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ure 5: AVG curve for a phased array 16 element, 1.4 mm pitch working at 2.25 MHz

Figure 5 ure 5: AVG curve for a phased array 16 element, 1.4 mm pitch working at 2.25 MHz

Related Figures (5)

Figure 1: probe and flat circular reflector geometry for model implementation Figure 1 shows the description of probe — reflector geometry, where it is assumed that the probe will produce a normal ultrasonic beam and the reflector disk is centered on the probe acoustical axis. The active surface of linear probe are discretized in small rectangular elements according to its phased array structure (in particular the j-index denote the j-th phased array element). Instead, disk reflector, due to its circular shape, is discretized according to the radial axis (m-index) and to the angular axis (n-index). The arrow denoted by pj ém,n indicates the path of ultrasonic field produced by the (j,k) probe element on the surface of (m,n) reflector element, where Pim iS the distance between the two elements. If we indicates with Ajimn the amplitude of such ultrasonic field, then the total field C,,,, produced on the (m,n) disk element is the summation of ultrasonic field produced by all the probe elements, that is:
Figure 1: probe and flat circular reflector geometry for model implementation Figure 1 shows the description of probe — reflector geometry, where it is assumed that the probe will produce a normal ultrasonic beam and the reflector disk is centered on the probe acoustical axis. The active surface of linear probe are discretized in small rectangular elements according to its phased array structure (in particular the j-index denote the j-th phased array element). Instead, disk reflector, due to its circular shape, is discretized according to the radial axis (m-index) and to the angular axis (n-index). The arrow denoted by pj ém,n indicates the path of ultrasonic field produced by the (j,k) probe element on the surface of (m,n) reflector element, where Pim iS the distance between the two elements. If we indicates with Ajimn the amplitude of such ultrasonic field, then the total field C,,,, produced on the (m,n) disk element is the summation of ultrasonic field produced by all the probe elements, that is:
Figure 2: AVG curve for standard probe B2S Equation (1), (2) (3) and (4) has been used to implement a computer program, written in Visual Basic 8.00, which accepts as input the phased array probe parameters and produces as output the numerical value, expressed in dB and normalized with respect to the maximum value, of amplitude S as a function of distance and diameter of reflector disk.
Figure 2: AVG curve for standard probe B2S Equation (1), (2) (3) and (4) has been used to implement a computer program, written in Visual Basic 8.00, which accepts as input the phased array probe parameters and produces as output the numerical value, expressed in dB and normalized with respect to the maximum value, of amplitude S as a function of distance and diameter of reflector disk.
ure 4: AVG curve for a phased array 32 element, 1.4 mm pitch working at 2.25 MHz A second assessment has been done generating two set of AVG curve: one for a 32 element, 1.4 mm pitch phased array probe working at 2.25 MHz and the other for similar probe but with 16 element.
ure 4: AVG curve for a phased array 32 element, 1.4 mm pitch working at 2.25 MHz A second assessment has been done generating two set of AVG curve: one for a 32 element, 1.4 mm pitch phased array probe working at 2.25 MHz and the other for similar probe but with 16 element.
Table I: comparison of experimental results obtained with a standard probe B2S and with phased array with two element configuration Looking at Table I we can observe that in the probe far field, regardless it’s a standard probe or a phased array probe, size estimations are quite good and comparable each other, while if we work in the near field, as the case of 32-elements phased array probe and the last two defects, we have a mismatch consisting in an oversizing of approximately a factor 2. This behavior can be easily explained taking into account that the nearfield region is quite complex to model, especially for what concern the real effect of probe bandwidth.
Table I: comparison of experimental results obtained with a standard probe B2S and with phased array with two element configuration Looking at Table I we can observe that in the probe far field, regardless it’s a standard probe or a phased array probe, size estimations are quite good and comparable each other, while if we work in the near field, as the case of 32-elements phased array probe and the last two defects, we have a mismatch consisting in an oversizing of approximately a factor 2. This behavior can be easily explained taking into account that the nearfield region is quite complex to model, especially for what concern the real effect of probe bandwidth.
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Computer ScienceAcousticsNursingPhased Array
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