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Imaging contrast agent concentration and extracellular volume fraction in the right ventricle
Journal of Cardiovascular Magnetic Resonance volume 14, Article number: O109 (2012)
Globally increased myocardial extracellular volume fraction (ECVF) has been associated with diffuse myocardial fibrosis. ECVF can be estimated using blood and tissue concentrations of gadolinium contrast agent, [Gd], which are calculated using baseline and post-contrast T1 values . To date, T1 quantification has been limited to the left ventricle (LV) with moderate spatial resolution (~2 mm) and long imaging windows (>200 ms) to accommodate breath-hold acquisitions. These methods have insufficient spatial resolution to image the relatively thin-walled right ventricle (RV). A new cine-imaging approach for the measurement of contrast agent concentration and ECVF using saturation-recovery preparation is evaluated in the LV and RV.
A saturation-recovery gated-segmented cine SSFP sequence, similar to the multi-contrast late enhancement imaging method , provides a short acquisition window (< 50 ms) enabling end-systolic imaging and higher spatial resolution (~1 mm). Bloch equation simulations of the sequence were used to generate a look-up table to relate the measured ratio of post- to pre-contrast image intensity to the tissue concentration of contrast agent (CLAIR - Contrast Level Assessment using Intensity Ratios). Short axis images were acquired in 9 subjects from an ongoing study of heart failure (Alberta HEART), with contrast-enhanced images at 15 min post 0.15mmol/kg Gadovist. Typical CLAIR pulse sequence parameters: FOV=300mm, 256 matrix, 8 mm slice, flip angle=73°, TE=1.66ms, TR=3.32ms, VPS=14, TI=300ms. Average LV [Gd] in subjects was compared to values obtained using a saturation-recovery SSFP T1-mapping sequence  calculated using [Gd] = ΔR1/r (ΔR1 = change in 1/T1 with contrast, r = relaxivity). For both methods ECVF = (1-Hct)*[Gd]Tissue/[Gd]Blood, with [Gd]Blood obtained via the T1 mapping sequence and an assumed Hct of 0.4. Data are presented as mean±SD and differences compared with the two-tailed paired Student’s t-test.
Subject age was 60.7±14.3yrs, with 5 males. Images from an individual using CLAIR (end-systole) and conventional T1-mapping (end-diastole) are shown in Fig. 1. LV [Gd] is not statistically different between CLAIR and T1 mapping (0.188±0.042 vs. 0.198±0.029 mM, p=0.151) and is significantly correlated between methods (p<0.01) (Fig. 2 left). LV ECVF is not statistically different between CLAIR and T1 mapping (0.216±0.027 vs. 0.231±0.027, p=0.120) with negligible bias (Fig. 2 right) between the two methods. CLAIR RV [Gd] (0.212±0.066 mM) and ECVF (0.245±0.054) were not statistically different from LV values (p=0.134 and p=0.093).
CLAIR yields similar LV myocardial contrast concentration and ECVF in the LV to T1-mapping and provides sufficient temporal and spatial resolution for end-systolic RV imaging.
Alberta HEART Team Grant.
Donahue : Magn Reson Med. 34 (3): 423-32.
Connelly : JMRI. 30: 771-7.
Chow : J Cardiov Magn Reson. 13 (Suppl1): P31-
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Pagano, J.J., Chow, K., Paterson, I. et al. Imaging contrast agent concentration and extracellular volume fraction in the right ventricle. J Cardiovasc Magn Reson 14 (Suppl 1), O109 (2012). https://doi.org/10.1186/1532-429X-14-S1-O109
- Left Ventricle
- Right Ventricle
- Contrast Agent Concentration
- Diffuse Myocardial Fibrosis
- Extracellular Volume Fraction