Gadolinium-enhanced off-resonance contrast angiography.
We describe a novel physical basis and methodology for gadolinium (Gd)-enhanced MRA, which we call "off-resonance contrast angiography" (ORCA). Unlike standard contrast-enhanced (CE) MR angiography (MRA), ORCA contrast depends not on T(1) but on Gd-induced shifts in intravascular resonance frequency due to the bulk magnetic susceptibility (BMS) effects of Gd. The method was tested at 3 Tesla in phantoms with a range of dilutions of Gd-DTPA and ultrasmall iron oxide contrast agent (CA). With the use of ORCA, complete background suppression was obtained without image subtraction. As a result, catheters filled with various Gd dilutions proved to be highly conspicuous in ORCA projection images. This feature may make ORCA particularly attractive for passive catheter tracking during MR-guided endovascular procedures. Gd-induced intravascular frequency shifts were measured in human subjects and found to be in the expected range. ORCA was used to create angiograms of forearm veins that were comparable in quality to standard CE-MRA. In addition, ORCA images of the extracranial carotid bifurcation were successfully acquired during intravenous contrast administration. However, significant technical restrictions also exist, including a dependence on vessel orientation with respect to B(0), and sensitivity to static field inhomogeneities. Further study is needed to determine the practicality and potential clinical utility of this method.
Edelman
Robert R
RR
Department of Radiology, Evanston Northwestern Healthcare and Northwestern University School of Medicine, Evanston, Illinois 60201, USA. redelman@enh.org
Storey
Pippa
P
Dunkle
Eugene
E
Li
Wei
W
Carrillo
Andres
A
Vu
Anthony
A
Carroll
Timothy J
TJ
D000328:Adult; D002342:Carotid Artery, External / Q000033:anatomy & histology; D003287:Contrast Media / Q000008:administration & dosage*; D003911:Dextrans; D005260:Female; D052203:Ferrosoferric Oxide; D005542:Forearm / Q000098:blood supply*; D019786:Gadolinium DTPA / Q000008:administration & dosage*; D006801:Humans; D007501:Iron / Q000008:administration & dosage; D018810:Magnetic Resonance Angiography / Q000379:methods*; D058185:Magnetite Nanoparticles; D008297:Male; D010087:Oxides / Q000008:administration & dosage; D019047:Phantoms, Imaging
D003287:Contrast Media; D003911:Dextrans; D058185:Magnetite Nanoparticles; D010087:Oxides; D007501:Iron; C065507:ferumoxides; D019786:Gadolinium DTPA; D052203:Ferrosoferric Oxide