Noninvasive assessment of blood flow based on magnetic resonance global coherent free precession.
BACKGROUND
Magnetic resonance global coherent free precession (GCFP) is a new technique that produces cine projection angiograms directly analogous to those of x-ray angiography noninvasively and without a contrast agent. In this study, we compared GCFP blood flow with "gold standards" to determine the accuracy of noninvasive GCFP blood flow measurements.


RESULTS
The relationship between GCFP blood flow and true blood flow defined by invasive ultrasonic flow probe and by phase contrast velocity encoded MRI (VENC) was studied in anesthetized dogs (n=6). Blood flow was controlled by use of a hydraulic occluder around the left iliac artery. GCFP images were acquired by selectively exciting the abdominal aorta and visualizing temporal blood flow into the iliac arteries. GCFP flow was similar to ultrasonic blood flow at baseline (131.3+/-44.8 versus 114.8+/-34.2 mL/min), during occlusion (10.8+/-5.1 versus 6.5+/-7.2 mL/min), during reactive hyperemia (191.4+/-100.7 versus 260.3+/-138.7 mL/min), during the new resting state (135.5+/-52.4 versus 117.8+/-24.1 mL/min), and during partial occlusion (61.4+/-36.4 versus 49.3+/-13.1 mL/min, P=NS for all). Results comparing GCFP flow with VENC were similar. Statistical analysis revealed that GCFP flow was related to mean blood flow assessed by the flow probe (P<0.0001) and by VENC (P<0.0001). In the control right iliac artery, conversely, GCFP measurements were unaffected throughout all left iliac interventions (P=NS).


CONCLUSIONS
GCFP blood flow is linearly related to true blood flow for a straight, cylindrical blood vessel without branches. Although more complex geometries imply a qualitative rather than a quantitative relationship, the data nevertheless suggest that GCFP may serve as the basis for a new form of noninvasive stress testing.
Klem
Igor
I
Duke Cardiovascular Magnetic Resonance Center, Durham, NC 27710, USA.
Rehwald
Wolfgang G
WG
Heitner
John F
JF
Wagner
Anja
A
Albert
Timothy
T
Parker
Michele A
MA
Chen
Enn-Ling
EL
Kim
Raymond J
RJ
Judd
Robert M
RM
D000818:Animals; D004285:Dogs; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods / Q000639:trends*; D015336:Molecular Probe Techniques; D012039:Regional Blood Flow / Q000502:physiology*