In vivo real-time intravascular MRI.
OBJECTIVE
The Magnetic resonance imaging (MRI) is an emerging technology for catheter-based imaging and interventions. Real-time MRI is a promising methodfor overcoming catheter and physiologic motion for intravascular imaging.


METHODS
All imaging was performed on a 1.5 T Signa MRI scanner with high-speed gradients. Multiple catheter coils were designed and constructed, including low-profile, stub-matched coils. Coil sensitivity patterns and SNR measurements were compared. Real-time imaging was performed with an interleaved spiral sequence using a dedicated workstation, providing real-time data acquisition, image reconstruction and interactive control and display. Real-time "black-blood" imaging was achieved through incorporation of off-slice saturation pulses. The imaging sequence was tested in a continuous flow phantom and then in vivo in the rabbit aorta using a 2 mm catheter coil.


RESULTS
The real-time intravascular imaging sequence achieved 120-440 micron resolution at up to 16 frames per second. Low-profile stub-tuned catheter coils achieved similar SNR to larger traditional coil designs. In the phantom experiments, addition of real-time black-blood saturation pulses effectively suppressed the flow signal and allowed visualization of the phantom wall. In vivo experiments clearly showed real-time intravascular imaging of the rabbit aortic wall with minimal motion artifacts and effective blood signal suppression.


CONCLUSIONS
Real-time imaging with low-profile coil designs provides significant enhancements to intravascular MRI.
Rivas
Pedro A
PA
Division of Cardiovascular Medicine, Stanford University School of Medicine, CA 94305-5233, USA.
Nayak
Krishna S
KS
Scott
Greig C
GC
McConnell
Michael V
MV
Kerr
Adam B
AB
Nishimura
Dwight G
DG
Pauly
John M
JM
Hu
Bob S
BS
D000818:Animals; D001011:Aorta / Q000473:pathology; D001161:Arteriosclerosis / Q000473:pathology; D016477:Artifacts; D002404:Catheterization / Q000295:instrumentation*; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D019047:Phantoms, Imaging; D011673:Pulsatile Flow; D011817:Rabbits