| Objective:1.To evaluate which of T1-weighted technique between fast spoiled GRE (FSPGR) and Fast-Spine echo (FSE) sequence is more sensitive to low concentration of Mncl2 solution. A serial of aqueous Mncl2 phantoms were studied.2.To compare Mncl2 solution signal enhancement in five rats olfactory bu1b (OB) between FSPGR-T1WI and FSE-T1WI sequence.3.To determine if Mn2+ is transport with transcallosally cross hemispheres between the motor cortex.Material and method:1.Mncl2 was diluted with saline to obtain 8 solution with different concentration (salina solution,0.1 uM,1 uM,1 OuM,0.1 mM,1 mM,10mM, 0.1M Mncl2 solution).The solution were imaged in test tube of 10mm internal diameter and 10ml in volume, arrange in alterning high and low concentration. T1WI images of each phantom were aquired at room temperature (approximately 21℃) using two clinically available pulse sequence (FSE and FSPGR). Magnetic response imaging was performed on a 3.0T whole human body scanner (Signa EXCIT HD GE healthcare USA).A standard quadrature birdcage head coil was used for the imaging of phantoms.Circular RoIs with 70-80% of diameter of test tube were placed on a uniform signal portion of each phantom. Mean signal intensity were calculated from each ROI.Each sequence relative signal intensity change (ΔSI) were calculated asΔSI= SItest-SIsaline/SIsaline×100%. Where SItest is the signal intensity of each solution and SIsaline is the signal intensity of saline solution.2.To trace the neuronal conections into the olfactory pathway,20ul of 0.5M MnCL2 aqueous solution was injected right nostril of a rat (N=5). T1-weighted were acquired by FSPGR sequence and FSE sequence. Magnetic response imaging was performed on a 3.0T whole human body scanner (Signa EXCIT HD GE healthcare USA).Imaging acquired from the same animal at before injection and 3h,4h,5h,6h,12h,24h,36h and 48h post injection.Region of interest(ROIs)were drawn on the olfactory bulb (OB) according to the rat brain atlas using Pax i no. The ROI for the OB was drawn in the anterior part of the bulb, which is close to where Mn2+ gets in the intranasal injection experiment. Signal intensities in ROI 10-30mm3 were measured using ADW4.3 software (GE 3.0T Signa EXCIT HD GE healthcare USA).To average and compare data from different animals. Reginal signal noise ratio (SNR) were used.Regional SNR was calculated by dividing the mean signal in ROI by standard deviation in noise region outside the head. Befor injection and post-injection multiple comparison using student's paired t test were done to access the statistical significant of MRI signal changes. Repeated measurements were performed to assess significance means of SNR between FSPGR-T1WI and FSE-T1WI sequence.A value of P<0.05 was considerated significant. Statistical calculations were performed using spss 13.0 version.2.5 adult Sprague-Dawley(SD) rats were used in this study. For cortical injections,5 rats received pressure injection of luL of 0.8M aqueous MnCL2.All stereotactic coordinates were determined according to the paxinos and waston atlas. For stereotactic injection,rats were initially anesthetized by 3% pentobarbital sodium, positioned in a stereotactic frame.A small bur hole was drilled after exposing the skull. A syring was placed at the proper coordinates in the stereotactic frame.Injections were performed slowly over 5-10mm and the syringe was slowly removed. The burr was sealed with bone wax and muscle sutured closed.T1-weighted images were acquired by FSPGRT1WI sequence and FSET1WI sequence. Magnetic response imaging was performed on a 3.0T whole human body scanner (Signa EXCIT HD GE healthcare USA). MRI was performed before injection and 8h,24h, 48h,72h post injection.Region of interest (ROI) analysis was performed on FSPGR images according to the rat brain atlas.ROIs were drawn in a portion of cortical corresponding the left somatosensory cortex (SI) and contralateral somatosensory cortex. Signal intensities in ROI 10-30mm3 were measured using ADW4.3 software (GE 3.0T Signa EXCIT HD GE healthcare USA).Average signal intensity value were get at different rat and different time point from FSPGR-T1WI sequence data.Reginal signal noise ratio (SNR) were used. Regional SNR was calculated by dividing the mean signal in ROI by standard deviation in noise region outside the head.Befor injection and post-injection multiple comparison using student's paired t test were done to access the statistical significant of MRI signal changes. Repeated measurements were performed to assess significance means of SNR between left somatosensory cortex (SI) and contralateral somatosensory cortex,a value of (P< 0.05) was considerated significant. Statistical calculations were performed using spss 13.0 version.Result:1.The similar trends of signal intensity change in the different concentration Mncl2 solutions with FSE-T1WI and FSPGR-TIWI sequence.In 0.1M Mncl2 solution,ΔSI is negative value because of extensive signal loss due to T2 decay. Mncl2 solutions rang from 1uM to 10mM,ΔSI for FSPGR-T1WI sequence is higher than FSE-T1WI sequence.2.The time at which Mn2+ signal enhancement was seen in olfactory pathway was to some extent related to the distance from injection site. In our study distance signal enhancement was seen after intranasal injection 3h in lfactory nerve,after 6h in the OB and after 24h in the olfactory center.The repeated measures showed significant difference (P<0.05) for SNR between FSPGR-T1WI sequence and FSE-T1WI sequence after intranasal injection 6h.SNR for FSPGRTiWI was significant higher than FSE-T1WI sequence after intranasal injection 6h.The similar trends of signal increase in OB between FSPGR-T1WI sequence and FSE-TIWI sequence.3. Mncl2 was injected in cortical M2 region when the animal were scanned after injection 8h, the injection site were visible as bright region in T1-weighted images.The high signal intensity region surrounding the point of injection typically had a radius of 6mm after injection 8h, increasing to 9mm after 48-72h.In the center of the injection, we often observed low signal intensity,associated with high concentration of Mn2+. Mn2+ signal enhancement was visible in the corpus callosum after injection 8h. After 8h distinct intracortical signal enhancement could be seen in the ipsilateral secondary motor cortex (M2) and contralateral M2, as well as in the other cortical sites.Signal enhancement was observed in the ipsilateral thalamus,internal capsule, cerebral peduncle, corticospinal pathways and contralateral internal capsule after injection 8h,in these regions was seen the intensity values gradully increased. The similar trends of signal intensity increase between ipsilateral motor cortex and contralateral motor cortex. The repeated measures showed significant difference (P<0.05) for SNR between ipsilateral motor cortex and contralateral motor cortex after injection 8h.SNR for ipsilateral motor cortex was significant higher than contralateral motor cortex after injection 8h.Conclusion:1. FSPGR-T1WI sequence is more sensitive than FSE-T1WI sequence to low concentration Mncl2 solution.2. FSPGR-T1WI sequence is more superior than the FSE-T1WIsequence in its ability to delineate OB of rat after intranasal injection 6h.3. It was found that differences in maximal intensity due to Mn2+ accumulation through depths of the cortex are specifi to particular neural input pathway to layer of M2 contex.The layer specificity of MEMRI neuronal track tracing has great potential for identifying changes in neuronal connectivity in vivo that may occur in learning, plastic, brain development, or certain disease states such as stoke or peripheral never injury. Objective:We use FA to characterizeWM tracts adjacent to brain tumor in an effort to determine preoperatively whether a specific tract is viable or should be resected during surgery.Material and method:A total of 23 patients with brain lesions were evaluated.Among these 23 patients, a total of 43 tracts had potentially abnormal WM tracts identified adjacent to a lesion, and these WM tracts were compared to WM tracts in the contralateral hemisphere, which were assumed to be normal. Because all patients underwent a routine preoperative MR examination, which included T1- and T2-weighted sequences and DTI sequence. We identified individual WM tracts using directionally encoded color maps. Hues in the color map represent tensor direction, whereas grayscale intensity represents the integrity of WM tracts. The location of individual WM tracts was identified by reference to a pictorial review based on cadaveric dissections. White matter tract involvement was categorized as edema, infiltration, displacement, or disruption. According to the method of Witwer et al, WM tracts were characterized as displaced if they maintained normal anisotropy relative to the corresponding tract in the contralateral hemisphere but were situated in an abnormal location or with an abnormal orientation on color-coded orientation maps,edematous if they maintained normal anisotropy and orientation but demonstrated high signal intensity on T2-weighted MR images, infiltrated if they showed reduced anisotropy but remained identifiable on Categorization was based on the 3-dimensional appearance of the tract and on pathology of the resected tumor tissue. Meningioma was defined as noninfiltrative. Fractional anisotropy was then measured in every WM tract adjacent to tumor, as well as in the corresponding WM tract in the contralateral hemisphere. A ROI was drawn manually on the 2-dimensional image using adw4.3 software. Statistical analysis:the FA from lesioned and normal hemispheres was expressed as mean±SD. A mixed model analysis was used, corrected for repeated measures with the LSD method. Statistical calculations were performed using spss 13.0 version with a significance level of 0.05.Result: The WM tracts of 23 patients with WHO-graded brain tumors were evaluated, including 8 patients with meningioma WHOⅠgrade.3 with brain metastases.5 with WHOⅡgrade glioma.7 patients with WHOⅢ-Ⅳgrade. A total of 43 tracts near a lesion were compared to the contralateral (normal) hemisphere; therefore,86 tracts were evaluated. By category, there were 16 corticospinal tracts involved,12 WM tracts in the frontal lobe,6 in the temporal lobe,5 inthe optic radiation, and 4 bulbar tracts. Grouping the tracts qualitatively, there were 5 WM tracts with edema,9 with infiltration,18 with displacement, and 11 with disruption. We compared the FA value of WM pairs using a mixed model approach to compensate for repeated measurements. A significant FA was noted only for WM disruption.Conclusions:1.Quantitative analysis of DTI data may provide insight as to whether WM tracts are salvageable preoperatively.2.The brain tumor and surrounding white matter fiber tracts were showed by DTI and DTT technology in vivio in a clear and intuitive, non-invasive way. DTI and DTT technology provide an important basis to determine preoperative treatment program for brain tumor. |
PDF Full Text Request