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

Area of Science:

• Medical Imaging
• Biophysics
• Pharmacokinetics

Background:

• Dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) is crucial for assessing tissue perfusion and vascularity.
• Accurate quantification of contrast agent concentration, such as gadolinium (Gd), is essential for reliable DCE-MRI analysis.
• Traditional methods often require a separate precontrast scan to measure longitudinal relaxation time (T10), adding to scan time and complexity.

Purpose of the Study:

• To evaluate the feasibility of a 2-flip angle (FA) approach during DCE-MRI to estimate plasma Gd concentration.
• To determine if this method can eliminate the need for a precontrast T10 measurement.
• To assess the accuracy of Gd concentration estimation compared to traditional methods and direct measurement.

Main Methods:

• T1-weighted DCE-MRI experiments were performed on mice using a 2-FA protocol within a single scan.
• Plasma Gd concentrations were estimated using T10 derived from the 2-FA data (T1T), precontrast T10 (T1M), and a literature T10 (T1C).
• Estimated Gd concentrations were compared against measurements obtained via inductively coupled plasma mass spectrometry (ICP-MS).

Main Results:

• The T10 estimated from the 2-FA method (T1T) showed strong correlation with precontrast T10 measurements (T1M, r=0.81).
• Gd concentrations estimated using T1T and T1M ([Gd]T1T, [Gd]T1M) closely agreed with ICP-MS measurements ([Gd]MS), with strong correlations (r=0.85 and r=0.70, respectively).
• The 2-FA method yielded significantly more accurate Gd concentration estimates than using a constant T10 (T1C).

Conclusions:

• The 2-flip angle approach during DCE-MRI is feasible for estimating plasma Gd concentration.
• This method effectively bypasses the requirement for an additional precontrast T1 measurement.
• The 2-FA method offers a more accurate and efficient alternative for Gd quantification in DCE-MRI studies.