A Stable Phantom Material for Optical and Acoustic Imaging
June 16th, 2023
This protocol describes the fabrication of a stable, biologically relevant phantom material for optical and acoustic biomedical imaging applications, featuring independently tunable acoustic and optical properties.
Our research is focused on developing new imaging modalities for early cancer detection. In this study in particular, we focused on developing a stable test object, or also called phantom, to validate imaging modalities based on light and or sound. Different resources have been proposed to develop tissue mimicking materials in the acoustic optical regimen.
For example, PVA, hydrogels, polyurethane, or PVCP. This study focuses on a promising new material type based on core polyman oil composition, which overcomes many of the tunability and stability challenges. The field of biomedical optics covers a wide range of imaging modalities that can be applied to some of the key challenges facing medicine today.
Many of the all optical imaging modalities are relatively depth-limited, but we can also couple light with sound through the photoacoustic effect to take advantage of some of the depth penetration benefits of ultrasound. Photoacoustic imaging has shown promise in a wide range of clinical trials, from imaging inflammation to cancer diagnosis. However, quantitative performance assessment remains challenging due to a lack of available phantom materials that can accurately mimic the optical and acoustic properties of tissue and remain stable over time.
Many new optical and photoacoustic imaging systems are being developed, but we lack a standardized reference phantom to validate those systems and to compare their performance. Our material is a promising candidate to fill this gap and support further development and translation of these exciting new techniques into the clinic. In the future, we would like to focus on creating more anatomically-realistic phantom designs and architecture that is suitable to evaluate the performance of different system configurations.
For example, microscopic, mesoscopic, and macroscopic systems, which have different geometries and spatial resolutions. Begin the sonication of 0.15 grams of titanium dioxide and one milliliter of the absorber dye stock solution in 100 milliliters of mineral oil at 90 degrees Celsius for 60 minutes. Let all the components dissolve completely.
Use suitable glassware and silicone oil to create an oil bath and carefully secure it on the hot plate. For uniform heat distribution, place a magnetic stir bar inside the oil bath. Turn on the hot plate, set the heating temperature to 160 degrees Celsius, and adjust the stir to 50 RPM.
Next, weigh 25.14 grams of SEBS and 6.70 grams of LDPE and transfer them into the glass beaker containing the sonicated mineral oil. Place a stir bar in the beaker and transfer it to the center of the oil bath to heat the measured components. When the added polymers float over the mineral oil, manually stir the mineral oil solution using a metal spatula and distribute the floating polymer inside the mineral oil.
Leave the mixture at 160 degrees Celsius for 1.5 hours until all the polymer is dissolved and the solution appears uniformly-mixed, smooth, and homogenous. To begin, place the hot beaker filled with the uniformly-mixed, smooth, and homogenous phantom material solution into the vacuum chamber. Vacuum the samples on the lowest vacuum setting for two to three minutes.
Remove any air bubbles accumulated on the surface using a metal spatula. If air bubbles persist, reheat the mixture and repeat the vacuuming step until complete removal of the air bubbles. In the case of complex-shaped molds, coat the mold with a thin layer of oil before pouring.
Wear heat-resistant gloves, use adequate protective equipment, and carefully pour the solution into a suitable mold without introducing any air bubbles. Once poured, quickly remove any air bubbles from the top of the samples using a metal spatula. Allow the solution to be set overnight at room temperature.
Three representative phantom material designs were created for photoacoustic imaging, targeted for different system designs with different optical illumination and acoustic detection geometries. The successful procedure resulted in smooth and homogenous phantom material preparation without trapped air bubbles, impurities, or artifacts. Insufficient removal of air bubbles and inhomogeneous mixing of base components resulted in inhomogeneities in the resulting photoacoustic image.
Overview
This study presents a protocol for creating a stable phantom material designed for optical and acoustic biomedical imaging. The phantom material features tunable acoustic and optical properties, addressing challenges in validating imaging modalities.
Key Study Components
Area of Science
- Biomedical Imaging
- Optical Imaging
- Acoustic Imaging
Background
- Development of tissue-mimicking materials is crucial for validating imaging techniques.
- Existing materials often lack stability and tunability.
- Photoacoustic imaging combines light and sound for deeper tissue penetration.
- Standardized reference phantoms are needed for performance assessment of imaging systems.
Purpose of Study
- To fabricate a stable phantom material for optical and acoustic imaging.
- To provide a solution for the lack of reliable phantom materials in biomedical optics.
- To support the development and translation of new imaging techniques into clinical settings.
Methods Used
- Sonication of titanium dioxide and dye in mineral oil.
- Heating and mixing polymers (SEBS and LDPE) in the sonicated solution.
- Vacuum removal of air bubbles from the mixture.
- Pouring the solution into molds and allowing it to set at room temperature.
Main Results
- Successful preparation of a smooth and homogeneous phantom material.
- Three distinct phantom designs were created for different imaging systems.
- The material demonstrated stability and tunability for optical and acoustic properties.
- Addressed challenges in existing phantom materials for photoacoustic imaging.
Conclusions
- The developed phantom material is a promising candidate for validating imaging modalities.
- Future work will focus on creating anatomically-realistic designs.
- This research supports the advancement of imaging techniques in clinical applications.
