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The skin is composed of three layers—epidermis, dermis, and subcutaneous tissue—and four ancillary organs which are the hair, nail, sweat glands, and sebaceous glands.

The epidermis is made up of basic level, stratum spinosum, granular layer, stratum lucidum, and corneum from the bottom to up. The dermis is between the epidermis and subcutaneous and contains collagen fiber, elastic fiber, reticular fiber, and amorphous matrix. There are a few auxiliary

organs in the dermis, including hair follicles, sweat glands, sebaceous glands, nerves, blood vessels, and lymphatic vessels. Subcutaneous fat lies under the dermis and is formed by adipocytes. The main tissue of the subcutaneous tissue is fat and fiber. For scanning of the skin and soft tissue, 7.0– 30 MHz high-­frequency transducer is generally used. The structures in the epidermis and dermis can be shown clearly if 20 MHz or higher-fre- quency transducer was used.

1.1\ Scanning Method

When small lesions in the skin, dermis, and subcutaneous tissue are scanned, a water-filled balloon or a thick layer of coupling agent can be put between the probe and skin so that the section is more clearly imaged. Lesion in the subcutaneous can be shown well with coupling agent. The sonogram of the skin and soft tissue in routine scanning will be different from that of pressurized scanning. The compression of transducer to the skin should be the same when contrastive scanning is performed at two points.

1.2\ Section Structure

There are four layer structures from the skin to the subcutaneous. (1) The first layer appears hyperechoic, which is a reflection interface formed by the epidermis. (2) The second layer is the dermis; it has homogeneous isoechoic or slightly hyperechoic superficial part and hyper-

echoic deep part. (3) The third layer is the subcutaneous fat; it is hypoechoic with transverse hyperechoic texture parallel to the skin. (4) The fourth layer is the isoechoic muscle layer, which can be mixed up with hyperechoic bars which are parallel to the skin. The direction of linear bars indicates the direction of muscle texture. The thickness of the subcutaneous is not the same as different parts of the body.

1.3\ Measuring Method

The thickness of every layer of the skin is measured if necessary. It may be more clear if the epidermis is measured in zoom condition.

1.4\ The Clinical Application Value

The diffuse and local abnormals in the skin including cystic and solid diseases can be diagnosed.

Probe is placed on the forehead transversely. A large amount of layer of the coupling agent is smeared between the transducer and skin.

2.2\ Section Structure

The (1) Epidermis, (2) Dermis—the bounder between the dermis and subcutaneous fat of the face is not clear—(3) Subcutaneous fat, (4) Frontal muscle, and (5) Frontal bone.

Thickness of every layer of the skin can be measured if necessary.

2.4\ The Clinical Application Value

The diffuse and local abnormal skin conditions including cystic and solid diseases can be diagnosed by this plane. It can be used to make postoperative follow-up and observation in cosmetic surgery.