title: Time-of-flight MR arteriography of below-knee arteries with maximum-intensity-projection reconstruction: is interpretation of the axial source images helpful?
abstract: OBJECTIVE
  We evaluated the extent to which detailed review of axial source images enhances the interpretation of projectional reconstructions of two-dimensional time-of-flight MR arteriograms of the tibial vessels.
  
  
  METHODS
  Thirty-one patients (34 limbs) with limb-threatening ischemia underwent two-dimensional time-of-flight imaging and contrast-enhanced angiography of the below-knee arteries. Maximum-intensity-projection (MIP) reconstructions of the MR arteriograms were independently interpreted by three observers. The studies were then reinterpreted after detailed review of the axial source images. A consensus reading of each study was performed as well. The observers commented on the patency of 816 vascular segments and graded the extent of disease for 272 vessels. Interobserver agreement and correlation with contrast-enhanced angiography were determined.
  
  
  RESULTS
  On average, the addition of axial images altered the observers' interpretation of MR arteriograms in 13% of segments for patency and in 18% of vessels for grading of disease severity. For determining the patency of vascular segments, mean interobserver agreement was 0.79 without and 0.80 with axial image interpretation, and mean agreement with contrast-enhanced angiography improved from 0.69 to 0.72 with the addition of axial images. When evaluating the extent of disease, correlation between observers improved for all combinations of observers with the addition of axial images, and correlation with contrast-enhanced angiography improved for two of three observers. Based on the consensus interpretation of the MR arteriograms, review of axial images was found to improve agreement with contrast-enhanced angiography in 34 vascular segments. In addition, axial image review correctly altered the number of stenoses identified in 12 vessels. When consensus interpretation identified a vessel as patent without significant stenosis on the MIP images, the MIP-based interpretation was found to be correct in all cases.
  
  
  CONCLUSIONS
  Review of axial source images provides limited benefit to interpretation of MR arteriograms of the distal lower extremity in patients with peripheral vascular disease. Although selective review of axial source images may be appropriate, axial images can improve interpretation when MIP images are complicated by the presence of patient motion, difficult anatomy, or artifacts. Axial image review may also be appropriate when a significant stenosis is identified on the MIP images.
authors.affiliation: Department of Radiology/PSRD, Wilford Hall Medical Center, Lackland Air Force Base, TX 78236, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Leyendecker
authors.forename: S P
authors.initials: SP
authors.lastname: Johnson
authors.forename: D C
authors.initials: DC
authors.lastname: Diffin
authors.forename: K
authors.initials: K
authors.lastname: Elsass
authors.forename: S L
authors.initials: SL
authors.lastname: Bifano
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography; D003287:Contrast Media; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007511:Ischemia / Q000175:diagnosis / Q000000981:diagnostic imaging; D007866:Leg / Q000098:blood supply*; D018810:Magnetic Resonance Angiography; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D014654:Vascular Patency
chemical_list: D003287:Contrast Media