High-resolution fMRI: Overcoming the signal-to-noise problem

- Poor Stars . Viii . High - Resolution , High - Signal - to - Noise Analysis

High-resolution, high-signal-to-noise (〈S/N〉 = 85) spectra have been obtained for five stars – CD–2417504, CD–38245, CS 22172–002, CS 22885–096, and CS 22949–037 – having [Fe/H] . –3.5 according to previous lower S/N material. LTE model-atmosphere techniques are used to determine [Fe/H] and relative abundances, or their limits, for some 18 elements, and to constrain more tightly the early enric...

On the Definition of Signal-To-Noise Ratio and Contrast-To-Noise Ratio for fMRI Data

Signal-to-noise ratio, the ratio between signal and noise, is a quantity that has been well established for MRI data but is still subject of ongoing debate and confusion when it comes to fMRI data. fMRI data are characterised by small activation fluctuations in a background of noise. Depending on how the signal of interest and the noise are identified, signal-to-noise ratio for fMRI data is rep...

On Signal to Noise Ratio Tradeoffs in fMRI

When planning an fMRI experiment, it is desirable to optimize the SNR to maximize the statistical return on scan time investment. At first glance, the tradeoffs may seem unclear. As more slices are acquired, the TR needed to fit in the slices increases linearly. With longer TR the flip angle and degree of magnetization recovery between pulses both increase, leading to higher signal. However, at...

Implantable Microsystems for High-Resolution Interfacing to the Brain

High Signal-to-Noise, Differential NICMOS Spectrophotometry

We report analysis for NICMOS CAL/9642, High S/N Capability Characterization.The purpose of this three orbit test was to establish NICMOS time domain stability in a domain not previously tested for NICMOS. Observations of the bright (H = 6.13) G0 V star HD 209458 were obtained using 1.8 second MULTIACCUMs with G141 on NIC3. Exposure-to-exposure stability summed over the full spectrum provides S...