APT Imaging Study Of Intracellular Metabolic Changes In Different Regions Of Acute Cerebral Infarction

Objective: Using amide proton transfer(APT)imaging,the characteristics of amide proton transfer rate(APTR)changes and asymmetric magnetization transfer rate(MTRasym)changes in the cytotoxic edema area,infarct peripheral area and contralateral normal brain parenchyma of acute cerebral infarction were observed,and to explore the ability of these two different parameters to assess the changes of intracellular environmental metabolic state.Subjects and Methods: 44 patients with acute cerebral infarction were enrolled.All patients underwent conventional MRI,DWI,PWI,MRA,DKI(Diffusion kurtosis imaging,DKI),APT sequence scans.The MD,average kurtosis coefficient(MK),APTR,MTRasym,PWI and various parameter maps were obtained.(1)The changes of APTR and MTRasym parameters in the cytotoxic edema area,infarct peripheral area,and contralateral normal brain parenchyma were measured.(2)According to the DKI performance of cytotoxic edema area,observe the changes of APT parameters of different DKI performance.(3)According to the division of different perfusion states of infarcted area according to PWI,the changes of APT parameters under different perfusion conditions were analyzed,and division of the degree of ischemia in the peripheral area of the infarction,analysis of changes in APT parameter values caused by different degrees of ischemia.Statistical analysis was performed using SPSS22.0software package: for the differences in APT parameter values between cytotoxic edema area,infarct peripheral area,and contralateral normal brain parenchyma area,using Fridman related sample test and pairwise comparison to analyze the difference of APT parameter values in different regions;analysis of differences in APT parameter values between different DKI performance regions using Wilcoxon paired sample test;Wilcoxon paired sample test was used to analyze the changes of APT parameters under different perfusion conditions in the infarct peripheral area and the changes of APT parameters caused by different ischemic degrees in the infarct area.Results:(1)Among 44 patients,There were significant statistical differences in APTR parameters(-0.0136±0.013、-0.0043±0.010、-0.0006±0.008,c2=52.08,P < 0.0001)between cytotoxic edema area,infarct peripheral area and contralateral normal brain parenchyma area,the cytotoxic edema area was statistically different from the infarct peripheral area and the contralateral normal brain parenchyma area(Z =-5.277,P <0.0001;Z =-6.876,P < 0.0001),there was no significant difference between the infarct peripheral area and the contralateral normal brain parenchyma area(Z =-1.599,P = 0.329);the MTRasym parameter values did not show obvious regularity and statistical difference in the cytotoxic edema area,the infarct peripheral area,and the contralateral normal brain parenchyma area(0.0264±0.181 、-0.0289±0.075 、-0.0389±0.027,c2=0.318,P =0.853).MTRasym parameter signal reversal in some cytotoxic edema areas,statistical analysis shows that,MTRasym signal reversal cases and unreversed cases,there were no significant differences in gender,age,infarct location,NIHSS score,and onset time between the two groups,but the lesion size is significantly different(t=-2.965,P = 0.005).(2)In the cytotoxic edema area,APTR has a decreasing trend in DKI positive and negative areas(-0.0254±0.026 和-0.0140±0.021,Z=-1.955,P=0.051),it is suggested that the infarct core area has more obvious APTR parameter change trend than the potentially reversible damage area;the difference between the MTRasym parameter values in the above different areas is not obvious(0.0292±0.234 和 0.0759±0.227,Z=-1.008,P=0.314).(3)In the infarcted area,the APTR parameter values of hypoperfusion were statistically different(Z=-2.101,P=0.036),there was no statistical difference between the normal perfusion group and the contralateral side(Z=-0.966,P=0.334);MTRasym parameter values were not statistically different between the low perfusion and normal perfusion groups(Z=-0.370,P=0.711;Z=-0.852,P=0.394).For different degrees of ischemia,the APTR parameter value of the severe ischemia group was more obvious than that of the mild ischemia,but has not yet reached statistical difference(Infarct peripheral area is-0.0055±0.005,Contralateral normal brain parenchyma is 0.0005±0.010,Z=-1.895,P=0.058);the difference in MTRasym parameter values was not significant in mild ischemia and severe ischemia.Conclusions: APT imaging has potential diagnostic value for prognostic outcome and perfusion status in different areas of acute cerebral infarction:(1)In the cytotoxic edema area,different DKI performance areas,APT parameters vary in degree,suggesting that APT parameters change more in the infarct core area,while the potential reversible damage area changes relatively lightly,and may be related to prognosis.(2)In the peri-infarct area,the hypoperfusion state will cause changes in APT parameters.As the degree of ischemia increases,the APT parameters also decrease,suggesting that APT parameters can reflect changes in intracellular environmental metabolism caused by hypoperfusion.Potential ability of ischemia.(3)The APTR parameters have better stability and reliability than the MTRasym parameters.The MTRasym parameters may have reversal in the pathology of some infarct areas,which may be related to larger lesions and more obvious edema.