Transcript A non-invasive instrument .

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
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 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
 Development
 Examples
 Performance
 Status
(1 of 4)
• Wounds are costly:
• Approx. £ 500 million
annually in the UK
venous leg ulcer
MAVIS - II
Introduction
 MAVIS-I
 MAVIS-II
 Principle
Introduction
(2 of 4)
Why Wound Measurement?
• Wounds need to be healed:
• objective information required
 Hardware
• monitor progress of healing wound
 Software
• assess influence of clinical interventions
 Competitors
 Development
• increasingly important: litigation
 Examples
• verify clinical trials
 Performance
 Status
diabetic foot ulcer
MAVIS - II
Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
Introduction
(3 of 4)
Existing techniques
• Area:
• transparency tracings or photographs
• 2D only
• inaccurate (especially on curved wounds)
• contact with wound  pain, infection
 Development
 Examples
 Performance
 Status
Smith & Nephew ‘Visitrak
MAVIS - II
Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
 Development
 Examples
 Performance
 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
 Introduction
MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
 Development
 Examples
 Performance
 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
 Principle
MAVIS - II
Data sheet
• light, about 1.5 kg, compact
• non-contact
 Hardware
• inexpensive to build, few custom parts
 Software
• accuracy & precision better than MAVIS-I
 Competitors
• full-colour
 Development
 Examples
• stereo-photogrammetry principle
 Performance
• “intelligence” in software not hardware
 Status
• no moving mechanical parts
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
Principle
Stereo – Photogrammetry
• displacement between corresponding
points in stereo images = distance
Principle
 Hardware
displacement
d
object point 1
 Software
 Competitors
 Development
Left
Image
object point 2
left stereo image
 Examples
 Performance
 Status
Left
Image
Right
Image
Right
Image
right stereo image
camera / eyes
• challenge: finding corresponding points
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
Hardware
 Software
 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
 Development
 Examples
 Performance
 Status
camera + stereo adapter
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
Hardware
 Software
 Competitors
 Development
 Examples
 Performance
 Status
Hardware
In-house
• range finder
(2 of 2)
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
Software
 Competitors
 Development
 Examples
 Performance
 Status
Software
(1 of 2)
Modular design
• 3-D displacement engine
• user delineation tool
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
Software
(2 of 2)
Modular design
• ‘minimum surface’ reconstruction
false reconstruction
correct reconstruction
positive
volume
 Hardware
Software
 Competitors
negative
volume
ulcerated limb
 Development
 Examples
 Performance
 Status
• measurement,
visualisation &
output module
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
Competitors
(1 of 2)
Upper ranger: Minolta Vivid 700
• 9 kg, laser scanner
• £ 70,000
 Principle
 Hardware
 Software
Competitors
Lower range: Minolta 3D 1500
• 0.5 kg, structured light
• £ 2,500
 Development
 Examples
 Performance
 Status
And many others in-between
• EOIS “Handy”, Inspec “3D Body Builder”, …..
• common feature:
no wound measurement software !
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
Competitors
 Development
 Examples
 Performance
 Status
Competitors
(2 of 2)
Most direct: Vista Medical “VeV 3D”
•
•
•
•
standard digital camera
no volume…
…but excellent data base
1 year free trial / subscription or purchase
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
Development
 Examples
 Performance
 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
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
 Development
Examples
 Performance
 Status
Examples
No more wounds now
• measurement
grid overlay
• all from a single ‘shot’
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
Performance
Wound Area
Precision
error range
(one standard
deviation as %
of wound
area)
 Competitors
12
 Development
10
 Examples
Performance
 Status
(1 of 3)
MAVIS
8
6
wound<10 cm²
4
wound 10-40 cm²
2
0
wound >40 cm²
rulers
tracings
digital
photography
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
Performance
(2 of 3)
Wound Volume
precision error range
min. precision
(large, shallow wounds)
(one standard deviation in % of the wound volume)
 Hardware
 Software
 Competitors
40%
30%
 Development
 Examples
Performance
 Status
20%
10%
max. precision
(deep, small wounds)
0%
3D Scanners
casts
saline
MAVIS
rulers
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
Performance
Calibration
• against NPL
precision artifacts
 Hardware
 Software
 Competitors
 Development
 Examples
Performance
 Status
• user control via
consistency
checker
(3 of 3)
MAVIS - II
 Introduction
 MAVIS-I
 MAVIS-II
 Principle
 Hardware
 Software
 Competitors
 Development
 Examples
 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.MedImaging.org/Mavis