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Ultrasound Imaging of Hip Displacement in Children With Cerebral Palsy
Thanh-Tu Pham1, Lawrence H Le1, Thanh-Giang La2
1Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, Alberta, Canada; Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
Insights
This study presents a new ultrasound (US) method to estimate hip displacement in children. The developed migration percentage (MP) index shows accurate results validated by simulations and phantom studies.
Area of Science:
- Medical imaging
- Biomedical engineering
- Pediatric orthopedics
Background:
- Hip displacement in children requires accurate diagnostic methods.
- Ultrasound (US) imaging offers a non-invasive approach for hip assessment.
Purpose of the Study:
- To describe and validate an ultrasound-based method for estimating hip displacement.
- To introduce a new diagnostic index, the migration percentage (MP).
Main Methods:
- Developed a migration percentage (MP) index using acetabulum-femoral head distance and femoral head width from US images.
- Validated the method using numerical simulations, 3-D-printed hip phantoms, and pilot in vivo data.
Main Results:
- Numerical simulations showed a maximum diameter error of 16.1 ± 8.5% under specific noise and roughness conditions.
- Phantom studies demonstrated low percentage errors for MP (0.3%-6.6% vs. X-ray).
- Pilot clinical trials showed a mean absolute difference of 3.5 ± 2.8% between X-ray and US MPs.
Conclusions:
- The developed ultrasound method is a viable tool for evaluating hip displacement in pediatric patients.
- The migration percentage (MP) index provides accurate and reliable measurements.
Objective:
An approach to estimation of hip displacement on ultrasound (US) images is described. Its accuracy is validated through numerical simulation, an in vitro study with 3-D-printed hip phantoms and pilot in vivo data.
Methods:
A diagnostic index, migration percentage (MP), is defined by the ratio of acetabulum-femoral head distance to femoral head width. The acetabulum-femoral head distance could be measured directly on hip US images, while the femoral head width was estimated from the diameter of a best-fit circle. Simulation was performed to evaluate the accuracy of circle fitting with noiseless and noisy data. Surface roughness was also considered. Nine hip phantoms (three different sizes of femur head × three MP values) and 10 US hip images were used in this study.
Results:
The maximum diameter error was 16.1 ± 8.5% when the roughness and noise were 20% of the original radius and 20% of the wavelet peak, respectively. In the phantom study, the percentage errors of MPs between the 3-D-design US and X-ray US were 0.3%-6.6% and 0.0%-5.7%, respectively. From the pilot clinical trial, the mean absolute difference between the X-ray-US MPs was 3.5 ± 2.8% (1%-9%).
Conclusion:
This study indicates that the US method can be used to evaluate hip displacement in children.
