Physics of ultrasonic surgery using tissue fragmentation: Part I (original) (raw)
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Physics of ultrasonic surgery using tissue fragmentation: Part II
Ultrasound in Medicine and Biology, 1996
Ultrasonic surgical aspirators typically operate at a frequency between 20 and 60 kHz. A vibrating hollow horn moves against the tissue and suction is applied. The interaction causes tissue to fragment; the fragmented material is then aspirated. However, the mechanism of interaction is poorly understood: the most common view relates it to cavitation, probably active in coucert with other mechanisms, including the direct jack-hammer effect, shock-induced stress, acoustic micro&reaming and shearing stress. It has also been attributed to chopping, which will produce emulsification. This article reports a study that collected and analyzed ultrasonic, high-speed photographic, visual/optical and electrical data for a 23-kHz unit operating in water and a range of fresh pig tissues. The primary mechanism for tissue fragmentation is shown to be horn-tip impact and other mechanical forces, operating in combination with hydrodynamic forces applied to the tissue on the forward stroke in each cycle. No evidence of cavitation in tissue was observed.
Physics of ultrasonic surgery using tissue fragmentation
Ultrasonics, 1996
Ultrasonic surgical aspirators typically operate at a frequency between 20 and 60 kHz. A vibrating hollow horn moves against the tissue and suction is applied. The interaction causes tissue to fragment; the fragmented material is then aspirated. However, the mechanism of interaction is poorly understood: the most common view relates it to cavitation, probably active in coucert with other mechanisms, including the direct jack-hammer effect, shock-induced stress, acoustic micro&reaming and shearing stress. It has also been attributed to chopping, which will produce emulsification. This article reports a study that collected and analyzed ultrasonic, high-speed photographic, visual/optical and electrical data for a 23-kHz unit operating in water and a range of fresh pig tissues. The primary mechanism for tissue fragmentation is shown to be horn-tip impact and other mechanical forces, operating in combination with hydrodynamic forces applied to the tissue on the forward stroke in each cycle. No evidence of cavitation in tissue was observed.
Journal of Materials Processing Technology, 2008
High-power low-frequency ultrasound in the range 20–60 kHz has wide ranging clinical applications in surgical and medical instruments for biological tissue cutting, ablation or fragmentation, and removal. Despite widespread clinical application and common device operating characteristics, there is an incomplete understanding of the mechanism of tissue failure, removal and damage. The relative contribution of cavitation, direct mechanical impact and thermal effects to each process for specific tissue types remains unclear. Different and distinct mechanisms and rates of tissue removal are observed for interaction with soft and hard tissue types. Device operating parameters known to affect the interaction include frequency, peak–peak tip amplitude, suction and application time. To date, there has been little analysis of the effect of variations in, and interactions of, these parameters on tissue removal and damage for individual biological tissue types. Potential controllable damage mechanisms occurring in tissues include alteration in global biomechanical properties, histomorphological changes, protein denaturation and tissue necrosis. This paper presents a critical review of the literature on the clinical application, mechanism of tissue interaction, removal and residual tissue damage. It describes known mechanisms for distinct tissue types.
Spie Proceedings Series, 1998
The Cavitron Ultrasonic Surgical Aspirator (CUSA) is being used, especially in neuro- and liver surgery, to resect selectively soft and hard tissue in favor of elastic tissues like blood vessels, enabling the removal of tumors with minimal loss of blood. In this study the phenomena associated with CUSA were visualized to expand the understanding of the mechanism of action of the CUSA. Real- time high-speed imaging techniques were applied to capture cavitation phenomena during application of the CUSA under physiological settings: in water, at tissue surfaces and inside artificial tissue. Close-up photography using a 1 microsecond(s) flashlight showed the expanding and imploding cavitation bubbles around the rim of the ultrasonic vibrating hollow tip. Shock waves generated by imploding cavitation bubbles were observed using Schlieren techniques with a temporal resolution of 10 ns and synchronized with the duty cycle of the vibrating tip. In addition, thermal effects associated with friction between the vibrating tip and tissue were visualized sing a thermal imaging technique. The CUSA mechanism has proven to be a combined effect of cavitation induced fragmentation, mechanical cutting and thermal deterioration of tissue depending on the irrigation/aspiration flow, intermittent vibration regime and degree of tissue contact. The impact of the shock waves observed is undetermined yet. These real-time imaging techniques will contribute to expand the understanding of the working mechanism of CUSA and to show the characteristics of probe designs and influence of driving frequency.
PROSPECTS OF APPLICATION IN MEDICINE OF ULTRASONIC METHODS BASED ON THE USE OF CAVITATION
rao.akin.ru
It is considered that with the use of high intensity ultrasound in medicine, it is necessary to avoid a cavitation regimen because of specific features of the physical nature of cavitation (e.g., random and stochastic character of its origination, weak reproducibility of localization and the shape of lesions in tissues, etc.). Nevertheless, the results of investigations carried out in different laboratories for the last years, demonstrate an opportunity of application in medicine of new, non-traditional methods based just on the use of ultrasound cavitation. For example, one of the methods of ultrasound surgery can be based on a preliminary creation in tissues gas bubbles decreasing cavitation thresholds and, therefore, a threshold of ablation of tissues. Thus, independently on the method of bubbles generation (e.g. with the use of ultrasound or, for example, by means of introduction of ultrasound contrast agents), localization of cavitation lesions and their shape become quite reproducible. The cavitation regimen can be used, for example, for ultrasonic ablation of deep-located brain structures through an intact skull to prevent excessive heating of skull bones. Cavitation can be used also as an effective mean of enhancement of the thermal effect of ultrasound due to creation gas bubbles in tissues, which increase significantly the sound attenuation. Cavitation is considered to be one of the basic mechanisms of the enhancement of the efficiency of the action of antitumoral chemicals on malignant tumors. One of the possible applications of cavitation in oncology can be based also on ablation of blood vessels surrounding a tumor, that will lead to blocking of blood supply and, therefore, to increasing of the destructive effect of ultrasound on the tumor. Prospects of the researches directed on the development of new acoustic methods for application in medicine based on the use of cavitation are discussed.
Japanese Journal of Applied Physics, 2007
Recently, ultrasonic surgical knives have been applied in a variety of surgical operations. In this paper, the operation frequency of a surgical knife is focused on. Prototype ultrasonic knives operated at 24.3, 44.3, and 71.9 kHz were constructed. Differences in the effects on soft tissue depending on the operation frequency were investigated using these knives. Frequency characteristics were measured using two parameters: coagulation ratio and coagulated depth. For the same vibration velocity, at a lower frequency, the distribution of the coagulated tissue was deep and in a narrower region around the center of the tip. For the same vibration amplitude, the coagulated depth at each frequency was similar for all these frequencies. Furthermore, the dependences of tissue coagulation on the vibration velocity, pressure load, contact of the tip with tissue, and direction of vibration were investigated. From these investigations, it was found that the mechanical effect, rather than ultrasound absorption, is the dominant factor in tissue coagulation.
Surgical Endoscopy, 2009
Background Ultrasound shears often are applied in minimally invasive surgery because they facilitate fast and secure tissue dissection, thereby reducing operative time. Although the technical principle underlying all the shears is almost identical, considerable differences exist between specific instruments. However, production of disturbing mist should be avoided. Methods To obtain quantitative measurements regarding mist production, a novel hermetically sealed test system was developed. Tissue dissection efficiency was evaluated by means of a standardized cutting test. The dissection time and the numbers of cuttings were recorded. In this study, four different ultrasound dissectors from three manufacturers were assessed. One manufacturer provided two instruments: a conventional instrument and an improved version, which was designed particularly to reduce mist emission. Results The fastest ultrasound dissector emitted the highest quantity of disturbing mist. However, improved dissection efficiency does not linearly correlate with mist production. This clearly could be shown for the improved ''less mist production instrument,'' which turned out to work faster than the comparable standard dissector but produced significantly less mist. Conclusion Ultrasonic shears are effective for bloodless tissue dissection but may impede surgical proceeding by mist production. The findings of this study demonstrate that emission of mist can be reduced not only by lowering the dissection power, resulting in a prolonged dissection time, but also by modifying the technical design of an instrument. Further development of ultrasonic cutting devices therefore should account for the desired results.
Open Access Surgery, 2014
Background: A new ultrasonic device, Harmonic Focus ® +, has been developed that is smaller and delivers energy more efficiently than its predecessor via the inclusion of Adaptive Tissue Technology. This study was undertaken to compare its dissection capabilities to an advanced bipolar electrosurgery device in benchtop and preclinical evaluations. Methods: In ex vivo testing, Focus+ and LigaSure™ Small Jaw were evaluated for physical dimensions, device and tissue temperature after repeated applications to porcine jejunum, and burst pressure of vessel seals, transection time, and tissue sticking in 3-5 mm porcine carotid arteries. In in vivo testing, the devices were tested on intact porcine carotid arteries for thermal damage via collagen denaturation and in muscle incisions near rat sciatic nerve for acute inflammation via hematoxylin and eosin and for impaired axonal transport via β-APP. Results: Focus+ was smaller than the Small Jaw in width and height, yet it had a longer active blade and larger jaw aperture. Device temperatures were not different after application, but thermal spread (tissue temperature above 50°C) was 78% greater for Small Jaw (9.6 mm) than for Focus+ (5.4 mm). Burst pressures of sealed vessels were not significantly different between the devices: 900 (±466) mmHg for Focus+ versus 974 (±500) mmHg for Small Jaw. Small Jaw had a shorter individual transection time (5.0 seconds compared to 6.3 seconds for Focus+), whereas Focus+ had 70% less tissue sticking. Thermal damage, neural inflammation, and impaired axonal transport were all significantly lower for Focus+ compared to Small Jaw, by 19%, 57%, and 50%, respectively. Conclusion: With the addition of Adaptive Tissue Technology, Harmonic Focus+ builds upon the manifold advantages of ultrasonic devices in procedures requiring meticulous dissecting capability. Improvements in energy sensing and controlled delivery produce lower tissue temperatures and less thermal damage, especially critical when working near nerves. Focus+ produces vessel seal strengths equivalent to advanced bipolar devices and, although individual device activations are longer, the reduction in tissue sticking is expected to materially lessen operative time in clinical practice.
Physics in Medicine and Biology, 2012
Atomization and fountain formation is a well-known phenomenon that occurs when a focused ultrasound wave in liquid encounters an air interface. High intensity focused ultrasound (HIFU) has been shown to fractionate a tissue into submicron-sized fragments in a process termed boiling histotripsy, wherein the focused ultrasound wave superheats the tissue at the focus, producing a millimetre-sized boiling or vapour bubble in several milliseconds. Yet the question of how this millimetre-sized boiling bubble creates submicronsized tissue fragments remains. The hypothesis of this work is that the tissue can behave as a liquid such that it atomizes and forms a fountain within the vapour bubble produced in boiling histotripsy. We describe an experiment, in which a 2 MHz HIFU transducer (maximum in situ intensity of 24 000 W cm −2 ) was aligned with an air-tissue interface meant to simulate the boiling bubble. Atomization and fountain formation was observed with highspeed photography and resulted in tissue erosion. Histological examination of the atomized tissue showed whole and fragmented cells and nuclei. Airliquid interfaces were also filmed. Our conclusion was that HIFU can fountain and atomize tissue. Although this process does not entirely mimic what was observed in liquids, it does explain many aspects of tissue fractionation in boiling histotripsy.