Temperature dependence of acoustic harmonics generated by nonlinear ultrasound beam propagation in ex vivo tissue and tissue-mimicking phantoms

Figures & data

Figure 1. Schematic of the experimental set-up.

Figure 2. The averaged (100 RF lines) values of (A) and (B) p_1, (C) and (D) p₂, (E) and (F) p₃ in tissue-mimicking gel phantom (left column) and ex vivo bovine muscle tissue (right column) at temperatures of 26°, 34°, 38° and 46 °C.

Figure 3. Changes in (A) p₁, (B) p₂, (C) p₃ and the ratios (D) p₂/p₁ and (E) p₃/p₁ as a function of temperature in tissue-mimicking gel phantoms with respect to the initial temperature (26 °C). The error bars represent the standard deviation of five trials.

Figure 4. Changes in (A) p₁, (B) p₂, (C) p₃ and the ratios (D) p₂/p₁ and (e) p₃/p₁ as a function of temperature in ex vivo bovine muscle tissues with respect to the initial temperature (26 °C). The error bars represent the standard deviation of six trials.

Table 1. Percentage increase in p₁, p₂, p₃ and the ratios p₂/p₁ and p₃/p₁ as the temperature was increased from 26° to 46 °C in tissue-mimicking gel phantoms and ex vivo tissue samples.

Harmonic amplitude	% increase in gel phantoms	% increase in tissue samples
p1	18 ± 6	69 ± 15
p2	47 ± 13	100 ± 42
p3	113 ± 19	283 ± 141
p2/p1	30 ± 10	17 ± 13
p3/p1	80 ± 14	114 ± 65

Figure 5. Changes in (A) E, (B) E₁, (C) E₂, (D) E₃ and the ratios (E) E₂/E₁ and (F) E₃/E₁ at the focal region as a function of temperature in tissue-mimicking gel phantoms with respect to the initial temperature (26 °C). The error bars represent the standard deviation of five trials.

Figure 6. Changes in (A) E, (B) E₁, (C) E₂, (D) E₃ and the ratios (E) E₂/E₁ and (f) E₃/E₁ at the focal region as a function of temperature in ex vivo bovine muscle tissues with respect to the initial temperature (26 °C). The error bars represent the standard deviation of six trials.

Table 2. Percentage increase in E, E₁, E₂, E₃ and the ratios E₂/E₁ and E₃/E₁ as the temperature was increased from 26° to 46 °C in tissue-mimicking gel phantoms and ex vivo tissue samples.

Backscattered harmonic energy	% increase in gel phantoms	% increase in tissue samples
E	48 ± 5	168 ± 28
E1	42 ± 7	163 ± 24
E2	121 ± 24	281 ± 143
E3	470 ± 198	2257 ± 1394
E2/E1	55 ± 22	43 ± 44
E3/E1	297 ± 123	770 ± 444

Figure 7. Changes in (A) p₁, (B) E₁, (C) p₂, (D) E₂, (E) p₃ and (F) E₃ at 44 °C as a function of time in ex vivo bovine muscle tissues with respect to the initial time (40 min). The error bars represent the standard deviation of four trials.