Fig. 1

Fig. 1

(A) Schematic showing the RThAM imaging principle. We used silicone oil (Si oil) as dielectric medium in an open transmission line (TxLine) and coupled an RF field [E⃑(t)] to the biological sample (supported by a tubing of ∅1 mm) to excite thermoacoustic wave (dashed red circles). The thermoacoustic wave is coupled by deionized water (DI H₂O) contained by PE film to an ultrasound (US) transducer. Resin coating to the copper and an extra PE film are applied to avoid direct contact between the sample and TxLine. (B and C) RThAM image of two copper wires (diameter, 50 μm) formed (B) by MIP in the xy plane and (C) by a slice (indicated by the dotted gray line) in the yz plane. (D) Line profiles showing a FWHM of 23 μm in the z axis (axial) and 33 μm in the y axis (lateral) along the solid blue and dashed arrows indicated in (C), respectively. (E) A temporal RThAM signal (black curve) showing an SNR of 34 dB and its Fourier transform (FFT; blue curve) showing the frequency components and a central frequency at 47 MHz.