(MX) Dimension in the stationary (laboratory) frame of reference in the plane orthogonal (at right angles) to the direction of the static magnetic field (B0 or H0), z, and orthogonal to y, the other dimension in this plane. This is commonly defined to be in the direction of the frequency-encoding gradient.

(MY) Dimension in the stationary (laboratory) frame of reference in the plane orthogonal to the direction of the static magnetic field (B0 and H0), z, and orthogonal to x, the other dimension in this plane. This is commonly defined to be in the direction of the phase encoding gradient.

(MZ) Dimension in the direction of the static magnetic field (B0 and H0), in both the stationary and rotating frames of reference.

Hydrogen nuclei magnetic moments are randomly oriented in the absence of an external magnetic field and are considered to have a net magnetization of zero. Once hydrogen protons are placed in the presence of an external magnetic field, they align themselves in one of two directions, parallel or anti parallel to the net magnetic field, which is commonly referred to as the vector B0. The parallel and anti parallel protons cancel each other out, only the small number of low energy protons left aligned with the magnetic field create the overall net magnetization, this difference is all that counts. The magnetic moments of these protons are added together and are referred to as net magnetization vector (NMV) or the symbol 'M'.

See also Magnetization Transfer Contrast.

Omniscan® is a nonionic chelate complex with low osmolality used as a paramagnetic MRI contrast agent. The efficacy of Omniscan® is similar to that of Gd-DTPA. Omniscan® is given intravenously to enhance images of intracranial and spinal lesions where there is abnormal vascularity or an abnormal blood brain barrier. The complex does not cross an intact blood brain barrier so Omniscan® only accumulates in lesions such as neoplasm's and abscesses.

WARNING: NEPHROGENIC SYSTEMIC FIBROSIS Gadolinium-based contrast agents increase the risk for nephrogenic systemic fibrosis (NSF) in patients with acute or chronic severe renal insufficiency (glomerular filtration rate less than 30 mL/min/1.73m²), or acute renal insufficiency of any severity due to the hepato-renal syndrome or in the perioperative liver transplantation period.

See also Gadodiamide, and Classifications, Characteristics, etc.