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Purpose: To experimentally investigate the optimum dose of an iron-oxide-based blood pool agent for spiral coronary MR angiography (MRA), and the difference between single and multiple spiral excitations in each cardiac cycle. Materials and Methods:Images using single and triple spiral excitations in each cardiac cycle were obtained in late diastole of the left main coronary artery in eight pigs following an inversion prepulse. Measurements were obtained before and after injection of increasing doses of an iron oxide blood pool agent (Clariscan) corresponding to concentrations of 0.8, 2.2, and 3.9 mg Fe/kg BW. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured.Results: For 0.8 mg Fe/kg BW relative to precontrast values, a significant increase was observed for both one (SNR: 2.3, CNR: 3.8) and three (SNR: 1.4, CNR: 2.2) excitations (P Ͻ 0.01). When the dose was increased from 0.8 mg Fe/kg BW to 2.2 mg Fe/kg BW, only the SNR (P Ͻ 0.01) increased further. Significantly higher CNR (1.6 -1.8) and SNR (1.4 -1.6) values were seen for one excitation relative to three excitations at all concentrations (P Ͻ 0.05). Conclusion:At low concentrations, an iron oxide blood pool agent can increase SNR and CNR significantly with both single excitation and triple excitations using an inversion-prepared spiral acquisition scheme. At higher concentrations, T2* effects reduce image quality.

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