Estimation of Contrast Agent Concentration in DCE-MRI Using 2 Flip Angles

Abstract

The aim of this study was to investigate the feasibility of using 2 flip angles (FAs) with an ultrashort echo time during dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) for estimation of plasma gadolinium (Gd) concentration without using a precontrast longitudinal relaxation time T 1 (T 10 ) measurement. Methods: T 1 -weighted DCE-MRI experiments were carried out with C57BL/6J mice using the scan protocol with 2 FAs over 3 sequential segments during 1 scan. The data with 2 FAs were used to estimate T 10 (T 1T ) during conversion of a timeintensity curve to the time-concentration curve. Three dosages of gadoliniumbased contrast agent were used to achieve a wide range of variability in Gd concentrations when measured at 10 minutes postinjection: 0.05 mmol/kg (n = 6), 0.1 mmol/kg (n = 11), and 0.15 mmol/kg (n = 7). For comparison, the signalto-concentration conversion was also conducted using the T 10 measured from the precontrast scan (T 1M ) as well as a constant T 10 (2.1 seconds) from the literature (T 1C ). The Gd concentrations ([Gd]) estimated using DCE-MRI data for the time of retro-orbital blood collection ([Gd] T1T , [Gd] T1M , and [Gd] T1C , respectively) were compared against the [Gd] of the blood samples measured by inductively coupled plasma mass spectrometry ([Gd] MS ). In addition, contrast kinetic model analysis was conducted on mice with GL261 brain tumors (n = 5) using the 3 different methods for T 10 . Results: T 1T strongly correlated with T 1M (r = 0.81). [Gd] T1M and [Gd] T1T were significantly different from [Gd] T1C . [Gd] T1M and [Gd] T1T were in good agreement with [Gd] MS with strong correlations (mean percentage error ± standard deviation) of r = 0.70 (16% ± 56%) and r = 0.85 (15% ± 44%), respectively. In contrast, [Gd] T1C had a weak correlation of r = 0.52 with larger errors of 33% ± 24%. The contrast kinetic model parameters of GL261 brain tumors using T 1T were not significantly different from those using T 1M . Conclusions: This study substantiates the feasibility of using the 2-FA approach during DCE-MRI scan to estimate [Gd] in the plasma without using an extra scan to perform precontrast T 1 measurements.

Rapid In Vitro Quantification of a Sensitized Gadolinium Chelate via Photoinduced Triplet Harvesting

“…Furthermore, our proposed assay can quantify gadolinium concentrations from the subnanomolar range up to 1 mM depending on the media. Further investigation into the accuracy of this fluorescent quantification method is warranted in applications of tumor pharmacokinetic modeling in preclinical and clinical studies …”

“…Further investigation into the accuracy of this fluorescent quantification method is warranted in applications of tumor pharmacokinetic modeling in preclinical and clinical studies. 3 …”

“… 4 , 5 However, accurate measurement of GBCA concentration using dynamic contrast-enhanced MRI remains challenging due to uncertainties in multiple factors such as: the arterial input function, GBCA relaxivity in tissue, the longitudinal relaxation rate of tissue, and radiofrequency coil in homogeneities. 3 For this reason, secondary methods of measuring GBCA concentrations can be especially useful.…”

“…Gadolinium (Gd) based contrast agents (GBCAs) are widely used in magnetic resonance imaging (MRI) and are especially important for early diagnoses of diseases such as cancer . By measuring contrast delivery and clearance to and from tumors, the use of GBCAs extends to grading tumors and assessing treatment response. , In this context, pharmacokinetic modeling of MRI signal changes can be used to estimate GBCA concentration in tissue, providing quantitative measurements of the tumor microcirculation environment. , However, accurate measurement of GBCA concentration using dynamic contrast-enhanced MRI remains challenging due to uncertainties in multiple factors such as: the arterial input function, GBCA relaxivity in tissue, the longitudinal relaxation rate of tissue, and radiofrequency coil in homogeneities . For this reason, secondary methods of measuring GBCA concentrations can be especially useful.…”