Method for automatic localization of MR-visible markers using morphological image processing and conventional pulse sequences: feasibility for image-guided procedures.
OBJECTIVE
To evaluate the feasibility and accuracy of an automated method to determine the 3D position of MR-visible markers.


METHODS
Inductively coupled RF coils were imaged in a whole-body 1.5T scanner using the body coil and two conventional gradient echo sequences (FLASH and TrueFISP) and large imaging volumes up to (300 mm(3)). To minimize background signals, a flip angle of approximately 1 degrees was used. Morphological 2D image processing in orthogonal scan planes was used to determine the 3D positions of a configuration of three fiducial markers (FMC). The accuracies of the marker positions and of the orientation of the plane defined by the FMC were evaluated at various distances r(M) from the isocenter.


RESULTS
Fiducial marker detection with conventional equipment (pulse sequences, imaging coils) was very reliable and highly reproducible over a wide range of experimental conditions. For r(M) </= 100 mm, the estimated maximum errors in 3D position and angular orientation were 1.7 mm and 0.33 degrees , respectively. For r(M) </= 175 mm, the respective values were 2.9 mm and 0.44 degrees .


CONCLUSIONS
Detection and localization of MR-visible markers by morphological image processing is feasible, simple, and very accurate. In combination with safe wireless markers, the method is found to be useful for image-guided procedures.
Busse
Harald
H
Department of Diagnostic and Interventional Radiology, Leipzig University Hospital, Leipzig, Germany. harald.busse@medizin.uni-leipzig.de
Trampel
Robert
R
Gründer
Wilfried
W
Moche
Michael
M
Kahn
Thomas
T
D000465:Algorithms; D001331:Automation; D001706:Biopsy; D004867:Equipment Design; D006339:Heart Rate; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods*; D015233:Models, Statistical; D016011:Normal Distribution; D010363:Pattern Recognition, Automated; D019047:Phantoms, Imaging; D015203:Reproducibility of Results