✦ LIBER ✦

Improved Resolution and Signal-to-Noise Ratio in MRI via Enhanced Signal Digitization

✍ Scribed by Mark A. Elliott; Erik K. Insko; Robert L. Greenman; John S. Leigh

Publisher: Elsevier Science
Year: 1998
Tongue: English
Weight: 198 KB
Volume: 130
Category: Article
ISSN: 1090-7807
DOI: 10.1006/jmre.1997.1319

No coin nor oath required. For personal study only.

✦ Synopsis

The high frequency k-space data in magnetic resonance imaging clinical field strengths of 1.5 T, 3D proton MRI of large is often poorly reproduced due to the finite dynamic range of an volumes can have k-space signal-to-noise ratios which exanalog-to-digital converter. The magnitude of this digitization erceed this limit. For example, a 256 1 128 1 32 image with ror can equal and even exceed the magnitude of the thermal noise. an average SNR in each voxel of 100-to-1 will have an Under such conditions, attempts to increase image signal-to-noise observable dynamic range in k-space of approximately 10 5ratio via signal averaging meet with diminishing success. Because to-1. Under such conditions, the noise amplitude is, on averthe relative size of the digitization error increases at higher spatial age, less than 1 bit. The effective SNR is now set by the frequencies, a reduction in image resolution is incurred as well.

resolution of the ADC, and attempts to increase the SNR By adjusting the level of the analog signal sampled by the analogthrough signal averaging will yield limited results.

to-digital converter during the course of an imaging experiment,

The limitation on image quality imposed by the resolving the magnitude of the digitization artifact can be greatly reduced.

The results of simulations and imaging experiments are presented power of the ADC was first recognized by Maudsley (1) which demonstrate that this strategy improves both the signal-toand Wedeen et al. (2), who proposed to reduce the dynamic noise ratio and resolution of magnetic resonance images. ᭧ 1998 range of the k-space signal by phase-scrambling with RF Academic Press pulses and nonlinear gradients, respectively. Modifications

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