Fig 1.
Homogeneity of the fluorescent microbubble coating before insonification.
(A) Number of microbubbles with hot spots (n = 137 microbubbles). (B) Number of hot spots per microbubble coating (n = 71 microbubbles). Hot spots were defined as focal areas of increased fluorescence intensity.
Fig 2.
Microbubble vibration during insonification at a frequency of 1 MHz and P_ of 50 kPa.
(A) D-t curve of the microbubble shown in 2B5; the letters correspond to the frames shown in 2B5. (B) Typical examples of lipid coating behavior during insonification. Arrow heads in leftmost column indicate hot spots present before insonification; arrows in second column to right indicate hot spots formed during insonification that persisted when the ultrasound was off; see S1–S6 Videos for the ultra-high-speed recordings of the shown selected frames. US = ultrasound; E = expansion phase; C = compression phase. The symbols in the rightmost column (see Fig 3 for more details) are the figure legends for Figs 4–10.
Fig 3.
Categories of fluorescence observations during insonification.
The symbols in the Fig are also used as Fig legend for Figs 4–11; see Fig 2B. FL = fluorescence; US = ultrasound.
Table 1.
Amount of newly formed hot spots on the coating of microbubbles.
Fig 4.
Amplitude at the fundamental frequency, fT.
For microbubbles insonified at a frequency of 0.5 MHz and a P_ of 25 kPa (A), frequency of 0.5 MHz and P_ 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3.
Fig 5.
Relative vibration amplitude, (E+C)/2.
For microbubbles insonified at a frequency of 0.5 MHz and a P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3.
Fig 6.
Relative compression amplitude, C.
For microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3.
Fig 7.
For microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3. Microbubbles with an E/C < 0.5 show compression-only behavior, indicated by the dashed line.
Fig 8.
The maximum negative amplitude of A0.
For microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3.
Fig 9.
Amplitude at the subharmonic frequency, .
For microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3. A value of 0 indicates no subharmonic was present.
Fig 10.
Amplitude at the second harmonic frequency, 2fT.
For microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 kPa (A), frequency of 0.5 MHz and P_ of 50 kPa (B), and frequency of 1 MHz and P_ of 50 kPa (C). For figure legend, see the rightmost column of Fig 2 and Fig 3. A value of 0 indicates no second harmonic was present.
Fig 11.
Relative microbubble diameter after insonification.
Combination of microbubbles insonified at a frequency of 0.5 MHz and P_ of 25 and 50 kPa and frequency of 1 MHz and P_ of 50 kPa; * indicates significant difference; for the symbols on the x-axis, see the rightmost column of Fig 2 and Fig 3.
Fig 12.
Percentage of microbubbles forming hot spots at frequency of 1 MHz and higher P_. n = 41 microbubbles.
Fig 13.
Microbubbles insonified at frequency of 1 MHz and higher P_.
Insonification at P_ of 300 kPa and 10 cycles (A) or P_ of 150 kPa and 15 cycles (B). Arrow head in leftmost column indicates hot spot present before insonification; arrows in rightmost column indicate hot spots formed during insonification that persisted when the ultrasound was off; see S7 and S8 Videos for the ultra-high-speed recordings of the shown selected frames. US = ultrasound; E = expansion phase; C = compression phase.