Biomedical Engineering Reference
In-Depth Information
(a)
( b)
(c)
15
10
7 5
5
0
-5
-10
-1
-15
-10
-5
0
x (cm)
5
10
15
(d)
FIGURE 8.4
(a) Schematic drawing of the current sheet applicator (CSA) and its electronic representation. (b) Disassembled CSA (Rotterdam
version) showing the capacitive electrodes, the current sheet is not shown (at the back). (c) Completely assembled CSA with cooling device to allow
higher RF powers. (d) Gaussian beam predicted relative SAR distribution at 1 cm depth in muscle-equivalent tissue for a 3 × 3 CSA array (E-fields
parallel) [52].
provided by Bach Andersen et al. [46] and Johnson et al. [47,48],
while later Lumori et al. [49,50] and Gopal et al. [51] devel-
oped it into a clinical version. The latest clinical CSA design is
by Rietveld et al. [52] (Figure 8.4) and is made of sticky copper
foil (0.05 mm) and polyethene (PE). The RF power is capaci-
tively coupled to the “current sheet” (55 × 49 mm
2
) creating a
resonant circuit at 434 MHz. The total is embedded in a Teflon
block; outer dimensions of the antenna are 75 × 65 mm
2
(l × w)
and 19 mm (h). The current flows along the longer dimension
of the sheet and so the dominant E-field is linearly polarized
parallel to the length of the CSA. Advantages offered by current
sheet applicators for tissue heating include compact size, a lin-
ear polarization of the induced electric field, and relatively large
heating area. It is shown that the effective field produced by a
pair of these elements is continuous regardless of whether the
