title: Evaluating the utility of intraprocedural 3D TRUS image information in guiding registration for displacement compensation during prostate biopsy.
abstract: OBJECTIVE
  In targeted 3D transrectal ultrasound (TRUS)-guided biopsy, patient and prostate movement during the procedure can cause target misalignments that hinder accurate sampling of preplanned suspicious tissue locations. Multiple solutions have been proposed for displacement compensation via registration of intraprocedural TRUS images to a baseline 3D TRUS image acquired at the beginning of the biopsy procedure. While 2D TRUS images are widely used for intraprocedural guidance, some solutions utilize richer intraprocedural images such as bi- or multiplanar TRUS or 3D TRUS, acquired by specialized probes. In this work, the impact of such richer intraprocedural imaging on displacement compensation accuracy was measured to evaluate the tradeoff between cost and complexity of intraprocedural imaging versus improved displacement compensation.
  
  
  METHODS
  Baseline and intraprocedural 3D TRUS images were acquired from 29 patients at standard sextant-template biopsy locations. Planes extracted from 3D TRUS images acquired at sextant positions were used to simulate 2D and 3D intraprocedural information available in different potential clinically relevant scenarios for co-registration with the baseline 3D TRUS image. In practice, intraprocedural 3D information can be acquired either via the use of specialized ultrasound probes (e.g., multiplanar or 3D probes) or via axial rotation of a tracked 2D TRUS probe. Registration accuracy was evaluated by calculating the target registration error (TRE) using manually identified homologous intrinsic fiducial markers (microcalcifications). The TRE was analyzed separately at the base, mid-gland and apex regions of the prostate.
  
  
  RESULTS
  The results indicate that TRE improved gradually as the number of intraprocedural imaging planes used in registration was increased, implying that 3D TRUS information assisted the registration algorithm to robustly converge to more accurate solutions. The acquisition of a partial volume up to the angle of rotation supported more accurate displacement compensation than acquiring biplane configurations. Additional intraprocedural 3D TRUS image information was more beneficial to registration accuracy in the base and apex regions as compared with the mid-gland region.
  
  
  CONCLUSIONS
  While the majority of the registrations using 2D TRUS images provided a clinically desired level of accuracy, intraprocedural 3D imaging helped improve the overall registration accuracy and robustness, especially in the base and apex regions of the prostate. These results are helpful for devising image-based registration methods for displacement compensation when designing 3D TRUS-guided biopsy systems.
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario N6A 5B7, Canada and Biomedical Engineering Graduate Program, The University of Western Ontario, London, Ontario N6A 5B9, Canada.
authors.forename: Tharindu
authors.initials: T
authors.lastname: De Silva
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario N6A 5B7, Canada and The Department of Medical Imaging, The University of Western Ontario, London, Ontario N6A 5W9, Canada.
authors.forename: Derek W
authors.initials: DW
authors.lastname: Cool
authors.affiliation: The Department of Medical Imaging, The University of Western Ontario, London, Ontario N6A 5W9, Canada.
authors.forename: Cesare
authors.initials: C
authors.lastname: Romagnoli
authors.affiliation: Imaging Research Laboratories, Robarts Research Institute, The University of Western Ontario, London, Ontario N6A 5B7, Canada; The Department of Oncology, The University of Western Ontario, London, Ontario N6A 4L6, Canada; and Biomedical Engineering Graduate Program, The University of Western Ontario, London, Ontario N6A 5B9, Canada.
authors.forename: Aaron
authors.initials: A
authors.lastname: Fenster
authors.affiliation: The Department of Medical Biophysics, The University of Western Ontario, London, Ontario N6A 5C1, Canada; Biomedical Engineering Graduate Program, The University of Western Ontario, London, Ontario N6A 5B9, Canada; and The Department of Oncology, The University of Western Ontario, London, Ontario N6A 4L6, Canada.
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Ward
mesh_terms: D000465:Algorithms; D003198:Computer Simulation; D057918:Fiducial Markers; D006801:Humans; D061705:Image-Guided Biopsy / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009038:Motion; D011467:Prostate / Q000000981:diagnostic imaging* / Q000601:surgery*; D018084:Ultrasonography, Interventional / Q000379:methods*