Navigator-triggered prospective acquisition correction (PACE) technique vs. conventional respiratory-triggered technique for free-breathing 3D MRCP: an initial prospective comparative study using healthy volunteers.

PURPOSE: To confirm the superiority of the navigator-triggered prospective acquisition correction (PACE) technique over the conventional respiratory-triggered (RESP) technique, something that has been perceived experimentally but without definite evidence, for free-breathing three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) using healthy volunteers. MATERIALS AND METHODS: Free-breathing 3D turbo spin-echo MRCP using both PACE and RESP techniques were prospectively performed on 25 healthy volunteers. Quantitative analyses of acquisition time, signal-to-noise ratio, contrast-to-noise ratio, and contour sharpness index of each segment of the pancreaticobiliary tree were compared using the paired t-test. Qualitative analyses on a five-point scale (1, excellent; 5, poor) scored by two independent radiologists were compared using the Wilcoxon signed-rank test. RESULTS: The subjective image quality and contour sharpness index of each segment of the PACE technique were found to be significantly better than those for RESP (P<0.05). No significant difference was observed with regard to signal-to-noise and contrast-to-noise ratios except for the pancreatic duct. No significant difference in acquisition times between PACE and RESP techniques was observed. CONCLUSION: We confirmed the superiority of the image quality of the PACE technique compared to conventional RESP technique for free-breathing 3D MRCP in healthy volunteers.

Compression belt for navigator-triggered trueFISP whole-heart coronary magnetic resonance angiography: study in healthy volunteers.

PURPOSE: To evaluate in healthy volunteers the usefulness of an abdominal compression belt in reducing acquisition time by stabilizing respiratory motion during whole-heart coronary magnetic resonance angiography (WHCMRA) using conventional navigator triggering. METHODS: In 10 healthy volunteers, we performed free-breathing 3-dimensional segmented true fast imaging with steady-state precession (trueFISP) WHCMRA using conventional navigator triggering without motion-adapted gating. We acquired images with the abdominal compression belt rolled tightly around the upper abdomen and without the belt. We compared image acquisition time, navigator efficiency, and visible length of coronary arteries using paired t-test and subjective image quality on a 4-point scale (1, poor; 4, excellent) using Wilcoxon signed-rank test. RESULTS: There were no statistically significant differences for mean acquisition time (11.5+/-5.0 vs. 9.3+/-2.4 min, P=0.150); navigator efficiency (38.7+/-13.6 vs. 42.8+/-11.0%, P=0.336); mean overall visible length of the coronary arteries (99.7+/-22.7 vs. 105.0+/-16.5 mm, P=0.530); or mean overall subjective image quality (2.5 vs. 2.7, P=0.297) between results obtained with and without the abdominal compression belt. CONCLUSION: In this small group of healthy volunteers, the use of an abdominal compression belt did not reduce image acquisition time or improve image quality in trueFISP WHCMRA using conventional navigator triggering; however, the technique's feasibility requires additional consideration using other navigator-triggering methods for patients with irregular respiratory cycles.

Contrast changes in portal vein and bile duct between centric and linear k-space ordering on three-dimensional segmented true fast imaging with steady-state precession magnetic resonance imaging.

PURPOSE: To compare the degree of visualization of the bile duct and portal vein in terms of the difference in k-space ordering on a three-dimensional (3D) segmented true fast imaging with steady-state precession (trueFISP) sequence. MATERIALS AND METHODS: A breath-hold coronal 3D segmented trueFISP sequence was prospectively performed on 14 healthy volunteers. Images obtained with centric and linear k-space ordering in the k(x)-k(y) plane were compared by two independent radiologists qualitatively with depiction scores on a five-point scale (1=not seen to 5=excellent depiction) using the Wilcoxon signed-rank test. Images were also compared quantitatively using relative contrast values for the bile duct and portal vein against the hepatic parenchyma using a paired t-test. RESULTS: With centric ordering, both the mean depiction scores and relative contrast values for the portal vein were significantly lower than those with linear ordering (1.5 vs. 3.5, P<.01; and 0.08+/-0.19 vs. 0.51+/-0.10, P<.01, respectively). However, in the bile duct, there were no significant differences, only slight differences were found among the results obtained with centric and linear ordering (3.9 vs. 3.8, P=.72; and 0.59+/-0.06 vs. 0.68+/-0.06, P<.01, respectively). CONCLUSION: For visualizing the bile duct, centric k-space ordering on 3D segmented trueFISP sequence is recommended, while linear ordering is recommended for portal vein visualization.

Prospective trial of a navigator setting under left hepatic lobe on magnetic resonance cholangiopancreatography using a free-breathing prospective acquisition correction technique.

PURPOSE: To prospectively compare the image acquisition time and image quality obtained by navigator setting under the left hepatic lobe vs. on the right diaphragm on magnetic resonance cholangiopancreatography (MRCP) using a free-breathing navigator-triggered prospective acquisition correction technique (PACE). MATERIALS AND METHODS: Fifty consecutive patients prospectively underwent three-dimensional T2-weighted turbo spin-echo MRCP using PACE with the navigator randomly set either under the left hepatic lobe or on top of the right diaphragm. Image acquisition time and subjective image quality were compared on a five-point scale using Student's t-test and Mann-Whitney's U test, respectively. RESULTS: There was no significant difference for mean acquisition time (6.1+/-1.6 vs. 6.3+/-1.2 min, P=.689) between the left hepatic lobe group and right diaphragm group. Mean subjective image quality was significantly worse in the left hepatic lobe group than in the right diaphragm group (4.1 vs. 4.7, P=.044). CONCLUSION: Setting the navigator under the left hepatic lobe for MRCP using PACE causes the data processing to be more difficult. As well, under current circumstances, it does not contribute to reducing acquisition time or improving the image quality.

Frequency of common bile duct motion artifacts caused by inferior vena cava pulsation on magnetic resonance cholangiopancreatography.

PURPOSE: We assessed the frequency of common bile duct (CBD) motion artifacts caused by inferior vena cava (IVC) pulsation on magnetic resonance cholangiopancreatography (MRCP). METHODS: We retrospectively evaluated CBD motion artifacts in 4 MRCP sequences from each of 115 consecutive patients. RESULTS: We observed 37 (32.2%) ghost artifacts at the ventral and dorsal aspects of the CBD on transaxial, half-Fourier acquisition single-shot turbo spin-echo (HASTE-ax) images; no such artifacts were observed on transaxial T(2)-weighted turbo spin-echo images. In 10 patients, we observed 9 (7.8%) pseudo-defects of the CBD on 3-dimensional T(2)-weighted turbo spin-echo with navigator-triggered prospective acquisition correction technique MRCP and 6 (5.2%) pseudo-defects on single-shot rapid acquisition with relaxation enhancement MRCP. Pseudo-defects were significantly more frequent in patients with ghost artifacts than without (9 of 37 [24.3%] versus one of 78 [1.3%]; P<0.01, McNemar test). CONCLUSION: Although uncommon, pseudo-defects of the CBD caused by IVC pulsation are observed on MRCP. MRCP interpretation that includes comparison with HASTE-ax images can diminish the potential misinterpretation of such CBD motion artifact as bile duct tumor or biliary stone.