Towards intra-operative monitoring of ablation using tracked 3D ultrasound elastography and internal palpation

Pezhman Foroughi, Jessica Burgner, Michael A. Choti, Robert J. Webster, Gregory D. Hager, Emad M. Boctor

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Scopus citations


B-mode ultrasound is widely used in liver ablation. However, the necrosis zone is typically not visible under b-mode ultrasound, since ablation does not necessarily change the acoustic properties of the tissue. In contrast, the change in tissue stiffness makes elastography ideal for monitoring ablation. Tissue palpation for elastography is typically applied at the imaging probe, by indenting it slightly into the tissue surface. However, in this paper we propose an alternate approach, where palpation is applied by a surgical instrument located inside the tissue. In our approach, the ablation needle is placed inside a steerable device called an active cannula and inserted into the tissue. A controlled motion is applied to the center of the ablation zone via the active cannula. Since the type and direction of motion is known, displacement can then be computed from two frames with the desired motion. The elastography results show the ablated region around the needle. While internal palpation provides excellent local contrast, freehand palpation from outside of the tissue via the transducer can provide a more global view of the region of the interest. For this purpose, we used a tracked 3D transducer to generate volumetric elastography images covering the ablated region. The tracking information is employed to improve the elastography results by selecting volume pairs suitable for elastography. This is an extension of our 2D frame selection technique which can cope with uncertainties associated with intra-operative elastography. In our experiments with phantom and ex-vivo tissue, we were able to generate high-quality images depicting the boundaries of the hard lesions.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2012
Subtitle of host publicationUltrasonic Imaging, Tomography, and Therapy
StatePublished - 2012
EventMedical Imaging 2012: Ultrasonic Imaging, Tomography, and Therapy - San Diego, CA, United States
Duration: Feb 5 2012Feb 6 2012

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


OtherMedical Imaging 2012: Ultrasonic Imaging, Tomography, and Therapy
Country/TerritoryUnited States
CitySan Diego, CA


  • Ablation
  • Active cannula
  • Elastography
  • Frame selection
  • Intra-operative imaging
  • Monitoring
  • Strain
  • Tracking

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging
  • Biomaterials


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