Prostate Brachytherapy UK & Ireland 11-12 June 2026

One Minute Poster Pitches Archive

UK & Ireland Prostate Brachytherapy Conference 2024

Abstract number 10 

MRI registration with the Transrectal ultrasound in LDR Prostate Brachytherapy

Prabakar Sukumar, Helen Winter
Oxford University Hospitals 

Purpose: The standard MR imaging in prostate cancer provides the staging and prognostic information. Here in Oxford, we utilise diagnostic MR to estimate the number of seeds required by preplanning. To aid contouring during the implant procedure we need to register the MR with the Transrectal ultrasound (TRUS). In this paper, we studied three MR-US registration methods using the Variseed treatment planning system: (1) Manual registration without reformat (MR); (2) reformatted manual registration (MRWR); (3) Reformatted template registration (TR). 

Methods: Eighteen prostate cancer patients who had diagnostic MR images available were retrospectively included in this study. Prostate volumes were contoured on the T2 axial MR images by the oncologists. MR images were reformatted using the Varian Variseed 9.0.1 Reformat option. The images were rotated along the rectal axis and resliced to a thickness of 5 mm. The template grid was aligned symmetrically with the bottom grid matched with the posterior prostate, and the base of the prostate was defined. MR images with reformat (MRWR) and without reformat (MR) were manually registered with the TRUS images. Another set of MR images with reformat was imported based on the template registration (TR). The difference in volume, Dice coefficient, and centroid shift between the TRUS prostate volume and the MR image volume were calculated. 

Results: The Dice coefficients of the three registration methods (MR, MRWR and TR) were 0.83±0.05, 0.84±0.03 and 0.72±0.11, respectively. The centroid shifts between the TRUS and MR contours were 0.24±0.16 mm, 0.22±0.09 mm and 0.65±0.34 mm, respectively. The average volume differences were 2.5±3.0 cc, -0.21±5.6 cc and 2.24±5.4 cc. The volume change appears to be significant with MR and TR. 

Conclusion: Reformatted manually registered (MRWR) images have higher Dice values with smaller deviations and lower centroid shifts than the other two registration methods. Template registration (TR) needs to be investigated to identify the reformatting process that can be utilized in the planning process. 

References: 

  1. Thomas J. Pugh and Sajal S. Pokharel, Magnetic resonance imaging in prostate brachytherapy: Evidence, clinical end points to data, and direction forward, Brachytherapy 16(4) pp 659-664.
  2. Report No. 132 – Use of image registration and fusion algorithms and techniques in radiotherapy: Report of the AAPM Radiation Therapy Committee Task Group No. 132 (2017)
  3. Stish BJ, Davis BJ, Mynderse LA, McLaren RH, Deufel CL, Choo R. Low dose rate prostate brachytherapy. Transl Androl Urol. 2018 Jun;7(3):341-356.