Utility of a High-Resolution Superficial Diagnostic Ultrasound System for Assessing Skin Thickness: A Cross-Sectional Study.

BACKGROUND: Compared with other imaging modalities, ultrasound is relatively deeply penetrating and can be used to evaluate deep dermal and subcutaneous structures. OBJECTIVE: Image skin thickness of the face and neck using high-frequency diagnostic ultrasound devices. MATERIALS AND METHODS: Skin overlying 20 different predesignated face and neck anatomic sites in 32 individuals was imaged using 2 commercially available high-frequency diagnostic ultrasound devices, a dedicated imaging device and a diagnostic device bundled with a therapeutic device. At each site, the subcutaneous and combined epidermal and dermal layer thicknesses were assessed by blinded expert raters. RESULTS: Similar skin thickness measurements were obtained. Notably, subcutaneous fat depth was measured to be 0.2 cm at the forehead; 0.5 cm at the mental eminence; and 0.6 cm at the submental, supraglenoid, and temporal regions. The combined epidermal and dermal thickness was approximately 0.1 cm at the zygomatic process, suborbital area, inferior malar region, gonion, supraglenoid area, and nasolabial-buccal, and nasolabial fold regions. CONCLUSION: This is the first study using high-resolution superficial diagnostic ultrasound to map skin thickness of the face and neck at standard anatomic locations. Ultrasound is an inexpensive, noninvasive, and convenient means to monitor dermatologic conditions and guide their treatment.

Intense focused ultrasound: evaluation of a new treatment modality for precise microcoagulation within the skin.

BACKGROUND AND OBJECTIVE: Focused ultrasound can produce thermal and/or mechanical effects deep within tissue. We investigated the capability of intense focused ultrasound to induce precise and predictable subepidermal thermal damage in human skin. MATERIALS AND METHODS: Postmortem human skin samples were exposed to a range of focused ultrasound pulses, using a prototype device (Ulthera Inc.) emitting up to 45 W at 7.5 MHz with a nominal focal distance of 4.2 mm from the transducer membrane. Exposure pulse duration ranged from 50 to 200 ms. Thermal damage was confirmed by light microscopy using a nitroblue tetrazolium chloride assay, as well as by loss of collagen birefringence in frozen sections. Results were compared with a computational model of intense ultrasound propagation and heating in tissue. RESULTS: Depth and extent of thermal damage were determined by treatment exposure parameters (source power, exposure time, and focal depth). It was possible to create individual and highly confined lesions or thermal damage up to a depth of 4 mm within the dermis. Thermal lesions typically had an inverted cone shape. A precise pattern of individual lesions was achieved in the deep dermis by applying the probe sequentially at different exposure locations. DISCUSSION AND CONCLUSION: Intense focused ultrasound can be used as a noninvasive method for spatially confined heating and coagulation within the skin or its underlying structures. These findings have a significant potential for the development of novel, noninvasive treatment devices in dermatology.