title: Visualization of HIFU-induced lesion boundaries by axial-shear strain elastography: a feasibility study.
abstract: In this paper, we report on a study that investigated the feasibility of reliably visualizing high-intensity focused ultrasound (HIFU) lesion boundaries using axial-shear strain elastograms (ASSE). The HIFU-induced lesion cases used in the present work were selected from data acquired in a previous study. The samples consisted of excised canine livers with thermal lesions produced by a magnetic resonance-compatible HIFU system (GE Medical System, Milwaukee, WI, USA) and were cast in a gelatin block for the elastographic experiment. Both single and multiple HIFU-lesion samples were investigated. For each of the single-lesion samples, the lesion boundaries were determined independently from the axial strain elastogram (ASE) and ASSE at various iso-intensity contour thresholds (from -2 dB to -6 dB), and the area of the enclosed lesion was computed. For samples with multiple lesions, the corresponding ASSE was analyzed for identifying any unique axial-shear strain zones of interest. We further performed finite element modeling (FEM) of simple two-inclusion cases to verify whether the in vitro ASSE obtained were reasonable. The results show that the estimation of the lesion area using ASSE is less sensitive to iso-intensity threshold selection, making this method more robust compared with the ASE-based method. For multiple lesion cases, it was shown that ASSE enables high-contrast visualization of a "thin" untreated region in between multiple fully-treated HIFU-lesions. This contrast visualization was also noticed in the FEM predictions. In summary, the results demonstrate that it is feasible to reliably visualize HIFU lesion boundaries using ASSE.
authors.affiliation: The University of Texas Medical School, Department of Diagnostic and Interventional Imaging, Ultrasonics Laboratory, Houston, TX 77030, USA. Arun.K.Thittai@uth.tmc.edu
authors.forename: Arun K
authors.initials: AK
authors.lastname: Thittai
authors.forename: Belfor
authors.initials: B
authors.lastname: Galaz
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ophir
mesh_terms: D000818:Animals; D004285:Dogs; D055119:Elastic Modulus / Q000502:physiology / Q000528:radiation effects; D054459:Elasticity Imaging Techniques / Q000379:methods*; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging* / Q000502:physiology / Q000528:radiation effects*; D013010:Sonication / Q000379:methods*