In vivo validation of cardiac spiral computed tomography using retrospective gating.
BACKGROUND
Cardiac functional assessment represents the basis for diagnostics and cardiac operation planning. Spiral computed tomography (CT) combines the advantages of three-dimensional imaging and high temporal resolution when using gating techniques. However, in vivo validation data of this novel imaging technology are lacking. The purpose of this study was to validate in vivo the new imaging method using retrospective gating and to evaluate the clinical usefulness of the achieved temporal resolution.


METHODS
In domestic pigs (n = 10, weight 35 to 40 kg) a flowmeter was placed surgically on the ascending aorta. Flow velocity integrated over systole served as the gold standard for left ventricular (LV) stroke volume (LVSV-FM). CT signal, projection data, pacemaker signal, and flow velocity were recorded simultaneously at constant heart rate (pacemaker, 90 beats per minute). End-systolic and end-diastolic frames were calculated by retrospective gating. LV volumes were traced, the difference representing CT stroke volume (LVSV-CT). Image data were three-dimensionally reconstructed using ray-tracing.


RESULTS
Temporal resolution was 170 ms. Correlation of stroke volumes was high (r = 0.94, mean difference 1.75 mL). Intraobserver (0.49 mL for LVEDV, 0.31 for LVESV) and interobserver variability (p = 0.21 and p = 0.06, respectively) were low. Postprocessing resulted in four-dimensional beating-heart models useful for operation planning.


CONCLUSIONS
Spiral CT using retrospective gating was validated in vivo. Clinically acceptable temporal resolution and accuracy in determining cardiac stroke volumes were found. As a true volumetric imaging modality the method may now play an important role in computer-assisted diagnostics and surgery.
Albers
Jörg
J
Department of Cardiac Surgery, University of Heidelberg, Heidelberg, Germany. joerg.albers@urz.uni-heidelberg.de
Boese
Jan M
JM
Vahl
Christian F
CF
Hagl
Siegfried
S
D000818:Animals; D001783:Blood Flow Velocity; D002304:Cardiac Pacing, Artificial; D003971:Diastole / Q000502:physiology; D004562:Electrocardiography; D006339:Heart Rate / Q000502:physiology; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D017078:Laser-Doppler Flowmetry; D012680:Sensitivity and Specificity; D012984:Software; D013318:Stroke Volume / Q000502:physiology*; D013552:Swine; D013599:Systole / Q000502:physiology*; D036542:Tomography, Spiral Computed / Q000379:methods*; D016277:Ventricular Function, Left / Q000502:physiology*