Score Evaluation of MRI Sequence Type Related Artifacts after Interbody Fusion with Metallic Implants—A Spine Specimen Study

Introduction: According to anterior spine fusion intervertebral disc spacers made of titanium or cobalt-chromium al-loys are of special interest. With regard to postoperative problems implant related artifacts can lead to a decreased MRI evaluation. The focus of this study was to compare the respective implant artifact artifact range dependend on different MRI sequences. To simplify artifact evaluation we introduced in this study a new developed 0-1-2 score. Material and Methods: We performed an MRI artifact evaluation of 2 different metallic intervertebral disc spacers (cobalt-chromium and titanium alloy). A carcass porcine spine was employed. Considering 12 defined spinal regions of interest we evaluated the respective implant artifact properties independent from the total artifact volume by using a new developed 0-1-2 score. The artifact range was documented for 15 different MRI-sequences. Results: For the titanium spacer as well as the cobalt-chromium-spacer an MRI evaluation of the implant/disc space situation could not be carried out. In contrast to the cobalt chromium spacer the titanium spacer allowed a good differentiation of the spinal canal opposite to the implant. Optimal MRI imaging results for both metallic intervertebral disc spacers could be achieved considering TSE sequences. Conclusion: A comparison of these two metallic spacers showed in all examined sequences clear advantages in favour of the titanium spacer. The best MRI representation of both tested implants by reducing implant related artifacts could be achieved with fast spin echo (TSE-) sequences. In spite of the use of TSE sequences a variability of susceptibility artifacts has to be included with regard to implant shape and material. With regard to the results of this study the easy use of a new developed artifact score represented a useful help to compare implant related MRI artifact properties independent from the actual implant related total artifact volume.

Score based assessment of implant-related post fusion MRI artifacts focused on different interbody disc spacers: An <i>in vitro</i>study

Interbody disc spacers for anterior spine fusion are made of different materials, such as titanium alloys or carbon fiber reinforced polymers (CFRP). Implant-related susceptibility artifacts can decrease the quality of MRI scans. This cadaveric study aimed to demonstrate the extent that implant-related MRI artifacting affects the post fusion differentiation of the spinal canal (SC) and intervertebral disc space (IDS). In 6 cadaveric porcine spines, we evaluated the post-im- plantation MRI scans of a titanium and CFRP spacer that differed in shape and surface qualities. A spacer made of human cortical bone was used as a control. A defined evaluation unit was divided into regions of interest (ROI) to characterize the SC and IDS. Considering 15 different MRI sequences read independently by an interobserver-validated team of specialists artifact-affected image quality of the median MRI slice was rated on a modified score of 0-1-2-3. A maximum score of 15 points for the SC and 9 points for the IDS (100%) was possible. Turbo spin echo sequences produced the best scores for both spacers and the control. Only the control achieved a score of 100%. For the IDS the titanium and CFRP spacer maximally scored 0% and 74%, for the SC 80% and 99%, respectively. By using favored T1 TSE sequences the CFRP-spacer represented clear advantages in post fusion spinal imaging. Independent of artifact dimensions the used scoring system allowed us to create an implant-related ranking of MRI scan quality in reference to the bone control.

双延迟3D-ASL评估单侧大脑中动脉闭塞患者侧支循环的预后价值

目的探讨双延迟三维动脉自旋标记(3D ASL)在评估单侧大脑中动脉(MCA)闭塞患者侧支循环状态及临床转归中的应用价值。方法回顾性分析2019年1月至2021年12月经MRA证实的单侧MCA闭塞的患者134例,所有患者治疗前行T2-FLAIR、DWI、MRA及双延迟3D-ASL检查,入院当日和入院15日美国国立卫生研究院卒中量表(NIHSS)评分完整。测量患侧及镜像侧脑血流量(CBF)值,并计算相对脑血流量(rCBF)(rCBF=患侧CBF/健侧CBF);依据CBF伪彩图梗死核心周围低灌注区皮层及皮层下是否出现动脉穿行伪影(ATA)征象,将患者分为ATA(+)组和ATA(-)组;依据T2-FLAIR序列中高信号血管征(HVS),对所有患者进行侧支循环等级分组。结果(1)ATA(-)组28例,ATA(+)组106例,两组患者在侧支循环等级分组、PLD=1.5s rCBF值、入院15dNIHSS评分及入院15d NIHSS评分降度差异均有统计学意义(P<0.001),其中ATA(+)组PLD=1.5s rCBF明显低于ATA(-)组、入院15d NIHSS评分降度明显高于ATA(-)组;(2)侧支循环等级分组:0级28例,1级25例,2级33例,3级48例,各组间PLD=1.5s rCBF、入院15d NIHSS评分及入院15dNIHSS评分降度差异均有统计学意义(P<0.001),侧支循环等级越高,rCBF(PLD=1.5s)越低、入院15d NIHSS评分降度越大;(3)侧支循环评分与入院15d NIHSS评分降度呈明显正相关(t=10.241,B=0.096,95%CI 0.077~0.114,P<0.001)。结论双延迟3D-ASL可以无创、直观地判断单侧大脑中动脉闭塞患者是否存在侧支循环,与T2-FLAIR联合可进一步评估侧支循环的状态,为临床评价预后提供客观依据。

基于图像结构的无参考模糊图像及其复原图像质量评价方法

针对传统图像的质量评价测度,提出了一种基于边缘检测的无参考模糊图像评价模型。通过测量梯度图像的梯度边缘信息,来评价模糊退化图像和带有模糊效应的复原图像,实验表明:利用本测度所得到的模糊图像质量评价结果与主观评价结果有很好的相关性。本测度较准确地反映了人对模糊图像质量的主观感受,对于带有模糊效应的复原图像的评价结果也较为符合主观评价结果。

回归分析最小化睡眠信号中的ECG干扰

简要介绍了回归分析的方法 ,并将其应用于睡眠EEG自动分期研究中 ,用于抑制所采集的各通道信号中的ECG干扰。实验结果表明 :回归分析方法可以极大地消除各通道信号中的ECG干扰 。

基于块效应的JPEG图像无参考质量评价

根据JPEG压缩图像产生的块效应,提出了一种简单的JPEG图像无参考质量评价方法。首先找出JPEG图像相邻失真块的边界位置,然后计算相邻块边界像素灰度差值的平方,同时累计边界像素的个数,最后利用简单的公式直接得到JPEG图像无参考质量评价值。对LIVE和TID2008数据库中.JPEG图像进行了实验,客观值与主观评价间的线性相关系数分别达到0.924 4和0.937 3。实验结果表明:该方法对不同的图像有良好的适应性。

古籍高精复制方法探究——以明代刻本《对音捷要琴谱》的复制实践为例

《对音捷要琴谱》是明代杨表正所写的一本琴谱,他大胆创作提出了“正文对音”原则。琴谱作为纸质文物真实地记录了人类的历史和文化,是研究社会发展的重要史料,展览是传承古籍价值最有效的途径,但是因为文物的珍贵性不宜长久陈设,故对其进行复制。文中着重对文物复制过程中色彩管理技术的实施进行了介绍,在文物影像后期处理方面根据所要复制的内容确定了多次锐化的策略从而有效突出了想要强化的细节纹理。并尝试在Lab色彩模式下对文物影像进行调色。在打印输出过程中使用色彩管理软件对输出结果进行了预测。整套工作流程具有较高的可靠性,具备一定的实用价值。

长程视频脑电图监测期间患者舒适水平对监测效果的相关性研究

目的 观察长程视频脑电图（VEEG）监测期间患者舒适水平对监测效果的影响.方法 观察168例发作性疾病患者行VEEG监测前后舒适度评分及脑电图伪差的发生情况,采用Pearson相关分析舒适度评分与伪差的相关性.结果 VEEG前患者生理舒适、精神心理舒适、社会舒适、环境舒适及整体舒适度5项的平均单项目得分分别为（2.87±1.04）、（2.63±0.98）、（2.40±1.25）、（2.84±0.90）、（2.69±1.07）分,实施VEEG后患者生理舒适、精神心理舒适、社会舒适、环境舒适及整体舒适度5项的平均单项目得分分别为（2.06±1.38）、（1.66±1.40）、（1.89±0.57）、（1.83±1.24）、（1.86±1.19）分,2组比较差异有统计学意义（t=4.011-6.353,均P〈0.05）.整体舒适度平均单项目得分与眨眼或眼球运动伪差、身体活动伪差、咀嚼或吞咽伪差和肌电图伪差呈显著负相关（r=-0.843--0.585,均P〈0.05）,即整体舒适度提高会降低上述伪差出现的次数;整体舒适度平均单项目得分与出汗及皮肤电伪差、心电图伪差的发生无相关性（r=-0.204、-0.158,均P〉0.05）.结论长程VEEG监测期间,患者舒适度评分与伪差发生次数有显著负相关,监测前进行舒适度评估,提供舒适护理,对提高长程VEEG的监测准确性有重要意义.

一种基于无参考的块效应评价方法

针对基于离散余弦变换(DCT)变换的图像压缩后失真图像易产生块效应,提出了一种有效的块效应评价方法。首先依据JPEG图像每8×8图像块的灰度值特性把其失真程度分为严重、较严重、有轻微方块化效应和无方块化4类,统计每类图像块占整幅图像的比例,然后确立每类图像块与图像质量平均主观得分(MOS)之间的关系,利用统计的Regress方法建立JPEG图像块效应评价模型。通过对公用图像数据库LIVE中JPEG图像进行实验,结果表明,该方法简单实用,与MOS具有较高的相关性。