Elastography, a non-invasive ultrasound technique introduced in the 1990s, measures tissue stiffness or elasticity, providing insights beyond traditional palpation. It works by assessing how tissues deform under applied force, with stiffer tissues deforming less. Over the past decade, elastography has advanced significantly and is increasingly integrated into clinical practice due to its ability to provide detailed and objective information about tissue stiffness, complementing traditional imaging techniques. It has enhanced the specificity of conventional ultrasound for assessing liver fibrosis, as well as breast and thyroid masses, since stiffer tissues are more likely to be malignant. Elastography helps in distinguishing between benign and malignant tissues and can monitor the progression of diseases.

Currently available elastographic methods can be divided into static and dynamic: 

• Static Elastography (SE): Measures tissue elasticity by applying external pressure, either through direct compression or natural forces like blood vessel pulsation. (SE) is a common static method where images before and after compression are compared to create a color-coded map of tissue stiffness.

• Dynamic Elastography: Includes Shear Wave Elastography (SWE), which uses the speed of shear waves passing through tissue to measure stiffness. Stiffer tissues have higher shear wave velocities. SWE provides quantitative data on tissue stiffness and is less prone to observer variability compared to SE. The data that can be color-coded on images for clarity

Application in Dermatology

Skin tumors

SWE provided 83.3% sensitivity and 97.5% specificity in differential diagnosis of benign and malignant skin lesions (6). The results of previous studies imply that skin malignancies not only are stiffer than benign lesions, but are also less elastic than surrounding normal tissues (Figure1). A study (1) analyzed the strain ratios of skin malignancies, including basal cell carcinomas and squamous cell carcinomas, compared to benign lesions. The malignant lesions exhibited higher strain ratios than the benign tumors. usefulness of elastography was also confirmed in the case of malignant melanoma of the skin where the strain in malignant melanomas was found significantly higher than in surrounding normal tissues (2).

In addition, studies have generally found a significant correlation between ultrasound-measured melanoma thickness and pathological measurements (3). Obviously, elastography will not replace diagnostic methods used routinely to evaluate proliferative skin lesions, such as biopsy. Nevertheless, combined with dermatoscopy, EUS may constitute a useful screening instrument at early stages of the diagnostic process.(4)

Another potential application of elastography in oncology is identification of metastases in skin-draining lymph nodes (5). While normal lymph nodes are typically more elastic, metastatic nodes are stiffer. Elastography, when combined with conventional imaging techniques such as B-mode ultrasound and color Doppler, can significantly improve the sensitivity for detecting lymph node metastases of malignant melanoma. Ambroziak et al., 2019

Inflammatory cutaneous diseases

• Abscesses: Strain Elastography (SE) can detect stiff peripheral areas of abscesses that conventional B-mode ultrasonography cannot.

• Psoriasis: SE was used to monitor responses to corticosteroid therapy. Despite changes in skin thickness, elastography did not show alterations in plaque stiffness, suggesting limited use for psoriasis.

• Systemic and localized Sclerosis: Elastography, especially with modern Shear Wave Elastography (SWE) techniques, effectively assesses skin stiffness, which is crucial for evaluating disease severity. It is also valuable for monitoring treatment progress, as it can track the thickening and subsequent thinning of the skin in response to effective treatment.

• Other Fibrotic Conditions: Elastography is also useful for evaluating fibrotic and sclerotic conditions like post-irradiation lesions, pressure ulcers, and lipodermatosclerosis.

Aesthetic medicine

Increasing evidence suggests that skin elastography could be beneficial in aesthetic medicine, potentially serving as a measure of biological age and guiding personalized cosmetic treatments. It may also help monitor skin recovery and outcomes after aesthetic procedures. However, establishing reference ranges for facial skin elasticity and validating these uses of elastography require further research. 

Comparison with Other Imaging Techniques

• Confocal Microscopy: Provides high-resolution, subcellular images but limited depth (approximately 500 μm) and does not assess vascularization or stiffness.

• Optical Coherence Tomography (OCT): Offers high image speed and similar images to ultrasound but has limited depth of penetration and resolution for cancer cell morphology. Lacks Doppler and elastography capabilities.