Principles of the Laser and Applications
Sujoy K. Guba in Bioengineering in Reproductive Medicine, 2020
Major effects of surgical lasers on tissue are: vaporization, cutting and coagulation.3 When a sharply focused laser beam (for example, of spot diameter of 1 mm from a carbon dioxide laser) impinges on tissue, there is a rise in tissue temperature to as high as 800 C on account of energy absorption, which is mainly in the tissue water. At the irradiation site the conversion of irradiant energy into heat is considerably faster than the dissipation of heat through tissue by conduction and removal of blood. Hence the temperature rise is marked. As a result, water as well as the solid contents of tissue vaporize. Tissue is thus removed and if the beam spot is moved a cutting effect is obtained. At any location around the tissue vaporized zone there is a narrow region where temperature elevation is lower and instead of vaporization a coagulative effect is manifested. If this narrow area has blood vessels of size smaller than about 0.5 mm diameter the coagulation cauterizes the vessels thus checking blood loss and a blood free surgical field is obtained. Contrary to common belief, laser irradiation does not always produce a bloodless area. In a vascular area with larger blood vessels, laser focused to a small spot size cannot seal vessels and contain bleeding. In such a situation a defocused beam may be used. The same energy is now spread over a larger area giving a lower energy density. Limited temperature rise occurs. Vaporization is less and cell shrinkage due to dehydration, carbonization and coagulation are the more dominant effects.
Lasers in Medicine: Healing with Light
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
Two conditions must be met for vaporization to occur. First, the tissue must have been heated to at least the boiling point of water, and maintained at that temperature for some time. The amount of time needed for vaporization to occur is controlled by the amount of energy needed to vaporize a given volume of material. This is determined by the energy needed to disrupt all of the associations between neighboring molecules of water to convert them into isolated gas molecules. The amount of energy required for different tissues depends upon their varying water contents. This energy is called the heat of vaporization. Second, very short exposure times and high power densities must be used so there is no time for the heat to flow outward before enough energy has been delivered to vaporize the entire targeted region (Table 3.3and Figure 3.18b). When these conditions have been met, layers of tissue can be vaporized completely, with enough heat flowing to a thin surrounding region to coagulate it. A delicate balance must hold in laser surgery using photovaporization, since unlike a scalpel, the laser beam can cut deeply beyond its apparent extent if too high a power density is used.
Cannabis
G. Hussein Rassool in Alcohol and Drug Misuse, 2017
Cannabis is usually smoked as a cigarette (called a joint). Usually these substances are mixed with tobacco and smoked. Sometimes they are smoked in a pipe or bong. Smoking allows the user to regulate the dose because the effect is very rapid when used in this way. Cannabis has also appeared in blunts which are rolled with tobacco paper (dark brown color) or are cigars that have been emptied of tobacco and refilled with cannabis. Vaping cannabis is done by placing raw cannabis or THC oil in a vaporiser or e-cigarette. Currently there are devices capable of vaporising oils, waxes, and dry herbs. It is reported that cannabis users perceived vaporisation as a safer alternative to smoking (Lee et al. 2016). It is widely known that smoking (any product) is bad for our health: when marijuana is smoked, its combustion releases carbon-monoxide and other by-products that when inhaled, harm your lungs, throat and overall respiratory system. Some people make cakes containing cannabis or hashish. Space brownies, space cookies and space muffins are bakery products made using hashish. Some users also use cannabis to brew tea or cannabis-infused drinks. Cannabis or marijuana is the same product and is used as a relaxant or mild intoxicant. In fact, the term “marijuana” is part of the American lexicon and many Americans do not know any other name for the cannabis plant. It was stated that “The Spanish word ‘marijhuana’ was adopted to reinforce the connection between the ‘devil’s weed’ and Mexican immigrants who, allegedly, first introduced it to American society” (Serrano 2013).
Differences in those who prefer smoking cannabis to other consumption forms for mental health: what can be learned to promote safer methods of consumption?
Published in Journal of Addictive Diseases, 2023
Lindsay A. Lo, Caroline A. MacCallum, Jade C. Yau, Alasdair M. Barr
In conclusion, smoking cannabis was highly prevalent within this sample of dispensary medical cannabis users. Education can be a key tool for smoking harm-reduction. In those who prefer smoking cannabis, intent and patterns of use may be more similar to recreational users. As such, education on tactics for optimal symptom control (e.g. utilizing CBD) with less harmful methods (e.g. dried flower vaporization) is necessary.11 Information on the benefits of vaporizers should be more widely available. Finally, medical cannabis users should be encouraged to seek continual support from a knowledgeable healthcare provider where education and guidance can be provided. In a sample of authorized medical cannabis users in Canada under the care of a healthcare provider, vaporization was the most popular mode of administration.12 The main reported reason for vaporization use was to reduce negative health consequences associated with smoking. This aligns with what is seen clinically, when education and guidance is provided. The findings from this study may inform harm-reduction approaches to decrease the number of individuals smoking cannabis. This could help mitigate one of the greatest risks associated with cannabis use. Future research should focus on practical harm-reduction strategies that can be applied to this patient population.
Proactive esophageal cooling protects against thermal insults during high-power short-duration radiofrequency cardiac ablation
Published in International Journal of Hyperthermia, 2022
Marcela Mercado Montoya, Tatiana Gomez Bustamante, Enrique Berjano, Steven R. Mickelsen, James D. Daniels, Pablo Hernandez Arango, Jay Schieber, Erik Kulstad
The variations of density and thermal conductivity were taken from COMSOL predefined functions for human myocardium while the reference values were taken from the ITIS database [37]. The electric conductivity and the heat capacity were specified to increase linearly (Equations (13) and (14)) and then change near 100 C to account for the water loss associated with the evaporation phenomenon [39]. Equation (14) describes the heat capacity of the tissue during heating below the boiling point of water, but above this value, the formation of bubbles can occur. The effect of this phase change on the temperature distribution in the tissue is therefore included. Between 30 °C and 110 °C, Equation (17) describes the vaporization latent heat of water (
Holmium laser enucleation versus bipolar transurethral enucleation for treating benign prostatic hyperplasia, which one is better?
Published in The Aging Male, 2021
Jinze Li, Dehong Cao, Yin Huang, Chunyang Meng, Lei Peng, Zhongyou Xia, Yunxiang Li, Qiang Wei
Despite a growing amount of data reported in the literature, the comparison of HoLEP, and B-TUEP for the management of BPH is still unclear. And with that background, we performed a meta-analysis of the reported comparative studies to update the contemporary evidence base. In this study, we observed that HoLEP could have more advantages in perioperative parameters than B-TUEP. The significantly lower operation time, catheterization time, and bladder irrigation time in the HoLEP cohort. The biggest difference was found in the study of Patard et al. [25], which used a bipolar device with an oval electrode button. This technology has been developed for vaporization and coagulation. Another possible explanation is the proficiency of the surgeon. Boeri et al., Habib et al., and Higazy et al. [5,23,24] reported that the surgeons had rich experience in endoscopic enucleation (namely, >50 cases per technique). While, in the study of Patard et al. [25], both two surgical methods were performed by inexperienced surgeons (>15 cases). In general, the key to shortening the operation time of endoscopic enucleation is to accurately identify the surgical capsule plane. Meanwhile, hemostasis is also very important to make the field of vision as clear as possible during the whole process [34].
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