Application Of Diffusion And Perfusion Weighted Imaging In Study Of Transient Ischemic Attack

Partâ… Transient Ischemic Attack and minor Stroke Can Be Differentiated by Analyzing Diffusion-Weighted Imaging Signal Intensity Changes Purpose:Diffusion-weighted imaging(DWI) has been established to diagnose acute cerebral ischemia.Signal intensity changes occur not only in patients with definite stroke but also in up to 67%of transient ischemic attack(TIA) patients.We investigated the predictive value of DWI signal intensity and apparent diffusion coefficient(ADC) value changes to distinguish between TIA and minor stroke.Methods:Clinical data,conventional magnetic resonance imaging(MRI),DWI were collected in 45 consecutive patients with TIA and 33 consecutive patients with minor stroke.DWI was performed within 24 hours after symptom onset.Using an image analyzing system,we calculated the ratio of the lesion and corresponding contralateral normal tissue average signal intensity(rAI_{b =1000}) and average ADC value(rAI_ADC).Results:22 of 45 TIA patients(49%) revealed focal abnormalities on DWI.The mean duration of symptoms was 44.5 mins in TIA patients with DWI lesions and 40.5 mins in patients without lesions.The time to DWI was comparable in TIA and minor stroke patients.The signal intensity was significantly higher(P＜0.05) in minor stroke patients(n=33,rAI_b=1000=1.96) as compared with TIA patients with DWI lesions(n=22,rAI_b=1000=1.46).The ADC value was significantly lower (P＜0.05) in minor stroke patients(n=33,rAI_b=1000=0.69) as compared with TIA patients with DWI lesions(n=22,rAI_b=1000=0.87).Conclusions:Our data indicate that TIA and minor stroke might be differentiated by analyzing the signal intensity and ADC value of the lesions.Partâ…¡Application of Diffusion Tensor Imaging in Transient Ischemic AttackPurpose:Diffusion tensor imaging(DTI) permits the quantitative evaluation of white matter pathology using measures of diffusion anisotropy.FA may be important in detection of wallerian degeneration that may be important in determining prognosis.Signal intensity changes occur not only in patients with definite stroke but also in up to 67%of transient ischemic attack(TIA) patients.We investigated the predictive value of rAI_FA value changes and 3D fiber trcatography in revealing corticospinal tract(CST) injury to distinguish between TIA and minor stroke.Methods:Clinical data,conventional magnetic resonance imaging (MRI),diffusion weighted imaging(DWI)and diffusion tensor imaging(DTI) were collected in 45 consecutive patients with TIA and 33 consecutive patients with stroke.DWI and DTI were performed within 24 hours after symptom onset.All raw data were reconstructed using Functool 2 software, Three seeds were used to reconstruct the corticospinal tract.Using an image analyzing system,we calculated the ratio of the lesion and corresponding contralateral normal tissue FA value(rAI_FA).The spatial relationship between lesion and CST were analyzed and the lesion size between minor stroke and TIA patients were compared.Results:22 of 45 TIA patients(49%) revealed focal abnormalities on DWI and DTI.The FA value was significantly lower(P＜0.05) in stroke patients(0.71±0.29) as compared with TIA patients with DWI lesions(0.93±0.40).We also found most stroke lesions were in relation to functionally important pathways,while most TIA lesions were not.Conclusions:Our data indicate that TIA and minor stroke might be differentiated by analyzing the rAI_FA value of the lesions,which may allow more accurate prognosis of long-term recovery or disability.DTI can quantify differences in the responses of gray versus white matter to ischemia.Partâ…¢Assesement of Transient Ischemic Attack Patients using combined diffusion-and perfusion-weighted imagingPurpose:Abnormalities in diffusion-weighted(DWI) and perfusion-weighted(PWI) magnetic resonance imaging(MRI) changes occur not only in patients with definite stroke but also in transient ischemic attack(TIA) patients.No studies have examined classification of TIA for assessment of the ischemic degree(＜24h from symptom onset).Methods: This is a prospective study of 41 patients admitted with a diagnosis of TIA performed with DWI and PWI studies within 1 day of onset of symptoms and within 7-14 days and 1-3 months follow-up.Values of CBV and MTT were measured in the abnormal region and the normal contralateral region in white matter at each time point and the ratio of abnormal regions to control regions of interest were calculated.Data were expressed as relative CBV and MTT.Relative CBF is get by rCBV/rMTT.Results:Patients with abnormal PWI were more likely to have coronary artery disease(P =.032) andhyperlipidemia(P=.045) than the rest of the patients.There was no difference in the prevalence of cardiovascular risk factors between patients with abnormal PWI as compared with those with unremarkable scan.Hemiparesis was significantly associated with abnormal PWI.However, other neurologic symptoms were not predictive of MR imaging abnormalities. The duration of transient neurologic dysfunction did not differ between patients with abnormal PWI imaging when compared with those patients with unremarkable scan.MR imaging was abnormal in 28 patients(68%):15 had abnormal DW imaging,7 had both DW and PW imaging defects and 6 had an isolated PW imaging abnormality.After follow-up 4 of 22(9.8%)with high intensity on DWI showed normal intensity onDWI and T2WI:5 of 19(12.2 %) with normal DWI progressed to stroke.We hypothesized that DWI(-) patients with DWI(-) after follow-up and DWI(+) patients with DWI (-) after follow-up mostly showed hypo-perfusion on white matter of the symphtomside,while DWI(-) patients with DWI(+) after follow-up and DWI(+) patients with DWI(+) after follow-up mostly showed hyper-perfusion on white matter of the symphtom side.Conclusions:DWI and PWI can be used for classifications of TIA.The classifications may be helpful to assess the ischemic degree for treatment and prognosis of TIA patients.Partâ…£Metabolic Changes in Transient Ischemic Attack Patients and Their Correlation with perfusion-weighted imagingPurpose:We investigated whether patients with transient ischemic attack (TIA) have metabolic changes in the brain.Methods:35 patients with clinically diagnosed TIA were prospectively included in our study. Clinical and neurological data were compiled.¹H-MR spectroscopy was performed in all patients within 3 days and PWI within 1 day of onset of symptoms.Results:In TIA patients,the N-acetylaspartate(NAA)/choline ratio in noninfarcted regions was significantly decreased in the symptomatic hemisphere(1.33±0.38) compared with the asymptomatic hemisphere(1.51±0.41,P＜0.05).Patients with a history of prior TIA had a significantly decreased NAA/choline ratio in both the symptomatic (P＜0.05) and asymptomatic(P＜0.05) hemispheres compared with TIA patients without a prior TIA.TIA patients with DWI lesions had a significantly increased lactate/NAA ratio in both the symptomatic(P＜0.05) and asymptomatic(P＜0.05) hemispheres compared with TIA patients without lesions,rCBF value was directly related to the symptomatic Cho/Cr value. (r=0.81,p＜0.01).The higher the rCBF value is,the higher the symptomatic Cho/Cr value.Conclusions:TIA patients have neurological deficits that are transient;however,metabolic damage to the brain is present up to 3 days after the onset of the symptoms.These metabolic changes are not restricted to the symptomatic hemisphere or to areas close to ischemic lesions and the changes are related to the cerebral blood flow.