Table 1:

Comparison of MR venography techniques.^[16,21]

	TOF-MRV	PC-MRV	CE-MRV
Principle	Flow enhancement	Phase shift	T1 shortening
Sequence	Gradient echo-based	Gradient echo-based	Gradient echo-based
Gadolinium	No	No	Yes
Acquisition time	5–8 min	>15 min*	Approx. 4 min
Background	Partly suppressed	Suppressed	Enhancing lesions seen
Factors for accuracy	Saturation of exogenous signal (arteries)	Operator for selection of appropriate VENC	Scan timing for maximum venous enhancement
Flow velocity	Can detect slow flow	Depends on the VENC	Independent
Flow direction	Not detected	Detected	Not detected
Flow quantification	No	Yes	No

^*Long acquisition time of PC-MRV is due to three gradient directions used to detect flowing spins in all directions. Acquisition time has now been reduced with the help of parallel imaging techniques refer [Table 2].^[16,17] TOF-MRV: Time-of-flight magnetic resonance venography, PC-MRV: Phase-contrast magnetic resonance venography, CE-MRV: Contrast-enhanced magnetic resonance venography, VENC: Velocity encoding gradient