Quantitative photoacoustic estimates of intervascular blood oxygenation differences using linear unmixing

Abstract

The linear unmixing technique is an appealing method for estimating blood oxygen saturation (sO2) from multiwavelength photoacoustic tomography images, as estimates can be acquired with a straightforward matrix inversion. However, the technique can only rarely provide accurate estimates in vivo, as it requires that the light fluence at the voxels of interest is constant with wavelength. One way to extend the set of cases where accurate information related to sO2 can be acquired with the technique is by taking the difference in sO2 estimates between vessels. Assuming images are perfectly reconstructed, the intervascular difference in sO2 estimates is accurate if the error in the estimates due to the wavelength dependence of the fluence is identical for both. An in silico study was performed to uncover what kinds of conditions may give rise to accurate sO2 differences for a vessel pair. Basic criteria were formulated in simple tissue models consisting of a pair of vessels immersed in two-layer skin models. To assess whether these criteria might still be valid in more realistic imaging scenarios, the sO2 difference was estimated for vessels in more complex tissue models.

Size-tunable ICG-based contrast agent platform for targeted near-infrared photoacoustic imaging.

“…To further demonstrate the clinical translation potential of the JAAZ particles, an in vivo pilot study was conducted on the commercially available small animal PAI system TriTom™ ( Fig. 6 A) [45] , [46] , [47] . We first acquired multiwavelength images of microcuvette tubes containing 0.4 mM of ICG dye or RGD-JAAZ particles to evaluate the PA spectra of both contrast agents.…”

“…6 E). Molecular maps were generated from a linear spectral unmixing of the multiwavelength PA images using previously reported spectra for hemoglobin and the measured spectra of the RGD-JAAZ particles at their injection concentration [47] , [48] .

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Size-tunable ICG-based contrast agent platform for targeted near-infrared photoacoustic imaging

“…Additionally, the molecular maps of oxyhemoglobin, deoxyhemoglobin, and RGD-JAAZ particles show the biodistribution of the contrast agent is restricted to the vasculature and blood-rich tissues such as the liver and spleen (Figure 6E). Molecular maps were generated from a linear spectral unmixing of the multiwavelength PA images using previously reported spectra for hemoglobin and the measured spectra of the RGD-JAAZ particles at their injection concentration [45,46].…”

“…To further demonstrate the clinical translation potential of the JAAZ particles, an in vivo pilot study was conducted on the commercially available small animal PAI system TriTom™ (Figure 6A) [43][44][45]. We first acquired multiwavelength images of microcuvette tubes containing 0.4 mM of ICG dye or RGD-JAAZ particles to evaluate the PA spectra of both contrast agents.…”

Detection of collagen by multi-wavelength photoacoustic analysis as a biomarker for bone health assessment

“…In our previous clinical study on the human calcaneus bone, wavelength-dependent light attenuation was partially addressed based on the bone model [ 25 ]. Previous studies from other groups have also indicated that spectral coloring can be eliminated using model-based or machine-learning-based methods [ [41] , [42] , [43] , [44] , [45] , [46] , [47] ]. Therefore, in future clinical studies, PA absorption curves affected by spectral coloring should be further studied and corrected.…”