Current difficulties and the possible future directions in scar assessment

Copyright

0 1996

Burns Vol. 22, No. 6, pp. 455-458, 1996 Elsevier Science Ltd for ISBI. All rights reserved Printed in Great Britain 0305-4179196

$15.00+0.00

ELSEVIER 0305-4179(95)00168-9

Current difficulties and the possible directions in scar assessment* IF. M. Wood,

K. Currie,

B. Backman

future

and B. Cena

Royal Perth and Princess Margaret Hospital, Bum Unit and Skin lCuiture Laboratory, University of Western Australia, Ferfh, Australia

The qti!antitafive assessment of fhe results of burn management is notorious/y difict4lt. With fhe focus changing from survival to cosmehc and functional outcome, Ihe scar assessmentsare increasingly ivzporfal~f. The scar is a sum of fhe injury and all subsequenf interve,qtions on ihe way fo healing. As such it is a complex structure, abrlorrnal in its colour, depth, contour and plinbikty. To develop a quanfifafiue syskm we believe if is vital lo be able fo track accurately an are,a of injury fhrough time. Further, that physiological data acquired by a number of measuremenf fools be fused accurately to the morphologically correct informafian. Copyright 0 1996 Elsevter Scimce Ltd.ior I’SBI.

The use of internal rigid body anchors, bony landmarks, externally marked for UV light registration. In this way, the information can be linked from a number of sources at differing times. Temporal visualization, i.e. studying the morphological and its associated pathophysioiogicai data through time. Dynamic functional imaging linking multiple data sources to provide a composite quantitative system.

Burns, Vol. 22, No. 6, 455-458, 1996.

Introduction The final scar quality of a burn injury is influenced at every St-agein the history of that injury by: 1. 2. 3. 4. 5.

Depth and extent of the burn. Method and timing of resuscitation. Presence of infection. Surgical intervention techniques and timing. Posthealing scar manipulation strategies.

Burns research has been hampered by the difficulties in assessment of the initial injury and matching accurately the injury to the final scar result in terms of functional and cosmetic outcomes. The current scar assessments are static, non-functional and subjective. A static assessment is one done at a given point in time to demonstrate the current situation. It is difficult to be sure that at a later date the same area is assessed. The methods give no insight into the pathophysioiogicai processes taking place at the surface. The first step in the process is to visualize the body surface, and then to track the changes on the surface through time. In this paper, a number of concepts are introduced: accurate

1. The use (of structured light for morphological acquisition. “This paper was presented trophic Scar, Hong Kong,

at the International June 1995.

Symposium

Figure 1. Vancouver General Hospital scar assessmentat six

facial locations.

data

for Hyper-

Figure 2. Ultrasound thickness measured tions.

at

three facial loca-

Burns: Vol. 22, No. 6, 1996

Figure 3. Scarof skin graft area 4 weeks posthealing.

Figure 4. Scar of skin graft area 12 weeks posthealing.

The aim is to develop a non-invasive multimodal temporal visualization system of assessment of the injury and the scar resulting.

It is possible that the use of a m&modality temporal system is worthy of further investigation.

Scientific ase report The difficulties in scar assessmentcan be highlighted when the progress of a I s-year-old boy, who sustained a 35 per cent body surface area bum of his upper body, face, neck and hands, is followe(d. The burn to his face required debridement and split-skin

grafting to achieve wound healing. He wore an acrylic face mask from 3 days postinjury until 1.2 weeks post skin grafting. He discarded the mask and was non-compliant with treatment for a period of 6 weeks. Scar assessment was performed at 4 weeks after the split skin graft had healed, and was repeated at 7 and 12 weeks posthealing. Assessments included the Vancouver General Hospital using (VGH) scar index, a standardized subjective assessment short non-equal-interval scales rating colour, vascularity, pliability and height. The assessments were carried out in six locations on

the face. FigureI demonstrates how the scores rose initially

then plateaued. Ultrasound assessment of scar thickness was performed using 10.MH2: B-mode ultrasound. In the three sites under investigation, one area thickened, one became thinner and one remained the same (Figr,trEo2). However, relentless progression of the

scarring is all too easy to seein the seriesof clinical photographs in Figures 3 and 4.

quantitative

visualization

This process involves: COARSE LEVEL: Pre-imaging registration using a mechanical frame. MEDIUM LEVEL: Using internal anchor points, bony landmarks, externally marked with fluorescent paint to be identified by UV light and therefore not interfering with other imaging modalities. MEDIUM LEVEL: Uses the structure stripped light to acquire surface data for computer manipulation. FINE LEVEL: Fine level is proposed for the future fusing of physiological data to the morphological data as a form of functional imaging. The surface data must be rapid and capable of being collected at regular intervals, as the surface of our patients distorts in a non-linear fashion. Realignment based on the internal anchor points is crucial in developing the system. In that way external mechanical fixation frames are discarded. The series of illustrations in Figwe 5 show an example of the technique applied to the torso. Having established the surface, the physiological changes at the surface needed to be tracked through time.

Wood:

457

Scar assessment

Figure 5. Series I: acquisition of surface data using structured light. a, X-ray of the chest indicating the positions of internal anchor points externally marked. b, UV light image to identify fluorescent markers of internal body landmarks. c, Structured light on the torso. The distortion of the line indicates the surface contour. d, Computer-generated grid of the surface reconstructed from the structured light data. e, Final model of the torso under investigation.

Early experience had been acquired in using a surgical precision tracking arm. The surfaces of scars and normal skin have been scanned with a ~-MHZ B-mode ultrasound transducer

linked

to the tracking

arm. In this way

the

position of the transducer is known in space. The position of the arm relative to fixed patient landmarks, external markers relating to static internal bony landmarks, is a method allowing accurate relocation. Further, knowing the position

of the ultrasound

2D information

buildi a 3D rr,odel of the area (Figure 6).

enables

us to

Discussion ‘The scanning of the body surface of a patient is a vast undertaking. Further, to couple the surface information with

information

from

a number

of

scanning

tools

increases the complexity of the system. However, if the problem of bum assessment from injury to rehabilitation is to be assessed, and we need to investigate the possibility of developing a multimodal temporal visualization system.

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Vol. 22, No. 6,1996

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e 6. SeriesII: use of the precision tracking arm applied to collection of ultrasound data. a, Demonstration of ultrasound in use with the tracking arm scanning a scar on the thigh. b, Conventional 2D ultrasound linked to the precision tracking arm allows data acquisition for 3D reconstruction. c, 2D ultrasound of normal skin. d, 2D ultrasound of scarred area demonstrating an increase in skin thickness. e, Computer algorithms highlighting areasof interest.

Figure

Imaging a person with any technique, e.g. CT, MRI or structured light, on more than one occasion faces the same difficulties of: I. Extrinsic re-aligning the body in mechanical frames. 2. Intrinsic changes in the bodies’ morphology. Developing the use of registration and precision tracking will dispense with the need of mechanical fixation with its inherent in inaccuracies. Such a system will have great potential in research, teaching, as an adjunct to clinical practice and for compatibility with tele medicine useful for the remote areas (a problem faced daily in Western Australia). In the future, the possibility of extending the data and using it as a predictive tool is to be explored.

Paper accepted 19 February 19%.

c

orrespondence should be atiressed to: Dr Fiona N. Wood, 44

Churchill Avenue, Subiaco6008,

Western Australia.