Sequence optimization to reduce velocity offsets in cardiovascular magnetic resonance volume flow quantification--a...

Area of Science:

• Medical Imaging
• Cardiovascular Imaging
• Magnetic Resonance Imaging

Background:

• Eddy currents induce velocity offsets, impacting cardiovascular magnetic resonance (CMR) flow quantification accuracy.
• Existing theoretical understanding of eddy currents has not yielded effective guidelines for optimizing CMR flow quantification sequences.

Purpose of the Study:

• To identify correlations between CMR protocol parameters and velocity errors in clinical flow measurements.
• To evaluate velocity offsets across multiple vendors and scanner types in a multi-vendor study.

Main Methods:

• Nine 1.5T scanners from three vendors were evaluated using a stationary phantom.
• Protocol parameters were varied from a clinical breath-hold flow protocol across three orientations.
• Exploratory measurements investigated time delay, velocity encoding asymmetry, and gradient parameters.

Main Results:

• Significant variation in velocity offset behavior was observed among scanners (SD 0.3-0.9 cm/s).
• No tested protocol settings consistently reduced velocity offsets below 0.6 cm/s across all orientations and scanner types.
• Oblique aortic and pulmonary slices showed systematically higher offsets (0.6 cm/s and 1.8 cm/s, respectively) than transverse aortic slices.

Conclusions:

• Current CMR systems lack a universal protocol for acceptable flow offset values.
• Protocol optimization must be performed on a per-scanner and per-protocol basis.
• Accurate transverse aortic flow quantification may be achievable with optimization, but pulmonary flow requires further offline correction.