- SIGNA MR355 / SIGNA MR360
- Service Manual
- 5856356-3EN Revision 5.0
- Basic Service Documentation. Copyright General Electric Company.
- 00000018WIA3019CF20GYZ
- id_131075261.1
- Jul 5, 2019 10:25:10 PM
Signal To Noise Check
This document details the procedure for checking body, head and surface coil signal-to-noise values.
Proprietary procedures (SPT and TLT) are available for GE use and to customers with a valid Advanced Service Package Limited License. For Head and Body, refer to SPT Full Test Mode procedure. For Surface Coils, refer to the TLT procedure.
In this measurement, two back-to-back scans are performed. The SNR Tool uses an ROI that covers 80% of the phantom image, and measures a mean pixel value minus 1024. The result is the signal value. The two images are then subtracted to obtain the noise image. The 80% ROI is placed on the noise image and the standard deviation, divided by the square root of two, is the noise value. The signal-to-noise ratio (SNR) is the signal divided by the noise. No image artifacts are allowed in any SNR scan.
SNR reflects primarily the state of the RF sub-system of the scanner, but as the gradients are used to spatially isolate the slice/volume, it can be used to check for comparative performance between the different gradient coils. It is important to use the same GradMode throughout any test section.
Signal To Noise Check consist of three individual component scans followed by analysis.