64 Chapter 5 Image acquisition Cardiac Magnetic Resonance image acquisition was performed on a 1.5 Tesla scanner (Magnetom Avanto-fit, Siemens Healthineers, The Hague, Netherlands) equipped with a phased-array five channel coil for cardiac imaging. Long-axes cines were visualized in 4 chamber, 2 chamber left, and left ventricular outflow tract views. The heart was covered from the atria to the ventricular apex using short-axis cine views. Native (long) T1 series were performed covering basal, mid and apex in three corresponding short axis planes, using an optimized motion corrected single breath hold 5(3)3 MOLLI sequence. The gadolinium based contrast agent DotaremTM was used (0.2 mmol/kg body weight at 2mL/s). Equivalent post contrast (short) T1 series were scanned 12 minutes after injection. Matching long and short axis planes were used for late gadolinium enhancement imaging, starting 15 minutes after injection, using standard clinical sequences with standard parameters. All images were acquired anonymously in accordance with the Good Clinical Practice guidelines of our centre and stored digitally for offline analysis. Image analysis The acquired images were post-processed with Circle CVI42 (Circle Cardiovascular Imaging, Calgary, Canada [version 5.6.7]). T1 values (time in ms) were measured by drawing endocardial and epicardial left ventricular contours manually in the basal, mid, and apical short axis views on the native 8 acquired echo images and subsequently registered and subdivided using the ESC 16 segment model.[22] All delineations were performed by one observer (CG) and checked by a dedicated cardiac radiologist (NP). Extracellular volume fraction (ECV) was calculated using the standard formula with correction for red blood cell density in the blood pool (hematocrit).[24] The hematocrit was obtained on the day of the MRI acquisition. Statistical analysis SPSS (version 23) was used for statistical analysis. All data were expressed with mean ± standard deviation(SD). The irradiated group and non-irradiated control groups were compared using a t test for continuous data and a χ2 test for categorical data. All statistical tests were two-sided and group differences were considered statistically significant if at p < 0.05. ECV was considered to be elevated if it deviates >2 SD above the mean global ECV of the control group. To investigate a possible relationship between radiation dose to the segments of the LV myocardium and ECV, we calculated these individual segments. All statistics were performed at the LV myocardial segment level using a mixed-model regression analysis with random intercept to correct for patient-
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