Relation Between Early CT Signs And Ischaemic Core Size On DWI MR In Stroke Patients At The 2^nd Affiliated Hospital Of Dalian Medical University

Background and Purpose: Stroke is the third leading cause of mortality in the world.It is also the most common cause of disability in the adult population1,2.Stroke is therefore a major medical cost for family units and governments alike,accounting for a significant portion of the health budget in first world countries.The most common type of stroke is ischemic stroke,of which the middle cerebral artery(MCA)region is the most affected1-7.The Alberta Stroke Program Early CT Score(ASPECTS)is a semiquantitave method of delineating the extent of middle cerebral artery(MCA)territory stroke which is reliable,consistent and reproducible12-15.The ischemic core size is the earliest radiological measurement of the irreversible ischemic damage to cerebral parenchyma.The main aim of this study was to retrospectively determine the relation between the early CT signs using ASPECTS on non contrast computer tomography(NCCT/ NECT)and the ischemic core circumference using diffusion weighted magnetic resonance imaging(DWI).NCCT or plain CT is the first line investigation in acute stroke imaging that is readily accessible in most facilities,has less contraindication,has faster scan times and is more affordable compared to MRI.Thus the use of NCCT ASPECTS to determine extent and outcome will benefit the patient as a fast,reliable and available around the clock tool.Furthermore,the use of DWI is now widely available in most tertiary care institutions.A correlation of the core circumference with the NCCT ASPECTS could transform patient care in these facilities that may not have more sophisticated imaging equipment and/ or post-processing software,such as in perfusion imaging studies.Methods: A retrospective study of diagnostic imaging investigations,namely NCCT and DWI magnetic resonance,taken at the Second Affiliated Hospital of Dalian Medical University in 2015 were examined.First time(including the cerebral hemisphere affected for the first time)MCA territory stroke patients presenting in the acute phase who were evaluated by non contrast CT(NCCT)within 12 hours and then diffusion weighted magnetic resonance(DWI MR)imaging within 1-5 days,with follow up MR angiography(MRA)images available,were included.Patients were excluded for hemorrhagic stroke,lacunar infarcts and persistently stenosed or occluded vessels.Twenty-four patients met the inclusion criteria and were assessed by two raters through consensus.The ASPECTS of Noncontrast computer tomography and diffusion weighted magnetic resonance were determined,and the average ischemic core circumferences on DWI MR measured.The ASPECTS on DWI MR served as the radiological reference point and gold standard in identifying infarct regions in the brain.The mean age,mean ASPECTS of the NCCT and DWI MR,mean of ischemic core circumferences,sensitivity of NCCT ASPECTS,comparison of the ischemic core circumferences betweens two groups of ASPECTS ≤ 7 and ASPECTS>7,correlation of the NCCT ASPECTS with the DWI ischemic core circumferences,were calculated using the IBM SPSS version 23 software.P values <0.05 were in all calculations considered significant and null hypothesis rejected.Results: Twenty-four patients who satisfied the study criteria were eventually included: 45.8%(11/24)were females and 54.2%(13/24)male subjects.DWI MR revealed 57 regions with infarction from the total 240 regions of interest(ROI).The NCCT ASPECTS only picked out 39 regions with infarct with a sensitivity of 68.4%.The mean age is 67 years and standard deviation 12.85 years.The means of ASPECTS on NCCT and DWI were 8.375 ± 1.408 and 7.625 ± 1.929 respectively at 95% confidence interval.The mean of ischemic core sizes was 73.208 mm ± 48.594 mm.The means of ischemic core circumferences between the two NCCT ASPECTS groups yielded t = 5.096 and p = 0.000042(critical t value is 2.069).The means of ischemic core circumferences in the reference DWI ASPECTS groups was also significantly different;t = 7.603 and p = 0.000001.The mean ischemic core in gender groups(male/female)had no significant statistical difference;t =-0.475,p = 0.640.The mean of NCCT ASPECTS and DWI ASPECTS were also the same;t = 0.060,p = 0.953.In correlation analysis,NCCT ASPECTS and ischemic core size Pearson coefficient was r = 0.382 and p =0.066.DWI ASPECTS and ischemic core size were r =-0.264,p = 0.212.Discussion and Conclusion: In a retrospective cohort of nonlacunar MCA territory strokes reviewed at the 2nd Affiliated Hospital of Dalian Medical University radiology department,there was a significant difference in the means of ischemic core circumferences of NCCT ASPECTS ≤ 7 and NCCT ASPECTS >7.The two groups are not the same.However,the means of NCCT ASPECTS and those of reference DWI ASPECTS were the same,therefore NCCT ASPECTS is accurate in determining the early infarct extent and predicting outcome in MCA territory stroke patients.There was no relationship found between ischemic core circumferences measured on DWI and the NCCT ASPECTS scores of acute and subacute phase MCA territory strokes that were studied.Therefore,the ischemic core size cannot be interchanged for NCCT ASPECTS in determining infarct extent and outcome prediction for MCA territory ischemic stroke patients.Future research using a larger sample size,all axial cuts of the cerebral regions on non contrast CT for ASPECTS,accounting for MR spacing in the measurement of average circumferences on DWI and preferably a prospective study design may yield different results from this paper.