Optimal acquisition delay for dynamic contrast-enhanced MRI of hypervascular hepatocellular carcinoma. AJR Am J Roentgenol. 2009;192:686-692. [PMID: 19234264 DOI: 10.2214/ajr.08.1255]

Gadoxetic acid-enhanced high temporal-resolution hepatic arterial-phase imaging with view-sharing technique: Impact on the LI-RADS category

PURPOSE

To evaluate the value of view-sharing multi-hepatic arterial-phase (mHAP) imaging for diagnosis of hypervascular hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Forty-seven consecutive patients with HCC underwent gadoxetic acid-enhanced magnetic resonance (MR) imaging before angiographic and lipiodol CT. Hepatic arterial-phase images were obtained at 5 consecutive phases with shared central k-space of 25%, followed by portal venous, late (2 and 3min), and hepatobiliary phase imaging. One-hundred-eight HCC nodules (size: 5-88mm, mean size: 18.2mm) confirmed on angiographic CT and lipiodol CT were evaluated for LI-RADS category and compared with single arterial-phase and mHAP findings regarding wash out, capsule, corona enhancement, and image quality.

RESULTS

Twenty-four HCCs (22.2%) (size: 6-19mm, mean size: 12.3mm) were categorized as LR-3 based on the single arterial-phase. Capsule appearance (25.9%) and washout (57.4%) were most frequently observed in late phase (2min). Corona enhancement was observed in 73.1% of all HCCs on mHAP. For the 24 HCCs of LR-3, corona enhancement was observed in 75% on mHAP and contributed to upgrade category. No significant difference was found in the frequency of corona enhancement between mHAP and angiographic CT (P=0.11). Image quality was valued as good or excellent in all cases.

CONCLUSION

View-sharing mHAP was feasible without compromising image quality and contributed to the improvement in diagnostic confidence for hypervascular HCC in gadoxetic acid-enhance MR imaging.

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

Objectives

The 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).

Methods

In 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.

Results

The 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).

Conclusions

The 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.

Magnetic resonance imaging of the cirrhotic liver in the era of gadoxetic acid

Gadoxetic acid improves detection and characterization of focal liver lesions in cirrhotic patients and can estimate liver function in patients undergoing liver resection. The purpose of this article is to describe the optimal gadoxetic acid study protocol for the liver, the unique characteristics of gadoxetic acid, the differences between gadoxetic acid and extra-cellular gadolium chelates, and the differences in phases of enhancement between cirrhotic and normal liver using gadoxetic acid. We also discuss how to obtain and recognize an adequate hepatobiliary phase.

[Modern magnetic resonance imaging of the liver]

Magnetic resonance imaging (MRI) of the liver has become an essential tool in the radiological diagnostics of both focal and diffuse diseases of the liver and is subject to constant change due to technological progress. Recently, important improvements could be achieved by innovations regarding MR hardware, sequences and postprocessing methods. The diagnostic spectrum of MRI could be broadened particularly due to new examination sequences, while at the same time scanning time could be shortened and image quality has been improved. The aim of this article is to explain both the technological background and the clinical application of recent MR sequence developments and to present the scope of a modern MRI protocol for the liver.

Superparamagnetic iron oxide-enhanced magnetic resonance imaging for focal hepatic lesions: Systematic review and meta-analysis

AIM: To evaluate the performance of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance imaging (MRI) in the detection and characterization of focal hepatic lesions (FHLs).

METHODS: This meta-analysis compared relevant studies that were identified by searching PubMed, EMBASE, and the Cochrane Library databases for articles published between January 1988 and September 2014 and that met the following criteria: (1) SPIO-enhanced MRI was conducted to identify FHLs and data were sufficient for pooled analysis using Meta-DiSc 1.4; (2) hepatocellular carcinomas (HCCs) were differentiated from other FHLs; (3) well-differentiated HCCs (WD-HCCs) were contradistinguished from dysplastic nodules; and (4) WD-HCCs were compared with moderately and poorly differentiated HCCs (MD- and PD-HCCs, respectively).

RESULTS: The data obtained from 15 eligible studies yielded a sensitivity of 85% and a specificity of 78% for differentiating between HCCs and other FHLs. The sensitivity was unchanged and the specificity was increased to 87% when non-HCC malignancies were excluded. Comparative analyses between WD-HCCs and MD- and PD-HCCs from seven studies showed a sensitivity of 98% and a specificity of 50% for the diagnosis of MD- and PD-HCCs, and the area under the summary receiver operating characteristics (sROC) curve was 0.97. A comparison between WD-HCCs and dysplastic nodules revealed a sensitivity of 50% and a specificity of 92% for the diagnosis of WD-HCCs and the area under the sROC curve was 0.80.

CONCLUSION: SPIO-enhanced MRI is useful in differentiating between HCCs and other FHLs.

Evaluation of optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI using MR fluoroscopic triggering and slow injection technique

OBJECTIVE

The purpose of this article is to prospectively evaluate the optimal scan delay for gadoxetate disodium-enhanced hepatic arterial phase MRI of hypervascular hepatocellular carcinoma (HCC) using MR fluoroscopic triggering and a slow-injection technique.

SUBJECTS AND METHODS

Sixty-three patients (37 men and 26 women; age range, 33-92 years; mean age, 68.2 years) underwent gadoxetate disodium-enhanced MRI; there were 33 hypervascular HCCs (size range, 8-57 mm; mean size, 19.8 mm) in 19 patients. The time from the start of contrast agent injection to its arrival in the abdominal aorta (time to arrival) and the time from contrast agent arrival to peak enhancement (time to peak) were determined using MR fluoroscopy using IV slow injection at 1 mL/s of contrast material and a saline chaser. All patients underwent four-phase whole-liver imaging with a 3D keyhole gradient-echo sequence during a single breath-hold immediately after confirmation of aortic peak enhancement. Delays from peak aortic enhancement to k-space filling were 5-9, 10-14, 15-19, and 20-28 seconds, respectively, in the four phases. Time to arrival, time to peak, and HCC-to-liver contrast were evaluated.

RESULTS

The time to arrival (range, 11-24 seconds; mean, 16.2 seconds) and the time to peak (range, 3-10 seconds; mean, 6.8 seconds) showed considerable variation among patients. HCC-to-liver contrast peaked at the first phase in 58% of cases, at the second phase in 42% of cases, and at the third and fourth phases in 0% of cases. Mean HCC-to-liver contrast in the first and second phases was significantly higher than that in the third and fourth phases (p<0.01).

CONCLUSION

Optimal scan delays for imaging hypervascular HCCs with gadoxetate disodium-enhanced hepatic arterial phase MRI was 7-12 seconds after the peak aortic enhancement using a slow-injection protocol.

Timing of the hepatic arterial phase at Gd-EOB-DTPA-enhanced hepatic dynamic MRI: comparison of the test-injection and the fixed-time delay method

PURPOSE

To compare the fixed-time- and the test-injection method with respect to the image quality of hypervascular hepatocellular carcinoma (HCC) and the adequacy of timing of the hepatic arterial phase (HAP) in Gd-EOB-DTPA (EOB) enhanced MRI.

MATERIALS AND METHODS

We studied 63 patients with computed tomography (CT) -proven hypervascular HCC: 30 (group 1) were scanned HAP using the fixed-time delay method (protocol 1); in the other 33 (group 2), we applied the test-injection method (protocol 2). We compared the protocols with respect with tumor-to-liver contrast (TLC), contrast-to-noise-ratio (CNR), and relative enhancement of the liver and tumor (REL , RET ) during HAP. Two radiologists compared the adequacy of HAP, image contrast, image noise, and overall image quality.

RESULTS

Under protocol 2, TLC, CNR, and REL and RET of hypervascular HCC were significantly higher (P < 0.01). The proportion of optimal HAP was significantly higher for protocol 2 than protocol 1 (P < 0.01). The visual score of the image contrast and the overall image quality were significantly higher in group 2 than group 1 (P = 0.02 and P = 0.01, respectively).

CONCLUSION

At EOB-enhanced hepatic dynamic MRI, the test-injection method yielded better image quality of hypervascular HCC and improved adequacy of timing of HAP.

Magnetic resonance imaging of the liver: sequence optimization and artifacts

The liver is one of the most challenging organs of the body to image with magnetic resonance because it is large and mobile, receives a dual blood supply, and is surrounded by organs and structures that contribute to artifacts from flow and susceptibility. Recent advances in imaging hardware, in addition to improvements in temporal resolution and development of hepatocyte-specific contrast agents, make imaging of the liver more approachable than in the past; however, it remains a complex process that requires compromise. In this article the authors discuss development and optimization of a liver imaging protocol at 1.5 T, with common variations in each element of the protocol, as well as the strengths and weaknesses associated with the relevant sequences.

Comparison of portal venous and delayed phases of gadolinium-enhanced magnetic resonance imaging study of cirrhotic liver for the detection of contrast washout of hypervascular hepatocellular carcinoma

OBJECTIVE

To retrospectively compare portal venous phase (PVP) and delayed phase (DP) for the detection of tumor washout at gadobenate dimeglumine-enhanced liver magnetic resonance imaging (MRI) in cirrhotic patients with hypervascular hepatocellular carcinoma (HCC).

METHODS

Thirty-three patients with 55 HCCs underwent 1.5-T MRI by means of fat-suppressed T1-weighted sequence obtained before and after gadobenate dimeglumine administration, during early and late arterial phases, PVP (70 seconds), and DP (180 seconds). Detection rates of contrast washout of hypervascular HCCs and tumor-to-liver contrast on PVP and DP were measured and compared.

RESULTS

Among 54 hypervascular HCCs, washout was present in 24 (44%) of 54 tumors on PVP and in 44 (82%) of 54 on DP (P < 0.001). In 20 (37%) of 54 tumors, washout was deemed present only on DP. Delayed phase images yielded significantly higher mean tumor-to-liver contrast absolute values compared with PVP images (-24.5 [56.1] vs -9.3 [52.6], P = 0.001).

CONCLUSIONS

Delayed phase is superior to PVP for the washout detection of hypervascular HCC at gadobenate dimeglumine-enhanced MRI of cirrhotic liver.

[Simulation study for artifacts on Gd-EOB-DTPA-enhanced liver dynamic MR imaging in arterial dominant phase]

We performed a simulation for artifacts on liver dynamic MR imaging with the contrast agent gadolinium-ethoxybenzyl (Gd-EOB)-DTPA. The signal enhancement of the image by the contrast agent in the arterial dominant phase was assumed, and the time-enhancement curve was numerically generated. The data in k-space was obtained by the Fourier transform of a liver image. By assuming the scan timing and duration in the time-enhancement curve, the data set of each phase-encoding step in k-space was increased in proportion to the corresponding intensity in the time-enhancement curve. We obtained the simulated image by the Fourier transform of the k-space data, and investigated artifacts in the image. Assuming the use of the centric k-space filling scheme, blurring in the image is found when the scan timing is delayed. When the scan is started in an early timing, we observe the effect of edge enhancement in the image. These artifacts of blurring and edge enhancement are decreased by shortening the scan duration. Assuming the use of the sequential k-space filling scheme, those artifacts are not prominent. The use of the sequential scheme would be effective for the purpose of avoiding the artifacts. It is known that the contrast enhancement would not be sufficient without optimal scan timing; in addition, artifacts should be noted. For basic study of the contrast enhancement and artifacts, our simulation technique based on the time-enhancement curve would be useful.