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Abstract
Background
Diffuse myocardial fibrosis may be quantified with cardiovascular magnetic resonance
(CMR) by calculating extra-cellular volume (ECV) from native and post-contrast T1
values. Previous studies have used either infusion or single bolus contrast administration.
In clinical practice however split dose contrast injection is used as part of a stress/rest
protocol in stress perfusion studies. The effects of using such an injection regime
on ECV calculation is unknown.
This study aimed to assess the effects of split dose versus single bolus contrast
administration on ECV calculation.
Methods
Ten healthy volunteers were studied on a 3.0 Tesla (Philips Achieva TX) MR system
and underwent three separate CMR studies over a mean of 30 days. In one study, contrast
was administered as a single bolus (Gadovist 0.15mmol/kg). In two further CMR studies,
contrast was given in two boluses (0.075mmol/kg per bolus) as part of an adenosine
stress/rest perfusion protocol, separated by 12 minutes. T1 maps were acquired pre
contrast and 15 minutes following the single bolus or second contrast injection. T1
measurements were made in the inter-ventricular septum. Means and standard deviations
were compared between MOLLI T1 estimates and ECV calculated.
Results
Volunteer mean age was 27 ± 3yrs, BSA corrected LVEDV (101 ± 12ml/m2) and LV mass
(52 ± 7 g/m2) were normal. No perfusion defects or scar were identified in the 10
volunteers. ECV agreed between bolus and split dose contrast administration (coefficient
of variability 5.78%, bias -0.993, 95% CI -4.495 to 2.509, r2=0.801, p>0.001)(figure
1). Inter-study agreement with split dose administration was good (coefficient of
variability, 5.67%, bias -0.018, 95% CI -4.045 to 4.009, r2=0.766, p>0.001)(figure
2).
Figure 1
Bland Altman plot of agreement between ECV estimated using single bolus and split-dose
contrast administrations (bias -0.993, 95% CI -4.495 to 2.509, r2=0.801, p=0.00).
Figure 2
Bland Altman plot of agreement of ECV estimates between visit 1 and 2 using split-dose
administration (bias -0.018, 95% CI -4.045 to 4.009, r2=0.766, p=0.00)
Conclusions
ECV quantification using split dose contrast administration is reproducible and in
healthy controls agrees well with previously validated methods. This suggests that
perfusion CMR studies may incorporate assessment of tissue composition by ECV based
on T1 mapping.
Funding
AKM is funded by a British Heart Foundation Project Grant (PG/14/10/30641)
DAB has a Research Doctoral Fellowship from the National Institute for Health and
Research (DRF-2012-05-155)
SP is funded by a British Heart Foundation Senior Fellowship (FS/10/62/28409).
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