Biomedical Engineering Reference
In-Depth Information
CBE from a 2.25 MHz synthetic-aperture
CBE to 60°C from a 7.5 MHz phased array
6
6
STD of CBE
Positive CBE
5
5
4
4
3
3
2
2
1
1
0
0
35
40
45
50
55
60
40
45
50
Temperature (°C)
Temperature (°C)
FIGURE 13.12
CBE Thermal Sensitivity from 37 to 60°C at 7.5 MHz and from 37 to 50°C at 2.25 MHz. (Left) Positive change in backscattered
energy at 7.5 MHz from an
ex vivo
specimen of porcine muscle. (Right) CBE from synthetic-focus images at 2.25 MHz in a 10 ×30 mm region of
bovine liver.
CBE calibration in turkey breast muscle
Temperature estimation: CBE sensitivity = 0.3 dB/°C
3
0.6
Slope = 0.3 dB/°C
2.5
0.4
2
0.2
1.5
0
−0.2
1
−0.4
0.5
−0.6
0
−0.8
−0.5
36
38
40
42
44
46
36
38
40
42
44
46
Temperature (°C)
Temperature (°C)
FIGURE 13.13
Calibration of CBE thermal sensitivity and temperature estimation in turkey breast muscle.
73
(Left) Mean ± standard deviation
of the change in backscattered energy (CBE) in 20 volumes (1 cm
3
each) from eight 4 × 6 × 2 cm specimens of turkey breast muscle. (Right) Mean
estimation error ± standard deviation of error values for temperature estimation using CBE over all 20 tissue volumes with a fixed CBE sensitivity
of 0.3 dB/°C.
13.4.4.3 3D Calibration and temperature
Estimation during Uniform Heating
well matched with a linear regression line (see Figure 13.13).
Correlation coefficients ranged from 0.991 to 0.999. The error of
the regression-line fit over all volumes and temperatures was 0 ±
0.07 dB. By definition, CBE at the reference temperature (37°C)
is zero. The slope for the 20 cubic centimeter volumes was 0.300
± 0.016 dB/°C.
Temperature estimation in 1 cm
3
volumes of turkey breast
muscle was based on calibration from a linear regression for
measured CBE in a separate 1 cm
3
volume of turkey breast mus-
cle. Figure 13.13 shows an example of estimation of tempera-
ture based on calibration using a fixed CBE thermal sensitivity
(0.3 dB/°C). Maximum positive and minimum negative errors
were 0.53 and -0.39°C.
The mean of the maxima of the absolute value of the errors
encountered in this
in vitro
study of CBE temperature estimation
To investigate the effect of temperature on backscattered energy
in 3D using backscattered energy, we calibrated CBE in 1 cm
3
volumes of turkey breast muscle during uniform heating. This
volume size was selected to match our long-term goal to measure
3D temperature distributions to within 0.5°C in 1 cm
3
volumes
for monitoring hyperthermia treatments.
35, 120
Temperature was estimated in separate 1 cm
3
volumes of tur-
key.
73
Both calibration and estimation were done after compen-
sation for motion in 3D. CBE as a function of temperature was
measured in 20 1 cm
3
volumes from eight specimens of turkey
breast muscle using the standard deviation of the energy ratio
in a given tissue volume.
43
The slope of each CBE curve was
