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Technical Note: A comparison of point set registration methods for electromagnetic tracking.
T I Götz1,2,3, H Wankerl1, A M Tomé4
1CIML, Biophysics, University of Regensburg, 93040, Regensburg, Germany.
Medical Physics
|February 13, 2019
Summary
Multidimensional scaling (MDS) and coherent point drift (CPD) accurately register radiation source positions in high dose rate brachytherapy. MDS offers superior accuracy and less variance in determining dwell positions compared to CPD.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image Registration
Background:
- High dose rate brachytherapy requires precise radiation source placement to protect healthy tissues.
- Accurate quantification of source position changes across treatment sessions is crucial for effective brachytherapy planning.
- Electromagnetic tracking (EMT) is used to localize radiation sources, but requires registration due to patient repositioning.
Purpose of the Study:
- To compare two point set registration techniques for improving the accuracy of radiation source localization in brachytherapy.
- To evaluate the effectiveness of Multidimensional Scaling (MDS) and Coherent Point Drift (CPD) for registering electromagnetic tracking data.
- To determine which registration method provides more reliable and precise dwell position determination.
Main Methods:
- Electromagnetic tracking (EMT) was employed to record radiation source dwell positions during brachytherapy sessions.
- Two point set registration algorithms, Coherent Point Drift (CPD) and Multidimensional Scaling (MDS), were compared.
- The registration techniques were assessed based on their ability to align dwell point sets from different sessions without external registration.
Main Results:
- Both CPD and MDS enabled the use of EMT for dwell position determination without external registration, yielding comparable results.
- MDS demonstrated smaller grand average deviations (2.15 mm) compared to rigid CPD (2.55 mm).
- MDS also exhibited less variance in dwell position determination (IQR = 3 mm) than CPD (IQR = 4 mm), and does not require iterative procedures.
Conclusions:
- Both MDS and rigid CPD are effective for registering radiation source positions in brachytherapy using EMT.
- MDS is recommended over rigid CPD due to its superior accuracy and reduced variance in determining source dwell positions.
- Nonrigid CPD is not suitable for this application as it does not preserve the topology of the point sets.
