Consensus-Based Technical Recommendations for Clinical Translation of Renal Phase Contrast MRI

Abstract

Background: Phase-contrast (PC) MRI is a feasible and valid noninvasive technique to measure renal artery blood flow, showing potential to support diagnosis and monitoring of renal diseases. However, the variability in measured renal blood flow values across studies is large, most likely due to differences in PC-MRI acquisition and processing. Standardized acquisition and processing protocols are therefore needed to minimize this variability and maximize the potential of renal PC-MRI as a clinically useful tool.

Purpose: To build technical recommendations for the acquisition, processing, and analysis of renal 2D PC-MRI data in human subjects to promote standardization of renal blood flow measurements and facilitate the comparability of results across scanners and in multicenter clinical studies.

Study type: Systematic consensus process using a modified Delphi method.

Population: Not applicable.

Sequence field/strength: Renal fast gradient echo-based 2D PC-MRI.

Assessment: An international panel of 27 experts from Europe, the USA, Australia, and Japan with 6 (interquartile range 4-10) years of experience in 2D PC-MRI formulated consensus statements on renal 2D PC-MRI in two rounds of surveys. Starting from a recently published systematic review article, literature-based and data-driven statements regarding patient preparation, hardware, acquisition protocol, analysis steps, and data reporting were formulated.

Statistical tests: Consensus was defined as ≥75% unanimity in response, and a clear preference was defined as 60-74% agreement among the experts.

Results: Among 60 statements, 57 (95%) achieved consensus after the second-round survey, while the remaining three showed a clear preference. Consensus statements resulted in specific recommendations for subject preparation, 2D renal PC-MRI data acquisition, processing, and reporting.

Data conclusion: These recommendations might promote a widespread adoption of renal PC-MRI, and may help foster the set-up of multicenter studies aimed at defining reference values and building larger and more definitive evidence, and will facilitate clinical translation of PC-MRI.

Level of evidence: 1 TECHNICAL EFFICACY STAGE: 1.

Keywords: consensus; kidney; phase-contrast MRI; renal blood flow; standardization.

FIGURE 1

Schematic representation of 2D phase‐contrast magnetic resonance imaging (PC‐MRI) acquisition and processing. (a) A single axial, coronal, and sagittal 2D slice of the 3D vascular survey, showing hyperintense arteries, to illustrate planning of the 2D PC‐MRI acquisition plane, (b) Acquired phase and magnitude images depicting the renal artery in the center. A circular ROI was drawn on the magnitude images and copied to the phase images. The temporal sequences show the evolution of the phase signal inside the vessel in the cardiac cycle, which is graphically shown in (c), a graph showing the mean and max velocity in the ROI during the cardiac cycle. PC‐MRI data were acquired using the recommended acquisition protocol in the University Medical Center Utrecht, the Netherlands and in the ASST Papa Giovanni XXIII, Bergamo, Italy.

FIGURE 2

Pulse diagram of the recommended sequence with typical timings of the shot interval (Siemens and General Electric: repetition time), repetition time (Siemens and General Electric: echo spacing), and echo time.