Focal hepatic lesions: diagnostic value of enhancement pattern approach with contrast-enhanced 3D gradient-echo MR imaging

MR imaging of benign focal liver lesions

Focal liver lesions (FLLs) are commonly encountered on routine imaging studies. Most lesions detected are benign, but many are indeterminate at the time of initial imaging. This article reviews the important role of MR imaging for the detection and characterization of various benign FLLs while illustrating typical imaging appearances and potential pitfalls in interpretation. The utility of diffusion-weighted imaging and hepatocyte-specific contrast agents is also discussed.

Respiratory motion artifact affecting hepatic arterial phase imaging with gadoxetate disodium: examination recovery with a multiple arterial phase acquisition

PURPOSE

To determine whether the use of a multiple arterial phase imaging technique provides adequate image quality in patients experiencing transient severe motion (TSM) in the arterial phase on abdominal magnetic resonance (MR) images obtained with gadoxetate disodium.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board and was compliant with HIPAA. The requirement to obtain informed consent was waived. Five hundred forty-nine consecutive MR examinations were evaluated, 345 performed with gadoxetate disodium and 204 performed with gadobenate dimeglumine. All examinations included single-breath-hold triple arterial phase acquisition. Five radiologists blinded to the contrast material rated motion on a scale of 1 (no motion) to 5 (nondiagnostic images) for the precontrast phase, the three arterial phases, the portal venous phase, and the late dynamic phase. Adequacy of late hepatic arterial timing was also rated for the each of the three arterial phases. Mean motion scores were compared by using the Wilcoxon signed rank test. The number of patients with TSM, as well as the number of those with "adequate" arterial phases, was compared with the χ(2) or Fisher exact test, as appropriate.

RESULTS

Mean motion scores in all three arterial phases in the gadoxetate disodium cohort were significantly worse than those in the gadobenate dimeglumine cohort (P < .005). TSM occurred at a higher rate with gadoxetate disodium than with gadobenate dimeglumine (10.7% [37 of 345 examinations] vs 0.5% [one of 204 examinations], P < .001). However, 30 of 37 examinations affected by TSM had at least one well-timed arterial phase with a mean motion score of 3 or less and were thus considered adequate.

CONCLUSION

Use of single-breath-hold multiple arterial phase acquisition in abdominal MR imaging with gadoxetate disodium recovers most arterial phases that would otherwise have been compromised by transient motion.

Free-breathing contrast-enhanced multiphase MRI of the liver using a combination of compressed sensing, parallel imaging, and golden-angle radial sampling

OBJECTIVE

The objectives of this study were to develop a new method for free-breathing contrast-enhanced multiphase liver magnetic resonance imaging (MRI) using a combination of compressed sensing, parallel imaging, and radial k-space sampling and to demonstrate the feasibility of this method by performing image quality comparison with breath-hold cartesian T1-weighted (conventional) postcontrast acquisitions in healthy participants.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act-compliant prospective study received approval from the institutional review board. Eight participants underwent 3 separate contrast-enhanced fat-saturated T1-weighted gradient-echo MRI examinations with matching imaging parameters: conventional breath-hold examination with cartesian k-space sampling volumetric interpolate breath hold examination (BH-VIBE) and free-breathing acquisitions with interleaved angle-bisection and continuous golden-angle radial sampling schemes. Interleaved angle-bisection and golden-angle data from each 100 consecutive spokes were reconstructed using a combination of compressed sensing and parallel imaging (interleaved-angle radial sparse parallel [IARASP] and golden-angle radial sparse parallel [GRASP]) to generate multiple postcontrast phases.Arterial- and venous-phase BH-VIBE, IARASP, and GRASP reconstructions were evaluated by 2 radiologists in a blinded fashion. The readers independently assessed quality of enhancement (QE), overall image quality (IQ), and other parameters of image quality on a 5-point scale, with the highest score indicating the most desirable examination. Mixed model analysis of variance was used to compare each measure of image quality.

RESULTS

Images of BH-VIBE and GRASP had significantly higher QE and IQ values compared with IARASP for both phases (P < 0.05). The differences in QE between BH-VIBE and GRASP for the arterial and venous phases were not significant (P > 0.05). Although GRASP had lower IQ score compared with BH-VIBE for the arterial (3.9 vs 4.8; P < 0.0001) and venous (4.2 vs 4.8; P = 0.005) phases, GRASP received IQ scores of 3 or more in all participants, which was consistent with acceptable or better diagnostic image quality.

CONCLUSION

Contrast-enhanced multiphase liver MRI of diagnostic quality can be performed during free breathing using a combination of compressed sensing, parallel imaging, and golden-angle radial sampling.

Diffusion- and T₂-weighted MR imaging of the liver: effect of intravenous administration of gadoxetic acid disodium

PURPOSE

We evaluated the effect of intravenous administration of gadoxetic acid disodium to hepatic lesions and liver parenchyma on T₂-weighted (T₂WI) and diffusion-weighted imaging (DWI).

MATERIALS AND METHODS

One hundred and one consecutive patients with 259 hepatic lesions underwent T₂WI and DWI (b-values of 500 and 1000 s/mm²) before and after gadoxetic acid administration. We compared the ratio of signal intensity (SIR) of the liver parenchyma and hepatic lesions, the ratio of contrast intensity of the lesion to the liver (CIR), the apparent diffusion coefficients (ADCs) of the liver and lesions, and lesion detectability between pre- and post-contrast images.

RESULTS

SIRs, CIRs, and ADC of focal hepatic lesions were comparable on pre- and post-contrast images, and lesion detectability did not differ significantly between pre- and post-contrast T₂WI and DWI. The SIRs of the liver parenchyma were significantly lower on post-contrast DWI (1.4±0.68 [b=500 s/mm²] and 1.71±0.67 [b=1000 s/mm²]) than pre-contrast images (1.89±0.68 [b=500 s/mm²] and 2.26±0.78 [b=1000 s/mm²]) (P<0.001). ADCs of the liver parenchyma were also significantly decreased on post-contrast DWI (0.77±0.32 mm²/s) than pre-contrast images (0.64±0.33 mm²/s) (P=0.001).

CONCLUSION

T₂WI and DWI after administration of gadoxetic acid are feasible and do not compromise the SIR, CIR, and ADC of focal hepatic lesions. However, the signal intensity of DWI and ADC value of the liver parenchyma were decreased on gadoxetic acid-enhanced hepatocyte phase images.

Characterization of hepatic tumors using [11C]metomidate through positron emission tomography: comparison with [11C]acetate

Background

Using positron emission tomography (PET), we compared two tracers, [¹¹C]metomidate ([¹¹C]MTO) and [¹¹C]acetate ([¹¹C]ACE), for the characterization of hepatic tumors.

Methods

Thirty-three patients underwent PET with [¹¹C]MTO and [¹¹C]ACE and magnetic resonance imaging (MRI). Based on the histology of the tumor biopsy, 14 patients had hepatocellular carcinoma (HCC), 9 patients had focal nodular hyperplasia (FNH), and 10 patients had other types of hepatic tumors. Tumor uptake was evaluated by calculating the maximum and mean standardized uptake value and tumor-to-liver ratio.

Results

Altogether, 120 hepatic lesions (59 HCC, 18 FNH, 30 metastases of different primaries, 9 adenomas, and 4 regenerating nodules of liver cirrhosis) were detected by MRI. The overall tumor detection rate was slightly higher for [¹¹C]MTO (39%) than for [¹¹C]ACE (33%). [¹¹C]ACE was more sensitive for HCC detection (50% versus 43%, respectively), whereas [¹¹C]MTO was more sensitive for FNH detection (78% versus 44%, respectively). In HCC patients, the tumor grade correlated with [¹¹C]ACE, but not with [¹¹C]MTO. All of the patients with liver metastases, from various primary tumors (n = 10), were negative for both tracers.

Conclusions

Due to low sensitivity, [¹¹C]MTO and [¹¹C]ACE PET have only limited value in diagnosing hepatic tumors.

[Overview: liver tumors]

Since the introduction of abdominal ultrasound liver lesions have been increasingly detected. Being usually diagnosed by chance these lesions create psychological stress among patients because a potential malignant disease has to be taken into consideration. The increasing use of oral contraceptives with high estrogen doses starting in the 1980s led to a rising incidence of adenomas, whose natural history differed from those described in surgical and autoptic studies. This fact brought about a change towards a modern pathophysiologic and prognostic differentiation. Current histologic and molecular biological techniques are able to distinguish benign adenomas from those with malignant potential.

Comparison of acute transient dyspnea after intravenous administration of gadoxetate disodium and gadobenate dimeglumine: effect on arterial phase image quality

PURPOSE

To determine whether acute transient dyspnea and/or arterial phase image degradation occurs more or less often after intravenous administration of gadoxetate disodium than with intravenous administration of gadobenate dimeglumine.

MATERIALS AND METHODS

Institutional review board approval and patient consent were obtained for this prospective observational study. One hundred ninety-eight gadolinium-based contrast media administrations (99 with gadoxetate disodium [10 mL, n = 97; 8 mL, n = 1; 16 mL, n = 1] and 99 with gadobenate dimeglumine [0.1 mmol per kilogram of body weight, maximum dose, 20 mL]) for hepatobiliary indications were assessed in 192 patients. Subjective patient complaints were assessed. Objective respiratory motion degradation on T1-weighted precontrast and dynamic postcontrast (arterial, venous, or late dynamic or extracellular) magnetic resonance (MR) imaging datasets were independently assessed in a randomized, blinded fashion by five readers using a five-point scale, with mean scores of 4 or greater indicating severe motion. Comparisons between agents were made by using χ(2) or Fisher exact test, where appropriate.

RESULTS

Significantly more patient complaints of acute transient dyspnea occurred after gadoxetate disodium administration than gadobenate dimeglumine (14% [14 of 99] vs 5% [five of 99], P = .05). There were significantly more severely degraded arterial phase data sets for gadoxetate disodium than for gadobenate dimeglumine for both the general population (17% [17 of 99] vs 2% [two of 99], P = .0007) and the subpopulation with cirrhosis (19% [14 of 72] vs 3% [one of 37], P = .02). This effect did not extend to venous (1% [one of 99] vs 2% [two of 99], P > .99 [overall population]) or late dynamic or extracellular (2% [two of 99] vs 0% [zero of 99], P = .5 [overall population]) phases. No patient required treatment for self-limited dyspnea.

CONCLUSION

Intravenous gadoxetate disodium can result in acute self-limiting dyspnea that can have a deleterious effect on arterial phase MR image quality and occurs significantly more often than with intravenous gadobenate dimeglumine.

Comparison of breathhold, navigator-triggered, and free-breathing diffusion-weighted MRI for focal hepatic lesions

PURPOSE

To compare the breathhold, navigator-triggered, and free-breathing techniques in diffusion-weighted magnetic resonance imaging (MRI) for the evaluation of focal liver lesions on a 3.0T system.

MATERIALS AND METHODS

Fifty-two patients (36 men, 16 women; mean age, 56.4 years) with focal liver lesions underwent breathhold, navigator-triggered, and free-breathing diffusion-weighted imaging (DWI) of the liver on a 3.0 Tesla (T) system. All sequences were performed with b values of 50 and 800 s/mm(2) and identical parameters except for signal averages (two for navigator-triggered, one for breathhold, and four for free-breathing) and repetition time (3389 ms for navigator-triggered, 1500 ms for breathhold, and 4400 ms for free-breathing). A total of 74 lesions (50 malignant, 24 benign) were evaluated. The signal-to-noise ratios (SNR) of the liver and lesions, contrast-to-noise ratios (CNR) of each lesion, and ADC values of the liver and lesions were compared for each DWI sequence. The detection sensitivity and characterization accuracy were also compared.

RESULTS

The SNRs of the liver and lesions were significantly lower for breathhold DWI than for non-breathhold DWI (navigator-triggered and free-breathing DWI) for all b values. The CNRs of the lesions were also significantly lower for breathhold DWI than for non-breathhold DWI. The ADC values of the liver and focal lesions measured using the three DWI techniques were not significantly different and showed good correlation. For lesion detection and characterization, there were no significant differences between breathhold and non-breathhold DWI.

CONCLUSION

Both breathhold and non-breathhold DWI are comparable for the detection or characterization of focal liver lesions at 3.0T; however, non-breathhold DWI provides higher SNR and CNR than breathhold DWI. In addition, although free-breathing and navigator-triggered DWI sequences show similar performance for 3.0T liver imaging, free-breathing DWI is more time efficient than navigator-triggered DWI.

Imaging of multifocal hepatic lesions in pediatric patients

Imaging plays a vital role in detection and characterization of multifocal liver lesions in children. Numerous causes for these lesions exist, including benign and malignant neoplasms, infectious lesions, and congenital and inflammatory conditions. The imaging spectrum of multifocal liver lesions in children is presented with emphasis on key imaging features, differential diagnoses and helpful relevant clinical features.

Accuracy of visual analysis vs. apparent diffusion coefficient quantification in differentiating solid benign and malignant focal liver lesions with diffusion-weighted imaging

PURPOSE

The authors compared the accuracy of diffusion-weighted imaging (DWI) visual analysis (VA) vs. apparent diffusion coefficient quantification (ADC-Q) in assessing malignancy of solid focal liver lesions (FLLs).

MATERIALS AND METHODS

Using a 1.5-T system, two radiologists retrospectively assessed as benign or malignant 50 solid FLLs: (a) by VA of signal intensity on DWI images at b=800 s/mm(2) and ADC map; (b) by quantifying lesion ADC. Reference standard included histology or follow-up confirmation of diagnosis by a consensus panel. Receiver operating characteristic (ROC) curve analysis was performed.

RESULTS

because of 20 false-negative hepatocellular carcinomas, VA showed lower accuracy than ADC-Q (52.0% VS. 68.0%). however, stratified accuracy for metastases was higher with VA (75.0 VS. 66%). ADC and signal features of malignant and benign FLLs were found to largely overlap.

CONCLUSIONS

VA performed worse than ADC-Q for hepatocellular carcinoma and better for metastases. Overall, the accuracy of both methods was limited because of the overlap in visual appearance and ADC values between solid benign and malignant FLLs.

Diffusion-weighted MRI in a liver protocol: Its role in focal lesion detection

AIM: To evaluate the role of diffusion-weighted imaging (DWI) in the detection of focal liver lesions (FLLs), using a conventional magnetic resonance imaging (MRI) protocol.

METHODS: Fifty-two patients (22 males, average age 55.6 years, range: 25-82 years), studied using a 1.5 Tesla magnetic resonance scanner, were retrospectively analyzed; detection of FLLs was evaluated by considering the number of lesions observed with the following sequences: (1) respiratory-triggered diffusion-weighted single-shot echo-planar (DW SS-EP) sequences; (2) fat-suppressed fast spin-echo (fs-FSE) T2 weighted sequences; (3) steady-state free precession (SSFP) images; and (4) dynamic triphasic gadolinium-enhanced images, acquired with three-dimensional fast spoiled gradient-echo (3D FSPGR). Two radiologists independently reviewed the images: they were blinded to their respective reports. DW SS-EP sequences were compared to fs-FSE, SSFP and dynamic gadolinium-enhanced acquisitions using a t-test. Pairs were compared for the detection of: (1) all FLLs; (2) benign FLLs; (3) malignant FLLs; (4) metastases; and (5) hepatocellular carcinoma (HCC).

RESULTS: Interobserver agreement was very good (weighted κ = 0.926, CI = 0.880-0.971); on the consensus reading, 277 FLLs were detected. In the comparison with fs-FSE, DW SS-EP sequences had a significantly higher score in the detection of all FLLs, benign FLLs, malignant FLLs and metastases; no statistical difference was observed in the detection of hepatocellular carcinoma (HCCs). In the comparison with SSFP sequences, DW SS-EP had significantly higher scores (P < 0.05) in the detection of all lesions, benign lesions, malignant lesions, metastases and HCC. All FLLs were better detected by dynamic 3D FSGR enhanced acquisition, with P = 0.0023 for reader 1 and P = 0.0086 for reader 2 in the comparison with DW SS-EP sequences; with reference to benign FLLs, DW SS-EP showed lower values than 3D FSPGR enhanced acquisition (P < 0.05). No statistical differences were observed in the detection of malignant lesions and metastases; considering HCCs, a very slight difference was reported by reader 1 (P = 0.049), whereas no difference was found by reader 2 (P = 0.06).

CONCLUSION: In lesion detection, DWI had higher scores than T2 sequences; considering malignant FLLs, no statistical difference was observed between DWI and dynamic gadolinium images.

[Benign focal hepatic lesions]

A profound knowledge of the various benign focal hepatic lesions and selection of the most suitable radiological examination modality is essential for achieving an accurate characterization of a hepatic lesion and in turn will determine the further patient management. This will avoid unnecessary agitation to both patient and the referring clinician and limits time-consuming, costly and risky biopsies to an absolute minimum. The following article will discuss the typical and atypical appearances of the most frequent and clinically relevant benign focal hepatic lesions with ultrasound, computed tomography and magnetic resonance imaging.

Free-breathing radial 3D fat-suppressed T1-weighted gradient echo sequence: a viable alternative for contrast-enhanced liver imaging in patients unable to suspend respiration

OBJECTIVE

: To compare free-breathing radially sampled 3D fat suppressed T1-weighted gradient-echo acquisitions (radial volumetric interpolated breath-hold examination [VIBE]) with breath-hold (BH) and free-breathing conventional (rectilinearly sampled k-space) VIBE acquisitions for postcontrast imaging of the liver.

MATERIALS AND METHODS

: Eighteen consecutive patients referred for clinically indicated liver magnetic resonance imaging were imaged at 3 T. Three minutes after a single dose of gadolinium contrast injection, free-breathing radial VIBE, BH VIBE, and free-breathing VIBE with 4 averages were acquired in random order with matching sequence parameters. Radial VIBE was acquired with the "stack-of-stars" scheme, which uses conventional sampling in the slice direction and radial sampling in-plane.All image data sets were evaluated independently by 3 radiologists blinded to patient and sequence information. Each reader scored the following parameters: overall image quality, respiratory motion artifact, pulsation artifact, liver edge sharpness, and hepatic vessel clarity using a 5-point scale, with the highest score indicating the most optimum examination. Mixed model analysis of variance was used to compare sequences in terms of each measure of image quality.

RESULTS

: When scores were averaged over readers, there was no statistically significant difference between radial VIBE and BH VIBE regarding overall image quality (P = 0.1015), respiratory motion artifact (P = 1.0), and liver edge sharpness (P = 0.2955). Radial VIBE demonstrated significantly lower pulsation artifact (P < 0.0001), but had lower hepatic vessel clarity (P = 0.0176), when compared with BH VIBE. Radial VIBE had significantly higher image quality scores for all parameters when compared with free-breathing VIBE (P < 0.0001). Acquisition time for BH VIBE was 14 seconds and that of free-breathing radial VIBE and conventional VIBE with multiple averages was 56 seconds each.

CONCLUSION

: Radial VIBE can be performed during free breathing for contrast-enhanced imaging of the liver with comparable image quality to BH VIBE. However, further work is necessary to shorten the acquisition time to perform dynamic imaging.

Diagnosing small hepatic cysts on multidetector CT: an additional merit of thinner coronal reformations

Objective

We wanted to validate the additional merit of the thinner coronal reformation images from multidetector CT (MDCT) for making the diagnosis of hepatic cysts.

Materials and Methods

For the 90 benign hepatic cysts confirmed on MRI, the transverse (5-mm thickness) and additional coronal (2-mm thickness) reformation images from MDCT were compared with each other in terms of the Hounsfield units (HUs) and the size of each hepatic cyst.

Results

The attenuations (mean: 17.2 HUs, standard deviation: ± 14.4) on the thinner coronal images were significantly lower than those (mean: 40.7 HUs; standard deviation: ± 20.6) on the thicker transverse images for the small hepatic cysts (≤ 10 mm on the transverse image, p < 0.01). Twenty-three (79%) of the 29 cysts between 5 mm and 10 mm and 21 (51%) of 41 lesions up to 5 mm showed a mean HU value of 20 or less on the coronal reformation images.

Conclusion

By reducing the partial volume effect, routine coronal reformation of MDCT with a thinner section thickness can provide another merit for making a confidential diagnosis of many small sub-centimeter hepatic cysts, and these small cysts are not easily characterized on the conventional transverse images.

Contrast enhanced ultrasound in the detection of liver metastases: a prospective multi-centre dose testing study using a perfluorobutane microbubble contrast agent (NC100100)

OBJECTIVE

To conduct a dose testing analysis of perfluorobutane microbubble (NC100100) contrast-enhanced ultrasound (CEUS) to determine the optimal dose for detection of liver metastases in patients with extra-hepatic primary malignancy.

METHODS

157 patients were investigated with conventional US and CEUS. CEUS was performed following intravenous administration of perfluorobutane microbubbles (using one dose of either 0.008, 0.08, 0.12 or 0.36 μL/kg body weight). Three blinded off-site readers recorded the number and locations of metastatic lesions detected by US and CEUS. Contrast enhanced CT and MRI were used as the "Standard Of Reference" (SOR). Sensitivity, specificity and accuracy of liver metastasis detection with US versus CEUS, for each dose group were obtained. Dose group analysis was performed using the Chi-square test.

RESULTS

165 metastases were present in 92 patients who each had 1-7 lesions present on the SOR. Sensitivity of US versus CEUS (for all doses combined) was 38% and 67% (p = 0.0001). The 0.12 dose group with CEUS (78%) had significantly higher sensitivity and accuracy (70%) compared to other dose groups (p < 0.05).

CONCLUSION

The diagnostic performance of CEUS is dose dependent with the 0.12 μL/kg NC100100 dose group showing the greatest sensitivity and accuracy in detection of liver metastases.

Diffusion-weighted MRI and liver metastases

Liver metastases are the most frequently encountered malignant liver lesions in the Western countries. Accurate diagnosis of liver metastases is essential for appropriate management of these patients. Multiple imaging modalities, including ultrasound, CT, positron emission tomography, and MRI, are available for the evaluation of patients with suspected or known liver metastases. Contrast-enhanced MRI has a high accuracy for detection and characterization of liver lesions. Additionally, diffusion-weighted MRI (DWI) has been gaining increasing attention. It is a noncontrast technique that is easy to perform, could be incorporated in routine clinical protocols, and has the potential to provide tissue characterization. This article discusses the basic principles of DWI and discusses its emerging role in the detection of liver metastases in patients with extrahepatic malignancies.

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.

Hepatic perfusion imaging: concepts and application

Hepatic perfusion imaging with magnetic resonance (MR) imaging is an emerging technique for quantitative assessment of diffuse hepatic disease and hepatic lesion blood flow. The principal method that has been used is based on T1 dynamic contrast-enhanced MR imaging. Perfusion imaging shows promise in the assessment of tumor therapy response, staging of liver fibrosis, and evaluation of hepatocellular carcinoma. The future standardization of imaging protocols and MR imaging pulse sequences will allow for broader clinical applications.

Contrast-Enhanced Ultrasound (CEUS) for Echographic Detection of Hepato Cellular Carcinoma in Cirrhotic Patients Previously Treated with Multiple Techniques: Comparison of Conventional US, Spiral CT and 3-Dimensional CEUS with Navigator Technique (3DNav CEUS)

A commercially available technique named “NAVIGATOR” (Esaote, Italy) easily enables a 3-D reconstruction of a single 2-D acquisition of Contrast Enhanced Ultrasound (CEUS) imaging of the whole liver (with a volumetric correction thanks to the electromagnetic device of NAVIGATOR). Aim of the study was to evaluate this “panoramic” technique in comparison with conventional US and spiral CT in the detection of new hepatic lesions. 144 cirrhotic patients (previously treated for hepato cellular carcinoma (HCC)) in follow-up with detection of 98 new nodules (N), 28 multinodular (Nmulti), 14 loco-regional regrowth (LR) 94 efficaciously treated without new nodules (neg) and four multinodular without new nodules, were submitted to 200 examinations with this new technique from November 2008 to November 2009. 3DNavCEUS was performed using SonoVue (Bracco), as contrast agent, and a machine (Technos MPX, Esaote). Spiral CT and 3DNav CEUS were performed in the same month during follow up. Sens.,Spec.,diagn.-Acc.,PPV and NPV were evaluated; comparison and differences between the techniques were obtained with chi-square (SPSS release-15). Final diagnosis was: 98 new lesions (N) (one to three), 28 multinodular HCC (Nmulti) and 14 loco-regional regrowth (LR); in 94 no more lesions were observed during follow-up; conventional US obtained: 58 N (+18 multinodularN and 8 LR), 40 false negative (+10 Nmulti and 6 LR) (sens:59.2, spec:100%, Diagn Accur:73.6, PPV:100; NPV:70.1); spiral CT obtained: 84N (+26-multinodularN and 14-LR), 14 false-negative (+2-Nmulti), and one false-positive (sens:85.7, spec:97.9%, Diagn Accur:90.9, PPV:97.7; NPV:86.8); 3DNAV obtained: 92N (+28 multinodularN and 14LR), 6 false-negative, and two false-positives (sens:93.9, spec:97.9%, Diagn Accur:95.6, PPV:97.9; NPV:93.9). 3-DNav CEUS is significantly better than US and almost similar to spiral CT for detection of new HCC. This technique, in particular, showed the presence of lesions even in the cases not detected with spiral CT.

Hepatic and pulmonary nodular lesions in pediatric urinary tract infections

One of the major goals in investigating children with urinary tract infection (UTI) is to recognize patients at risk of further UTI-related problems. This study reports the clinical features of 19 pediatric patients with UTIs in whom associated hepatic and/or pulmonary nodules were incidentally diagnosed by the imaging tests performed for the UTI. Hepatic nodules in five patients were detected on ultrasound scans, and pulmonary nodules and both hepatic and pulmonary nodules were detected in 12 and two children by dimercaptosuccinic acid scintigraphy. The mean age of the patients was 24.5 months. Vesicoureteral reflux (VUR) was detected in nine of 17 patients (52.9%), acute pyelonephritis was identified in nine of 18 patients, and renal scarring was found in 57.1% patients with pyelonephritis. On follow-up, the hepatic and/or pulmonary nodules regressed in all patients. About 85.7% of patients experienced a recurrence of UTI within 1 year. In comparison with age- and sex-matched controls with UTIs without pulmonary or hepatic nodules, the presence of VUR and the recurrence of UTI within 1 year were higher in patients with UTIs and nodules (P<0.05). The hepatic and/or pulmonary nodules identified on the ultrasound scan and by dimercaptosuccinic acid scintigraphy may provide a valuable diagnostic marker for the proper management of patients with an UTI.

Comparison of multi-echo and single-echo gradient-recalled echo sequences for SPIO-enhanced liver MRI at 3 T

AIM

To assess the utility of a T2*-weighted, multi-echo data imaging combination sequenced on superparamagnetic iron oxide (SPIO)-enhanced liver magnetic resonance imaging (MRI) using a 3 T system.

MATERIALS AND METHODS

Fifty patients underwent SPIO-enhanced MRI at 3 T using T2*-weighted, single-echo, gradient-recalled echo (GRE) sequences [fast imaging with steady precession; repetition time (TR)/echo time (TE), 126 ms/9 ms; flip angle, 30°] and multi-echo GRE (multi-echo data image combination) sequences (TR/TE, 186 ms/9 ms; flip angle, 30°). Three radiologists independently reviewed the images in a random order. The sensitivity and accuracy for the detection of focal hepatic lesions (a total of 76 lesions in 33 patients; 48 solid lesions, 28 non-solid lesions) were compared by analysing the area under the receiver operating characteristic curves. Image artefacts (flow artefacts, susceptibility artefacts, dielectric artefacts, and motion artefacts), lesion conspicuity, and overall image quality were evaluated according to a four-point scale: 1, poor; 2, fair; 3, good; 4, excellent. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the lesions were compared.

RESULTS

Image artefacts were more frequent with single-echo GRE (p<0.05). The mean scale of image quality assessment for flow, susceptibility, dielectric, and motion artefacts were 2.76, 3.13, 3.42, and 2.89 with single-echo, respectively, compared with 3.47, 3.43, 3.47, and 3.39, respectively, with multi-echo GRE. There was no significant difference in lesion conspicuity between single-echo (3.15) and multi-echo (3.30) GRE sequences. The overall image quality was significantly (p<0.05) better with multi-echo (3.37) than with single-echo GRE (2.89). The mean SNR and CNR of the lesions were significantly (p<0.05) higher on multi-echo (79±23 and 128±59, respectively) images than on single-echo (38±11 and 102±44, respectively) images. Lesion detection accuracy and sensitivity were not significantly different between the two sequences. Mean accuracies and sensitivities were 0.864 and 0.785 for single-echo and 0.847 and 0.785 for multi-echo GRE, respectively.

CONCLUSION

At 3 T, the T2*-weighted, multi-echo data image combination sequence performs comparably to the T2*-weighted, single-echo GRE sequence for SPIO-enhanced MRI with good overall image quality and a decrease in undesired artefacts.

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.

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.

Diffusion-weighted MR imaging of liver on 3.0-Tesla system: effect of intravenous administration of gadoxetic acid disodium

OBJECTIVE

To determine whether intravenous administration of gadoxetic acid disodium (Gd-EOB-DTPA) affects lesion conspicuity and apparent diffusion coefficient (ADCs) in diffusion-weighted imaging (DWI) for hepatic magnetic resonance imaging (MRI) at 3.0 T.

METHODS

Thirty-four patients with 50 focal hepatic lesions (18 hepatocellular carcinomas, 12 metastases, 1 cholangiocarcinoma, 7 haemangiomas, 12 cysts) underwent DWI at 3.0 T before and after administration of Gd-EOB-DTPA. Non-breath-hold DWI was performed with b values of 0, 200, 400 and 800 s/mm(2). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of each lesion, and ADCs of the liver and lesion were calculated for unenhanced and enhanced images. Statistical differences between unenhanced and enhanced data were assessed.

RESULTS

SNRs and ADCs of the liver on enhanced images were significantly lower than on unenhanced images. On DW images at b = 200 s/mm(2), CNRs of malignant and overall lesions were significantly higher on enhanced than on unenhanced images. CNRs of focal lesions tended to be higher, especially in malignant lesions, on DW images at b = 0 and 400 s/mm(2), but without reaching statistical significance. ADCs of focal hepatic lesions were not significantly different before and after administration of contrast agent.

CONCLUSION

DWI after Gd-EOB-DTPA administration can be used as a substitute for unenhanced DWI at 3.0 T without compromising CNR and ADC of focal hepatic lesions.

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.

MR imaging of hypervascular liver masses: a review of current techniques

Major technologic advances in magnetic resonance (MR) imaging, including the advent of novel pulse sequences (eg, diffusion-weighted and steady-state free precession sequences) and the use of hepatocyte-specific contrast agents, have led to better image quality and shorter acquisition times, resulting in dramatic improvements in the noninvasive detection and characterization of hepatic lesions, particularly hypervascular neoplasms. However, as the role of MR imaging in clinical evaluation of the liver continues to evolve, keeping abreast of new developments can be daunting as well as confusing. A systematic approach that makes use of a simple decision algorithm can help differentiate hypervascular hepatic lesions on the basis of their distinguishing MR imaging characteristics and related clinical information.

Differentiation of well-differentiated hepatocellular carcinomas from other hepatocellular nodules in cirrhotic liver: value of SPIO-enhanced MR imaging at 3.0 Tesla

PURPOSE

To determine the diagnostic value of superparamagnetic iron oxide (SPIO)-enhanced MRI for the differentiation of well-differentiated hepatocellular carcinomas (WD-HCCs) from other hepatocellular nodules in cirrhotic liver.

MATERIALS AND METHODS

This study included 114 patients with 216 histologically confirmed hepatocellular nodules, i.e., 23 dysplastic nodules (DNs), 37 WD-HCCs, and 156 moderately or poorly differentiated HCCs (MD-/PD HCCs), who underwent SPIO-enhanced MRI at 3.0T. MRI included T2-weighted fast-spin echo and T2*-weighted gradient recalled echo (GRE) sequences before and after administration of ferucarbotran. The contrast-to-noise ratio (CNR) of the lesion was calculated. Reviewers analyzed signal intensity (SI) of the nodules and their enhancement features on SPIO-enhanced images. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in the diagnosis of WD-HCC were also calculated.

RESULTS

The mean CNR of WD-HCC was significantly higher than that of DN on T2*-weighted image. Incomplete high SI on SPIO-enhanced T2*-weighted images were seen in 56.8% of WD-HCC. The most prevalent enhancement features of WD-HCCs on SPIO-enhanced T2*-weighted images, were iso SI with high SI foci [32.5% (12/37)] and homogenous subtle high SI [24.3% (9/37)]. Alternatively, 22 of 23 DNs (95.7%) showed low- or iso SI, and 145 of 156 (94.9%) MD-/PD HCCs showed strong high SI. When iso SI with high SI foci or subtle homogenous high SI nodule was considered as diagnostic criteria for WD-HCC, we could identify 56.8% of the WD-HCCs but only 4.4% of the DNs and 3.2% of the MD-/PD HCCs.

CONCLUSION

WD-HCCs have characteristic enhancement features that differentiate them from DNs and MD-/PD HCCs on SPIO-enhanced 3.0T MRI. The lesion conspicuity was better on T2*-weighted images than that on T2-weighted images.Inc.

Imaging detection of new HCCs in cirrhotic patients treated with different techniques: Comparison of conventional US, spiral CT, and 3-dimensional contrast-enhanced US with the Navigator technique (Nav 3D CEUS)()

INTRODUCTION

The commercially available Navigator system(©) (Esaote, Italy) allows easy 3D reconstruction of a single 2D acquisition of contrast-enhanced US (CEUS) imaging of the whole liver (with volumetric correction provided by the electromagnetic device of the Navigator(©)). The aim of our study was to compare the efficacy of this panoramic technique (Nav 3D CEUS) with that of conventional US and spiral CT in the detection of new hepatic lesions in patients treated for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

From November 2006 to May 2007, we performed conventional US, Nav 3D CEUS, and spiral CT on 72 cirrhotic patients previously treated for 1 or more HCCs (M/F: 38/34; all HCV-positive; Child: A/B 58/14) (1 examination: 48 patients; 2 examinations: 20 patients; 3 examinations: 4 patients). Nav 3D CEUS was performed with SonoVue(©) (Bracco, Milan, Italy) as a contrast agent and Technos MPX(©) scanner (Esaote, Genoa, Italy). Sensitivity, specificity, diagnostic accuracy, and positive and negative predictive values (PPV and NPV, respectively) were evaluated. Differences between the techniques were assessed with the chi-square test (SPSS release-15).

RESULTS

Definitive diagnoses (based on spiral CT and additional follow-up) were: 6 cases of local recurrence (LocRecs) in 4 patients, 49 new nodules >2 cm from a treated nodule (NewNods) in 34 patients, and 10 cases of multinodular recurrence consisting of 4 or more nodules (NewMulti). The remaining 24 patients (22 treated for 1-3 nodules, 2 treated for >3 nodules) remained recurrence-free. Conventional US correctly detected 29/49 NewNods, 9/10 NewMultis, and 3/6 LocRecs (sensitivity: 59.2%; specificity: 100%; diagnostic accuracy: 73.6%; PPV: 100%; NPV: 70.1%). Spiral CT detected 42/49 NewNods plus 1 that was a false positive, 9/10 NewMultis, and all 6 LocRecs (sensitivity: 85.7%; specificity: 95.7%; diagnostic accuracy: 90.9%; PPV: 97.7%; NPV: 75.9%). 3D NAV results were: 46N (+9 multinodularN and 6 LR), 3 false-negatives, and one false-positive (sensitivity: 93.9; specificity: 97.9%; diagnostic accuracy: 95.6; PPV: 97.9; NPV: 93.9).

CONCLUSIONS

3D Nav CEUS is significantly better than US and very similar to spiral CT for detection of new HCCs. This technique revealed the presence of lesions that could not be visualized with spiral CT.

Three-dimensional fast spoiled gradient-echo dual echo (3D-FSPGR-DE) with water reconstruction: preliminary experience with a novel pulse sequence for gadolinium-enhanced abdominal MR imaging

PURPOSE

To compare three-dimensional fast spoiled gradient-echo dual-echo (3D-FSPGR-DE) with water reconstruction to conventional 3D-FSPGR for gadolinium-enhanced abdominal imaging.

MATERIALS AND METHODS

Sixty-five patients underwent abdominal MRI on a 1.5T GE-HDx MR scanner using gadolinium-enhanced 3D-FSPGR and 3D-FSPGR-DE imaging. Qualitatively, FSPGR-DE and 3D-FSPGR images were reviewed side by side for normal anatomic structures, artifacts, and image quality. The images were reviewed separately for abnormalities of abdominal organs. Receiver operating characteristic (ROC) curve analysis was performed. Quantitative analysis measured mean signal intensity of liver, spleen, aorta, liver lesions, and noise.

RESULTS

Observers preferred FSPGR-DE for evaluating liver, vessels, muscles, and subcutaneous tissues. Fat suppression was superior on FSPGR-DE in 63 (0.97) and 61 (0.94) of 65 cases for two observers. FSPGR-DE showed less susceptibility artifact in 47 (0.72) and 41 (0.63) cases, better signal in edge slices in 60 (0.92) and 60 (0.92) cases, less phase artifact in 42 (0.65) and 45 (0.69) cases, and less parallel imaging artifact in 13 (0.20) and 10 (0.15) cases. Images were equivalent for depicting abdominal findings with no difference in the area under the ROC curve. FSPGR-DE images showed a 20%, 29%, and 34% increase in liver, splenic, and aortic signal, respectively, and a 45% and 62% increase in liver-lesion contrast and contrast-to-noise ratio (CNR), respectively.

CONCLUSION

Gadolinium-enhanced 3D-FSPGR-DE with water reconstruction provides volumetric abdominal imaging with superior image quality, more homogeneous fat suppression, reduced artifacts, and improved image signal and homogeneity.

Cholangiocarcinoma: current and novel imaging techniques

The radiologic manifestations of cholangiocarcinomas are extremely diverse, since these tumors vary greatly in location, growth pattern, and histologic type. Familiarity with the imaging manifestations of cholangiocarcinomas is important for accurate detection and characterization of these tumors and assessment of resectability. Advances in imaging techniques have led to the availability of an array of modalities that, used independently or in combination, can aid in the accurate diagnosis and evaluation of cholangiocarcinomas in preparation for advanced surgical procedures and treatment planning. Response to novel targeted therapies can also be assessed with newer imaging tools. Hence, knowledge of current and emerging imaging applications is essential for correct diagnosis and appropriate management of these tumors.

Receiver operating characteristic analysis of diffusion-weighted magnetic resonance imaging in differentiating hepatic hemangioma from other hypervascular liver lesions

PURPOSE

To evaluate the role of diffusion-weighted imaging in differentiating between hepatic hemangiomas, both typical and atypical, and other hypervascular liver lesions.

METHODS

Retrospective review of 182 hypervascular liver lesions in 117 patients was performed. Diffusion and contrast-enhanced magnetic resonance imaging were performed using a 1.5-T unit. Imaging protocol consisted of T2-weighted fast spin-echo images, breath-hold diffusion-weighted echo-planar images, and breath-hold unenhanced and contrast-enhanced T1-weighted 3-dimensional fat-suppressed spoiled gradient-echo images in the arterial phase (20 seconds) and portal venous phase (60 seconds). Signal intensity changes and apparent diffusion coefficient (ADC) values were evaluated for all lesions. Unpaired t test was used to compare the mean ADC values for different lesions, and statistical significance was set at P < 0.01. Receiver operating characteristic analysis was used to determine the accuracy of diffusion-weighted imaging in differentiating hemangiomas from other hypervascular liver lesions.

RESULTS

Lesions included typical and atypical hemangioma (n = 38), hepatocellular carcinoma (HCC; n = 58), focal nodular hyperplasia (FNH; n = 22), and neuroendocrine tumor metastasis (NET; n = 64) with a mean tumor size of 5.3 cm. Mean ADC value for hemangioma, HCC, FNH, and NET was 2.29 x 10(-3), 1.55 x 10(-3), 1.65 x 10(-3), and 1.43 x 10(-3) mm2/s, respectively. There was a statistically significant difference in the ADC value of hemangioma compared with that of FNH (P < 0.001), HCC (P < 0.001), and NET (P < 0.001), respectively. The area under the receiver operating characteristic curve was 0.91.

CONCLUSIONS

Diffusion-weighted magnetic resonance imaging and ADC maps can provide rapid quantifiable information to differentiate typical and atypical hemangiomas from other hypervascular liver lesions.

[Diagnostic imaging of liver tumours. Current status]

Nowadays, contrast enhanced ultrasound (CEUS) is an imaging technique equivalent to multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) for the detection and characterization of focal liver lesions. These methods have comparable sensitivity and specificity in differentiating a liver lesion as "benign" or "malignant". For benign lesions, CEUS is the recommended method of the choice. In unclear cases, or if CEUS is not available, MRI or CT are the methods of the second choice. If a benign tumor remains unclear, then a needle biopsy is recommended. In the case of a malignant tumor, it is necessary to use a second imaging technique besides CEUS. In addition to the detection and characterization of a liver tumor, CT and MRI provide information on the extrahepatic spread of a tumor, particularly into the lung or retroperitoneum. The rapid development of surgical and interventional approaches requires accurate information on the character and number of malignant liver lesions. Therefore, the combined use of CEUS and MDCT or MRI currently represents the most modern and optimal standard of imaging. The standardization of CT and MRI protocols has increased the general diagnostic level of these images. Adequate training and a certificate for the use of CEUS is recommended in order to maintain the high diagnostic level of this method (EFSUMB guide lines). An optimal interdisciplinary imaging strategy for focal liver lesions minimises unnecessary invasive or potentially harmful imaging and reduces health costs.