How is the homogeneity of the main magnetic field quantified?

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Multiple Choice

How is the homogeneity of the main magnetic field quantified?

Quantifying the uniformity of the main magnetic field is about how much B0 varies across the imaging volume relative to its nominal value. This is most meaningfully expressed as a relative deviation, typically measured in parts per million. Using ppm allows a single number to describe how uniform the field is across space, independent of how strong the magnet is. For example, at 3 Tesla, a 1 ppm variation corresponds to about 3 microtesla of deviation somewhere in the region of interest. Absolute field strength in Tesla describes how strong the magnet is, not how uniform it is. Units like MHz per Tesla relate to how the Larmor frequency scales with field (frequency per unit field) and are used for frequency considerations, not homogeneity. Units like mT per meter describe gradient strength used for spatial encoding, again not a measure of overall field uniformity. So, parts per million is the appropriate way to quantify the homogeneity of the main magnetic field.

Quantifying the uniformity of the main magnetic field is about how much B0 varies across the imaging volume relative to its nominal value. This is most meaningfully expressed as a relative deviation, typically measured in parts per million. Using ppm allows a single number to describe how uniform the field is across space, independent of how strong the magnet is. For example, at 3 Tesla, a 1 ppm variation corresponds to about 3 microtesla of deviation somewhere in the region of interest.

Absolute field strength in Tesla describes how strong the magnet is, not how uniform it is. Units like MHz per Tesla relate to how the Larmor frequency scales with field (frequency per unit field) and are used for frequency considerations, not homogeneity. Units like mT per meter describe gradient strength used for spatial encoding, again not a measure of overall field uniformity. So, parts per million is the appropriate way to quantify the homogeneity of the main magnetic field.

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