Skin ultrasound for rheumatologists: Technical issues and challenges

In several rheumatic diseases, the skin is involved and therefore it is an organ of interest which may be investigated by the rheumatologist. Ultrasound imaging has been proposed for assessing multiple skin conditions providing qualitative and quantitative information about different parameters in distinct skin layers. Our aim was to describe with a pictorial essay the main challenges that the ultrasound imaging may encounter when investigating the healthy skin in different body areas.

Fourteen healthy subjects were submitted to skin ultrasound. The body areas that were investigated were decided following the 17 modified Rodnan skin score anatomical areas used in systemic sclerosis. Skin ultrasound was performed with a GE Logiq 10 with two probes (20 and 24 MHz). For an optimal quantification of the skin layers, the dermis interfaces either with the epidermis and hypodermis were investigated.

The results of the ultrasound analysis are described and summarized in a pictorial essay which shows that some main factors may significantly influence the quality of the images of the skin layers. Specifically, age, scanning position, probe frequency, and the optimal positioning of some anatomical areas, in particular the hands and digits, emerged as factors that may have a relevance in influencing the quality of the imaging of the skin layers. Moreover, some technical suggestions are proposed to help optimizing and standardizing the performance of skin ultrasound assessment in healthy population.

The pictorial essay we performed shows that the performance of skin ultrasound in healthy subjects still presents several issues that need to be addressed. The definition of the interface in different body areas is the first step which should be standardized before any measurement of the thickness of the skin layers is performed in rheumatic diseases.