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A method for MRI guidance of intercostal high intensity focused ultrasound ablation in the liver
Author(s) -
Quesson Bruno,
Merle Mathilde,
Köhler Max O.,
Mougenot Charles,
Roujol Sebastien,
de Senneville Baudouin Denis,
Moonen Chrit T.
Publication year - 2010
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3413996
Subject(s) - rib cage , high intensity focused ultrasound , transducer , materials science , ablation , biomedical engineering , ultrasound , intercostal muscle , radiology , medicine , acoustics , anatomy , physics , respiratory system
Purpose High intensity focused ultrasound (HIFU) is a promising method for the noninvasive treatment of liver tumors. However, the presence of ribs in the HIFU beam path remains problematic since it may lead to adverse effects (skin burns) by absorption and reflection of the incident beam at or near the bone surface. This article presents a method based on magnetic resonance (MR) imaging for identification of the ribs in the HIFU beam, and for selection of the transducer elements to deactivate. Methods The ribs are visualized on anatomical images acquired prior to heating and manually segmented. The resulting regions of interest surrounding the ribs are projected onto the transducer surface by ray tracing from the focal point. The transducer elements in the “shadow” of the ribs are then deactivated. The method was validated ex vivo and in vivo in pig liver during breathing under multislice real‐time MR thermometry, using the proton resonance frequency shift method. Results Ex vivo and in vivo temperature data showed that the temperature increase near the ribs was substantial when HIFU sonications were performed with all elements active, whereas the temperature was reduced with deactivation of the transducer elements located in front of the ribs. The temperature at the focal point was similar with and without deactivation of the transducer elements, indicative of no loss of heat efficiency with the proposed technique. Conclusions This method is simple, rapid, and reliable, and enables intercostal HIFU ablation while sparing ribs and their surrounding tissues.