C-arm Fluoroscopy: Developing a Method for

Orthotic AnalysisLisa Friedland

Department of Medical BiophysicsUniversity of Western Ontario

London , Ontario

AcknowledgementsThomas Jenkyn, Ph.D., P.Eng

Megan Balsdon, MSc. Candidate

Kristen Bushey, MSc. Candidate

QuestionHow does a podiatrist/orthotist know

that a custom made orthotic is functioning effectively during dynamic gait?

Create a method to analyze the orthotic in real time motion.

What is C-arm Fluoroscopy? Live feed X-ray technique

aka X-ray Image Intensifier Uses an image intensifier to

amplify low intensity X-rays CCD camera coupled to the image

intensifier displays feed on monitor

Features Recording Zoom & contrast adjustments Last image hold

Medical Uses Cardiac catheterization Barium investigations Guide placement of medical

devices

1. c-arm fluoroscope

Orthotic TypeRigid

Preferred for flat footed individuals

Support, stability, & control Proper fitting extremely

important

Soft

Preferred for high-arched individuals—flexible

Cushioning, balance, & shock absorption

Shorter lifespan

Rigid

Soft

Molding Technique: Plaster Casting vs. Foam BoxPlaster Casting

Leading techniqueFoot placed in subtalar

joint neutral positionCostly, messy

Foam BoxQuick, cleanAllows for natural soft

tissue deformationAccommodative mold

Experimental Design

21 patients

7 flat foot

7 normal

7 high arch

• Barefoot• Neutral shoe• Soft foam box shoe • Soft plaster cast shoe• Rigid foam box shoe• Rigid plaster cast shoe

Experimental DesignPatients walk on a

platform 2 C-arm fluoroscopes

Camera A – lateral view

Camera B –anterior/oblique view

Pull string on each fluoroscope to mark time for syncing

A A

B

B

2D Arch AnalysisUsing camera A

(lateral) freeze frame as entire foot touches down

Measure calcaneal first metatarsal angle (C1MA) in Matlab

3. C1MA protocol

Barefoot Dynamic

Rigid Foam Box Dynamic

Progress so farAs expected

Barefoot – 121.66°Neutral shoe – 115.96°Soft plaster – 113.65°Rigid plaster – 112.22°

More support—C1MA angle decreases

InconclusiveData collection ongoingProblematic images

1st Metatarsal Out of Image

Problem with 2D AnalysisOut of plane rotation

Foot must strike exactly 90° with camera A

Put markers on floorStill not realistic

Future 3D AnalysisRadiostereometric Analysis (RSA)

Calibration boxImage from cameras A & B—calibrate using MatlabDigitize the image frames in Adobe PhotoshopImport 3D CT image into Rhinoceros modelling

software Bone match CT image to Fluoroscope image

4. RSA system

Images1. c-arm fluoroscope: http://www.industry-medical.com/mymedical/ajmedical/prodetail2284/

AJ4501_High_Frequency_Mobile_C-Arm_Xray_Imaging_System.html 2. normal/high/flat: http://www.footlogics.ie/pronation-flatfeet-fallen-arches.html &

http://www.youcanbefit.com/shoes.html 3. C1MA protocol: Murley, G., Menz, H., & Landorff, K. (2009). A protocol for classifying normal-and flat- arched foot posture for research studies using clinical and radiographic measurements. Journal of Foot and Ankel Research, 2, 22, 1-13. 4. Allen, A, M. (2009). Development and validation of a markerless RSA system. Thesis. Biomedical

Engineering, University of Western Ontario: London.