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library:bandwidth [2025/03/31 19:50] – scottlibrary:bandwidth [2025/03/31 20:18] (current) – scott
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   * Bandwidth is reported as Hz/Pixel; hold the mouse over the drop down menu to see the # of pixels chemical shift    * Bandwidth is reported as Hz/Pixel; hold the mouse over the drop down menu to see the # of pixels chemical shift 
-  * Fat and water are ~220 Hz apart at 1.5T; try to keep the Hz/Pixel near 220, or # of pixel chemical shift close to 1-1.3  +  * Fat and water are ~220 Hz apart at 1.5T; try to keep the Hz/Pixel in 150-220, or # of pixel chemical shift close to 1-1.5  
-  * Keep in mind how large the pixels are when adjusting FOV and Matrix, as the Hz/pixel will stay constant. Big pixels = larger artifacts+  * Keep in mind how large the pixels are when adjusting FOV and Matrix, as the Hz/pixel will stay constant. Big pixels = big artifacts
  
 ====Bandwidth in Practice==== ====Bandwidth in Practice====
    
-Below are several examples of how different bandwidths a affect image quality. 
  
 {{:library:rbwchemshift_8_.gif|}} {{:library:rbwchemshift_8_.gif|}}
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 {{:library:rbw_10-63khz_10_.gif|}} {{:library:rbw_10-63khz_10_.gif|}}
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 +The images above are of an Axial T2 weighted FSE, with the bandwidth increased from 10 kHz to 63 kHz. Notice that the first low bandwidth (10 kHz) result in quite a blurry image; the echo spacing is long and the chemical shift artifact  is significant. As bandwidth is increased, note how the morphology of the extruded disc appears to change. Also note that the 'bulk' of the patient appears to move within the image; this is the effect of chemical shift across the entire image. Once the 63 kHz bandwidth is reached, the SNR is poor and zipper artifacts appear in the image.
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