A new non-invasive ultrasound imaging technique can detect changes in skin elasticity that are predictive of disease progression in scleroderma, a recent pilot study suggests.
The study, “Ultrasound Surface Wave Elastography for Assessing Scleroderma,” was published in the journal Ultrasound in Medicine and Biology.
Elastography is a medical imaging method, used in liver disease, that measures the relative stiffness of soft tissues. Meanwhile, a surface ultrasound probe is regularly used to detect stiffness in liver disease.
Researchers from the Mayo Clinic in Minnesota now tested a new surface wave elastography technique — which combines these two techniques — to measure two clinically relevant skin properties: elasticity and viscosity.
Elasticity refers to the skin’s ability to snap back to its original shape after stretching, while viscosity is associated with the skin’s thickness. Together, they are referred to as skin viscoelasticity.
Scleroderma affects both of these properties, causing loss of elasticity as well as thickening and hardening of skin.
The most common clinical method for assessing the skin is the Modified Rodnan Skin Score (MRSS). A patient’s score is monitored over time, and improvements generally correlate with better disease outcomes.
However, the MRSS is a highly subjective measurement, varying considerably from one rater to the next. The test also has other limitations, according to scientists, who note that it may not capture disease progression or short-term treatment response.
To address these shortcomings, the researchers developed a technique called ultrasound surface wave elastography (USWE) to measure subtle changes in skin viscoelasticity.
USWE measures the change in speed of a sound wave as it passes over or through tissue, also known as wave propagation. The viscoelastic properties of the skin affect this propagation. Previous studies also have shown that USWE can safely be used on the lungs and eyes.
Now, the team used USWE to measure skin viscoelasticity in the left and right forearms of 26 scleroderma patients (mean age 60.3 years). The participants were tested while sitting, with their left or right forearm and upper arm placed on a pillow in a relaxed state.
The ultrasound findings were then compared with the MRSS scores to understand how well the two measures correlate.
The results showed that both surface wave speed at three frequencies and skin elasticity are higher with greater MRSS scores.
“This indicates that the stiffening of skin can be detected by both skin surface wave speed and MRSS measurements,” the investigators said.
In contrast, skin viscosity measured with USWE was not correlated with the MRSS findings. The scientists suggested that changes in viscosity may indicate edema, or swelling in response to early inflammation, while elasticity may be sensitive to progressive fibrosis, or scarring.
“We will further study if skin viscosity is sensitive enough to detect early edema from inflammation changes in SSc [scleroderma],” the researchers said.
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