title: Automatic post-implant needle reconstruction algorithm to characterize and improve implant robustness analyses.
abstract: Post-implant analysis in permanent implant brachytherapy is an important process that provides a feedback on treatment quality. Random seed movements, edema, and needle related factors contribute to deteriorate dose coverage. For a complete study of these movements, it is important to reconstruct the post-implant seeds clusters but, up to now, this task was only possible via a long and difficult manual process. To facilitate post-implant analysis a simulated annealing algorithm was developed to perform automatic reconstructions. This process is fast (30-60 s on a 1.3 GHz pentium) and has a high level of success, even with up to 5% of seed loss. Tests on 21 clinical cases show that the algorithm yields exactly the same results as manual reconstructions. A realistic simulation tool was used to generate 58 synthetic post-implant data, in which cases the exact configuration was known. Even if some errors were found, pertinent information was extracted. For medium seed density [corresponding to seeds of 0.6 mCi (0.762 U)], 97% of seeds are matched with their correct needle and 89% are matched with their correct planned position. This method provides pertinent information that can be used to understand inhomogenous dose coverage in specific prostate quadrants; to make realistic post-implant simulations or to identify seeds belonging to a needle loaded with different seed types or activity.
authors.affiliation: Départment de Radio-Oncologie, Centre de Recherche en Cancérologie, Hôtel-Dieu de Quebec, 11 côte du palais, Québec, QC G1R 2J6, Canada.
authors.forename: Louis
authors.initials: L
authors.lastname: Archambault
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
authors.forename: Dragan
authors.initials: D
authors.lastname: Tubic
mesh_terms: D000465:Algorithms; D001918:Brachytherapy / Q000379:methods*; D003198:Computer Simulation; D006801:Humans; D008297:Male; D009339:Needles; D010363:Pattern Recognition, Automated; D019047:Phantoms, Imaging; D011471:Prostatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique