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Cardiac 16-MDCT for anatomic and functional analysis: assessment of a biphasic contrast injection protocol.

OBJECTIVE
The purpose of this study was to determine the optimal contrast injection protocol for clear delineation of the endocardial and epicardial contours and coronary vessels in anatomic and functional imaging with cardiac 16-MDCT.


SUBJECTS AND METHODS
Thirty-eight patients were allocated to three groups according to contrast injection protocol: a long-duration biphasic protocol in which diluted contrast material was used in the latter phase (protocol A, 13 patients); a uniphasic protocol with saline flush (protocol B, 12 patients); a uniphasic protocol without a flush (protocol C, 13 patients). Six regions of interest were drawn within the left ventricle (LV), right ventricle (RV), and interventricular septum along the z-axis. Mean ventricular attenuation, mean difference between maximum and minimum ventricular attenuation, and ventricular-myocardial contrast-to-noise ratio (CNR) were calculated. Attenuation and visualization of the coronary vessels also were compared.


RESULTS
The difference between maximum and minimum RV attenuation was significantly smaller in group A (58.1 H) than in groups B (179.5 H) and C (157.0 H). RV-myocardial CNR was significantly higher in group A (9.0) than in group B (5.5). The mean LV attenuation, difference between maximum and minimum LV attenuation, and LV-myocardial CNR were not significantly different among three groups. In protocol A, both endocardial and epicardial contours were clearly delineated, and cardiac functional analysis was feasible in all cases. Average attenuation and visualization of the coronary vessels were not significantly different among groups. The diagnostic accuracies in detection of coronary stenosis were 92%, 93%, and 91%, respectively, for protocols A, B, and C.


CONCLUSION
The long-duration contrast injection protocol with diluted contrast material is optimal for assessing the coronary vessels and cardiac function.