Objective:To assess the value of amide proton transfer weighted (APTw) imaging in the evaluation of pH changes in infarct core (IC) and ischemic penumbra (IP) in subacute cerebral infarction.Methods:The data of twenty-three subacute cerebral infarction patients with unilateral steno-occlusive disease of the middle cerebral artery (subacute infarction group) from April to November 2019 in the First Affiliated Hospital of Dalian Medical University were prospectively analyzed. Fifteen healthy volunteers were enrolled in this study as the control group. All subjects underwent conventional MRI, DWI, 3D-pseudo continuous arterial spin labeling (3D-pCASL) and APTw sequences. Based on DWI images, relative cerebral blood flow (rCBF) and APTw images to determine the region of IC, blood flow penumbra [cerebral blood flow(CBF)-DWI mismatch area, IP CBF] and metabolic penumbra (APTw-DWI mismatched area, IP APT). 3D ROIs were used to semi-automatically measure the APTw signals and the volume of IC and IP CBF of the patients in subacute infarction group. The comparison of APTw signals between the infarct side and the contralateral side in the subacute infarction group, the comparison of bilateral APTw signals in the control group, and the comparison of APTw signals in the IC and IP CBF regions were performed by paired-sample t test or Wilcoxon signed-rank test. The paired-sample t test or Mann-Whitney U test was used to compare the APTw signals between the two groups. The Friedman test was applied to compare the difference of volumes among IP CBF1.5, IP CBF2.5 and IP APT . Results:There was no significant difference of the APTw signals among the IC, the contralateral side in the subacute infarction group and the control group ( P>0.05). The APTw signals of IP CBF and IC of the infarction group were statistically different ( P<0.05). Compared with the contralateral side of IP CBF1.5 (3.7±1.7, -1.84±1.48, 5.57±2.75), the APTwmax (3.07±1.41, t=-3.012, P=0.006), APTw min [-1.30 (-1.74, -0.57), Z=-2.099, P=0.036], and APTwmax-min(4.51±2.58, t=-3.273, P=0.003) signals in the IP CBF1.5 were decreased ( P<0.05). Compared with the contralateral side of IP CBF2.5 [-1.53 (-2.80, -0.91), 5.31±2.61], the APTw min [-1.08 (-1.60, -0.49), Z=-2.616, P=0.009] and APTwmax-min (4.41±2.72, t=-3.228, P=0.004) signals in the IP CBF2.5 were decreased. The volumes of IP CBF1.5 [107.51(50.08, 138.61)mm 3], IP APT [99.00 (53.27, 121.335) mm 3] and IP CBF2.5 [89.91 (51.53, 139.87) mm 3] were successively reduced (χ2=7.913, P=0.019), and the volume of IP CBF2.5 was significantly smaller than that of IP CBF1.5 ( P=0.037). Conclusion:The acid-base metabolism in the IC of subacute cerebral infarction is not obvious, but the blood flow penumbra has local acid-base metabolism imbalance, and the range of metabolic penumbra coincides with the blood flow penumbra.

Objective To observe the influence of different acceleration factors(AF)on compressed sensing susceptibility weighted imaging(CS-SWI)for cerebral medullary veins of healthy people,and to screen the best AF.Methods Forty healthy volunteers were prospectively enrolled.Axial brain SWI images were obtained with CS technique under different AF(AF0,CS2,CS4,CS6,CS8 and CS10),and the phase value(PV)and standard deviation(SD)of bilateral septal vein(SV),internal cerebral vein(ICV),thalamus vein(TV),basal vein(BV)and dentate nucleus vein(DNV)were measured.Taken PV and SD of parietal white matter as controls,the signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of venous images were calculated.Then the original images were reconstructed with minimum intensity projection,and the subjective quality scoring of reconstructed images were performed using a 5-point scale.SNR,CNR,PV and quality score were compared among images under different AF,and the best AF,i.e.with the best performances for displaying and quantitatively analyzing cerebral medullary veins in healthy people was obtained.Results Compared with those acquired with AF0,SNR and CNR of all cerebral medullary veins acquired with CS6,CS8 and CS10 were significantly different(all adjusted P＜0.05).Meanwhile,significant differences of PV in bilateral SV and right TV were found among CS6,CS8 and CS10,also in bilateral ICV,left TV and bilateral BV between CS8 and CS10(all adjusted P＜0.05).Conclusion Excessive AF might decrease image quality of CS-SWI for cerebral medullary veins.CS4 was the best AF for displaying and quantitatively analyzing cerebral medullary veins in healthy people.