"The earliest method that is used to image the blood vessels is by exploiting the inflow effect of the blood, also known as "time-of-flight" (TOF). The inflow effect is due to differential exposure of the stationary tissue and inflowing blood to radiofrequency (RF) excitations. Stationary tissue is repeatedly exposed to RF pulse, thus causing its longitudinal magnetisation to reach approximately zero (Mz=0), producing no signal. Meanwhile, inflowing blood are not exposed to RF pulse, causing it to express full longitudinal magnetisation of (Mz=1), thus producing detectable signal. The signal intensity of the flowing blood depends on blood velocity, repetition time (TR), and cross-sectional area of the blood vessel. The faster the blood velocity relative to the TR, the higher the signal of the blood. In slow-flowing blood where parts of the blood are fully saturated and the other parts are unsaturated, the signal of the blood depends upon the flip-angle and T1 relaxation time of the blood. The addition of gadolinium into the blood (as in contrast-enhanced MR angiography) will reduce the T1 relaxation time, thus increasing the signal of the slow-flowing blood 5."
"The earliest method that is used to image the blood vessels is by exploiting the inflow effect of the blood, also known as "time-of-flight" (TOF). The inflow effect is due to differential exposure of the stationary tissue and inflowing blood to radiofrequency (RF) excitations. Stationary tissue is repeatedly exposed to RF pulse, thus causing its longitudinal magnetisation to reach approximately zero (Mz=0), producing no signal. Meanwhile, inflowing blood are not exposed to RF pulse, causing it to express full longitudinal magnetisation of (Mz=1), thus producing detectable signal. The signal intensity of the flowing blood depends on blood velocity, repetition time (TR), and cross-sectional area of the blood vessel. The faster the blood velocity relative to the TR, the higher the signal of the blood. In slow-flowing blood where parts of the blood are fully saturated and the other parts are unsaturated, the signal of the blood depends upon the flip-angle and T1 relaxation time of the blood. The addition of gadolinium into the blood (as in contrast-enhanced MR angiography) will reduce the T1 relaxation time, thus increasing the signal of the slow-flowing blood 5."
"The earliest method that is used to image the blood vessels is by exploiting the inflow effect of the blood, also known as "time-of-flight" (TOF). The inflow effect is due to differential exposure of the stationary tissue and inflowing blood to radiofrequency (RF) excitations. Stationary tissue is repeatedly exposed to RF pulse, thus causing its longitudinal magnetisation to reach approximately zero (Mz=0), producing no signal. Meanwhile, inflowing blood are not exposed to RF pulse, causing it to express full longitudinal magnetisation of (Mz=1), thus producing detectable signal. The signal intensity of the flowing blood depends on blood velocity, repetition time (TR), and cross-sectional area of the blood vessel. The faster the blood velocity relative to the TR, the higher the signal of the blood. In slow-flowing blood where parts of the blood are fully saturated and the other parts are unsaturated, the signal of the blood depends upon the flip-angle and T1 relaxation time of the blood. The addition of gadolinium into the blood (as in contrast-enhanced MR angiography) will reduce the T1 relaxation time, thus increasing the signal of the slow-flowing blood 5."
"time of flight angiography (TOF)"
"cardiac-gated 3D fast spin-echo (3D FSE or fresh blood imaging) 3"
"TOF is used to assess arteries of the head and neck"
"subtractive FSE and QISS can be used in peripheral arteries"
"Subtractive 3D MRA"
Expected headings
"Techniques"
"Types"
"Applications"
"The earliest method that is used to image the blood vessels is by exploiting the inflow effect of the blood, also known as "time-of-flight" (TOF). The inflow effect is due to differential exposure of the stationary tissue and inflowing blood to radiofrequency (RF) excitations. Stationary tissue is repeatedly exposed to RF pulse, thus causing its longitudinal magnetisation to reach approximately zero (Mz=0), producing no signal. Meanwhile, inflowing blood are not exposed to RF pulse, causing it to express full longitudinal magnetisation of (Mz=1), thus producing detectable signal. The signal intensity of the flowing blood depends on blood velocity, repetition time (TR), and cross-sectional area of the blood vessel. The faster the blood velocity relative to the TR, the higher the signal of the blood. In slow-flowing blood where parts of the blood are fully saturated and the other parts are unsaturated, the signal of the blood depends upon the flip-angle and T1 relaxation time of the blood. The addition of gadolinium into the blood (as in contrast-enhanced MR angiography) will reduce the T1 relaxation time, thus increasing the signal of the slow-flowing blood 5."