Photoacoustic and high-frequency power Doppler ultrasound biomicroscopy: a comparative study

Abstract

Abstract. Both photoacoustic imaging and power Doppler ultrasound are capable of producing images of the vasculature of living subjects, however, the contrast mechanisms of the two modalities are very different. We present a quantitative and objective comparison of the two methods using phantom data, highlighting relative merits and shortcomings. An imaging system for combined photoacoustic and highfrequency power Doppler ultrasound microscopy is presented. This system uses a swept-scan 25-MHz ultrasound transducer with confocal dark-field laser illumination optics. A pulse-sequencer enables ultrasonic and laser pulses to be interlaced so that photoacoustic and power Doppler ultrasound images can be coregistered. Experiments are performed on flow phantoms with various combinations of vessel size, flow velocity, and optical wavelength. For the task of blood volume detection, power Doppler is seen to be advantageous for large vessels and high flow speeds. For small vessels with low flow speeds, photoacoustic imaging is seen to be more effective than power Doppler at the detection of blood as quantified by receiver operating characteristic analysis. A combination of the two modes could provide improved estimates of fractional blood volume in comparison with either mode used alone.

Blood oxygen flux estimation with a combined photoacoustic and high-frequency ultrasound microscopy system: a phantom study

“…Readers are referred to our previous work 16,17 for specific details about the instrumentations and explanations on light delivery probe and imaging procedures. In brief, a digital-input-output (DIO) card (NI PCI-6542, National Instruments, Inc., USA) is used to generate a pulse sequence that is sent to the ultrasound pulser/receiver (5073PR, Panametrics; Waltham, Massachusetts) and/or laser to enable different imaging modes.…”

“…We recently developed a combined photoacoustic and high-frequency ultrasound microscopy system with a swept-scan 25-MHz transducer and confocal dark-field laser illumination optics. 16,17 Previously we demonstrated the use of this system for interlaced photoacoustic and power Doppler imaging modes. In this article, along with our recent conference publication, 18 we add color Doppler flow imaging to our system's capabilities.…”

“…For small vessels with low flow speeds, which are hard to detect by Doppler ultrasound, our previous work shows that photoacoustic imaging is more effective than power Doppler for the detection of blood. 16 The long-term goal of our research is to develop photoacoustic and ultrasonic imaging methods for noninvasive estimation of MRO 2 in vivo. We recently developed a combined photoacoustic and high-frequency ultrasound microscopy system with a swept-scan 25-MHz transducer and confocal dark-field laser illumination optics.…”

Estimation of cerebral metabolic rate of oxygen consumption using combined multiwavelength photoacoustic microscopy and Doppler microultrasound

“…The construction of the cornstarch-gelatin phantom can be referred to our previous work. 31 Under the assumption of fully developed parabolic flow, we observed excellent consistency and sensitivity to flow velocities of several mm∕s, sufficient for in vivo flow estimation in murine carotid artery and jugular veins. The correlation of determination R 2 of linear least-square fitting is 0.99 with a slope of 0.94 and a zero-offset of 4.2 mm∕s.…”

“…Different from flow velocity estimation, the intensity of power Doppler image is proportional to the number of scatterers moving within a vascular volume rather than the frequency shifts they generate, 30 which makes it more sensitive to blood flow detection and independent of Doppler angles. 31 Since tissues surrounding blood vessels often generate much stronger scattered signals than moving blood, clutter filtering is necessary before velocity estimation and power calculations. Here, an adaptive eigenfilter was designed and implemented based on the statistics of the clutter and tissue movement.…”