脑功能磁共振成像研究进展

主要综述fMRI产生的历史、成像原理、成像技术和方法、已经取得的成绩以及将来研究发展的方向等。fMRI产生技术广泛应用的20世纪90年代,主要受快速成像技术的影响,从有创走向无创,从而受到神经、认知和心理科学领域的极大关注。fMRI原理是根据神经元兴奋后局部氧耗与血流增幅不一致,而BOLD效应机制成像,间接显示神经元活动。成像主要采用平面回波成像（EPI）和快速小角度激发（FLASH）技术、二者在时间和空间分辨率上各有优劣。最后几年来,fMRI技术对脑功能的研究已取得了巨大的成绩,估计将在这一领域继续拥有非常重要的地位。将来fMRI可能主要在BOLD效应的生理过程、临床应用以及高场磁体的应用等领域进一步展开。     

Multimodal biological brain age prediction using magnetic resonance imaging and angiography with the identification of predictive regions

Biological brain age predicted using machine learning models based on high‐resolution imaging data has been suggested as a potential biomarker for neurological and cerebrovascular diseases. In this work, we aimed to develop deep learning models to predict the biological brain age using structural magnetic resonance imaging and angiography datasets from a large database of 2074 adults (21–81 years). Since different imaging modalities can provide complementary information, combining them might allow to identify more complex aging patterns, with angiography data, for instance, showing vascular aging effects complementary to the atrophic brain tissue changes seen in T1‐weighted MRI sequences. We used saliency maps to investigate the contribution of cortical, subcortical, and arterial structures to the prediction. Our results show that combining T1‐weighted and angiography MR data led to a significantly improved brain age prediction accuracy, with a mean absolute error of 3.85 years comparing the predicted and chronological age. The most predictive brain regions included the lateral sulcus, the fourth ventricle, and the amygdala, while the brain arteries contributing the most to the prediction included the basilar artery, the middle cerebral artery M2 segments, and the left posterior cerebral artery. Our study proposes a framework for brain age prediction using multimodal imaging, which gives accurate predictions and allows identifying the most predictive regions for this task, which can serve as a surrogate for the brain regions that are most affected by aging.     

MR序列优化组合在创伤性脑损伤的诊断价值

目的分析MR诊断创伤性脑损伤(TBI)的价值,探讨TBI患者MR一站式诊断的可行性。方法对260例TBI病例进行MR序列组合扫描,包括小角度激发快速梯度回波序列(FLASH)、流动衰减反转恢复序列(FLAIR)、自旋回波(SE)T1WI、快速自旋回波(TSE)T2WI,比较MR序列组合和CT对各种类型TBI诊断的差异。结果脑实质内出血61例,MR显示61例,CT显示53例;硬膜下出血55例,MR显示55例,CT显示49例;硬膜外出血45例,MR显示45例,CT显示40例;脑挫(裂)伤35例,MR显示35例,CT显示25例;蛛网膜下腔出血35例,MR显示31例,CT显示33例;弥漫性轴索损伤29例,MR显示29例,CT显示5例。MR序列组合准确显示病变256例,CT为209例,两者差异有极显著统计学意义(P0.01),MR序列组合总体诊断敏感性高于CT。结论 MR序列组合(FLASH\FLAIR\T1WI\T2WI)诊断创伤性脑损伤明显优于CT,可列为TBI常规检查方法,实行TBI一站式诊断。     

Invited Review: Factors associated with atypical brain development in preterm infants: insights from magnetic resonance imaging

Preterm birth (PTB) is a leading cause of neurodevelopmental and neurocognitive impairment in childhood and is closely associated with psychiatric disease. The biological and environmental factors that confer risk and resilience for healthy brain development and long-term outcome after PTB are uncertain, which presents challenges for risk stratification and for the discovery and evaluation of neuroprotective strategies. Neonatal magnetic resonance imaging reveals a signature of PTB that includes dysconnectivity of neural networks and atypical development of cortical and deep grey matter structures. Here we provide a brief review of perinatal factors that are associated with the MRI signature of PTB. We consider maternal and foetal factors including chorioamnionitis, foetal growth restriction, socioeconomic deprivation and prenatal alcohol, drug and stress exposures; and neonatal factors including co-morbidities of PTB, nutrition, pain and medication during neonatal intensive care and variation conferred by the genome/epigenome. Association studies offer the first insights into pathways to adversity and resilience after PTB. Future challenges are to analyse quantitative brain MRI data with collateral biological and environmental data in study designs that support causal inference, and ultimately to use the output of such analyses to stratify infants for clinical trials of therapies designed to improve outcome.     

Correlates between nuclear magnetic resonance spectroscopy,diffusion weighted imaging and CA1 morphometry following chronic brain ischemia

Chronic brain ischemia (CBI) was induced in aging (13 month) rats by ligating the left subclavian artery and placing temporary occluders in each common carotid artery [three-vessel occlusion (3-VO)]. Carotid artery occluders were removed after 1, 2, or 3 weeks following brain ischemia or maintained for 9 weeks. Two rats were kept with their occluders in place for 25 weeks. On weeks 3 and 9 after CBI, ³¹ P-/¹H-nuclear magnetic resonance (NMR) spectroscopy and high resolution diffusion weighted imaging were performed in vivo, non-invasively for detection of hippocampal high energy phosphates, lactate, intracellular pH, N-acetyl-aspartate, choline, glutamate, creatine, and structural alterations of the brain following CBI. Brains were histologically processed for morphometry of glial fibrillary acidic protein (GFAP) and CA1 damaged neurons 9 weeks after CBI. ³¹P-/¹H-NMR spectroscopy showed that high energy substrates remained normal in ischemic animals when compared to non-ischemic controls except for an elevation of phosphomonoesters in the hippocampal region. Rats deoccluded 1 and 2 weeks after initiation of CBI had no NMR spectroscopic or imaging changes. Rats kept ischemic for 9 weeks showed high signal intensities in the parietal cortex detected by diffusion weighted imaging as well as CAI damage and increased GFAP density but no cortical atrophy or neuronal damage could be detected histologically. Rats kept ischemic for 25 weeks showed extensive cortical atrophy which corresponded to the high, signal intensity observed with diffusion weighted imaging in the group kept ischemic for 9 weeks. These findings indicate that NMR spectroscopy and difussion weighted imaging can be used to follow the progress of neuronal injury in vivo and non-invasively. Moreover, diffusion weighted imaging may be an excellent predictor of cerebral damage and atrophy prior to histopatholog ical detection of such damage. Our present and previous findings using our 3-VO model indicate that this aging rat model may be useful in screening potential therapy for neurodegenerative disorders associated with abnormal aging and memory impairment. © 1995 Wiley-Liss, Inc.     

Functional magnetic resonance imaging of mild traumatic brain injury

Functional magnetic resonance imaging (fMRI) offers great promise for elucidating the neuropathology associated with a single or repetitive mild traumatic brain injury (mTBI). The current review discusses the physiological underpinnings of the blood-oxygen level dependent response and how trauma affects the signal. Methodological challenges associated with fMRI data analyses are considered next, followed by a review of current mTBI findings. The majority of evoked studies have examined working memory and attentional functioning, with results suggesting a complex relationship between cognitive load/attentional demand and neuronal activation. Researchers have more recently investigated how brain trauma affects functional connectivity, and the benefits/drawbacks of evoked and functional connectivity studies are also discussed. The review concludes by discussing the major clinical challenges associated with fMRI studies of brain-injured patients, including patient heterogeneity and variations in scan-time post-injury. We conclude that the fMRI signal represents a complex filter through which researchers can measure the physiological correlates of concussive symptoms, an important goal for the burgeoning field of mTBI research.     

Incidental radiological findings on brain magnetic resonance imaging in first-episode psychosis and chronic schizophrenia

OBJECTIVE: To investigate whether patients with first-episode psychosis or chronic schizophrenia have an increased incidence of magnetic resonance imaging (MRI) brain abnormalities compared with control subjects. METHOD: Totally 340 clinical MRI reports [Controls (n=98), first-episode psychoses (n=152), chronic schizophrenia (n=90)] were reported by a neuroradiologist blind to diagnosis and subsequently categorized using referral criteria (immediate, urgent, routine or no referral). RESULTS: Thirty percent of all scans were reported by a neuroradiologist as abnormal, but the majority required no referral. Patients with chronic schizophrenia were more likely to have clinically significant abnormal scans than patients with first episode psychosis or control subjects. In four patients the MRI findings led to the discovery of previously unsuspected pathology. CONCLUSION: Patients with chronic schizophrenia have an increased prevalence of incidental brain abnormalities. A small proportion of patients with chronic schizophrenia and first-episode psychosis benefitted directly from MRI scanning.     

Influence of X chromosome and hormones on human brain development: a magnetic resonance imaging and proton magnetic resonance spectroscopy study of Turner syndrome.

BACKGROUND: Women with Turner syndrome (TS; 45,X) lack a normal second X chromosome, and many are prescribed exogenous sex and growth hormones (GH). Hence, they allow us an opportunity to investigate genetic and endocrine influences on brain development. METHODS: We examined brain anatomy and metabolism in 27 adult monosomic TS women and 21 control subjects with volumetric magnetic resonance imaging and magnetic resonance spectroscopy. RESULTS: In TS women, regional gray matter volume was significantly smaller in parieto-occipital cortex and caudate nucleus and larger in cerebellar hemispheres. White matter was reduced in the cerebellar hemispheres, parieto-occipital regions, and splenium of the corpus callosum but was increased in the temporal and orbitofrontal lobes and genui of corpus callosum. Women with TS had a significantly lower parietal lobe concentration of N-acetyl aspartate, and higher hippocampal choline. Also, among women with TS, there were significant differences in regional gray matter volumes and/or neuronal integrity, depending upon parental origin of X chromosome and oxandrolone and GH use. CONCLUSIONS: X chromosome monosomy, imprinting and neuroendocrine milieu modulate human brain development-perhaps in a regionally specific manner.     

Correspondence of AQP4 expression and hypoxic-ischaemic brain oedema monitored by magnetic resonance imaging in the immature and juvenile rat

Whether the water channel protein AQP4 is involved in the very early cell swelling and brain oedema observed with cerebral hypoxia-ischaemia (HI) and whether this response depends on the maturity of brain were investigated by comparing regional changes in AQP4 protein expression and signal intensity on magnetic resonance (MR) images in immature and juvenile brains. Maps of T2 and the apparent diffusion coefficient (ADC) of water were acquired in 1- and 4-week-old rats at times prior to HI, within the last 5 min of HI and 1 h or 24 h afterwards. AQP4 expression assessed with Western blotting was not significantly reduced until 24 h post-HI irrespective of age. However, AQP4 immunostaining was decreased at the end of HI and at 1 h or 24 h after HI in the hemisphere ipsilateral to the occlusion with changes being similar in both age groups and coinciding well with regional reductions in ADC. IgG immunostaining to assess blood-brain barrier integrity and T2 were unchanged at early time points in 4-week old rats despite decreases in AQP4 immunostaining. Thus, at early time points there were decreases in AQP4 detected with immunostaining but not Western blotting methods. However, the good correlation between alterations in ADC and AQP4 immunostaining suggests that changes in the AQP4 are involved in some of the early changes in brain water distribution observed in hypoxia-ischemia, and supports the speculation that AQP4 is involved in the transport of water across the perivascular membranes into the vascular lumen.     

合成MRI在高级别脑胶质瘤术后复发与放射性损伤鉴别中的应用

目的 探讨合成MRI技术鉴别高级别脑胶质瘤（HCG）术后复发与放射性脑损伤的应用价值。方法 收集2018年1月—2022年12月在安阳地区医院和西安医学院第二附属医院就诊的HCG术后放疗后患者41例,所有患者均接受合成MRI扫描和合成MRI对比增强扫描,并经二次手术病理证实或MRI随访确诊。测量病灶实质区、周围水肿区的增强前T1值（T1-pre）、T2值（T2-pre）和增强后T1值（T1+c）,比较复发组和损伤组间各参数的差异。并绘制ROC曲线评价各参数对复发和损伤的鉴别诊断效能。结果 最终纳入37例,其中21例为复发,16例为放射性脑损伤。复发组和脑损伤组实质区与水肿区T1-pre、T2-pre比较,差异均无统计学意义（均P＞0.05）。复发组实质区和水肿区T1+c低于损伤组,增强前后T1差值（ΔT1）、T1值变化百分比高于损伤组,差异均具有统计学意义（P＜0.05）。实质区和水肿区T1+c、ΔT1、T1值变化百分比对鉴别HCG复发和放射性脑损伤的效能均较高,诊断准确率分别为91.8%、94.6%、94.6%、97.2%和97.2%。结论 合成MRI技术在鉴别HCG术后复发和放射性脑损伤方面具有较好的效能,可辅助临床制定后续治疗方案。 [国际神经病学神经外科学杂志, 2023, 50(6): 40-46]     

Simultaneous functional magnetic resonance imaging in the rat spinal cord and brain

Functional magnetic resonance imaging (fMRI) method was developed to investigate the pattern and temporal relationship in neuronal pathways of brain and spinal cord. Signal intensity changes correlating with stimulation patterns were observed simultaneously in the rat spinal cord and brain using fMRI at 9.4 T. Electrical stimulation of the forepaw was used to elicit activity. A quadrature volume RF coil covering both brain and the cervical spinal cord was used. Sets of fast spin echo (FSE) images were acquire simultaneously for both brain and spinal cord fMRI. Experiments were repeated in single animal and across animals. Activities within the dorsal horn of the spinal cord and within the somatosensory cortex were observed consistently within each animal as well as across animals.     

Diffusion magnetic resonance imaging for Brainnetome: A critical review

Increasing evidence shows that the human brain is a highly self-organized system that shows attributes of smallworldness,hierarchy and modularity.The "connectome" was conceived several years ago to identify the underpinning physical connectivities of brain networks.The need for an integration of multi-spatial and-temporal approaches is becoming apparent.Therefore,the "Brainnetome"(brain-net-ome) project was proposed.Diffusion magnetic resonance imaging(dMRI) is a non-invasive way to study the anatomy of brain networks.Here,we review the principles of dMRI,its methodologies,and some of its clinical applications for the Brainnetome.Future research in this field is discussed.     

Doxycycline treatment in a neonatal rat model of hypoxia-ischemia reduces cerebral tissue and white matter injury: a longitudinal magnetic resonance imaging study

Doxycycline may potentially be a neuroprotective treatment for neonatal hypoxic-ischemic brain injury through its anti-inflammatory effects. The aim of this study was to examine any long-term neuroprotection by doxycycline treatment on cerebral gray and white matter. Hypoxic-ischemic brain injury was induced in 7-day-old rats. Pups were treated with either doxycycline (HI+doxy) or saline (HI+vehicle) by intraperitoneal injection at 1 h after hypoxia-ischemia (HI). At 6 h after HI, MnCl(2) was injected intraperitoneally for later manganese-enhanced magnetic resonance imaging (MRI). MRI was performed with diffusion-weighted imaging on day 1 and T(1) -weighted imaging and diffusion tensor imaging at 7, 21 and 42 days after HI. Animals were killed after MRI on day 42 and histological examinations of the brains were performed. There was a tendency towards lower lesion volumes on diffusion maps among HI+doxy than HI+vehicle rats at 1 day after HI. Volumetric MRI showed increasing differences between groups with time after HI, with less cyst formation and less cerebral tissue loss among HI+doxy than HI+vehicle pups. HI+doxy pups had less manganese enhancement on day 7 after HI, indicating reduced inflammation. HI+doxy pups had higher fractional anisotropy on diffusion tensor imaging in major white matter tracts in the injured hemisphere than HI+vehicle pups, indicating less injury to white matter and better myelination. Histological examinations supported the MRI results. Lesion size on early MRI was highly correlated with final injury measures. In conclusion, a single dose of doxycycline reduced long-term cerebral tissue loss and white matter injury after neonatal HI, with an increasing effect of treatment with time after injury.     

功能神经导航和术中磁共振引导下精确切除毗邻大脑运动功能区的致(癎)病变

目的 评估功能神经导航和术中MRI引导对毗邻运动功能区致(癎)病变切除术的效果.方法 回顾性分析接受神经导航引导手术的14例癫(癎)病人,其中10例采用术中MRI.术前MRI扫描,融合影像,设计病变切除范围及入路,三维计划输入导航系统并投射至手术显微镜辅助手术.术中复查MRI,对残余病变重新定位,实施手术切除.术后定期进行随访.结果 病人均成功实施了功能神经导航,致(癎)病变、运动区皮质和锥体束投射在手术显微镜下,精确切除病变,同时运动区皮质和锥体束获得有效保护;术中MRI末次扫描提示致(癎)灶病变的切除范围达到术前计划.术后随访6～24个月,癫(癎)发作控制达Engel Ⅰ级12例,Engel Ⅱ级2例.未出现肢体肌力下降.结论 对于毗邻运动功能区的致(癎)病变,通过功能神经导航和术中MRI精准定位病灶和功能区,可以达到精准切除病变并保护正常脑功能的目的.     

低血糖脑病的临床及脑部磁共振特征

目的探讨低血糖脑病的临床及脑部磁共振特征。方法回顾分析69例低血糖昏迷患者的临床、脑磁共振（MRI）成像资料。结果低血糖昏迷诱因较为复杂,常见的为进食减少、腹泻、上呼吸道感染、降糖药物应用不当等。临床表现复杂多样,除意识障碍外,还可表现为偏瘫、四肢瘫、凝视麻痹等,多数伴有Babinski征。69例患者中有18例出现脑MRIDWI异常高信号病灶,病灶主要累及海马、基底节、大脑皮质以及皮质下白质,多为对称性损害。3个月后随访,不伴有脑部MRI损害的患者预后良好率明显高于伴有脑部MRI损害的患者（94．12％对22．22％;P=0．0011）。伴有脑部MRI损害者有10例患者预后不良,其中9例（90％）发生于皮质受累患者。结论低血糖脑病临床表现不具有特异性,对于昏迷患者,应当考虑到低血糖的可能。降糖药物应用不当为低血糖脑病的主要诱发因素。脑部MRI要优于脑部CT检查,其中DWI序列对于检测低血糖所致的脑部损害有着非常重要的意义。皮质受累者预后不良。     

Performing functional magnetic resonance imaging in patients with Parkinson's disease treated with deep brain stimulation.

Deep brain stimulation (DBS) is a relatively novel treatment in advanced Parkinson's disease (PD). Functional magnetic resonance imaging (fMRI) is a useful technique for examining the effects of DBS both within the basal ganglia and its cortical connectivity. There are technical difficulties in imaging patients with PD, and the DBS itself can generate image artifacts. We describe aspects related to optimizing the fMRI acquisition parameters in patients with DBS and the results of sensorimotor activation tasks performed by four PD patients during hand, foot, and tongue movements, both before and after DBS implant. Provided that all safety conditions are followed, it is possible to perform fMRI in patients with PD and DBS. The standard DBS surgical procedure has to be slightly modified in order to reduce image artifacts. The event-related design provided increased power to detect sensorimotor cortex and basal ganglia activation.     

T2-weighted magnetic resonance imaging of cerebrovascular reactivity in rat reversible focal cerebral ischemia

Cerebrovascular carbon dioxide (CO₂) reactivity is an important hemodynamic index in cerebrovascular disease. In the present study T2^*-weighted magnetic resonance image (T2^*WI) was evaluated as a non-invasive method to investigate changes in CO₂ reactivity. Fourteen rats were subjected to permanent or, 30 and 90 min of temporary middle cerebral artery occlusion. A series of T2^*WIs and diffusion-weighted magnetic resonance images (DWI) was performed hourly under normo- and hypercapnic conditions. Triphenyltetrazolium chloride (TTC) staining of brain sections was obtained at the end of experiment to evaluate ischemic damage. During ischemia, a 4–6% signal increase upon hypercapnia was observed on T2^*WI in the non-ischemic hemisphere, while no such reactivity was seen in the putamen and cortex ipsilateral to the MCA occlusion. After reperfusion, CO₂ reactivity recovered in the putamen and cortex in the 30 min ischemia group and in the cortex alone of the 90 min ischemia groups. The areas with irreversible CO₂ reactivity dysfunction coincidentally revealed no recovery on DWI and lack of TTC staining. The results indicate that T2^*WI can be used to monitor changes in CO₂ reactivity after various ischemic insults that may indicate tissue viability.     

Magnetic resonance imaging, Down's syndrome and Alzheimer's disease: research and clinical implications

Background The diagnosis of Alzheimer's disease (AD) remains at times difficult to make using available neuropsychological measures. Neuro‐imaging is a relatively new form of detecting the changes associated with dementia. The present study investigated the role of magnetic resonance imaging (MRI) in diagnosing AD in adults with Down's syndrome (DS). Methods Subjects with DS and Alzheimer‐type dementia were matched to non‐demented controls with DS. Magnetic resonance imaging findings (i.e. volumetric and two‐dimensional scans) were compared between the two groups in order to show a relationship between the changes of AD and structural MRI abnormalities. Results Specific structural abnormalities which are seen in non‐intellectually disabled subjects with dementia are also found in individuals with both DS and AD. However, such findings cannot be used to diagnose clinical AD with good accuracy in adults with DS. A number of practical issues of patient compliance and over‐sedation are demonstrated by the findings. Conclusions Magnetic resonance imaging has an important but limited role to play in the management of AD in the population with DS. If intravenous sedation is used, medical support is essential to prevent a serious mishap.     

Magnetic resonance imaging and computed tomography in Alzheimer's disease

Structural neuroimaging with CT and MRI plays an important role in the routine clinical investigation of dementia patients. One major purpouse of the technique is to exclude secondary, treatable dementia disorders. In this respect these techniques are of utmost importance. Another major purpose of these techniques is to differentiate AD from healthy controls and other dementias.
Although some research groups have reported a high sensitivity and specificity for diagnosing AD by measuring the volumes (with MRI) of structures in the temporal lobes, there are no unequivocal "radiological" markers (such as the size of the lateral ventricles or sulci) that can differentiate AD from controls or vascular dementia. There have been a large number of CT and MRI studies showing that the volumes of the temporal lobes or part of the temporal lobes, such as the hippocampal formation are reduced in AD, as compared to healthy subjects.
The role of white matter changes (WMH, leukoaraiosis) in the development of AD or as a diagnostic marker for AD is unclear. The degree of WMH has been shown to be strongly age dependent and there are contradictory data concerning its relation to cognitive decline. There is stronger agreement concerning the relationship between LA assessed with CT and cognitive functions than there is between WMH on MRI and cognitive functions.
Correlative studies with MRI, CT and SPECT or PET are few. Usually the sensitivity and specificity of diagnosing AD can be increased by combining two or more modalities. One other goal with this approach is to use one structural modality, such as MRI or CT as a template for functional images in order to obtain a higher accuracy in measurement of blood perfusion or glucose metabolism.     

The characterization of human brain tumor using magnetization transfer technique in magnetic resonance imaging

Abstract

The clinical applicabiity of magnetization transfer (MT) technique in magnetic resonance imaging (MRI) for the estimation of the histological and constitutional feature of brain tumors was investigated. MT effect was evaluated by measuring the MT ratio (MTR). The parameters in 1.5-tesla MRI system were as follows: TR, 50 msec; TE, 5 msec; flip angle, 30 degree; offset frequency of off-resonance MT pulse, 1000 Hz. The sequence was performed in 20 normal volunteers and 45 patients with brain tumors which were characterized histologically and surgically. The MTR for brain tumors was significantly lower than that for normal brain tissue (p < 0.05). The MTR for meningioma was higher than that for the other brain tumors (p < 0.05). In the meningiomas, MTR for fibrous type was higher than that for méningothélial type, but there was no statistical significance. Regarding the physical consistency for the brain tumors, as classified by surgery, there was a statistically significant difference in MTR between the soft tumor group (0.22 ± 0.03, n = 6) and the hard tumor group (0.36±0.04, n=10) (p < 0.01). This study suggested that the MT technique for patients with brain tumor may be useful to understand the characteristics of the tumors presurgically, based on the degree of intermolecular interaction of macromolecule such as protein. [Neurol Res 1999; 21: 250-254]