Abstract:A real-time 512-element photoacoustic tomography system for small animal imaging using a ring ultrasound array has been developed. The system, based upon a 5 MHz transducer array formed along a 50 mm circular aperture, achieves sub-200 micron lateral resolution over a 2 cm disk-shaped region. Corresponding elevation resolutions of 0.6 to 2.5 mm over the central volume enable depth-resolved 3D tomographic imaging with linear translation. Using 8:1 electronic multiplexing, imaging at up to 8 frame/sec is demonstrated for both dynamic phantoms and in vivo mouse and brain samples. The real-time, full 2D tomographic capability of the system paves the way for functional photoacoustic tomographic imaging studies in small animals with sub-second time frame. ©2009 Optical Society of America

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Abstract. We present systematic characterization of a photoacoustic imaging system optimized for rapid, high-resolution tomographic imaging of small animals. The system is based on a 128-element ultrasonic transducer array with a 5-MHz center frequency and 80% bandwidth shaped to a quarter circle of 25 mm radius. A 16-channel dataacquisition module and dedicated channel detection electronics enable capture of a 90-deg field-of-view image in less than 1 s and a complete 360-deg scan using sample rotation within 15 s. Measurements on cylindrical phantom targets demonstrate a resolution of better than 200 m and high-sensitivity detection of 580-m blood tubing to depths greater than 3 cm in a turbid medium with reduced scattering coefficient s Ј=7.8 cm −1 . The system is used to systematically investigate the effects of target size, orientation, and geometry on tomographic imaging. As a demonstration of these effects and the system imaging capabilities, we present tomographic photoacoustic images of the brain vasculature of an ex vivo mouse with varying measurement aperture. For the first time, according to our knowledge, resolution of sub-200-m vessels with an overlying turbid medium of greater than 2 cm depth is demonstrated using only intrinsic biological contrast.

A series of high polymer content phosphoric acid-doped m/p-polybenzimidazole (PBI) copolymer membranes were prepared via the poly­(phosphoric acid) (PPA) process. These copolymer membranes showed much higher solubility in solution (7–10 wt %) compared to the homopolymer para-PBI (typically <3.5 wt %), which translated to higher polymer solids content in the PPA-processed doped membranes. Concurrent with these changes, the compressive creep compliance (J) decreased from approximately 1 × 10–5 to <2 × 10–6 Pa–1. These membranes exhibited high proton conductivities, >150 mS/cm at typical operating temperatures of 160–200 °C, and showed exceptional low voltage decay, ∼0.67 μV/h when tested at 160 °C for more than 2 years.

We report a frequency domain optical tomography system utilizing three RF modulation frequencies, which are optimized for probing breast lesions of different size located at different depths. A real-time co-registered ultrasound scanner is used to provide on-site estimation of lesion size and location. Based on the lesion information, an optimal light modulation frequency can be selected, which may yield more accurate estimates of lesion angiogenesis and hypoxia. Phantom experiments have demonstrated that a high modulation frequency, such as 350Mhz, is preferable for probing small lesions closer to the surface while a low modulation frequency, such as 50Mhz, is desirable for imaging deeper and larger lesions. A clinical example of a large invasive carcinoma is presented to demonstrate the application of this novel technique.