Proton density images

Fig. 2.8.9 (a) Implementation of opposed jet device, (b) Proton density image obtained across a horizontal slice, (c) Velocity image obtained across a horizontal slice, (d) Velocity profile taken along the x axis of the cell showing the uniform extensional strain rate e such that vx — ex (adapted from Ref. [15]). 

Fig. 5. Standard fast spin-echo imaging of the pelvis and the lower leg. Typical contrasts between musculature and other tissues are demonstrated. Bl = bladder, Fe = femur. Gluteus = gluteus muscle. Original recording parameters matrix 192 x 256, slice thickness 6 mm, a-c field of view (fov) = 380 mm, d-f fov = 180 mm. (a) and (d) Proton density weighting TR = 5000 ms, TE = 12 ms. (b) and (e) Ti-weighting TR = 500 ms, TE = 12 ms. (c) and (f) 7 2-weighting TR = 5000 ms, TE = 100 ms.

Compared to lipids in the subcutaneous fat layer and in the bone marrow (TiR O.S s), musculature shows a clearly slower longitudinal relaxation (Ti 1.0 s). For this reason, musculature has lost more signal intensity than fat in Ty weighted images, when compared with proton density weighting (Fig. 5a... 

Figure 7. Proton density image of Ice+MCH with different degree of ice packing the left images correspond to highly packed ice and the right images correspond to not so highly packed ice. (Reprinted from J. Phys. Chem. B (Susilo et al., 2006), Copy right (2006) with permission from American Chemical Society).

The final effect on image contrast is proton density, or the relative nnmber of protons per nnit volnme. To produce contrast dne to proton density differences, the transverse... 

Fig. 4.7. Coronal measurements of diffusion, proton density (RHO), T1 and T2 relaxation times 30 min after occlusion of the middle cerebral artery in a rat. Note the clear-cut striatal signal increase in the diffusion-weighted image (DWI) compared to nearly unchanged images of the other MR modalities...

Proton density-weighted images seem to be as sensitive as FLAIR in detecting SAHs of less than 24 h. CSF flow artifacts in cisterns and ventricles are less likely to be observed with proton density than with FLAIR (Wiesmann et al. 2002). A recent report suggests that proton-density weighted sequences allow an accurate diagnosis of hyperacute SAH (Fiebach et al. 2004). 

In normal elderly controls, non-specific periventricular and subcortical T2-hyperintense lesions of the brain are a common finding and are reported in 27%-92% of the elderly population (Breteler et al. 1994 de Leeuw et al. 2001). In asymptomatic individuals over 50 years of age, changes in the white matter on T2-weighted, proton density and FLAIR images are frequently found, varying from a few scattered lesions in the centrum semiovale or peri-... 

Fig. 16.5a-d. The late imaging shows diffuse cortical necrosis seen as areas of hyperintensity on T2-weighted imaging (a, d). Proton density image is shown in (b). There are also the typical Tl-weighted hyperintensities in the parietal cortex bilaterally (arrows, c)... 

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