Ultrasound B scanning with image analysis for assessment of allergic patch test reactions.

Assessment of patch test results has been performed visually and using ultrasound in the B mode. A positive test site has a typical ultrasonographic appearance, presenting a uniform hypoechogenic area in the dermis. In this zone, the mean amplitude of ultrasound reflection peaks decreases, and the extension of this area increases, together with the intensity of the eczematous reaction. A close correlation has been shown between visual scoring, amplitude decrease and surface increase of the hypoechogenic area. This technique seems to provide a reproducible system for the evaluation of patch tests.