Respiratory variation of the extrahepatic bile duct: evaluation with deep inspiratory and expiratory MRCP

Purpose

The purpose of the study was to evaluate the respiratory variation of the extrahepatic bile duct in morphology including shape, length and duct diameter on the breath-hold magnetic resonance cholangiopancreatography (MRCP) obtained during deep inspiration and deep expiration in patients with or without biliary diseases.

Materials and Methods

This study included 102 patients with or without biliary diseases. Breath-hold MRCP was obtained twice during the end-inspiration and the end-expiration. MRCP images were evaluated for the length, maximal diameter and “bowing” of the extrahepatic bile duct.

Results

In the normal group, the mean maximal diameter of the extrahepatic bile duct was significantly larger on the end-inspiratory MRCP (8.0±2.0 mm) than on the end-expiratory MRCP (7.3±1.8 mm) (P<.0001), while it was not significantly different in the dilated group. In the normal group, 25 (39%) of 65 patients had an increase in the mean maximal diameter of more than 1 mm at the end-inspiration, whereas 4 (11%) of 37 patients in the dilated group had it. The bowing of the extrahepatic bile duct on the end-inspiratory MRCP was observed in 60 (92%) of 65 normal patients, while it was seen in 22 (60%) of 37 patients with biliary dilatation (P<.0001).

Conclusion

Deep inspiratory and expiratory MRCP demonstrated the respiratory variations of the extrahepatic bile duct in the shape (bowing), length and maximal duct diameter in patients with nondilated bile ducts. Awareness of this normal phenomenon will be important for the correct interpretation of MRCP in patients with or without biliary diseases.     

Evaluation of Marfan patients status post valve-sparing aortic root replacement with 4D flow

Background

Over the past two decades elective valve-sparing aortic root replacement (V-SARR) has become more common in the treatment of patients with aortic root and ascending aortic aneurysms. Currently there are little data available to predict complications in the post-operative population. The study goal was to determine if altered flow patterns in the thoracic aorta, as measured by MRI, are associated with complications after V-SARR.

Methods

Time-resolved three-dimensional phase-contrast MRI (4D flow) was used to image 12 patients with Marfan syndrome after V-SARR. The patients were followed up for an average of 5.8 years after imaging and 8.2 years after surgery. Additionally 5 volunteers were imaged for comparison. Flow profiles were visualized during peak systole using streamlines. Wall shear stress estimates and normalized flow displacement were evaluated at multiple planes in the thoracic aorta.

Results

During the follow-up period, a single patient developed a Stanford Type B aortic dissection. At initial imaging, prior to the development of the dissection, the patient had altered flow patterns, wall shear stress estimates, and increased normalized flow displacement in the thoracic aorta in comparison to the remaining V-SARR patients and volunteers.

Conclusions

This is the first follow-up study of patients after 4D flow imaging. An aortic dissection developed in one patient with altered flow patterns and hemodynamic stresses in the thoracic aorta. These results suggest that flow and altered hemodynamics may play a role in the development of post-operative intramural hematomas and dissections.     

Gadolinium- and superparamagnetic-iron-oxide-enhanced MR findings of intrapancreatic accessory spleen in five patients

Purpose

The purposes of this study were to describe dynamic gadolinium-enhanced magnetic resonance imaging (MRI) findings of intrapancreatic accessory spleen(s) (IPAS) in five patients and to show how superparamagnetic iron oxide (SPIO) enhancement can be used for definite characterization in two cases.

Materials and Methods

An MRI database was searched for patients who had pancreatic tail lesions with imaging features compatible with IPAS between June 2005 and July 2007. Five (four male, one female) patients (age: mean±S.D., 58±9.8 years; range, 50–75 years) were identified. All patients were examined with standard gadolinium-enhanced MRI protocol. Additionally, two patients were examined with SPIO-enhanced MRI protocol. All MRI examinations were retrospectively and blindly evaluated by two radiologists for the predetermined findings, and their final diagnoses were noted.

Results

One pancreatic tail lesion was detected in each patient. All of these lesions were single, focal, well-marginated and located within 3 cm of the distal tail of the pancreas. The mean size (mean±S.D.) of the lesions was (2.02±0.64)×(1.72±0.42) cm², and all lesions had a rounded morphology. The signal intensity of all lesions was similar to that of the spleen on all sequences, including precontrast, postgadolinium and post-SPIO sequences. The reviewers confidently diagnosed IPAS in two patients who had SPIO-enhanced MRI. In the remaining three patients, the reviewers favored the diagnosis of IPAS based on the findings of standard gadolinium-enhanced MRI; however, they could not definitively exclude the other differential diagnoses.

Conclusion

The discovery of a well-marginated, rounded mass in the distal aspect of the tail of the pancreas with signal intensity features of the spleen on all precontrast and postgadolinium sequences suggests the diagnosis of IPAS. However, SPIO-enhanced MRI can be used to characterize the lesion and to establish the definite diagnosis of IPAS in case of clinical doubt.     

Hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide-enhanced magnetic resonance imaging in cirrhosis or chronic hepatitis: comparison of four magnetic resonance sequences for lesion conspicuity

Purpose

The aim of this study was to determine the adequate MR sequence for the lesion conspicuity of hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide (SPIO)-enhanced MRI.

Materials and Methods

SPIO-enhanced MRI was performed using a 1.5-T system. Among 25 patients with hypovascular hepatocellular nodules on contrast-enhanced dynamic CT (no early enhancement at arterial phase and hypoattenuation at equilibrium phase), 39 lesions with increased iron uptake on SPIO-enhanced MRI were evaluated. SPIO-enhanced MRI included (1) T1-weighted in-phase gradient recalled echo (GRE) images, (2) T2-weighted fast spin echo (FSE) images, (3) T2*-weighted GRE with moderate TE (7 ms) and (4) long TE (12 ms). The lesion-to-liver contrast-to-noise ratios of the hepatocellular nodule and the signal-to-noise ratio (SNR) of the hepatic parenchyma were calculated by one radiologist for a quantitative assessment. MR images were reviewed retrospectively by two independent radiologists to compare the subjective lesion conspicuity in each image set based on a four-point rating scale.

Result

The mean lesion-to-liver contrast-to-noise ratios with T2*-weighted GRE with moderate TE (7 ms) was highest (5.79±3.71) and was significantly higher than those with T1-weighted, in-phase images (3.79±3.23, P<.01), T2-weighted images (2.72±1.52, P<.001) and T2*-weighted GRE with long TE (12 ms) (3.93±2.69, P<.05). The subjective rating of lesion conspicuity was best on the T2*-weighted GRE with moderate TE (7 ms), followed by that on the T2*-weighted GRE with moderate TE (7 ms; P<.05).

Conclusion

T2*-weighted GRE sequence with moderate TE (7 ms) showed high lesion-to-liver contrast-to-noise ratios in hepatocellular lesions with increased iron uptake on SPIO-enhanced MRI, indicating better lesion conspicuity of hypointense hepatocellular nodules in cirrhosis or chronic hepatitis.     

An approach for computer-aided detection of brain metastases in post-Gd T1-W MRI

Purpose

To develop an approach for computer-aided detection (CAD) of small brain metastases in post-Gd T1-weighted magnetic resonance imaging (MRI).

Method

A set of unevenly spaced 3D spherical shell templates was optimized to localize brain metastatic lesions by cross-correlation analysis with MRI. Theoretical and simulation analyses of effects of lesion size and shape heterogeneity were performed to optimize the number and size of the templates and the cross-correlation thresholds. Also, effects of image factors of noise and intensity variation on the performance of the CAD system were investigated. A nodule enhancement strategy to improve sensitivity of the system and a set of criteria based upon the size, shape and brightness of lesions were used to reduce false positives. An optimal set of parameters from the FROC curves was selected from a training dataset, and then the system was evaluated on a testing dataset including 186 lesions from 2753 MRI slices. Reading results from two radiologists are also included.

Results

Overall, a 93.5% sensitivity with 0.024 of intra-cranial false positive rate (IC-FPR) was achieved in the testing dataset. Our investigation indicated that nodule enhancement was very effective in improving both sensitivity and specificity. The size and shape criteria reduced the IC-FPR from 0.075 to 0.021, and the brightness criterion decreases the extra-cranial FPR from 0.477 to 0.083 in the training dataset. Readings from the two radiologists had sensitivities of 60% and 67% in the training dataset and 70% and 80% in the testing dataset for the metastatic lesions <5 mm in diameter.

Conclusion

Our proposed CAD system has high sensitivity and fairly low FPR for detection of the small brain metastatic lesions in MRI compared to the previous work and readings of neuroradiologists. The potential of this method for assisting clinical decision- making warrants further evaluation and improvements.     

MR evaluation of breast lesions obtained by diffusion-weighted imaging with background body signal suppression (DWIBS) and correlations with histological findings

Objectives

Diffusion imaging represents a new imaging tool for the diagnosis of breast cancer. This study aims to investigate the role of diffusion-weighted MRI with background body signal suppression (DWIBS) for evaluating breast lesions.

Methods

90 patients were prospectively evaluated by MRI with STIR, TSE-T2, contrast enhanced THRIVE-T1 and DWIBS sequences. DWIBS were analyzed searching for the presence of breast lesions and calculating the ADC value. ADC values of ≤ 1.44 × 10^- 3 mm²/s were considered suspicious for malignancy. This analysis was then compared with the histological findings. Sensitivity, specificity, diagnostic accuracy (DA), positive predictive value (PPV) and negative (NPV) were calculated.

Results

In 53/90 (59%) patients, DWIBS indicated the presence of breast lesions, 16 (30%) with ADC values of  > 1.44 and 37 (70%) with ADC ≤ 1.44. The comparison with histology showed 25 malignant and 28 benign lesions. DWIBS sequences obtained sensitivity, specificity, DA, PPV and NPV values of 100, 82, 87, 68 and 100%, respectively.

Conclusion

DWIBS can be proposed in the MRI breast protocol representing an accurate diagnostic complement.     

Usefulness of the navigator-echo triggering technique for free-breathing three-dimensional magnetic resonance cholangiopancreatography

Purpose

To prospectively compare the navigator-echo triggering technique (navigator technique) and the conventional respiratory triggering technique using bellows (bellows technique) for free-breathing three-dimensional (3D) magnetic resonance cholangiopancreatography (MRCP) under clinical conditions.

Materials and methods

Forty patients referred for evaluation of biliary or pancreatic diseases underwent 3D MRCP examination using both navigator and bellows techniques. Two independent radiologists visually evaluated the image quality of 12 segments of the pancreaticobiliary tree in a blinded manner. In addition, the clarity of the lesion was compared between the two techniques in a side-by-side manner.

Result

MRCP images were successfully acquired using both techniques in all patients. No significant difference in acquisition time was found between the two techniques. The image quality was significantly better using the navigator technique than using the bellows technique for the following seven segments: the head, body, and tail of the pancreatic duct; right hepatic duct; anterior and posterior segments of the right hepatic duct; and cystic duct. The other segments (common hepatic and bile duct, left hepatic duct, medial and lateral segments of left hepatic duct, gallbladder) showed no significant difference. The clarity of lesion depiction was significantly better using the navigator technique than using the bellows technique.

Conclusion

Respiratory-triggered 3D MRCP using the navigator technique was shown to be feasible in routine clinical practice. The navigator technique improved the image quality of free-breathing 3D MRCP compared with the bellows technique. The clarity of lesion visualization was also better using the navigator technique than using the bellows technique.     

Noncontrast MRI with diffusion-weighted imaging as the sole imaging modality for detecting liver malignancy in patients with high risk for hepatocellular carcinoma

Purpose

To compare the diagnostic performance of the noncontrast MRI including DWI to the standard MRI for detecting hepatic malignancies in patients with chronic liver disease.

Materials and methods

We included 135 patients with 136 histologically-confirmed hepatocellular carcinomas (HCCs), 12 cholangiocarcinomas, and 34 benign lesions (≤ 2.0 cm), and 22 patients with cirrhosis but no focal liver lesion who underwent 3.0 T liver MRI. Noncontrast MRI set (T1- and T2-weighted images and DWI) and standard MRI set (gadoxetic acid-enhanced and noncontrast MRI) were analyzed independently by three observers to detect liver malignancies using receiver operating characteristic analysis.

Results

The Az value of the noncontrast MRI (mean, 0.906) was not inferior to that of the combined MRI (mean, 0.924) for detecting malignancies by all observers (P > 0.05). For each observer, no significant difference was found in the sensitivity and specificity between the two MRI sets for detecting liver malignancies and distinguishing them from benign lesions (P > 0.05), whereas negative predictive value was higher with the combined MRI than with the noncontrast MRI (P = 0.0001). When using pooled data, the sensitivity of the combined MRI (mean 94.8%) was higher than that of the noncontrast MRI (mean, 91.7%) (P = 0.001), whereas specificity was equivalent (78.6% vs 77.5%).

Conclusion

Noncontrast MRI including DWI showed reasonable performance compared to the combined gadoxetic acid-enhanced and noncontrast MRI set for detecting HCC and cholangiocarcinoma and differentiating them from benign lesions in patients with chronic liver disease.     

Pharmacokinetics of gadoversetamide injection, a gadolinium-based contrast agent, in pediatric patients

Objective

The pharmacokinetics of gadoversetamide were examined in pediatric patients scheduled to undergo contrast-enhanced MRI of the central nervous system.

Materials and Methods

One hundred patients received an intravenous injection of gadoversetamide at a dose of 0.1 mmol/kg for a contrast-enhanced MRI procedure. A subpopulation of 30 patients were enrolled to evaluate the pharmacokinetics of gadoversetamide in patients 2–11 and 12–18 years of age. Serial blood and urine samples were collected before and after the administration of gadoversetamide.

Results

The terminal half-life, initial concentration and area under the curve assessments for gadoversetamide showed no significant (P>.05) differences between the age groups or the sexes. Although no sex-related differences occurred in the volume of distribution or clearance, significant (P<.05) age-related differences were found, but once corrected for body mass or surface area the differences were no longer significant.

Conclusions

The pharmacokinetic behavior of gadoversetamide was not significantly altered by differences in age or sex in pediatric patients from 2 to 18 years of age. Although significant differences in volumes of distribution, and clearance occurred between the age groups, these differences appeared to depend on body size rather than on age in pediatric patients between 2 and 18 years of age.     

Diagnostic performance of apparent diffusion coefficient and quantitative kinetic parameters for predicting additional malignancy in patients with newly diagnosed breast cancer

Purpose

To evaluate the diagnostic performance of an apparent diffusion coefficient (ADC) and quantitative kinetic parameters in patients with newly diagnosed breast cancer.

Materials and Methods

We enrolled 169 lesions in 89 patients with breast cancer who underwent dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI). Comparisons between benign and malignant lesions were performed for lesion type (mass or nonmass-like enhancement), size (≥ 1 cm or < 1 cm), ADC, kinetic parameters and the presence of a US correlate.

Results

There were 63 benign and 106 malignant lesions. The mean size and initial peak enhancement of the benign lesions were significantly lower than those of malignant lesions (P < 0.001 for both). The ADC of the benign lesions was significantly higher than that of malignant lesions (1.42 × 10^− 3 mm²/sec vs. 1.04 × 10^− 3 mm²/sec; P < 0.001). The area under the receiver operating characteristic curve (AUC) for predicting malignancy was 0.87 for the combined parameters of size, ADC, and initial peak enhancement, which was higher than those of each parameter.

Conclusions

Combination of quantitative kinetic parameters and ADC showed higher diagnostic performance for predicting malignancy than each parameter alone for the evaluation of patients with breast cancer.     

Feasibility of post-gadolinium three-dimensional gradient-echo sequence to evaluate the pulmonary arterial vasculature

Purpose

To determine the feasibility of post-gadolinium three-dimensional gradient-echo (3D-GE) sequence for the evaluation of the pulmonary arterial vasculature in patients with suspected pulmonary embolism (PE) and in patients with a variety of other disease processes.

Materials and Methods

Twenty-six consecutive patients (18 females, 8 males; mean age±S.D., 46.6±21.1 years) who underwent chest magnetic resonance imaging (MRI) including post-gadolinium 3D-GE sequence for the evaluation of PE (Group A, n=13) and a variety of other disease processes (Group B, n=13) were included in the study. Post-gadolinium 3D-GE MR sequences were retrospectively, independently and blindly evaluated by two reviewers for the image quality of pulmonary arterial vasculature, and findings of PE and other disease processes. Clinical and imaging follow-up data for all patients were obtained. Interobserver agreement was calculated by kappa statistics.

Results

All central and lobar pulmonary arteries, 71.4–89.6% of segmental arteries and 46.7–52.7% of subsegmental arterial units in both groups were visualized with sufficient diagnostic image quality on post-gadolinium 3D-GE sequences. PE involving lobar and segmental arteries was diagnosed in two patients in each group. Other disease processes including pneumonia, lung nodules, superior vena cava stenosis, lung metastases, chronic lymphocytic leukemia and aortic aneurysm were detected in 10 of 26 patients. There was good to excellent interobserver agreement (0.73 to 1.00) for all findings.

Conclusion

Post-gadolinium 3D-GE sequence may be an alternative technique for the visualization of central, lobar and segmental arteries, and may diagnose PE and other pathologies involving the chest in different patient populations.     

Comparison of diffusion tensor,dynamic susceptibility contrast MRI and Tc-Tetrofosmin brain SPECT for the detection of recurrent high-grade glioma

Introduction

Treatment induced necrosis is a relatively frequent finding in patients treated for high-grade glioma. Differentiation by imaging modalities between glioma recurrence and treatment induced necrosis is not always straightforward. This is a comparative study of diffusion tensor imaging (DTI), dynamic susceptibility contrast MRI and ^99mTc-Tetrofosmin brain single-photon emission computed tomography (SPECT) for differentiation of recurrent glioma from treatment induced necrosis.

Methods

A prospective study was made of 30 patients treated for high-grade glioma who had suspected recurrent tumor on follow-up MRI. All had been treated by surgical resection of the tumor followed by standard postoperative radiotherapy with chemotherapy. No residual tumor had been found on brain imaging immediately after the initial treatment. All the patients were studied with dynamic susceptibility contrast brain MRI and, within a week, ^99mTc-Tetrofosmin brain SPECT.

Results

Both ^99mTc-Tetrofosmin brain SPECT and dynamic susceptibility contrast MRI could discriminate between tumor recurrence and treatment induced necrosis with 100% sensitivity and 100% specificity. An apparent diffusion coefficient (ADC) ratio cut-off value of 1.27 could differentiate recurrence from treatment induced necrosis with 65% sensitivity and 100% specificity and a fractional anisotropy (FA) ratio cut-off value of 0.47 could differentiate recurrence from treatment induced necrosis with 57% sensitivity and 100% specificity. A significant correlation was demonstrated between ^99mTc-Tetrofosmin uptake ratio and rCBV (P = 0.003).

Conclusions

Dynamic susceptibility contrast MRI and brain SPECT with ^99mTc-Tetrofosmin had the same accuracy and may be used to detect recurrent tumor following treatment for glioma. DTI also showed promise for the detection of recurrent tumor, but was inferior to both dynamic susceptibility contrast MRI and brain SPECT.     

Sensitivity of multi-parametric MRI to the compressive state of the isolated intervertebral discs

Objective

Magnetic resonance imaging (MRI) offers great potential as a sensitive and noninvasive technique for describing the alterations in mechanical properties, as shown in vitro on intervertebral disc (IVD) or cartilage tissues. However, in vivo, the IVD is submitted to complex loading stimuli. Thus, the present question focuses on the influence of the mechanical loading during an MRI acquisition on the relaxation times, magnetization transfer and diffusion parameters within the IVD.

Methods

An apparatus allowing the compression of isolated IVDs was designed and manufactured in acrylonitrile butadiene styrene. IVDs were dissected from fresh young bovine tail, measured for their thickness and submitted to compression just before the MRI acquisition. Six discs received 0% (platen positioned at the initial disc thickness), 5% (platen positioned at 95% of the initial disc thickness), 10%, 20% and 40% deformation. The MRI parameters were compared between the loading states using mean and standard deviation for T1 and T2, and matrix subtraction for Magnetization Transfer, fractional anisotropy and apparent diffusion coefficient.

Results

The compression of the IVD did not lead to any significant change of the MRI parameters, except for the diffusion that decreased in the direction of the compressive stress.

Discussion

This experimental in vitro study shows that multi-parametric MRI on isolated discs in vitro is not sensitive to compression or to the partial confined relaxation that followed the compression.     

MR T1ρ quantification of cartilage focal lesions in acutely injured knees: correlation with arthroscopic evaluation

Objective

Quantitative T₁ρ MRI has been suggested as a promising tool to detect changes in cartilage composition that are characteristic of cartilage damage and degeneration. The objective of this study was to evaluate the capability of MR T₁ρ to detect cartilage lesions as evaluated by arthroscopy in acutely ACL-injured knees and to compare with the Whole-Organ Magnetic Resonance Imaging Score (WORMS) using clinical standard MRI.

Method

Ten healthy controls (mean age 35) with no ACL injury or history of osteoarthritis (OA) and 10 patients with acute ACL injuries (mean age 39) were scanned at 3 Tesla (3 T). ACL patients underwent ACL reconstruction, where focal lesions were graded according to an Outerbridge grading system during arthroscopic evaluation. Normalized MR T₁ρ values (T₁ρ z-scores normalized to control values in matched regions) in full thickness, and superficial and deep layers of cartilage were compared between defined sub-compartments with and without focal lesions. Intraclass (ICC) correlation and the root mean square coefficient of variation (RMS-CV) were performed to evaluate the inter-observer reproducibility of T₁ρ quantification. Sub-compartments of cartilage were also evaluated using WORMS scoring and compared to their Outerbridge score respectively.

Results

The inter-observer ICC and the RMS-CV of the sub-compartment T₁ρ quantification were 0.961 and 3.9%, respectively. The average T₁ρ z-scores were significantly increased in sub-compartments with focal lesions compared to those without focal lesions and to the control cohort (p < 0.05).

Conclusion

Our results indicate that T₁ρ provided a better diagnostic capability than clinical standard MRI grading in detecting focal cartilage abnormalities after acute injuries. Quantitative MRI may have great potential in detecting cartilage abnormalities and degeneration non-invasively, which are occult with standard morphological MRI.     

Diagnostic value of elastosonography for thyroid microcarcinoma

Objective

To assess the diagnostic value of elastosonography for thyroid microcarcinoma (TMC), particularly with regard to elasticity score (ES) and strain ratio (SR).

Methods

Conventional ultrasound and elastosonography were performed for 487 thyroid micronodules before surgery. We set the histology as the reference standard. The ES and SR values, as well as their diagnostic threshold and efficiency, were compared and analyzed by the receiver-operating characteristic (ROC) curve. Additional comparisons between TMC patients with and without extracapsular extension were also performed.

Results

Statistically significant differences (P < 0.05) in both ES and SR values were detected among the TMC and benign groups. The area under the ROC curve of SR was significantly greater than that of ES (0.956 and 0.844, respectively; P < 0.05). Using ES ? 3 and SR ? 3.65 as diagnostic threshold values, the diagnostic sensitivity, specificity, and accuracy of ES for differentiating benign and malignant nodules were 79.9%, 72.3%, and 80.5%, respectively, whereas those of SR were 86.6%, 85.3%, and 89.4%, respectively. The maximum diameter, microcalcification status, aspect ratio, bilateral cervical lymph node metastasis, and SR values of nodules with extracapsular extension (A1 subgroup) were greater than those of nodules without extracapsular extension (A2 subgroup).

Conclusions

Elasticity imaging technology not only can help differentiate between benign and malignant thyroid micronodules but also allow SR values to provide accurate and objective information on tissue hardness and to predict TMC extracapsular extension or even bilateral cervical lymph node metastasis.     

MR findings of focal eosinophilic liver disease using gadoxetic acid

Purpose

The purpose of this study was to describe magnetic resonance (MR) findings of focal eosinophilic liver disease using gadoxetic acid (Gd-EOB-DTPA).

Materials and Methods

Nineteen patients (M:F=14:5; age range, 26–66 years; mean age, 50 years) with 35 focal eosinophilic liver lesions were included after reviewing the medical records of 482 patients who underwent Gd-EOB-DTPA-enhanced MR imaging (MRI) on a 3.0-T unit between April 2008 and June 2009. The diagnosis of focal eosinophilic liver disease was established by means of percutaneous liver biopsy or surgery and consistent clinical findings. Two radiologists retrospectively reviewed MR images with consensus. Margin, shape and distribution of the lesions were analyzed. We also evaluated signal intensity of focal hepatic lesions on T₁- and T₂-weighted images and patterns of enhancement in dynamic contrast study.

Results

The mean diameter of the lesions was 1.7 cm (range, 0.7–6.1 cm). Most of the focal eosinophilic liver lesions [n=31/35 (88.6%)] had poorly defined margins. They were usually isointense or slightly hypointense [n=34/35 (97.2%)] on T₁-weighted images and hyperintense [n=32/35 (91.4%)] on T₂-weighted images. Dynamic study showed enhancement (rim or homogeneous) on the arterial phase [n=21/35 (60%)] and hypointensity on the late venous phase [n=31/35 (88.6%)]. All the lesions were hypointense on the hepatobiliary phase images.

Conclusion

Focal eosinophilic liver lesions tend to be hyperintense on the arterial phase and hypointense on the late venous phase during dynamic study of Gd-EOB-DTPA-enhanced MRI. Although these findings mimic other focal hepatic lesions, poorly defined margins of the lesions and peripheral eosinophilia might help distinguish focal eosinophilic liver disease from other hepatic lesions.     

Artifacts in magnetic resonance imaging after surgical resection of brain tumors

Background

Since the advent of magnetic resonance imaging, metal artifacts have posed an important diagnostic problem in different fields of medicine. However, this has not been systematically studied in patients undergoing surgery for brain tumors.

Objective

This study was planned to assess whether metal artifacts can occur in patients undergoing brain surgery without metallic implants.

Methods

Of 40 individuals who could be included because of having a pre- and postoperative MRI and a postoperative computed tomography (CT) scan or a conventional skull X-ray for the detection of metallic artifacts, 26 patients agreed to participate in this study and gave informed consent.

Results

Twenty-six subjects, 12 males and 14 females, with an age range of 12 to 54 years, were included in the study. Four patients were found to have gross metal particles in their postoperative brain CTs and were excluded. Of the remaining 22 subjects, 7 patients (31.8%) had metallic artifacts.

Conclusion

Our study showed that simple bone drilling or chiseling during surgical manipulation of skull bones may result in separation of very tiny metal particles which can remain in the surgical site and cause artifacts in postoperative MRIs. This finding appeared to be independent of factors such as age, sex, tumor/incision site, tumor size, pathologic tumor type, total radiation dose, operation–MRI time interval and sequence of MRI.     

Impact of diffusion-weighted MR imaging on the characterization of small hepatocellular carcinoma in the cirrhotic liver

Purpose

The purpose of this study was to determine whether or not adding diffusion-weighted magnetic resonance imaging (DWI) to conventional magnetic resonance (MR) imaging sequences improves the characterization of small hepatocellular carcinoma (HCC) (≤2 cm) in the setting of cirrhotic liver compared to conventional sequences alone.

Materials and Methods

A total of 62 cirrhotic liver patients with 82 nodules smaller than 2 cm in diameter were enrolled, and all lesions were pathologically confirmed. For the first reading session, which included precontrast T1- and T2-weighted images and T1 dynamic contrast-enhanced images, preindicated lesions by a study coordinator were characterized by two radiologists. They determined the confidence levels in consensus for the presence of small HCC into four grades. In another session, respiratory-triggered diffusion-weighted MR images (b factor=50, 400 and 800 s/mm²) were added to the previously reviewed images, and the same two radiologists again determined the confidence levels. The diagnostic performance of the combined DWI–conventional sequences set and the conventional sequences alone set was evaluated using receiver operating characteristic curves. Sensitivity and specificity values for characterizing small HCCs were also calculated.

Results

The area under the receiver operating characteristic curve for the second interpretation session (0.86) was significantly higher (P=.038) than that of the first session (0.76). The sensitivity was significantly increased from 75.7% to 87.8% by adding DWI to the conventional sequences (P=.015). No significant differences were observed for specificity values.

Conclusion

Adding DWI to conventional imaging modalities improves the diagnosis of small HCCs in the cirrhotic liver in terms of diagnostic performance and sensitivity by increasing reader confidence.     

Gadoxetic acid-enhanced MRI compared with CT during angiography in the diagnosis of hepatocellular carcinoma

Purpose

To assess the value of gadoxetic acid-enhanced magnetic resonance imaging (MRI) for the pre-therapeutic detection of hepatocellular carcinoma (HCC) using receiver operating characteristic (ROC) analysis with the combination of computed tomography (CT) arterial portography and CT hepatic arteriography (CTAP/CTHA).

Materials and Methods

A total of 54 consecutive patients with 87 nodular HCCs were retrospectively analyzed. All HCC nodules were confirmed pathologically. Three blinded readers independently reviewed 432 hepatic segments, including 78 segments with 87 HCCs. Each reader read two sets of images: Set 1, CTAP/CTHA; Set 2, gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and diffusion-weighted imaging (DWI). The ROC method was used to analyze the results. The sensitivity, specificity, positive predictive value, negative predictive value and sensitivity according to tumor size were evaluated.

Results

For each reader, the area under the curve was significantly higher for Set 2 than for Set 1. The mean area under the curve was also significantly greater for Set 2 than for Set 1 (area under the curve, 0.98 vs. 0.93; P = .0009). The sensitivity was significantly higher for Set 2 than for Set 1 for all three readers (P = .012, .013 and .039, respectively). The difference in the specificity, positive predictive values and negative predictive values of the two modalities for each reader was not significant (P > .05).

Conclusion

Gadoxetic acid-enhanced MRI including a gradient dual-echo sequence and DWI is recommended for the pre-therapeutic evaluation of patients with HCC.     

A new vascular coupling device: Assessment of MRI issues at 3-tesla

Objective

Vascular grafting frequently involves a time-consuming operation. A new vascular coupling device (VCD) made from metallic material was recently developed that may be advantageous because of the reduced operative time and decreased patient risks. Because of the metal, there are safety concerns related to MRI. Therefore, the purpose of this investigation was to use standardized testing techniques to evaluate MRI issues for this VCD in association with a 3-Tesla MR system.

Methods

The VCD (corlife oHG, Hannover, Germany) was evaluated for magnetic field interactions (translational attraction and torque), MRI-related heating, and artifacts at 3-Tesla. MRI-related heating was assessed with the VCD in a gelled-saline-filled phantom with MRI performed at a whole body averaged SAR of 2.9-W/kg for 15-min. Artifacts were assessed using T1-weighted, spin echo, and gradient echo pulse sequences.

Results

The VCD exhibited minor magnetic field interactions and minimal heating (maximum temperature elevation, 1.8 °C). Artifacts were relatively small in relation to the size and shape of this implant. The lumen of the VCD could not be visualized using the gradient echo pulse sequence.

Conclusions

The metallic VCD that underwent evaluation is MR conditional for a patient undergoing an MRI procedure at 3-Tesla or less.