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

MAVIS-II Measurement of Area and Volume Instrument System for Skin Wounds

MAVIS-II Measurement of Area and Volume Instrument System for Skin Wounds

C.D. Jones, P. PlassmannUniversity of Glamorgan,Medical Computing Research Group

MAVIS - II

Introduction MAVIS-I MAVIS-II

Status

Introduction (1 of 4)

Principle Hardware Software Competitors Development Examples Performance

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

• Wounds are costly:

• Approx. £ 500 million annually in the UK

venous leg ulcer

MAVIS - II


Status



Why Wound Measurement?• Wounds need to be healed:

• objective information required

• monitor progress of healing wound

• assess influence of clinical interventions

• increasingly important: litigation

• verify clinical trials

diabetic foot ulcer

MAVIS - II


Status



Existing techniques• Area:

• transparency tracings or photographs• 2D only• inaccurate (especially on curved wounds)

• contact with wound pain, infection

Smith & Nephew ‘Visitrak

MAVIS - II


Status



Existing techniques• Volume:

• fill wound with measured amount of saline or alginate paste

• messy & time-consuming• inaccurate• contact with wound pain, infection

MAVIS - II

Introduction

MAVIS-I MAVIS-II

Status

MAVIS - I


Data sheet• 110 kg, trolley mounted• £ 15,000, only 6 sold• non-contact• structured light principle

MAVIS - II

Introduction MAVIS-I

MAVIS-II

Status

MAVIS - II


Data sheet• light, about 1.5 kg, compact

• non-contact

• inexpensive to build, few custom parts

• accuracy & precision better than MAVIS-I

• full-colour

• stereo-photogrammetry principle

• “intelligence” in software not hardware

• no moving mechanical parts

MAVIS - II


Status

Principle


Stereo – Photogrammetry• displacement between corresponding

points in stereo images = distance

• challenge: finding corresponding points

d

Left Image

Left Image

Right Image

Right Image

camera / eyes

displacementobject point 1

object point 2 left stereo image

right stereo image

MAVIS - II


Status

Hardware (1 of 2)

Principle

Hardware Software Competitors Development Examples Performance

Off-the-shelf components

• any high-resolution digital camera with standard lens adapter & flash

• stereo adapter(slightly modified)

• laptop or PC

camera + stereo adapter

MAVIS - II


Status

Hardware (2 of 2)

Principle

Hardware Software Competitors Development Examples Performance

In-house

• range finder

MAVIS - II


Status

Software (1 of 2)

Principle Hardware

Software Competitors Development Examples Performance

Modular design • 3-D displacement engine

• user delineation tool

ulcerated limb

correct reconstructionfalse reconstruction

positivevolume

negativevolume

MAVIS - II


Status

Software (2 of 2)

Principle Hardware

Software Competitors Development Examples Performance

Modular design

• ‘minimum surface’ reconstruction

• measurement, visualisation & output module

MAVIS - II


Status

Competitors (1 of 2)

Principle Hardware Software

Competitors Development Examples Performance

Upper ranger: Minolta Vivid 700 • 9 kg, laser scanner• £ 70,000

Lower range: Minolta 3D 1500 • 0.5 kg, structured light• £ 2,500

And many others in-between• EOIS “Handy”, Inspec “3D Body Builder”, …..• common feature:

no wound measurement software !

MAVIS - II


Status

Competitors (2 of 2)

Principle Hardware Software

Competitors Development Examples Performance

Most direct: Vista Medical “VeV 3D”• standard digital camera• no volume…• …but excellent data base• 1 year free trial / subscription or purchase

MAVIS - II


Status

Future Developments

Principle Hardware Software Competitors

Development Examples Performance

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


Status

Examples

Principle Hardware Software Competitors Development

Examples Performance

No more wounds now

• measurement grid overlay

• all from a single ‘shot’

MAVIS - II


Status

Performance (1 of 3)

Principle Hardware Software Competitors Development Examples

Performance

wound >40 cm²

wound 10-40 cm²

wound<10 cm²

0

2

4

6

8

10

12

rulers tracings digital photography

Precision error range

(one standard deviation as % of wound area)

MAVIS

Wound Area

MAVIS - II


Status



Performance

Wound Volume

saline

0%

10%

20%

30%

40%

3D Scanners casts rulers

min. precision

max. precision

(large, shallow wounds)

(deep, small wounds)

precision error range(one standard deviation in % of the wound volume)

MAVIS

MAVIS - II


Status



Performance

Calibration• against NPL

precision artifacts

• user control viaconsistency checker

MAVIS - II


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.MedImaging.org/Mavis

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

Documents

introduction mavis

status mavis

status introduction

status hardware

status software

light principle slide

stereo image slide

infection slide