title: An international multicenter comparison of time-SLIP unenhanced MR angiography and contrast-enhanced CT angiography for assessing renal artery stenosis: the renal artery contrast-free trial.
abstract: OBJECTIVE
  The unenhanced MR angiography (MRA) technique time-spatial labeling inversion pulse (time-SLIP) may provide a safe alternative for evaluating the renal arteries for stenosis. This international multicenter trial tested the hypothesis that time-SLIP unenhanced MRA is accurate and robust for assessing the renal arteries for stenosis in comparison with contrast-enhanced CT angiography (CTA).
  
  
  METHODS
  Four centers (United States, Europe, Asia) enrolled 75 patients (average age ± SD, 58 ± 13 years; 41 [55%] men and 34 [45%] women). Each patient underwent abdominal contrast-enhanced CTA and abdominal unenhanced MRA using time-SLIP with balanced steady-state free precession. All images were visually assessed for quality (arterial signal intensity) and for the absence or presence of renal artery stenosis (≤ 50% or > 50% stenosis, respectively). In addition, for arteries with any visible disease, the severity of the stenosis was quantified. Two blinded readers evaluated each study. No arteries were excluded from analysis.
  
  
  RESULTS
  Unenhanced MRA image quality was excellent for 56 of 75 patients (75%) and good for 16 of 75 patients (21%). CTA was used as the reference standard and showed that 23 of 161 renal arteries (14.3%) had stenosis > 50%. Unenhanced MRA correctly classified 17 of the 23 renal arteries with > 50% stenosis and correctly classified 128 of the 138 renal arteries as not having disease (≤ 50% stenosis) to yield a sensitivity of 74%, specificity of 93%, and accuracy of 90% (χ(2) = 0.56; p = 0.45, no statistically significant difference). Of the 16 misclassified arteries, only three had a clinically relevant misclassification (CTA ≥ 70% stenosis and unenhanced MRA ≤ 50% stenosis or unenhanced MRA ≥ 70% stenosis and CTA ≤ 50% stenosis). On average, measured stenotic severity (n = 28 arteries) was similar for unenhanced MRA (64% ± 17%) and CTA (62% ± 16%) (p = 0.51).
  
  
  CONCLUSIONS
  Compared with contrast-enhanced CTA, the unenhanced MRA technique time-SLIP shows promise for assessing the renal arteries for stenosis. The unenhanced MRA technique time-SLIP may provide a safe alternative for evaluating the renal arteries for stenosis.
authors.affiliation: 1 Advanced Diagnostic Imaging Center, Salinas Valley Memorial Healthcare System, 5 Lower Ragsdale Dr, Ste 103, Monterey, CA 93940.
authors.forename: Timothy S E
authors.initials: TS
authors.lastname: Albert
authors.forename: Masaaki
authors.initials: M
authors.lastname: Akahane
authors.forename: Isabelle
authors.initials: I
authors.lastname: Parienty
authors.forename: Nancy
authors.initials: N
authors.lastname: Yellin
authors.forename: Violeta
authors.initials: V
authors.lastname: Catalá
authors.forename: Xavier
authors.initials: X
authors.lastname: Alomar
authors.forename: Antoine
authors.initials: A
authors.lastname: Prot
authors.forename: Nobuo
authors.initials: N
authors.lastname: Tomizawa
authors.forename: Huadan
authors.initials: H
authors.lastname: Xue
authors.forename: Venkata S
authors.initials: VS
authors.lastname: Katabathina
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Lopera
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Jin
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D038622:Internationality; D018810:Magnetic Resonance Angiography / Q000379:methods*; D008875:Middle Aged; D015588:Observer Variation; D012078:Renal Artery Obstruction / Q000175:diagnosis*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method; D014057:Tomography, X-Ray Computed / Q000379:methods*; D055815:Young Adult
chemical_list: D003287:Contrast Media
keywords: CT angiography; multicenter clinical trial; renal artery stenosis; unenhanced MR angiography