CAIPIRINHA-Dixon-TWIST (CDT)-VIBE MR imaging of the liver at 3.0T with gadoxetate disodium: a solution for transient arterial-phase respiratory motion-related artifacts?

CT/MRI technical pitfalls for diagnosis and treatment response assessment using LI-RADS and how to optimize

Hepatocellular carcinoma (HCC), the most common primary liver cancer, is a significant global health burden. Accurate imaging is crucial for diagnosis and treatment response assessment, often eliminating the need for biopsy. The Liver Imaging Reporting and Data System (LI-RADS) standardizes the interpretation and reporting of liver imaging for diagnosis and treatment response assessment, categorizing observations using defined categories that are based on the probability of malignancy or post-treatment tumor viability. Optimized imaging protocols are essential for accurate visualization and characterization of liver findings by LI-RADS. Common technical pitfalls, such as suboptimal postcontrast phase timing, and MRI-specific challenges like subtraction misregistration artifacts, can significantly reduce image quality and diagnostic accuracy. The use of hepatobiliary contrast agents introduces additional challenges including arterial phase degradation and suboptimal uptake in advanced cirrhosis. This review provides radiologists with comprehensive insights into the technical aspects of liver imaging for LI-RADS. We discuss common pitfalls encountered in routine clinical practice and offer practical solutions to optimize imaging techniques. We also highlight technical advances in liver imaging, including multi-arterial MR acquisition and compressed sensing. By understanding and addressing these technical aspects, radiologists can improve accuracy and confidence in the diagnosis and treatment response assessment for hepatocellular carcinoma.

Deep learning-based image reconstruction for the multi-arterial phase images: improvement of the image quality to assess the small hypervascular hepatic tumor on gadoxetic acid-enhanced liver MRI

PURPOSE

To evaluated the impact of a deep learning (DL)-based image reconstruction on multi-arterial-phase magnetic resonance imaging (MA-MRI) for small hypervascular hepatic masses in patients who underwent gadoxetic acid-enhanced liver MRI.

METHODS

We retrospectively enrolled 55 adult patients (aged ≥ 18 years) with small hepatic hypervascular mass (≤ 3 cm) between December 2022 and February 2023. All patients underwent MA-MRI, subsequently reconstructed with a DL-based application. Qualitative assessment with Linkert scale including motion artifact (MA), liver edge (LE), hepatic vessel clarity (HVC) and image quality (IQ) was performed. Quantitative image analysis including signal to noise ratio (SNR), contrast to noise ratio (CNR) and noise was performed.

RESULTS

On both arterial phases (APs), all qualitative parameters were significantly improved after DL-based image reconstruction. (LE on 1st AP, 1.22 vs 1.61; LE on 2nd AP, 1.21 vs 1.65; HVC on 1st AP, 1.24 vs 1.39; HVC on 2nd AP, 1.24 vs 1.44; IQ on 1st AP, 1.17 vs 1.45; IQ on 2nd AP, 1.17 vs 1.47, all p values < 0.05). The SNR, CNR and noise were significantly improved after DL-based image reconstruction. (SNR on AP1, 279.08 vs 176.14; SNR on AP2, 334.34 vs 199.24; CNR on AP1, 106.09 vs 64.14; CNR on AP2, 129.66 vs 73.73; noise on AP1, 1.51 vs 2.33; noise on AP2, 1.45 vs 2.28, all p values < 0.05).

CONCLUSIONS

Gadoxetic acid-enhanced MA-MRI with DL-based image reconstruction improved the qualitative and quantitative parameters. Despite the short acquisition time, high-quality MA-MRI is now achievable.

Intra-patient and inter-observer image quality analysis in liver MRI study with gadoxetic acid using two different multi-arterial phase techniques

PURPOSE

To evaluate intra-patient and interobserver agreement in patients who underwent liver MRI with gadoxetic acid using two different multi-arterial phase (AP) techniques.

METHODS

A total of 154 prospectively enrolled patients underwent clinical gadoxetic acid-enhanced liver MRI twice within 12 months, using two different multi-arterial algorithms: CAIPIRINHA-VIBE and TWIST-VIBE. For every patient, breath-holding time, body mass index, sex, age were recorded. The phase without contrast media and the APs were independently evaluated by two radiologists who quantified Gibbs artefacts, noise, respiratory motion artefacts, and general image quality. Presence or absence of Gibbs artefacts and noise was compared by the McNemar's test. Respiratory motion artefacts and image quality scores were compared using Wilcoxon signed rank test. Interobserver agreement was assessed by Cohen kappa statistics.

RESULTS

Compared with TWIST-VIBE, CAIPIRINHA-VIBE images had better scores for every parameter except higher noise score. Triple APs were always acquired with TWIST-VIBE but failed in 37% using CAIPIRINHA-VIBE: 11% have only one AP, 26% have two. Breath-holding time was the only parameter that influenced the success of multi-arterial techniques. TWIST-VIBE images had worst score for Gibbs and respiratory motion artefacts but lower noise score.

CONCLUSION

CAIPIRINHA-VIBE images were always diagnostic, but with a failure of triple-AP in 37%. TWIST-VIBE was successful in obtaining three APs in all patients. Breath-holding time is the only parameter which can influence the preliminary choice between CAIPIRINHA-VIBE and TWIST-VIBE algorithm.

ADVANCES IN KNOWLEDGE

If the patient is expected to perform good breath-holds, TWIST-VIBE is preferable; otherwise, CAIPIRINHA-VIBE is more appropriate.

State-of-the-art magnetic resonance imaging sequences for pediatric body imaging

Longer examination time, need for anesthesia in smaller children and the inability of most children to hold their breath are major limitations of MRI in pediatric body imaging. Fortunately, with technical advances, many new and upcoming MRI sequences are overcoming these limitations. Advances in data acquisition and k-space sampling methods have enabled sequences with improved temporal and spatial resolution, and minimal artifacts. Sequences to minimize movement artifacts mainly utilize radial k-space filling, and examples include the stack-of-stars method for T1-weighted imaging and the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)/BLADE method for T2-weighted imaging. Similarly, the sequences with improved temporal resolution and the ability to obtain multiple phases in a single breath-hold in dynamic imaging mainly use some form of partial k-space filling method. New sequences use a variable combination of data sampling methods like compressed sensing, golden-angle radial k-space filling, parallel imaging and partial k-space filling to achieve free-breathing, faster sequences that could be useful for pediatric abdominal and thoracic imaging. Simultaneous multi-slice method has improved diffusion-weighted imaging (DWI) with reduction in scan time and artifacts. In this review, we provide an overview of data sampling methods like parallel imaging, compressed sensing, radial k-space sampling, partial k-space sampling and simultaneous multi-slice. This is followed by newer available and upcoming sequences for T1-, T2- and DWI based on these other advances. We also discuss the Dixon method and newer approaches to reducing metal artifacts.

Magnetic Resonance Imaging and Magnetic Resonance Imaging Cholangiopancreatography of the Pancreas in Small Animals

Simple Summary

In human medicine Magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP) play a consistent role in the investigation of pancreatic and pancreatic duct disorders. In veterinary medicine the number of studies focused on MR and MRCP for pancreatic disease is scant, and the protocols are not yet standardized. This review will focus on the MRI and MRCP technical aspects of the protocols used for the investigation of pancreatic disease in veterinary medicine. The aim of this review is to elucidate the value and the potential of each MR and MRCP sequence listed in the different protocols, either in canine or feline patients, with the intention to build a valid and solid tool for further innovative studies.

Abstract

Magnetic resonance imaging (MRI) and MR cholangiopancreatography (MRCP) have emerged as non-invasive diagnostic techniques for the diagnosis of pancreatic and pancreatic duct disorders in humans. The number of studies focused on MR and MRCP for pancreatic disease in small animals is very limited. MR has been described for the evaluation of insulinoma in dogs and to investigate pancreatitis in cats. The studies were based on a standard protocol with T2 weighted (w) fast recovery fast spin-echo (FRFSE) with and without fat suppression, T1w FSE pre-contrast and T1w FSE post-contrast with and without fat suppression. MRCP after secretin stimulation has been described in cats to assess the pancreatic ductal system, taking advantage of pulse sequences heavily T2w as rapid acquisition with rapid enhancement (RARE), fast-recovery fast spin-echo (FRFSE) sequences and single-shot fast spin-echo (SSFSE) sequences. In addition to the standard protocol, fast spoiled gradient recalled echo pulse sequences (fSPGR) and volume interpolated 3D gradient-echo T1w pulse sequences pre and post-contrast have also been used in cats, reaching the goal of assessing the biliary tree and the pancreatic duct with the same sequence and in multiple planes. Despite the small amount of data, the results show potential, and the most recent technical innovations, in particular, focused on diffusion MRI and fast acquisition, further support the need for continued evaluation of MRI as an effective instrument for the investigation of pancreatic disease.

Evaluation of late arterial acquisition and image quality after gadoxetate disodium injection using the CDT-VIBE sequence

To explore the applicability of multi-arterial phase imaging technique in gadoxetate disodium-enhanced MRI. We studied 140 consecutive patients with suspected liver lesions who underwent gadoxetate disodium-enhanced MRI before surgery. All patients were randomized into three groups: group A (n = 50) was examined with VIBE-based single-artery phase imaging, group B (n = 44) with StarVIBE, and group C (n = 46) with CAIPIRINHA-Dixon-TWIST-VIBE (CDT-VIBE)-based multi-artery phase imaging. We evaluated the display rate of late arterial images and image quality in arterial phase images. We performed a study of 140 consecutive patients suspected with liver lesions who received gadoxetate disodium-enhanced MRI examination before surgery. All patients were randomly divided into three groups: group A (n = 50) was examined with single arterial phase imaging based on VIBE, group B (n = 44) was based on StarVIBE and group C (n = 46) was analyzed with multi-arterial phase imaging based on CAIPIRINHA-Dixon-TWIST-VIBE (CDT-VIBE). We evaluated the display rate of late arterial images and the image quality of dynamically enhanced images. Both radiologists had an almost perfect agreement (Kappa value > 0.8) in the assessment of late arterial and image quality. For late arterial acquisition, group C was superior to groups A and B (x² = 18.940, P < 0.05); The image of phase 4 had the highest display rate in the late artery phase. For arterial phase image quality, there was no difference between groups A, B and C at five phases (H = 10.481, P = 0.106); and the best image quality score was lower in group C than in groups A and B (H = 8.573, P = 0.014).For the quality of the late arterial images, there was a statistical difference between the best images in groups A, B and C (H = 6.619, P = 0.037), and the images in group C were significantly better than those in group A (P_.adj < 0.05). By applying multi-arterial phase acquisition based on CDT-VIBE, gadoxetate disodium-enhanced MRI scanning can obtain a better late arterial phase and provide high-quality images with fewer motion artifacts.

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.

Transient Severe Motion Artifact on Arterial Phase in Gadoxetic Acid-Enhanced Liver Magnetic Resonance Imaging: A Systematic Review and Meta-analysis

OBJECTIVES

The aims of this study were to determine the incidence of transient severe motion artifact (TSM) on arterial phase gadoxetic acid-enhanced magnetic resonance imaging of the liver and to investigate the causes of heterogeneity in the published literature.

MATERIALS AND METHODS

Original studies reporting the incidence of TSM were identified in searches of PubMed, Embase, and Cochrane Library databases. The pooled incidence of TSM was calculated using random-effects meta-analysis of single proportions. Subgroup analyses were conducted to explore causes of heterogeneity.

RESULTS

A total of 24 studies were finally included (single arterial phase, 19 studies with 3065 subjects; multiple arterial phases, 8 studies with 2274 subjects). Studies using single arterial phase imaging reported individual TSM rates varying from 4.8% to 26.7% and a pooled incidence of TSM of 13.0% (95% confidence interval, 10.3%-16.2%), which showed substantial study heterogeneity. The pooled incidence of TSM in the studies using multiple arterial phase imaging was 3.2% (95% confidence interval, 1.9%-5.2%), which was significantly less than in those studies using single arterial phase imaging (P < 0.001). In the subgroup analysis, the geographical region of studies and the definition of TSM were found to be causes of heterogeneity. The incidence of TSM was higher in studies with Western populations from Europe or North America than in those with Eastern (Asia/Pacific) populations (16.0% vs 8.8%, P = 0.005). Regarding the definition of TSM, the incidence of TSM was higher when a 4-point scale was used for its categorization than when a 5-point scale was used (20.0% vs 11.0%, P = 0.008), and a definition considering motion artifact on phases other than arterial phase imaging lowered the incidence of TSM compared with it being defined only on arterial phase imaging (11.3% vs 20.3%, P = 0.018).

CONCLUSIONS

The incidence of TSM on arterial phase images varied across studies and was associated with the geographical region of studies and the definition of TSM. Careful interpretation of results reporting TSM might therefore be needed.

Quantitative Multiparametric MRI as an Imaging Biomarker for the Prediction of Breast Cancer Receptor Status and Molecular Subtypes

Objectives

To assess breast cancer receptor status and molecular subtypes by using the CAIPIRINHA-Dixon-TWIST-VIBE and readout-segmented echo-planar diffusion weighted imaging techniques.

Methods

A total of 165 breast cancer patients were retrospectively recruited. Patient age, estrogen receptor, progesterone receptor, human epidermal growth factorreceptor-2 (HER-2) status, and the Ki-67 proliferation index were collected for analysis. Quantitative parameters (K^trans, V_e, K_ep), semiquantitative parameters (W_-in, W_-out, TTP), and apparent diffusion coefficient (ADC) values were compared in relation to breast cancer receptor status and molecular subtypes. Statistical analysis were performed to compare the parameters in the receptor status and molecular subtype groups.Multivariate analysis was performed to explore confounder-adjusted associations, and receiver operating characteristic curve analysis was used to assess the classification performance and calculate thresholds.

Results

Younger age (<49.5 years, odds ratio (OR) =0.95, P=0.004), lower K_ep (<0.704,OR=0.14, P=0.044),and higher TTP (>0.629 min, OR=24.65, P=0.011) were independently associated with progesterone receptor positivity. A higher TTP (>0.585 min, OR=28.19, P=0.01) was independently associated with estrogen receptor positivity. Higher K_ep (>0.892, OR=11.6, P=0.047), lower TTP (<0.582 min, OR<0.001, P=0.004), and lower ADC (<0.719 ×10^-3 mm²/s, OR<0.001, P=0.048) had stronger independent associations with triple-negative breast cancer (TNBC) compared to luminal A, and those parameters could differentiate TNBC from luminal A with the highest AUC of 0.811.

Conclusions

K_ep and TTP were independently associated with hormone receptor status. In addition, the K_ep, TTP, and ADC values had stronger independent associations with TNBC than with luminal A and could be used as imaging biomarkers for differentiate TNBC from Luminal A.

Transient Respiratory-motion Artifact and Scan Timing during the Arterial Phase of Gadoxetate Disodium-enhanced MR Imaging: The Benefit of Shortened Acquisition and Multiple Arterial Phase Acquisition

Purpose:

To investigate whether shortened acquisition or multiple arterial phase acquisition improves image quality of the arterial phase compared with conventional protocol.

Methods:

This retrospective study was approved by the relevant Institutional Review Board. A total of 615 consecutive patients who underwent gadoxetate disodium-enhanced MRI including one of the following three sequences in three different periods were included: (i) conventional liver acquisition with volume acceleration (LAVA) (between October 2014 and January 2015, n = 149), (ii) Turbo-LAVA (between March and August 2016, n = 216), and (iii) differential sub-sampling with Cartesian ordering (DISCO) (between January and September 2015, n = 250). We monitored the respiratory bellows waveform during breath holding for each patient and recorded breath-hold fidelity of the patients. Two radiologists independently evaluated the degree of respiratory artifact and scan timing on the arterial phase and compared them between the three protocols (i.e., conventional LAVA, Turbo-LAVA, and DISCO), with conventional LAVA as control.

Results:

The ratio of patients with breath-hold failure was not significantly different among the three protocols (P = 0.6340 and 0.1085). Respiratory artifact was significantly lower in DISCO than in conventional LAVA (P = 0.0424), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.2593). The ratio of adequate scan timing and diagnosable image defined as no or mild artifact and adequate scan timing were higher in DISCO than in conventional LAVA (P = 0.0025 and 0.0019), while there was no significant difference between Turbo-LAVA and conventional LAVA (P = 0.0780 and 0.0657).

Conclusion:

Compared with conventional protocol, multiple arterial phase acquisition (DISCO) obtained a higher number of diagnosable images by reducing respiratory motion artifact and optimizing the scan timing of arterial phase.

Three-Dimensional Printed Anatomic Models Derived From Magnetic Resonance Imaging Data: Current State and Image Acquisition Recommendations for Appropriate Clinical Scenarios

Three-dimensional (3D) printing technologies have been increasingly utilized in medicine over the past several years and can greatly facilitate surgical planning thereby improving patient outcomes. Although still much less utilized compared to computed tomography (CT), magnetic resonance imaging (MRI) is gaining traction in medical 3D printing. The purpose of this study was two-fold: 1) to determine the prevalence in the existing literature of using MRI to create 3D printed anatomic models for surgical planning and 2) to provide image acquisition recommendations for appropriate clinical scenarios where MRI is the most suitable imaging modality. The workflow for creating 3D printed anatomic models from medical imaging data is complex and involves image segmentation of the regions of interest and conversion of that data into 3D surface meshes, which are compatible with printing technologies. CT is most commonly used to create 3D printed anatomic models due to the high image quality and relative ease of performing image segmentation from CT data. As compared to CT datasets, 3D printing using MRI data offers advantages since it provides exquisite soft tissue contrast needed for accurate organ segmentation and it does not expose patients to unnecessary ionizing radiation. MRI, however, often requires complicated imaging techniques and time-consuming postprocessing procedures to generate high-resolution 3D anatomic models needed for 3D printing. Despite these challenges, 3D modeling and printing from MRI data holds great clinical promises thanks to emerging innovations in both advanced MRI imaging and postprocessing techniques. EVIDENCE LEVEL: 2 TECHNICAL EFFICATCY: 5.

Diagnostic Confidence and Feasibility of a Deep Learning Accelerated HASTE Sequence of the Abdomen in a Single Breath-Hold

OBJECTIVE

The aim of this study was to evaluate the feasibility of a single breath-hold fast half-Fourier single-shot turbo spin echo (HASTE) sequence using a deep learning reconstruction (HASTEDL) for T2-weighted magnetic resonance imaging of the abdomen as compared with 2 standard T2-weighted imaging sequences (HASTE and BLADE).

MATERIALS AND METHODS

Sixty-six patients who underwent 1.5-T liver magnetic resonance imaging were included in this monocentric, retrospective study. The following T2-weighted sequences in axial orientation and using spectral fat suppression were compared: a conventional respiratory-triggered BLADE sequence (time of acquisition [TA] = 4:00 minutes), a conventional multiple breath-hold HASTE sequence (HASTES) (TA = 1:30 minutes), as well as a single breath-hold HASTE with deep learning reconstruction (HASTEDL) (TA = 0:16 minutes). Two radiologists assessed the 3 sequences regarding overall image quality, noise, sharpness, diagnostic confidence, and lesion detectability as well as lesion characterization using a Likert scale ranging from 1 to 4 with 4 being the best. Comparative analyses were conducted to assess the differences between the 3 sequences.

RESULTS

HASTEDL was successfully acquired in all patients. Overall image quality for HASTEDL was rated as good (median, 3; interquartile range, 3-4) and was significantly superior to HASTEs (P < 0.001) and inferior to BLADE (P = 0.001). Noise, sharpness, and artifacts for HASTEDL reached similar levels to BLADE (P ≤ 0.176) and were significantly superior to HASTEs (P < 0.001). Diagnostic confidence for HASTEDL was rated excellent by both readers and significantly superior to HASTEs (P < 0.001) and inferior to BLADE (P = 0.044). Lesion detectability and lesion characterization for HASTEDL reached similar levels to those of BLADE (P ≤ 0.523) and were significantly superior to HASTEs (P < 0.001). Concerning the number of detected lesions and the measured diameter of the largest lesion, no significant differences were found comparing BLADE, HASTES, and HASTEDL (P ≤ 0.912).

CONCLUSIONS

The single breath-hold HASTEDL is feasible and yields comparable image quality and diagnostic confidence to standard T2-weighted TSE BLADE and may therefore allow for a remarkable time saving in abdominal imaging.

Transient respiratory motion artifacts in multiple arterial phases on abdominal dynamic magnetic resonance imaging: a comparison using gadoxetate disodium and gadobutrol

PURPOSE

To compare the occurrence of transient respiratory motion artifacts (TRMAs) in multiple arterial phases on abdominal magnetic resonance (MR) images between those obtained using gadobutrol and gadoxetate disodium.

MATERIALS AND METHODS

Two hundred and fourteen abdominal MR examinations (101 with gadoxetate disodium, 113 with gadobutrol) were evaluated. Dynamic three-dimensional contrast-enhanced T1-weighted imaging (CAIPIRINHA-Dixon-TWIST-VIBE) including single-breath-hold six arterial phase acquisitions was performed on a 3.0-T MRI scanner. The TRMAs frequency and the mean TRMA scores were compared between patients assessed with gadoxetate disodium and those assessed with gadobutrol. In addition, the timing of TRMAs appearing for the first time was also recorded and compared between the two groups.

RESULTS

The mean TRMA scores in all arterial phases using gadoxetate disodium were significantly worse than in those using gadobutrol (1.49 ± 0.78 vs. 1.18 ± 0.53, P < .001). Regarding the timing of the occurrence of TRMAs, the severe TRMAs frequency after the third arterial phase was significantly higher in patients using gadoxetate disodium (10/101, 10%) than in those using gadobutrol (0/113, 0%) (P < .001).

CONCLUSION

In multiple-arterial-phase dynamic MRI, the TRMAs frequency when using gadoxetate disodium increased compared with gadobutrol, due to intolerable respiratory suspension after the third arterial phase.

Image quality of the CAIPIRINHA-Dixon-TWIST-VIBE technique for ultra-fast breast DCE-MRI: Comparison with the conventional GRE technique

PURPOSE

The aim of this study was to evaluate image quality of the CAIPIRINHA-Dixon-TWIST-Volume-Interpolated Breath-hold Examination (CDT-VIBE) technique for ultra-fast breast dynamic contrast enhanced (DCE) MRI with respect to conventional Gradient-Recalled Echo (GRE) technique.

METHODS

A total of 58 patients underwent a DCE-MRI based on CDT-VIBE sequence (temporal resolution: 11.9 s), immediately followed by 1 phase of a conventional T1 weighted GRE sequence (acquisition time: 68 s). The Signal-to-Noise Ratio (SNR) on phantom images, lesion/parenchyma signal ratio (LPSR), image quality, and morphological characterization were compared between the last phase of CDT-VIBE and conventional GRE images. The image quality was assessed by visual grading analysis (VGA). Reader agreement was assessed using Kappa analysis.

RESULTS

There was no significant difference in SNR (phantom) or LPSR (patient) between CDT-VIBE and conventional GRE images (P > 0.05). Significant parallel acquisition technique (PAT) noise and mild blurriness was observed on CDT-VIBE images. Visual grading analysis (VGA) confirmed significantly worse ratings for CDT-VIBE compared to the conventional GRE sequence in terms of PAT noise, lesion's internal feature clarity, and therefore overall image quality (area under contrast curve [AUC] values: 0.578 ‒ 0.764, P < 0.05), but edge sharpness and lesion conspicuity were equivalent (P > 0.05). Kappa analysis revealed good agreement on image quality scores (к = 0.725 ‒ 0.908) and on morphologic terms (к = 0.745-1.000).

CONCLUSION

The CDT-VIBE sequence provides excellent spatial resolution and adequate image quality in ultra-fast breast DCE-MRI. Further improvement in PAT noise and internal structure blurriness may be necessary.

Reduction of respiratory motion artifacts in gadoxetate-enhanced MR with a deep learning-based filter using convolutional neural network

Objectives

To reveal the utility of motion artifact reduction with convolutional neural network (MARC) in gadoxetate disodium–enhanced multi-arterial phase MRI of the liver.

Methods

This retrospective study included 192 patients (131 men, 68.7 ± 10.3 years) receiving gadoxetate disodium–enhanced liver MRI in 2017. Datasets were submitted to a newly developed filter (MARC), consisting of 7 convolutional layers, and trained on 14,190 cropped images generated from abdominal MR images. Motion artifact for training was simulated by adding periodic k-space domain noise to the images. Original and filtered images of pre-contrast and 6 arterial phases (7 image sets per patient resulting in 1344 sets in total) were evaluated regarding motion artifacts on a 4-point scale. Lesion conspicuity in original and filtered images was ranked by side-by-side comparison.

Results

Of the 1344 original image sets, motion artifact score was 2 in 597, 3 in 165, and 4 in 54 sets. MARC significantly improved image quality over all phases showing an average motion artifact score of 1.97 ± 0.72 compared to 2.53 ± 0.71 in original MR images (p < 0.001). MARC improved motion scores from 2 to 1 in 177/596 (29.65%), from 3 to 2 in 119/165 (72.12%), and from 4 to 3 in 34/54 sets (62.96%). Lesion conspicuity was significantly improved (p < 0.001) without removing anatomical details.

Conclusions

Motion artifacts and lesion conspicuity of gadoxetate disodium–enhanced arterial phase liver MRI were significantly improved by the MARC filter, especially in cases with substantial artifacts. This method can be of high clinical value in subjects with failing breath-hold in the scan.

Key Points

• This study presents a newly developed deep learning–based filter for artifact reduction using convolutional neural network (motion artifact reduction with convolutional neural network, MARC).

• MARC significantly improved MR image quality after gadoxetate disodium administration by reducing motion artifacts, especially in cases with severely degraded images.

• Postprocessing with MARC led to better lesion conspicuity without removing anatomical details.

Respiratory motion artefacts in Gd-EOB-DTPA (Primovist/Eovist) and Gd-DOTA (Dotarem)-enhanced dynamic phase liver MRI after intensified and standard pre-scan patient preparation: A bi-institutional analysis

Objective

The objective of this study is to evaluate if intensified pre-scan patient preparation (IPPP) that comprises custom-made educational material on dynamic phase imaging and supervised pre-imaging breath-hold training in addition to standard informative conversation with verbal explanation of breath-hold commands (standard pre-scan patient preparation–SPPP) might reduce the incidence of gadoxetate disodium (Gd-EOB-DTPA)-related transient severe respiratory motion (TSM) and severity of respiratory motion (RM) during dynamic phase liver MRI.

Material and methods

In this bi-institutional study 100 and 110 patients who received Gd-EOB-DTPA for dynamic phase liver MRI were allocated to either IPPP or SPPP at site A and B. The control group comprised 202 patients who received gadoterate meglumine (Gd-DOTA) of which each 101 patients were allocated to IPPP or SPPP at site B. RM artefacts were scored retrospectively in dynamic phase images (1: none– 5: extensive) by five and two blinded readers at site A and B, respectively, and in the hepatobiliary phase of the Gd-EOB-DTPA-enhanced scans by two blinded readers at either site.

Results

The incidence of TSM was 15% at site A and 22.7% at site B (p = 0.157). IPPP did not reduce the incidence of TSM in comparison to SPPP: 16.7% vs. 21.6% (p = 0.366). This finding was consistent at site A: 12% vs. 18% (p = 0.401) and site B: 20.6% vs. 25% (p = 0.590). The TSM incidence in patients with IPPP and SPPP did not differ significantly between both sites (p = 0.227; p = 0.390). IPPP did not significantly mitigate RM in comparison to SPPP in any of the Gd-EOB-DTPA-enhanced dynamic phases and the hepatobiliary phase in patients without TSM (all p≥0.072). In the Gd-DOTA control group on the other hand, IPPP significantly mitigated RM in all dynamic phases in comparison to SPPP (all p≤0.031).

Conclusions

We conclude that Gd-EOB-DTPA-related TSM cannot be mitigated by education and training and that Gd-EOB-DTPA-related breath-hold difficulty does not only affect the subgroup of patients with TSM or exclusively the arterial phase as previously proposed.

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.

Intravenous gadolinium-based hepatocyte-specific contrast agents (HSCAs) for contrast-enhanced liver magnetic resonance imaging in pediatric patients: what the radiologist should know

Hepatocyte-specific contrast agents (HSCAs) are a group of intravenous gadolinium-based MRI contrast agents that can be used to characterize hepatobiliary pathology. The mechanism by which these agents are taken up by hepatocytes and partially excreted into the biliary tree improves characterization of hepatic lesions and biliary abnormalities relative to conventional extracellular gadolinium-based contrast agents (GBCAs). This manuscript presents an overview of HSCA use in pediatric patients with the intent to provide radiologists a guide for clinical use. We review available HSCAs and discuss dosing and age specifications for use in children. We also review various hepatic and biliary indications for HSCA use in children, with emphasis on the imaging characteristics distinct to HSCAs, as well as discussion of pitfalls one can encounter when imaging with HSCAs. Given the growing concern regarding gadolinium deposition in soft tissues and brain, we also discuss safety of HSCA use in children.

Whole-lesion histogram and texture analyses of breast lesions on inline quantitative DCE mapping with CAIPIRINHA-Dixon-TWIST-VIBE

PURPOSE

To investigate the diagnostic capability of whole-lesion (WL) histogram and texture analysis of dynamic contrast-enhanced (DCE) MRI inline-generated quantitative parametric maps using CAIPIRINHA-Dixon-TWIST-VIBE (CDTV) to differentiate malignant from benign breast lesions and breast cancer subtypes.

MATERIALS AND METHODS

From February 2018 to November 2018, DCE MRI using CDTV was performed on 211 patients. The inline-generated parametric maps included K^trans, k_ep, V_e, and IAUGC₆₀. Histogram and texture features were extracted from the above parametric maps respectively based on a WL analysis. Student's t tests, one-way ANOVAs, Mann-Whitney U tests, Jonckheere-Terpstra tests, and ROC curves were used for statistical analysis.

RESULTS

Compared with benign breast lesions, malignant breast lesions showed significantly higher K^trans_{_median, 5th percentile, entropy, and diff-entropy}, IAUGC_{60_median, 5th percentile, entropy, and diff-entropy}, k_{ep_mean, median, 5th percentile, entropy, and diff-entropy}, and V_{e_95th percentile, diff-variance, and contrast}, and significantly lower k_{ep_skewness} and V_{e_SD, entropy, diff-entropy, and skewness} (all p ≤ 0.011). The combination of all the extracted parameters yielded an AUC of 0.85 (sensitivity 76%, specificity 86%). k_{ep_contrast} showed a significant difference among different subtypes of breast cancer (p = 0.006). k_{ep_skewness} showed a significant difference between lymph node-positive and lymph node-negative breast cancer (p = 0.007). The IAGC_{60_5th percentile} had an AUC of 0.71 (sensitivity 50%, specificity 91%) for differentiating between high- and low-proliferation groups of breast cancer.

CONCLUSIONS

The WL histogram and texture analyses of CDTV-DCE-derived parameters may give additional information for further evaluation of breast cancer.

KEY POINTS

• Inline DCE mapping with CDTV is effective and time-saving. • WL histogram and texture-extracted features could distinguish breast cancer from benign lesions accurately. • k_{ep_contrast}, k_{ep_skewness}, and IAUGC_{60_5th percentile} could predict breast cancer subtypes, lymph node metastasis, and proliferation abilities, respectively.

Modified CAIPIRINHA-VIBE without view-sharing on gadoxetic acid-enhanced multi-arterial phase MR imaging for diagnosing hepatocellular carcinoma: comparison with the CAIPIRINHA-Dixon-TWIST-VIBE

PURPOSE

We evaluated the detection rate and degree of motion artifact of the modified CAIPIRINHA-VIBE (mC-VIBE) without view-sharing and compare them with the CAIPIRINHA-Dixon-TWIST-VIBE (CDT-VIBE) with view-sharing on multi-arterial gadoxetic acid-enhanced liver MRI in the assessment of hepatocellular carcinoma (HCC).

MATERIAL AND METHODS

We retrospectively identified 114 pathological-proven hepatic tumors in 114 patients with risk of HCC who underwent multi-arterial gadoxetic acid-enhanced MRI between June 2016 and June 2018. All patients underwent triple arterial phase imaging using the mC-VIBE without view-sharing (54 patients; 49 HCCs and 5 non-HCCs) or the CDT-VIBE with view-sharing (60 patients; 55 HCCs and 5 non-HCCs). We compared the detection rate of two sequences for HCC, with reference to LI-RADS.V.2017. We also compared the mean motion scores and proportions of transient severe motion (TSM) in two sequences.

RESULT

For the examination using the mC-VIBE, the HCC-detection rate was significantly higher, compared with that using CDT-VIBE (93.9% [46/49] vs 80.0% [44/55], respectively; p = 0.047). For the examination with the mC-VIBE, mean motion scores were significantly lower compared with those of CDT-VIBE for all multi-arterial phases (1.21, 1.19, and 1.15 vs. 1.82, 1.85, and 1.84, respectively; p < 0.001 for all three comparisons). The proportion of TSM in the CDT-VIBE was significantly higher than that in the mC-VIBE (15.0% [9/60] vs 0.0% [0/54], respectively; p = 0.003).

CONCLUSION

In multi-arterial phase gadoxetic acid-enhanced MRI, the mC-VIBE sequence without view-sharing has slightly higher HCC-detection rate and fewer motion artifacts compared with CDT-VIBE with view-sharing.

KEY POINTS

• Multi-arterial phase using the mC-VIBE without view-sharing can overcome motion artifacts, resulting in providing optimal arterial phase imaging. • The HCC-detection rate is slightly higher with the mC-VIBE vs. CAIPIRINHA-Dixon-TWIST-VIBE with view-sharing (CDT-VIBE). • View-sharing of CDT-VIBE in the multi-arterial phase is associated with increased frequency of TSM.