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MRIdian® – MR-guided radiation therapy

Reducing treatment time and improving toxicity in prostate cancer treatment

Approximately one third of patients with prostate cancer are offered external beam radiation therapy, and this proportion increases with age. Conventionally fractionated treatment often requires up to 8 weeks of treatment, delivering small daily fractions such as 1-8-2 Gy/fraction.1 Recent developments in radiation therapy have allowed for larger doses per fraction (hypofractionation), which has been shown to shrink prostate tumors, while protecting surrounding healthy tissue.

MR imaging during dose delivery takes in to account the systematic anatomical variability of prostate swelling as well as random anatomical changes such as inter/intra-fraction bladder and rectal filling and independent variations and deformations of OARs. The adaptive and beam gating capabilities of the MRIdian® offer the possibility of compensating for many of these variables. With MRIdian® , it is possible to:2

  • Compensate for independent movements of the prostate volume
  • Automatically pause the treatment delivery if the prostate position exceeds predefined threshold
  • Avoid the need for specific radio-opaque markers that serve as a surrogate for the prostate position.

Low-grade toxicity

Studies by Bruynzeel et al in 2019 performed a prospective phase 2 study of MR guided RT for localised prostate cancer. The study looked at early gastrointestinal (GI), genitourinary (GU) toxicity and quality-of-life after SABR and MR guided treatment.3

Key results

  • One of the main findings of the study was a very low rate of 5% early grade ≥2 GI toxicity
  • No grade 3 toxicity was observed. GU grade toxicity peaked to 19.8% at the end of MR guided treatment, followed by a return to baseline average score at 3-month follow up
  • Therefore, patients with localised prostate cancer observed a low incidence of early GI and GU toxicity in both clinician and patient reported outcome measurements.

Discover MRIdian®

Watch Dr. Rodney Ellis, National Medical Director of MR-Linac, explain this game-changing technology.


  1. Tetar SU, et al. Phy Imaging Radiat Oncol 2019; 9:69-76.
  2. Tetar SU, et al. Resonance Imaging – guided radiation therapy. Cereus 2018; 10(2).
  3. Bruynzeel A, et al. Int J Radiat Oncol Biol Phys 2019; 105(5):1086-1094.
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