In vivo validation of spatio-temporal liver motion prediction from motion tracked on MR thermometry images

C. Tanner (Lead / Corresponding author), Y. Zur, K. French, G. Samei, J. Strehlow, G. Sat, H. McLeod, G. Houston, S. Kozerke, G. Székely, A. Melzer, T. Preusser

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Purpose: Magnetic resonance-guided focused ultrasound (MRgFUS) of the liver during free-breathing requires spatio-temporal prediction of the liver motion from partial motion observations. The study purpose is to evaluate the prediction accuracy for a realistic MRgFUS therapy scenario, namely for human in vivo data, tracking based on MR images routinely acquired during MRgFUS and in vivo deformations caused by the FUS probe.

Methods: In vivo validation of the motion model was based on a 3D breath-hold image and an interleaved acquisition of two MR slices. Prediction accuracy was determined with respect to manually annotated landmarks. A statistical population liver motion model was used for predicting the liver motion for not tracked regions. This model was individualized by mapping it to end-exhale 3D breath-hold images. Spatial correspondence between tracking and model positions was established by affine 3D-to-2D image registration. For spatio-temporal prediction, MR tracking results were temporally extrapolated. 

Results: Performance was evaluated for 10 volunteers, of which 5 had a dummy FUS probe put on their abdomen. MR tracking had a mean (95 %) accuracy of 1.1 (2.4) mm. The motion of the liver on the evaluation MR slice was spatio-temporally predicted with an accuracy of 1.9 (4.4) mm for a latency of 216 ms. A simple translation model performed similarly (2.1 (4.8) mm) as the two MR slices were relatively close (mean 38 mm). Temporal prediction was important (10 % error reduction), while registration effects could only partially be assessed and showed no benefits. On average, motion magnitude, motion amplitude and breathing frequency increased by 24, 16 and 8 %, respectively, for the cases with FUS probe placement. This motion increase could be reduced by the spatio-temporal prediction.

Conclusion: The study shows that tracking liver vessels on MR images, which are also used for MR thermometry, is a viable approach.

Original languageEnglish
Pages (from-to)1143-1152
Number of pages10
JournalInternational Journal of Computer Assisted Radiology and Surgery
Volume11
Issue number6
Early online date12 Apr 2016
DOIs
Publication statusPublished - Jun 2016

Keywords

  • Focused ultrasound
  • Motion prediction
  • Respiration
  • Tracking

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