Comparison of ADC Map with Trace Map in the Normal and Infarct Areas of the Brains of Stro ke Patients

Kim, Seung Hyung; Yoon, Pyeong Ho; Jeong, Eun Kee; Oh, Young Taick; Kim, Dong Ik

Abstract

PURPOSE: To compare ADC mapping with trace mapping in normal and infarct areas of the brains of strokepatients.
MATERIALS AND METHODS
Eighteen patients diagnosed on the basis of clinical and brain MRI examinationsas suffering from brain infarction were included in this study (hyperacute-1, acute-4, subacute-12, chronic-1).Diffusion weighted images of three orthogonal directions of a patient's brain were obtained by means of a singleshot EPI pulse sequence, using a diffusion gradient with four serial b-factors. Three ADC maps were thenreconstructed by post-image processing and were summed pixel by pixel to yield a trace map. ROIs were selected inthe normal areas of white matter, gray matter and CSF of one hemisphere, and other ROIs of the same size wereselected at the same site of the contralateral hemisphere. ADC and trace values were measured and right/leftratios of ADC and trace values were calculated. Using these values, we then compared the ADC map with the tracemap, and compared the degree of anisotropic diffusion between white matter, gray matter and CSF. Except for three,whose infarct lesions were small and lay over white and gray matter, patients were divided into two groups. Thosewith infarct in the white matter (n=10)were assigned to one group, and those with in-farct in the gray matter(n=5) to the other. ROIs were selected in the infarct area and other ROIs of the same size were selected at thesame site of the contralateral hemisphere. ADC and trace values were measured and infarct/contralateral ratioswere calculated. We then compared ADC ratio with trace ratio in white matter and gray matter infarct.
RESULTS
Innormal white matter, the Dxx ratio was 0.980 +/-0.098, the Dyy ratio 1.019 +/-0.086, the Dzz ratio 0.999 +/-0.111,and the trace ratio 0.995 +/-0.031. In normal gray matter, the Dxx ratio was 1.001 +/-0 . 0 5 8 , the Dyy ratio0.996 +/-0.063, Dzz ratio 1.005 +/-0.070, and the trace ratio 1.001 +/-0.028. In CSF, the Dxx ratio was 1.002+/-0.064, the Dyy ratio 1.023 +/-0.055, the Dzz ratio 0.999 +/-0.060 and the trace ratio 1.007 +/-0 . 0 2 1. Becausethe standard deviation of trace ratios (<0.05) is less than that of ADC ratios (>0.05), the trace ratio is moreaccurate representative value. The standard deviation of white matter is greater than that of gray matter or CSF(p<0.05), the degree of anisotropic diffusion in white matter is therefore more severe than in gray matter andCSF. The difference between the ADC ratios and trace ratio is greater in an infarct involving white matter than inone involving gray matter (p<0.05). CONCLUSION: Because a trace map overcomes the anisotropic diffusions of ADCmaps, the former offers better post-image processing. The deviation of ADC ratios owing to the direction ofdiffusion gradient is greater in white matter than in gray matter, and the trace map is thus superior forevaluation of an infarct involving white matter.