Scan parameter trade-offs

Table 1. Scan parameter trade-offs
Scan Parameter	SNR	Spatial Resolution	Scan Time	T1 contrast	PD Contrast	T2 Contrast
As TR increases	Increases	Not applicable	Increases	Decreases	Increases	Increases
As TE increases	Decreases	Not applicable	Not applicable	Decreases	Decreases	Increases
As RBw increases	Decreases	Not applicable	Not applicable	Increases	Increases	Not applicable
As ETL increases	Not applicable	Not applicable	Decreases	Decreases	Decreases	Increases
As Frequency increases	Decreases	Increases	Not applicable	Decreases	Not applicable	Not applicable
As Phase increases (sq pixel)	Increases	Not applicable	Increases	Contrast is directly affected by scan timing parameters (TR, TE, TI and flip angle). The SNR can enhance or obscure contrast, but it cannot change the image weighting from one type of contrast to another.
As Phase increases (rect pixels)	Decreases	Increases	Increases
As NEX increases	Increases	Not applicable	Increases
As FOV increases	Increases	Decreases	Not applicable
As Slice Thickness increases	Increases	Decreases	Not applicable
As Spacing increases	Increases	Not applicable	Not applicable