Dynamic 3d liver contrast scan technique

3D Dynamic Gd (FAME)

On older scanners this was performed as out-of-phase 2D FMPSPGR with fat saturation to eliminate artifact at fat-organ boundaries. On state-of-art scanners, 3D provides higher resolution and allows zero filling (ZIP2) for overlapping reconstruction of slices. Repeat the scan multiple times with breath holding as follows:

·        Pre-contrast fat-saturated 3D volume images are obtained. These provide T1-weighted information.

·        Begin to administer 0.1-0.2 mmol/kg dose of Gd contrast (typically 30 ml) at a rate of 3 ml/s, and set the fluoro-triggering to detect to contrast arrival. Operator may visually follow the contrast travel through the right heart, pulmonary arteries, ascending aorta and finally descending aorta. Triggering the scan should be done when the contrast arrives to proximal segment of abdominal aorta (diaphragmatic level). As soon as the operator observes the contrast arrival, instructs the patient to hold his/her breath at the end of inspiration, and triggers the sequence. There is a 5 s delay between triggering and the beginning of actual acquisition for breathe holding instructions.

·        Gd injection is followed by 20 ml of saline flush at a rate of 3 ml/s.

·        The first acquisition is timed for arterial enhancement. Same acquisition is performed subsequently multiple times in quick succession (10 seconds between each to allow patients to catch their breath) to acquire the portal, hepatic venous, and equilibrium phases. The scan may be repeated as much as desired. Delayed phase imaging: If the liver is cirrhotic, a delay of 3 minutes is adequate. If there is a suspicious lesion that might be hemangioma or cholangiocarcinoma, then repeat scan every 2-3 minutes out to 10 minutes. Cholangiocarcinoma is known to enhance late.

·        A chemically selective fat-saturation pulse is applied just before each partitions loop. In the saturation pulse area, choose the ‘special’. The partitions loop is centric reordered to optimize fat-saturation uniformity.

·        Zero-filling interpolation can reduce partial volume artifacts on 3D MR angiograms.

·        The 3D volumetric imaging technique is a modified MRA sequence. The operator, by using “IVI” option and MIP algorithms on the scanner or Windows Advantage work station can obtain reconstructions of the arterial territories.

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