Which MR sequences are most effective in differentiating perivascular spaces from parenchymal lesions, and what are their key signal characteristics?

Proton-density (PD) and FLAIR sequences are crucial in distinguishing perivascular spaces from parenchymal lesions. On PD sequences, cerebrospinal fluid (CSF) appears similar in signal intensity to white matter, making perivascular spaces isointense to the brain, while ischemic lesions appear bright due to gliosis. On FLAIR sequences, parenchymal lesions with gliosis exhibit abnormal hyperintense signals, whereas perivascular spaces remain hypointense. A common pitfall is mistaking dilated perivascular spaces for small infarcts, especially in the basal ganglia, so careful evaluation of signal characteristics is essential.