Quantitative time‐of‐flight MR angiography for simultaneous luminal and hemodynamic evaluation of the intracranial arteries

• Published in: Magnetic resonance in medicine Vol. 87; no. 1; pp. 150 - 162
• Main Authors: Koktzoglou, Ioannis, Huang, Rong, Edelman, Robert R.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.01.2022
• Subjects: Angiography; Arteries; Background noise; Blood flow; Cartesian coordinates; Computer vision; Correlation coefficients; Data sampling; Evaluation; flow; Flow velocity; Hemodynamics; Humans; Image analysis; Image contrast; Image processing; Imaging, Three-Dimensional; intracranial; Magnetic Resonance Angiography; Noise; Phase contrast; qTOF; quantitative; time‐of‐flight; Veins & arteries; Velocity; intracranial; phase contrast; quantitative; flow; qTOF; time-of-flight
• ISSN: 0740-3194; 1522-2594; 1522-2594
• DOI: 10.1002/mrm.28969

Purpose To report a quantitative time‐of‐flight (qTOF) MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries. Methods Implemented using a thin overlapping slab 3D stack‐of‐stars based 3‐echo FLASH readout, qTOF was tested in a flow phantom and for imaging the intracranial arteries of 10 human subjects at 3 Tesla. Display of the intracranial arteries with qTOF was compared to resolution‐matched and scan time‐matched standard Cartesian 3D time‐of‐flight (TOF) MRA, whereas quantification of mean blood flow velocity with qTOF, done using a computer vision‐based inter‐echo image analysis procedure, was compared to 3D phase contrast MRA. Arterial‐to‐background contrast‐to‐noise ratio was measured, and intraclass correlation coefficient was used to evaluate agreement of flow velocities. Results For resolution‐matched protocols of similar scan time, qTOF portrayed the intracranial arteries with good morphological correlation with standard Cartesian TOF, and both techniques provided superior contrast‐to‐noise ratio and arterial delineation compared to phase contrast (20.6 ± 3.0 and 37.8 ± 8.7 vs. 11.5 ± 2.2, P < .001, both comparisons). With respect to phase contrast, qTOF showed excellent agreement for measuring mean flow velocity in the flow phantom (intraclass correlation coefficient = 0.981, P < .001) and good agreement in the intracranial arteries (intraclass correlation coefficient = 0.700, P < .001). Stack‐of‐stars data sampling used with qTOF eliminated oblique in‐plane flow misregistration artifacts that were seen with standard Cartesian TOF. Conclusion qTOF is a new 3D MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries that provides significantly greater contrast‐to‐noise ratio efficiency than phase contrast and eliminates misregistration artifacts from oblique in‐plane blood flow that occur with standard 3D TOF.