MAVIS: a non-invasive instrument to measure area and volume of wounds. Measurement of Area and Volume Instrument System.
Accurate measurement of the physical size of wounds is vital for assessment of the progress of healing. An instrument has been developed to measure area and volume of skin wounds, ulcers, and pressure sores. MAVIS--Measurement of Area and Volume Instrument System-is based on the principle of colour coded structured light. A set of parallel stripes of alternating colours is projected onto the wound area at an angle of approximately 45 degrees and is recorded by a CCD camera. From the known position of the focal points of projector and camera, and from the observed intersection points of the stripes of light with the wound surface, a computer calculates a three-dimensional map of the observed wound. The volume of the wound is defined as the volume of the region sandwiched between the observed surface and the original healthy skin surface which is simulated by cubic spline interpolation. This paper compares the performance of the instrument with three traditional wound measurement techniques using results obtained from a clinical trial involving 50 patients. Traditional area measurement techniques such as transparency tracings produce results with standard deviations between 4% (large wounds) and up to 20% (small wounds) of the measured mean value. MAVIS measurements reduce these standard deviations by 3-5%. Measuring the wound volume by alginate casts produces errors in volume figures between 5% and 40%. Standard deviations of MAVIS results are 5% smaller on average. The results demonstrate that MAVIS yields more reproducible results with a minimum of inter-observer error. The instrument does not make contact with the wound, provided visual records and measurements are made in less then 5 min. It is not suitable for undermined, very deep or very large wounds.