Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy of the prostate: a preclinical study with radiological and pathological correlation using customised MRI-based moulds

Authors


Correspondence: Peter A. Pinto, Urologic Oncology Branch, National Cancer Institute, 10 Center Drive MSC 1210, Building 10, CRC, Room 2W-5940, Bethesda, MA 20892-1210, USA.

e-mail: pintop@mail.nih.gov

Abstract

Objective

  • To characterise the feasibility and safety of a novel transurethral ultrasound (US)-therapy device combined with real-time multi-plane magnetic resonance imaging (MRI)-based temperature monitoring and temperature feedback control, to enable spatiotemporally precise regional ablation of simulated prostate gland lesions in a preclinical canine model.
  • To correlate ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology.

Materials and Methods

  • Three dogs were treated with three targeted ablations each, using a prototype MRI-guided transurethral US-therapy system (Philips Healthcare, Vantaa, Finland).
  • MRI provided images for treatment planning, guidance, real-time multi-planar thermometry, as well as post-treatment evaluation of efficacy.
  • After treatment, specimens underwent histopathological analysis to determine the extent of necrosis and cell viability.
  • Statistical analyses (Pearson's correlation, Student's t-test) were used to evaluate the correlation between ablation volumes measured with intra-procedural cumulative thermal damage estimates, post-procedural MRI, and histopathology.

Results

  • MRI combined with a transurethral US-therapy device enabled multi-planar temperature monitoring at the target as well as in surrounding tissues, allowing for safe, targeted, and controlled ablations of prescribed lesions.
  • Ablated volumes measured by cumulative thermal dose positively correlated with volumes determined by histopathological analysis (r2 0.83, P < 0.001).
  • Post-procedural contrast-enhanced and diffusion-weighted MRI showed a positive correlation with non-viable areas on histopathological analysis (r2 0.89, P < 0.001, and r2 0.91, P = 0.003, respectively).
  • Additionally, there was a positive correlation between ablated volumes according to cumulative thermal dose and volumes identified on post-procedural contrast-enhanced MRI (r2 0.77, P < 0.01).
  • There was no difference in mean ablation volumes assessed with the various analysis methods (P > 0.05, Student's t-test).

Conclusions

  • MRI-guided transurethral US therapy enabled safe and targeted ablations of prescribed lesions in a preclinical canine prostate model.
  • Ablation volumes were reliably predicted by intra- and post-procedural imaging.
  • Clinical studies are needed to confirm the feasibility, safety, oncological control, and functional outcomes of this therapy in patients in whom focal therapy is indicated.

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