Biomedical Engineering Reference
In-Depth Information
FIGURE 8.9
BSD-500 applicators type MA-151, MA-120, and
MA-100.
(a)
75
65
55
45
35
25
15
5
-5
-15
-25
-35
-45
-55
-65
-7
-75 -60 -45 -30 -15 0 530 560 5
(b)
known as an effective method to improve the uniformity of the
E-field distribution across the aperture of a rectangular wave-
guide applicator [62,63]. The drawback of such a waveguide
design is the difference in wave velocity in the dielectric slab
at the side walls with that at the center of the waveguide, mak-
ing it difficult to combine these waveguides in an array setup.
Similarly, the ridge waveguide design (single or dual ridge) is
a known technique to concentrate the RF energy to the aper-
ture area near the ridge. The MA-100, MA-120, and MA-151
are advised for heating nodular type of tumors fitting within
the heating area. In accordance with the 915 MHz operating
frequency, the recommended heating depths are 2.5, 2.5, and
2.0 cm, respectively.
Recently, BSD Medical Corporation has extended their appli-
cator range for the BSD-500 with two multi-element applicators:
an 8-element rigid and a 24-element flexible array applicator
at 915 MHz. The SA-812 applicator is a closely spaced array of
8 dual-armed Archimedean spiral antennas (Figure 8.10). The
array is configured as seven closely spaced 3.35 cm diameter
spirals surrounding a central 4.05 cm diameter spiral. For each
antenna the spiral traces are deposited on a 12 cm diameter
plexiglass substrate with an integral water bolus. The overall
diameter of the applicator is 14 cm and the thickness varies
between 3.0 and 4.5 cm (maximum water bolus). The struc-
ture is such that it can be utilized with a mechanical support
arm to maintain its position over the patient, but is consider-
ably lighter in weight and more easily positioned near complex
75
65
55
45
35
25
15
5
-5
-15
-25
-35
-45
-55
-65
-7
-75 -60 -45 -30 -15 0 530 560 5
(c)
FIGURE 8.10
BSD-500: 8-element applicator. (a) Prototype SA-812 with
8 dual-armed Archimedean spiral antennas; (b) Uniform SAR pattern;
(c) “C-shape” SAR pattern. (From Johnson, J.E., Neuman, D.G., Maccarini,
P.F., Juang, T., Stauffer, P.R., Turner, P.,
Int J Hyperthermia
22, 2006.)
TABLE 8.2
BSD-500 Waveguide Applicators
a
Applicator Type
MA-100
MA-120
MA-151
Aperture size (cm
2
)
10 × 13
18 × 24
4 × 5
Heating area (cm
2
)
8 × 10
12.5 × 19.5
2.5 × 2.5
Heating depth
2.5
2.5
2.0
a
All values as provided by BSD Medical Corporation.
