Magnetic field inhomogeneity is expressed in:

Magnetic field inhomogeneity refers to the variation in the magnetic field strength across a specified volume. This inhomogeneity is crucial in MRI because it can affect image quality and the uniformity of the magnetic field.

When measuring magnetic field inhomogeneity, it is most commonly expressed in parts per million (ppm). This unit provides a relative measure by comparing the variation in the magnetic field strength to its average value, which is essential in characterizing how much the field deviates from its ideal uniformity. This scale allows for a clear and meaningful assessment of inhomogeneity, especially when dealing with magnetic fields that can operate at very high strengths, such as those used in MRI systems.

The other choices relate to units of measure that involve magnetic fields or specific power absorbed in tissues but do not specifically pertain to the concept of magnetic field inhomogeneity. Watts per kilogram reflects the specific absorption rate (SAR), Gauss per centimeter is a measure more relevant to the gradient fields, and Tesla per meter relates to magnetic field strength gradients, rather than the assessment of uniformity in the magnetic field itself.