Volumetric interpolated contrast-enhanced MRA for the diagnosis of pulmonary embolism in an ex vivo system.
OBJECTIVE
To implement a three-dimensional gradient-recalled echo (GRE) volumetric interpolated breath-hold examination (VIBE) sequence for pulmonary contrast-enhanced MRA (CE-MRA) in an experimental setup.


METHODS
Eight porcine lungs were intubated, inflated inside a chest phantom, and examined at 1.5 T during slow perfusion (2-300 mL/minute). Three-dimensional-MRA was performed with and without contrast agent using three-dimensional-GRE (VIBE) with TR/TE = 4.5/1.9 msec, TA = 23 seconds, FOV = 390 mm, FA = 12 degrees /30 degrees, as well as a standard three-dimensional-GRE sequence and T2 fast spin-echo (FSE) sequences. Four of the eight lungs were embolized with autologous blood clots. By consensus readings, two observers evaluated the detectability of peripheral vessels, signal intensity over vessels and lung, and visualization of emboli. Digital subtraction angiograms served as a control to document vessel patency.


RESULTS
Prior to contrast administration, three-dimensional-VIBE/12 degrees yielded the best results for lung parenchyma signal and visualization of small vessels (third-order, P < 0.01); however, no emboli were detected (due to lack of contrast). After administration of contrast agent, three-dimensional-GRE (VIBE) at FA = 30 degrees provided significantly better results (fifth-order branches, documentation of subsegmental occlusions [fourth order], P < 0.01). T2-FSE images documented water uptake into the lungs. Digitally subtracted angiography (DSA) confirmed the patency of seventh-order branches.


CONCLUSIONS
This ex vivo study confirms the potential advantages of using a dual MR investigation for pulmonary embolism, combining three-dimensional-GRE (VIBE) at FA = 12 degrees to image lung parenchyma and at FA = 30 degrees for CE-MRA..
Biederer
Jürgen
J
Department of Diagnostic Radiology, University Hospital Kiel, Kiel, Germany. juergen.biederer@rad.uni-kiel.de
Liess
Carsten
C
Charalambous
Nikolas
N
Heller
Martin
M
D015901:Angiography, Digital Subtraction; D000818:Animals; D003287:Contrast Media; D019786:Gadolinium DTPA; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D066298:In Vitro Techniques; D018810:Magnetic Resonance Angiography; D019047:Phantoms, Imaging; D011651:Pulmonary Artery / Q000473:pathology; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000000981:diagnostic imaging; D013552:Swine
D003287:Contrast Media; D019786:Gadolinium DTPA