Table 1.
Outline of 4bDWI sequence.
Figure 1.
The graph illustrates typical in vivo signal attenuation of diffusion-weighted imaging (DWI). S0 to S2500 are the signal intensities of the corresponding b-values. S0high and S0low are the theoretical S0 values calculated from a different data pair (pair of S500 and S1500, and pair of S1500 and S2500, respectively) using a monoexponential fitting (which becomes a straight line in this semi-logarithmic graph). Fraction of high b-pair (FH) equals S0high/S0low.
Figure 2.
Regions of interest (ROIs) for the ROI-based study.
A, B: Images acquired from a 1-year-old boy of unspecific acute encephalopathy. The images show the two specific slice levels selected for evaluation: the slice at the level of cerebral hemisphere (A), and the slice at the level of cerebral basal ganglia (B). Ten regions of interests (ROIs) were set as schematically illustrated for further assessments. C, D: A sample of accurate ROI 1 (frontal lobe of left cerebral hemisphere) acquired from a 2-year-old boy with suspected labium dyskinesia but which regressed a while after the examination (control group). C: Diffusion-weighted image before setting ROIs. D: Brightened area indicates the selected ROI, from which the pixels of cerebrospinal fluid and deep white matter were excluded as much as possible.
Figure 3.
Mean FH and ADC calculated in the encephalopathy group for analysis.
Mean fraction of high b-pair (FH) and apparent diffusion coefficient (ADC) for statistics were calculated for each patient. For the patients in the encephalopathy group, mean FH and ADCs were calculated for each category separately by averaging FH and ADCs across the regions of interests (ROIs) corresponding to each category. In this case (same case as in Fig. 2), five ROIs (ROIs 1, 3, 4, 5, and 8) corresponded to the “Severe” category, so the mean FH and ADC (only ADC calculated by b-value = 0 and 1500 (ADC0–1500) is shown here as example) for the “Severe” category was the averaged FH and ADC of the five ROIs. In this case, ROIs 7, 9, and 10 were categorized as “mild” and ROIs 2 and 6 as “indistinct”. Note: the schematic ROIs illustrated on the images seem to include deep white matter and cerebrospinal fluid, but the accurate ROIs for assessments did not include these areas (Fig. 2; D).
Figure 4.
A: FH map (FH: fraction of high b-pair) calculated from the images acquired from a 2-year-old boy in the control group (the same boy as in Fig. 2 C,D). B, C, and D: FH maps (upper) and corresponding diffusion-weighted images (DWI) at b = 1500 (lower) of 1-year-old girl with unspecific encephalopathy (B), 1-year-old boy with acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) (C), and another 1-year-old boy with AESD (D). FH seems elevated in the cortical and subcortical areas of the encephalopathy group (B, C, and D) compared to the control group (A). The prominence of elevation in FH seems related to the prominence of the abnormally high signal intensity in DWI, but the elevations of FH are seen even in areas where there are no particular findings in DWI (e.g., posterior area of (D)).
Table 2.
Categorization of ROIs of each patient in encephalopathy group.
Table 3.
Statistical analysis of FH and ADC.
Figure 5.
ADCs of each category in each b-value pair.
The bar graph shows the mean apparent diffusion coefficient (ADC) in each b-value pair in each category of the encephalopathy group. The error bar indicates standard deviations. The average ADC of the “indistinct” group was lower compared to the control group in the low b-pair (b = 0, 500), but it reversed toward the higher average in the high b-pair (b = 1500, 2500).