Myocardial perfusion and intracapillary blood volume in rats at rest and with coronary dilatation: MR imaging in vivo with use of a spin-labeling technique.
OBJECTIVE
To validate a magnetic resonance (MR) imaging technique that is not first pass and that reveals perfusion and regional blood volume (RBV) in the intact rat.


METHODS
Measurement of perfusion was based on the perfusion-sensitive T1 relaxation after magnetic spin labeling of water protons. RBV was determined from steady-state measurements of T1 before and after administration of an intravascular contrast agent. The colored microsphere technique was used as a reference method for perfusion measurement. RBV and perfusion maps were obtained with the rats at rest and during administration of 3 mg of adenosine phosphate per kilogram of body weight per minute.


RESULTS
At MR imaging, perfusion during resting conditions was 3.5 mL/g/min +/- 0.1 (SEM), and RBV was 11.6% +/- 0.6 (SEM). Adenosine phosphate significantly increased perfusion to 4.5 mL/g/min +/- 0.3 (SEM) and decreased mean arterial pressure from 120 mm Hg to 65 mm Hg, which implies a reduction of coronary resistance to 40% of baseline. RBV increased consistently to 23.8% +/- 0.6 (SEM).


CONCLUSIONS
The study results show that quantitative mapping of perfusion and RBV may be performed noninvasively by means of MR imaging in the intact animal. The presented method allows determination of vasodilative and perfusion reserve, which reflects the in vivo regulation of coronary microcirculation for a given stimulus.
Waller
C
C
Medical Institute, University of Würzburg, Josef-Schneider-Str. 2, 97080 Würzburg, Germany. wallerphysik.uni-wuerzburg.de
Kahler
E
E
Hiller
K H
KH
Hu
K
K
Nahrendorf
M
M
Voll
S
S
Haase
A
A
Ertl
G
G
Bauer
W R
WR
D000241:Adenosine / Q000494:pharmacology; D000418:Albumins; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001810:Blood Volume / Q000187:drug effects / Q000502:physiology*; D002196:Capillaries / Q000187:drug effects / Q000502:physiology; D003287:Contrast Media; D003326:Coronary Circulation / Q000187:drug effects* / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D019786:Gadolinium DTPA; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000502:physiology; D008863:Microspheres; D010865:Pilot Projects; D011522:Protons; D051381:Rats; D017208:Rats, Wistar; D012146:Rest; D013113:Spin Labels; D013223:Statistics as Topic; D014655:Vascular Resistance / Q000187:drug effects / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*; D014867:Water
D000418:Albumins; D003287:Contrast Media; D011522:Protons; D013113:Spin Labels; D014665:Vasodilator Agents; D014867:Water; D019786:Gadolinium DTPA; D000241:Adenosine