Oral and Poster Presentation – Clinical Abstracts Archive

UK & Ireland Prostate Brachytherapy Conference 2017

Abstract number 6

Can MRI based pre-planning replace ultrasound for permanent prostate brachytherapy treatment planning? – A feasibility study

Yoosuf ABM*; McGrath C*; Workman G*; Napier E*; Mitchell DM*
*Belfast City Hospital

AIMS/INTRODUCTION: The objective of this study is to assess the feasibility, beneﬁ ts and effectiveness of staging MRI based pre-planning in permanent prostate brachytherapy and to compare the dosimetric parameters of MRI based and US based pre-planning.

MATERIALS/METHODS: In this retrospective study the planning US images of ten men treated with permanent prostate implant were re-planned using their staging MRI datasets, primarily axial T2 weighted images. All images were anonymized and the structures were contoured by an experienced Radiation Oncologist and independently reviewed by a MRI Radiologist. Contours were compared in terms of volume and dimensions (height, width and length). Treatment plans for MR images were created independently and the dosimetric parameters were compared against US plans.

RESULTS: The mean US/MRI prostate volume ratio was 1.10 ± 0.12 (p = 0.05). The mean US based prostate volume was over-estimated (3.17 cc in mean volume) in comparison to MRI based volume. The width, height and length ratios (US/MRI) for the prostate were 1.06 ± 0.06 (p = 0.01), 0.99 ± 0.08 (p = 0.54) and 1.08 ± 0.15 (p = 0.14) respectively. All dosimetric constraints and objectives could be achieved with MRI pre-planning and were comparable to US based pre-planning. The mean dose to Urethra D10% and total number of needles were reduced signiﬁcantly (p < 0.02) with MRI plans.

CONCLUSION: Staging MRI is comparable to US imaging for pre-implant planning and dosimetric constraints. Signiﬁ cant differences were noticed in the contouring of prostate width between the image sets which could potentially be due to prostate deformation by the US probe. From the results, MRI based pre-planning was found to be a useful modality as it could potentially replace the US volume study visit thereby reducing the staging to treatment timeframe. Further, MRI/CT fused image sets could potentially be used for accurate post-implant dosimetry.