- Technologist presentation
- Open Access
How to measure vessel flow with CMR phase contrast imaging
© Lawton et al; licensee BioMed Central Ltd. 2015
- Published: 3 February 2015
- Peak Velocity
- Breath Hold
- Cine Image
- Measure Blood Flow
- Free Breathing
Accurately measuring blood flow with CMR is paramount in patients with valvular disease. These flow measurements are important components of a CMR report and provide the referring clinicians with valuable information in which to base further clinical management. This poster presents a guide on how to measure blood flow accurately based on our experience at the Bristol Heart Institute.
Velocity Encoding (Venc.) matching
The velocity encoding (Venc) range should be chosen to match the peak velocity as closely as possible. If the Venc is too high the image will become noisy with high background error, too low, and an artefact known as aliasing will corrupt the measurement flow data, rendering it un-diagnostic. To ensure the Venc is matched correctly, run a flow scout sequences at 4 different Venc settings [Fig 3]. Alternatively start with a low Venc, if there is aliasing repeat in steps of 50 until it disappears.
Free Breathing & Breath hold flows
Free breathing flow offers higher temporal and spatial resolution than a breath hold flow as a greater number of heart beats are used to acquire the data. As it is also measured over multiple respiratory and cardiac cycles it would appear to be the method of choice to measure arterial valve function. However when there is turbulent flow or when peak velocity estimation is required it can produce misleading data. In this situation a stack of breath hold flows across the valve can be employed. This optimises slice position for peak velocity and peak flow measurement.
No results as this is a reference poster.
Accurate positioning of the slice and selecting the correct velocity encoding are paramount steps when measuring blood flow. Due care and diligence needs to be shown to achieve accurate results.
National Institute for Health Research, Biomedical Research Unit.
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