Intravascular photoacoustic imaging

A catheter-based imaging apparatus comprising:

• a catheter having a proximal end and a distal end;
• an optical emitter configured to emit optical excitation signals from a distal portion of the catheter;
• a first transducer and a second transducer, wherein:
• the first transducer has a peak detection sensitivity in a lower frequency range of a first frequency to a second frequency;
• the second transducer has a peak detection sensitivity in a higher frequency range of a third frequency to a fourth frequency, the third frequency being no less than the second frequency, and
• the catheter-based imaging apparatus is configured for:
• (a) transmission of acoustic excitation signals from the distal portion of the catheter with the second transducer;
• (b) detection of a photoacoustic response signal with the first transducer, the photoacoustic response signals being from an object of interest at or near to the distal portion of the catheter and excited by the optical excitation signals and
• (c) detection of imaging signals with the second transducer, the imaging signals comprising reflections of the acoustic excitation signals from the object of interest wherein the first transducer is configured to be operable at a frequency range which encompasses a lower receive frequency at least as low as 10 MHz and the second transducer is configured to be operable at a frequency range that encompasses a higher receive frequency at least as high as 35 MHz.