了解超声

通过Dr Sarah Tonks/ 2016年6月22日

萨拉博士唐克斯细节三英洁具ce behind ultrasound and explains how it can be used for skin tightening

聚焦超声最近已开发,以满足实现显著非侵入性的皮肤提升和收紧日益增长的需求。面巾纸的光老化如下纹理,色素,骨骼的半预测的进展,以及脂肪changes.1起初,动态皱纹存在其发展与时间静态皱纹。该组织开发松弛,常出现于下巴和颏下区。传统上用于治疗皮肤老化的能量输送装置将包括烧蚀二氧化碳或铒:ytterium - 铝 - 石榴石(YAG)的设备,或治疗诸如深化学换肤和磨皮。这些方法依赖于真皮和reepithelialisation的消融,而在为了使显著足够热损伤到真皮刺激伤口愈合响应,并因此胶原重塑和组织的收缩。1Unfortunately most of these treatments require significant patient downtime.

More recently, other devices have become available such as infrared and LED devices, and energy-based procedures such as radiofrequency. Radiofrequency ablation allows the use of thermal energy to the reticular dermis to cause tissue contraction and remodelling whilst minimising downtime. In addition, these have the added benefit of being a safer treatment than those listed above, for a wider range of skin types.1Unfortunately the results are often more modest than more invasive procedures and there is considerable individual variation in responsiveness to treatment.

What is ultrasound?

超声是一种能量形式可以聚焦并深深地渗透到组织中以引起热凝固。有用于超声几个术语,诸如强烈聚焦超声(IFUS),高强度聚焦超声(HIFU),microfocused超声(MFU)和聚焦超声(FUS)。HIFU使用高能超声波,主要用于在医疗应用中,例如消融肿瘤或脂肪组织为主体轮廓。MFU使用低能量来治疗皮肤的表层。HIFU涉及热性能和空化导致细胞破裂而死亡,而MFU依靠热量来实现组织的影响。2For the remainder of this article the energy modality referred to will be FUS as this is the type most commonly used in aesthetic treatments.

FUS is similar to the ultrasound used in medical imaging but it is highly convergent and used to form different frequencies of energy. Transducers direct the ultrasound energy to a small focal point where the elevated temperatures are capable of causing tissue coagulation. Like medical imaging, the beam of ultrasound energy can pass harmlessly through the skin allowing the focal point to target the subcutaneous tissues.2

Ultrasound is the sound wave frequencies in the range of 18-20 kHz, which is above the range of human hearing. Inducible energy is delivered to specific foci in the dermis and subcutis leading to generation of heat, initiating the tissue repair cascade. Thermal coagulation points are placed at prescribed depths creating micro-coagulation zones of 1 to 1.5mm.3The thermal injury is confined by keeping the pulse duration short – the epidermis is unaffected if the energy delivered is not excessive, so there is no need for epidermal cooling.3As the tissue only has smaller zones of focal damage, rapid healing can occur from tissue immediately adjacent to the lesions. The ultrasound vibrates tissue and creates friction between molecules, which absorb the mechanical energy leading to heat.

Coagulation only occurs in the focal range of the beam. Energy is deposited in short pulses of 50-200 milliseconds. The energy delivered at each site is around 0.5-10J.4It is estimated that the tissue is heated to 65-75?C, which is the temperature at which collagen denaturation occurs and tissue repair cascade begins. The intermolecular hydrogen bonds are broken causing the chains of collagen to fold and assume a more stable configuration resulting in shorter, thicker collagen.4 De novo collagen formation occurs in the areas of thermal tissue coagulation and new viscoelastic collagen forms causing the lifting and tightening of the skin. FUS targets the SMAS which is a fan-shaped structure covering the face and connects the facial muscles with the dermis.4

的紧缩发生由于加热pecific zones of tissue. Histologic evidence suggests that dermal collagen and elastic fibres were increased in number, causing thickening of the reticular dermis.5 The onset of collagen remodelling occurs up to around three months and persists for around one year, which is similar to radiofrequency or laser energy sources.2

Cadaver studies have shown that penetration depth is determined by frequency – higher frequency waves produce a shallow focal injury zone and low frequency waves penetrate more deeply. They have also demonstrated consistency in depth, size and orientation of the thermal coagulation points in the subdermal soft tissue and deeper SMAS layers while preserving adjacent soft tissue.1,3,6Apart from ionising radiation, ultrasound is the only type of inducible energy that can be delivered into deep tissue selectively.1

病人的选择

Those who wish to avoid a surgical facelift but would like an improvement in skin laxity are ideal candidates. The patient should have mild to moderate skin and soft tissue laxity. Smokers and those with excessive photoageing are not ideal candidates as their ability to create collagen may be inadequate. Those with severe ageing, heavy and full tissues may have their result impaired by the inability of the collagen to shorten. Younger patients are more suited for the procedure as they generally have a more robust wound-healing response. Relative contraindications are medical conditions that impair wound healing and those who have a keloid response. Absolute contraindications include an open wound at the treatment site, cystic acne, a metallic implant at the site of treatment and pregnancy. Safety has been demonstrated across all skin types as absorption of ultrasound energy is independent of the melanin content of skin; the microscopic and bulk mechanical properties of the tissue determine the absorption in the skin.7

重要的是,病人有程序的切合实际的期望。临床改善往往是微妙的,不像外科手术。还为没有明显的临床症状明显改善的潜力。

Specific devices

有FUS设备有若干种在英国上市,如Ulthera,Ultracel和Doublo。其中的一些允许真皮和具有显示器,这允许关键的解剖结构,并允许精确的能量沉积到真皮的深处的识别处理之前,皮下组织的直接可视化,尽管目前尚不清楚的是能够可视化的组织以这种方式使得在处理结果的临床改善。

Ulthera received FDA approval for eyebrow lifting in 2009 and then gained approval for skin lifting of the neck and submental tissue in 2012.8The device consists of a computer, central power unit and interchangeable transducers. Multiple output settings can be controlled such as power output, exposure time, length of exposure time and time delay between each exposure. The device has four available transducers: super superficial 19MHz at 1.5mm focus depth, superficial 7.5MHz at 3mm focus depth, intermediate 7.5MHz at 4.5mm focus depth, deep 4.4MHz at 4.5mm focus depth. The Ultracel is a similar device that has a 3 and 4mm transducer available in the UK.

In a recent Korean study two devices were compared for facial skin tightening in 20 patients (Ulthera and Ultra-Skin). The two devices had similar efficacy in blinded clinician and quantitative assessment, although there were some differences with patient satisfaction and degree of pain. Interestingly, the patients reported more pain but a higher degree of satisfaction with Ulthera, despite there being no significant difference in the blinded assessors evaluation of the results.9

协议

深度处理是通过在该部位的皮肤的厚度决定。与皮肤较薄的区域应与肤浅的深度处理,脸颊和submentum应与更深层次的和肤浅的传感器都被处理。

In dual-plane treatment the deeper plane is treated first. The efficacy of treatment is increased when multiple treatment passes are used. In one study, areas of the face and neck were treated with a 4MHz and 4.5mm transducer followed by a 7MHz and 3mm transducer. Two blinded clinicians determined that 8 of 10 patients showed clinical improvement 90 days after treatment while nine subjects reported improvement.10If the vector is varied, further improvements have been demonstrated in treatment outcome. Using the same energy output one study reported that 15 vertically orientated treatment lines in 3 and 4.5mm tissue depths produced significantly greater lifting than 15 horizontally placed lines in the opposing brows and marionette lines.11Overall treatment sites receiving more treatment lines and higher energy at dual depths produced significantly greater lifting. Despite concerns about lipoatrophy with FUS, this phenomenon has not been reported in the literature so far. Although FUS typically results in microscopic coagulation, staking of pulses should be avoided and repeat treatments with some time interval would be better in terms of safety to avoid cavitation.12

患者应被告知从治疗,如果可能的应用天面的基础上,粉和乳液不要。脸上全金属首饰应该被删除。那些单纯疱疹感染病史应采取预防性抗病毒药物的前两天,治疗后六天。皮肤被治疗前清洁任何脸谱或产品的一些从业者标记目标的列数。一种超声凝胶被施加到治疗部位和探针被放置在皮肤上并激活。换能器的整个表面区域,应适用于皮肤。它可能需要在手术过程中重新应用超声凝胶以确保适当的耦合。在一些机器中,可以以可视化的超声图像中的显示器,其可与真皮深层到SMAS的相应层被对准在焦深。超声脉冲的平行阵列被递送。行数取决于治疗面积的大小。 Treatment should be avoided over the thyroid gland, inside the orbital rim and over implants. Post procedure the ultrasound gel is removed and the patient is free to return immediately to their usual activities.

Pain

The amount of pain experienced varies from mild to severe and the type of pain control used varies according to physician preference. The use of 5-10mg diazepam and 50-75mg meperidine 20-30 minutes prior to the procedure has been described.13Others have described topical or local anaesthesia, conscious sedation, cold compresses, high-dose non-steroidal anti-inflammatories, oral or intravenous narcotics and massage.14Most patients having treatment to the mid-face and neck do not require any pain control, whereas those treated to the brow may require some due the thin tissue overlaying the frontal bone.11这是我的偏好不使用任何止痛方法,因为我知道,病人将无法通知的,如果你麻醉时损坏神经。

Safety

这种治疗有较好的副作用谱和大多数副作用是暂时的。可能的副作用包括疼痛,红斑,水肿和紫癜。可能发生的最令人痛心的并发症是运动神经麻痹。所在区域的面神经分支是肤浅的风险最大,如三叉神经在寺庙颞支,并在下巴下颌缘神经。症状可以看出治疗后一到两个小时,继发于神经发炎。分辨率是二到六个星期内看到。13Three of the patients studied have developed transient dysaethesia to the deep branch of the supraorbital nerve lasting three to seven days and four patients developed numbness along the mandible after cheek treatment that resolved after two to three weeks.11

Summary

Focused ultrasound delivers ultrasound energy to predetermined depths to the deep dermis and subdermal tissue. Neocollagenesis and tissue contraction occurs in the months after treatment. As the energy delivered is focused precisely and adjacent tissue is spared it has a very good safety profile. More recent treatment developments have included the use of this technology on other body sites including the décolletage.

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