Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging

Abstract

Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP's acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be [Formula: see text] = 1.01 ± 0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated.

Sulfates as chromophores for multiwavelength photoacoustic imaging phantoms

“…Despite recent advances on the study of phantom matrix materials for general photoacoustic (PA) system characterization and quality control, [8][9][10][11][12] for multiwavelength and quantitative PAI purposes further efforts are needed, with one of the crucial issues being finding suitable chromophores. 13,14 It is essential for these to be well-characterized, well-behaved, and stable. They should also exhibit spectral variation and if possible be tissue-realistic, although the extent to which this is necessary will depend on the application.…”

Whole-body multispetral photoacoustic imaging of adult zebrafish

“…Through the utilization of a multispectral strategy, we were able to capture additional tissues and structures inside the zebrafish. In addition, by employing quantitative reconstruction methods, such as quantitative photoacoustic tomography [29,30], we can derive the concentrations of different compositions inside the major organs. Although, our study demonstrates the great potential of photoacoustic imaging in the study of adult zebrafish, further improvements must be made to optimize both the imaging system and experimental procedures.…”

Cylindrical illumination with angular coupling for whole-prostate photoacoustic tomography

“…For the acoustic properties, the speed of sound in human prostates is 1529 m/s, while the attenuation coefficient and slope at 5.0 MHz is 2.35 dB/cm and 0.72 dB/cm/MHz [68]. Based on these properties, 8% type A, 300-Bloom porcine gelatin (G2500, Sigma-Aldrich, St. Louis, MO, USA) was chosen for its similar acoustic properties, while being optically transparent [69,70]. To modify the optical properties of the phantom, Intralipid fat emulsion solution and black India ink have been well studied for tuning the optical properties of tissue-mimicking phantoms [69,71].…”