Tunable blood oxygenation in the vascular anatomy of a semi-anthropomorphic photoacoustic breast phantom

Abstract

. Significance : Recovering accurate oxygenation estimations in the breast with quantitative photoacoustic tomography (QPAT) is not straightforward. Accurate light fluence models are required, but the unknown ground truth of the breast makes it difficult to validate them. Phantoms are often used for the validation, but most reported phantoms have a simple architecture. Fluence models developed in these simplistic objects are not accurate for application on the complex tissues of the breast. Aim : We present a sophisticated breast phantom platform for photoacoustic (PA) and ultrasound (US) imaging in general, and specifically for QPAT. The breast phantom is semi-anthropomorphic in distribution of optical and acoustic properties and contains wall-less channels with blood. Approach : 3D printing approaches are used to develop the solid 3D breast phantom from custom polyvinyl chloride plastisol formulations and additives for replicating the tissue optical and acoustic properties. A flow circuit was developed to flush the channels with bovine blood with a controlled oxygen saturation level. To showcase the phantom’s functionality, PA measurements were performed on the phantom with two oxygenation levels. Image reconstructions with and without fluence compensation from Monte Carlo simulations were analyzed for the accuracy of oxygen saturation estimations. Results : We present design aspects of the phantom, demonstrate how it is developed, and present its breast-like appearance in PA and US imaging. The oxygen saturations were estimated in two regions of interest with and without using the fluence models. The fluence compensation positively influenced the estimations in all cases and confirmed that highly accurate fluence models are required to minimize estimation errors. Conclusions : This phantom allows studies to be performed in PA in carefully controlled laboratory settings to validate approaches to recover both qualitative and quantitative features sought after in in-vivo studies. We believe that testing with phantoms of this complexity can streamline the transition of new PA technologies from the laboratory to studies in the clinic.

Suite of 3D test objects for performance assessment of hybrid photoacoustic-ultrasound breast imaging systems

“…36,40 As more systems are nowadays equipped with two or more illumination wavelengths, the demand for test objects for QPA has increased. Recent works on blood vessel phantoms have been reported, [41][42][43] where channels in tissue mimicking materials were flushed with blood. Connecting these vessels to a pump and a flow spectrometer allowed to monitor the blood SO 2 in real time.…”

“…In the previous works, 41,51 we introduced advanced breast-mimicking phantoms for testing PA and QPA algorithms, which will be valuable in phase (iii) of the system testing process. In this work, we introduce test objects to use in phases (i) and (ii).…”

Photoacoustic imaging phantoms for assessment of object detectability and boundary buildup artifacts

“…However, the optical and acoustic properties cannot be tuned independently, and dye diffusion within the TMM has been reported [28] . PVCP TMMs offer high optical and acoustic tunability as well as temporal stability [15] , and complex solid inclusions can also be formed [16] , [29] . However, PVCP requires preparation at high temperatures, potentially limiting the compatible materials used for phantom molding as well as imaging target options.…”

“…Ideally, imaging targets would be solid inclusions made of tunable TMM, which could be prepared with variable shapes and dimensions, and could represent small assemblies of small absorbers (e.g., arterioles and capillaries). Most reported PAI phantoms use tubes or wall-less channels filled with contrast media such as dyes, blood, or nanoparticles [29] , [30] , [40] , [42] . However, tubes are often only available in relatively large sizes representative of larger blood vessels, rather than smaller vasculature.…”

“…Semi-anthropomorphic breast phantoms have been recently reported for PAI [16] , [29] . These phantoms are composed of multiple layers of PVCP breast-mimicking TMMs embedding spherical inclusions and wall-less channels for absorber injection.…”