Korean J Radiol.  2017 ;18(4):585-596. 10.3348/kjr.2017.18.4.585.

Influence of B₁-Inhomogeneity on Pharmacokinetic Modeling of Dynamic Contrast-Enhanced MRI: A Simulation Study

Affiliations
  • 1Department of Radiology, Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea. kim.jeongkon@gmail.com
  • 2Center for Bioimaging of New Drug Development, Asan Institute for Life Sciences, Asan Medical Center, University of Ulsan College of Medicine, Seoul 05505, Korea.
  • 3Department of Radiology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea.
  • 4Department of Surgery, National Health Insurance Service Ilsan Hospital, Goyang 10444, Korea.
  • 5Biomedical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea.

Abstract


OBJECTIVE
To simulate the B₁-inhomogeneity-induced variation of pharmacokinetic parameters on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI).
MATERIALS AND METHODS
B₁-inhomogeneity-induced flip angle (FA) variation was estimated in a phantom study. Monte Carlo simulation was performed to assess the FA-deviation-induced measurement error of the pre-contrast R₁, contrast-enhancement ratio, Gd-concentration, and two-compartment pharmacokinetic parameters (K(trans), v(e), and v(p)).
RESULTS
B₁-inhomogeneity resulted in −23-5% fluctuations (95% confidence interval [CI] of % error) of FA. The 95% CIs of FA-dependent % errors in the gray matter and blood were as follows: −16.7-61.8% and −16.7-61.8% for the pre-contrast R₁, −1.0-0.3% and −5.2-1.3% for the contrast-enhancement ratio, and −14.2-58.1% and −14.1-57.8% for the Gd-concentration, respectively. These resulted in −43.1-48.4% error for K(trans), −32.3-48.6% error for the v(e), and −43.2-48.6% error for v(p). The pre-contrast R₁ was more vulnerable to FA error than the contrast-enhancement ratio, and was therefore a significant cause of the Gd-concentration error. For example, a −10% FA error led to a 23.6% deviation in the pre-contrast R₁, −0.4% in the contrast-enhancement ratio, and 23.6% in the Gd-concentration. In a simulated condition with a 3% FA error in a target lesion and a −10% FA error in a feeding vessel, the % errors of the pharmacokinetic parameters were −23.7% for K(trans), −23.7% for v(e), and −23.7% for v(p).
CONCLUSION
Even a small degree of B₁-inhomogeneity can cause a significant error in the measurement of pharmacokinetic parameters on DCE-MRI, while the vulnerability of the pre-contrast R₁ calculations to FA deviations is a significant cause of the miscalculation.

Keyword

Brain; Magnetic resonance imaging; Dynamic contrast enhancement; Monte Carlo method; Phantoms, imaging

MeSH Terms

Contrast Media/chemistry/*metabolism
Gadolinium/chemistry
Gray Matter/diagnostic imaging
Humans
Image Enhancement
Magnetic Resonance Imaging/instrumentation/*methods
*Models, Theoretical
Monte Carlo Method
Phantoms, Imaging
Contrast Media
Gadolinium
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