功能磁共振和弥散张量纤维束成像中的人脑皮质桥小脑束

The anatomical organization of the corticopontocerebellar tract(CPCT) in the human brain remains poorly understood.The present study investigated probabilistic tractography of the CPCT in the human brain using diffusion tensor tractography with functional magnetic resonance imaging.CPCT data was obtained from 14 healthy subjects.CPCT images were obtained from functional magnetic resonance imaging and diffusion tensor tractography,revealing that the CPCT originated from the primary sensorimotor cortex and descended to the pontine nucleus through the corona radiata,the posterior limb of the internal capsule,and the cerebral peduncle.After crossing the pons through the transverse pontine fibers,the CPCT entered the cerebellum via the middle cerebral peduncle.However,some variation was detected in the midbrain(middle cerebral peduncle and/or medial lemniscus) and pons(ventral and/or dorsal transverse pontine fibers).The CPCT was analyzed in 3 dimensions from the cerebral cortex to the cerebellum.These results could be informative for future studies of motor control in the human brain.     

双侧脑桥出血后双侧皮质脊髓束压迫的弥散张量纤维束成像验证

Bilateral spontaneous pontine hemorrhage is rare.In addition,bilateral corticospinal tract(CST) involvement in the pons may accompany serious motor sequelae.A 45-year-old right-handed woman was admitted for bilateral pontine hemorrhage.The patient presented with moderate quadriparesis at stroke onset and quickly recovered to the point of being able to extend the muscles of all four extremities against resistance,at 2 weeks from onset.At 4 weeks after stroke onset,she was able to perform all fine motor activities,as well as to walk with a normal gait.Diffusion tensor tractography results showed that the CSTs of both hemispheres originated from the primary sensorimotor cortex and descended through the corona radiata,the posterior limb of the internal capsule,midbrain,anterior pons,and the anterior medulla,along the known pathway of the CST.However,at midbrain and pons,the CSTs were compressed posterolaterally.The contralateral primary sensorimotor cortex,centered on the precentral knob,was activated during movement of either hand of the patient,as shown by functional MRI,which indicates the preservation of lateral CST.Findings from this study suggest that diffusion tensor tractography may be helpful in the elucidation of the CST status in patients with pontine hemorrhage.     

弥散张量纤维束成像和经颅磁刺激显现脑出血患者独立的皮质脊髓束

Diffusion tensor tractography allows visualization of the corticospinal tract (CST) in three dimensions. Transcranial magnetic stimulation offers a unique advantage in that it can distinguish between the corticospinal tract and the non-CST by analyzing the characteristics of a motor-evoked potential. A 15 year-old female showed right hemiparesis, due to intracerebral hemorrhage in the left corona radiata, and the posterior limb of the internal capsule. Diffusion tensor tractography revealed that the tracts of both hemispheres originated from the precentral gyrus, and descended through the known CST pathway. Specifically, the tract of the affected hemisphere descended through an isolated area in the leukomalactic lesion at the posterior limb level. In addition, the characteristics of the motor-evoked potential obtained from the right hand when stimulating the hot spot of the left motor cortex corresponded to a CST. In conclusion, we report on a patient with intracerebral hemorrhage who showed an isolated CST in a leukomalactic lesion. This result suggests the importance of saving the adjacent area or penumbra around a hematoma after an intracerebral hemorrhage.     

延髓锥体梗死患者运动功能恢复与皮质脊髓束穿行于梗死延髓锥体的小块空余区

The present study reported a 58-year-old male patient who exhibited complete paralysis of the right extremities at stroke onset.Brain MR images showed an infarct in the left medullary pyramid and a small spared area on the medial side of the infarct.He gained the ability to extend the affected fingers against gravity and to dorsiflex the affected ankle without gravity at 3 months after stroke onset.Diffusion tensor imaging results showed that at 6 months after stroke onset,the corticospinal tract of the affected(left) hemisphere descended through the small spared area of the infarcted medullary pyramid.No motor-evoked potential was elicited from the affected(left) hemisphere at 2 weeks after stroke onset;however,motor-evoked potential was elicited at 6 months as shown by transcranial magnetic stimulation results.The motor function of the affected side of this patient appears to have been recovered via the corticospinal tract that passed through the small spared area within the infarcted medullary pyramid.     

Magnetic resonance diffusion tensor imaging-based evaluation of optic-radiation shape and position in meningioma

Employing magnetic resonance diffusion tensor imaging, three-dimensional white-matter imaging and conventional magnetic resonance imaging can demonstrate the tumor parenchyma, peritumoral edema and compression on surrounding brain tissue. A color-coded tensor map and three-dimensional tracer diagram were applied to clearly display the optic-radiation location, course and damage. Results showed that the altered anisotropy values of meningioma patients corresponded with optic-radiation shape, size and position on both sides. Experimental findings indicate that the magnetic resonance diffusion tensor imaging technique is a means of tracing and clearly visualizing the optic radiation.     

健康人双大脑脚各向异性值及面积：弥散张量成像研究

Diffusion tensor imaging was performed in 105 volunteers free of central nervous system lesions.No differences were found in fractional anisotropy between the left and right cerebral peduncles among subjects(P > 0.05).The lower limit value of fractional anisotropy was 0.36,and the asymmetry ratio was 0.77.The area and lower limit value of the cerebral peduncles were 0.90 cm2 and 0.83,respectively.These results will be useful in evaluating the diagnosis of Wallerian degeneration following cerebral infarction.     

内囊后肢梗死患者皮质脊髓束的重组

Several diffusion tensor-imaging studies have demonstrated motor recovery mechanisms in stroke patients with subcortical infarct,including the corona radiata,pons,and medulla.However,studies of motor recovery mechanisms have not been reported in patients with posterior limb infarcts of the internal capsule.The present study reports on a 77-year-old man with complete paralysis of the left extremities at stroke onset.At 6 months after onset,motor function of the left extremities recovered to a nearly normal state.The 3-week diffusion tensor tractography of the affected(right) hemisphere showed that corticospinal tract discontinued below the posterior limb.In contrast,6-month diffusion tensor tractography revealed that the right corticospinal tract originated from the precentral gyrus and descended along the anterior area of the infarcted posterior limb.Motor function of the affected extremities was reorganized into the anterior area of the posterior limb infarct.     

Magnetic resonance imaging markers for early diagnosis of Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by selective and progressive degeneration, as well as loss of dopaminergic neurons in the substantia nigra. In PD, approximately 60-70% of nigrostriatal neurons are degenerated and 80% of content of the striatal dopamine is reduced before the diagnosis can be established according to widely accepted clinical diagnostic criteria. This condition describes a stage of disease called "prodromal", where non-motor symptoms, such as olfactory dysfunction, constipation, rapid eye movement behaviour disorder, depression, precede motor sign of PD. Detection of prodromal phase of PD is becoming an important goal for determining the prognosis and choosing a suitable treatment strategy. In this review, we present some non-invasive instrumental approaches that could be useful to identify patients in the prodromal phase of PD or in an early clinical phase, when the first motor symptoms begin to be apparent. Conventional magnetic resonance imaging (MRI) and advanced MRI techniques, such as magnetic resonance spectroscopy imaging, diffusion-weighted and diffusion tensor imaging and functional MRI, are useful to differentiate early PD with initial motor symptoms from atypical parkinsonian disorders, thus, making easier early diagnosis. Functional MRI and diffusion tensor imaging techniques can show abnormalities in the olfactory system in prodromal PD.     

弥散张量成像定位初级运动功能区的研究

目的 探讨弥散张量成像在定位初级运动功能区的价值.方法 20例脑深部肿瘤患者,分别进行常规MRI、fMRI及DTI检查,获取fMRI脑激活图、DTI图、3D解剖图.DTI通过三维重建皮质脊髓束定位初级运动功能区.fMRI采用手握拳激发模式,获取激活信号定位初级运动功能区.比较两种技术的吻合度,以评价DTI三维重建皮质脊髓束定位的初级运动功能区的准确性.结果 20例患者fMRI获得的激活信号主要位于对侧中央沟处,围绕着"Ω"形柄状结构分布,中央前回位于激活信号前方.所有患者均成功地完成DTI皮质脊髓束的三维重建,重建的皮质脊髓束也定位于激活信号前的脑回,两者均较好显示初级运动功能区且具有较好的一致性.结论 DTI可较好地定位初级运动功能区,这对于有肢体瘫痪患者及不能合作的儿童的初级运动功能区的定位有重要意义.     

基于多梯度方向脑神经扩散张量成像的质量评价

Diffusion tensor MRI(DT-MRI or DTI) is emerging as an important non-invasive technology for elucidating internal brain structures.It has recently been utilized to diagnose a series of diseases that affect the integrity of neural systems to provide a basis for neuroregenerative studies.Results from the present study suggested that neural tissue is reconstructed with multiple diffusion-weighted gradient directions DTI,which varies from traditional imaging methods that utilize 6 gradient directions.Simultaneously,the diffusion tensor matrix is obtained by multiple linear regressions from an equation of echo signal intensity.The condition number value and standard deviation of fractional anisotropy for each scheme can be used to evaluate image quality.Results demonstrated that increasing gradient direction to some extent resulted in improved effects.Therefore,the traditional 6 and 15 directions should not be considered optimal scan protocols for clinical DTI application.In a scheme with 20 directions,the condition number and standard deviation of fractional anisotropy of the encoding gradients matrix were significantly reduced,and resulted in more clearly and accurately displayed neural tissue.Results demonstrated that the scheme with 20 diffusion gradient directions provided better accuracy of structural renderings and could be an optimal scan protocol for clinical DTI application.     

Characters of MR diffusion tensor imaging in cerebral ischemic corticospinal tract injury

BACKGROUND: Diffusion tensor imaging (DTI) is one of the noninvasive methods to study the morphological structure of brain white matter fibrous bands in vivo, and it has been applied primarily in clinic. DTI is acknowledged as the more effective imaging method to diagnose ultra-acute and/or acute cerebral infarction. OBJECTIVE: To observe the anisotropic characters of cerebral white matter fibrous bands in patients with ischemic stroke by using DTI, and investigate the correlation between the damage of corticospinal tract and muscle strength in patients with ischemic stroke at acute period. DESIGN: A case-control observation. SETTING: Department of Medical Imaging, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA. PARTICIPANTS: Nine inpatients with injury of motor function induced by acute ischemic stroke (patient group) at 6 hours to 2 weeks after the attack were selected from the Department of Neurology, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA from September 2005 to March 2006, and they all accorded with the present diagnostic standard for cerebrovascular disease in China. There were 5 males and 4 females, aged 16-87 years. At the same time, nine healthy right-handed physical examinees matched by age and sex with the patients were taken as the control group, and they all had no nervous disease, mental diseases, cerebrovascular abnormalities and injury history, etc. All the subjects were informed with the detected items and agreed to participate in the study. METHODS: All the 9 patients with ischemic stroke at acute period and 9 healthy subjects were examined with MRI, T1 weighted imaging, T2 weighted imaging and DTI. And the data were processed offline with dTV.II software, the images of fractional anisotropy and directional encoded color (DEC) were obtained, and the three-dimensional fibrous band images of bilateral corticospinal tracts were reconstructed. In the control group, the values of fractional anisotropy of main white matter fibrous bands were measured in the region of interest (ROI) of the anterior limb, knee and posterior limb of internal capsule. In the patient group, the values of fractional anisotropy of white matter were measured in the infarcted sites and corresponding contralateral sites of the patients. The ROI was set in bilateral cerebral peduncles to reconstruct three-dimensionally the bilateral corticospinal tracts. The muscle strength of the affected hand was assessed with Brunnstorm standard in the stroke patients. MAIN OUTCOME MEASURES: The characters of DTI and images of the value of fractional anisotropy, and the manifestations of three-dimensional corticospinal tracts were observed in the two groups. RESULTS: All the data from the 9 patients and 9 healthy volunteers were involved in the analysis of results. ① In the control group, the white matter and gray matter could be distinguished clearly in the image of fractional anisotropic values, the fibers of different directions were shown by different colors in DEC picture, which clearly demonstrated the normal anatomic structure and direction of white matter fibers. In the patient group, the infarctions occurred in the gray matter or white matter could be distinguished in the images of fractional anisotropic values, DEC picture could clearly show the direct influence of the infarcted site on the white matter fibers. The fractional anisotropic values in different white matter structure of the same side were significantly different in the control group (t =3.12, P < 0.05), and the reconstructed images fractional anisotropic values and DEC picture could show most of the main white matter fibrous bands. The fractional anisotropic values of the infarcted sites were significantly lower than the contralateral ones in the patient group (t=5.570, P < 0.01). ② The reconstructed bilateral corticospinal tracts showed that the anatomic forms of the contralateral corticospinal tract of the patients were almost identical to those of normal people, it started from precentral gyrus, downward to the nternal capsule, and extended to pontine and medulla oblongata, each fibrous band was continuous, and the form had good consistency. Because of the involvement of infarction of different severity, the ipsilateral corticospinal tract manifested as continuous interruption and the loss of consistent anatomic structural form. The involved severity of corticospinal tract had significant correlation with that of muscle strength of the ipsilateral hand (r =1.30, P < 0.01). CONCLUSION: ① DTI can display the direction and distribution of cerebral white matter fibrous bands. ② DTI images of fractional anisotropic values and DEC can show the directions and anisotropic degree of white matter fibers in the infarcted sites of stroke patients. ③ The three-dimensional images of fibrous bands can show the conditions of pyramidal tracts more directly. ④ The damaged severity of corticospinal tracts is correlated with that of muscle strength.     

应用扩散张量和功能磁共振成像技术探讨皮质脊髓束与肌力的相关性

目的探讨脑梗死与脑肿瘤患者皮质脊髓束(corticospinaltract,CST)损伤对肢体肌力的影响。方法应用磁共振扩散张量成像(diffusiontensorimaging,DTI)和扩散张量纤维束成像(diffusiontensortractography,DTT)技术,并将DTI与功能磁共振成像(functionalMRimaging,fMRI)相结合,对脑梗死和脑肿瘤引起的皮质脊髓束损伤进行定位诊断,并观察皮质脊髓束损伤对患者肢体肌力的影响。对40例急性脑梗死(发病时间<72h)和113例脑肿瘤患者行MRI和扩散加权成像检查,其中部分患者再行增强扫描和fMRI检查。收集全部患者的磁共振扩散张量成像原始数据,然后行扩散张量纤维束成像,重建双侧皮质脊髓束,并将患侧皮质脊髓束的病理性改变对肢体肌力的影响进行相关性分析。结果(1)梗死区各向异性(FA)阈值为(0.336±0.065),对侧半球正常白质区FA阈值为(0.705±0.069),梗死白质区FA值显著低于健侧,两侧相比差异有显著性意义(t=15.823,P<0.001)。(2)扩散张量纤维束成像显示,脑梗死和脑肿瘤患者病变侧皮质脊髓束受压、变形、移位,部分断裂。(3)脑梗死皮质脊髓束损伤患者的肢体肌力降低率为67.50%(27/40),脑肿瘤为16.81%(19/113);组间差异有显著性意义(χ2=36.096,P<0.001)。(4)急性脑梗死和脑肿瘤累及皮质脊髓束内囊后肢致肌力降低率分别     

In vivo three-dimensional reconstruction of human median nerves by diffusion tensor imaging

The in vivo assessment of axonal projections of the peripheral nervous system has been severely limited by the lack of noninvasive techniques. We examined whether MR diffusion tensor imaging with fiber tracking of the human median nerve is feasible. The median nerve was examined with a 3-T MRI scanner in wrists of three healthy volunteers and the wrist of a patient after median nerve repair. In vivo three-dimensional (3D) reconstruction of axonal projections of the median nerve could be achieved in healthy volunteers with intact median nerves and a patient with a transected median nerve using diffusion tensor imaging combined with fiber tracking. The median nerve could be visualized and correlated well to the expected location on T1-weighted images in the patient and all volunteers. The transected median nerve in the patient could be detected up to the site of repair one month postoperatively, whereas the nerve could not be detected more distally immediately after repair. Two months postoperatively, it could clearly be tracked more distally, indicating nerve regeneration. Diffusion tensor imaging can detect the median nerve in healthy individuals as well as up to the lesion site in a patient with a complete transection of the median nerve.     

Fractional anisotropy of the corticospinal tract in normal adults Preliminary study using a diffusion tensor imaging technique

BACKGROUND: The corticospinal tract is an important tract for conducting motor function. The majority of studies focus on lesions of the corticospinal tract on appearance and function, whereas observation of normal corticospinal pathways can also improve understanding of lesion outcomes. OBJECTIVE: To observe the normal adult corticospinal tract using a diffusion tensor imaging technique to analyze fractional anisotropy (FA) in different levels of the brain. DESIGN, TIME AND SETTING: Neuroimaging observation was performed in the MRI Department, First Affiliated Hospital of Kunming Medical College in China, from October 2005 to October 2008. PARTICIPANTS: A total of 30 healthy adults were selected from the Department of MRI, First Affiliated Hospital of Kunming Medical College in China, from October 2005 to October 2008, and people with nervous system symptoms and signs were excluded. METHODS: Participants with normal conventional MRI results underwent diffusion tensor imaging examination in a 1.5 T GE MRI (slice thickness 4-5 mm, slice gap 0) for gradient data acquisition from 15 directions. The scanning involved the entire brain from the inferior medulla oblongata to the inferior cranial plate. Imaging post-processing was performed to obtain FA values; a paired Mest was applied for statistical analysis.MAIN OUTCOME MEASURES: FA values of the bilateral corticospinal tract in the medulla oblongata, pons, cerebral peduncle, basal ganglia, corona radiata, and centrum semiovale. RESULTS: FA values in the medulla oblongata and centrum semiovale were similar (P> 0.01). FA values of left corticospinal tract were significantly greater than the right side in the pons, cerebral peduncle, basal ganglia and corona radiata (P< 0.01). CONCLUSION: FA values vary by brain levels, including pons, cerebral peduncle, basal ganglia, and corona radiata. Moreover, FA values of the left corticospinal tract pathway were greater than the right side, which may relate to right handedness.     

Evaluation of corticospinal tract injury with three-dimensional diffusion tensor tract in patients with acute cerebral infarction

Three-dimensional diffusion tensor tract (DTT) is the newest imaging to describe the structure of white matter fiber in three-dimensions, it has great significance in dividing the concrete anatomic site of gray and white matter lesions, displaying the correlation with fibrous band and judging clinical prognosis, which is incomparable by other imagings.OBJECTTVE: To observe the conditions of corticospinal tract (CST) in acute cerebral ischemic stroke patients,and analyze the relationship between motor function and the severity of CST injury.DESIGN: A case-control observation.SETTTNG: Department of Medical Imaging, Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA.PARTTCTPANTS: Fifteen patients with acute cerebral infarction were selected from Fuzhou General Hospital of Nanjing Military Area Command of Chinese PLA from February to December in 2005. They all suffered from acute attack and motor disorder of hemiplegic limbs to different extent, and were conformed by CT or MRI.There were 9 males and 6 females, aging 16-87 years old, the median age was 51.7 years, and all were right handed. Fifteen right-handed normal subjects, who were matched by age and sex with the patients in the cerebral infarction group, were selected from the relatives of patients and physicians of the Imaging Department as the control group. All the subjects were informed and agreed with the study.METHODS: The patients with acute cerebral infarction and subjects in the control group received MR diffusion tensor imaging (DTI) with GE 1.5 T nuclear magnetic resonance system, fiber tracking with the software of dTV- Ⅱ. Fractional anisotropy (FA) maps and three-dimensional tractography of bilateral CST of all patients were created. Displacement, continuity and destroy of fibrous bands were observed. At the same time, muscle strength of ipsilateral hand of patients with cerebral infarction was measured with Brunnstrom standard. The correlation between the severity of CST injury and the muscle strength of ipsilateral hand was analyzed with spearman correlation analysis.MAIN OUTCOME MEASURES: ① FA values in the infarcted sites and those in the contralateral corresponding sites of patients with cerebral infarction; ② CST manifestations in the patients with cerebral infarction and the control group.RESULTS: All the 30 testees were involved in the analysis of results. ① The FA values in infarcted sites of white matter were significantly lower than those in the contralateral ones (t =4.570, P ＜ 0.001 ). ② In the control group, bilateral CST were reconstructed, they originated from precentral gyrus, went downwards to internal capsule, and extended to pontine and medulla oblongata, each fiber had good uniformity in continuous form. In the patients with cerebral infarction, the forms of contralateral CST were consistent with those in the control group with good continuity. Due to the involvement by the infarcted site to different extents, the ipsilateral CST manifested as continuous interruption and loss of uniformity in anatomic structure and form. The CST involvements were divided into three grades: integrated CST for grade I (n =2); integrated CST but compressed or displaced for grade 2 (n =5); interrupted CST for grade 3 (n =8). ③ The severity of CST injury was obviously correlated with the muscle strength of the ipsilateral hand (r=0.888, P＜ 0.05＝.CONCLUSION: ① CST is injured to different extents in patients with acute cerebral infarction, and the severity of injury is associated with muscle strength. It is indicated that it can be used to judge the prognosis of rehabilitative treatment. ②DTT can directly display the status of pyramidal tract more three-dimensionally.     

Diffusion tensor imaging for tracing the corticospinal tract

Totally three articles focusing on magnetic resonance diffusion tensor imaging and diffusion tensor imaging evaluation of ischemic and hemorrhagic stroke, deep brain tumors and healthy corticospinal tract state are published in three issues. We hope that our readers find these papers useful to their research.