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Harriet S. Meyer

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The following terms are commonly used in radiology.9

b value—The b factor or b value is associated with diffusion-weighted magnetic resonance imaging (diffusion-weighted MRI or DWI). It measures “strength (intensity and timing) of the diffusion gradient”9; units are seconds per square millimeter.

maximum b value of 1221 s/mm2

Four gradient strengths were applied, resulting in b values of 0 and 1000 s/mm2 applied sequentially in the X, Y, and Z gradient directions.

Doppler—See 15.3.6, Cardiology, Echocardiography.

echo train—A sequence of echoes. “Echo train is not a unit of measure”9 but is expressed as in these examples:

echo train length 5

echo train length 18

echo train length 16

echo train length 20

a long echo-train-length 3-dimensional fast-spin echo sequence

k-space—This term refers to mathematical space with frequency and phase as coordinates, rather than spatial coordinates.6

Our pulse sequences collected data spirally in k-space.

k-space filtering

k-space sampling

number of excitations/signals—Change “number of excitations” to “number of signals acquired” (applies to MRI).

T1, T1ρ, T2, T2*—These are types of relaxation time in magnetic resonance imaging.5,6 They need not be expanded.


spin-lattice or longitudinal relaxation time


spin-lattice relaxation time in the rotating frame


spin-spin or transverse relaxation time


time constant for loss of phase coherence among spins

TE, TR—Expand echo time (TE) and repetition time (TR) as in this example:

cardiac-gated repetition time (TR) greater than 2400 milliseconds; echo times (TEs), 20 and 80 milliseconds

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