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Hand-held Ultrasound Elastography for guiding liver ablations produced using a Toroidal HIFU Transducer. Results of animal experiments

2010; American Institute of Physics; Linguagem: Inglês

10.1063/1.3367187

1935-0465

Jérémy Chenot, David Melodelima, Rémi Souchon, Jean‐Yves Chapelon, Kullervo Hynynen, Jacques Souquet,

Photoacoustic and Ultrasonic Imaging

The use of real‐time elastography for imaging HIFU ablations produced during surgery in porcine liver by a toroidal HIFU transducer was investigated. A conventional sectorial 7.5 MHz real‐time ultrasound imaging probe was used to obtain radiofrequency signals from a modified B‐K ultrasound scanner. Strain images were calculated and displayed at 23 image/sec using a correlation‐based method. Two compression methods were used to produce elastograms: hand‐held compression and hand‐held compression with a plate. Ablations produced in pigs during in vivo treatments were imaged. The quality of the elastograms corresponding to the elastically inhomogeneous liver (normal and ablated tissues) was assessed by computing the contrast‐to‐noise ratio (CNRe) and the signal‐to‐noise ratio (SNRe). In addition, the ablation dimensions measured on sonograms and on elastograms were compared with gross pathology. The contrast observed between sonograms and elastograms was also compared. Sonograms and elastograms allowed observation of ablations with dimensions corresponding well to dimensions measured on gross pathology (r = 0.67 and 0.82 respectively). The average CNRe and SNRe were 3.6±3.1[0.1–14.7] and 1.1±0.3[0.8–2.0] for elastograms. The contrast between ablated and non‐ablated tissue was higher on elastograms (22 dB) when compared with sonograms (2 dB). Hand‐held sonography/elastography is straightforward and allows combining the advantages of both modalities used in a highly complementary manner for the guidance of ablations produced in the liver during surgical HIFU therapy. Compared with sonograms, the two elastography methods shown higher contrast and better estimation of ablation dimensions. Strains generated using hand‐held compression with or without a plate produce satisfactory results. However hand‐held compression may have broader possible applications.