Gadolinium-enhanced MR imaging of the liver: optimizing imaging delay for hepatic arterial and portal venous phases--a prospective randomized study in patients with chronic liver damage

Automatic discrimination of different sequences and phases of liver MRI using a dense feature fusion neural network: a preliminary study

PURPOSE

To develop and validate a dense feature fusion neural network (DFuNN) to automatically recognize different sequences and phases of liver magnetic resonance imaging (MRI).

MATERIALS AND METHODS

In total, 3869 sequences and phases from 384 liver MRI examinations, divided into training/validation (n = 2886 sequences from 287 patients) and test (n = 983 sequences from 97 patients) sets, were used in this retrospective study. Ten unenhanced sequences and enhanced phases were included. Manual sequence recognition, performed by two radiologists (20 and 10 years of experience) in a consensus reading, was used as the reference standard. The sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of the DFuNN on an identical unseen test set. Finally, we evaluated the factors impacting the model precision.

RESULTS

A fusion block improved the performance of the DFuNN. DFuNN with a fusion block achieved good recognition performance for both complete and incomplete sequences and phases in the test set. The average sensitivity of recognition performance for complete sequence and phase inputs ranged from 88.06 to 100%, the average specificity ranged from 99.12 to 99.94%, and the median accuracy ranged from 98.02 to 99.95%. The DFuNN prediction accuracy for patients without cirrhosis were significantly higher than those for patients with cirrhosis (P = 0.0153). No significant difference was found in the accuracy across other factors.

CONCLUSION

DFuNN can automatically and accurately identify specific unenhanced MRI sequences and enhanced MRI phases.

Intra-individual comparison of dual portal venous phases for non-invasive diagnosis of hepatocellular carcinoma at gadoxetic acid-enhanced liver MRI

OBJECTIVES

To compare the diagnostic performances of first and second portal venous phases (PVP1 and PVP2) in revealing washout and capsule appearance for non-invasive HCC diagnoses in gadoxetic acid-enhanced MRI (Gd-EOB-MRI).

METHODS

This retrospective study included 123 at-risk patients with 160 hepatic observations (HCCs, n = 116; non-HCC malignancies, n = 18; benign, n = 26) showing arterial phase hyper-enhancement (APHE) ≥ 1 cm at Gd-EOB-MRI. The mean time intervals from gadoxetic acid injection to PVP1 and PVP2 acquisitions were 53 ± 2 s and 73 ± 3 s, respectively. After evaluating image findings independently, imaging findings and diagnoses were finalized by a consensus of two radiologists using either PVP1 or PVP2 image sets according to the LI-RADS v2018 or EASL criteria. Sensitivity, specificity, and accuracy were compared.

RESULTS

Among HCCs, more washout and enhancing capsule were observed in PVP2 (83.6% and 27.6%) than in PVP1 (50.9% and 19.8%) (p < 0.001, both). The PVP2 set presented significantly higher sensitivity (83.6% vs. 53.5%, LI-RADS; 82.8% vs. 50.0%, EASL; p < 0.001, both) and accuracy (0.88 vs. 0.73, LI-RADS; 0.88 vs. 0.72, EASL; p < 0.001, both) than the PVP1 set without significant specificity loss (93.2% vs. 93.2%, by LI-RADS or EASL; p = 0.32, both). None of the non-HCC malignancy was non-invasively diagnosed as HCC in both PVP image sets.

CONCLUSION

Late acquisition of PVP detected washout and enhancing capsule of HCC more sensitively than early acquisition, enabling accurate diagnoses of HCC, according to LI-RADS or EASL criteria.

KEY POINTS

• Among HCCs, more washout and enhancing capsules were observed in PVP2 than PVP1, quantitatively and qualitatively. • The portal venous phase acquired at around 70 s after contrast media administration (PVP2) provided significantly higher sensitivity and AUC value than PVP1 by using LI-RADS v2018 or EASL criteria. • More HCCs were categorized as LR-5 in PVP2 than in PVP1 images, and the specificity of PVP2 (93.5%) was comparable with PVP1 (93.5%).

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.

Surrogate arterial phase imaging using a long duration (≈1.5 min) radial acquisition T1-weighted sequence: an alternative in patients unable to breath-hold

BACKGROUND

Pediatric and adult patients unable to suspend respiration generally undergo magnetic resonance (MR) examinations that lack arterial phase imaging, which is a phase that provides substantial information on disease processes. An MR strategy that provides this type of information may be of considerable value.

PURPOSE

To describe and assess the feasibility and enhancement quality of early-phase imaging utilizing long-duration radial 3D-GRE imaging by initiating the sequence prior to starting contrast injection.

MATERIAL AND METHODS

Thirty-three consecutive patients (10 men, 23 women; 50.7 ± 25.5 years) underwent free-breathing gadolinium-enhanced radial 3D-GRE, with sequence initiation 30 s prior to contrast injection. Late hepatic arterial (LHA) phase was chosen for comparison. Images were evaluated for enhancement and overall image quality. Organ enhancement was calculated. Sub-group analysis was performed.

RESULTS

Twenty-two examinations of radial 3D-GRE sequences were acquired during the LHA phase. Organ enhancement scores were of satisfactory to good quality (range, 3.32-3.82). There was a significant trend of superior overall enhancement quality scores in pediatrics and examinations performed at 3 T (P = 0.0225 and 0.0001, respectively).

CONCLUSION

Arterial phase abdominal MR imaging is feasible using conventional radial 3D-GRE by adopting this simplistic proposed approach, which may allow arterial-phase imaging in patients unable to breath-hold.

Application of direct virtual coil to dynamic contrast-enhanced MRI and MR angiography with data-driven parallel imaging

PURPOSE

To demonstrate the feasibility of direct virtual coil (DVC) in the setting of 4D dynamic imaging used in multiple clinical applications.

THEORY AND METHODS

Three dynamic imaging applications were chosen: pulmonary perfusion, liver perfusion, and peripheral MR angiography (MRA), with 18, 11, and 10 subjects, respectively. After view-sharing, the k-space data were reconstructed twice: once with channel-by-channel (CBC) followed by sum-of-squares coil combination and once with DVC. Images reconstructed using CBC and DVC were compared and scored based on overall image quality by two experienced radiologists using a five-point scale.

RESULTS

The CBC and DVC showed similar image quality in image domain. Time course measurements also showed good agreement in the temporal domain. CBC and DVC images were scored as equivalent for all pulmonary perfusion cases, all liver perfusion cases, and four of the 10 peripheral MRA cases. For the remaining six peripheral MRA cases, DVC were scored as slightly better (not clinically significant) than the CBC images by Radiologist A and as equivalent by Radiologist B.

CONCLUSION

For dynamic contrast-enhanced MR applications, it is clinically feasible to reduce image reconstruction time while maintaining image quality and time course measurement using the DVC technique.

Optimizing Liver Magnetic Resonance Imaging: Does Intuitive Protocol Management Software Save Time and Produce Better Scans than Manually Optimized Protocols?

PURPOSE

The purpose of this study is to determine if a software package (Abdomen DOT; Siemens Medical Systems, Erlangen Germany) designed to automate magnetic resonance imaging (MRI) scans of the liver results in faster and higher quality examinations compared to optimized protocols performed by appropriately trained technologists.

MATERIALS AND METHODS

One hundred eight liver MRIs obtained using Abdomen DOT and 94 liver MRIs obtained without Abdomen DOT were retrospectively reviewed. Total scan time and the number of repeated sequences were objectively measured. Timing of the arterial phase, motion artifact, and quality of subtraction images were subjectively evaluated.

RESULTS

The examinations scanned using Abdomen DOT averaged 2 minutes and 2 seconds shorter than the examinations scanned without Abdomen DOT (P = 0.004) and on average, fewer sequences were repeated. The arterial phase was timed correctly 67% (63/94) of the time without using Abdomen DOT and 81% (87/108) of the time when using Abdomen DOT (P = 0.019). There was no difference in the amount of respiratory artifact. The subtraction images obtained using Abdomen DOT were considered slightly better (P < 0.005 for arterial, portal venous, and equilibrium phase images).

CONCLUSIONS

The Abdomen DOT software helped our technologists scan slightly faster and obtain correctly timed arterial phase images more often.

Evaluation of image quality, radiation dose and diagnostic performance of dual-energy CT datasets in patients with hepatocellular carcinoma

AIM

To evaluate image quality and diagnostic accuracy of different dual-energy computed tomography (DECT) datasets for identification of hepatocellular carcinoma (HCC), assess the reliability of virtual unenhanced (VU) images in replacing standard unenhanced (SU) images, and quantify effective dose (ED) at different tube voltages.

MATERIAL AND METHODS

Thirty cirrhotic patients underwent liver contrast-enhanced DECT. Two blinded observers retrospectively evaluated conventional unenhanced and VU images, 140 kVp/80 kVp/mixed tube potential arterial datasets and conventional portal-venous/late phases in consensus. Final diagnosis was based on pathological proof or imaging criteria. Image quality, ED, sensitivity, and specificity of arterial datasets were calculated.

RESULTS

Thirty-eight HCC and 18 benign lesions were detected at 80 kVp, 33 HCC and 22 benign lesions were detected at 140 kVp, and 36 HCC and 20 benign lesions were detected at mixed tube potentials. Final diagnosis confirmed 37 HCC and 20 benign lesions. There was no significant difference in diagnostic confidence between 80 kVp, 140 kVp, and mixed tube potential arterial datasets (p>0.05). Image quality was adequate for all datasets, with increased quality at higher tube potential (80 versus 140 kVp, p=0.001; mixed versus 140 kVp, p=0.001; 80 kVp versus mixed, p=0.0024). Significant ED reduction was observed between 140 and 80 kVp datasets (p<0.001).

CONCLUSIONS

The 140 kVp dataset provided higher image quality. The 80 kVp images were more sensitive in detecting HCC. VU images are adequate in replacing SU images. The ED of the 80 kVp dataset was significantly lower.

Detection of small (≤2 cm) HCC in cirrhotic patients: added value of diffusion MR-imaging

OBJECTIVES

To evaluate the usefulness of the diffusion-weighted sequence in the detection of small (≤2 cm) hepatocellular carcinoma (HCC) in patients with cirrhosis.

METHODS

Seventy cirrhotic patients with 93 HCCs underwent MR-Imaging at 1.5 T. MR acquisitions comprised unenhanced T1- and T2-weighted images and post-contrast Gd-BOPTA-enhanced T1W GRE-3D images acquired after approximately 25, 60, 180 s (dynamic phases) and 90 min (hepatobiliary phase). DWI was performed by a SSEPI sequence (b values 0, 50, 400, 800 s/mm(2)). Quantitative analysis was performed to establish significant difference of ADC values of benign lesions compared with that of HCC. Sensitivity, specificity, positive and negative predictive values and diagnostic accuracy of two different protocols with and without diffusion MRI sequence were also calculated and compared each other.

RESULTS

A good inverse correlation was found between reference standard and ADC values (ρ = -0.688). The mean ADC value of HCC was significantly lower than the mean value of benign focal liver lesions (p < 0.0001). No significant difference was reported in term of sensitivity, specificity, PPV, NPV and diagnostic accuracy between the two datasets. A trend to a better sensitivity was found when DWI images were considered.

CONCLUSIONS

The adjunction of DWI does not significantly improve the diagnostic accuracy in the detection of small HCC.

Performance of magnetic resonance elastography and diffusion-weighted imaging for the staging of hepatic fibrosis: A meta-analysis

A meta-analysis was performed to assess and compare the accuracies of magnetic resonance elastography (MRE) and diffusion-weighted imaging (DWI) for the staging of hepatic fibrosis. Online journal databases and a manual search from January 2000 to May 2011 were used. We identified 41 studies, but only 14 met the criteria to perform a meta-analysis assessing MRE (five trials) or DWI (10 trials). Fibrosis was categorized by redistribution into five stages according to histopathological description. A bivariate binomial model was used to combine the sensitivity and specificity and their 95% confidence intervals (CIs), from which diagnostic odds ratio (DOR), positive likelihood ratio (PLR), negative likelihood ratio (NLR), and summary receiver operating characteristic (sROC) were derived to indicate the diagnostic accuracy of imaging modalities. With MRE, the sensitivity, specificity, DOR, PLR, NLR, and area under sROC curve (with 95% CIs) for staging F0 ∼ F1 versus F2 ∼ F4 and F0 ∼ F2 versus F3 ∼ F4 were 0.94 (0.81-0.98), 0.95 (0.87-0.98), 20 (7-57), 0.06 (0.02-0.22), 317 (55-1,796), 0.98 (0.97-0.99) and 0.92 (0.85-0.96), 0.96 (0.91-0.98), 21 (10-45), 0.08 (0.04-0.16), 251 (103-609), and 0.98 (0.96-0.99), respectively; and with DWI, these values were 0.77 (0.71-0.82), 0.78 (0.69-0.85), 3 (2-5), 0.30 (0.22-0.40), 12 (6-21), 0.83 (0.79-0.86) and 0.72 (0.60-0.81), 0.84 (0.77-0.89), 5 (3-7), 0.34 (0.23-0.50), 13 (6-29), and 0.86 (0.83-0.89), respectively. A z test demonstrated that MRE had a significantly higher accuracy than DWI in those indicators (P < 0.05).

CONCLUSION

MRE is more reliable for staging hepatic fibrosis, compared with DWI, with a high combination of sensitivity, specificity, likelihood ratios, DOR, and area under sROC curve.

3 T MRI of hepatocellular carcinomas in patients with cirrhosis: does T2-weighted imaging provide added value?

AIM

To assess whether T2-weighted imaging (T2WI) provides any added value for the detection of hepatocellular carcinoma (HCC) in patients with cirrhosis, especially for lesions smaller than 2 cm.

MATERIALS AND METHODS

Sixty-five patients with cirrhosis underwent liver 3 T MRI. Images were qualitatively analysed independently by two observers in two separate sessions, including a dynamic enhanced session and a combination of dynamic and T2WI. The diagnostic accuracy was evaluated using the alternating free-response receiver operating characteristic. Sensitivity and positive predictive values were calculated for all HCCs and for the subgroup of HCCs that were smaller than 2 cm. Additionally, artefacts on T2WI were evaluated by two observers in consensus.

RESULTS

Ninety HCCs (>2 cm n = 36; ≤2 cm n = 54) were detected in 46 patients. For all HCCs and for lesions smaller than 2 cm, the sensitivities were significantly higher for the combined session than the dynamic session alone (p < 0.05). Conversely, for the Az and positive predictive values, there was no significant difference between the two sessions. For smaller HCC, 9% (5/54) and 7% (4/54) of the 54 HCCs were correctly interpreted by observers 1 and 2, respectively, only when T2WI was included. Three false-positive lesions (≤2 cm) were correctly diagnosed by one of the observers after combining T2WI. Conspicuity of only one large HCC was severely reduced by the artefacts from massive ascites.

CONCLUSION

At 3 T liver imaging, combining with T2WI can improve the sensitivity of detection of HCC compared with dynamic MRI alone by increasing observer confidence, especially for lesions smaller than 2 cm. Additionally, T2 image quality was not significantly affected by artefacts.

Optimal scanning protocol of arterial dominant phase for hypervascular hepatocellular carcinoma with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced MR

PURPOSE

To investigate optimal delay time of hepatic arterial phase in Gadoxetate-enhanced MR for detecting hypervascular hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Forty-five patients with 85 hypervascular HCCs and 9 patients with 16 hypervascular HCCs underwent Gadoxetate- and Gd-DTPA-enhanced MR at 1.5 Tesla (T) system, respectively. All HCCs were analyzed 10-38 s after injection using a time-resolved dynamic MR sequence with keyhole data sampling. Seven sequential phase images (1 phase = 4 s) were obtained during a single breath hold of 28 s. Time-intensity curves of the abdominal aorta, liver parenchyma, and HCC were obtained, then aortic contrast arrival time, time of peak HCC enhancement, duration time of HCC and aortic enhancement, and time delay from aortic contrast arrival to peak enhancement of HCC were measured.

RESULTS

Aortic contrast arrival time was 15.1 ± 2.9 s, time of peak HCC enhancement 29.9 ± 4.6 s, duration time of HCC enhancement 17.4 ± 6.4 s postinjection of Gadoxetate. Duration of aortic enhancement (23.6 ± 3.5 s) of Gadoxetate-enhanced MR was significantly less than that of Gd-DTPA-enhanced MR (26.3 ± 2.8 s) (P < 0.0059).

CONCLUSION

Peak enhancement time of HCC on Gadoxetate-enhanced MR imaging occurred at 14.6 ± 4.6 s after aortic contrast arrival.

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.

Optimization of single injection liver arterial phase gadolinium enhanced MRI using bolus track real-time imaging

PURPOSE

To measure contrast agent enhancement kinetics in the liver and to further evaluate and develop an optimized gadolinium enhanced MRI using a single injection real-time bolus-tracking method for reproducible imaging of the transient arterial-phase.

MATERIALS AND METHODS

A total of 18 subjects with hypervascular liver lesions were imaged with four dimensional (4D) perfusion scans to measure time-to-peak (TTP) delays of arterial (aorta-celiac axis), liver parenchyma, liver lesion, portal, and hepatic veins. Time delays were calculated from the TTP-aorta signal, and then related to the gradient echo (GRE) k-space acquisition design, to determine optimized timing for real-time bolus-track triggering methodology. As another measure of significance, 200 clinical patients were imaged with 3D-GRE using either a fixed time-interval or by individualized arterial bolus real-time triggering. Bolus TTP-aorta was calculated and arterial-phase acquisitions were compared for accuracy and reproducibility using specific vascular enhancement indicators.

RESULTS

The mean bolus transit-time to peak-lesion contrast was 8.1 ± 2.7 seconds following arterial detection, compared to 32.1 ± 5.4 seconds from contrast injection, representing a 62.1% reduction in the time-variability among subjects (N = 18). The real-time bolus-triggered technique more consistently captured the targeted arterial phase (94%), compared to the fixed timing technique (73%), representing an expected improvement of timing accuracy in 28% of patients (P = 0.0001389).

CONCLUSION

Our results show detailed timing window analysis required for optimized arterial real-time bolus-triggering acquisition of transient arterial phase features of liver lesions, with optimized arterial triggering expected to improve reproducibility in a significant number of patients.

Intraindividual comparison of gadoxetate disodium-enhanced MR imaging and 64-section multidetector CT in the Detection of hepatocellular carcinoma in patients with cirrhosis

PURPOSE

To prospectively compare gadoxetate disodium-enhanced magnetic resonance (MR) imaging with multiphasic 64-section multidetector computed tomography (CT) in the detection of hepatocellular carcinoma (HCC) in patients with cirrhosis.

MATERIALS AND METHODS

Institutional review board approval and informed patient consent were obtained for this prospective study. Fifty-eight patients (39 men, 19 women; mean age, 63 years; age range, 35-84 years) underwent gadoxetate disodium-enhanced MR imaging and multiphasic 64-section multidetector CT. The imaging examinations were performed within 30 days of each other. The two sets of images were qualitatively analyzed in random order by three independent readers in a blinded and retrospective fashion. Using strict diagnostic criteria for HCC, readers classified all detected lesions with use of a four-point confidence scale. The reference standard was a combination of pathologic proof, conclusive imaging findings, and substantial tumor growth at follow-up CT or MR imaging (range of follow-up, 90-370 days). The diagnostic accuracy, sensitivity, and positive predictive value were compared between the two image sets. Interreader variability was assessed. The accuracy of each imaging method was determined by using an adjusted modified chi(2) test.

RESULTS

Eighty-seven HCCs (mean size +/- standard deviation, 1.8 cm +/- 1.5; range, 0.3-7.0 cm) were confirmed in 42 of the 58 patients. Regardless of lesion size, the average diagnostic accuracy and sensitivity for all readers were significantly greater with gadoxetate disodium-enhanced MR imaging (average diagnostic accuracy: 0.88, 95% confidence interval [CI]: 0.80, 0.97; average sensitivity: 0.85, 95% CI: 0.74, 0.96) than with multidetector CT (average diagnostic accuracy: 0.74, 95% CI: 0.65, 0.82; average sensitivity: 0.69, 95% CI: 0.59, 0.79) (P < .001 for each). No significant difference in positive predictive value was observed between the two image sets for each reader. Interreader agreement was good to excellent.

CONCLUSION

Compared with multiphasic 64-section multidetector CT, gadoxetate disodium-enhanced MR imaging yields significantly higher diagnostic accuracy and sensitivity in the detection of HCC in patients with cirrhosis.

Characterisation of small hypoattenuating hepatic lesions in multi-detector CT (MDCT) in patients with underlying extrahepatic malignancy: added value of contrast-enhanced MR images

OBJECTIVE

To retrospectively assess the value of adding gadolinium-enhanced dynamic imaging to standard ununenhanced magnetic resonance imaging (MRI) for characterising hypoattenuating hepatic lesions that are too small to characterise with multi-detector computed tomography (MDCT).

METHODS

Informed consent was waved, and institutional review board approval was obtained. Three hundred and forty-six small (≤ 2 cm) lesions (63 metastatic, 283 benign) in 183 patients with underlying carcinoma who underwent hepatic MRI after CT were retrospectively analysed. Two radiologists independently reviewed images and diagnoses were graded on an ordinal scale from 1 (definitely benign) to 5 (definitely malignant). Receiver operating characteristic analysis was used. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy were also determined.

RESULTS

The areas under the curve of the ununenhanced images alone and with dynamic images were 0.837 and 0.850 for reader 1 (p = 0.616) and 0.771 and 0.783 for reader 2 (p = 0.700). Descriptive statistical values demonstrated sensitivities of 76% and 80%, specificities of 93% and 95%, PPVs of 69% and 79%, NPVs of 95% and 95% and accuracies of 90% and 92%, respectively.

CONCLUSION

The value of adding three-phase contrast-enhanced MRI to unenhanced imaging did not reach statistical significance for characterising small hypoattenuating hepatic lesions on MDCT.

MRI and S-MRCP findings in patients with suspected chronic pancreatitis: correlation with endoscopic pancreatic function testing (ePFT)

PURPOSE

To review magnetic resonance imaging (MRI) and secretin stimulated magnetic resonance cholangiopancreatography (S-MRCP) findings of patients with suspected chronic pancreatitis and compare them with endoscopic pancreatic function testing (ePFT).

MATERIALS AND METHODS

MRI and S-MRCP findings of 36 patients with clinically suspected chronic pancreatitis were reviewed. Baseline ductal changes, duodenal filling grades, and pancreatic duct caliber change (PDC) on S-MRCP, mean values of pancreatic anteroposterior (AP) diameter, signal intensity ratio (SIR) between pancreas and the spleen on T1-weighted fat saturated images, and arterial to venous (A/V) enhancement ratios were compared between groups of normal and abnormal pancreatic exocrine function determined by ePFT.

RESULTS

All patients (n = 24) with normal ePFT (HCO(3) >80 mEq/L) had grade 3 normal duodenal filling. Patients with abnormal ePFT (HCO(3) <80 mEq/L) (n = 12) had grade 1 (n = 1) and grade 2 (n = 11) diminished duodenal filling (P < 0.0001). PDC was 1.51 in the normal ePFT group versus 1.27 in the abnormal ePFT group (P = 0.01). No significant differences were found in terms of mean pancreatic AP diameter (21.8 vs. 19.8 cm), SIR (1.59 vs. 1.44), and A/V (1.08 vs. 1.01) between groups of normal/abnormal pancreatic exocrine function.

CONCLUSION

Despite discrepancies between pancreatic exocrine function and the findings on standard MRI/MRCP, the S-MRCP findings are comparable to ePFT in the evaluation of chronic pancreatitis.

Gadolinium-enhanced imaging of liver tumors and manifestations of hepatitis: pharmacodynamic and technical considerations

The ability for contrast-enhanced magnetic resonance imaging to provide significant diagnostic impact to focal and diffuse liver diseases requires knowledge, analysis, and technical optimization of the imaging techniques. Our review outlines the technical requirements needed to perform reproducible contrast-enhanced liver imaging and describes the important imaging features for assessing liver disease with conventional and alternate gadolinium-based contrast media. We present an experimental review of timing and quantification methods in dynamic contrast-enhanced liver imaging, with results of analysis showing perfusion and uptake curves in a series of patients and healthy subjects. An evidence-based methodology for reproducible arterial-phase imaging is detailed for performing a real-time bolus-tracking method. Additional diagnostic imaging features manifest at later imaging phases, in which the kinetic behavior of the contrast media serves to further specify focal lesions, while revealing detailed information of diffuse liver disease, particularly hepatic fibrosis. We review the utility of alternate gadolinium-based contrast media that undergo hepatocyte uptake, for applications related to liver tumor imaging. We also introduce results showing the potential for using alternate hepatocyte uptake agents to detect and quantify liver changes related to acute and chronic hepatitides.

Focal liver lesions: detection and characterization at double-contrast liver MR Imaging with ferucarbotran and gadobutrol versus single-contrast liver MR imaging

PURPOSE

To retrospectively compare, in a multiobserver study, double-contrast-material (sequential administration of ferucarbotran and gadobutrol) magnetic resonance (MR) imaging with single-contrast-material ferucarbotran-enhanced and dynamic postferucarbotran gadobutrol-enhanced MR imaging for the detection and characterization of benign and malignant focal liver lesions.

MATERIALS AND METHODS

This study was institutional review board approved, and the requirement for informed patient consent was waived. Eighty-nine patients with a total of 128 focal liver lesions underwent double-contrast liver MR imaging (nonenhanced, ferucarbotran-enhanced, and dynamic postferucarbotran gadobutrol-enhanced MR imaging performed during one session). Four readers independently reviewed the data sets during three reading sessions focused on focal liver lesion detection and characterization: In session 1, the nonenhanced and dynamic postferucarbotran gadobutrol-enhanced images obtained at double-contrast MR imaging were analyzed. In session 2, the nonenhanced and ferucarbotran-enhanced images were analyzed. In session 3, all MR images were analyzed together. The diagnostic performance of each MR technique and each reader was evaluated by using receiver operating characteristic (ROC) analysis; differences between postferucarbotran gadobutrol-enhanced, ferucarbotran-enhanced, and double-contrast MR imaging were assessed at Wilcoxon signed rank testing; and interreader agreement was assessed at Cohen kappa analysis. Histopathologic confirmation or an unchanged clinical course or MR finding was the reference standard.

RESULTS

The four readers' detection of the benign and malignant lesions was not significantly different (P > or = .11) between the three MR techniques. The benign and malignant focal liver lesions were differentiated with significantly higher confidence (P < or = .01) on the double-contrast (area under ROC curve [A(z)] = 0.988) and ferucarbotran-enhanced (A(z) = 0.985) MR images than on the dynamic gadobutrol-enhanced images (A(z) = 0.963). Accuracy in the diagnosis of hepatocellular carcinoma (HCC) was highest (P = .02) and confidence in the final diagnosis of HCC (P = .001) or metastasis (P = .049) was significantly higher with double-contrast imaging.

CONCLUSION

In select cases, double-contrast MR imaging can improve diagnostic accuracy and increase confidence in characterizing focal liver lesions as HCC or metastasis.

Hepatocellular carcinoma in patients with cirrhosis: qualitative comparison of gadobenate dimeglumine-enhanced MR imaging and multiphasic 64-section CT

PURPOSE

To prospectively investigate whether combined interpretation of dynamic and hepatobiliary phase magnetic resonance (MR) images can improve the accuracy of gadobenate dimeglumine-enhanced MR imaging in the detection of hepatocellular carcinoma (HCC) compared with either dynamic MR or multiphasic multidetector computed tomographic (CT) images alone.

MATERIALS AND METHODS

Institutional review board approval and informed patient consent were obtained. Fifty-two patients (39 men, 13 women; mean age, 68 years; range, 38-81 years) suspected of having HCC underwent gadobenate dimeglumine-enhanced MR imaging and multiphasic 64-section multidetector CT. Images were qualitatively analyzed independently by three observers in three separate reading sessions. The alternating free-response receiver operating characteristic (AFROC) method was used to analyze the results. Differences in sensitivity and positive predictive values were calculated at a statistical significance of P < .05.

RESULTS

A total of 67 HCCs were detected in 36 patients. The mean area under the AFROC curve (A(z)) was significantly higher for either the combined interpretation of dynamic and hepatobiliary phase MR images (A(z) = 0.95) or dynamic MR images alone (0.91) than for CT images (0.77) (P = .01 for both comparisons). The mean sensitivity of combined interpretation of MR images (0.72) was significantly higher than those of dynamic MR images alone (0.63) and multidetector CT images (0.61) (P = .008 and .001, respectively). The mean positive predictive value was not significantly different among the three imaging sets.

CONCLUSION

The combined interpretation of dynamic and hepatobiliary phase MR images improves diagnostic accuracy of gadobenate dimeglumine-enhanced MR imaging for the detection of HCC compared with either dynamic MR or multiphasic multidetector CT images alone.

Optimal acquisition delay for dynamic contrast-enhanced MRI of hypervascular hepatocellular carcinoma

OBJECTIVE

The purpose of this study was to prospectively determine the optimal acquisition delay for imaging of hypervascular hepatocellular carcinoma with multiphasic dynamic contrast-enhanced MRI.

SUBJECTS AND METHODS

One hundred twenty patients with chronic hepatic disease underwent three-phase dynamic contrast-enhanced MRI of the liver, which revealed 49 hypervascular hepatocellular carcinomas. Abdominal aortic contrast arrival time was determined with test bolus imaging. Patients were assigned to one of the following four groups according to acquisition delay determined from abdominal aortic contrast arrival time to the middle of the k-space for the early, late hepatic arterial, and portal venous phases: 0, 12, and 49 seconds (group 1); 3, 15, and 52 seconds (group 2); 6, 18, and 55 seconds (group 3); and 9, 21, and 58 seconds (group 4). Each phase of imaging took 12 seconds. Contrast enhancement in the abdominal aorta, portal vein, hepatic parenchyma, and hepatocellular carcinoma was evaluated. Peritumoral sinusoidal enhancement (i.e., coronal enhancement) also was assessed.

RESULTS

Intense enhancement of hepatocellular carcinoma with little background parenchymal enhancement occurred at 9-12 seconds (p < 0.05) after arrival of contrast material in the abdominal aorta. Hepatocellular carcinoma-to-liver contrast began to decline at 15 seconds and decreased to less than zero at 49 seconds. The conspicuity of coronal enhancement was greater 21 seconds after contrast administration than in earlier phases.

CONCLUSION

With the injection protocol used in this study, optimal acquisition delay-determined from abdominal aortic contrast arrival time to the middle of the k-space acquisition-for imaging of hypervascular hepatocellular carcinoma was 9-12, 21 or more, and 49 seconds for the early, late hepatic arterial, and portal venous phases.

Early contrast enhancement of the liver: exact description of subphases using MRI

PURPOSE

The purpose of this study was to describe the subphases of early post-contrast enhancement of the liver, using vessel enhancement patterns, and correlate these findings with enhancement patterns of abdominal organs.

MATERIALS AND METHODS

A total of 114 patients who underwent gadolinium-enhanced abdominal magnetic resonance imaging examinations constituted the final study group, of which 56 were women (age range, 3-94 years; mean, 50 years) and 58 were men (age range, 6-85 years; mean, 54 years). Early post-contrast sequences in all patients were evaluated retrospectively by two reviewers for the determination of the presence of contrast enhancement in predetermined major vessels of the abdomen and qualitative and quantitative extent of enhancement of the renal cortex, spleen, pancreas and liver. Based on the overall findings, subphases of early contrast enhancement of the liver were described and quantitative extent of enhancement of organs was correlated with subphases of early contrast enhancement of the liver. Mann-Whitney U test and one-way unbalanced analysis of variance tests were used for the comparisons.

RESULTS

Early hepatic arterial phase was observed in 14/114 patients, mid-hepatic arterial phase in 23/114 patients, late hepatic arterial phase in 33/114 patients, splenic vein only hepatic arterial dominant phase in 20/114 patients and hepatic arterial dominant phase in 24/114 patients. There was an overall association between the subphases of enhancement and the quantitative extent of enhancement for all studied organs (P<.0001).

CONCLUSION

The evaluation of vessel and organ enhancement patterns has allowed the characterization of five different subphases in early post-contrast enhancement of the liver. The quantitative extent of enhancement of abdominal organs also demonstrated significant correlation with these five subphases.

Imaging of liver disease: comparison between quadruple-phase multidetector computed tomography and magnetic resonance imaging

BACKGROUND AND AIM

To compare quadruple-phase multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) for the assessment of focal and diffuse liver disease.

METHODS

Quadruple-phase contrast-enhanced MDCT and MRI of 37 consecutive patients were retrospectively reviewed by two readers (R1 and R2). In patients with focal liver lesions, the gold standard was histopathology (n = 17) and/or long-term (>6 months) follow-up imaging (n = 27) or transarterial chemoembolization (n = 1). Diffuse liver disease was confirmed by histopathology in all patients, when present.

RESULTS

Both readers identified 60 focal liver lesions on MDCT and 56 focal liver lesions on MRI. Gold standard diagnoses revealed 48 focal liver lesions in 25 patients. Diagnosis of malignant liver lesions revealed a sensitivity of 88% (R1) and 91% (R2) for MRI; 63% (R1) and 66% (R2) for MDCT; and a specificity of 75% (R1) and 79% (R2) for MRI; 50% (R1) and 64% (R2) for MDCT. MRI was superior to MDCT for the diagnosis of malignant focal liver lesions, when the mean areas under the alternative free-response receiver operating characteristic curves (A(Z)) were compared (MRI = 0.93 vs CT = 0.69), (P < 0.00001). Thirty-three patients had histopathologically confirmed diffuse liver disease. Overall diagnosis of diffuse liver disease revealed a sensitivity of 88% (R1) and 92% (R2) for MRI; 75% (R1) and 74% (R2) for MDCT; and a specificity of 100% for both modalities by both readers.

CONCLUSIONS

MRI is superior for the assessment of malignant focal liver lesions and diffuse liver disease compared to quadruple-phase MDCT, and can be considered as primary diagnostic imaging modality for liver imaging.

Suspected chronic pancreatitis with normal MRCP: findings on MRI in correlation with secretin MRCP

PURPOSE

To review pancreatic MRI findings and their relationship with estimated pancreatic exocrine function on secretin-stimulated MR cholangiopancreatography (S-MRCP) in patients with clinically suspected chronic pancreatitis and normal baseline MRCP findings.

MATERIALS AND METHODS

MRI findings of 26 patients with normal pancreatic duct diameter and without side branch ectasia on MRCP were evaluated. A single radiologist assessed pancreatic size, pancreatic signal intensity ratio (SIR), and arterial enhancement ratio (A/V) at head, body, and tail of the pancreas on T(1)-weighted fat-suppressed and serial contrast-enhanced images at a single session. Combined findings were graded with a composite score. Serial S-MRCP was performed at the same session with standard MRI. Correlation and differences between MRI findings and associated grade of duodenal filling (DF) or the degree of pancreatic duct caliber change (PDC) were analyzed.

RESULTS

Seven patients revealed normal and 19 patients abnormal MRI findings. Significant correlation was present between the degree of DF and mean values of pancreatic size (r = 0.748), SIR (r = 0.610), A/V (r = 0.466), composite score (r = 0.833), and PDC (r = 0.554) separately. PDC correlated with SIR (r = 0.413) and composite score (r = 0.452), but not with A/V or pancreatic size. Significant differences were present between normal and abnormal DF grades in terms of mean values of associated findings of size (P = 0.001), SIR (P = 0.008), A/V (P = 0.019), and PDC (P = 0.001).

CONCLUSION

Patients with clinically suspected chronic pancreatitis and normal MRCP findings may have a spectrum of MRI findings that correlate with the estimated pancreatic exocrine insufficiency on S-MRCP with the increasing number of combined findings.

Double-contrast MRI for accurate staging of hepatocellular carcinoma in patients with cirrhosis

OBJECTIVE

The aim of this study was to evaluate the accuracy of a double-contrast MRI protocol in staging of hepatocellular carcinoma (HCC) in patients with cirrhosis.

MATERIALS AND METHODS

This cross-sectional study was performed at a tertiary liver care center. Forty-eight patients with cirrhosis underwent double-contrast MRI for clinical care and liver transplantation. For each MRI examination, superparamagnetic iron oxide was infused, and 2D T2*-weighted spoiled gradient-recalled echo and T2-weighted echo-train spin-echo MR images were obtained for assessment of phagocytic function. Immediately afterward, a low-molecular-weight gadolinium compound was injected, and 3D T1-weighted spoiled gradient-recalled echo images were acquired dynamically for assessment of vascularity. Two blinded radiologists independently reviewed all MR images and assigned per-lesion and per-patient cancer confidence scores to determine the American Liver Tumor Study Group tumor stage. The imaging-based cancer scores and tumor stages were correlated with pathology reports. Performance parameters were computed for imaging-based measurements.

RESULTS

Of the 48 study subjects, 25 had HCC (three, T1; 18, T2; one, T3; one, T4a; two, T4b). In total, there were 37 HCC nodules. The accuracy of MRI in prediction of pathologic tumor stage was 81-85% depending on the radiologist. Per-patient and per-lesion sensitivity in the diagnosis of HCC were 96% and 81% for one radiologist and 96% and 89% for the other.

CONCLUSION

A double-contrast MRI protocol has high accuracy in staging of HCC in patients with cirrhosis.

Patient-specific Time to Peak Abdominal Organ Enhancement Varies with Time to Peak Aortic Enhancement at MR Imaging

PURPOSE

To retrospectively evaluate the relationship between the times to peak enhancement of the liver, pancreas, and jejunum with respect to the time to peak aortic enhancement at magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The committee on human research approved this study and waived written informed consent. This study was HIPAA compliant. The study retrospectively identified 141 patients (63 men, 78 women; mean age, 57 years) who underwent abdominal MR imaging by using a test bolus that was monitored approximately every second for 2 minutes with a spoiled gradient-echo T1 transverse section through the upper abdomen. The times to peak enhancement of the aorta, liver, pancreas, and jejunum were recorded and correlated with the time to peak aortic enhancement, age, and sex by means of univariate and multivariate linear regression analyses.

RESULTS

The mean time to peak aortic enhancement was 21.1 seconds (range, 8.7-41.8 seconds). The times to peak enhancement of the liver, pancreas, and jejunum were positively and linearly correlated with the time to peak aortic enhancement (r = 0.69, 0.86, and 0.80, respectively, all P < .001) and were 3.39, 1.64, and 2.04 times longer than the time to peak aortic enhancement, respectively. Age, sex, and history of heart disease did not give additional predictive information for determining the time to peak visceral enhancement.

CONCLUSION

The times to peak enhancement of the liver, pancreas, and jejunum are linearly related to that of the aorta. These results could potentially allow tailored patient- and organ-specific scan delay optimization at contrast material-enhanced MR image evaluation.

Test bolus measurement: effects of the respiratory position on bolus arrival time and signal-intensity-time curve quality

OBJECT

The aim of our study is to determine if the respiratory position (free breathing, end expiration) influences bolus arrival time (BAT) or the quality of the SI-time curve in the test bolus measurement.

MATERIALS AND METHODS

We examined 150 consecutive patients in free breathing and end expiration with 1 mL contrast media (CM) and a flow of 3 mL/s with MRI. The BAT in the aorta and the quality of the SI-time curve were determined.

RESULTS

In 13/300 measurements BAT could not be determined because of poor quality of the SI-time curve (two free breathing, 11 end expiration). Mean BAT was 21 s in both respiratory positions. In 13/137 (9%) there was a difference in BAT in end expiration and free breathing of more than 5 s without a tendency towards elongation or shortening of BAT due to the respiratory command (RC). Quality of the SI-time curve was significantly better in the second of both measurements independently of the respiratory position and in free breathing compared to end expiration.

CONCLUSION

Test bolus examinations may differ in an individual patient of more than 5 s without a tendency towards elongation or shortening due to the RC. SI-time curve quality is negatively influenced by the RC.

Magnetic resonance imaging of the liver: a review

In this review article, the authors discuss the essential aspects of liver magnetic resonance imaging (MRI), including protocol, intravenous contrast use and disease entities. At present, liver MRI uses fast scanning techniques, allowing the maximization of the principles of image quality, reproducibility of image quality and good conspicuity of disease. MRI is the most accurate imaging modality for the detection and characterization of diffuse and focal liver disease. In the expert opinion section, the authors refer to the advantages and challenges of 3.0T liver imaging.

Liver MR Imaging: 1.5T versus 3T

This article focuses on technical challenges in transferring 1.5T liver protocols to 3T systems and the overall comparison of MR sequences, highlighting the advantages and disadvantages of imaging at the higher field strength. An important benefit is the capacity of acquiring high-quality, thin-section postgadolinium T1-weighted three-dimensional gradientecho sequences, most clinically relevant for the detection and characterization of small hypervascular malignant diseases. Further research and development is necessary to overcome disadvantages, such as with in- and out-of phase T1-weighted gradient-echo sequences, and to minimize artifacts that appear at 3T.

Serial contrast-enhanced MRI of the pancreas: correlation with secretin-stimulated endoscopic pancreatic function test

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the relationship between the pancreatic enhancement on serial contrast-enhanced MRI (CEMRI) and pancreatic exocrine function using the secretin-stimulated endoscopic pancreatic function test (ePFT).

MATERIALS AND METHODS

A total of 30 patients with clinical symptoms consistent with chronic pancreatitis underwent CEMRI of the abdomen and ePFT within a 1- to 4-week interval. CEMRI was performed in arterial, early venous, and late venous phases. Secretin ePFT was performed with the measurement of HCO(3) concentration from the duodenal aspirates after secretin stimulation. Contrast enhancement ratio of the arterial phase to early venous phase was measured on CEMRI (SIRa/SIRv). A three-point evaluation system was used for grading the HCO(3) concentration and the enhancement ratio on MRI. For the significance of correlation, kappa statistics was used. Sensitivity and specificity of CEMRI was determined for the diagnosis of early chronic pancreatitis accepting ePFT as a reference.

RESULTS

Twenty patients had identical scores on both secretin ePFT and CEMRI. Ten patients revealed discrepancy in scores. Kappa statistics revealed moderate agreement between MRI and ePFT (kappa = 0.44). Sensitivity and specificity values for the diagnosis of pancreatitis were 82% and 57%, respectively. Positive predictive value was 56%, and negative predictive value was 86%.

CONCLUSION

The results of our data indicate that serial CEMRI is an appropriate imaging technique to rule out early chronic pancreatitis. However, secretin-stimulated imaging or ePFT may still be needed for the definite diagnosis of pancreatic exocrine dysfunction.

Triple Arterial Phase Dynamic MRI with Sensitivity Encoding for Hypervascular Hepatocellular Carcinoma: Comparison of the Diagnostic Accuracy Among the Early, Middle, Late, and Whole Triple Arterial Phase Imaging

OBJECTIVE

We assessed and compared the diagnostic accuracy of the early, middle, late, and whole triple arterial phase MRI with sensitivity encoding (SENSE) for the detection of hypervascular hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Thirty-one patients with 102 HCCs underwent dynamic MRI with SENSE. The findings of CT examinations, combined with those of visceral angiography or histopathologic examination, were used as the gold standard. After acquisition of T1- and T2-weighted images, gadolinium-enhanced triple arterial, portal, and delayed phase images were obtained. Acquisition of the triple arterial phase imaging was started at the timing of peak aortic enhancement and completed within a single breath-hold. Acquisition time for each phase was 8.4 sec. Four image sets including the early, middle, late, and whole triple arterial phase imaging were interpreted separately by four observers. The mean values of area under alternative-free-response receiver operating characteristic (AFROC) curve and of sensitivity were compared among the four image sets.

RESULTS

The mean values of area under AFROC curve were 0.52, 0.66, 0.53, and 0.68 and of sensitivity were 45%, 64%, 48%, and 65% for the image sets with the early, middle, late, and whole triple arterial phase imaging, respectively. Both mean values were significantly higher for the image sets with the middle and whole triple arterial phase imaging than for those with the early and late arterial phase imaging.

CONCLUSION

The middle arterial phase imaging with k-space centered at 12.6 sec after the peak aortic enhancement was optimal for detecting HCC and showed diagnostic accuracy equivalent to that of the whole triple arterial phase imaging.

Lung image database consortium: developing a resource for the medical imaging research community

To stimulate the advancement of computer-aided diagnostic (CAD) research for lung nodules in thoracic computed tomography (CT), the National Cancer Institute launched a cooperative effort known as the Lung Image Database Consortium (LIDC). The LIDC is composed of five academic institutions from across the United States that are working together to develop an image database that will serve as an international research resource for the development, training, and evaluation of CAD methods in the detection of lung nodules on CT scans. Prior to the collection of CT images and associated patient data, the LIDC has been engaged in a consensus process to identify, address, and resolve a host of challenging technical and clinical issues to provide a solid foundation for a scientifically robust database. These issues include the establishment of (a) a governing mission statement, (b) criteria to determine whether a CT scan is eligible for inclusion in the database, (c) an appropriate definition of the term qualifying nodule, (d) an appropriate definition of "truth" requirements, (e) a process model through which the database will be populated, and (f) a statistical framework to guide the application of assessment methods by users of the database. Through a consensus process in which careful planning and proper consideration of fundamental issues have been emphasized, the LIDC database is expected to provide a powerful resource for the medical imaging research community. This article is intended to share with the community the breadth and depth of these key issues.