SNR dependence on hardware installation and patient immobilization in fMRI examinations. MR imaging protocol optimization

Abstract

Introduction The primary form of fMRI uses the blood-oxygen-level dependent (BOLD) contrast imaging. In BOLD fMRI imaging, the signal-to-noise ratio (SNR) is extremely low and statistical methods are used to extract quantitative data. SNR of the images obtained has to be maintained as high as possible. Purpose The aim of this study is to estimate the SNR dependence on the video and audio device hardware as well as the patient immobilization in event related functional MRI examinations. Materials and methods A head mimicking phantom printed on a commercial 3D printer was scanned on a clinical 1.5 T whole-body clinical scanner utilizing a standard fMRI sequence protocol. Both anatomical and functional MR sequences were used for data acquisition. SNR parametric maps were produced and were fused on both anatomical and functional MR images obtained. The phantom was scanned before and after the installation of all the fMRI stimulus devices (visual and audio). Further examination conditions referring to immobilization of the phantom and cable looping were also studied separately. Results SNR is reduced down to 30% when the hardware cables were looped. Immobilization of the head mimicking phantom affected SNR by reducing its value to a level of 10%. The whole fMRI hardware installation also affected SNR with discrepancies at a level of 10%. Conclusion The fMRI hardware pre-installation and patient immobilization are important factors that have to be taken into consideration before performing an fMRI examination, as they can both affect the already extremely low SNR of the obtained images.