title: Pulmonary Embolism Detection with Three-dimensional Ultrashort Echo Time MR Imaging: Experimental Study in Canines.
abstract: OBJECTIVE
  To demonstrate the feasibility of free-breathing three-dimensional (3D) radial ultrashort echo time (UTE) magnetic resonance (MR) imaging in the simultaneous detection of pulmonary embolism (PE) and high-quality evaluation of lung parenchyma.
  
  
  METHODS
  The institutional animal care committee approved this study. A total of 12 beagles underwent MR imaging and computed tomography (CT) before and after induction of PE with autologous clots. Breath-hold 3D MR angiography and free-breathing 3D radial UTE (1.0-mm isotropic spatial resolution; echo time, 0.08 msec) were performed at 3 T. Two blinded radiologists independently marked and graded all PEs on a four-point scale (1 = low confidence, 4 = absolutely certain) on MR angiographic and UTE images. Image quality of pulmonary arteries and lung parenchyma was scored on a four-point-scale (1 = poor, 4 = excellent). Locations and ratings of emboli were compared with reference standard CT images by using an alternative free-response receiver operating characteristic curve (AFROC) method. Areas under the curve and image quality ratings were compared by using the F test and the Wilcoxon signed-rank test.
  
  
  RESULTS
  A total of 48 emboli were detected with CT. Both readers showed higher sensitivity for PE detection with UTE (83% and 79%) than with MR angiography (75% and 71%). The AFROC area under the curve was higher for UTE than for MR angiography (0.95 vs 0.89), with a significant difference in area under the curve of 0.06 (95% confidence interval: 0.01, 0.11; P = .018). UTE image quality exceeded that of MR angiography for subsegmental arteries (3.5 ± 0.7 vs 2.9 ± 0.5, P = .002) and lung parenchyma (3.8 ± 0.5 vs 2.2 ± 0.2, P < .001). The apparent signal-to-noise ratio in pulmonary arteries and lung parenchyma was significantly higher for UTE than for MR angiography (41.0 ± 5.2 vs 24.5 ± 6.2 [P < .001] and 10.2 ± 1.8 vs 3.5 ± 0.8 [P < .001], respectively). The apparent contrast-to-noise ratio between arteries and PEs was higher for UTE than for MR angiography (20.3 ± 5.2 vs 15.4 ± 6.7, P = .055).
  
  
  CONCLUSIONS
  In a canine model, free-breathing 3D radial UTE performs better than breath-hold 3D MR angiography in the detection of PE and yields better image quality for visualization of small vessels and lung parenchyma. Free-breathing 3D radial UTE for detection of PE is feasible and warrants evaluation in human subjects.
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Peter
authors.initials: P
authors.lastname: Bannas
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Bell
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Johnson
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Mark L
authors.initials: ML
authors.lastname: Schiebler
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: François
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Utaroh
authors.initials: U
authors.lastname: Motosugi
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Daniel
authors.initials: D
authors.lastname: Consigny
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Scott B
authors.initials: SB
authors.lastname: Reeder
authors.affiliation: From the Departments of Radiology (P.B., M.L.S., C.J.F., U.M., D.C., S.B.R., S.K.N.), Medical Physics (L.C.B., K.M.J., S.B.R., S.K.N.), Biomedical Engineering (S.B.R.), Medicine (S.B.R.), Emergency Medicine (S.B.R.), and Pediatrics (S.K.N.), University of Wisconsin-Madison, 600 Highland Ave, Madison, WI 53792-3252.
authors.forename: Scott K
authors.initials: SK
authors.lastname: Nagle
mesh_terms: D000818:Animals; D003287:Contrast Media; D004195:Disease Models, Animal; D004285:Dogs; D005682:Gadolinium; D021621:Imaging, Three-Dimensional; D018810:Magnetic Resonance Angiography / Q000379:methods*; D009942:Organometallic Compounds; D011655:Pulmonary Embolism / Q000175:diagnosis*; D059629:Signal-To-Noise Ratio; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D003287:Contrast Media; D009942:Organometallic Compounds; D005682:Gadolinium; C109932:gadofosveset trisodium