Aims and objectives
Conventional Magnetic Resonance Imaging (MRI) scanners allow patients to be imaged only in the supine position.
tilting MRI scanners allow to examine a subject also in the sitting position,
for Weight-Bearing (WB) MRI studies.
the last types of scanners have a lower magnetic field (typically between 0.2 T and 0.4 T),
with a consequent lower signal-to-noise ratio (SNR) . For what concerns brain neuroimaging,
a tilting MRI scanner might be used as a non-invasive tool for...
Methods and materials
Subject population: Two subjects (age 38 – subject 1 – and age 49 – subject 2 –,
males) underwent head MRI on a tilting 0.25 T system (GScan Brio,
Italy) and on a 1.5 T scanner (Magnetom Avanto,
Germany). Data acquisition: An isotropic (resolution 1 × 1 × 1 mm 3 ) high-resolution T1-weighted 3D image,
using a magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequence,
was acquired on both scanners in the supine position.
The sequence parameters for 0.25 T...
The 3D T1 images obtained for the two subjects with the two scanners in the supine position are reported in Figure 1.
The 3D T1 images of Subject 2 in the supine and sitting position at 0.25 T are shown in Figure 2. Tissue segmentation and volumes The performance of the GM segmentation obtained with the two scanners is shown in Figure 3,
where the GM obtained at 0.25 T was coregistered and superimposed to the GM obtained at 1.5 T. The differences between the corresponding volumes obtained at...
Cortical and subcortical GM volumes were underestimated (range 0.1-10.3%) and WM volume was overestimated (range 1.3-4.8%) by 0.25 T compared to 1.5 T,
likely because parts of the cortical GM were misclassified as WM (as shown in Figure 3). The differences of tissue volumes computed using different scanners and positions,
although higher than the repeatability at 1.5 T,
were in line with the repeatability reported in a specific study using a 3 T scanner . Since SNR is directly dependent on...
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