Abstract
Established medical imaging technologies such as magnetic resonance imaging and computed tomography rely on well-validated tissue-simulating phantoms for standardized testing of device image quality. The availability of high-quality phantoms for optical-acoustic diagnostics such as photoacoustic tomography (PAT) will facilitate standardization and clinical translation of these emerging approaches. Materials used in prior PAT phantoms do not provide a suitable combination of long-term stability and realistic acoustic and optical properties. Therefore, we have investigated the use of custom polyvinyl chloride plastisol (PVCP) formulations for imaging phantoms and identified a dual-plasticizer approach that provides biologically relevant ranges of relevant properties. Speed of sound and acoustic attenuation were determined over a frequency range of 4 to 9 MHz and optical absorption and scattering over a wavelength range of 400 to 1100 nm. We present characterization of several PVCP formulations, including one designed to mimic breast tissue. This material is used to construct a phantom comprised of an array of cylindrical, hemoglobin-filled inclusions for evaluation of penetration depth. Measurements with a custom near-infrared PAT imager provide quantitative and qualitative comparisons of phantom and tissue images. Results indicate that our PVCP material is uniquely suitable for PAT system image quality evaluation and may provide a practical tool for device validation and intercomparison.
Highlights
1.1 Photoacoustic TomographyPhotoacoustic tomography (PAT) is an emerging noninvasive imaging modality that combines pulsed or rapidly modulated optical irradiation with acoustic sensing to achieve greater penetration depths than pure optical imaging techniques.[1]
We focus on simulating breast tissue properties, given the potential of photoacoustic tomography (PAT) for mammography applications.[6,17,18,19,20,21]
We can conclude that commercial polyvinyl chloride plastisol (PVCP), even with commercially available additives, does not possess adequately tunable acoustic properties for tissue phantoms
Summary
1.1 Photoacoustic TomographyPhotoacoustic tomography (PAT) is an emerging noninvasive imaging modality that combines pulsed or rapidly modulated optical irradiation with acoustic sensing to achieve greater penetration depths than pure optical imaging techniques.[1]. PAT systems reported in the literature show a wide variation in configuration, including sensor geometry, illumination geometry, optical wavelength, and acoustic frequency band. Many of these systems are bimodal, capable of providing coregistered PAT and B-mode ultrasound imaging. Based on this variation in system operating parameters, a wide variation in device performance is expected. Standardized test methods and materials are needed in order to enable objective, quantitative characterization of PAT system performance. Phantombased test methods are commonly used in medical imaging
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