Assessment of the enhancement potential of Halloysite Nanotubes for echographic imaging

Abstract

Halloysite Nanotubes (HNTs) are nanomaterials composed of double layered aluminosilicate minerals with a predominantly hollow tubular structure in submicron range. HNTs are characterized by a wide range of applications in anticancer therapy, sustained agent delivery, being particularly interesting because of their tunable release rates and fast adsorption rates. However systematic investigations of their acoustic properties are still poorly documented. This paper shows a quantitative assessment of the effectiveness of HNTs as scatterers at conventional ultrasonic frequencies (5.7 -7 MHz) in low range of concentrations (1.5-5 mg/mL). Different samples of HNT (diameter: 40-50 nm; length: 0.5 to 2 microns, empty lumen diameter: 15-20 nm) containing agarose gel were imaged through a commercially available echographic system and acquired data were processed through a dedicated prototypal platform in order to extract the average ultrasonic signal amplitude associated to the considered sample. Relationships have been established among backscatter, HNT concentration and the employed echographic frequency. Our results demonstrated that improvement in image backscatter could be achieved incrementing HNT concentration, determining a non-linear signal enhancement due to the fact that they are poly-disperse in length. On the other hand the effect of different echographic frequencies used was almost constant at all concentrations, specifically using higher values of echographic frequency allows yielding a signal enhanced of a factor 1.75±0.26.

Multiparametric Evaluation of the Acoustic Behavior of Halloysite Nanotubes for Medical Echographic Image Enhancement

“…2 shows how the average backscatter signal amplitude values, measured using different HNT concentrations, are affected by varying power of the emitted echographic signal with both employed ultrasonic frequencies. The proportionality between the HNT concentration and the measured backscatter signal was found at all tested values of power of the emitted signal, for the higher insonification diagnostic frequency employed, while, using 5.7 MHz, values of backscatter signal obtained using 1.5-mg/mL concentrated HNTs resulted always higher than those obtained with the concentration 3 mg/mL supporting our previous findings [11].…”

“…Therefore, this paper extends our previous investigations, about a preliminary characterization of ultrasonic HNT acoustic behavior [11], to additional two levels of power of the emitted signal, one higher and the other lower than the previously adopted value, and compares with the corresponding results with those related to the intermediate level, to characterize the scattering behavior of HNTs under different parametric configurations. Therefore, our aim is to provide complete indications for the safe and effective use of HNTs as echographic image enhancement agent implementing repeatable experimental conditions and documenting the diagnostic performance with regards to the employed concentrations and to the mechanical parameters involved in the echographic examination with different employed frequency.…”

“…For these reasons, echographic pulses used in conjunction with the most commonly employed ultrasonic contrast agent have been optimized over the years [22], [23] to complement the continuous advances in US-based diagnostic techniques [24]- [26]. Nonetheless, the acoustic potential of HNTs as US contrast agent is still scarcely explored by diagnostic imaging relevant literature [11]. Therefore, we tested in our framework three values of power of the emitted signal, quantified as percentage of the maximum power achievable as indicated on the device, and two diagnostic frequencies on different HNT containing tissue-mimicking samples to give indication with regards to the adopted parametric settings.…”

“…Subsequently, different amounts of HNTs (purified dehydrated HNTs, obtained from Applied Minerals, Inc.) were added to the agarose solution in separate vials, sonicating the mixture for 30 s to complete mixture. The experimental samples were obtained in 2-mL Eppendorf tube, reproducing the configuration optimized in our previous work [11]. On a base layer (corresponding to 0.5 mL) of pure agarose gel, 1 mL of HNT containing solution was quickly poured into the Eppendorf tube laced in freezer for 2 min to ensure quick Fig.…”

Modeling and Designing a Full Beamformer for Acoustic Sensing and Measurement

“…The beamformer linearly combines the different origins in spatial regions, this spatial diversity can be used for the aforementioned reason, utilizing a spatial filtering in receiving unit. With beamforming, we indicate a technique by means of which we carry out a versatile form of spatial filtering [4][5] [6], to separate signals that are spectrally superposed but that they come from diverse spatial directions [7] [8] [9]. Let us assume that the incident signal, on the array of sensors, is a complex plane wave, with DOA θ and frequency ω.…”