All US and PA scans were performed on a VisualSonics Vevo LAZR-X
Imaging System (VisualSonics, Inc., Toronto, Canada) as previously
described.25 (link)In vitro phantom PAI was performed using a Vevo PHANTOM imaging chamber (VisualSonics,
Inc.). NP samples were loaded into PE-20 medical polyethylene tubing
using a syringe with a 27 gauge needle. PA spectra were analyzed under
Spectro Mode scan from 680 to 970 nm with a step size of 5 nm.
During PAI, a tunable laser (680–970 nm) was used.25 (link) Pulse-to-pulse energy fluctuation was continuously
monitored, and variations exceeding 25% resulted in the recalibration
of the system before further imaging. Multiwavelength PAI was acquired
at a frequency of 21 MHz (MX250, VisualSonics, Inc.) combined with
a high-efficiency Vevo Optical Fiber (medium). Multispectral and volumetric
photoacoustic images were exported for offline analysis using Vevo
LAB. In the multiwavelength PA mode, PAIs at 680, 804, 850, 900, 924,
and 954 nm created images of oxygenated hemoglobin, deoxygenated hemoglobin,
and AuNR@mSiO2@Gd2O(CO3)2, which were coregistered with gray-scale B-mode imaging. Within
an ROI, quantifications of the PA average from AuNR@mSiO2@Gd2O(CO3)2 and oxygen saturation
were achieved using the Spectra unmixing tool (VisualSonics, Inc.)
and the OxyZated tool (VisualSonics, Inc.), respectively.
Imaging System (VisualSonics, Inc., Toronto, Canada) as previously
described.25 (link)In vitro phantom PAI was performed using a Vevo PHANTOM imaging chamber (VisualSonics,
Inc.). NP samples were loaded into PE-20 medical polyethylene tubing
using a syringe with a 27 gauge needle. PA spectra were analyzed under
Spectro Mode scan from 680 to 970 nm with a step size of 5 nm.
During PAI, a tunable laser (680–970 nm) was used.25 (link) Pulse-to-pulse energy fluctuation was continuously
monitored, and variations exceeding 25% resulted in the recalibration
of the system before further imaging. Multiwavelength PAI was acquired
at a frequency of 21 MHz (MX250, VisualSonics, Inc.) combined with
a high-efficiency Vevo Optical Fiber (medium). Multispectral and volumetric
photoacoustic images were exported for offline analysis using Vevo
LAB. In the multiwavelength PA mode, PAIs at 680, 804, 850, 900, 924,
and 954 nm created images of oxygenated hemoglobin, deoxygenated hemoglobin,
and AuNR@mSiO2@Gd2O(CO3)2, which were coregistered with gray-scale B-mode imaging. Within
an ROI, quantifications of the PA average from AuNR@mSiO2@Gd2O(CO3)2 and oxygen saturation
were achieved using the Spectra unmixing tool (VisualSonics, Inc.)
and the OxyZated tool (VisualSonics, Inc.), respectively.