Wang Jing^{1}, Yudong Zhang^{2}, Yang Fan^{3}, HaiBin Shi^{2}, and Xiaoyan Liu^{1}

^{1}Center for Medical Device Evaluation, CFDA, Beijing, China, People's Republic of, ^{2}Department of Radiology, the First Affiliated Hospital with Nanjing Medical University Nanjing, Nanjing, China, People's Republic of, ^{3}GE Healthcare, MR Research China, Beijing, China, People's Republic of

### Synopsis

**This
study compares three methods for quantitatively analyzing dynamic
contrast-enhanced MRI datasets for the extraction of myocardial perfusion,
permeability, and other hemodynamic parameters. The two-compartment exchange
model and the adiabatic approximation to the tissue homogeneity models are
compared with reference to model-free deconvolution. The goal was to determine
if these three models could reliably estimate hemodynamic parameters and be
able to distinguish between normal patients and those with hypertrophic
cardiomyopathy. Results demonstrate that all three methods yield consistent
estimates for perfusion, blood volume, and mean transit times, and that these
parameters were significantly different for the hypertrophic heart.**### INTRODUCTION

First-pass dynamic
contrast-enhanced (DCE) MRI with kinetic analysis
models was know as a reliable tool to quantify myocardial F

^{1}, but not yet reached agreement for
myocardial permeability.
Recently, an adiabatic approximation to the tissue homogeneity model
(AATH) and two-compartment
exchange model (2CXM), have been
recognized as promising ways for F
and PS quantification in brain, breast and prostate

^{2}. This study was to explore
the feasibility of cardiac function evaluation by first-pass DCE-MRI
with 2CXM and AATH in healthy
subjects
and hypertrophic
cardiomyopathy (HCM) patients.

### METHODS

All examinations were performed on a 1.5 T
GE MRI (14 HCM patients, 12 healthy subjects, no age difference). For MF
analysis, h(t) was determined by deconvolving AIF to tissue enhancement signal, then calculated F, Vp and
MTT maps. For 2CXM and AATH, the plots of F, Vp, MTT, E, and PS were
performed using Levenberg-Marquardt nonlinear least squares algorithm. Because ventricular septum is the most
representative place for characterizing an asymmetrical
hypertrophy in HCM patients, regional
F, Vp, MTT, E and PS were calculated using manual segmentation in middle short-axis
slices.
Bland-Altman plot was adopted to verify the concordance of 2CXM and AATH
with MF (the average of F, Vp and MTT as X-axis, the difference as Y-axis).
Mean difference, 95% limits of agreement, and the Pearson correlation
coefficients between both methods were reported. With regards to the validation
of model outputs, the quantitative cardiac parameters (F, Vp, MTT, E and PS)
was compered between normal and HCM groups by independent-samples t test.

### RESULTS

Fig.
1 shows representative
myocardial DCE results estimated by MF, 2CXM
and AATH. Fig. 2 shows the ROI-based fitting results of all
three methods. Bland-Altman plot (Fig.3) shows that the mean bias of F between the three
methods is 0.20 mL/g/min (-0.25
to 0.64 mL/g/min, 95% confidence interval [CI]). There are one sample in 2CXM below, and
one in AATH above the 95% limits of
agreement, demonstrating high concordance of both methods with MF in F quantitation. The correlation plots show
that the slop of Y (F2CXM) versus X (FMF) is 1.42 (intercept = -0.19 mL/g/min, ρ = 0.88), and the slop of Y (FAATH)
versus X (FMF) is 1.23 (intercept = 0.12 mL/g/min, ρ = 0.82). The mean bias of Vp between all three
methods is 0.02 mL/g (-0.11
to 0.08 mL/ g of 95% CI). There are two samples in 2CXM and one in AATH below the 95% limits of
agreement. The slop of Y (Vp2CXM) versus
X (VpMF) is 1.28 (intercept of -0.04 mL/g, ρ = 0.70), and the slop of Y (VpAATH) versus X (VpMF)
is 1.15 (intercept = -0.01
mL/g, ρ = 0.44). The mean bias of MTT of all three
methods is 2.8 s. (-8.7
to 14.4 s of 95% CI). There are two samples in 2CXM below the 95%
limits of agreement and non
for AATH. The slop of Y (MTT2CXM) versus X (MTTMF) is 1.28
(intercept = -5.96s, ρ = 0.60), and the slop of Y (MTTAATH)
versus X (MTTMF) is 0.59 (intercept = 1.83 s, ρ = 0.39). For
myocardial permeability comparison between AATH and 2CXM, mean bias of E is 35.1%
(-10.8% to 80.7% of 95% CI), and mean bias of PS is 0.23
mL/g/min (-0.75 to 1.20 mL/g/min
of 95% CI). However,
there is no statistically significant correlation in E or PS between both
methods (p > 0.05). Fig. 4 shows the
representative parameters acquired by AATH in a HCM patient. The hypertrophic myocardium shows
evident delay-enhancement in ventricular septum and inferior wall (arrow) from
the short-axis delay-enhanced T1-weighted image. For permeability
maps derived from AATH, it shows inhomogeneous decrease in regional F,
combining with inhomogeneous increase in E and Tc, extremely in these regions
with replaced myocardial fibrosis (arrows), indicating an impaired blood supply
and structural abnormality of involved myocardium.

### CONCLUSION

This study demonstrated that myocardial perfusion can be well obtained
from first-pass DCE-MRI with currently proposed approaches. All the three models
show high accordance in determining myocardial F (coefficient correlation r > 0.8). With regards to quantitation of
myocardial permeability, although myocardial E and/or PS obtained by 2CXM and AATH
reflected significant difference between HCM and normal group, there is yet
great inconsistence of the results between the proposed two methods, indicating
the limitation
of current imaging techniques in evaluation of myocardial permeability in physiopathologic conditions.

### Acknowledgements

No acknowledgement found.### References

[1]
Coelho-Filho OR,et al. MR myocardial perfusion imaging. Radiology 2013.
[2] Korporaal
JG, et al. Tracer kinetic model selection for dynamic contrast-enhanced
computed tomography imaging of prostate cancer. Invest Radiol 2012.