A Novel Dermoscopic Probe for Determining Elasticity

Measurements of the Skin

Group 7:Erica BozemanMarkesha CookStephanie Cruz

February 28, 2007

Design Objective

"Structural alterations within cancerous skin-lesions cause unexpected patterns of anatomical deformation in response to mechanical forces."

Dr. Michael Miga

HypothesisIf structural alterations in skin cancer lesions differ from that of normal skin when a mechanical force is applied, then a systematic method of measuring the force response of a skin lesion can be compared to that of normal skin to determine the if the presence of skin cancer.

Conduct phantom experiments Design skin-friendly stretching apparatus Develop systematic method of testing skin forces

Skin Cancer Types of skin cancer

Basal Cell carcinoma ~800,000/yr

Squamous cell carcinoma ~200,000/yr

Melanoma ~60,000/yr Most aggressive Originates in melanocytes

Moles Types: Normal and Atypical Size: 2 mm-2 cm Depth of melanoma: 1 mm-

>4 mm

Color: pink-purple

http://www.aad.org/aad/Newsroom/2005+Skin+Cancer+Fact+Sheet.htm

•Increasing Rate of Incidence and Morbidity

•1973-1995: incidence increases from 5.7/100,000 to 13.3/100,000

•Adults over 65 account for large percentage of new cases: males (22%) females (14%) but only make up ~ 5.2% of population

•Poor incorporation of technology

•Underused methods of screening

www.abc.net.au/science/news/img/melanoma.jpg

Current Methods of Detection Clinical eye

Accuracy varies with experience Biopsy

Dermoscopy 10X magnification, liquid

polarizing lens Only ~75-80% accurate

Serial photography Software expensive (~$30,000) Slow Specialty clinics

In vivo confocal microscopy Experimental

http://www.jfponline.com/images/5206/5206JFP_AppliedEvidence-fig4.jpgwww.dermafend.com/images/illust/abcds_larger.jpg

Cost of Treating Skin CancerPhysicians•Lab fees•Time•Resources

Patients•Discomfort•Uninsured costs•scarring•time

•Cost of treatmentPhysician’s office: $492Inpatient: $5537 Outpatient: $1043

•Melanoma•$740 million/yr (US)•Advanced: $168,000•Early treatment: $1800•Screening $700

Insurance Companies•Cost

•Annual mean charged to Medicare:

NMSC: $357 millionMelanoma: $107

Our Proposed Device

Safe Easy Non-invasive Quick Effective Cost-efficient

Using plexiglass box:Overhead view

130 mm

25.4 mm

Lead screw

Force Sensor

Voltmeter

Design Feedback

Meeting with Phil Davis Lead screw Linear Actuator Use SolidWorks Contact Dr. Goldfarb for rapid-

prototyping

Portescap Representative Use a control board for the linear

actuator

Using plexiglass box:Overhead view

130 mm

25.4 mm

Force Sensor

Voltmeter

Linear Actuator

SolidWorks Schematic

Linear Actuator

Force Sensor

Translational Motion

Camera

Digital Linear Actuator

Generate controlled physical linear displacement

Linear step resolution-.001”

Unipolar coil construction

Power consumption- 2.5 Watts

Design Specifications:Ultra-Low Profile Load Cell - S215

Strain Gauge TechnologyMeasures up to 8 N (2 lb-

force) Dimensions:

27.94 x 5.99 mm (1.1 x .236 in)

Rigidly mounted on beam

Budget

Force Sensor $155.00

Linear Actuator $55.00

3M Micropore Surgical tape $10.00

Testing Methods

Uniaxial Tension Simple Finite

Element Method Viscoelastic

parameters of the skin

Independent Testing with the Bose ElectroForce ©

Elastographyhttp://www.bose-electroforce.com/product.cfm?

pid=41&sid=1

Phantom Skin: Vytaflex-10 and Vytaflex-60

Approximate difference between Elastic modulus is 6 x’s.

Tensile strength: 160 psi Elongation at break: 1,000%

Challenges We are Facing…

Requirements: Clamps must be

lightweight Must mate perfectly

with the tester Need to keep weight

symmetric about the centerline in all directions

One side of the clamp should not weigh more than the other side

Preparation of the Phantom Skin

Sample shape – 4 mm thick.

Top view

Side view

4mm

1cm1cm 2cm

5mm

Vytaflex-10

Vytaflex-60

Sketch of the Grip Design

Thread to transducer

Thread to translationpart of the tester

clamps clamps

Top view

Alternative Solution…

Buying customized grips from www.bose-electroforce.com

Cost: $4,000

Independent Testing with the Bose Electroforce ©

Assumption: Skin exhibits linear elastic properties

Compression testing and Indentation testing instead of tensile due to accessibility

Determine the viscoelastic properties of the skin such as the Young’s modulus, Poisson’s ratio and the plane stress.

Compare these to the values that result from our probe testing.

Future Matlab Processing

Important Design Dates February 9: Received materials for independent

testing February 24: Ordered force sensor and linear

actuator March 11-17

Begin independent testing (compression/indentation) Submit SolidWorks design for prototyping

March 18-24 Complete independent testing Begin testing our device

March 25-31 Comparative analysis using Dr. Miga’s model

April Finalize results; prepare for design presentation

References www.skincancer.org http://www.eurekalert.org/pub_releases/2006-10/osoa-ltt

101606.php http://www.smdsensors.com/detail_pgs/s100.htm http://www.omega.com/literature/transactions/volume3/s

train.html M. I. Miga, M. P. Rothney, J. J. Ou, "Modality independent

elastography (MIE): Potential applications in dermoscopy", Medical Physics, vol. 32, no. 5, pp. 1308-1320, 2005.

Tsap, Leonid V. et al. Efficient Nonlinear Finite Element Modeling of Nonrigid Objects via Optimization of Mesh Models. Computer Vision and Image Understanding. Vol 69, No. 3 March 1998 pp. 330-350.

Wan Abas, W.A.B and J.C. Barbenal. Uniaxial Tension Test of Human Skin In Vivo. J. Biomed. Engng. Vol 4 January 1982 pp.65-71.

Questions