Frequency-Domain Differential Photoacoustic Radar: Theory and Simulation for Ultra-Sensitive Cholesterol Imaging

摘要

Lipid composition of atherosclerotic plaques is considered to be one of the primary indicators of plaque vulnerability.Therefore, a specific diagnostic or imaging modality that can sensitively evaluate plaques’ necrotic core is highly desirablein atherosclerosis imaging. In this regard, intravascular photoacoustic (IVPA) imaging is an emerging plaque detectiontechnique that provides lipid-specific chemical information from an arterial wall with great optical contrast and longacoustic penetration depth. Within the near-infrared window, a 1210-ğ‘›ğ‘š optical source is usually chosen for IVPAapplications as lipids exhibit a strong absorption peak at that wavelength due to the second overtone of the C-H bondvibration within the lipid molecules. However, other arterial tissues also show some degree of absorption near 1210 ğ‘›ğ‘šand thus generate undesirably interfering PA signals.In this study, a theory of the novel Frequency-Domain Differential Photoacoustic Radar (DPAR) modality is introducedas an interference-free detection technique for accurate and reliable evaluation of vulnerable plaques. By assuming twolow-power continuous-wave (CW) optical sources at ï½1210 ğ‘›ğ‘š and ï½970 ğ‘›ğ‘š in a differential manner, DPAR theoryand the corresponding simulation study suggest a unique imaging modality that can efficiently suppress any undesirableabsorptions and system noise, while dramatically improving PA sensitivity and specificity toward cholesterol contents ofatherosclerotic plaques.