MAVISII Measurement of Area and Volume Instrument System

MAVIS-II Measurement of Area and Volume Instrument System for Skin Wounds C. D. Jones, P. Plassmann University of Glamorgan, Medical Computing Research Group

MAVIS - II Introduction c MAVIS-II c Principle c Hardware c Software c Competitors Introduction Why Wound Measurement? • Chronic wounds are frequent: • 8% of bedridden/chairbound patients develop pressure ulcers • 3. 5% of all adults in the USA suffer from venous leg ulcers alone c Development c Examples c Performance c Status (1 of 4) • Wounds are costly: • Approx. £ 500 million annually in the UK venous leg ulcer

MAVIS - II Introduction c MAVIS-II c Principle Introduction (2 of 4) Why Wound Measurement? • Wounds need to be healed: • objective information required c Hardware • monitor progress of healing wound c Software • assess influence of clinical interventions c Competitors c Development • increasingly important: litigation c Examples • verify clinical trials c Performance c Status diabetic foot ulcer

MAVIS - II Introduction c MAVIS-II c Principle c Hardware c Software c Competitors Introduction (3 of 4) Existing techniques • Area: • transparency tracings or photographs • 2 D only • inaccurate (especially on curved wounds) • contact with wound pain, infection c Development c Examples c Performance c Status Smith & Nephew ‘Visitrak

MAVIS - II Introduction c MAVIS-II c Principle c Hardware c Software c Competitors c Development c Examples c Performance c Status Introduction (4 of 4) Existing techniques • Volume: • fill wound with measured amount of saline or alginate paste • messy & time-consuming • inaccurate • contact with wound pain, infection

MAVIS - II c Introduction MAVIS-I c MAVIS-II c Principle c Hardware c Software c Competitors c Development c Examples c Performance c Status MAVIS - I Data sheet • • 110 kg, trolley mounted £ 15, 000, only 6 sold non-contact structured light principle

MAVIS - II c Introduction c MAVIS-II c Principle MAVIS - II Data sheet • light, about 1. 5 kg, compact • non-contact c Hardware • inexpensive to build, few custom parts c Software • accuracy & precision better than MAVIS-I c Competitors • full-colour c Development c Examples • stereo-photogrammetry principle c Performance • “intelligence” in software not hardware c Status • no moving mechanical parts

MAVIS - II c Introduction c MAVIS-II Principle Stereo – Photogrammetry • displacement between corresponding points in stereo images = distance Principle c Hardware displacement d object point 1 c Software c Competitors c Development Left Image object point 2 left stereo image c Examples c Performance c Status Left Image Right Image right stereo image camera / eyes • challenge: finding corresponding points

MAVIS - II c Introduction c MAVIS-II c Principle Hardware c Software c Competitors Hardware (1 of 2) Off-the-shelf components • any high-resolution digital camera with standard lens adapter & flash • stereo adapter (slightly modified) • laptop or PC c Development c Examples c Performance c Status camera + stereo adapter

MAVIS - II c Introduction c MAVIS-II c Principle Hardware c Software c Competitors c Development c Examples c Performance c Status Hardware In-house • range finder (2 of 2)

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware Software c Competitors c Development c Examples c Performance c Status Software (1 of 2) Modular design • 3 -D displacement engine • user delineation tool

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware Software c Competitors Software Modular design • ‘minimum surface’ reconstruction positive volume negative volume ulcerated limb c Development c Examples c Performance c Status (2 of 2) • measurement, visualisation & output module false reconstruction correct reconstruction

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware c Software Competitors (1 of 2) Upper ranger: Minolta Vivid 700 • 9 kg, laser scanner • £ 70, 000 Lower range: Minolta 3 D 1500 • 0. 5 kg, structured light • £ 2, 500 c Development c Examples c Performance c Status And many others in-between • EOIS “Handy”, Inspec “ 3 D Body Builder”, …. . • common feature: no wound measurement software !

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware c Software Competitors c Development c Examples c Performance c Status Competitors (2 of 2) Most direct: Vista Medical “Ve. V 3 D” • • standard digital camera no volume… …but excellent data base 1 year free trial / subscription or purchase

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware c Software c Competitors Development c Examples c Performance c Status Future Developments MAVIS-II improvements (in order of urgency) • improve automation (e. g. : image transfer from camera initiated when camera placed next to laptop, then start software) • “package” system (own cameras, flash) • merging multiple images (e. g. for circumferential wounds) • addition of colour analysis (analysis of inflammation / infection status) • enable ”telemedicine” features and measurements as online services

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware c Software c Competitors c Development Examples c Performance c Status Examples No more wounds now • measurement grid overlay • all from a single ‘shot’

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware Performance (1 of 3) Wound Area Precision error range (one standard deviation as % of wound area) c Software c Competitors c Development c Examples Performance c Status 12 10 MAVIS 8 6 wound<10 cm² 4 wound 10 -40 cm² 2 0 wound >40 cm² rulers tracings digital photography

MAVIS - II c Introduction c MAVIS-II c Principle Performance (2 of 3) Wound Volume precision error range min. precision (large, shallow wounds) (one standard deviation in % of the wound volume) c Hardware c Software c Competitors 40% 30% c Development c Examples Performance c Status 20% 10% max. precision (deep, small wounds) 0% 3 D Scanners casts saline MAVIS rulers

MAVIS - II c Introduction c MAVIS-II c Principle Performance Calibration • against NPL precision artifacts c Hardware c Software c Competitors c Development c Examples Performance c Status • user control via consistency checker (3 of 3)

MAVIS - II c Introduction c MAVIS-II c Principle c Hardware c Software c Competitors c Development c Examples c Performance Status Summary so far… MAVIS – II is: • unique • inexpensive to manufacture, mainly from standard components • lightweight and portable • a precise tool for an increasingly important medical task • More information, examples, FAQs, etc: www. Med. Imaging. org/Mavis