实验性缺氧缺血性脑病的~1H-MRS及病理学研究

目的:探讨早期新生猪缺氧缺血性脑病(HIE)的1H-MRS波峰变化规律及其与病理学改变的关系。方法:选取40只7日龄健康新生猪,随机分为:正常对照组(n=5只)、假手术组(n=5只)及缺氧缺血组(n=30只)。1.5T磁共振1H MRS测定脑内代谢产物。观察每组新生猪脑组织的病理变化情况。结果:①造模后0~24h,NAA峰明显下降,Lac峰呈典型的双峰状显著升高,NAA/Cho、Lac/NAA、Lac/Cr、Lac/Cho和Lac/(Cr Cho)比值逐渐降低,HI后3h,NAA/Cr、NAA/(Cr Cho)比值升高,然后逐渐降低,Glx峰和mI峰无明显变化。②造模后0~24h随着时间延长脑水肿逐渐加重,24h出现坏死灶。结论:①NAA/Cho、Lac/NAA、Lac/Cr、Lac/Cho和Lac/(Cr Cho)是定量反映脑缺氧缺血生化改变的最敏感指标;②早期缺氧缺血后脑NAA、Lac与病理学的变化一致。     

新生猪缺氧缺血脑损伤治疗时间窗初探:1HMRS与HSP70对照研究

目的探讨新生猪缺氧缺血性脑损伤(HIBD)治疗时间窗的存在及其意义。方法生后7天约克种白猪30头,随机分成对照组(5头)和实验组(25头)。实验组分5组,每组5头,双侧颈总动脉结扎加4%低氧通气1h,分别于缺血缺氧(HI)后0、6、12、18和24h进行磁共振频谱分析(MRS),各时间点MR扫描后作脑组织热休克蛋白70(HSP70)表达的免疫组化研究。结果实验组HI后0h,Lac/NAA、Lac/Cho、Lac/Cr明显增高,NAA/Cho、NAA/Cr下降,未见明显HSP70阳性表达细胞;HI后6~18h,NAA峰呈现进行性增高趋势,NAA/Cho、NAA/Cr比值升高,Lac峰呈进行性下降趋势,Lac/NAA、Lac/Cho、Lac/Cr降低,HSP70阳性表达细胞进行性增加;HI后24h,NAA峰再次下降,NAA/Cho、NAA/Cr降低,Lac峰则再度明显升高,Lac/NAA、Lac/Cho、Lac/Cr均增高,HSP70阳性表达细胞明显减少;对照组各时间点MRS未见异常,脑组织未见HSP70阳性表达细胞。结论MRS可以比较准确地反映缺氧缺血性脑病的病理生理学演变过程,结合HSP70的表达,在探讨HIE的治疗时间窗的存在及其意义上具有重要价值,在HIE的发生发展过程中确实存在潜在的治疗时间窗。     

质子磁共振波谱对脑肿瘤的鉴别诊断价值

目的初步探讨氢质子磁共振波谱(1H-MRS)对不同脑肿瘤的诊断及鉴别诊断价值.材料和方法39例颅内肿瘤分别行常规MRI及1H-MRS检查,将肿瘤实质与对侧相应部位及正常对照组行对照研究.检查方法为PRESS序列,主要观察代谢物为氮-乙酰天门冬氨酸(NAA)、含胆碱的化合物(Cho)、肌酸(Cr/PCr)、乳酸(Lac)和脂类(Lipids).结果几乎所有肿瘤波谱均呈现NAA峰降低,Cho升高,Cho/Cr及Cho/NAA比值升高,与正常组织相比有显著性差异(p＜0.05).低度恶性胶质瘤组8例Cho/Cr、NAA/Cr、NAA/Cho代谢物比值分别为1.87±0.45、1.13±0.26、0.74±0.21;高度恶性胶质瘤组7例的代谢物比值的均值分别为2.75±1.17、1.07±0.31和0.62±0.28;脑膜瘤组11例,其代谢物比值的均值分别为6.04±2.15、0和0;转移瘤组10例,其代谢物比值的均值分别为2.32±1.08、1.22±0.17和1.23±0.46.胶质瘤组2例术后与术前比较Cho/Cr比值有明显降低.淋巴瘤1例放疗后较放疗前Cho/Cr比值降低;听神经鞘瘤1例见升高的Cho峰;蛛网膜囊肿1例仅见Lac峰.结论H1-MRS对脑肿瘤的诊断及鉴别诊断、治疗后随访、手术后疗效的评价均有重要价值,可作为一种非损伤性的辅助诊断手段.     

MRS定量测量急性缺氧缺血脑损伤猪脑代谢物研究

目的 评价外标准法MRS结合LCModel软件绝对定量测量急性缺氧缺血脑损伤猪脑N-乙酰天冬氨酸(NAA)、肌酸(Cr)和乳酸(Lac)浓度变化的价值.方法 8头7日龄健康猪麻醉后未作任何处理(正常组),麻醉清醒后1 d制成缺氧缺血性脑病(HIE)模型(HIE组),先后与内含已知浓度物质的外标准模型一起行1H-MRS检查,数据采集完毕后用LCModel软件定量分析测量NAA、Cr、Lac浓度,HIE前、后猪脑代谢物NAA、Cr、Lac间比较采用多元方差分析,并对2头HIE猪缺氧缺血0、2 h脑代谢物动态变化情况作初步观察.结果 l头猪因麻醉过深死亡而剔除,最后统计数据为7头.小猪急性缺氧缺血前脑NAA、Cr、Lac分别为(6.86±0.49)、(4.65±0.73)、0.00 mmol/kg,缺氧缺血后即刻脑NAA、Cr、Lac分别为(5.73±0.88)、(4.40±0.80)、(0.43±0.39)mmol/kg.急性缺氧缺血后即刻猪脑NAA浓度下降,差异有统计学意义(F=8.608,P=0.013);Cr浓度有所下降,但差异无统计学意义(F=0.379,P=0.550);Lac浓度升高,差异有统计学意义(F=8.600,P=0.013).初步观察脑代谢物动态变化见HIE后即刻出现Lac峰,2 h Lac峰下降.结论 外标准法MRS结合LCModel定量分析软件能方便准确地定量测量脑内代谢物,NAA与Lac浓度的改变均能敏感地反映急性缺氧缺血脑损伤早期改变,且以NAA浓度的改变稍敏感.     

阻塞性睡眠呼吸暂停综合征的质子磁共振波谱研究

目的:探讨阻塞性睡眠呼吸暂停综合征(OSAS)的质子磁共振波谱(1H-MRS)改变及其临床应用价值.方法:分别对33例OSAS患者和20例健康志愿者行1H-MRS,经多导睡眠仪监测将患者分为轻度OSAS(16例)和中重度OSAS(17例),分别测量脑灰质和脑白质的代谢物包括氮-乙酰天门冬氨酸(NAA)、胆碱(Cho)、肌酸(Cr)和乳酸(Lac)的波峰下面积,计算NAA/Cho、NAA/Cr、Cho/Cr,对组间代谢物比值的差异进行统计学分析.结果:中重度OSAS患者白质区NAA/Cho(1.56±0.21)低于轻度OSAS患者(1.88±0.23)及正常对照组(1.89±0.25),差异有显著性意义(P<0.01),NAA/Cr轻度降低,Cho/Cr轻度升高,但与轻度OSAS患者和正常对照组比较,无统计学意义(P>0.05).轻度OSAS患者灰、白质NAA/Cho、NAA/Cr、Cho/Cr 与正常对照组之间差异均无显著性意义(P>0.05).结论:1H-MRS能够早期发现OSAS患者的脑代谢异常,对临床诊断和治疗具有重要价值.     

胼胝体变性的扩散加权成像和多体素氢质子波谱分析

目的 探讨扩散加权成像(DWI)和多体素氢质子波谱(1H-MRS)在急性和亚急性胼胝体变性(MBD)中的应用价值. 资料与方法 5例长期酗酒男性MBD 患者均经DWI检查,其中急性型3例经1H-MRS检查,测量DWI不同信号病灶的ADC值,多体素1H-MRS采集胼胝体病灶的胆碱复合物(Cho)、氮-乙酰天门冬胺酸(NAA)、肌酸(Cr)等波峰,计算Cho/Cr、NAA/Cr及Cho/NAA的比值. 结果 大部分病灶在DWI上表现为高和稍高信号,根据液体衰减翻转恢复序列(FLAIR)、DWI、ADC图上病灶信号的不同分为3组,不同病灶区的ADC值表现为不同程度升高或降低.1H-MRS示胼胝体病灶的Cho/Cr升高,NAA/Cr不同程度下降,1例探测到倒置的乳酸(Lac)峰,所有胼胝体病灶的Cho/NAA均明显升高,比值在2.03～2.53之间.结论 DWI和1H-MRS分别可以提供MBD所致脑组织微观结构的改变和局部代谢物变化方面的信息,对于MBD的诊断具有重要价值.     

急性颈髓创伤MRS

目的探讨MR质谱(1H-MRS)与MRI对急性颈髓损伤的诊断价值.材料和方法对19例急性颈髓损伤病人行MRI与1H-MRS检查,根据MRI表现与临床神经功能分组并计算氮-乙酰天门冬氨酸(NAA)、胆碱(Cho)、肌酸(Cr)、乳酸(Lac)波峰面积,分析NAA/Cho、NAA/Cr、Cr/Cho、Lac/Cho各值变化,并取9例健康者作对照.结果颈髓完全性损伤组NAA/Cho、NAA/Cr、Cr/Cho、Lac/Cho各值为0.4l、0.4l、1.08、4.2l,不完全损伤组为0.96、0.90、1.05、2.44,对照组为1.1、1.23、1.05、1.3.颈髓完全损伤组与对照组比NAA/Cho、NAA/Cr值降低,Lac/Cho值升高(p＜0.01),不完全损伤组仅Lac/Cho值升高(p＜0.05).颈髓损伤不同程度中,完全损伤组较不完全损伤组中NAA/Cho、NAA/Cr显著减低(p＜0.05).结论1H-MRS可定量测定创区颈髓相关代谢介质的变化,从代谢水平反映颈髓损伤的不同程度,MRI结合1H-MRS有利于颈髓损伤评价.     

小儿正常小脑半球组织~1H-MRS研究

目的:测定和计算0～7岁小儿正常小脑半球组织代谢物比值,并观察各比值随年龄变化规律。方法:应用多体素2D1H-MRS点分辨波谱(PRESS)序列测定70例0～7岁小儿正常小脑半球组织的双侧灰质及白质区代谢物浓度,按年龄分为0-1岁,1-2岁,2-3岁,3-5岁,5-7岁五组,计算和分析NAA/Cr、Cho/Cr、NAA/Cho的比值。结果:正常小脑灰质区在各年龄组间NAA/Cho(P=0.0143)和NAA/Cr(P=0.0050);白质区的NAA/Cho和NAA/Cr均P<0.001;灰质和白质区的Cho/Cr(P=0.1195,P>0.05);灰质和白质区NAA/Cho值与年龄呈正相关(P<0.001,P<0.0001);NAA/Cr值与年龄呈正相关(P=0.0004,P<0.0001);灰质区Cho/Cr与年龄呈负相关(P=0.038),白质区与年龄呈负相关(P=0.568>0.05)。结论:0～7岁小儿正常小脑半球灰、白质的代谢物比值在不同年龄组会不同,灰质和白质区NAA/Cho、NAA/Cr值随年龄增长逐渐升高,而灰质区Cho/Cr值逐渐减小,白质区无明显变化,临床上应用MRS要考虑其年龄和部位的因素。     

肾上腺脑白质营养不良的MR功能成像表现分析

目的探讨磁共振扩散加权成像(DWI)的信号及波谱(MRS)的代谢异常变化与肾上腺脑白质营养不良(ALD)病理、生化改变的对应性。方法分析6例血浆极长链脂肪酸增高证实的ALD的病变不同区域表观扩散系数(ADC)和磁共振波谱N乙酰天门冬氨酸(NAA)、胆碱复合物(Cho)和乳酸(Lac)的代谢变化,比较病变的位置不同和时间不同在ADC值和代谢变化中的差异。结果病灶最早发生的枕顶叶脑白质区域,DWI信号很低,ADC值最高(2.400×10-3mm2/s,F=7.31,P=0.003),NAA/Cr和NAA/Cho降低(0.62±0.24,F=4.00,P=0.02;0.32±0.16,F=6.75,P=0.02),Cho/Cr和Lac/Cr增高(1.96±0.53,F=3.53,P=0.03;0.28±0.24,F=3.22,P=0.04)。在病灶向前扩展的区域中,DWI信号最高,而ADC值最低[(0.749～0.752)×10-3mm2/s,F=7.31,P=0.003],灶周近区NAA/Cr和NAA/Cho降低较远区明显(q2=-0.23,p2=0.047;q2=-0.23,p2=0.02),Cho/Cr和Lac/Cr的增高无统计学意义(q2=0.34,p2=0.19;q2=0.11,p2=0.17)。结论磁共振功能成像能够动态观察营养不良的脑白质的空间时间演变顺序。陈旧性病灶,ADC值升高,Cho和Lac均升高,NAA下降明显。进展区的病灶,ADC明显降低,Cho和Lac的升高变化较前者并不显著,残存的神经元和轴索的保留使NAA的水平部分下降。     

磁共振波谱在早产儿神经系统发育落后早期预测的价值

目的探讨早产儿1H-MRS脑内代谢物与Gesell发育商间的相关性,为早产儿神经系统发育落后的早期诊断及预测提供帮助。方法对我院符合条件的45例早产儿及30例同期足月儿于出生后1周内行1H-MRS检查,计算脑内代谢物NAA/Cr、Cho/Cr、m I/Cr、Lac/Cr、Glx/Cr比值;并于出生后40~52周行Gesell发育诊断量表检测,得出发育商及其5个能区对应的发育商值,同时分析早产儿组发育商与脑内各代谢物间的相关性。结果早产儿组NAA/Cr显著低于足月儿组,差异有统计学意义(t=-6.202,P0.001),但Cho/Cr、Lac/Cr、Glx/Cr均显著高于足月儿组,差异有统计学意义(P0.001)。早产儿组发育商及其各能区均显著低于足月儿组,差异有统计学意义(P0.001)。多元线性回归模型显示发育商与NAA/Cr及Lac/Cr存在显著相关性(决定系数为0.418)。结论早产儿早期1H-MRS脑内代谢物质(NAA、Lac)与Gesell发育商有相关性,NAA、Lac的变化可以早期预测早产儿可能发生的神经系统发育落后。     

Stress MR imaging for evaluation of popliteal artery entrapment

The popliteal artery entrapment (PAE) syndrome has been recognized as a cause of arterial occlusion in young people. It is the result of an anomaly of the relationship between the popliteal artery and the gastrocnemius muscle. Eight young healthy volunteers (16 legs) and six patients (10 legs) with suspected PAE underwent magnetic resonance (MR) imaging. Gradient-echo images were obtained in axial planes with the leg at rest and during active plantar flexion against resistance. Imaging at rest allowed identification of PAE signs in only one leg, which had an anomalous medial course of the popliteal artery. In the other cases, only the stress technique was able to show signal loss in the popliteal artery due to muscular compression (two legs) or the presence of accessory muscle slip around the vessel (two legs), as confirmed at surgery. MR imaging is therefore a useful technique for the diagnosis of PAE because of its capability of combining information obtainable with other modalities.     

MR imaging of muscle and tender points in fibromyalgia

Fibromyalgia is a syndrome manifested by chronic, diffuse muscu-loskeletal aching and soreness, palpable muscle tender points, and other symptoms. Standardized clinical diagnostic criteria have recently been developed. Skeletal muscle has been postulated as the end organ in this disease. Biochemical, histologic, electromyographic, and conventional radiographic studies have demonstrated no definitive abnormality. This study sought to establish whether magnetic resonance (MR) imaging could demonstrate any abnormality in these patients. Eighteen patients were entered in the study, 14 of whom were able to complete their examinations. T1 -weighted, T2-weighted, gradient-echo, and STIR (short-tau inversion-recovery) sequences were performed in all patients, with selected patients examined with T1weighted, gadopentetate dimeglu-mine-enhanced sequences. The trapezius and suboccipital regions were imaged in patients who, clinically, had active fibro-myalgia. No abnormalities could be detected. The authors conclude that the conventional MR imaging used in this study was unable to depict any primary skeletal muscle abnormality in fibromyalgia.     

Controversies in cervical spine imaging in trauma patients

No area of emergency radiology has generated as much discussion in recent years as the subject of cervical spine imaging for trauma patients. This review will be in three parts. The first will examine the indications for cervical imaging and will focus on those factors that make patients at high risk or low risk for cervical injury. The second part will discuss the merits of radiography and computed tomography as the main screening diagnostic examination. In addition to the roles of each modality in the evaluation process, such factors as efficacy of diagnosis, time (duration) of study, and cost will be discussed. Finally, the third part will explore the methods currently employed to clear the cervical spine in comatose patients.Presented at the Annual Meeting of the American Society of Emergency Radiology, Las Vegas, Nevada, 22–25 October, 2003     

Uterine contractions: Possible diagnostic pitfall at MR imaging

A total of 206 nongravid patients with various gynecologic problems underwent pelvic magnetic resonance (MR) examinations that included both sagittal T2-weighted and contrast agent–enhanced T1-weighted images. MR images were retrospectively reviewed to identify changes in endometrial configuration on serial images obtained during the same MR examination. In 20 MR examinations (all in women of reproductive age), endometrial distortion due to myometrial bulging was noted on T2-weighted or contrast-enhanced T1-weighted images. It was absent on other MR images obtained at different times. Myometrial bulging exhibited low signal intensity in 18 examinations. The finding resembled adenomyosis or leiomyoma on T2-weighted or contrast-enhanced T1-weighted images. These results evidence the presence of transient myometrial bulging and transient low-intensity myometrium in the nongravid uterus. This phenomenon is thought to represent uterine contraction. Clinicians should be aware of the potential presence of transient low-signal-intensity myometrial bulging that could present diagnostic problems in the normal uterus.     

Brodie Abscess: MR imaging appearance in 10 patients

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR (short-inversion-time inversion recovery) images, (b) an inner ring isointense to muscle on T1-weighted images and with high signal intensity on T2-weighted and STIR images, (c) an outer ring hypoin-tense on all images, and (d) a peripheral halo hypointense on T1-weighted images. In six of eight cases, a soft-tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR images. Only the peripheral halo was clearly identified in both cases.     

Dynamic contrast-enhanced MR imaging assessment of vascularized free fibular grafts

Magnetic resonance (MR) imaging may be a noninvasive method for assessing perfusion of vascularized bone grafts placed for treatment of avascular necrosis. One proximal femur of seven beagles was devascularized, with insertion of a vascularized fibular graft. MR imaging at 1 week (seven dogs) and 6 weeks (five dogs) after surgery included pre- and postcontrast spin-echo sequences, unenhanced twodimensional time-of-flight (TOF) vascular imaging, and dynamic gradient-echo imaging during infusion of gadolinium. Relative signal intensity values of selected regions obtained from the dynamic gradientecho images were plotted as percent enhancement versus time. In the operated hip, MR imaging did not show enhancement in six of seven femoral heads and greater trochanters at 1 week after surgery, with similar results after 6 weeks. MR imaging of fibular grafts 6 weeks after surgery showed an initial rapid increase in enhancement and a subsequent slower increase in five of five dogs, although no enhancement was seen in six of seven dogs at 1 week. These findings contrasted with a rapid initial increase in enhancement followed by slow decline in non-operated hips. Two-dimensional TOP imaging did not show the vascular pedicle of the graft in any dog. Findings of radionuclide bone scanning performed 1 week after surgery were consistent with devascularization of the operated femur and fibular graft. However, tetracycline distribution and histologic findings confirmed the viability of five of five grafts within the devascularized femurs 6 weeks after surgery. Thus, dynamic contrast-enhanced MR imaging at 6 weeks after surgery is valuable for assessing vascular bone graft perfusion, while similar imaging at 1 week may suggest otherwise.     

Right-side aortic arch with aneurysm of aberrant left subclavian artery: MR imaging appearance.

Reports of aneurysms of the subclavian artery in both normal and anomalous aortic arches have been rare. The authors describe a patient with a right-side aortic arch and an aneurysm of the aberrant left subclavian artery, which, to the authors' knowledge, is a previously unreported association. At presentation, the aneurysm appeared as a calcified left superior mediastinal mass. Magnetic resonance imaging enabled preoperative diagnosis and guided surgical planning.     

Adrenal tissue characterization with 0.5-T MR imaging: Value of T2*-weighted images

The authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor–liver signal intensity ratios on T1-, T2-, and T2*-weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21 of 23, 91%) than on T2-weighted images (15 of 23, 65%). T1-weighted images were not useful for this distinction. In conclusion, T2*-weighted images were better than routine T2-weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*-weighted images because of an out-of-phase effect.     

MR angiography of congenital heart disease: Value of segmented two-dimensional inflow technique and maximum-intensity-projection display

Magnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two-dimensional (2D) inflow technique based on a magnetization-prepared gradient-echo pulse sequence with segmented k-space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40–50 overlapping sections. Both 2D angiograms and maximum-intensity-projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal-to-noise ratios were obtained with a flip angle of 65° and short prepulse delay times. Two-dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in-plane and hemodynamically induced signal intensity changes.