A composite contrast agent, a nanoemulsion bead with assembled gold nanospheres at the interface, is proposed to improve the specific contrast of photoacoustic molecular imaging. A phase transition in the bead's core is induced by absorption of a nanosecond laser pulse with a fairly low laser fluence (∼3.5 mJ/cm2), creating a transient microbubble through dramatically enhanced thermal expansion. This generates nonlinear photoacoustic signals with more than 10 times larger amplitude compared to that of a linear agent with the same optical absorption. By applying a differential scheme similar to ultrasound pulse inversion, more than 40 dB contrast enhancement is demonstrated with suppression of background signals.
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机译：提出了一种复合造影剂，即在界面处具有组装好的金纳米球的纳米乳液珠，以改善光声分子成像的特定对比度。纳秒级激光脉冲的吸收具有相当低的激光通量（〜3.5 mJ / cm 2 ），从而引起了珠芯的相变，并通过显着增强的热膨胀产生了瞬态微气泡。与具有相同光吸收的线性试剂相比，这会产生非线性光声信号，其振幅比线性试剂大10倍以上。通过采用类似于超声脉冲倒置的差分方案，在抑制背景信号的情况下，对比度增强了40 dB以上。
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