Radial MRI during free breathing in contrast-enhanced hepatobiliary phase imaging.

BACKGROUND: Use of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for diagnosis of hepatic tumors has been previously reported. Fat-saturated 3D T1-weighted gradient echo sequence (TIGRE) imaging using a breath-hold technique is usually used for dynamic studies and hepatobiliary phase Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI). In cases where the patient has difficulty holding their breath, this scanning method can be difficult. PURPOSE: To investigate the usefulness of a fat-saturated T1-weighted spin-echo (SE) sequence using a radial read-out (radial acquisition regime-SE, RADAR-SE) during free breathing for hepatobiliary phase Gd-EOB-DTPA-enhanced MRI. MATERIAL AND METHODS: Images were acquired at 1.5 T. First, a phantom with diluted Gd-EOB-DTPA was scanned using the TIGRE sequence and the RADAR-SE sequence. Contrast ratios of the sequences were compared. Next, the hepatobiliary phase was imaged in 62 patients using the TIGRE sequence with breath-hold and the RADAR-SE during free breathing. Qualitative and quantitative evaluations were compared. RESULTS: In the phantom study, RADAR-SE had a higher contrast ratio than TIGRE. In the clinical study, artifacts were more conspicuous in RADAR-SE compared to TIGRE images in the qualitative evaluation. However, RADAR-SE images were equal to or better than TIGRE images in patients who had difficulty holding their breath. The signal intensity ratio of the liver was statistically higher using RADAR-SE than TIGRE. CONCLUSION: RADAR-SE can be useful for hepatobiliary phase Gd-EOB-DTPA-enhanced MRI in patients who have difficulty holding their breath.

Gadoxetic acid disodium-enhanced hepatocyte phase MRI: can increasing the flip angle improve focal liver lesion detection?

PURPOSE: To determine whether hepatocyte phase gadoxetic acid disodium (EOB)-enhanced MRI using a high flip angle (FA) improves focal liver lesion (FLL) detection compared with using a standard low FA. MATERIALS AND METHODS: Sixty-two consecutive patients with 159 FLLs underwent EOB-enhanced MRI during the hepatocyte phase at 5, 10, 15, and 20 min, with both low (10°) and high (30°) FAs. Two blinded radiologists independently and randomly reviewed the two image sets using a four-point rating scale. Sensitivities and specificities were calculated and lesion-to-liver contrast ratio (LLC) on all hepatocyte phase images was measured. RESULTS: The sensitivities with high FA for small (≤10 mm) malignant FLLs were significantly higher than those with low FA, at all time points, for both readers (P ≤ 0.05). Meanwhile, the specificities of the two protocols for the detection of all FLLs at all time points during the hepatocyte phase were high and same (98.2%) for both readers, without any significant differences (P = 1.00). LLCs with high FA were significantly higher than those with low FA at all time points (P ≤ 0.001). CONCLUSION: Hepatocyte phase EOB-enhanced MRI with increasing FA can significantly increase LLC and improve the detection of FLLs, particularly small malignant lesions.

Can MR fluoroscopic triggering technique and slow rate injection provide appropriate arterial phase images with reducing artifacts on gadoxetic acid-DTPA (Gd-EOB-DTPA)-enhanced hepatic MR imaging?

PURPOSE: To evaluate whether using MR fluoroscopic triggering technique and slow rate injection improves the quality of arterial phase images in gadoxetic acid-DTPA-enhanced (Gd-EOB-DTPA) MR imaging because of proper acquisition timing and reduction of artifacts. MATERIALS AND METHODS: Two hundred sixteen patients undergoing examination for liver diseases were retrospectively reviewed. All MR images were obtained with two Gd-EOB-DTPA injection protocols: (i) a combination protocol, in which the MR fluoroscopic triggering technique and slow rate injection (1 mL/s) were used; and for comparison, (ii) a conventional protocol, in which adjusted fixed scan delay and ordinary rate injection (2 mL/s) were adopted. Signal-to-noise ratio (SNR) of aorta, portal vein, and liver parenchyma on arterial phase images were calculated. Two blinded readers independently evaluated the obtained arterial phase images in terms of acquisition timing and degree of artifacts. RESULTS: The SNRs of aorta and portal vein on arterial phase images were significantly higher in the combination protocol group (aorta/portal: 221.9 +/- 91.9/197.1 +/- 89.8) than that in the conventional protocol group (aorta/portal: 169.8 +/- 97.4/92.7 +/- 48.5) (P < 0.05). The acquisition timing for arterial phase images with the combination protocol was significantly better than that with the conventional protocol (P < 0.01). The image quality of the combination protocol was significantly higher than that of the conventional protocol (P < 0.01). The occurrence rate of moderate or severe degree of artifacts in the conventional protocol (38.0%) was more prominent than that in the combination protocol (18.5%). CONCLUSION: The combination of the MR fluoroscopic triggering technique and slow rate injection provides proper arterial phase images and reduces the artifacts in Gd-EOB-DTPA MR imaging.

Evaluation of the changes in signals from the spleen using ferucarbotran.

PURPOSE: Because superparamagnetic iron oxide is actively taken into the reticuloendothelial system, the signal intensity observed on T2-weighted images is reduced not only in the liver but also in the spleen. There is no difference in the reduction in signal intensity in the liver after contrast between the ferumoxides and ferucarbotran, but the reduction in signal intensity in the spleen is considerable. In the present study, we examined the efficacy of T2*-weighted imaging to compensate for the reduction in signal intensity in the spleen by administering ferucarbotran. MATERIALS AND METHODS: We examined the images obtained from 35 patients who underwent MRI with ferucarbotran. T2-weighted images and T2*-weighted images were obtained before and after administration of ferucarbotran, and the changes in signal intensity in the liver and spleen were then analyzed. RESULTS: A reduction in signal intensity was observed in the liver by both T2- and T2*-weighted imaging. In the spleen, the signal intensity was reduced on T2-weighted images but was not reduced on T2*-weighted images. CONCLUSION: The reduction in signal intensity due to administration of ferucarbotran is low in the spleen. Thus, it was considered necessary to approach the problem of diagnosing ectopic splenic tissue using ferucarbotran with caution.