Precision and accuracy of computed tomography foot measurements

Objective: To test the accuracy and precision of computed tomography (CT) imaging for describing the 3-dimensional structure of the foot in patients with diabetes mellitus and peripheral neuropathy. Design: Experimental, test-retest. Setting: Clinical CT scanner at a local hospital. Specimens: Two tissue-equivalent phantoms and 6 cadaver feet. Main Outcome Measures: Measurements taken from CT data of phantoms and cadaver feet were compared with physical (caliper) measurements. The feasibility of creating a computer-aided design/rapid prototyping 3-dimensional model from CT data was assessed by using 1 cadaver foot. Results: No bias was found for phantom or cadaver CT measurements compared with caliper measurements. The mean difference between repeat scans of cadaver feet (1 observer) was 0.1 ± 0.8mm and between observers, 0.4 ± 0.8mm. Comparing caliper measurements of the rapid prototype model and actual foot measurements revealed an error of 0.3 ± 0.4mm. Conclusion: CT-based 3-dimensional imaging produced accurate and precise foot measurements, enabling description of internal and external structures. This capability will be coupled with plantar pressure measurements to improve our understanding and treatment of foot ulcers in people with diabetes.