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Intravascular Photothermal Strain Imaging for Lipid Detection
摘要： Cardiovascular disease (CVD) is one of the major threats to humanity, accounting for one-third of the world’s deaths. For patients with high-risk CVD, plaque rupture can lead to critical condition. It is therefore important to determine the stability of the plaque and classify the patient’s risk level. Lipid content is an important determinant of plaque stability. However, conventional intravascular imaging methods have limitations in ?nding lipids. Therefore, new intravascular imaging techniques for plaque risk assessment are urgently needed. In this study, a novel photothermal strain imaging (pTSI) was applied to an intravascular imaging system for detecting lipids in plaques. As a combination of thermal strain imaging and laser-induced heating, pTSI differentiates lipids from other tissues based on changes in ultrasound (US) velocity with temperature change. We designed an optical pathway to an intravascular ultrasound catheter to deliver 1210-nm laser and US simultaneously. To establish the feasibility of the intravascular pTSI system, we experimented with a tissue-mimicking phantom made of fat and gelatin. Due to the difference in the strain during laser heating, we can clearly distinguish fat and gelatin in the phantom. The result demonstrates that pTSI could be used with conventional intravascular imaging methods to detect the plaque lipid.
关键词： photothermal strain imaging,intravascular ultrasound (IVUS),thermal strain imaging,lipid detection,unstable plaque,intravascular imaging,cardiovascular disease
更新于2025-09-23 15:21:01
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Temporal evolution of photo-induced thermal strain in InSb probed by ultra-short laser produced Cu Kα x-rays
摘要： Development and characterization of a wire target based kHz rep rate Cu Kα x-ray source using a Ti:sapphire laser system and its use in time resolved x-ray diffraction (TXRD) of the InSb (111) sample are presented. The observed Kα x-ray photon flux is ～3.2 × 109 photons sr?1 s?1 at a laser intensity of ～3.5 × 1016 W cm?2. TXRD signal from the InSb (111) crystal pumped by an ultrashort Ti:sapphire laser pulse (fluence ～ 13 mJ cm?2) shows a lattice expansion due to heating on a multipicosecond time scale. The crystal gradually cools down and recovers at ～1.5 ns after the laser excitation. The observed strain variation in the crystal matches well with the simulated results. The study of full recovery of the sample will be helpful for the development of InSb based devices.
关键词： Cu Kα x-ray source,time resolved x-ray diffraction,ultrashort laser pulses,thermal strain,InSb
更新于2025-09-11 14:15:04
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Coherent Acoustic Phonon and Its Chirping in Dirac Semimetal Cd <sub/>3</sub> As <sub/>2</sub>
摘要： Ultrafast optical spectroscopy of a single crystal of a Dirac semimetal Cd3As2 is carried out. An acoustic phonon (AP) mode with central frequency ?? = 0.037 THz (i.e., 1.23 cm?1 or 0.153 meV) is unambiguously generated and detected, which we attribute to laser-induced thermal strain. An AP chirping (i.e., variation of the phonon frequency) is clearly detected, which is ascribed to heat capacity variation with time. By comparing our experimental results and the theoretical model, we obtain a chirping time constant, which is 31.2 ps at 6 K and 19.8 ps at 300 K, respectively. Significantly, we identify an asymmetry in the AP frequency domain peak and find that it is caused by the chirping, instead of a Fano resonance. Moreover, we experimentally demonstrate that the central frequency of AP is extremely stable with varying laser fluence, as well as temperature, which endows Cd3As2 application potentials in thermoelectric devices.
关键词： Cd3As2,chirping,acoustic phonon,Dirac semimetal,thermoelectric devices,thermal strain
更新于2025-09-09 09:28:46