Phantom Validation of DCE-MRI Magnitude and Phase-Based Vascular Input Function Measurements.

Warren Foltz,Naren Nallapareddy,Brandon Driscoll,Ali Fatemi,Caroline Chung,Krishna Nayak,Cynthia Ménard,Catherine Coolens,Sangjune Laurence Lee

doi:10.18383/j.tom.2019.00001

Abstract

Accurate, patient-specific measurement of arterial input functions (AIF) may improve model-based analysis of vascular permeability. This study investigated factors affecting AIF measurements from magnetic resonance imaging (MRI) magnitude (AIFMAGN) and phase (AIFPHA) signals, and compared them against computed tomography (CT) (AIFCT), under controlled conditions relevant to clinical protocols using a multimodality flow phantom. The flow phantom was applied at flip angles of 20° and 30°, flow rates (3–7.5 mL/s), and peak bolus concentrations (0.5–10 mM), for in-plane and through-plane flow. Spatial 3D-FLASH signal and variable flip angle T1 profiles were measured to investigate in-flow and radiofrequency-related biases, and magnitude- and phase-derived Gd-DTPA concentrations were compared. MRI AIF performance was tested against AIFCT via Pearson correlation analysis. AIFMAGN was sensitive to imaging orientation, spatial location, flip angle, and flow rate, and it grossly underestimated AIFCT peak concentrations. Conversion to Gd-DTPA concentration using T1 taken at the same orientation and flow rate as the dynamic contrast-enhanced acquisition improved AIFMAGN accuracy; yet, AIFMAGN metrics remained variable and significantly reduced from AIFCT at concentrations above 2.5 mM. AIFPHA performed equivalently within 1 mM to AIFCT across all tested conditions. AIFPHA, but not AIFMAGN, reported equivalent measurements to AIFCT across the range of tested conditions. AIFPHA showed superior robustness.

Highlights

Dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) is a useful tool to measure blood vessel permeability and volume fractions within heterogeneous lesions, such as tumors [1]
At a 10° flip angle, considerable inflow bias was observed across the entire slice package at flow velocities above 3.2 cm/s for through-plane flow data (Figure 4C), whereas in-plane flow data were effectively acquired in steady-state at 0.6 relative to the field of view (FOV) for flow velocities up to 30 cm/s (9.5 mL/s) (Figure 4D)
In this study a multimodality flow phantom was used to compare the arterial input function (AIF) derived from 3D-FLASH magnitude and phase signals, against the gold standard DCE-computed tomography (CT) under similar conditions

Summary

Introduction

Dynamic contrast-enhanced magnetic resonance imaging (DCEMRI) is a useful tool to measure blood vessel permeability and volume fractions within heterogeneous lesions, such as tumors [1]. Analysis of DCE-MRI data commonly assumes a 2-compartmental model to generate functional parameters, such as the permeability surface area product per unit volume (Ktrans), size of the extracellular extravascular space (ve), and efflux rate constant (kep) [6, 7]. Accurate quantification of these permeability kinetic parameters is dependent on the application of an accurately measured arterial input function (AIF) from a major vessel in the vicinity of the tumor [8]. The AIF has been evaluated by using the magnetization magnitude signal in an artery, but the conversion from magnitude signal to absolute gadolinium contrast agent concentration (eg, Gd-DTPA) is susceptible to a number of factors including blood inflow effects, radiofrequency transmit field (B1) inhomogeneity, slice profile

Methods

Results

Conclusion