A real-time photoacoustic tomography system for small animals

Abstract

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

Noninvasive High-Speed Photoacoustic Tomography of Cerebral Hemodynamics in Awake-Moving Rats

“…(A) Statistic analysis (mean ± s.e.m.) of hemodynamic response percent intensity change of regions of interest (ROIs) for eight rats (four anesthetized and four in awake-moving state); Left panel, 60 seconds after pentylenetetrazol (PTZ) injection relative to baseline (anesthetized state, 3.75 ± 0.49%, 4.98 ± 1%, 1.73 ± 1.66%, 1.48 ± 3.11%, and 8.44 ± 1.27% for superior sagittal sinus (SSS), V1, V2, V3, and V4, respectively; awake-moving state, 8.29 ± 3.69%, 2.29 ± 2.41%, − 1.61 ± 5.17%, − 3.6 ± 2.11%, and 6.8 ± 6.82% for SSS, V1, V2, V3, and V4, respectively; ANOVA, P o0.05); Right panel, from PTZ injection at the 180th second to the 600th second relative to the baseline (anesthetized state, 10.16 ± 2.28%, 9.28 ± 1.95%, 4.38 ± 2.6%, 2.00 ± 1.12%, and 12.02 ± 1.43% for SSS, V1, V2, V3, and V4, respectively; awake-moving state, 22. elevation resolution of 0.6 to 2 mm within the imaging 'disk' was reported in Gamelin et al 9 ). An alternative method is to reduce the size of transducer element along the elevation dimension (e.g., to 1 mm), but this may reduce the detection sensitivity.…”

“…Due to the reduced number of transducer element, wPAT's spatial resolution is little worse than the current array-based PAT systems. 9,15 However, cerebral hemodynamic responses of different regions were successfully detected and imaged by wPAT. The image quality (X-Y spatial resolution) of wPAT can be improved by increasing the number of elements (~100 μm radial resolution was reported by using a 512-element transducer array 51 ) or using transducers with higher central frequency and wide bandwidth (30 μm image resolution was reported with a 20-MHz central frequency transducer having a bandwidth ranging from 50% to 80% 52 ).…”

“…12 Transducer arraybased PAT is capable of noninvasively imaging the animal's whole brain with a high temporal resolution (several frames per second), and possesses superior spatial resolution (~100 μm) as well. 9,[13][14][15] While these advantages make array-based PAT suitable for cerebral hemodynamics imaging, current array-based PAT systems are bulky, requiring subjects to be anesthetized and fixed during experiments, which might disrupt the neurochemistry and animal's perception to stimulation. 9,14,16 For example, anesthetics can modify the dopamine D 1 receptor binding in rat brain 17 and anesthesia also affects the neuronal excitability, vascular reactivity, and other baseline physiologies.…”

“…9,[13][14][15] While these advantages make array-based PAT suitable for cerebral hemodynamics imaging, current array-based PAT systems are bulky, requiring subjects to be anesthetized and fixed during experiments, which might disrupt the neurochemistry and animal's perception to stimulation. 9,14,16 For example, anesthetics can modify the dopamine D 1 receptor binding in rat brain 17 and anesthesia also affects the neuronal excitability, vascular reactivity, and other baseline physiologies. 18 Therefore, high-speed, noninvasive PAT imaging of the whole brain in awake-behaving animals is highly desirable.…”

Hybrid photoacoustic and ultrasound section imaging with optical ultrasound detection

“…For this purpose, it is sufficient to generate one or several two-dimensional tomographic images by focusing into selected slices. Such section images have been obtained either with a single detector scanning around a sample [26][27][28][29] or with a circular array [30,31]. In this study, in order to take advantage of the favorable properties of the optical detector and to implement the laser US imaging capability, we present a section imaging setup consisting of a single, optimized detector.…”