Diffusion-weighted signal intensity

Lansberg MG, Thijs VN, O Brien MW, Ali JO, de Crespigny AJ, Tong DC, Moseley ME, Albers GW. Evolution of apparent diffusion coefficient, diffusion-weighted, and T2-weighted signal intensity of acute stroke. Am J Neuroradiol 2001 22 637-644. 

Fig. 11.3. Spectroscopic imaging of stroke. Data from a 71-year-old male were obtained at 3 T using conventional CSI with 144 ms echo time (17 min acquisition time). Metabolite intensities are plotted as color-coded overlay on diffusion-weighted images. Intensities of SI maps of NAA and lactate were obtained by time domain data fit using jMRUI. Representative spectra and fit results (red line) are shown in the lower part of the figure. The arrows indicate the position of the respective voxels. Low Lac values and persistent NAA signals in the posterior part of the area with increased signal on the DWI image may be caused by early reperfusion of an M3 branch of the middle cerebral artery and consecutive washout of Lac...

Fig. 11.4. Fast spectroscopic imaging of stroke. SI maps of lactate and NAA. Metabolite intensities are plotted as color-coded overlay on diffusion-weighted images. Intensities were obtained by numerical integration of the peak areas defined in the two spectra below. Data were acquired with the multiple spin echo SI sequence (7 min acquisition time), thus signal resolution is considerably reduced compared to single voxel spectra in Fig. 11.2 or conventional CSI in Fig. 11.3. (Data courtesy of A. Stengel)...

A reversible leukoencephalopathy has been attributed to chronic unintentional exposure to toluene in a 40-year-old chemical salesman [99 ]. An MRI scan showed extensive, diffuse white matter changes with increased T2-weighted signal intensity throughout the subcortical and periventricular white matter. 

Fig. 4.8. Lesion development in permanent middle cerebral artery (MCA) occlusion in a rat measured by repeated MR diffusion-weighted imaging (DWI). Left column Control condition pre-occlusion in coronal slices from posterior (top) to anterior (bottom). The arrow marks the timepoint of occlusion. Images shown in columns 2 to 7 are DWI (subtraction images) measured 30 to 330 min post-occlusion. Note the lesion growth and the increase in signal intensity within the lesion. (Courtesy Dr. M. Hoehn, Cologne)...

Figure Bl.14.13. Derivation of the droplet size distribution in a cream layer of a decane/water emulsion from PGSE data. The inset shows the signal attenuation as a function of the gradient strength for diffusion weighting recorded at each position (top trace = bottom of cream). A Stokes-based velocity model (solid lines) was fitted to the experimental data (solid circles). The curious horizontal trace in the centre of the plot is due to partial volume filling at the water/cream interface. The droplet size distribution of the emulsion was calculated as a function of height from these NMR data. The most intense narrowest distribution occurs at the base of the cream and the curves proceed logically up through the cream in steps of 0.041 cm. It is concluded from these data that the biggest droplets are found at the top and the smallest at the bottom of the cream.

Fig. 7.3 The ADC for a given gradient direction is caicuiated on a pixel-by-pixel basis by fitting signal intensities to the diffusion equation for at least two diffusion-weighted images corresponding to two separate t>-values. The slope of the fit corresponds to the ADC value for that particular gradient direction...

Mintorovitch, J., et al.. Diffusion-weighted magnetic resonance imaging of acute focal cerebral ischemia comparison of signal intensity with changes in brain water and Na+,K(-t-)-ATPase activity. J Cereb Blood Flow Metab, 1994. 14(2) p. 332-6. 

Fig. 5.22. Leiomyoma, diffuse adenomyosis and endometrial polyp on MRI. T2-weighted sagittal image of a patient depicts di se adenomyosis (arrowheads) with symmetrical broadening of the junctional zone. An endometrial polyp exhibiting similar high signal intensity as the endometrium can be clearly identified within the uterine cavity (short arrow). A fibroid is present in the fundus (long arrow)...

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