Assessment of left ventricular perfusion, volumes, and motion in mice using pinhole gated SPECT.
Quantitative functional normal data should be a prerequisite before applying SPECT in murine models of cardiac disease. Therefore, we investigated the capability of in vivo pinhole gated SPECT for establishment of a reference database for left ventricular myocardial perfusion, volumes, and motion in normal mice.


METHODS
A small-animal dedicated pinhole gamma-camera with a field of view of 17 cm and a focal distance of 12 cm was used with a 1.5-mm pinhole and a 2.5-cm radius of rotation. Phantoms were designed to test spatial resolution and microvolume measurements of accuracy. Eight adult normal mice (CD1) were studied using a heated mixture of air (0.3 L/min) and 1.5%-2.5% isoflurane for anesthesia. For myocardial perfusion, 350-450 MBq of (99m)Tc-tetrofosmin were used in 0.15-0.25 mL. Gated acquisitions (8 or 10 time bins per cardiac cycle) were obtained using a 180 degrees circular arc and 48 anterior projections of 300 R-R intervals. Image reconstruction was done using a specific Algebraic Reconstruction Technique (ART) cone-beam algorithm. For quantification, reconstructed images were processed using standard nuclear medicine software.


RESULTS
Millimetric spatial resolution and volume calibration linear relationships (r(2) = 0.99) in the 10- to 100-muL range were obtained in phantoms and used to scale in vivo volume values. In mice, left ventricular perfusion was lower in the apex (65% +/- 6%) versus lateral (72% +/- 5%), inferior (74% +/- 5%), septum (75% +/- 4%), and anterior (74% +/- 2%) walls. The left ventricular ejection fraction was 60% +/- 9%, end-diastolic volume was 50 +/- 8 muL, end-systolic volume was 20 +/- 6 muL, stroke volume was 29.5 +/- 6 muL, and cardiac output was 9.6 +/- 1.6 mL/min. Wall thickening was higher in the apex (47% +/- 12%) versus lateral (30% +/- 9%), inferior (33% +/- 8%), septum (37% +/- 10%), and anterior (33% +/- 10%) walls.


CONCLUSIONS
This work shows that in vivo pinhole gated SPECT can be used for assessment of left ventricular perfusion, volumes, and cardiac function in normal mice.
Constantinesco
André
A
Service de Biophysique et Médecine Nucléaire, Centre Hospitalo-Universitaire Hautepierre, 1 Avenue Moliere, 67098 Strasbourg, France. andre.constantinesco@chru-strasbourg.fr
Choquet
Philippe
P
Monassier
Laurent
L
Israel-Jost
Vincent
V
Mertz
Luc
L
D000818:Animals; D002302:Cardiac Output; D016208:Databases, Factual; D004562:Electrocardiography; D005260:Female; D015637:Gated Blood-Pool Imaging; D006321:Heart / Q000000981:diagnostic imaging* / Q000502:physiology; D006339:Heart Rate; D051379:Mice; D009068:Movement; D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019047:Phantoms, Imaging; D019275:Radiopharmaceuticals; D012016:Reference Values; D013318:Stroke Volume; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods; D016277:Ventricular Function, Left
D009943:Organophosphorus Compounds; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C078700:technetium tc-99m tetrofosmin