Egg white as a blood coagulation surrogate

Overview of Therapeutic Ultrasound Applications and Safety Considerations: 2024 Update

A 2012 review of therapeutic ultrasound was published to educate researchers and physicians on potential applications and concerns for unintended bioeffects (doi: 10.7863/jum.2012.31.4.623). This review serves as an update to the parent article, highlighting advances in therapeutic ultrasound over the past 12 years. In addition to general mechanisms for bioeffects produced by therapeutic ultrasound, current applications, and the pre-clinical and clinical stages are outlined. An overview is provided for image guidance methods to monitor and assess treatment progress. Finally, other topics relevant for the translation of therapeutic ultrasound are discussed, including computational modeling, tissue-mimicking phantoms, and quality assurance protocols.

Development and characterization of polyurethane-based tissue and blood mimicking materials for high intensity therapeutic ultrasound

A polyurethane-based tissue mimicking material (TMM) and blood mimicking material (BMM) for the acoustic and thermal characterization of high intensity therapeutic ultrasound (HITU) devices has been developed. Urethane powder and other chemicals were dispersed into either a high temperature hydrogel matrix (gellan gum) or degassed water to form the TMM and BMM, respectively. The ultrasonic properties of both TMM and BMM, including attenuation coefficient, speed of sound, acoustical impedance, and backscatter coefficient, were characterized at room temperature. The thermal conductivity and diffusivity, BMM viscosity, and TMM Young's modulus were also measured. Importantly, the attenuation coefficient has a nearly linear frequency dependence, as is the case for most soft tissues and blood at 37 °C. Their mean values are 0.61f^1.2dB cm^-1 (TMM) and 0.2f^1.1dB cm^-1 (BMM) based on measurements from 1 to 8 MHz using a time delay spectrometry (TDS) system. Most of the other relevant physical parameters are also close to the reported values of soft tissues and blood. These polyurethane-based TMM and BMM are appropriate for developing standardized dosimetry techniques, validating numerical models, and determining the safety and efficacy of HITU devices.

Electrosurgery Turbinate Reduction Revisited: Can Comparable Volumetric Heating be Achieved Without Feedback Control?

BACKGROUND AND OBJECTIVES

Temperature-controlled radiofrequency inferior turbinate ablation (TCRFA) uses a feedback system to control thermal injury and achieve precise volumetric heating to induce specific scar formation. However, it requires costly single-use proprietary consumables. Comparable volumetric tissue heating may be achieved for a fraction of the cost by adjusting the power settings on traditional monopolar electrosurgery devices that use low-cost needle tips. This pre-clinical study aims to determine the optimized power parameters to achieve electrosurgical coagulum volume similar to that of TCRFA.

STUDY DESIGN/MATERIALS AND METHODS

An electrosurgery submucosal diathermy (SMD) system (cut mode, 4-32 W, 5-120 seconds) and a temperature-controlled radiofrequency ablation system (standard clinical parameters for treating inferior turbinate hypertrophy) were used to coagulate egg white and chicken breast. Coagulum major and minor axis were measured, and lesion volume was approximated as prolate spheroid.

RESULTS

No significant difference in volume was found between the temperature-controlled system and the electrosurgery system at 8 W for 30 seconds, 8 W for 60 seconds, 16 W for 30 seconds, 32 W for 5 seconds, and 32 W for 15 seconds. The time to achieve equivalent lesion size was significantly less in the SMD system when compared to the temperature-controlled system (P < 0.05).

CONCLUSION

Electrosurgery handpieces may achieve similar lesion volume effects as the temperature feedback-controlled, single-use handpieces when set to the optimized parameters. SMD handpieces are significantly more cost and time effective than proprietary devices, and they are easily used in the office. SMD devices may be a more affordable alternative to temperature-controlled systems with comparable lesion volume effect and may be valuable for office-based therapy. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

A cadaver study into the number of fasciotomies required to decompress the anterior compartment in forearm compartment syndrome

PURPOSE

There is no typical approach for decompression of forearm compartment syndrome, due to contradictory considerations regarding the characteristics of forearm anterior compartment deep fascia. The main purpose of this study was to determine how many fasciae should be opened to fully decompress the forearm anterior compartment. Further, the compliance of the deep anterior compartment was also investigated, to strengthen our results.

METHODS

An experimental study of a laboratory model of acute forearm compartment syndrome was performed. A deep forearm injection of egg white was undertaken to create an acute forearm compartment syndrome in sixteen non-embalmed human forearms from six male and two female donors. The pressure in the superficial and deep anterior compartments was recorded four times, both before and after each fasciotomy and the compliance of the deep anterior compartment was calculated for each step.

RESULTS

The first incision of the superficial lamina of the deep fascia was not sufficient to decrease the elevated compartment pressure in the superficial and deep anterior compartments. Whereas the pressures decreased to near-baseline levels, following the fasciotomy of the intermuscular septum observed posterior to the flexor carpi radialis. The last incision of the deep lamina of the deep anterior fascia had no noticeable impact. These observations supported the hypothesis of high compliance of the deep anterior compartment.

CONCLUSION

Two successive incisions were necessary to decompress the anterior compartment: the incision of the superficial lamina of the deep fascia and the incision of the intermuscular septum.

Measurement of the ultrasound attenuation and dispersion in whole human blood and its components from 0-70 MHz

The ultrasound attenuation coefficient and dispersion from 0-70 MHz in whole human blood and its components (red blood cells and plasma) at 37°C is reported. The measurements are made using a fixed path substitution technique that exploits optical mechanisms for the generation and detection of ultrasound. This allows the measurements to cover a broad frequency range with a single source and receiver. The measured attenuation coefficient and dispersion in solutions of red blood cells and physiological saline for total haemoglobin concentrations of 10, 15 and 20 g/dL are presented. The attenuation coefficient and dispersion in whole human blood taken from four healthy volunteers by venipuncture is also reported. The power law dependence of the attenuation coefficient is shown to vary across the measured frequency range. This is due to the varying frequency dependence of the different mechanisms responsible for the attenuation. The attenuation coefficient measured at high frequencies is found to be significantly higher than that predicted by historical power law parameters. A review of the attenuation mechanisms in blood along with previously reported experimental measurements is given. Values for the sound speed and density in the tested samples are also presented.