Model tags: direct three-dimensional tracking of heart wall motion from tagged magnetic resonance images

Although magnetic resonance tissue tagging is a useful tool for the non-invasive measurement of three-dimensional (3-D) heart wall motion, the clinical utility of current analysis techniques is limited by the prohibitively long time required for image analysis. A method was therefore developed for the reconstruction of 3-D heart wall motion directly from tagged magnetic resonance images, without prior identification of ventricular boundaries or tag stripe locations. The method utilized a finite-element model to describe the shape and motion of the heart. Initially, the model geometry was determined at the time of tag creation by fitting a small number of guide points which were placed interactively on the images. Model tags were then created within the model as material surfaces which defined the location of the magnetic tags. An objective function was derived to measure the degree of match between the model tags and the image stripes. The objective was minimized by allowing the model to deform directly under the influence of the images, utilizing an efficient method for calculating image-derived motion constraints. The model deformation could also be manipulated interactively by guide points. Experiments were performed using clinical images of a normal volunteer, as well as simulated images in which the true motion was specified. The root-mean-squared errors between the known and calculated displacement and strain for the simulated images were similar to those obtained using previous stripe-tracking and model-fitting methods. A significant improvement in analysis time was obtained for the normal volunteer and further improvements may allow the method to be applied in a 'real-time' clinical environment.     

肝脏实性占位磁共振成像定量指标与病灶性质的相关研究

目的:研究病灶?肝脏信号强度比(SIR)、信噪比(SNR)、对比噪声比(CNR)在区分肝脏实质性小占位的性质方面的价值。方法:随机选择经确诊的肝细胞癌、肝转移瘤和肝血管瘤共67例(101个病灶),行前瞻性磁共振成像(0.5T)研究。计算病灶的SIR,SNR,CNR,并进行统计学分析。结果:T1W图像及质子加权像上,三种定量指标对区分肝血管瘤和肝细胞癌、肝转移瘤无价值。T2W图像上,肝转移瘤与肝细胞癌的SIR,SNR,CNR值均显著小于血管瘤的SIR,SNR,CNR值,TE=60ms时SIR,SNR,CNR区分肝血管瘤和肝细胞癌的诊断正确率分别为72%,72%,83%;TE=90ms时诊断正确率分别为74%,80%,84%;TE=120ms时诊断正确率分别为75%,86%,88%。结论:T1W图像及质子加权像上,三种定量指标对区分肝脏实质性占位的性质无明确价值,T2W图像上测得的SIR,SNR,CNR值可用于区分肝血管瘤与肝细胞癌,且TE=120ms时诊断正确率最高。     

功能磁共振在药物依赖与成瘾中的研究进展

传统毒品海洛因的滥用以及新型毒品冰毒的蔓延,给我国带来严重的社会问题。毒品成瘾者戒断后产生心理渴求及复吸是当前戒毒存在的主要问题。近年来随着医学影像学的发展,弥散张量成像和磁共振波谱可以从微观和分子水平揭示药物成瘾的机制,对指导临床戒毒工作具有非常重要的意义。     

氢质子波谱在骨肌系统肿瘤诊断中的临床应用

目的：研究骨肌系统良、恶性肿瘤的1H-MRS特点，探讨1H-MRS用于骨肌系统肿瘤诊断与鉴别诊断的可行性及价值。材料与方法：本组研究共40例，良性肿瘤组12例，恶性肿瘤组28例。均行常规MRI扫描及在体1H-MRS检查。26例肿瘤新鲜手术标本行离体1H-MRS检查。观察良、恶性肿瘤组织及正常肌肉在体1H-MRS表现，并与肿瘤标本离体1H-MRS检查结果对照，在工作站上测量Cho/Cr及Lipid/Cr比值并进行统计学分析。分析36例肿瘤的细胞密度，并与肿瘤组织Cho/Cr值作Pearson相关性分析。结果：恶性肿瘤组织Cho/Cr比值明显高于良性肿瘤，Lipid/Cr比值低于良性肿瘤，差异均具有显著性意义（P<0.01）。离体波谱研究显示，与良性肿瘤组织相比，18例恶性肿瘤组织的Cho、Lac与mI峰都明显升高，而Lip、Glc则明显下降，12例恶性肿瘤Ala、Glu、PC、Gly峰增高。在体波谱Cho峰及Lipid峰变化趋势与离体波谱具有较高的一致性。恶性肿瘤平均细胞密度为150/视野，良性肿瘤平均细胞密度为61/视野，两者差异具有显著性意义。肿瘤细胞密度与Cho/Cr值呈明显正相关（r=0.882，P<0.001)。结论：良、恶性骨肌系统肿瘤1H-MRS表现明显不同，在体与离体1H-MRS具有较高的一致性，在体1H-MRS对骨肌系统肿瘤的诊断与鉴别诊断具有较高价值。     

应用磁共振体素内不相干运动成像评价大鼠肝纤维化

目的探讨磁共振体素内不相干运动(intravoxel incoherent motion,IVIM)评价大鼠肝纤维化的诊断及分期价值。材料与方法选取SPF级SD大鼠随机分实验组55只和对照组11只,实验组注射CCL4建立肝纤维化模型。第2～12周任意取实验组5只与对照组1只行MR扫描,测量扩散加权成像(diffusion weighted imaging,DWI)、IVIM参数值后同期行METAVIR分期病理检查。用SPSS 22.0分析DWI、IVIM参数值与肝纤维化分期的相关性、诊断及分期价值。结果 (1)实验组在建模期间4只死亡,6只扫描图像质量不佳被排除,共纳入45只实验鼠病理结果:F1～4分别为8、13、14、10只,对照组11只为F0。(2)实验组较对照组ADC、D*、f明显降低且差异具有统计学意义(P<0.01)。ADC、D、f、D*值随肝纤维化进展下降,且Spearman分析示ADC、D、f和D*与肝纤维化水平呈负相关(P<0.05)。(3) F3和F4的ADC、F0和F1的D*、F1和F2的D*和f、F3和F4的D差异有统计学意义(P<0.05)。受试者工作特征(receiver operating characteristic,ROC)曲线示D*鉴别F0和F1～F4、F0～F1和F2～F4及F0～F2和F3～F4效能优于ADC、D和f;ADC鉴别F0～F3和F4效能最高。结论 D*鉴别F0～F3效能最高,ADC鉴别F0～F3和F4效能最高。D*、ADC具肝纤维化分期应用价值。     

2020年心脏MR研究进展

MRI因具有可多平面、多参数及多序列成像且无创、无辐射的优势而成为心血管疾病的重要影像学检查方法。近年来,随着MR硬件与软件的发展,心脏磁共振（CMR）已逐渐成为集诊断与鉴别、判断预后与危险分层等于一体的综合性评估手段,为临床决策所不可或缺。本文对2020年CMR领域的代表性成果进行综述。     

Segmentation of brain tissue from magnetic resonance images

Segmentation of medical imagery is a challenging problem due to the complexity of the images, as well as to the absence of models of the anatomy that fully capture the possible deformations in each structure. The brain is a particularly complex structure, and its segmentation is an important step for many problems, including studies in temporal change detection of morphology, and 3-D visualizations for surgical planning. We present a method for segmentation of brain tissue from magnetic resonance images that is a combination of three existing techniques from the computer vision literature: expectation/maximization segmentation, binary mathematical morphology, and active contour models. Each of these techniques has been customized for the problem of brain tissue segmentation such that the resultant method is more robust than its components. Finally, we present the results of a parallel implementation of this method on IBM's supercomputer Power Visualization System for a database of 20 brain scans each with 256 × 256 × 124 voxels and validate those results against segmentations generated by neuroanatomy experts.     

脑活动功能磁共振成像研究进展

本文介绍了人脑活动功能磁共振成像(fMRI)的生物物理基础研究的现状和关键技术的进展,综述了这些技术在人脑功能研究和临床疾病诊疗中的应用和发展前景.     

Nicotinic acid treatment for Paralepistopsis acromelalga intoxication: assessment using magnetic resonance imaging

Context: Paralepistopsis acromelalga, formerly known as Clitocybe acromelalga, is a rare poisonous mushroom. The mycotoxins in this mushroom cause symptoms resembling those of erythromelalgia; however, its pathogenesis remains unclear. In this report, a patient who received nicotinic acid treatment for P. acromelalga poisoning and radiological evaluation for erythromelalgia has been presented.

Case detail: A 59-year-old woman was hospitalized for redness, swelling, and burning pain in her extremities that rendered difficulty in walking, and a diagnosis of P. acromelalga poisoning was made by detailed interview and mushroom identification. She was treated with intravenous nicotinic acid for 17 days followed by oral nicotinic acid amide for 2 months. She exhibited rapid symptomatic improvement and walked independently after 11 days of initial treatment. Initial MRI of her feet revealed toe-dominated subcutaneous thickening. After nicotinic acid treatment, those radiological findings improved dramatically.

Discussion: The subcutaneous thickening evident on MRI indicated P. acromelalga poisoning-induced erythromelalgia involved subcutaneous inflammatory edema. The typical duration of edema without treatment is more than a month. The improvement on MRI after nicotinic acid treatment indicated that the adequate vasodilation induced by nicotinic acid contributed to resolution of the symptoms. Nicotinic acid was associated with the improvement of the edematous changes caused by the P. acromelalga intoxication.     

可变形图像配准的CT与MRI对肝癌体积测定的前瞻性比较

目的  通过比较MRI与CT对肝癌肿瘤的诊断情况,进而进行高精度放疗计划。方法  选择2020年7月~2022年7月收治的26例不可切除的肝转移(n=8)、肝细胞癌(n=10)和胆管癌(n=8)患者作为研究对象,患者在放疗计划时进行了具有诊断质量的MRI扫描和三期CT扫描,并确定了肝内解剖参考点。在最能显示肿瘤的CT和MRI系列中,勾画了肝脏和肿瘤体积,确定了肝内解剖参考点。采用形变配准对CT和MRI的肝脏进行配准。结果  5例肝癌CT病灶数量与MRI有差异,MRI病灶多3例,CT病灶多2例。肝脏变形配准后,CT肿瘤表面与MRI肿瘤表面平均距离的人群中位数为3.7（2.2~21.3）mm。肿瘤表面积相差5 mm的中位百分比为26%(38%~86%)。转移瘤的中位符合率为81%(77%~86%),肝细胞癌的一致性为78%（44%~86%）,胆管癌的一致性为69%（25%~85%）。结论  MRI诊断的肝癌肿瘤体积与CT诊断的肝癌肿瘤体积存在显著差异,且在原发性肝癌中更为常见。     

DWI多b值水通道蛋白分子成像在肝纤维化早期诊断的价值

目的：探讨磁共振弥散加权成像（MR diffusion weighted imaging,MR-DWI）多b值水通道蛋白（Aquaporin,AQP）分子成像技术在肝纤维化早期诊断的价值.方法：应用乙酰唑胺作为水通道蛋白抑制剂,将对照组及肝纤维化模型组大鼠分别于乙酰唑胺静脉注射抑制前后进行常规MRI及DWI扫描.DWI扫描多b值包括0～4 500 s/mm2共18个不同b值,先按照常规方法获得“标准”表观弥散系数（ADC）值,然后再分别以200、1 500作为界值将其分为低、中和高b值.以病理学肝纤维化分期将大鼠分为S0、S1、S2、S3、S4期,比较低、中、高b值下,不同纤维化分期大鼠肝脏ADC值,并观察同一分期大鼠乙酰唑胺抑制前后,肝脏组织细胞膜上AQP表达量和活性变化情况.结果：“标准”ADC值在各分期之间均无显著性差异.在肝纤维化早期,随着肝纤维化程度的进展,肝脏组织细胞膜上AQP1表达相应增加.乙酰唑胺抑制前,在高b值下,S0期ADC值显著低于S3、S4期（P＜0.05）,其余各组比较均无明显统计学差异;但乙酰唑胺抑制后,高b ADC值比较,S0与S1比较无明显统计学差异,S0与其他各期比较、S1与S2、S1与S3/S4比较,均有明显统计学差异（均P＜0.05）.各组内乙酰唑胺抑制前后自身比较,SO、S1期抑制率分别为15.5％、16.0％,S2期抑制不明显1.9％,S3＋S4期为11.7％.结论：初步实验表明,常规方法获得“标准”ADC值并不能发现肝脏纤维化早期病变,也不能有效对其分期.磁共振DWI多b值扫描,主要是高b值下ADC值变化与肝脏细胞膜上AQP表达相关,该技术可以用于评价早期肝纤维化和对肝脏纤维化分期.     

The utility of near-infrared spectroscopy in the regression of low-frequency physiological noise from functional magnetic resonance imaging data

Near-infrared spectroscopy (NIRS) signals have been shown to correlate with resting-state BOLD-fMRI data across the whole brain volume, particularly at frequencies below 0.1 Hz. While the physiological origins of this correlation remain unclear, its existence may have a practical application in minimizing the background physiological noise present in BOLD-fMRI recordings. We performed simultaneous, resting-state fMRI and 28-channel NIRS in seven adult subjects in order to assess the utility of NIRS signals in the regression of physiological noise from fMRI data. We calculated the variance of the residual error in a general linear model of the baseline fMRI signal, and the reduction of this variance achieved by including NIRS signals in the model. In addition, we introduced a sequence of simulated hemodynamic response functions (HRFs) into the resting-state fMRI data of each subject in order to quantify the effectiveness of NIRS signals in optimizing the recovery of that HRF. For comparison, these calculations were also performed using a pulse and respiration RETROICOR model. Our results show that the use of 10 or more NIRS channels can reduce variance in the residual error by as much as 36% on average across the whole cortex. However the same number of low-pass filtered white noise regressors is shown to produce a reduction of 19%. The RETROICOR model obtained a variance reduction of 6.4%. Our HRF simulation showed that the mean-squared error (MSE) between the recovered and true HRFs is reduced by 21% on average when 10 NIRS channels are applied and by introducing an optimized time lag between the NIRS and fMRI time series, a single NIRS channel can provide an average MSE reduction of 14%. The RETROICOR model did not provide a significant change in MSE. By each of the metrics calculated, NIRS recording is shown to be of significant benefit to the regression of low-frequency physiological noise from fMRI data.     

磁共振成像对胆管癌的诊断价值

目的 探讨胆管癌的MRI和MRCP表现，评价MRI结合MRCP对胆管癌的诊断价值。方法 对62例经手术病理证实的胆管癌，回顾性分析其MRI和MRCP表现。结果 肝内胆管癌11例表现为肝内不规则长T1、长T2浸润性信号，增强后呈中度环形强化。肝门胆管癌16例，MRI主要表现为肝内胆管扩张，在肝门部胆管突然截断、中断或充盈缺损，肝门部软组织肿块。肝外胆管癌35例，MRI表现为肝内胆管软藤样扩张，胆总管不同部位完全性梗阻。MRCP可显示扩张的肝内外胆管及梗阻部位的狭窄、中断、截断和管腔内的充盈缺损。结论 MRI和MRCP联合应用能较好地对胆管癌进行诊断，并能准确描述和评价胆管癌扩散及浸润范围。     

前庭阵发症的MRI研究进展

前庭阵发症(vestibular paroxysmia,VP)是指反复短暂发作的旋转或非旋转性眩晕。该文综述了目前用于显示VP患者神经血管结构异常的多种成像方法,以期对VP影像学诊断及其发病机制的研究提供参考。     

Brain and heart magnetic resonance imaging/spectroscopy in duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X‐linked muscle disorder characterized by progressive and irreversible loss of muscular function. As muscular disease progresses, the repair mechanisms cannot compensate for cellular damage, leading inevitably to necrosis and progressive replacement by fibrous and fatty tissue. Cardiomyopathy and respiratory failure are the main causes of death in DMD. In addition to the well‐described muscle and heart disease, cognitive dysfunction affects around 30% of DMD boys. Myocardial fibrosis, assessed by late gadolinium enhancement (LGE), using cardiovascular magnetic resonance imaging (CMR), is an early marker of heart involvement in both DMD patients and female carriers. In parallel, brain MRI identifies smaller total brain volume, smaller grey matter volume, lower white matter fractional anisotropy and higher white matter radial diffusivity in DMD patients. The in vivo brain evaluation of mdx mice, a surrogate animal model of DMD, showed an increased inorganic phosphate (P(i))/phosphocreatine (PCr) and pH. In this paper, we propose a holistic approach using techniques of magnetic resonance imaging, spectroscopy and diffusion tensor imaging as a tool to create a “heart and brain imaging map” in DMD patients that could potentially facilitate the patients’ risk stratification and also future research studies in the field.     

MRI在肌肉疾病中的临床应用

目的:研究肌肉疾病的MRI表现,评价MRI在肌肉疾病诊断中的应用价值。材料和方法:选择骨盆、双侧大腿及双侧小腿肌肉,对53例经病理活检证实的肌肉疾病患者及4例健康人行MRI检查,进行性肌营养不良症(PMD)31例,其中假肥大型进行性肌营养不良症(Duchenne型PMD,DMD)16例,肢带型PMD 5例,面肩肱型PMD 10例;多发性肌炎(PM)9例;脂质沉积性肌病(LSM)9例;神经源性肌病4例。结果:全部DMD、肢带型PMD及神经源性肌病患者的受累肌肉均表现为短T1、长T2信号;面肩肱型PMD、PM与LSM的受累肌肉表现为两种信号改变:一种为长T1、长T2信号,另一种为短T1、长T2信号。结论:各型神经肌肉疾病具有不同MRI表现;MRI能为临床在肌肉疾病的诊断、鉴别诊断、疗效判断及病情随访中提供客观的资料,并能为临床选取准确的活检部位提供定位。     

磁共振扩散峰度成像在人体肾脏的应用

目的探讨磁共振扩散峰度成像(diffusion kurtosis imaging,DKI)在人体肾脏应用的可行性。材料与方法收集2016年3月至2017年2月在我院招募的健康男性志愿者35例,最终纳入30例。采用3.0 T MR进行双侧肾脏冠状位扫描,扫描序列包括:T1WI、T2WI与DKI序列;DKI采用三个不同b值(0、500s/mm2、1000 s/mm2)和30个扩散敏感梯度方向。采用配对t检验对肾皮质、髓质DKI参数进行组间比较。结果正常人左、右两侧肾皮质、髓质DKI均无统计学差异(P>0.05)。正常人肾脏皮质峰度参数值MK值、Ka值及Kr值均高于髓质(P<0.05);皮质的扩散参数FA值、Da值明显低于髓质,MD值、Dr值高于髓质(P<0.05)。结论肾脏的DKI成像不仅能够反映肾皮质、髓质水分子扩散状态差异,而且其特有的峰度参数值还能够提供更多关于肾皮质、髓质微结构的信息。     

超顺磁性氧化铁粒子增强MR成像在脾脏荷VX2肿瘤动物模型的影像学与病理学对照研究

目的：建立大鼠脾脏VX2肿瘤模型，分析大鼠脾VX2肿瘤超顺磁性氧化铁（SPIO）增强MR图像上信号强度变化与病理学改变之间的关系。探讨SPIO增强MR在大鼠脾脏转移瘤的应用价值。材料和方法：制作8只脾脏荷VX2肿瘤模型鼠，注射SPIO后行MR扫描，扫描序列采用T1WI（450/12ms)和T2WI（4000/128ms）。分析SPIO增强扫描前后MR图像上不同组织的信号特点。结果：SPIO增强T2WI MR图像上正常脾实质信号强度下降百分比（PSIL）为55.04％；脾脏VX2肿瘤PSIL为0.87％，与正常脾实质的信号强度下降程度有显著性差异（P<0.001）。脾VX2肿瘤的CNR较增强前显著提高（P<0.001）。结论：SPIO增强T2WI MR图像上脾脏－肿瘤的对比显著，提高了病灶的检出率，改善了病灶的影像学特征的描述。     

磁共振分子影像学研究进展

磁共振分子影像是分子影像学的重要分支,具有其他成像技术不可比拟的优越性和广阔的发展前景.近年来,新型磁共振靶向探针及成像序列的研发取得了一系列进展,包括可激活探针、19F成像、超极化成像以及化学交换饱和转移成像等方面,进一步拓展了磁共振分子影像的应用范围.此外,磁共振分子成像在多系统疾病的早期诊断、代谢成像、细胞示踪及基因分析等方面也发挥着巨大优势.尽管磁共振分子成像距离临床转化还存在着一定差距,随着成像技术的日新月异,其在临床疾病诊治中必将发挥重要价值.     

前注意视觉皮层脑功能磁共振成像

目的 探讨前注意视觉皮层的非注意视觉偏差刺激自动加工脑功能解剖的分布及意义。方法 对20名健康右利手男性,采用经典oddball被动范式给予非注意视觉刺激,标准刺激为红色方块,概率为80%,偏差刺激为绿色方块,概率为20%,观察功能MRI影像学表现。结果 最终分析15名被试,fMRI检查前、中、后的按键正确率均≥95%,反应时间差异无统计学意义(P=0.470)。fMRI显示右侧梭状回(枕颞内侧回)、右侧部分颞叶、枕叶及海马旁回,左侧枕叶,双侧额上回、双侧额中回及左侧中央前回/后回脑激活区BOLD信号在偏差刺激出现后明显升高。结论 fMRI可以清楚显示前注意视觉皮层功能解剖分布,为临床诊断前注意视觉皮层受损情况提供更加直观的检查方式,为疾病研究提供相应的参考信息。