Purpose: The aim of this study was to investigate the impact of contrast agent (CA) dose and acquisition timing after CA injection on the size of hyperenhancement
Methods and Materials: Nine patients with chronic myocardial infarction MI underwent two MR scans on a 1.5 Tesla system. TrueFISP-Cine sequences were performed to identify the area of myocardial infarction via altered regional wall motion (temporal resolution 35 ms). Vertical (VLA) and horizontal (HLA) long axis and short axis (SA) cines encompassing the entire left ventricle were acquired. To follow image contrast changes over time, two SA slices were chosen for ceMRI imaging. These were acquired in an interleaved fashion every other minute until 40 minutes after contrast agent injection (Gadolinium-DTPA, 0.1 mmol/kg body weight, segmented inversion-recovery TurboFLASH, constant TI of 260 ms). To quantify the total mass of non-viable myocardium, between minutes 20 and 28, VLA, HLA and SA ce-MRI images encompassing the entire left ventricle were acquired. To determine the influence of contrast agent dose, the protocol was repeated on day 2 with double dose contrast agent (0.2 mmol Gd-DTPA/kg body weight), using the identical imaging planes and acquisition protocol
Results: Total mass of hyperenhancement was lower for single dose CA between 20 and 28 minutes (9.0% vs. 14.2% for single and double dose, respectively [p = 0.03]). 10 to 18 minutes after CA injection, there was no significant difference between the two doses. No significant difference between mass of hyperenhancement and the internal "gold standard" (mass of hyperenhancement at 20 minutes with double dose contrast agent) was seen between 6 and 28 minutes for single dose and between 10 and 40 minutes for double dose.
Conclusion: Based on our results, a single dose of contrast agent may be sufficient for delayed enhancement imaging. The time point for measuring the exact infarct size should be between 10 and 18 minutes after single dose CA injection, thereby minimizing costs and CA dose. Use of standardized protocols for ce-MRI is important for comparison of results obtained at various CMR sites.
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