In vivo reproducibility of robotic probe placement for an integrated US-CT image-guided radiation therapy system

Muyinatu A.Lediju Bell, H. Tutkun Sen, Iulian Iordachita, Peter Kazanzides, John Wong

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

Abstract

Radiation therapy is used to treat cancer by delivering high-dose radiation to a pre-defined target volume. Ultrasound (US) has the potential to provide real-time, image-guidance of radiation therapy to identify when a target moves outside of the treatment volume (e.g. due to breathing), but the associated probe-induced tissue deformation causes local anatomical deviations from the treatment plan. If the US probe is placed to achieve similar tissue deformations in the CT images required for treatment planning, its presence causes streak artifacts that will interfere with treatment planning calculations. To overcome these challenges, we propose robot-assisted placement of a real ultrasound probe, followed by probe removal and replacement with a geometrically-identical, CT-compatible model probe. This work is the first to investigate in vivo deformation reproducibility with the proposed approach. A dog's prostate, liver, and pancreas were each implanted with three 2.38-mm spherical metallic markers, and the US probe was placed to visualize the implanted markers in each organ. The real and model probes were automatically removed and returned to the same position (i.e. position control), and CT images were acquired with each probe placement. The model probe was also removed and returned with the same normal force measured with the real US probe (i.e. force control). Marker positions in CT images were analyzed to determine reproducibility, and a corollary reproducibility study was performed on ex vivo tissue. In vivo results indicate that tissue deformations with the real probe were repeatable under position control for the prostate, liver, and pancreas, with median 3D reproducibility of 0.3 mm, 0.3 mm, and 1.6 mm, respectively, compared to 0.6 mm for the ex vivo tissue. For the prostate, the mean 3D tissue displacement errors between the real and model probes were 0.2 mm under position control and 0.6 mm under force control, which are both within acceptable radiotherapy treatment margins. The 3D displacement errors between the real and model probes were less acceptable for the liver and pancreas (4.1-6.1 mm), and force control maintained poorer reproducibility than position control.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2014
Subtitle of host publicationImage-Guided Procedures, Robotic Interventions, and Modeling
PublisherSPIE
ISBN (Print)9780819498298
DOIs
StatePublished - Jan 1 2014
EventMedical Imaging 2014: Image-Guided Procedures, Robotic Interventions, and Modeling - San Diego, CA, United States
Duration: Feb 18 2014Feb 20 2014

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume9036
ISSN (Print)1605-7422

Other

OtherMedical Imaging 2014: Image-Guided Procedures, Robotic Interventions, and Modeling
CountryUnited States
CitySan Diego, CA
Period2/18/142/20/14

Keywords

  • deformation
  • intrafraction organ motion
  • liver
  • mock ultrasound probe
  • pancreas
  • prostate
  • radiation therapy
  • repeatability
  • speckle tracking
  • transperineal imaging

ASJC Scopus subject areas

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

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