Visualization of bile movement using MRI spin-labeling technique: preliminary results.

OBJECTIVE: The purpose of this article is to noninvasively visualize intrabiliary bile movement using an MRI spin-labeling technique and administration of water, full-fat milk, and negative contrast agent as stimuli for bile excretion. SUBJECTS AND METHODS: Six healthy volunteers underwent three studies with each of three oral liquid agents (water, full-fat milk, and manganese chloride solution) for a total of 18 MRI studies. Oblique-coronal T2-weighted images of the common bile duct were acquired at an inversion time of 1500 milliseconds after pulse labeling using a spin-labeling technique with an inversion pulse, repeated at intervals of 22 seconds. Bile flow rate was measured before and for 50 minutes after administration of the oral liquid agents, and its correlation with the change in gallbladder volume was assessed. RESULTS: Both anterograde and retrograde intermittent bile movements were successfully visualized in the common bile duct. The summation of excreted bile volume calculated from spin-labeled images correlated significantly with a decrease in gallbladder volume (p = 0.011). Milk stimulated significantly prolonged bile flow; flow was momentary with manganese chloride and mild with water; however, gallbladder volume decreased only in milk studies (p = 0.003). Biliary flow early after oral intake correlated significantly with gallbladder contractility at 50 minutes after oral intake (p = 0.049). CONCLUSION: A new method for visualizing intrabiliary bile movement in semi-real time (22-second time resolution) using an MRI spin-labeling technique was proposed. Bile was shown to be excreted in a to-and-fro type of movement. Administration of water and negative contrast agent may induce temporary bile excretion.

Whole-heart 3D late gadolinium-enhanced MR imaging: investigation of optimal scan parameters and clinical usefulness.

PURPOSE: Whole-heart 3-dimensional (3D) late-gadolinium-enhanced magnetic resonance (MR) imaging (WH-LGE) uses respiratory gating combined with acquisition of 3D data for the entire heart in a single scan, which permits reconstruction of any plane with high resolution. We investigated the optimal scan parameters and compared WH-LGE with the conventional scanning method. MATERIALS AND METHODS: We employed inversion recovery 3D fast field echo using a 1.5-tesla system and scan parameters: repetition time (TR), 6.6 ms; echo time (TE), 2.5 ms; number of segments, 2; parallel imaging factor, 1.8; matrix size, 128 × 256; field of view (FOV), 320 × 320 mm; and acquisition slice thickness, 3 mm (reconstruction slice thickness, 1.5 mm). Five healthy volunteers underwent scanning during free breathing with real-time motion correction, from which we determined optimal scan parameters. We then used those parameters to scan 25 patients with myocardial infarction to compare scan time and image quality between the WH-LGE and conventional 3D breath-holding methods (slice thickness, 10 mm; matrix size, 128 × 256). RESULTS: Results in volunteers showed optimal scan parameters of 12° flip angle, fat suppression turned off in combination, and interleaved ordering. In clinical cases, scan times did not differ significantly. Sharpness of the margins of normal myocardium at the apex of the heart and contrast between enhanced and nonenhanced myocardium improved significantly with WH-LGE. CONCLUSION: WH-LGE yields high resolution images during free breathing and is considered useful for accurately estimating the area and transmural extent of myocardial infarction.

Time-resolved three-dimensional magnetic resonance digital subtraction angiography without contrast material in the brain: Initial investigation.

PURPOSE: To evaluate a novel magnetic resonance (MR) angiography (MRA) of three-dimensional (3D) MR digital subtraction angiography (MRDSA) without contrast material, which is essentially 3D true steady-state free precession (SSFP) with selected inversion recovery (IR) pulse using multiple cardiac phase acquisitions with a short increment delay in the assessment of normal cranial arteries, as a feasibility study before clinical use. MATERIALS AND METHODS: Serial MRA images using 3D MRDSA without contrast material were acquired from 10 healthy volunteers. Visualization of normal cranial arteries with time-spatial labeling inversion pulse (Time-SLIP) MRDSA was qualitatively compared with the conventional MRA method, 3D time-of-flight (TOF)-MRA. RESULTS: In all volunteers, serial 3D MRDSAs containing hemodynamic information were successfully imaged. The results of visualization of the branches of the cranial arteries with Time-SLIP MRDSA were comparable to those of 3D TOF-MRA. The mean scores +/- standard deviations for normal cerebral arteries (internal carotid arteries, middle cerebral arteries, anterior cerebral arteries, posterior cerebral arteries, and basilar arteries) were 2.4 +/- 0.5, 2.3 +/- 0.5, 2.0 +/- 0.7, 2.3 +/- 0.7, and 2.5 +/- 0.7, respectively. CONCLUSION: Time-SLIP 3D MRDSA is a simple method for obtaining hemodynamic information. Although more MR sequence improvement is needed, it can play an important role in assessing cranial arteries without contrast material.