Acquisition & Analysis of customised postural support systems

1. Lorna Tasker MEng MSc Pre-registrant Clinical Scientist, Rehabilitation Engineering Unit, Medical Physics & Clinical Engineering, Morriston Hospital, Swansea Acquisition & Analysis of customised postural support systems Posture & Mobility Group National Training Event 16th April 2009

2. Customised Postural Support Systems • Approximately 20% of wheelchair systems • Shape is taken directly from the client • To accommodate • To correct

3. Problem • Insufficient knowledge and scientific evaluation of these postural support shapes • Shape information is not retained • No comparable measurement or outcome data • Customised seating systems are: • Expensive • Labour-intensive • Require highly skilled professionals • Not reproducible

4. Digital Seating Service • Microscan 3D laser scanner • CAD/CAM software • CNC machine • More affordable • Research opportunities

5. Aims • Develop a technique for 3D shape data collection and analysis of custom seating systems • Understanding of human shape of individuals with complex disabilities • To influence fabrication techniques • Investigate two laser scanners • Research question:Can 50% of customised support systems be represented (and manufactured) using standardised geometric shapes that are within ±10mm from the actual shape?

6. Methodology: Equipment • Equipment: • Faro Scan Arm- high-cost • £100,000 • Accuracy: ±61µm • Microscan-low-cost • £15,000 • Accuracy: ±100µm

7. Methodology: Shapes (25 total) Swansea (SW) North Wales (NW) Chailey Heritage Services (CH) Microscan laser scans FARO laser scans

8. Methodology: Scanner comparison • 10 shapes compared: • Faro scans=Gold standard/reference • Microscan =test • Using Geomagic Qualify software- • 3D shape information was overlaid and compared to produce 3D comparison/deviation results • Results validated the use of the Microscan for research purposes and clinical work in special seating

9. Results: Scanner comparison

10. Results: Bounding Box Sizes • Simple analysis- use global feature e.g. area or volume • Bounding box sizes • Minimum and maximum point in each direction • Depth X= 296-559mm • Height Y=133-321mm • Width Z= 305-609mm • Inform manufacturing techniques Z X Y X

11. Methodology: Shape analysis- Geometric representation • Represent the shape volume using columns rods- reduced the variables for analysis to take place • Shape function- describes the frequency of column heights

12. Results: Column representation

13. Results: Proposed manufacturing technique • Geometric representation of contours provides an alternative, low-cost manufacturing method • Valuable information which can specify the shape of the seat • Shape histograms provides the number of components (columns) required

14. Demonstration

15. Results: Proposed manufacturing technique

16. Results: Proposed manufacturing technique • Data confirms that > 50% of customised support systems can be represented (and manufactured) using standardised geometric shapes • Areas which exceed ±10mm tolerance • Statistical measures used to highlight these areas

17. THE BIG PICTURE... 3D shape data DATABASE? -MATCH SHAPES Off-the-shelf standard shapes Modular approach e.g. Columns CNC technologies ON-SITE -FASTER TURN AROUND TIME FOR CLIENT LOW-COST GEOGRAPHICALLY CENTRAL

18. Summary • Developed shape acquisition and analysis processes to advance the knowledge of individuals’ shapes with complex disabilities • Results confirmed the use of the lower cost laser scanner • Routine shape capturing method of clinical work-eliminate plaster casting • Potential manufacturing technique explored by the definition and use of geometric shapes

19. Thank you Acknowledgements: Posture & Mobility Group (PMG) for funding Nigel Shapcott, Head of Rehabilitation Engineering, Swansea Staff at Rehab Engineering, Swansea National Leadership and Innovation Agency For Healthcare (NLIAH) and Welsh Assembly Government for funding my postgraduate degree Digital Design Partnership for 3D scanning/comparison services Paul Marl (North Wales Rehabilitation Engineering Unit) and Dr Donna Cowan (Chailey Clinical Services, East Sussex) for supplying plaster casts. ALAS (Artificial Limb and Appliance Service), Cardiff

20. Z X Methodology: Column representation • Using raw point data • Java program designed to provide heights of columns

21. Results: Shape Analysis 10 x10mm

22. Results: Shape Analysis 50 x 50mm

23. Scanner comparison

24. Results: Use of statistical measures Average column height Standard deviation

25. Results: Scanner comparison • Chailey Shape (±0.5mm)

26. Results: Scanner comparison • Chailey shape (±1.0mm)

27. Results: Testing ±10mm tolerance • 41.2% > ±10mm @ 20x20 resolution • 31.3% > ±10mm @ 10 x10 resolution

28. Probability Density Height (mm) Results: Generic Shape Analysis • Exploratory data analysis • Pattern-recognition • Gaussian kernel was used to ‘smooth’ the histograms • Tested potential groupings • Demonstrated potential use of cluster analysis