Dexamethasone Sodium Phosphate Penetration During Phonophoresis at 2 Ultrasound Frequencies

Context The effect of ultrasound frequency on phonophoresis drug delivery in humans is unknown. Objective To determine if a low (45-kHz) or high (1-MHz) frequency delivered a higher dexamethasone (Dex) concentration through the skin. Design Controlled laboratory study. Setting Laboratory. Patients or Other Participants A total of 40 healthy men between the ages of 18 and 45 years (age = 23.1 ± 2.6 years, height = 176.1 ± 7.2 cm, mass = 88.5 ± 19.4 kg, posterior calf subcutaneous thickness measured using musculoskeletal ultrasound imaging = 0.6 ± 0.2 cm). Intervention(s) Participants were randomly assigned to 1 of 4 groups (ultrasound frequency at microdialysis probe depth): (1) 45-kHz frequency at 1 mm, (2) 45-kHz frequency at 4 mm, (3) 1-MHz frequency at 1 mm, or (4) 1-MHz frequency at 4 mm (n = 10 in each group). Three linear microdialysis probes were inserted at the desired tissue depth. We rubbed dexamethasone sodium phosphate (Dex-P) into the skin and then applied a 15-minute phonophoresis treatment. Main Outcome Measure(s) Dialysate was collected during the treatment and 60 minutes posttreatment and analyzed for Dex-P, Dex, and the metabolite form of Dex. The sum of the 3 analytes was calculated as total dexamethasone (Dex-total), and differences between the 45-kHz and 1-MHz treatment groups were determined by a repeated-measures analysis of variance. Results At 1 mm, 3 (30%) participants in the 45-kHz and 4 (40%) participants in the 1-MHz group had measurable levels of Dex-P. Total dexamethasone increased after the treatment ceased, independent of ultrasound frequency (P < .001), with a trend of the 45-kHz treatment to produce a greater increase in drug concentration (P = .006). At 4 mm, 5 (50%) participants in the 45-kHz and 1 (10%) participant in the 1-MHz group had measurable levels of Dex-P. We observed no difference in Dex-total concentration between treatment groups at 4 mm (P = .72). Conclusions Phonophoresis provided a mechanism for Dex-total delivery at the 1- and 4-mm tissue depths. However, the effectiveness of the ultrasound frequencies varied between the 2 measured tissue depths.

3D-printed phantoms for characterizing SERS nanoparticle detectability in turbid media

A 3D-printed phantom showed that SERS tag detectability in solution and turbid media are dissimilar and illustrated fiber-probe depth sensitivity.

Spatially Resolved Stress Analysis in Al2O3/3Y-TZP Multilayered Composite Using Confocal Fluorescence Spectroscopy

Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al2O3/3Y-TZP (3 mol % Y2O3-stabilized ZrO2) composite using the chromophoric fluorescence spectra of Al2O3. The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.

A computerized tomography-computer graphics approach to stereotaxic localization

✓ This paper describes the use of three-dimensional computer graphics to display structures visible in computerized tomography (CT) scans and to accurately determine optimum stereotaxic probe placement relative to those structures. A prototype Lucite stereotaxic frame designed for use in CT body scanners was fitted with a phantom consisting of small Lucite spheres representing intracranial tumors with diameters of 6 to 19 mm. A series of CT scans was obtained of the frame and phantom together. Edge outlines of the spheres were extracted from each scan in the series. A three-dimensional visual representation of the spheres was obtained by displaying their outlines from all CT scans. A superimposed visual simulation of the stereotaxic frame was adjusted interactively using several analog dials in order to simulate trajectory choice and probe depth before actual surgery. The frame settings and probe depth calculated by the graphical computer were then applied to the actual prototype frame in order to assess the accuracy of this combined CT-computer graphics approach to stereotaxic localization. The results of 22 such experiments and the implications for future clinical use of this new and precise localization technique are discussed.