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.