title: Focal ablation of prostate cancer: four roles for magnetic resonance imaging guidance.
abstract: BACKGROUND
  There is currently a great deal of interest in the possible use of focal therapies for prostate cancer, since such treatments offer the prospect for control or cure of the primary disease with minimal side effects. Many forms of thermal therapy have been proposed for focal ablation of prostate cancer, including laser, high intensity ultrasound and cryotherapy. This review will demonstrate the important roles that magnetic resonance imaging (MRI) guidance can offer to such focal ablation, focusing on the use of high intensity ultrasonic applicators as an example of one promising technique.
  
  
  METHODS
  Transurethral and interstitial high intensity ultrasonic applicators, designed specifically for ablation of prostate tissue were tested extensively in vivo in a canine model. The roles of MRI in positioning the devices, monitoring prostate ablation, and depicting ablated tissue were assessed using appropriate MRI sequences.
  
  
  RESULTS
  MRI guidance provides a very effective tool for the positioning of ablative devices in the prostate, and thermal monitoring successfully predicted ablation of prostate tissue when a threshold of 52 ºC was achieved. Contrast enhanced MRI accurately depicted the distribution of ablated prostate tissue, which is resorbed at 30 days.
  
  
  CONCLUSIONS
  Guidance of thermal therapies for focal ablation of prostate cancer will likely prove critically dependent on MRI functioning in four separate roles. Our studies indicate that in three roles: device positioning; thermal monitoring of prostate ablation; and depiction of ablated prostate tissue, MR techniques are highly accurate and likely to be of great benefit in focal prostate cancer ablation. A fourth critical role, identification of cancer within the gland for targeting of thermal therapy, is more problematic at present, but will likely become practical with further technological advances.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, Stanford, California 94305, USA.
authors.forename: Graham
authors.initials: G
authors.lastname: Sommer
authors.forename: Donna
authors.initials: D
authors.lastname: Bouley
authors.forename: Harcharan
authors.initials: H
authors.lastname: Gill
authors.forename: Bruce
authors.initials: B
authors.lastname: Daniel
authors.forename: Kim Butts
authors.initials: KB
authors.lastname: Pauly
authors.forename: Chris
authors.initials: C
authors.lastname: Diederich
mesh_terms: D055011:Ablation Techniques / Q000379:methods*; D000818:Animals; D017679:Cryotherapy; D004195:Disease Models, Animal; D004285:Dogs; D006801:Humans; D053685:Laser Therapy; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000601:surgery*; D014464:Ultrasonic Therapy