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

Abstract

Abstract. The metabolic rate of oxygen consumption, an important indicator of tissue metabolism, can be expressed as the change of net blood oxygen flux into and out of a tissue region per 100 g of tissue. In this work, we propose a photoacoustic and Doppler ultrasound method for imaging local blood oxygen flux of a single vessel. An imaging system for combined photoacoustic and high-frequency 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 Doppler ultrasound images are co-registered. Since the mean flow speed can be measured by color Doppler ultrasound, the vessel cross-sectional area can be measured by power Doppler or structural photoacoustic imaging, and multi-wavelength photoacoustic methods can be used to estimate oxygen saturation (sO 2 ) and total concentration of haemoglobin (C Hb ), all of the parameters necessary for oxygen flux estimation can be provided. The accuracy of the flow speed and sO 2 estimation has been investigated. In vitro sheep blood phantom experiments have been performed at different sO 2 levels and mean flow speeds. Blood oxygen flux has been estimated, and the uncertainty of the measurement has been quantified.

Wavelength‐Modulated Differential Photoacoustic Spectroscopy (WM‐DPAS) for noninvasive early cancer detection and tissue hypoxia monitoring

“…[26] PACT; pulsed laser with 680 nm modulation amplitude 2.51%/% StO 2 in-vivo mouse [14] PAS; pulsed laser with 760 nm modulation amplitude 1.06%/% StO 2 in-vivo human blood [27] PAM; pulsed laser with 570 nm modulation amplitude 0.12%/% StO 2 in-vivo Phantom (cornstarch + gelatin)…”

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

“…A peripheral component interconnect (PCI) motion card (NI7350, National Instruments Inc., Texas) was used to control a highprecision three-axis motion stage with three integrated stepper motors (23Y002D-LW8, Anaheim Automation, California). Fast scanning was accomplished with a voice-coil actuator as previously described 25,26 while vertical and elevational translation were accomplished using the stepper motors.…”

“…25 Pulsed color Doppler ultrasound was used for flow velocity estimation. A sequence of modulated ultrasound pulses was transmitted along a certain Doppler angle, and the flow velocities were calculated from detected phase shifts in received echoes.…”

“…We previously demonstrated oxygen flux estimation in a phantom study using such a system. 25 In this paper, the CMRO 2 is estimated in vivo by combining the measurements of arterial and venous oxygen saturation and flow rate of the internal jugular vein.…”

Fully motorized optical-resolution photoacoustic microscopy

“…The high detection efficiency of intrinsic optical absorbers (e.g., oxy-hemoglobin (HbO2) and deoxy-hemoglobin (HbR) [3,4]) enables OR-PAM to provide label-free, high-resolution [5,6], functional imaging of fine structures [7]. OR-PAM has already demonstrated broad biomedical applications in the fields of neurology [8], ophthalmology [9][10][11][12], and vascular biology [13].…”