Post implant dosimetry is an essential part of quality assurance after permanent seed prostate brachytherapy. CT imaging is the standard of assessment but due to contouring uncertainties, MR-CT fusion is preferred. This is not always available due to financial restrictions. This study explores the possibility of post implant US-CT fusion to improve contouring accuracy and potentially replace the use of MR-CT fusion.

25 participants undergoing permanent seed prostate brachytherapy will be approached to undergo collection of prostate US images at the completion of their procedure. This will add approximately 5 minutes to the duration of their brachytherapy procedure. The US study will not entail any discomfort or risk to participants as they are still under anesthesia for the implant procedure. The institution standard of care for quality assurance will be complied with, obtaining a CT and MRI of the prostate at 30 days after the procedure. These will be co-registered and analyzed in the normal fashion. In addition, the post implant US images will also be co-registered with the CT and the resulting dosimetric parameters compared.

Inclusion Criteria:

• localized prostate cancer suitable for permanent seed implant brachytherapy as either monotherapy or as a boost

Exclusion Criteria:

• Unable to undergo MRI

Consecutive patients undergoing prostate brachytherapy for localized prostate cancer.