Pharmacokinetics of Two Nanoemulsion Formulations of Δ8-Tetrahydrocannabinol in Rats.

The use of Δ8-tetrahydrocannabinol (Δ8-THC) has increased in recent years. Given that the oral absorption of cannabinoids in oil formulations is typically slow and variable, nanoemulsions may be an improved delivery vehicle. Therefore, we characterized the pharmacokinetics (PK) in Sprague-Dawley rats following the administration of three different oral formulations containing 10 mg/kg Δ8-THC: a translucent liquid nanoemulsion, a reconstituted powder nanoemulsion, and a medium chain triglyceride (MCT) oil solution for comparison. Δ8-THC was also administered intravenously at 0.6 mg/kg. Plasma samples were quantified for Δ8-THC and two metabolites, 11-hydroxy-Δ8-THC (11-OH-Δ8-THC) and 11-carboxy-Δ8-THC (COOH-Δ8-THC). Non-compartmental PK parameters were calculated, and a PK model was developed based on pooled data. Despite a smaller median droplet size of the translucent liquid nanoemulsion (26.9 nm) compared to the reconstituted powder nanoemulsion (168 nm), the PK was similar for both. The median Tmax values of Δ8-THC for the nanoemulsions (0.667 and 1 h) were significantly shorter than the median Tmax of Δ8-THC in MCT oil (6 h). This resulted in an approximately 4-fold higher Δ8-THC exposure over the first 4 h for the nanoemulsions relative to the MCT oil solution. The active 11-OH-Δ8-THC metabolite followed a similar pattern to Δ8-THC. The non-compartmental bioavailability estimates of Δ8-THC for the nanoemulsions (11-16.5%) were lower than for the MCT oil solution (>21.5%). However, a model-based analysis indicated similar bioavailability for all three oral formulations. These results demonstrate favorable absorption properties of both nanoemulsions, despite the difference in droplet sizes, compared to an MCT oil formulation.

Shock-wave model of acoustic cavitation.

Shock-wave model of liquid cavitation due to an acoustic wave was developed, showing how the primary energy of an acoustic radiator is absorbed in the cavitation region owing to the formation of spherical shock-waves inside each gas bubble. The model is based on the concept of a hypothetical spatial wave moving through the cavitation region. It permits using the classical system of Rankine-Hugoniot equations to calculate the total energy absorbed in the cavitation region. Additionally, the model makes it possible to explain some newly discovered properties of acoustic cavitation that occur at extremely high oscillatory velocities of the radiators, at which the mode of bubble oscillation changes and the bubble behavior approaches that of an empty Rayleigh cavity. Experimental verification of the proposed model was conducted using an acoustic calorimeter with a set of barbell horns. The maximum amplitude of the oscillatory velocity of the horns' radiating surfaces was 17 m/s. Static pressure in the calorimeter was varied in the range from 1 to 5 bars. The experimental data and the results of the calculations according to the proposed model were in good agreement. Simple algebraic expressions that follow from the model can be used for engineering calculations of the energy parameters of the ultrasonic radiators used in sonochemical reactors.

Matching a transducer to water at cavitation: acoustic horn design principles.

High-power ultrasound for several decades has been an integral part of many industrial processes conducted in aqueous solutions. Maximizing the transfer efficiency of the acoustic energy between electromechanical transducers and water at cavitation is crucial when designing industrial ultrasonic reactors with large active volumes. This can be achieved by matching the acoustic impedances of transducers to water at cavitation using appropriately designed ultrasonic horns. In the present work, a set of criteria characterizing the matching capabilities of ultrasonic horns is developed. It is shown that none of the commonly used tapered-shape horns can achieve the necessary conditions. An analytical method for designing five-element acoustic horns with the desirable matching properties is introduced, and five novel types of such horns, most suitable for practical applications, are proposed. An evaluation of the horns' performance is presented in a set of experiments, demonstrating the validity of the developed theoretical methodology. Power transfer efficiency increase by almost an order of magnitude is shown to be possible with the presented horn designs, as compared to those traditionally utilized.

SENSE imaging with a quadrature half-volume transverse electromagnetic (TEM) coil at 4T.

PURPOSE: To demonstrate the feasibility of high-field SENSE imaging of large objects, such as the human head, using a semicircular (half-volume) coil for both transmission and multi-channel reception. MATERIALS AND METHODS: As a proof of concept, we present experimental data obtained using a seven-element half-volume (180 degrees of arc) transmit/receive quadrature transverse electromagnetic (TEM) coil. SENSE images of the human brain were acquired with a reduction factor of R=2, using two degenerate linear modes of the same coil as independent receive channels at 4T. Since the need for additional hardware (i.e., a separate set of receive coils) is eliminated, the design can be substantially simplified. RESULTS: The experimental data demonstrate that linear modes of the half-volume TEM coil have essentially no noise correlation, and their sensitivity profiles satisfy the requirement for small g-factors. Also, this type of coil provides efficient transmission with a relatively large uniform region and a reception profile that is more uniform than that of the surface coils. CONCLUSION: We demonstrate the feasibility of SENSE imaging using a half-volume coil. Half-volume coils allow reduced total power deposition compared to full-volume coils, and may replace the latter in body imaging applications in which the target region of interest (ROI) is smaller than the entire torso.

Sensitivity enhancement and compensation of RF penetration artifact with planar actively detunable quadrature surface coil.

An actively detunable planar quadrature surface coil for human body imaging at 4 T has been constructed and compared with a conventional linear surface coil. The coil could be used as a transmit/receive or a receive-only device in combination with a volume transmit coil. Transmission, reception profiles and the corresponding images acquired with each coil, as well as with both individual modes of the quadrature coil, are presented. Data collected using a tissue equivalent loaded phantom recorded with the linear surface coil demonstrated significant intensity distortions due to RF penetration artifact. The quadrature surface coil, on the other hand, provided compensation of the artifact, separately in its transmission and reception profiles as well as in the resultant images. Substantial sensitivity gain was also observed for the quadrature coil compared to the linear device. Significant advantages of using the quadrature surface coil over the linear device at 4 T have, therefore, been demonstrated.