Development and validation of a gel wax phantom to evaluate geometric accuracy and measurement of a hyperechoic target diameter in diagnostic ultrasound imaging.

Diagnostic ultrasound (US) scanners are generally evaluated using proprietary quality assurance (QA) phantoms, but their prohibitively high cost may prevent organizations to perform the necessary tests. This study aimed to develop a low-cost gel wax phantom with targets to determine the lateral and axial resolution and diameter of a hyperechoic target in an US scanner. The acoustic property (AP) of gel wax, which includes the speed of sound (cus), acoustic impedance (Z), and attenuation coefficient (µ), were determined for multiple transducers operating at 2.25, 5, 10, 15, and 30 MHz. These results were compared to the AP of soft tissue. Two polytetrafluoroethylene (PTFE) rectangular frames with holes separated by 5, 10, and 20 mm were constructed. Nylon filaments and stainless-steel disc (SS disc) (diameter = 16.8 mm) were threaded through the frames and suitably placed in gel wax to obtain orthogonal targets in the phantom. The target dimensions obtained from computerized tomography (CT) and US images of the phantom were compared for phantom validation. The average cus=1431.4 m/s, mass density ρ = 0.87 g/cm3, Z = 1.24 MRayls, and µ ranged from 0.7 to 0.98 dB/cm/MHz for gel wax at 22 °C. The US image measurement exhibited a maximum error in determining the diameter of the SS disc, resulting in a value of 18 mm instead of its actual value of 16.8 mm. The phantom volume decreased by 1.8% in 62 weeks. The present phantom is affordable, stable, customizable, and can be used to evaluate diagnostic US scanners across multiple centers.

Novel class of water-soluble phosphonate silver cluster assembled material for efficient photoelectric sensing and photoacoustic imaging.

Owing to the atomic precession and exotic photophysical properties, silver cluster assembled materials (CAMs) have been explored for use as functional nanomaterials in recent years. Although a small number of thiolate protected silver CAMs have previously been investigated, the synthesis of thiol-free analogues and their solubility remain challenging. Here, the structure-property correlation of a newly synthesized one-dimensional phenyl phosphonate protected [Ag2(PhPO3H)2(apy)2], (in which, 4,4'-azopyridine = apy) CAM is demonstrated. The multifunctional surface protecting ligand is strategically attached to the core for the first time to tailor the solubility, structural stability and charge transfer mechanism. The small size of the cluster building blocks, along with the choice of organic linker molecules, efficiently stabilize the structure via intra-chain π-π stacking while inter-chains π-π interactions create a two-dimensional supramolecular architecture. The advantageous band structure associated with the charge transfer phenomenon and the high structural stability of the material are guided to explore the sustainable photoresponsive character of this CAM, resulting in the generation of an 82 nA photocurrent. Additionally, the unprecedented water solubility, which is very rare for this class of material, provides opportunities for use in biomedical imaging applications. The measured photoacoustic signal strength confirms the blood vessel mimicking capabilities of the portrayed material at a depth of approximately 3 mm inside chicken breast tissue.