Comparison of the Timing of Hepatic Arterial Phase and Image Quality Using Test-Bolus and Bolus-Tracking Techniques in Gadolinium–Ethoxybenzyl–Diethylenetriamine Pentaacetic Acid–Enhanced Hepatic Dynamic Magnetic Resonance Imaging

Abstract

ObjectivesThe aim of this study was to compare the image quality, the degree of artifacts and the percentage of timing of the optimal hepatic arterial phase (HAP) between test-bolus and bolus-tracking methods on gadolinium–ethoxybenzyl–diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)–enhanced magnetic resonance imaging (MRI).MethodsIn this prospective study, 60 patients who underwent 3-dimensional dynamic Gd-EOB-DTPA–enhanced hepatic 3-T MRI were enrolled in this study. We randomly assigned the 30 patients to the bolus-tracking method, and another 30 patients to the test-bolus method. Signal-to-noise ratios of the liver and spleen in HAP were compared in the 2 groups. Two radiologists independently assessed the ratio of optimal timing of HAP and the degree of ringing and motion artifacts of the 2 protocols.ResultsThe signal-to-noise ratios of the liver (24.0 [SD, 6.4] vs 20.4 [SD, 4.0]) and spleen (30.0 [SD, 13.3] vs 23.6 [SD, 9.9]) were significantly higher in the test-bolus protocol than in the bolus-tracking protocol. The ratio of optimal timing was also significantly higher with the test-bolus protocol than with the bolus-tracking protocol (76.7% vs 40.0%). The degree of ringing and motion artifacts of test-bolus protocol was significantly lower than that of the bolus-tracking protocol (P < 0.01).ConclusionsThe test-bolus protocol in dynamic 3-T MRI can yield better qualitative image quality and more optimal timing of HAP images, while reducing the degree of artifacts compared with the bolus-tracking protocol.

Pitfalls in liver MRI: Technical approach to avoiding misdiagnosis and improving image quality

“…Given the importance of appropriate timing, different techniques have been employed to acquire an optimal late arterial phase. The simplest technique is a fixed or empiric delay, ranging from 20–30 seconds after the start of the injection . However, this method can often lead to suboptimal outcomes because it does not account for variability in cardiac output, venous capacity, injection rate or volume, or other variables …”

“…In this method, a small dose of gadolinium chelate contrast (typically 1–2 ml) is injected at the desired rate followed by a saline flush to determine the time to peak aortic enhancement (TTP). This is achieved by applying a single transverse high temporal resolution T 1 ‐w spoiled gradient‐recalled‐echo (SPGR) sequence through the aorta at approximately the level of the celiac axis following the test bolus injection . Spatial saturation preparatory pulses are applied above the slice location to eliminate inflow time‐of‐flight flow‐related enhancement, which can mimic contrast enhancement.…”

“…Spatial saturation preparatory pulses are applied above the slice location to eliminate inflow time‐of‐flight flow‐related enhancement, which can mimic contrast enhancement. TTP is qualitatively determined by the technologist or radiologist, and it is then used to calculate the optimal delay for the arterial phase using the following equation …”

“…Familiarity with the specific k ‐space acquisition method for each platform is required for optimum timing. There are a number of variants of the above equation described in the literature …”

“…The simplest technique is a fixed or empiric delay, ranging from 20-30 seconds after the start of the injection. 3,[9][10][11] However, this method can often lead to suboptimal outcomes because it does not account for variability in cardiac output, venous capacity, injection rate or volume, or other variables. 3,8 Methods more tailored to individual patient factors are recommended over a fixed or empiric delay.…”