Cargando…
Accuracy and precision of electrical permittivity mapping at 3T: the impact of three [Formula: see text] mapping techniques
PURPOSE: To investigate the sequence‐specific impact of [Formula: see text] amplitude mapping on the accuracy and precision of permittivity reconstruction at 3T in the pelvic region. METHODS: [Formula: see text] maps obtained with actual flip angle imaging (AFI), Bloch–Siegert (BS), and dual refocus...
Autores principales: | , , , , , , , |
---|---|
Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2019
|
Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6593818/ https://www.ncbi.nlm.nih.gov/pubmed/30737816 http://dx.doi.org/10.1002/mrm.27675 |
Sumario: | PURPOSE: To investigate the sequence‐specific impact of [Formula: see text] amplitude mapping on the accuracy and precision of permittivity reconstruction at 3T in the pelvic region. METHODS: [Formula: see text] maps obtained with actual flip angle imaging (AFI), Bloch–Siegert (BS), and dual refocusing echo acquisition mode (DREAM) sequences, set to a clinically feasible scan time of 5 minutes, were compared in terms of accuracy and precision with electromagnetic and Bloch simulations and MR measurements. Permittivity maps were reconstructed based on these [Formula: see text] maps with Helmholtz‐based electrical properties tomography. Accuracy and precision in permittivity were assessed. A 2‐compartment phantom with properties and size similar to the human pelvis was used for both simulations and measurements. Measurements were also performed on a female volunteer’s pelvis. RESULTS: Accuracy was evaluated with noiseless simulations on the phantom. The maximum [Formula: see text] bias relative to the true [Formula: see text] distribution was 1% for AFI and BS and 6% to 15% for DREAM. This caused an average permittivity bias relative to the true permittivity of 7% to 20% for AFI and BS and 12% to 35% for DREAM. Precision was assessed in MR experiments. The lowest standard deviation in permittivity, found in the phantom for BS, measured 22.4 relative units and corresponded to a standard deviation in [Formula: see text] of 0.2% of the [Formula: see text] average value. As regards [Formula: see text] precision, in vivo and phantom measurements were comparable. CONCLUSIONS: Our simulation framework quantitatively predicts the different impact of [Formula: see text] mapping techniques on permittivity reconstruction and shows high sensitivity of permittivity reconstructions to sequence‐specific bias and noise perturbation in the [Formula: see text] map. These findings are supported by the experimental results. |
---|