MRI-Guided Prostate Motion Tracking using Multislice-to-Volume Registration
Abstract
MRI-guided prostate needle biopsy requires compensation for organ motion between
target planning and needle placement. Two questions are studied and answered in this
work: is rigid registration sufficient in tracking the targets with a maximum error of
3 mm (smaller than average prostate tumor size) and how many intra-operative slices
are required to obtain this accuracy? We developed rigid and deformable multislice-
to-volume registration algorithms for tracking the biopsy targets within the prostate.
Three orthogonal plus additional transverse intra-operative slices were acquired in
the approximate center of the prostate and registered with a high-resolution target
planning volume. Simulated intra-operative data, phantom data, and MRI-guided
robotic prostate biopsy data were used to assess tracking accuracy. Registration tests
on simulated intra-operative data with 3, 4, and 5 slices were performed to evaluate
the effect on registration error and time. Results: Using three orthogonal slices pro-
vides sufficient accuracy. Convergence test results on phantom images demonstrated
100% success rate for initial misalignment of 5mm. Average registration errors for
the patient data were 2.55mm and 2.05mm for the rigid and deformable algorithms,
respectively. The algorithm was able to capture rigid biopsy target displacements
of maximum 8mm and non-rigid displacements of maximum 1.5mm. Rigid tracking
appears to be promising. Deformable registration does not seem warranted.