High Resolution Ultrasound
HRUS Image of Normal Skin
The EPISCAN produces high resolution images of the skin and superficial soft tissue to a vertical resolution of about 40 microns. The different layers of the epidermis and dermis can be visualized and distinguished. Subcutaneous structures can be identified and structures like tendon, blood vessels and ligaments are seen at a microscopic level. Each tissue has its own reflective quality giving it its unique appearance on the screen. Pathology such as edema and foreign bodies are of a different reflective quality, separating them from the surrounding tissue.
The scans should be read from the top down. They should be pictured as a non-invasive biopsy starting from the surface of the skin and continuing down to the selected depth. The intensity of the reflections is an indication of the density of the tissue. The intensity will also be affected by the reflective quality of the surrounding tissue. In other words if there is fluid above a structure the reflection off that tissue will be greater than if there were more dense tissue above it. The top reflection or entrance reflection is always intense because of the contrast between it and the ultrasound gel.
Skin
Ultrasound image of the skin exhibits very characteristic patterns. The top reflection off the epidermis is a strong reflection. This represents the stratum corneum. Directly beneath this hard reflection is a very much less reflective are that represents the stratum malpighii or area of living cells of the epidermis. Directly beneath this is the papillary layer of the dermis. This shows a homogenous pattern of moderately dense structure. The reticular layer of dermis is beneath the papillary layer. It has a slightly greater density with small highly reflective strips throughout. The dermis may have several lucent areas passing through it. These represent hair follicles or glandular structures.
Image of Abdomen
Directly below the dermis is a hard reflection that represents the dermal-hypodermal boundary. This reflection will be greater in thin skin than in thicker skin. The reason for that is that thicker skin is less mobile and is more firmly attached to the hypodermal tissue making this interface more gradual and therefore acoustically less distinct.
Subcutaneous tissue (Hypodermis): The reflective patterns of the deeper tissue will vary by the anatomy found in the imaged area. Structures such as blood vessels, glands, fascia and adipose tissue can be identified. Generally the deep fascia can be identified below a layer of subcutaneous tissue.
Deeper Tissue
Many structures can be identified in the deeper tissue. Tendons and ligaments can be imaged in both longitudinal and cross section. Nerves can also be distinguished as well as blood vessels. The bone/soft tissue interface can also be seen. Edema is easy to distinguish from normal tissue because of the marked difference in reflective quality of fluid with normal tissue.
