RMS can be calibrated using either a full-scale square wave, or a sine wave. The correct way to do this for a music signal, as defined by AES Standard AES17-1998, is to use a sine wave peaking at 0dBFS - for more details, click here.
Wavelab 7 full 17
Images of a healthy volunteer obtained with DIR-RADFSE. (A) The TE images are reconstructed from undersampled data sets (16 radial views per TE) using the ES and the CURLIE algorithms. (B) The anatomical image, reconstructed by filtered back-projection using the full k-space data set (all 256 radial views), and a colorized T2 map of the left ventricle myocardium overlaid on the anatomical image are displayed for both algorithms. The anatomical image, TE images and T2 maps are generated from the same k-space data (acquired in a single breath hold).
Images of a subject diagnosed with hypertrophic cardiomyopathy. (Top) Three out of the 16 TE images reconstructed from undersampled data sets (16 radial views per TE) using CURLIE. (Bottom) The anatomical image, reconstructed by filtered back-projection using the full k-space data set (all 256 radial views), is shown on the lower left panel. The colorized T2 map of the left ventricle overlaid onto the anatomical image is displayed in the lower middle panel for CURLIE-SEPG. The LGE image is shown in the lower right panel.
Images of a patient with myocardial infarct scar. (Top) Three out of the 16 TE images reconstructed from undersampled data sets (16 radial views per TE) using CURLIE. (Bottom) The anatomical image, reconstructed by filtered back-projection using the full k-space data set (all 256 radial views), is shown on the lower left panel. The colorized T2 map of the left ventricle overlaid onto the anatomical image is displayed in the lower middle panel for CURLIE-SEPG. The LGE image is shown in the lower right panel.
The magnitude reconstruction used to obtain the TE images in the ES algorithm is also a source of T2 overestimation. Taking the magnitude of the data causes the noise distribution to become non-Gaussian (i.e. strictly positive) for data with low signal-to-noise ratio (SNR) [31]. Thus, for data at the latter TEs (where the SNR may be compromised) the magnitude operation artificially increases the signal intensity of these time points, which in turn yields higher T2 values. This is not specific to the ES algorithm but to every algorithm that is based on a magnitude reconstruction (note that we have used a magnitude operation for the reference spin-echo data, however the SNR of the reference scan was higher because the data was fully sampled). In contrast, the model-based CURLIE algorithm does not suffer from the problems associated with a magnitude reconstruction because the data fitting is done in k-space using complex data [20,24]. 2ff7e9595c
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