Time-resolved absolute radius estimation of vibrating contrast microbubbles using an acoustical camera

Abstract

Ultrasound (US) contrast agents consist of microbubbles ranging from 1 to 10 μm in size. The acoustical response of individual microbubbles can be studied with high-frame-rate optics or an “acoustical camera” (AC). The AC measures the relative microbubble oscillation while the optical camera measures the absolute oscillation. In this article, the capabilities of the AC are extended to measure the absolute oscillations. In the AC setup, microbubbles are insonified with a high- (25 MHz) and low-frequency US wave (1–2.5 MHz). Other than the amplitude modulation (AM) from the relative size change of the microbubble (employed in Renaud, Bosch, van der Steen, and de Jong (2012a). “An ‘acoustical camera’ for in vitro characterization of contrast agent microbubble vibrations,” Appl. Phys. Lett. 100(10), 101911, the high-frequency response from individual vibrating microbubbles contains a phase modulation (PM) from the microbubble wall displacement, which is the extension described here. The ratio of PM and AM is used to determine the absolute radius, R0. To test this sizing, the size distributions of two monodisperse microbubble populations ([Formula: see text] 2.1 and 3.5 μm) acquired with the AC were matched to the distribution acquired with a Coulter counter. As a result of measuring the absolute size of the microbubbles, this “extended AC” can capture the full radial dynamics of single freely floating microbubbles with a throughput of hundreds of microbubbles per hour.

Equivalent-time-active-cavitation-imaging enables vascular-resolution blood-brain-barrier-opening-therapy planning

“…However, models of microbubble oscillation behavior (Marmottant et al 2005) and scattering (Anderson 1950, Johnson 1977, Censor 1988, Piquette et al 1988 also predict phase modulation effects. Previous studies have leveraged the contributions of phase modulation to size microbubbles (Fouan et al 2015, Spiekhout et al 2022. Future studies will investigate phase modulation to provide additional insights into the cavitating microbubbles in BP-ETACI.…”

“…RM has been used mostly as a μB-contrast imaging technique because the scattering-modulation effect is specific to μB. Work on RM first showed the change in amplitude of a high-frequency wave scattered by microbubbles through RM cycles induced by a low-frequency wave (Bouakaz et al 2007) which has been used to measure the size of individual μB (Spiekhout et al 2022). μB were found to produce different backscattered signal when high-frequency imaging pulses imaged them in compression and expansion phases of the RM (Chérin et al 2008).…”

Size quantification of non-spherical bubbles by ultrasound

“…需要注意, 利用级数法构建球形气泡散射模型时, 忽略热阻尼和液体黏度的 影响, 因为当入射声波频率远高于气泡的共振频率时, 热阻尼和液体黏度对散射 的影响很小 [19] . 其次, 构建级数模型时仅做远场近似且未对 ka 做任何限定, 故级 数解模型并不受 ka 限制.…”

Control of monodisperse microbubble properties for high-precision medical applications

“…By contrast, low amplitude microbubble oscillations (ϵ < 2.5%) of individual bubbles can be quantified using light scattering and by high-frequency (HF) off-resonance acoustic scattering [104][105][106][107]. In this work, we employ HF acoustic scattering using an experimental setup named the acoustical camera' [108,109] .…”

“…(D) Envelopes of the radial strain shown in (B) (same color coding) plotted together with a fit of a linearized bubble dynamics model. The design of the AC setup employed in the present work is improved with respect to that reported before [108,109]. First, the transmit transducers (HF1 and LF) now face upward at a 45 • angle in the water tank with an increased height (h in Fig.…”