Room: Exhibit Hall | Forum 4
Purpose: To find a tool that allows to reconstruct the brachytherapy cervix Utrecht applicator (Elekta AB, Stockholm, Sweeden) source channels corresponding to the intracavitary component (ICCs) simultaneously.
Methods: The tool described in this communication makes use of an algebraic library reconstruction method. In the MRI axial planes the sections left by the dummies of the ICCs are marked. The order during the process of identification is not important and it is also not necessary to determine the tip. With this data, B-Splines surfaces are generated for each ICC and subsequently exported as mesh surfaces. With the data obtained, and using the library model, the corresponding three-dimensional minimization problem is solved using the Broydenâ€“Fletcherâ€“Goldfarbâ€“Shanno algorithm in two steps. Once this is done, the position of the library model in the MRI base, the angle formed by the ovoids (OVs) and the relative position of the intrauterine component (IU) can be determined.
Results: The reconstruction method was applied to 14 patients. In the case of the OVs, differences were less than a millimeter except in the case of the IU. The larger difference observed in the case of the IU is due to the lower curvature of the source channel, which introduces a greater uncertainty in the cranio-caudal direction during the fitting process. In contrast, since the OVs are reconstructed together, the uncertainty diminishes. The method proposed improves the current algorithms without resorting to the inefficient and time-consuming superposition of the 3D model of the applicator over the MRI image sequence one channel at a time.
Conclusion: The method described is accurate and can be used in both computed tomography and MRI. This proof-of-concept shows that this method can be the basis for a fully automatic reconstruction procedure.