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Contrast-to-noise ratio of multiple slice spin lock technique: prospects for liver imaging
J Halavaara1, S Lukkarinen, R Sepponen
1Jorvi Hospital, Department of Radiology, Turuntie 150, 02740 Espoo, Helsinki University of Technology, Helsinki, Finland.
Abstract:
Spin lock (SL) MRI technique has been demonstrated to provide similar lesion/liver contrast to conventional MR technique. Multiple slice SL technique allows a large number of slices to be collected within a given repetition time due to the short echo time. In addition, the short echo time reduces movement and susceptibility artefacts. In the present study, the potential of the multiple slice SL technique in liver imaging was evaluated by using tissue nuclear magnetic resonance (NMR) information and tissue NMR parameters obtained at 0.1 T. 10 healthy volunteers were imaged at 0.1 T for the measurement of tissue T1rho, T1, and T2 relaxation times. Tissue radiofrequency-attenuation information was obtained from the literature, and included in the contrast-to-noise ratio (CNR) calculations. Our results demonstrated that by increasing the number of slices the acquired liver-to-spleen CNR decreases with all locking field durations (locking time, TL). However, with small TLs, the difference is small which is important for liver MRI where a wide coverage, i.e. large number of slices, is important. Long locking pulse durations are more favourable than short TLs if large flip angles are used. With an optimal combination of a moderate amount of slices, reasonably large flip angle, and TL of the order of 20 ms, high CNR is achieved in SL MRI.
Insights
The multiple slice spin lock (SL) MRI technique offers good liver imaging contrast. Optimizing slice number, flip angle, and locking time (TL) maximizes liver-to-spleen contrast-to-noise ratio (CNR) for better visualization.
Area of Science:
- Magnetic Resonance Imaging (MRI)
- Medical Physics
- Radiology
Background:
- Spin lock (SL) MRI provides contrast comparable to conventional MRI techniques for liver imaging.
- The multiple slice SL technique enables rapid data acquisition with reduced motion and susceptibility artifacts due to its short echo time.
Purpose of the Study:
- To evaluate the potential of the multiple slice SL technique for liver imaging at 0.1 Tesla.
- To determine optimal parameters for maximizing liver-to-spleen contrast-to-noise ratio (CNR) using SL MRI.
Main Methods:
- Tissue nuclear magnetic resonance (NMR) information and parameters (T1rho, T1, T2 relaxation times) were measured in 10 healthy volunteers at 0.1 T.
- Liver-to-spleen CNR was calculated using tissue NMR data and literature-derived radiofrequency-attenuation information.
- The effect of varying the number of slices and locking time (TL) on CNR was investigated.
Main Results:
- Increasing the number of slices decreased liver-to-spleen CNR across all locking field durations (TL).
- Minimal CNR difference was observed with small TLs, which is advantageous for achieving wide coverage in liver MRI.
- Higher CNR was achieved with an optimal combination of moderate slices, large flip angle, and TL around 20 ms.
Conclusions:
- The multiple slice SL MRI technique is a viable option for liver imaging, offering good contrast and reduced artifacts.
- Parameter optimization, specifically balancing the number of slices with flip angle and locking time (TL), is crucial for achieving high liver-to-spleen CNR.
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