Date of download: 9/18/2016 Copyright © 2016 SPIE. All rights reserved. (a) MAP PAM image of blood vessels of a mouse ear acquired at a wavelength of 610 nm. The vessel indicated by the arrow in the white rectangle was monitored to calculate the methemoglobin level during the induction and self-recovery periods. (b1–b4) Spatial distribution of methemoglobin percentages measured every 35 min after the intravenous injection of sodium nitrite solution. (c) Time course of methemoglobin and oxyhemoglobin average percentages before and after intravenous injection of sodium nitrite solution. Data are presented as the mean±standard error (based on four measurements). Figure Legend: From: Noninvasive photoacoustic microscopy of methemoglobin in vivo J. Biomed. Opt. 2015;20(3): doi: /1.JBO

Date of download: 9/18/2016 Copyright © 2016 SPIE. All rights reserved. (a) Maximum-amplitude projection (MAP) PAM images of tubes filled with different concentrations of methemoglobin in lysed bovine blood at 610, 620, and 630 nm. (b) Methemoglobin distribution image calculated from the multiwavelength PAM images. The average methemoglobin percentages from top to bottom are 23, 41, 58, 76, and 89%. (c) The photoacoustically measured methemoglobin and oxyhemoglobin percentage averaged within each tube versus the preset value. The preset percentages were measured with a spectrophotometer. Circles: photoacoustically versus spectrophotometrically measured methemoglobin percentages. Line: ideal fit if the photoacoustically measured and preset methemoglobin percentages were identical. Data are presented as the mean±standard error (based on four measurements). Figure Legend: From: Noninvasive photoacoustic microscopy of methemoglobin in vivo J. Biomed. Opt. 2015;20(3): doi: /1.JBO

Date of download: 9/18/2016 Copyright © 2016 SPIE. All rights reserved. (a) Molar extinction coefficients of oxyhemoglobin (OxyHb), deoxyhemoglobin (DeoxyHb), and methemoglobin (MetHb) versus optical wavelength. (b) Absorption coefficient of blood samples that are further diluted 20 times measured with spectrophotometry. 20, 40, 60, and 80% refer to the methemoglobin percentage of the total hemoglobin. (c) Photoacoustic signals of blood samples measured at three optical wavelengths: 610, 620, and 630 nm. (d) Methemoglobin percentage of each sample measured using PAM versus the preset value. Circles: photoacoustically measured methemoglobin percentages. Line: ideal fit if the photoacoustically measured and preset methemoglobin percentages were identical. Figure Legend: From: Noninvasive photoacoustic microscopy of methemoglobin in vivo J. Biomed. Opt. 2015;20(3): doi: /1.JBO

Date of download: 9/18/2016 Copyright © 2016 SPIE. All rights reserved. Schematic of photoacoustic microscopy (PAM) system. AT, attenuator; BS, beam splitter; CorL, correction lens; EP, eyepiece; OL, objective lens; PD, photodiode; PH, pinhole; RAP, right-angle prism; RhP, rhomboid prism; SOL, silicone oil layer; UT, ultrasonic transducer; WT, water tank. Figure Legend: From: Noninvasive photoacoustic microscopy of methemoglobin in vivo J. Biomed. Opt. 2015;20(3): doi: /1.JBO