Amide Proton Transfer-weighted Imaging Of Stroke At 3T:a Clinical Study On Patients With Ischemic Stroke

(Part 1)A Preliminary Research of Amide Proton Transfer Imaging in Normal Subjects and Patients with Ischemic StrokeObjective:Amide proton transfer(APT)imaging is novel type of magnetic resonance imaging(MRI)method,which has been proved to be able reflect the pH change in lesions of animal models with ischemic stroke.The purpose of this preliminary research is to investigate the feasibility of APTW MRI in the diagnosis of acute cerebral ischemia.Patients and Methods:30 subjects were enrolled,including 15 patients of acute ischemic stroke(stroke group,9 males,6 females,age ranging 44-83 years,average age 65.2±13.2 years),and 15 age-matched healthy volunteers(control group,8 males,7 females,age ranging 42-85 years,average age 61.7±11.3 years).The APT image was acquired on the transverse slice with the largest area of the lesions in stroke patients,and in control group the slice of basal ganglia was selected to acquire the APT image and detect the APT effect of the bilateral temporal lobe.The magnetic resonance ratio asymmetry(MTRasym)values,which were named APT weighted(APTW)values of the lesions were measured on APTW images,and APTW values on the contralateral side of normal appearance white matter regions was also observed.The differences of APTW values between the lesion side and contralateral normal regions in the stroke group and healthy subjects were compared with the paired t test.Results:APTW values of the infarcted side and the contralateral side in the stroke group were(-0.67±0.27)%and(0.12±0.08)%,respectively(P<0.001).In the control group,there was not significantly difference between the two normal appearance sides,and APTW values in the control group were(0.13±0.03)%and(0.14±0.06)%,respectively.Conclusions:APTW MRI can non-invasively and nonradiatively detect the existence of acute ischemic stroke,which could be potentially served as a useful tool for the clinical diagnosis and intervention in the future.(Part 2)Evolution of Cerebral Ischemia Assessed by Amide Proton Transfer-Weighted MRIObjective:Amide Proton Transfer-weighted(APTW)MRI has recently become a potentially important tool for evaluating acidosis in ischemic stroke.The purpose of this study was to evaluate the dynamic pH-related changes in the lesions in patients with ischemia.Patients and Methods:Thirty-nine patients with ischemic stroke(symptom onset to imaging time ranging 2 hours-7 days,23 males,16 females,age ranging 26-90 years,average age 62.7±14.3 years)were examined with a 3.0 T MRI system.Patients were divided into four groups:at the hyperacute stage(onset time ? 6 hours),at the acute stage(6 hours<onset time ? 48 hours),at the early subacute stage(48 hours<onset time ? 96 hours),and at the late subacute stage(96 hours<onset time ? 168 hours).The APTW signal intensities were quantitatively measured in multiple ischemic regions for each patient.Results:Compared with the contralateral normal white matter,APTW signals were significantly lower in ischemic tissue for all four stages(P<0.05).Among the four gourps,APTWave values were(-0.85±0.02)%.(-0.64±0.09)%,(-0.48±0.11)%.and(-0.34±0.10)%,repectively;APTWmax values were(-0.02±0.04)%,(-0.24±0.07)%.(-0.23±0.10)%,and(-0.11±0.07)%,repectively;APTWmin values were(-1.24±0.04)%.(-1.06±0.10)%,(-0.85±0.08)%,and(-0.70±0.09)%,repectively;APTWmax-min values were(1.22±0.06)%,(0.82±0.07)%,(0.62±0.05)%,and(0.59±0.07)%,repectively.The APTW signal intensities(APTWave and APTWmin)increased consistently with onset time(R2=0.11,P=0.040;R2 = 0.13,P = 0.022;respectively).APTWmax-min showed a continued reduction with onset time(R1= 0.43,P<0.001).Conclusion:Our results suggest persistent tissue acidification could occur after ischemia,and as the time from stroke onset increases,the acidotic environment would alleviate.APTW signal intensities could reflect pH-weighted properties in ischemic tissue at different stages and time points.(part 3)A Retrospective Study of Amide Proton Transfer-Weighted MR Imaging in Acute Ischemic StrokeObjective:Amide Proton transfer(APT)-weighted MRI has been demonstrated to be promising in stroke patients.However,the APT image characteristics in stroke subtypes have not been focused.To investigate the APT-weighted MRI features in different subtypes of acute ischemic stroke(AIS).Patients and Methods:Eighty-one AIS patients presenting within 96 hours of symptom onset were enrolled(56 males,25 females,age ranging 26-92 years,average age 65.5±13.7 years).APTW and routine MRI were performed in all subjects.Patients were grouped according to the radiological Oxfordshire Community Stroke Project(OCSP)classification:total anterior circulation infarcts(TACI,n = 9),partial anterior circulation infarcts(PACI,n = 28),lacunar circulation infarcts(LACI,n = 33),and posterior circulation infarcts(POCI,n = 11).APT values in the lesion(APTWlesion)and the contralateral normal-appearing region(APTWcon)were measured.The difference of APTWlesion and APTWcon(APTWles-con)was calculated.Results:The differences between APTWledion and APTWcon were significant in TACI,PACI and POCI groups(P<0.01),except the LACI group(P = 0.080).LACI patients had higher APTWlesion and lower APTWles-con than other groups(P<0.01).TACI patients had lower APTWlesion and greater APTWles-con than others(P<0.01).Patients with infarcts of brainstem from the LACI and POCI groups showed no significant differences between APTWlesion and APTWcon.Conclusion:Tissue acidification during acute stroke is more severe in TACI patients,and mild in LACI patients.APTW MRI can sensitively detect tissue acidification in TACI,and PACI patients.However,for patients with LACI and infarcts at the brainstem,APT imaging would not be recommended.