Biomedical Engineering Reference
In-Depth Information
FIGURE 4.1
(a) Real space profile through the object to be imaged. (b) Frequency spectrum obtained
from (a) by Fourier transformation. Note the broad wings of the spectrum, reflecting the
very wide range of frequencies required to characterize the object. (c) Slice profile used to
select a single slice from (a). Within the slice the sensitivity of the imaging system is unity,
whereas far from the slice there is zero sensitivity to the object. Gradual transitions exist at
the edges of the slice profile. (d) The frequency spectrum obtained for the slice profile by
Fourier transformation. Note that although the central maximum is broader than in (b), the
full spectrum occupies a much narrower frequency range. (e) The object profile convolved
with the slice profile. Selecting a slice corresponds to obtaining a point sample of this profile.
(f) The frequency spectrum obtained by Fourier transformation of (e), and equivalent to the
product of (b) and (d). Note that the broad wings in (b) have been suppressed, thus nar-
rowing the frequency range that must be sampled.
