Real-time method for motion-compensated MR thermometry and MRgHIFU treatment in abdominal organs.
OBJECTIVE
Magnetic resonance-guided high-intensity focused ultrasound is considered to be a promising treatment for localized cancer in abdominal organs such as liver, pancreas, or kidney. Abdominal motion, anatomical arrangement, and required sustained sonication are the main challenges.


METHODS
MR acquisition consisted of thermometry performed with segmented gradient-recalled echo echo-planar imaging, and a segment-based one-dimensional MR navigator parallel to the main axis of motion to track the organ motion. This tracking information was used in real-time for: (i) prospective motion correction of MR thermometry and (ii) HIFU focal point position lock-on target. Ex vivo experiments were performed on a sheep liver and a turkey pectoral muscle using a motion demonstrator, while in vivo experiments were conducted on two sheep liver.


RESULTS
Prospective motion correction of MR thermometry yielded good signal-to-noise ratio (range, 25 to 35) and low geometric distortion due to the use of segmented EPI. HIFU focal point lock-on target yielded isotropic in-plane thermal build-up. The feasibility of in vivo intercostal liver treatment was demonstrated in sheep.


CONCLUSIONS
The presented method demonstrated in moving phantoms and breathing sheep accurate motion-compensated MR thermometry and precise HIFU focal point lock-on target using only real-time pencil-beam navigator tracking information, making it applicable without any pretreatment data acquisition or organ motion modeling.
Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland; MRC Department, MPI for Biological Cybernetics, Tübingen, Germany.
Zarko
Z
Celicanin
Vincent
V
Auboiroux
Oliver
O
Bieri
Lorena
L
Petrusca
Francesco
F
Santini
Magalie
M
Viallon
Klaus
K
Scheffler
Rares
R
Salomir
D000005:Abdomen / Q000502:physiology / Q000528:radiation effects / Q000601:surgery; D000818:Animals; D016477:Artifacts; D001831:Body Temperature / Q000502:physiology / Q000528:radiation effects; D003199:Computer Systems; D019220:High-Energy Shock Waves; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D007089:Image Enhancement / Q000379:methods; D066298:In Vitro Techniques; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009038:Motion; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012756:Sheep; D025321:Surgery, Computer-Assisted / Q000379:methods; D013817:Thermography / Q000379:methods*; D014421:Turkey; D014781:Viscera / Q000502:physiology* / Q000528:radiation effects / Q000601:surgery*
MRgHIFU; dynamic HIFU-beam steering; mobile organ; motion correction; temperature mapping