- Meeting abstract
- Open Access
2114 Temporal stability of the background velocity error shows potential for automated correction of regurgitant and shunt flow measurements
© Gatehouse et al; licensee BioMed Central Ltd. 2008
- Published: 22 October 2008
- Sequence Parameter
- Pulmonary Trunk
- Velocity Image
- Shunt Flow
- Background Error
It is well-known that velocity images can show a background offset in stationary tissue. Although the offset is reduced after correcting concomitant gradients, it has recently been shown  that applications such as the assessment of regurgitation or shunt flow are extremely sensitive to the residual error. The background offset usually varies across the image and is hard to predict, being dependent on numerous sequence parameters. Background errors even smaller than 1% of the VENC can seriously affect measurements of regurgitant fraction. Correction depends on obtaining a background error image for subtraction from the in-vivo velocity image. Accuracy is improved by velocity imaging of a stationary phantom acquired with identical sequence parameters after the patient scan . However, this procedure may be impracticable for clinical work.
This abstract therefore investigates the feasibility of using corrections acquired once after service recalibration, where the correction image nearest to that of the patient is used to remove the error. We present work on two main difficulties with the stored-corrections idea: First, the set would require thousands of images, covering all angles, slice offsets, inplane rotations, slice thicknesses, spatial and temporal resolutions, VENCs etc.; impracticable to acquire, so its size must be reduced as proposed below. Second, it assumes that the background error is stable over time.
To improve accuracy of flow MRI by automatic correction using stored background velocity errors. Fundamental to this idea, we first assess how stable is the background offset error in velocity images over a period of several weeks.
The stability of the background error over 40 days has been demonstrated. We are not aware that this has been shown before. It supports the possible use of a stored set of background corrections for improved accuracy of regurgitant and shunt flow measurements.