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AJNR - American Journal of Neuroradiology

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Early Detection of Global Cerebral Anoxia: Improved Accuracy by High-b-Value Diffusion-Weighted Imaging with Long Echo Time

Khin K. Tha^a, Satoshi Terae^a, Toru Yamamoto^b, Kohsuke Kudo^a, Chihiro Takahashi^a, Masaki Oka^a, Shinji Uegaki^c and Kazuo Miyasaka^a,b,c

^a Department of Radiology, Hokkaido University Graduate School of Medicine, Sapporo, Japan
^b Department of Health Sciences, Hokkaido University Graduate School of Medicine, Sapporo, Japan
^c Department of Emergency Services, Hokkaido University Graduate School of Medicine, Sapporo, Japan

View larger version (115K): [in a new window]   FIG 1. T2-weighted image of a patient, showing positions of regions of interest. The regions of interest are shown in square boxes (with white borders). The section shown contains four regions of interest. Regions of interest for other sequences are also set at the same positions.

View larger version (21K): [in a new window]   FIG 2. ADC values of abnormal and normal regions of interest of the patients, measurable at b = 1000 s/mm2 (A) and at b = 3000 s/mm2 (B). For each column, the uppermost point indicates the maximum ADC value. The middle point indicates the mean ADC value, and the lowermost point the minimum. The bars indicate SDs.

View larger version (12K): [in a new window]   FIG 3. The ROC curves of each MR image achieved by the three observers. The high-b-value DWI holds the largest area under the curve (Az). The Az of the routine DWI (b = 1000 s/mm2), T2WI, and FLAIR imaging follow in descending order.

View larger version (43K): [in a new window]   FIG 4. Histogram showing Az for each MR image and observer. Asterisk represents statistical significance (P < .05 by univariate z score test). For all observers, the high-b-value DWI achieves the largest Az. For observer 1, Az between any two sequences shows statistically significant difference. For observer 2, the statistically significant difference is noted between the high-b-value DWI or FLAIR images and any other sequences. No significant difference is observed between routine DWI and T2WI. For observer 3, statistically significant difference is noted between any two sequences, except for Az between T2WI and FLAIR imaging.

View larger version (119K): [in a new window]   FIG 5. Routine DW image of a patient (A). High-b-value DW image (B). T2-weighted image (C). FLAIR image (D). The signal intensity abnormalities of bilateral cerebral cortex are more conspicuous on the high-b-value DWI.

View larger version (129K): [in a new window]   FIG 6. Routine DW image of another patient (A). High-b-value DW image (B). T2-weighted image (C). FLAIR image (D). The signal intensity abnormalities of bilateral cerebral cortex and deep gray matter are more conspicuous on the high-b-value DWI.

View larger version (11K): [in a new window]   FIG 7. The signal intensity attenuation curves for DWI. The horizontal (X) axis represents b value (b) and the vertical (Y) axis represents the logarithmic ratio of signal intensities (ln S[b]/S [0]).

View larger version (124K): [in a new window]   FIG 8. Routine DWI with long TE (190 ms) of a normal subject. Signal intensity from background brain tissue still persists.