Improvement of gadoxetate arterial phase capture with a high spatio-temporal resolution multiphase three-dimensional SPGR-dixon sequence

Detection of arterial phase hyperenhancement of small hepatocellular carcinoma with MRI: Comparison between single arterial and multi-arterial phases and between extracellular and hepatospecific contrast agents

PURPOSE

The purpose of this study was to compare the detection rate of arterial phase hyperenhancement (APHE) in small hepatocellular carcinoma (HCC) between single arterial phase (single-AP) and triple hepatic arterial (triple-AP) phase MRI and between extracellular (ECA) and hepato-specific (HBA) contrast agents.

MATERIALS AND METHODS

A total of 109 cirrhotic patients with 136 HCCs from seven centers were included. There were 93 men and 16 women, with a mean age of 64.0 ± 8.9 (standard deviation) years (range: 42-82 years). Each patient underwent both ECA-MRI and HBA (gadoxetic acid)-MRI examination within one month of each other. Each MRI examination was retrospectively reviewed by two readers blinded to the second MRI examination. The sensitivities of triple- and single-AP for the detection of APHE were compared, and each phase of the triple-AP sequence was compared with the other two.

RESULTS

No differences in APHE detection were found between single-AP (97.2%; 69/71) and triple-AP (98.5%; 64/65) (P > 0.99) at ECA-MRI. No differences in APHE detection were found between single-AP (93%; 66/71) and triple-AP (100%; 65/65) at HBA-MRI (P = 0.12). Patient age, size of the nodules, use of automatic triggering, type of contrast agent, and type of sequence were not significantly associated with APHE detection. The reader was the single variable significantly associated with APHE detection. For triple-AP, best APHE detection rate was found for early and middle-AP images compared to late-AP images (P = 0.001 and P = 0.003). All APHEs were detected with the combination of early-AP and middle-AP images, except one that was detected on late-AP images by one reader.

CONCLUSION

Our study suggests that both single- and triple-AP can be used in liver MRI for the detection of small HCC especially when using ECA. Early AP and middle-AP are the most efficient phases and should be preferred for detecting APHE, regardless of the contrast agent used.

Clinical usefulness of multiple arterial-phase images in gadoxetate disodium-enhanced magnetic resonance imaging: a systematic review and meta-analysis

OBJECTIVES

The multiple arterial-phase (AP) technique was introduced for liver MRI, but it is not really known if multiple AP MRI (MA-MRI) improves image quality and lesion detection rate on gadoxetate disodium-enhanced MRI in comparison with single AP MRI (SA-MRI). We aimed to determine the clinical usefulness of MA-MRI in comparison with SA-MRI.

METHODS

Original articles reporting the percentage of adequate AP imaging and the lesion detection rate on gadoxetate disodium-enhanced MA-MRI were identified in PubMed, EMBASE, and Cochrane Library databases. The pooled percentage of adequate AP imaging and lesion detection rate were calculated using random-effects meta-analysis of single proportions. Subgroup analysis was performed to explain causes of study heterogeneity, and publication bias was evaluated using Egger's test.

RESULTS

Of 772 articles screened, 22 studies in 12 articles were included: 18 studies (ten MA-MRI and eight SA-MRI) suitably defined the percentage of adequate AP imaging and four (three MA-MRI and one SA-MRI) defined the lesion detection rate. MA-MRI had 16.1% higher pooled percentage of adequate AP imaging than SA-MRI (94.8% vs. 78.7%, p < 0.01). MA-MRI additionally detected 33.2% of lesions than SA-MRI (83.2% vs. 50.0%, p = 0.06). Substantial study heterogeneity was found in MA-MRI, and the definition of adequate AP imaging, lesion characteristics, and reference standards were significant factors affecting study heterogeneity (p ≤ 0.02). Significant publication bias was found in MA-MRI (p < 0.01) but not in SA-MRI studies (p = 0.87).

CONCLUSIONS

Gadoxetate disodium-enhanced MA-MRI may be more clinically useful than SA-MRI, but further study is necessary to validate this finding because of study heterogeneity and publication bias.

KEY POINTS

• Multiple arterial-phase MRI (MA-MRI) had a 16.1% higher pooled percentage of adequate AP imaging than single arterial-phase MRI (SA-MRI) (94.8% vs. 78.7%, p < 0.01). • MA-MRI additionally detected an extra 33.2% of lesions compared with SA-MRI (83.2% vs. 50.0%, p = 0.06). • Substantial study heterogeneity and significant publication bias were found across MA-MRI studies.

Rapid Imaging: Recent Advances in Abdominal MRI for Reducing Acquisition Time and Its Clinical Applications

Magnetic resonance imaging (MRI) plays an important role in abdominal imaging. The high contrast resolution offered by MRI provides better lesion detection and its capacity to provide multiparametric images facilitates lesion characterization more effectively than computed tomography. However, the relatively long acquisition time of MRI often detrimentally affects the image quality and limits its accessibility. Recent developments have addressed these drawbacks. Specifically, multiphasic acquisition of contrast-enhanced MRI, free-breathing dynamic MRI using compressed sensing technique, simultaneous multi-slice acquisition for diffusion-weighted imaging, and breath-hold three-dimensional magnetic resonance cholangiopancreatography are recent notable advances in this field. This review explores the aforementioned state-of-the-art techniques by focusing on their clinical applications and potential benefits, as well as their likely future direction.

MRI Simulation-based evaluation of an efficient under-sampling approach

Compressive sampling (CS) has been commonly employed in the field of magnetic resonance imaging (MRI) to accurately reconstruct sparse and compressive signals. In a MR image, a large amount of encoded information focuses on the origin of the k-space. For the 2D Cartesian K-space MRI, under-sampling the frequency-encoding (k_x) dimension does not affect to the acquisition time, thus, only the phase-encoding (k_y) dimension can be exploited. In the traditional random under-sampling approach, it acquired Gaussian random measurements along the phaseencoding (k_y) in the k-space. In this paper, we proposed a hybrid under-sampling approach; the number of measurements in (k_y) is divided into two portions: 70% of the measurements are for random under-sampling and 30% are for definite under-sampling near the origin of the k-space. The numerical simulation consequences pointed out that, in the lower region of the under-sampling ratio r, both the average error and the universal image quality index of the appointed scheme are drastically improved up to 55 and 77% respectively as compared to the traditional scheme. For the first time, instead of using highly computational complexity of many advanced reconstruction techniques, a simple and efficient CS method based simulation is proposed for MRI reconstruction improvement. These findings are very useful for designing new MRI data acquisition approaches for reducing the imaging time of current MRI systems.

Characterization of the arterial enhancement pattern of focal liver lesions by multiple arterial phase magnetic resonance imaging: comparison between hepatocellular carcinoma and focal nodular hyperplasia

PURPOSE

To evaluate the features of arterial enhancement pattern of focal nodular hyperplasia (FNH) and hepatocellular carcinoma (HCC) by triple-phase arterial magnetic resonance imaging (MRI).

METHODS

Data were retrospectively collected from 52 consecutive patients who underwent triple-phase arterial MRI using hepatocyte-specific contrast agents (Gd-EOB-DTPA) from January 2017 to October 2017, with a MR imaging diagnosis of HCC or FNH. The images were independently assessed by two blinded readers. Contrast enhancement ratio (CER) and liver-to-lesion contrast ratio (LLCR) were calculated. The lesions were classified visually and also based on the peak of LLCR into the following groups: (1) early arterial, (2) middle arterial and (3) late arterial. Data were eventually analysed using nonparametric tests.

RESULTS

The CER analysis showed no significant difference between HCC and FNH patients (p > 0.05). LLCR_FNH were significantly higher than LLCR_HCC in the early arterial (p = 0.01), but not in the middle and late arterial phases (p = 0.20 and p = 0.82, respectively). LLCR_HCC presented a meaningful increase from early to middle arterial phase (p = 0.009), whereas LLCR_FNH showed a decrease from middle to late arterial phase (p = 0.004). Based on the peak of LLCR, 17 (55%) FNHs were classified into early, 11 (35%) in middle and only 3 (10%) in late arterial phase groups. Similarly, 14 (34%) HCCs were categorized into early, 13 (32%) in middle and 14 (33%) in late arterial phase groups. There was a good agreement between qualitative analysis and LLCR in 85% of cases.

CONCLUSION

The optimal visualization of FNH has been detected in early and middle arterial phases while HCC has been best observed during middle and late arterial phases.

Gadoxetate acid disodium-enhanced MRI: Multiple arterial phases using differential sub-sampling with cartesian ordering (DISCO) may achieve more optimal late arterial phases than the single arterial phase imaging

BACKGROUND

To prospectively determine whether the use of a multiple arterial phase imaging (DISCO) improve the capturing rate of late arterial phase with less motion artifact than single arterial phase obtained with gadoxetate acid disodium.

MATERIALS AND METHODS

From 06/2017 to 10/2018, prospectively acquired data of 132 patients who underwent either single (n = 67) or multiple arterial phase (n = 65) gadoxetate acid-enhanced MR imaging were analyzed. Two readers independently assessed arterial phase timing and the degree of motion artifact using a five-point scale. The kappa test was used to determine the agreement between the two readers, χ² or fisher exact test were used for the categorical variables and Student t-test or Mann-Whitney U test were used for the comparison of the motion artifacts.

RESULTS

Good to perfect inter-observer agreement was obtained for the arterial phase timing and degree of motion artifact (all kappa value >0.70). Optimal timing of arterial phase was observed in 95.4% (62/65) of multiple arterial phase compared with 73.1% (49/67) of single arterial phase (χ² = 12.209, p < 0.001). Motion artifact score of the late arterial phase images measured using single arterial phase acquisition (3.22 ± 0.68) was significantly higher than the multiple arterial phase (2.42 ± 0.74) group (t = 5.921, p < 0.001). For the multiple arterial phase comparison, motion artifact score of the 2nd, 3rd and 4th phases were also significant reduced compared with 1st, 5th and 6th phases (all p < 0.05).

CONCLUSION

The use of multiple arterial phase acquisition with gadoxetate acid disodium can improve the capturing rate of well-timed late arterial phase with less motion artifact.

Evaluation of Transient Motion During Gadoxetic Acid-Enhanced Multiphasic Liver Magnetic Resonance Imaging Using Free-Breathing Golden-Angle Radial Sparse Parallel Magnetic Resonance Imaging

OBJECTIVES

The aims of this study were to observe the pattern of transient motion after gadoxetic acid administration including incidence, onset, and duration, and to evaluate the clinical feasibility of free-breathing gadoxetic acid-enhanced liver magnetic resonance imaging using golden-angle radial sparse parallel (GRASP) imaging with respiratory gating.

MATERIALS AND METHODS

In this institutional review board-approved prospective study, 59 patients who provided informed consents were analyzed. Free-breathing dynamic T1-weighted images (T1WIs) were obtained using GRASP at 3 T after a standard dose of gadoxetic acid (0.025 mmol/kg) administration at a rate of 1 mL/s, and development of transient motion was monitored, which is defined as a distinctive respiratory frequency alteration of the self-gating MR signals. Early arterial, late arterial, and portal venous phases retrospectively reconstructed with and without respiratory gating and with different temporal resolutions (nongated 13.3-second, gated 13.3-second, gated 6-second T1WI) were evaluated for image quality and motion artifacts. Diagnostic performance in detecting focal liver lesions was compared among the 3 data sets.

RESULTS

Transient motion (mean duration, 21.5 ± 13.0 seconds) was observed in 40.0% (23/59) of patients, 73.9% (17/23) of which developed within 15 seconds after gadoxetic acid administration. On late arterial phase, motion artifacts were significantly reduced on gated 13.3-second and 6-second T1WI (3.64 ± 0.34, 3.61 ± 0.36, respectively), compared with nongated 13.3-second T1WI (3.12 ± 0.51, P < 0.0001). Overall, image quality was the highest on gated 13.3-second T1WI (3.76 ± 0.39) followed by gated 6-second and nongated 13.3-second T1WI (3.39 ± 0.55, 2.57 ± 0.57, P < 0.0001). Only gated 6-second T1WI showed significantly higher detection performance than nongated 13.3-second T1WI (figure of merit, 0.69 [0.63-0.76]) vs 0.60 [0.56-0.65], P = 0.004).

CONCLUSIONS

Transient motion developed in 40% (23/59) of patients shortly after gadoxetic acid administration, and gated free-breathing T1WI using GRASP was able to consistently provide acceptable arterial phase imaging in patients who exhibited transient motion.

LI-RADS technical requirements for CT, MRI, and contrast-enhanced ultrasound

Accurate detection and characterization of liver observations to enable HCC diagnosis and staging using LI-RADS requires a technically adequate imaging exam. To help achieve this objective, LI-RADS has proposed technical requirements for CT, MR, and contrast-enhanced ultrasound of liver. This article reviews the technical requirements for liver imaging, including the description of minimum acceptable technical standards, such as the scanner hardware requirements, recommended dynamic imaging phases, and common technical challenges of liver imaging.

Change in Liver Imaging Reporting and Data System Characterization of Focal Liver Lesions Using Gadoxetate Disodium Magnetic Resonance Imaging Compared With Contrast-Enhanced Computed Tomography

PURPOSE

The aim of this study was to determine whether gadoxetate-enhanced magnetic resonance imaging (MRI) improves lesion characterization in patients at risk for hepatocellular carcinoma compared with computed tomography (CT).

MATERIALS AND METHODS

Forty-nine patients with indeterminate lesions found at contrast-enhanced CT were prospectively enrolled and imaged using gadoxetate-enhanced hepatobiliary phase (HBP) MRI within 30 days of their initial CT. Three readers graded each lesion at CT and MRI using the Liver Imaging Reporting and Data System (LI-RADS) v2014 major criteria and HBP characterization as an ancillary feature. Patients were followed for an average of 1.8 years to document growth or stability of each lesion.

RESULTS

The Liver Imaging Reporting and Data System categorization changed for 71% (52/73) of lesions based on HBP MRI compared with CT, with 30% (22/73) of lesions upgraded and 41% (30/73) of lesions downgraded. There was almost perfect agreement between readers for arterial phase hyperintensity and HBP hypointensity, with lower interreader agreement for washout and capsule appearance. On the basis of composite clinical follow-up, lesions that were subsequently classified as hepatocellular carcinoma were assigned a higher LI-RADS category on HBP MRI when compared with CT.

CONCLUSIONS

For patients with indeterminate lesions seen on contrast-enhanced CT, HBP MRI using gadoxetate improves lesion characterization when using LI-RADS v2014 criteria.

Multiple arterial phase MRI of arterial hypervascular hepatic lesions: improved arterial phase capture and lesion enhancement

PURPOSE

To establish if triple-phase arterial imaging improves the detection of arterial phase hyperintense lesions based on arterial phase capture, motion artifact degradation, and lesion enhancement when compared to single-phase imaging.

MATERIALS AND METHODS

Patients at risk for hepatocellular carcinoma were imaged at 3.0T. Seventy-three consecutive patients with a standard single-phase MRI and eighty-five consecutive patients were imaged using extracellular contrast with triple arterial phase MRI using three sequential accelerated acquisitions of 8 s. Arterial phase capture and image quality were qualitatively categorized. Forty single-phase and forty-four triple-phase studies contained arterially enhancing lesions > 1 cm with washout appearance. The contrast-to-noise ratio (CNR) of the lesions was calculated. We compared the differences in means with Student t-tests and those in arterial phase capture with a Chi squared test with Yates correction.

RESULTS

The triple-phase acquisitions captured the early or late arterial phases more frequently than did the single-phase acquisition (99% vs 86%; P value = 0.006). Triple-phase also provided greater number of patients with early or late arterial phase imaging without motion artifact (92% vs 79%, P-value = 0.05). The lesion analysis revealed increased maximum CNR in the triple-phase imaging (704.4) vs. single-phase imaging (517.2), P-value < 0.001.

CONCLUSION

Triple-phase acquisition provides more robust arterial phase imaging for hepatic lesions, with increased lesion CNR, compared to standard single-phase arterial phase imaging.

Triple Arterial Phase MR Imaging with Gadoxetic Acid Using a Combination of Contrast Enhanced Time Robust Angiography, Keyhole, and Viewsharing Techniques and Two-Dimensional Parallel Imaging in Comparison with Conventional Single Arterial Phase

Objective

To determine whether triple arterial phase acquisition via a combination of Contrast Enhanced Time Robust Angiography, keyhole, temporal viewsharing and parallel imaging can improve arterial phase acquisition with higher spatial resolution than single arterial phase gadoxetic-acid enhanced magnetic resonance imaging (MRI).

Materials and Methods

Informed consent was waived for this retrospective study by our Institutional Review Board. In 752 consecutive patients who underwent gadoxetic acid-enhanced liver MRI, either single (n = 587) or triple (n = 165) arterial phases was obtained in a single breath-hold under MR fluoroscopy guidance. Arterial phase timing was assessed, and the degree of motion was rated on a four-point scale. The percentage of patients achieving the late arterial phase without significant motion was compared between the two methods using the χ² test.

Results

The late arterial phase was captured at least once in 96.4% (159/165) of the triple arterial phase group and in 84.2% (494/587) of the single arterial phase group (p < 0.001). Significant motion artifacts (score ≤ 2) were observed in 13.3% (22/165), 1.2% (2/165), 4.8% (8/165) on 1st, 2nd, and 3rd scans of triple arterial phase acquisitions and 6.0% (35/587) of single phase acquisitions. Thus, the late arterial phase without significant motion artifacts was captured in 96.4% (159/165) of the triple arterial phase group and in 79.9% (469/587) of the single arterial phase group (p < 0.001).

Conclusion

Triple arterial phase imaging may reliably provide adequate arterial phase imaging for gadoxetic acid-enhanced liver MRI.

Optimal visualization of focal nodular hyperplasia: quantitative and qualitative evaluation of single and multiphasic arterial phase acquisition at 1.5 T MR imaging

PURPOSE

To evaluate the qualitative and quantitative benefit of multiple arterial phase acquisitions for the depiction of hypervascularity in FNH explored MR imaging using an extracellular contrast agent.

METHODS

Between 2007 and 2014, all patients who underwent MR imaging for the exploration of FNH were included. The protocol included a single or a triple arterial phase ("single" and "triple" group, respectively). Arterial phases were visually divided into four types: (1) angiographic, (2) early, (3) late, and (4) portal. Signal intensity on arterial phase images was visually recorded as intense, moderate, or low for each lesion. Lesion-to-liver contrast (LLC) and relative lesion enhancement (RE) were calculated and compared between the two groups using the Mann-Whitney test.

RESULTS

Thirty-five women were included (mean 45-year old, range 20-66), with 50 FNH (mean size 30 mm). Single and triple groups included 20 patients (30 FNH) and 15 patients (20 FNH), respectively. Signal intensity was intense in all lesions in the triple group and in 22/30 (73%) in the single group (p = 0.041). Intense signals were more frequently found in the early arterial phase (p < 0.001). RE was not significantly different (1.78 ± 0.84 vs. 1.98 ± 1.81 p = 0.430, in the single and triple groups, respectively) but LLC was significantly higher in the triple group (0.32 ± 0.10 vs. 0.22 ± 0.10, p = 0.005). LLC was significantly higher in the first two arterial phases in the triple group (p < 0.001).

CONCLUSION

Acquisition of three arterial phases improves the visualization of hypervascularity of FNH, as lesions show high visual signal intensity and contrast. Optimal visualization is obtained in the early arterial phase.

Combined parenchymal and vascular imaging: High spatiotemporal resolution arterial evaluation of hepatocellular carcinoma

PURPOSE

To assess the ability of high-resolution arterial phase imaging of hepatocellular carcinoma (HCC) to provide combined vascular characterization and parenchymal evaluation.

MATERIALS AND METHODS

Thirty-eight consecutive studies in cirrhotic patients with HCC scanned with a view-shared 2-point-Dixon-based Differential Subsampling with Cartesian Ordering (DISCO) sequence were analyzed. Lesion contrast relative to precontrast and adjacent parenchyma was evaluated and compared using a Fisher's exact test. Visibility of hepatic arteries and tumor feeding vessels were graded on a 5-point scale. Catheter angiography was used as a reference standard for arterial anatomy.

RESULTS

The high spatiotemporal multiphasic acquisition allowed imaging of both the angiographic and late arterial phase in 30 of 38 studies with good image quality. Maximal lesion enhancement compared to precontrast occurred more frequently during the late arterial phase compared to maximal lesion-to-adjacent, which occurred more frequently during the early arterial phase (P < 0.001). Common and proper hepatic arteries were visualized adequately in 100%, right hepatic artery in 94-97%, left hepatic artery in 94%, and segmental vessel in 83% of cases. Arterial variants were detected with sensitivity of 87-100% and specificity of 100%.

CONCLUSION

High spatiotemporal resolution arterial phase imaging provides multiple angiographic and arterial phases in a single breath-hold, enabling accurate depiction of vascular anatomy while maintain optimal arterial phase imaging for characterization of focal lesions.

High temporal resolution dynamic MRI and arterial input function for assessment of GFR in pediatric subjects

PURPOSE

To introduce a respiratory-gated high-spatiotemporal-resolution dynamic-contrast-enhanced MRI technique and a high-temporal-resolution aortic input function (HTR-AIF) estimation method for glomerular filtration rate (GFR) assessment in children.

METHODS

A high-spatiotemporal-resolution DCE-MRI method with view-shared reconstruction was modified to incorporate respiratory gating, and an AIF estimation method that uses a fraction of the k-space data from each respiratory period was developed (HTR-AIF). The method was validated using realistic digital phantom simulations and demonstrated on clinical subjects. The GFR estimates using HTR-AIF were compared with estimates obtained by using an AIF derived directly from the view-shared images.

RESULTS

Digital phantom simulations showed that using the HTR-AIF technique gives more accurate AIF estimates (RMSE = 0.0932) compared with the existing estimation method (RMSE = 0.2059) that used view-sharing (VS). For simulated GFR > 27 mL/min, GFR estimation error was between 32% and 17% using view-shared AIF, whereas estimation error was less than 10% using HTR-AIF. In all clinical subjects, the HTR-AIF method resulted in higher GFR estimations than the view-shared method.

CONCLUSION

The HTR-AIF method improves the accuracy of both the AIF and GFR estimates derived from the respiratory-gated acquisitions, and makes GFR estimation feasible in free-breathing pediatric subjects.

The diagnostic value of Gd-EOB-DTPA-MRI for the diagnosis of focal nodular hyperplasia: a systematic review and meta-analysis

OBJECTIVE

We aimed to systematically review the gadoxetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-MRI) findings of focal nodular hyperplasia (FNH) and its diagnostic value.

METHODS

A thorough literature search was conducted in Ovid-MEDLINE and EMBASE databases to identify studies evaluating Gd-EOB-DTPA-MRI findings of FNH. To evaluate the frequency of characteristic imaging findings on Gd-EOB-DTPA-MRI, pooled proportions of high/iso signal intensity (SI) on the hepatobiliary phase (HBP), arterial enhancement, high/iso SI on the portal-venous phase (PVP) or equilibrium phase (EP), and the central scar were calculated. Meta-analysis was performed to evaluate the diagnostic accuracy of high/iso SI on HBP for distinguishing FNH from hepatocellular adenoma.

RESULTS

A review of 96 articles identified ten eligible articles with 304 patients with FNHs for meta-analysis. Pooled proportion of the Gd-EOB-DTPA-MRI findings showed that high/iso SI on the HBP, arterial enhancement, and high/iso SI on the PVP/EP were observed in 93% (95% CI, 90-97%), 99% (95% CI, 97-100%), and 97% (95% CI, 95-99%) of FNHs, respectively, while a central scar was observed in 61% of FNHs (95% CI, 47-74%). High/iso SI on the HBP was highly accurate for distinguishing FNH from hepatocellular adenoma, with a summary sensitivity of 93.9% (95% CI, 89.1-97.1%) and a specificity of 95.3% (95% CI, 88.4-98.7%).

CONCLUSIONS

High/iso SI on the HBP of Gd-EOB-DTPA-MRI is characteristic and a prevalent finding of FNHs and can be helpful in the management of patients with FNH.

KEY POINTS

• The vast majority (94-97 %) of FNHs show high/iso SI on HBP. • High/iso SI on HBP was accurate for distinguishing FNH from hepatocellular adenoma. • HBP of Gd-EOB-DTPA-MRI can reduce unnecessary biopsies for the diagnosis of FNHs.

Combined dynamic contrast-enhanced liver MRI and MRA using interleaved variable density sampling

PURPOSE

To develop and evaluate a method for volumetric contrast-enhanced MRI of the liver, with high spatial and temporal resolutions, for combined dynamic imaging and MR angiography (MRA) using a single injection of contrast agent.

METHODS

An interleaved variable density (IVD) undersampling pattern was implemented in combination with a real-time-triggered, time-resolved, dual-echo 3D spoiled gradient echo sequence. Parallel imaging autocalibration lines were acquired only once during the first time frame. Imaging was performed in 10 subjects with focal nodular hyperplasia (FNH) and compared with their clinical MRI. The angiographic phase of the proposed method was compared with a dedicated MR angiogram acquired during a second injection of contrast.

RESULTS

A total of 21 FNH, three cavernous hemangiomas, and 109 arterial segments were visualized in 10 subjects. The temporally resolved images depicted the characteristic arterial enhancement pattern of the lesions with a 4-s update rate. Images were graded as having significantly higher quality compared with the clinical MRI. Angiograms produced from the IVD method provided noninferior diagnostic assessment compared with the dedicated MR angiogram.

CONCLUSION

Using an undersampled IVD imaging method, we have demonstrated the feasibility of obtaining high spatial and temporal resolution dynamic contrast-enhanced imaging and simultaneous MRA of the liver.