In vivo assessment of inflammatory skin using high frequency ultrasound image and quantitative parameters

Histological examination remains the most direct means to assess the inflammatory tissue. It however is still with the nature of invasiveness and is time consuming for the preparation of tissue slices. The slice apparently is not applicable for a long term observation of the tissue in situ. For these reasons, this study is to explore another approach to assess the inflammatory skin using strengths and statistical parameters of high frequency ultrasonic backscattering signals. The experiments were performed from the dorsal skins of BALB/c mice using a 50 MHz ultrasound. The dorsal skins of different mice were injected with a 0.15 ml of either saline or lipopolysaccharides (LPS) with dosage of 2 mg/ml to be as the control group or to induce the local inflammation of the skin as the experiment group, respectively. Each set of experiments was arranged for four days, in which images and backscattered signals of the skins from both control and experiment groups were scanned and acquired daily. Parameters to assess the inflammation included a typical cutaneous thickness estimated from ultrasonic image and that those of integrated backscatter (IB) and Nakagami parameter (m) were calculated from regions of acquired backscattering signals. Results showed that there were no significant differences among measurements of those control groups injected with saline. On the other hand, the inflammatory skin induced by LPS injection tended to result an increase of cutaneous thickness from 0.38±0.07 mm of normal skin to 0.7±0.11 mm of the fourth day. The corresponding IB tended to decrease from -182.5±2.7 dB to -194.4±2.5 dB and m increase slightly from 0.36±0.08 to 0.51±0.12. Those thickness and quantitative parameters variations could be directly associated with changes of tissue properties due to a transfer of massive fluid shifts from the intravascular space into the interstitium and intracellular spaces in the inflammatory skin. This study has demonstrated that cutaneous thickness, integrated backscatter, and Nakagami parameter estimated from high frequency ultrasonic signals are able to be applied to sensitively and quantitatively assess the inflammation of skin.