- Workshop presentation
- Open Access
Longitudinal stability of gel T1 MRI Phantoms for quality assurance of T1 mapping
© Vassiliou et al; licensee BioMed Central Ltd. 2015
- Published: 3 February 2015
- Automatic Adjustment
- Native Blood
- Extracellular Volume Fraction
- Biomedical Research Unit
- Native Myocardium
Quantification of interstitial (diffuse) myocardial fibrosis by T1 mapping may prove useful in a range of conditions. Both native T1 maps and extracellular volume fraction (ECV) are being increasingly used clinically and have been shown to be sensitive to a wide range of conditions and associate with worse prognosis. However, quality control by T1 phantoms is essential [1, 2] and their long-term stability has not been demonstrated. Phantoms with long term stability could assure the stability of methods applied to patients against scanner alternations and across multiple centers. We sought to investigate the long-term stability of phantoms prepared to model T1 and T2 of blood and myocardium over a period of 52 weeks.
NiCl2-agarose gel phantoms  were prepared in a standardised lab following a reproducible procedure to model T1 and T2 of blood and myocardium, native and post-contrast . Phantoms were 60ml glass narrow-neck sealed thick-wall bottles, filled with minimal gaps from gel contraction whilst cooling. These were kept in a temperature controlled MRI room and imaged weekly for 52 consecutive weeks (Siemens, Avanto, 1.5T) using consistent coil and phantom arrangement with a 11-RR MOLLI prototype (Siemens WIP448B) with high resolution (for heart rate 75bpm) and low resolution (for heart rate 100bpm) versions, with pre-contrast and post-contrast variants (4) plus spin-echo T2. Image parameters were identical weekly except for automatic adjustments of flip-angle and reference frequency. T1 and T2 values were taken as mean values in each phantom in pixel-wise maps.
showing the variability during a 52 week period of the Phantom T1 and T2 values and ECV using an 11-cycle 8-image prototype MOLLI. There were 2 phantoms for each T1 and T2 value prepared in standardised laboratory and the value used here represents the average of the two. The phantom ECV was calculated using a hematocrit of 0.43.
High Resolution (75bpm)
Low resolution (100bpm)
Post Gd Myocardium
Post Gd Blood
There was significant stability of the NiCl2-agarose gel phantoms over a one year period, justifying their routine use in clinical practice to support T1 mapping. Having determined stability, detection of parameters that could lead to phantom value inaccuracies (e.g. heart rate, flip angle and temperature variation) may require further investigation.
NIHR Cardiovascular Biomedical Research Unit of Royal Brompton & Harefield NHS Foundation Trust and Imperial College London.
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