorithms are very popular in soft segmentation.A new soft image segmentation method based on center-free fuzzy clustering is proposed.The center-free fuzzy clustering is the modified version of the classical fuzzy C-means ( FCM ) clustering.Different from traditional fuzzy clustering , the center-free fuzzy clustering does not need to calculate the cluster center , so it can be applied to pairwise relational data.In the proposed method , the mean-shift method is chosen for initial segmentation firstly , then the center-free clustering is used to merge regions and the final segmented images are obtained at last.Experimental results show that the proposed method is better than other image segmentation methods based on traditional clustering.

Distortion-Free Data Embedding Scheme for High Dynamic Range Images

Distortion-free data embedding is a technique which can assure that not only the secret data is correctly extracted but also the cover media is recovered without any distortion after secret data is extracted completely. Because of these advantages, this technique attracts the attention of many researchers. In this paper, a new distortion-free data embedding scheme for high dynamic range （HDR） images is proposed. By depending on Cartesian product, this scheme can obtain higher embedding capacity while maintaining the exactly identical cover image and stego image when using the tone mapping algorithms. In experimental results, the proposed scheme is superior to Yu et aL＇s scheme in regard to the embedding rate——an average embedding rate of 0.1355 bpp compared with Yn et aL＇s scheme （0.1270 bpp）.

Statistical analysis of ocular monochromatic aberrations in Chinese population for adaptive optics ophthalmoscope design

It is necessary to know the distribution of the Chinese eye's aberrations in clinical environment to guide high-resolution retinal imaging system design for large Chinese population application.We collected the monochromatic wave aberration of 332 healthy eyes and 344 diseased eyes in Chinese population across a 6.0-mm pupil.The aberration statistics of Chinese eyes including healthy eyes and diseased eyes were analyzed,and some differences of aberrations between the Chinese and European race were concluded.On this basis,the requirement for adaptive optics(AO)correction of the Chinese eye's monochromatic aberrations was analyzed.The result showed that a stroke of 20μm and ability to correct aberrations up to the 8th Zernike order were needed for reflective wavefront correctors to achieve near difraction-limited imaging in both groups for a reference wavelength of 550 nm and a pupil diameter of 6.0mm.To verify the:analysis mentioned above,an A0 floodillumination system was established,and high-resolution retinal imaging in vivo was achieved for Chinese eye including both healthy and diseased eyes.

Multi-modality liver image registration based on multilevel B-splines free-form deformation and L-BFGS optimal algorithm

A new coarse-to-fine strategy was proposed for nonrigid registration of computed tomography(CT) and magnetic resonance(MR) images of a liver.This hierarchical framework consisted of an affine transformation and a B-splines free-form deformation(FFD).The affine transformation performed a rough registration targeting the mismatch between the CT and MR images.The B-splines FFD transformation performed a finer registration by correcting local motion deformation.In the registration algorithm,the normalized mutual information(NMI) was used as similarity measure,and the limited memory Broyden-Fletcher- Goldfarb-Shannon(L-BFGS) optimization method was applied for optimization process.The algorithm was applied to the fully automated registration of liver CT and MR images in three subjects.The results demonstrate that the proposed method not only significantly improves the registration accuracy but also reduces the running time,which is effective and efficient for nonrigid registration.

Semi-reference image quality metric for virtual view images in free-viewpoint television

A semi-reference image quality assessment metric based on similarity measurement for synthesizedvirtual viewpoint image (WI) in free-viewpoint television system (FTV) is proposed in this paper. Thekey point of the proposed metric is taking resemblant information between WI and its neighbor view imagesfor quality assessment to make our metric to be extended to multi-semi-reference image quality assessmenteasily. The proposed metric first extracts impact factors from image features, then combines animage synthesis technique and similarity functions, in which, disparity information are taken into accountfor registering the resemblant regions. Experiments are divided into three phases. Phase Ⅰ is to verify thevalidation of the proposed metric by taking impaired images and original reference into account. The experimentalresults show the agreement between evaluation scores and bio-characteristic of human visualsystem. Phase Ⅱ shows the accordance with Phase Ⅰ by taking neighbor view as reference. The proposedmetric can be taken as a full reference one to evaluate the image quality even though the original referenceis absent. Phase Ⅲ is then performed to evaluate the quality of ⅤⅥ. Evaluation scores in the experimentalresults are able to evaluate the quality of ⅤⅥ.

Optimization of Image Quality in Retrospective Respiratory-Gated Micro-CT for Quantitative Measurements of Lung Function in Free-Breathing Rats

Objective: To optimize scan time and X-ray dose with no loss of image quality for retrospectively gated micro-CT scans of free-breathing rats. Methods: Five free-breathing rats were scanned using a dynamic micro-CT scanner over 10 continuous gantry rotations (50 seconds and entrance dose of 0.28 Gy). The in-phase projection views were selected and reconstructed, representing peak inspiration and end expiration from all 10 rotations and progressively fewer rotations. A least error method was also used to ensure that all angular positions were filled. Image quality and reproducibility for physiological measurements were compared for the two techniques. Results: The least error approach underestimated the lung volume, air content in the lung at peak inspiration, and tidal volume. Other measurements showed no differences between the projection-sorting techniques. Conclusions: Seven gantry rotations (35 seconds and 0.2 Gy dose) proved to be the optimal protocol for both the in-phase images and the least error images.

3D自由呼吸starVIBE序列在颈部MRI增强中的应用研究

探讨3D自由呼吸starVIBE技术在颈部MRI增强扫描中的应用价值。前瞻性收集2022年4月至2023年3月首都医科大学附属北京同仁医院行颈部增强MRI检查的41例患者,使用3.0T MR扫描仪与16通道头颈联合线圈对其进行3D自由呼吸starVIBE增强和Dixon脂肪抑制TSE增强T1加权成像,评价2组图像的图像质量,客观评价为计算测量组织中淋巴结、对应层面竖脊肌的信号强度值及背景噪声,计算图像的信噪比(SNR)和对比度噪声比(CNR);主观评价为主观评分,指标包括脂肪抑制程度、黏膜增强、肌肉边缘清晰度、血管清晰度、病变边缘清晰度、病变清晰度、呼吸吞咽运动伪影、血管搏动伪影和图像质量总体评分(整体图像质量)。采用独立样本t检验或Wilcoxon秩和检验比较2组图像间客观指标和主观评分的差异。结果显示,TSE_T1WI-Dixon组淋巴结的SNR高于3D-starVIBE组,差异有统计学意义(P<0.001),3D-starVIBE组肌肉的SNR与TSE_T1WI-Dixon组差异无统计学意义(P=0.341>0.05),TSE_T1WI-Dixon组的CNR高于3D-starVIBE组,差异有统计学意义(P<0.001);3D-starVIBE组与TSE_T1WI-Dixon组的图像在脂肪抑制程度、黏膜增强、病变清晰度的评分差异无统计学意义(P均>0.05),3D-starVIBE组的图像在肌肉边缘清晰度、血管清晰度、病变边缘清晰度、呼吸吞咽运动伪影、血管搏动伪影和图像质量总体评分高于TSE_T1WI-Dixon组,差异有统计学意义(P均<0.001)。两名观察者对两组图像评分的一致性较强,加权Kappa系数为0.616~0.863(P均<0.001)。使用3D自由呼吸starVIBE增强序列可以减少颈部呼吸吞咽运动伪影和血管搏动伪影,提高颈部软组织清晰度的显示能力,可在临床实践中作为补充或替代使用。

改进YOLOv5s对病理学图像中猪只小肠绒毛的检测

为解决传统小肠绒毛需要专业人员手动检测耗时耗力且存在主观性和不稳定性等问题,同时提高在复杂病理学图像中小肠绒毛检测的准确率和效率,该研究提出基于改进YOLOv5s检测复杂病理学图像下猪只小肠绒毛的方法。首先,采用串联形式的混合池化对空间金字塔进行优化,增强特征提取与特征表达,提升检测精度;然后引入一种基于注意力机制的网络模块(simpleattentionmechanism,SimAM)与Bottleneck中的残差连接相结合,使用SimAM对Bottleneck中的特征图进行加权,得到加权后的特征表示,利用注意力机制加强模型对目标的感知。试验结果表明,该研究算法的平均精度(average precision)和每秒传输帧数(frame per second,FPS)达到92.43%和40帧/s。改进后的YOLOv5s在召回率和平均精度上相较改进前提高2.49和4.62个百分点,在不增加模型参数量的情况下,每帧图片的推理时间缩短1.04 ms。与经典的目标检测算法SSD、Faster R-CNN、YOLOv6s、YOLOX相比,平均精度分别提高15.16、10.56、2.03和4.07个百分点。结果表明,该方法能够实现病理学图像中猪只小肠绒毛自动化检测,保证复杂图像检测速度的同时,提高了小肠绒毛的检测精度。

基于无人机PPK技术在免像控条件下山区光伏地形图的生产

针对光伏场区高差大、部分区域植被覆盖、通信信号弱的特点,本文提出了一种基于动态后处理技术(PPK)在免像控条件下航测光伏地形图生产的方法。该方法首先在免像控的条件下对航测获取的无人机影像定位测姿系统(POS)数据和点云数据进行PPK解算;然后利用点云后处理、影像空中三角测量、数字微分纠正等技术生成高精度数字高程模型(DEM)和数字正射影像(DOM)成果;最后利用DEM和DOM成果构建三维模型,实现地形图生产。利用两个典型应用实例,验证了该方法可完全满足光伏地形图的精度要求。

MRI功能成像联合血清学对鉴别前列腺病变性质的临床意义

目的探讨MRI功能成像联合血清学对鉴别前列腺病变性质的临床意义。方法回顾性选取2021年7月至2023年7月延安市人民医院收治的疑似前列腺癌(PCa)患者120例,均为男性,均行3.0T MRI常规扫描、弥散加权成像(DWI)扫描、磁共振波谱(MRS)成像扫描及病理检查。根据病理结果,将患者分为PCa组(53例)及良性组(67例)。PCa组年龄(63.19±4.72)岁,良性组年龄(61.75±4.54)岁。比较两组血清游离前列腺特异性抗原(fPSA)水平、总前列腺特异性抗原(tPSA)水平、MRI功能成像结果、病理结果及不同检查方式的诊断效能。采用独立样本t检验和χ^(2)检验。结果PCa组血清fPSA、tPSA水平均高于良性组(均P<0.05);MRI常规扫描诊断灵敏度为69.81%(37/53)、特异度为83.58%(56/67)、准确率为77.50%(93/120),DWI诊断灵敏度为75.47%(40/53)、特异度为88.06%(59/67)、准确率为82.50%(99/120),MRS诊断灵敏度为73.58%(39/53)、特异度为86.57%(58/67)、准确率为80.83%(97/120),血清学诊断灵敏度为71.70%(38/53)、特异度为86.57%(58/67)、准确率为80.00%(96/120),联合诊断灵敏度为94.34%(50/53)、特异度为83.58%(56/67)、准确率为88.33%(106/120);联合诊断灵敏度、阳性预测值均高于MRI功能成像、血清学单独应用,漏诊率低于MRI功能成像、血清学单独应用(均P<0.05)。结论MRI功能成像联合血清学对PCa具有一定诊断价值,可作为临床鉴别前列腺病变性质的有效检查方式。

基于谱分析的红外成像模糊去除算法研究

针对红外成像中出现的像差和运动模糊问题,提出了一种基于谱分析的红外成像模糊去除算法。该方法通过对模糊问题的分析,利用红外图像频谱信息构建了模糊函数估计方法,通过数据拟合项和正则项的优化,实现红外图像的模糊去除。实验在运动模糊图像数据集和静态像差图像上进行测试,结果表明:在数据集模糊去除实验上,相比之前的方法,本文方法峰值信噪比(PSNR,peak signal-to-noise ratio)提升了2.01 dB,结果相似性(SSIM,structural similarity index)提升了0.06;静态像差图像在实验室条件下通过短波红外探测器采集,算法在主观上有较明显的复原效果,且针对高通量光学系统成像复原效果更为显著。