Real time shear waves elastography monitoring of thermal ablation: in vivo evaluation in pig livers.
BACKGROUND
Thermal ablation is a widely used minimally invasive treatment modality for different cancers. However, lack of a real-time imaging system for accurate evaluation of the procedure is one of the reasons of local recurrences. Shear waves elastography (SWE) is a new ultrasound (US) imaging modality to quantify tissue stiffness. The aim of the study was to assess the feasibility and accuracy of US elastography for quantitative monitoring of thermal ablation and to determine the elasticity threshold predictive of coagulation necrosis.


METHODS
A total of 29 in vivo thermal lesions were performed in pig livers with radiofrequency system. SWE and B-mode images were acquired simultaneously. Liver elasticity was quantified by using SWE data and expressed in kilopascal. After the procedure, pathologic analysis of treated tissues was compared with US images. The sensitivity and positive predictive value of the SWE maps of tissue elasticity were calculated and compared with the boundaries of the pale coagulation necrosis areas found at pathology.


RESULTS
The liver mean elasticity values before and after thermal therapy were 6.4 ± 0.3 and 38.1 ± 2.5 kPa, respectively (P < 0.0001). For a threshold of 20 kPa, sensitivity (i.e., the rate of pixels correctly detected as necrosed tissue) was 0.8, and the positive predictive value (i.e., the rate of pixels in the elastographic map >20 kPa that actually developed coagulation necrosis) was 0.83.


CONCLUSIONS
Tissue areas with coagulation necrosis are significantly stiffer than the surrounding tissue. SWE permits the real-time detection of coagulation necrosis produced by radiofrequency and could potentially be used to monitor US-guided thermal ablation.
Laboratoire de recherche en imagerie, INSERM, UMR 970, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, Paris, France; Department of Digestive and General Surgery, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France. Electronic address: a.mariani@hotmail.fr.
A
A
Mariani
Laboratoire de recherche en imagerie, Institut Langevin, Ecole Superieure de Physique et de Chimie, Industrielles de Paris (ESPCI) ParisTech, CNRS UMR 7587, INSERM U979, Paris, France.
W
W
Kwiecinski
Laboratoire de recherche en imagerie, Institut Langevin, Ecole Superieure de Physique et de Chimie, Industrielles de Paris (ESPCI) ParisTech, CNRS UMR 7587, INSERM U979, Paris, France.
M
M
Pernot
Laboratoire de recherche en imagerie, INSERM, UMR 970, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, Paris, France.
D
D
Balvay
Laboratoire de recherche en imagerie, Institut Langevin, Ecole Superieure de Physique et de Chimie, Industrielles de Paris (ESPCI) ParisTech, CNRS UMR 7587, INSERM U979, Paris, France.
M
M
Tanter
Laboratoire de recherche en imagerie, INSERM, UMR 970, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, Paris, France; Department of Radiology, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France.
O
O
Clement
Laboratoire de recherche en imagerie, INSERM, UMR 970, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, Paris, France; Department of Radiology, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France.
C A
CA
Cuenod
Laboratoire de recherche en imagerie, INSERM, UMR 970, Paris Cardiovascular Research Center, Université Paris Descartes, Sorbonne Paris Cité, Paris, France; Department of Digestive and General Surgery, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, Paris, France.
F
F
Zinzindohoue
D055011:Ablation Techniques / Q000009:adverse effects*; D000818:Animals; D003972:Diathermy / Q000009:adverse effects*; D054459:Elasticity Imaging Techniques; D005240:Feasibility Studies; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology / Q000601:surgery; D016343:Monitoring, Intraoperative; D009336:Necrosis; D013552:Swine
Coagulation necrosis; Elastography; Liver; Pigs; Radiofrequency; Shear waves; Thermal ablation