[Reference lines on diagnostic imagings of the head. Part 2: Reference lines on MRI]

Simple but accurate and useful methods to draw reference lines parallel to canthomeatal line (CML) and Reid's base line (RBL) on MRI are described in this paper. A line is drawn through the nasal root and the pontomedullary junction on a midsagittal MRI of the head. It is confirmed that this line is parallel to CML in 21 normal healthy volunteers and 33 patients who show no mass effect on the midsagittal image. It is also verified that a line through the nasal root and mesencephalon-pontine junction on the midsagittal image is parallel to RBL.