title: Digital subtraction dark-lumen MR colonography: initial experience.
abstract: OBJECTIVE
  To evaluate image subtraction for the detection of colonic pathologies in a dark-lumen MR colonography exam.
  
  
  METHODS
  A total of 20 patients (12 males; 8 females; mean 51.4 years of age) underwent MR colonography after standard cleansing and a rectal water enema on a 1.5-T whole-body MR system. After suppression of peristaltic motion, native and Gd-contrast-enhanced three-dimensional T1-w gradient echo images were acquired in the coronal plane. Two radiologists analyzed the MR data sets in consensus on two separate occasions, with and without the subtracted images for lesion detection, and assessed the value of the subtracted data set on a five-point Likert scale (1=very helpful to 5=very unhelpful). All imaging results were compared with endoscopy.
  
  
  RESULTS
  Without subtracted images, MR-colonography detected a total of five polyps, two inflammatory lesions, and one carcinoma in eight patients, which were all verified by endoscopy. Using subtraction, an additional polyp was found, and readout time was significantly shorter (6:41 vs. 7:39 minutes; P<0.05). In two patients, endoscopy detected a flat adenoma and a polyp (0.4 cm) that were missed in the MR exam. Sensitivity and specificity without subtraction were 0.67/1.0, and 0.76/1.0 with the subtracted images, respectively. Subtraction was assessed as helpful in all exams (mean value 1.8+/-0.5; Likert scale).
  
  
  CONCLUSIONS
  We consider subtraction of native from contrast-enhanced dark-lumen MR colonography data sets as a beneficial supplement to the exam.
authors.affiliation: Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, Essen, Germany.
authors.forename: Waleed
authors.initials: W
authors.lastname: Ajaj
authors.forename: Patrick
authors.initials: P
authors.lastname: Veit
authors.forename: Christiane
authors.initials: C
authors.lastname: Kuehle
authors.forename: Michaela
authors.initials: M
authors.lastname: Joekel
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Lauenstein
authors.forename: Christoph U
authors.initials: CU
authors.lastname: Herborn
mesh_terms: D000328:Adult; D003108:Colonic Diseases / Q000175:diagnosis*; D003287:Contrast Media; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives; D008875:Middle Aged; D009942:Organometallic Compounds; D012680:Sensitivity and Specificity; D013382:Subtraction Technique
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; C064572:gadobenic acid; D008536:Meglumine