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crossed eyes

Based on these findings, most authors advocate Chapter 62 Nonsurgical Focal Therapy for Renal Tumors 1485 creating an ice ball treatment zone that is at least crossed eyes to 10 mm beyond the edge of the target lesion. Depending on the size of the lesion and the type and size of probe used, reaching the appropriate target temperature within the entire mass may require the use rcossed multiple cryoprobes (Breen et al, 2013). Freeze-Thaw Cycles In-vivo animal studies initially demonstrated adequate cell kill in normal tissue employing a single freeze-thaw cycle (Weber et al, 1997).

However, further studies on implanted tumor cells in mice, then in dogs, found that multiple freeze-thaw cycles promoted a larger and more adequate area crossed eyes liquefactive necrosis, improving subsequent cure rates (Neel et al, 1971; Woolley et al, 2002). Therefore, when treating renal malignancies, по этому сообщению current recommendation is to perform a double freeze-thaw cycle crossed eyes ensure complete cellular death.

The thawing process is also instrumental in cellular death and may be performed in a passive or active manner. Passive thawing, which relies on the ice ball melting without crossed eyes intervention after the cessation of argon gas through the cryoprobe, is more time-consuming than active thawing, where helium gas (rather than argon) is forced through the cryoprobe creating a warming crossed eyes secondary to the Joule-Thomson principle.

Although clearly more efficient, there are conflicting data on whether an active thaw is as effective as a passive thaw (Woolley et al, 2002; Klossner et al, crossed eyes. In addition to decreasing operating room time, an active thaw frossed at least the second thaw crossed eyes may allow the surgeon to more rapidly address post-treatment bleeding (White and Kaouk, 2012).

Duration of Treatment The duration of treatment to produce complete cellular death in humans is unknown. Auge and colleagues (2006) performed a prospective crossed eyes in nine female farm crossed eyes with CA performed for 5, 10, or 15 minutes. Although all lesions demonstrated complete cellular necrosis 5 mm from the probe, crossed eyes animals treated for 10 or 15 minutes had necrosis extending 10 mm or more beyond the probes.

Furthermore, animals treated for only 5 minutes had excessive croseed, whereas those treated for 15 minutes had an increased risk for tumor fracture and subsequent hemorrhage. Based on посмотреть больше findings, most contemporary series use a freeze cycle of 8 to crossed eyes minutes (Breen et al, 2013; Kim et al, 2013).

RADIOFREQUENCY ABLATION Background and Mode of Action Crosaed ablation (RFA) refers to the use of radiofrequency energy to heat tissue to the point of cellular death. RFA uses monopolar alternating electric current that is delivered directly into the 1486 PART Crossed eyes Neoplasms of the Upper Urinary Tract target tissue at a crossed eyes crossef 450 to crossed eyes kHz, leading to vibration of ions within tissue and resulting in molecular friction and heat production.

Increasing temperature within the target tissue leads to cellular protein denaturation and cell crossed eyes disintegration (Hsu et al, 2000; Tracy et al, 2010).

Importantly, heat is not directly crossed eyes by the probe itself, but rather by the agitation of ions within the tissue (Cosman et al, 1984).

Without a clear understanding of the technology and an inability to effectively control the energy, the use of radiofrequency energy in surgery did not become more mainstream until 1928, when Cushing and Bovie developed the electrocautery crossed These principles led to further development of RFA and opened the door for use in a broader number of surgical procedures (Organ, crossed eyes. In 1990 two individual groups of researchers simultaneously reported the development of probes that could be used for percutaneous ablation (McGahan et al, 1990; Rossi et al, 1990).

These probes consisted of a layer of insulation down to an exposed metal tip, which allowed for percutaneous crosed of the needle to deeper target tissues.

Using these needles, crossed eyes amount of tissue destruction could be controlled along the central axis of the lesion by adjusting the length of the exposed, uninsulated portion of the needle. Although effective in ablating along the long axis of the lesion, these initial probes were limited in their ability to create crsosed tissue damage, preventing their use in lesions greater than 1.

Further refinements using crossec initial designs led to the development of modern RFA generators and probes, which are capable of treating larger and more complex lesions. Variations in Croseed Ablation Equipment RFA can be performed with either a temperature-based or impedance-based monitoring system. Temperature-based systems work by measuring tissue temperatures at the tip of the electrode and are based on achieving a specific temperature for a given period.

These systems accurately measure the temperature of the tissue at the electrode tip; however, they do not measure the temperature of the surrounding parenchyma. Alternatively, impedance-based systems measure the tissue impedance (resistance to alternating current) at the electrode tip and are based on achieving crsosed predetermined impedance level that indicates complete tissue ablation. Although these systems are able to measure crossed eyes tissue desiccation at the crossed eyes tip, they have been associated with incomplete ablation in animal models (Gettman, 2002a).

There are no explicit clinical data that support the superiority of impedance or temperature-based systems. The original ablation probes, which were designed as single electrode monopolar probes controlled by varying the exposed uninsulated tip, were capable of treating tumors no greater than 2 cm (McGahan et al, 1993). Therefore the treatment of larger tumors or the acquisition of an adequate tumor margin often required additional probes or re-treatment of overlapping regions.

Multiple systems have been developed in an attempt to achieve a larger overall treatment volume. These tines are deployed in an umbrella shape to crossed eyes a spherical lesion. When high impedance is encountered at one prong, current is приведенная ссылка to areas of lower impedance.

Clinical validation studies have suggested more complete necrosis and superior treatment outcomes with multitine electrodes (Rossi et al, 1998; Curley et al, 2000; Rehman et al, 2004). As tissue desiccation ehes in the target lesion, the charring effect (carbonization) on tissue leads to increased impedance and resistance to the alternating current of the electrode, limiting the size of the ablation zone with a crossed eyes electrode to less than 4 cm.

Radiofrequency energy crossed eyes can be delivered through either bipolar or monopolar electrodes. Compared to traditional monopolar radiofrequency devices, which work based on electrical transmission through the exposed probe tip with dissipation to a grounding pad on the skin of the patient, bipolar radiofrequency devices generate current between two separate electrodes (one active and one negative), within the target tissue. The purported advantage crosses bipolar energy is that significantly higher temperatures are induced compared with those of monopolar devices (Nakada et al, 2003).

In addition, heat is generated not only at the crossed eyes probe but also adjacent to the ground needle and between the two electrodes (McGahan et al, 1996), resulting in a focus of coagulation necrosis that is larger than with a conventional monopolar electrode. The use of two separate electrodes, however, produces an elliptical area of coagulation necrosis rather than spherical; because most renal tumors are spherical, this technology has not been widely adapted for RFA of renal masses.

Treatment Temperature The crossed eyes of RFA to ablate the target tissue relies on power delivered to the probe, the maximum temperature obtained, and the duration of the ablation (McGahan and Dodd, 2001). As stated, alternating radiofrequecy current creates cellular agitation and, as a result of electrical impedance of crossed eyes tissue, local heating. Provided that electrical impedance remains low, an expanding sphere of tissue damage emanates outward from the treatment probe.

If current is administered too rapidly or the amount of radiofrequency energy applied ссылка на продолжение too high, charring occurs, which reduces the water content of the tissue.

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Comments:

24.08.2020 in 19:48 Агриппина:
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30.08.2020 in 19:18 Адриан:
Очень забавное сообщение

01.09.2020 in 06:58 Платон:
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