Magnetization transfer study of HIV encephalitis and progressive multifocal leukoencephalopathy. Groupe d'Epidémiologie Clinique du SIDA en Aquitaine.

PURPOSE: To ascertain whether the use of magnetization transfer (MT) in MR imaging can characterize tissue destruction in human immunodeficiency virus (HIV)-positive patients with presumed progressive multifocal leukoencephalopathy (PML) or HIV encephalitis. METHODS: Brain MR studies that included MT were obtained in three groups: 11 healthy control subjects, 10 HIV-positive patients with clinical and radiologic findings of PML, and 13 HIV-positive patients with HIV encephalitis. MT ratios (MTRs) were calculated in PML and HIV encephalitis lesions and in normal-appearing white matter in the patients and control subjects. RESULTS: PML lesions revealed a dramatic decrease in MTR (22% +/- 2.3). HIV encephalitis lesions had statistically significantly higher MTR values (40% +/- 3.8) than PML lesions. The MTR of normal-appearing white matter was significantly higher in the control subjects (47% +/- 2.3) than in the PML group (46% +/- 3.3) or the HIV encephalitis group (44% +/- 2.6). CONCLUSION: MTR determinations suggest the possibility of distinguishing PML from HIV encephalitis and of indicating whether HIV encephalitis is involved in white matter that appears normal on conventional MR images.

[Progressive multifocal leukoencephalopathy. Study of the demyelination by magnetization transfer]. / Leucoencéphalopathie multifocale progressive. Etude de la démyélinisation par transfert de magnétisation.

PURPOSE: magnetization transfer imaging (MT) has been used to study the degree of demyelination in progressive multifocal leukoencephalopathy (PML). MATERIAL AND METHOD: two groups were studied: a group of 10 HIV + patients with clinical, MR features, biological and/or biopsy proven PML, and a group of 11 normal volunteers with matched age. MT ratio (MTR) were obtained from the center of the PML lesions and 11 areas of normal appearing white matter (NAWM) in the control group. RESULTS: the mean MTR of NAWM in the control group was 46.6% (SD = 2,3). PML lesions demonstrated a strong and significant (p = 0) decreased of the MTR with mean MTR value of 22.4% (SD = 2,3). CONCLUSION: MT characterized the demyelinating process in PML, and can be used to improve diagnosis. Furthermore, MT allowed a quantification of the degree of demyelination which can be helpful in other demyelinating process of CNS such as multiple sclerosis.

Magnetization transfer on in vitro circulating blood: implications for time-of-flight MR angiography.

Effects of magnetization transfer were evaluated in vitro on circulating blood. Various velocities were tested from 0 to 72 cm/second. Decrease signal intensity caused by magnetization transfer effects was inversely proportional to inflow velocity. It reached 10% at very low velocities and disappeared at velocities higher than 30 cm/second.