Technique for occult MS

Q. Which MR technique may be used to discern otherwise occult Multiple sclerosis disease in normal-appearing brain parenchyma?

a.MR spectroscopy

b.MT techniques

c. Diffusion-weighted MR imaging

d.T2W

e.T1W

ANS--.----b

MT techniques have been applied to brain MR in an attempt to characterize MS lesions and to discern otherwise occult disease in normal-appearing brain parenchyma.

This pulse sequence technique exploits differences in relaxation between immobilized water transiently bound to macromolecules and water protons not associated with macromolecules. The hypothesis underlying these investigations is that demyelination results in more free water (i.e., a reduction in the “bound” fraction of water) compared with myelinated white matter or intact but edematous tissue. Selective suppression of immobilized water is accomplished by the application of an off-resonance saturation pulse, which saturates the broad resonance of protons bound to macromolecules. Transiently bound protons exchange with free water protons by diffusion

 Using  experimental design, it has been shown in some studies that MT ratios are higher (i.e., there is more signal reduction due to the saturation pulse) in normal mature (myelinated) white matter than in gray matter. A slight decrease of the magnetization transfer ratio was noted in early inflammatory lesions without demyelination in models of experimental allergic encephalomyelitis. More pronounced reductions in MT ratios have been described in demyelinating lesions in experimental models (proportional to the degree of demyelination) and in patients with MS