ΔR1blood, a surrogate of blood-pool gadolinium concentration, is related to BMI, gender, LVEDVi, cardiac index and field strength at cardiac magnetic resonance late enhancement imaging.

Background: Late Gadolinium Enhancement (LGE) imaging is the cornerstone of tissue characterization via cardiac magnetic resonance imaging. The contrast-enhancing effect of gadolinium is caused by a linear increase of tissue longitudinal R1 relaxation rates (R1=1/T1). The change in R1 of blood pre- and post-contrast (ΔR1_blood) is therefore a surrogate for the blood-pool gadolinium concentration, which in turn correlates linearly to the tissue gadolinium concentration. The total volume of distribution for gadolinium is the extracellular volume of the body, which differs with body composition, potentially leading to variations in blood-pool and tissue gadolinium concentrations.

Methods: This study is a hypothesis-generating secondary analysis of a dataset of 1098 patients who underwent contrast CMR between August 2014 and November 2020 at a tertiary center. ΔR1_blood was calculated from T1 relaxation time maps acquired before and approx. 15minutes after application of 0.15mmol/kg gadobutrol. Explorative data analysis and multiple linear regression was performed to assess the influence of body mass index (BMI), gender, age, cardiac index (CI), Hematocrit (HCT) and left ventricular end-diastolic volume index (LVEDVi) on ΔR1_blood.

Results: In bivariate analysis, ΔR1_blood showed moderate correlation to BMI and weak correlation to LVEDVi, Hct and CI. The correlation to BMI was higher in women (r=0.52 at 1.5T and r=0.47 at 3T) than in men (r=0.27 at 1.5T and r=0.37 at 3T). Multiple linear regression showed independent predictive value of BMI, BMI:gender, gender, cardiac index (CI), field strength (FS) and LVEDVi (R² =.268, P<.001), with BMI remaining the strongest individual predictor (b = 0.032 [0.025; 0.040], η² = 0.13, P<.001).

Conclusion: ΔR1_blood, a measurement of gadolinium contrast enhancement in the blood-pool and a surrogate of plasma C_Gd at the time of late enhancement imaging, showed moderate association with BMI, FS and gender and weak association with LVEDVi and CI. Further research is necessary to assess the need for individualized gadolinium dosing.