Measuring the arterial input function with gradient echo sequences.

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Medical Physics
• Pharmacokinetics

Background:

• Accurate measurement of the arterial input function (AIF) is crucial for quantitative dynamic contrast-enhanced MRI (DCE-MRI).
• Gradient echo sequences are commonly used for DCE-MRI, but their accuracy can be affected by factors like contrast agent concentration.
• Existing methods for AIF determination may lack precision, necessitating improved algorithms.

Purpose of the Study:

• To investigate the measurement of the arterial input function using gradient echo sequences.
• To develop and validate a partial volume correction algorithm for improved AIF determination.
• To assess the reproducibility of AIF measurements with the enhanced algorithm.

Main Methods:

• In vitro experiments were conducted to establish calibration curves for Gd-DTPA concentration effects on MR signal phase and amplitude.
• A partial volume correction algorithm was developed incorporating these calibration curves.
• The algorithm's accuracy was tested in phantom experiments and its reproducibility assessed in 16 patients.

Main Results:

• Calibration curves showed a linear increase in phase velocity and quadratic increase in DeltaR(2) with Gd-DTPA concentration.
• The partial volume correction algorithm significantly improved the accuracy of concentration measurements in phantom studies.
• In vivo studies demonstrated improved reproducibility of AIF determination using the corrected algorithm.

Conclusions:

• Gradient echo sequences can accurately measure the arterial input function when combined with a validated partial volume correction algorithm.
• The developed algorithm enhances the precision of contrast agent concentration measurement in DCE-MRI.
• This approach improves the overall reliability and reproducibility of quantitative MRI analyses.