Dual-Mode Photoacoustic and Ultrasound Endoscope for Internal Organ Imaging
This dual-mode endoscopic probe integrates photoacoustic and ultrasound imaging in a single 3.8 mm diameter package for simultaneous, spatially co-registered functional and anatomical imaging of internal organs. The probe uses a 36 MHz LiNbO₃ single-crystal transducer with a central hole for optical fiber delivery, and a rotating mirror for circumferential scanning. Photoacoustic imaging provides optical absorption contrast—enabling visualization of blood vessels, hemoglobin concentration, and oxygen saturation (sO₂)—while ultrasound provides acoustic reflectance contrast for tissue morphology. In vivo imaging of rabbit esophagus and rat colon demonstrates transesophageal lung and trachea imaging, colon wall vasculature, and contrast-enhanced lymph node mapping with Evans blue dye. Lymph vessels as small as 1 mm are resolved.
Parameter | Value |
|---|---|
Probe Outer Diameter | 3.8 mm |
Rigid Distal Length | 38 mm |
Transducer Material | LiNbO₃ single crystal |
Center Frequency | 36 MHz |
Fractional Bandwidth | 65% |
Transducer Aperture | 2.6 mm |
Central Hole Diameter | 0.5 mm |
Scanning Method | Rotating mirror (~4 Hz) |
Angular FOV | 270° (360° with reinsertion) |
Pullback Speed | ~200 μm/s |
Imaging Modes | Photoacoustic (PA), Ultrasound (US), Dual‑wavelength PA |
PA Wavelengths Demonstrated | 562 nm, 584 nm, 523 nm, 640 nm |
Functional Contrast | Total hemoglobin, sO₂, exogenous dye (Evans blue) |
Minimum Resolved Lymph Vessel | ~1 mm |
In Vivo Targets | Rabbit esophagus, lung, trachea; rat colon, lymph nodes |
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