Blood oxygen level-dependent MRI of tissue oxygenation: relation to endothelium-dependent and endothelium-independent blood flow changes.
OBJECTIVE
The contribution of endothelial function to tissue oxygenation is not well understood. Muscle blood oxygen level-dependent MRI (BOLD MRI) provides data largely dependent on hemoglobin (Hb) oxygenation. We used BOLD MRI to assess endothelium-dependent signal intensity (SI) changes.


RESULTS
We investigated mean BOLD SI changes in the forearm musculature using a gradient-echo technique at 1.5 T in 9 healthy subjects who underwent a protocol of repeated acetylcholine infusions at 2 different doses (16 and 64 microg/min) and N(G)-monomethyl-L-arginine (L-NMMA; 5 mg/min) into the brachial artery. Sodium nitroprusside was used as a control substance. For additional correlation with standard methods, the same protocol was repeated, and forearm blood flow was measured by strain gauge plethysmography. We obtained a significant increase in BOLD SI during acetylcholine infusion (64 microg/min) and a significant decrease for L-NMMA infusion (P<0.005 for both). BOLD SI showed a different kinetic signal than did blood flow, particularly after intermittent ischemia and at high flow rates.


CONCLUSIONS
In standard endothelial function tests, BOLD MRI detects a dissociation of tissue Hb oxygenation from blood flow. BOLD MRI may be a useful adjunct in assessing endothelial function.
Utz
Wolfgang
W
Medical Faculty of the Charité, Franz Volhard Klinik HELIOS Klinikum-Berlin at the Max Delbrück Center for Molecular Medicine, Berlin, Germany.
Jordan
Jens
J
Niendorf
Thoralf
T
Stoffels
Mandy
M
Luft
Friedrich C
FC
Dietz
Rainer
R
Friedrich
Matthias G
MG
D000109:Acetylcholine / Q000008:administration & dosage; D000328:Adult; D004730:Endothelium, Vascular / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000008:administration & dosage; D006801:Humans; D007261:Infusions, Intra-Arterial; D007511:Ischemia / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008955:Models, Cardiovascular; D018482:Muscle, Skeletal / Q000098:blood supply* / Q000502:physiology; D019335:Nitroarginine / Q000008:administration & dosage; D009599:Nitroprusside / Q000008:administration & dosage; D010100:Oxygen / Q000097:blood*; D010991:Plethysmography; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000008:administration & dosage
D004791:Enzyme Inhibitors; D014665:Vasodilator Agents; D009599:Nitroprusside; D019335:Nitroarginine; D000109:Acetylcholine; D010100:Oxygen