title: Unenhanced MDCT in suspected urolithiasis: improved stone detection and density measurements using coronal maximum-intensity-projection images.
abstract: OBJECTIVE
  The purpose of this study was to determine whether coronal maximum-intensity-projection (MIP) reformations improve urinary tract stone detection and density measurements compared with routine axial and coronal images.
  
  
  METHODS
  Forty-five consecutive patients who underwent MDCT for suspected urolithiasis were included. Two radiologists independently determined the number of stones on 5-, 3-, and 1.25-mm axial, 5- and 3-mm coronal, and 5-mm coronal MIP images. The reference standard was obtained by consensus review using all six datasets. Stone density was determined for all calculi 4 mm or larger on all datasets.
  
  
  RESULTS
  There were a total of 115 stones. Reader 1 identified 111 (96.5%), 112 (97.4%), 97 (84.3%), 102 (88.7%), 99 (86.1%), and 85 (73.9%) stones and reader 2 identified 105 (91.3%), 102 (88.7%), 85 (73.9%), 89 (77.4%), 89 (77.4%), and 76 (66.1%) stones on the MIP, 1.25-mm axial, 3-mm axial, 3-mm coronal, 5-mm coronal, and 5-mm axial images, respectively. Both readers identified more stones on the MIP images than on the 3- or 5-mm axial or coronal images (p < 0.0001). The mean difference in stone attenuation compared with the thin axial images was significantly less for the MIP images (44.6 HU) compared with 3-mm axial (235 HU), 3-mm coronal (309 HU), and 5-mm coronal (329.6 HU) or axial images (347.8 HU) (p < 0.0001).
  
  
  CONCLUSIONS
  Coronal MIP reformations allow more accurate identification and density measurements of urinary tract stones compared with routine axial and coronal reformations.
authors.affiliation: 1 Department of Radiology, University of California, Davis Medical Center, 4860 Y St, Ste 3100, Sacramento, CA 95817.
authors.forename: Michael T
authors.initials: MT
authors.lastname: Corwin
authors.forename: Margaret
authors.initials: M
authors.lastname: Hsu
authors.forename: John P
authors.initials: JP
authors.lastname: McGahan
authors.forename: Machelle
authors.initials: M
authors.lastname: Wilson
authors.forename: Ramit
authors.initials: R
authors.lastname: Lamba
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D061330:Multidetector Computed Tomography / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D012189:Retrospective Studies; D052878:Urolithiasis / Q000000981:diagnostic imaging*