title: Magnetic resonance imaging characteristics of renal tumors after radiofrequency ablation.
abstract: OBJECTIVE
  The interpretation of radiographic findings in renal tumors treated with minimally invasive modalities, such as radiofrequency ablation (RFA), is critical for assessing treatment adequacy. Magnetic resonance imaging (MRI) is commonly used for patients with renal insufficiency or contrast allergy. Because the MRI experience with renal RFA is limited, we reviewed our experience and report the unique MRI characteristics of RFA-treated renal tumors.
  
  
  METHODS
  A single-institution database of renal RFA was reviewed to identify patients followed up with MRI. A radiologist and urologist retrospectively reviewed all MRI scans to identify the characteristic lesion findings after RFA.
  
  
  RESULTS
  Eleven patients (12 tumors) treated by RFA were followed up with MRI examinations. The mean follow-up was 10 months. The mean tumor size at ablation was 2.4 cm, with minimal reduction over time. Ablated lesions were characterized by high signal intensity on T1-weighted images, low signal intensity on T2-weighted images, and an absence of contrast enhancement. Of the patients treated by percutaneous RFA, 71% developed a characteristic peritumor halo, seen as a rim of low signal intensity on T1-weighted and T2-weighted images, surrounding a zone of perinephric fat just external to the ablated area. Two lesions demonstrated enhancement on the initial postablation MRI scan, indicating incomplete ablation.
  
  
  CONCLUSIONS
  The MRI characteristics of successfully ablated renal tumors include the absence of enhancement, minimal size reduction over time, and high and low signal intensity on T1-weighted and T2-weighted imaging, respectively. Knowledge of these findings can aid radiologists and urologists in correctly assessing the success of RFA for kidney lesions.
authors.affiliation: Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Svatek
authors.forename: Robert
authors.initials: R
authors.lastname: Sims
authors.forename: J Kyle
authors.initials: JK
authors.lastname: Anderson
authors.forename: Khaled
authors.initials: K
authors.lastname: Abdel-Aziz
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Cadeddu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017115:Catheter Ablation; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D012189:Retrospective Studies