Contrast Material-enhanced Magnetic Resonance Research Articles

Computerized Segmentation Method for Nonmasses on Breast DCE-MRI Images Using ResUNet++ with Slice Sequence Learning and Cross-Phase Convolution.

The purpose of this study was to develop a computerized segmentation method for nonmasses using ResUNet++ with a slice sequence learning and cross-phase convolution to analyze temporal information in breast dynamic contrast material-enhanced magnetic resonance imaging (DCE-MRI) images. The dataset consisted of a series of DCE-MRI examinations from 54 patients, each containing three-phase images, which included one image that was acquired before contrast injection and two images that were acquired after contrast injection. In the proposed method, the region of interest (ROI) slice images are first extracted from each phase image. The slice images at the same position in each ROI are stacked to generate a three-dimensional (3D) tensor. A cross-phase convolution generates feature maps with the 3D tensor to incorporate the temporal information. Subsequently, the feature maps are used as the input layers for ResUNet++. New feature maps are extracted from the input data using the ResUNet++ encoders, following which the nonmass regions are segmented by a decoder. A convolutional long short-term memory layer is introduced into the decoder to analyze a sequence of slice images. When using the proposed method, the average detection accuracy of nonmasses, number of false positives, Jaccard coefficient, Dice similarity coefficient, positive predictive value, and sensitivity were 90.5%, 1.91, 0.563, 0.712, 0.714, and 0.727, respectively, larger than those obtained using 3D U-Net, V-Net, and nnFormer. The proposed method achieves high detection and shape accuracies and will be useful in differential diagnoses of nonmasses.

Collateral and permeability imaging derived from dynamic contrast material-enhanced MR angiography in prediction of PH 2 hemorrhagic transformation after acute ischemic stroke: a pilot study.

To evaluate the role of collateral and permeability imaging derived from dynamic contrast material-enhanced magnetic resonance angiography to predict PH 2 hemorrhagic transformation in acute ischemic stroke. The secondary analysis of a published data from participants with acute ischemic stroke. The multiphase collateral map and permeability imaging were generated by using dynamic signals from dynamic contrast material-enhanced magnetic resonance angiography obtained at admission. To identify independent predictors of PH 2 hemorrhagic transformation, age, sex, risk factors, baseline National Institutes of Health Stoke Scale (NIHSS) score, baseline DWI lesion volume, collateral-perfusion status, mode of treatment, and successful early reperfusion were evaluated with multiple logistic regression analyses and the significance of permeability imaging in prediction of PH 2 hemorrhagic transformation was evaluated by subgroup analysis. In 115 participants, including 70 males (mean (SD) age, 69 (12) years), PH 2 hemorrhagic transformation occurred in 6 participants with very poor collateral-perfusion status (MAC 0). MAC 0 (OR, 0.06; 95% CI, 0.01, 0.74; P = .03) was independently associated with PH 2 hemorrhagic transformation. In 22 participants with MAC 0, the permeable signal on Kep permeability imaging was the only significant characteristic associated with PH 2 hemorrhagic transformation (P = .009). The specificity of Kep permeability imaging was 93.8% (95% confidence interval: 69.8, 99.8) in predicting PH 2 hemorrhagic transformation. Individual-based prediction of PH 2 hemorrhagic transformation in patients with acute ischemic stroke may be possible with multiphase collateral map and permeability imaging derived from dynamic contrast material-enhanced magnetic resonance angiography.

MR Lymphangiography in Children: Technique and Potential Applications.

The lymphatic system, an important component of the circulatory system with essential physiologic functions, can be affected by various disease processes. There has been a delay in the development of effective imaging methods for the lymphatic system due to its small size, which limits visualization as well as introduction of contrast material. Traditionally, the lymphatic system has been imaged by injecting contrast material or radiotracers into the feet or hands. This is not sufficient for assessment of the central conducting lymphatics (CCLs) (such as the thoracic duct or the cisterna chyli). Fluoroscopic intranodal lymphangiography with injection of oil-based contrast material into groin lymph nodes improves visualization of CCLs but is limited in practice owing to the use of radiation and the potential risk for paradoxical embolization in children with left-to-right shunt. Dynamic contrast material-enhanced (DCE) magnetic resonance (MR) lymphangiography, which is performed by injecting gadolinium-based contrast material into groin lymph nodes, overcomes these limitations. T2-weighted imaging plays a complementary role to DCE MR lymphangiography in the assessment of CCLs. DCE MR lymphangiography demonstrates preserved integrity or any abnormality of the CCLs (including blockage or leak). The technique has recently been used in evaluating pulmonary lymphatic perfusion syndrome in children with plastic bronchitis, neonatal lymphatic flow disorders, and nontraumatic chylothorax. It is useful in identification of the source of chylous ascites and contributes to understanding of the anatomy of lymphatic malformations. It is successfully used for planning of embolization of aberrant lymphatic channels in a variety of lymphatic flow disorders. This review discusses the anatomy and function of the lymphatic system, the evolution of imaging of the lymphatic system, and DCE MR lymphangiography technique and its applications in children. ©RSNA, 2017.

Heterogeneous Enhancement Patterns of Tumor-adjacent Parenchyma at MR Imaging Are Associated with Dysregulated Signaling Pathways and Poor Survival in Breast Cancer.

Purpose To identify the molecular basis of quantitative imaging characteristics of tumor-adjacent parenchyma at dynamic contrast material-enhanced magnetic resonance (MR) imaging and to evaluate their prognostic value in breast cancer. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 10 quantitative imaging features depicting tumor-adjacent parenchymal enhancement patterns were extracted and screened for prognostic features in a discovery cohort of 60 patients. By using data from The Cancer Genome Atlas (TCGA), a radiogenomic map for the tumor-adjacent parenchymal tissue was created and molecular pathways associated with prognostic parenchymal imaging features were identified. Furthermore, a multigene signature of the parenchymal imaging feature was built in a training cohort (n = 126), and its prognostic relevance was evaluated in two independent cohorts (n = 879 and 159). Results One image feature measuring heterogeneity (ie, information measure of correlation) was significantly associated with prognosis (false-discovery rate < 0.1), and at a cutoff of 0.57 stratified patients into two groups with different recurrence-free survival rates (log-rank P = .024). The tumor necrosis factor signaling pathway was identified as the top enriched pathway (hypergeometric P < .0001) among genes associated with the image feature. A 73-gene signature based on the tumor profiles in TCGA achieved good association with the tumor-adjacent parenchymal image feature (R2 = 0.873), which stratified patients into groups regarding recurrence-free survival (log-rank P = .029) and overall survival (log-rank P = .042) in an independent TCGA cohort. The prognostic value was confirmed in another independent cohort (Gene Expression Omnibus GSE 1456), with log-rank P = .00058 for recurrence-free survival and log-rank P = .0026 for overall survival. Conclusion Heterogeneous enhancement patterns of tumor-adjacent parenchyma at MR imaging are associated with the tumor necrosis signaling pathway and poor survival in breast cancer. © RSNA, 2017 Online supplemental material is available for this article.

US Evaluation of Juvenile Idiopathic Arthritis and Osteoarticular Infection

Juvenile idiopathic arthritis (JIA) and osteoarticular infection can cause nonspecific articular and periarticular complaints in children. Although contrast material-enhanced magnetic resonance imaging is the reference standard imaging modality, musculoskeletal ultrasonography (US) is emerging as an important adjunct imaging modality that can provide valuable information relatively quickly without use of radiation or the need for sedation. However, diagnostic accuracy requires a systemic approach, familiarity with various US techniques, and an understanding of maturation-related changes. Specifically, the use of dynamic, Doppler, and/or multifocal US assessments can help confirm sites of disease, monitor therapy response, and guide interventions. In patients with JIA, ongoing synovial inflammation can lead to articular and periarticular changes, including synovitis, tenosynovitis, cartilage damage, bone changes, and enthesopathy. Although these findings can manifest in adult patients with rheumatoid arthritis, important differences and pitfalls exist because of the unique changes associated with an immature and maturing skeleton. In patients who are clinically suspected of having osteoarticular infection, the inability of US to evaluate the bone marrow decreases its sensitivity. Therefore, the US findings should be interpreted with caution because juxtacortical inflammation is suggestive, but neither sensitive nor specific, for underlying osteomyelitis. Similarly, the absence of a joint effusion makes septic arthritis extremely unlikely but not impossible. US findings of JIA and osteoarticular infection often overlap. Although certain clinical scenarios, laboratory findings, and imaging appearances can favor one diagnosis over the other, fluid analysis may still be required for definitive diagnosis and optimal treatment. US is the preferred modality for fluid aspiration and administering intra-articular corticosteroid therapy. © RSNA, 2017.

Dynamic Contrast-enhanced MR Imaging Parameters in Bone Metastases from Non-Small Cell Lung Cancer: Comparison between Lesions with and Lesions without Epidermal Growth Factor Receptor Mutation in Primary Lung Cancer.

Purpose To compare dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging parameters between metastatic bone lesions with and without the epidermal growth factor receptor (EGFR) mutation in consecutive patients with primary non-small cell lung cancer (NSCLC). Materials and Methods This study was approved by the institutional review board. Forty-seven patients with NSCLC and a confirmed EGFR mutation status (27 patients were positive and 26 were negative for EGFR mutation), who underwent DCE MR imaging for bone metastases between November 2012 and March 2016, were included in this study. Two radiologists independently analyzed the volume transfer constant (Ktrans), reflux rate (kep), and volume fraction of the extravascular extracellular matrix (ve) using image processing software. Intergroup comparisons of the mean measured parameters were performed with the Mann-Whitney U test. Interobserver agreement was calculated with the intraclass correlation coefficient. Results There was a high level of agreement between the two reviewers for all three parameters (intraclass correlation coefficient = 0.95 for Ktrans, 0.97 for kep, and 0.91 for ve). Ktrans was significantly higher in the EGFR mutation-positive group (P = .039 for reviewer 1, P = .032 for reviewer 2). kep was also higher in the EGFR mutation-positive group but showed statistical significance only in the evaluation performed by one reviewer (P = .048 for reviewer 2, P = .058 for reviewer 1). No significant difference was observed in ve (P = .873 for reviewer 1, P = .889 for reviewer 2). Conclusion The differences in the DCE MR imaging parameters between metastatic bone lesions with and without EGFR mutations in primary NSCLC may be attributed to differences in the vascular structure related to angiogenesis stimulated by the activation of the EGFR signaling pathway. © RSNA, 2017 Online supplemental material is available for this article.

Risk-stratified versus Non-Risk-stratified Diagnostic Testing for Management of Suspected Acute Biliary Obstruction: Comparative Effectiveness, Costs, and the Role of MR Cholangiopancreatography.

Purpose To analyze the cost-effectiveness of the American Society for Gastrointestinal Endoscopy (ASGE) risk stratification guidelines versus magnetic resonance (MR) cholangiopancreatography-based treatment of patients with possible choledocholithiasis. Materials and Methods A decision-analytic model was constructed to compare cost and effectiveness of three diagnostic strategies for gallstone disease with possible choledocholithiasis: noncontrast MR cholangiopancreatography, contrast material-enhanced MR imaging/MR cholangiopancreatography, and ASGE risk stratification guidelines for diagnostic evaluation recommending endoscopy (high risk), MR cholangiopancreatography (intermediate risk), or no test (low risk). Analysis was performed from a U.S. health system perspective over 1-year and lifetime horizons. The model accounted for benign and malignant causes of biliary obstruction and procedural complications. Cost information was based on Medicare reimbursements. Sensitivity analysis assessed the impact of parameter variability on model results. Results Noncontrast MR cholangiopancreatography was most cost-effective in 45-55-year-old patients (less than $100 000 per quality-adjusted life-year [QALY] gained), while contrast-enhanced MR imaging was favored in younger adults. Risk-stratified testing was less costly than MR cholangiopancreatography, with long-term savings of $1870 and $2068 versus noncontrast and contrast-enhanced MR cholangiopancreatography, respectively, but was also less effective (-0.1814, -0.1831 QALY, respectively). The lifetime incremental cost per QALY for noncontrast MR cholangiopancreatography was $10 311. Contrast-enhanced MR imaging was favored with pretest probabilities of biliary stricture or malignancy 0%-73% for patients aged 20-44 years. For patients older than 55 years, ASGE guidelines maximized QALYs at the lowest cost. Conclusion Although adults older than 55 years of age are optimally evaluated by using ASGE guidelines, younger patients suspected of having acute biliary obstruction likely benefit from MR cholangiopancreatography rather than risk-stratified diagnostic imaging because of improved detection of choledocholithiasis and alternative causes of biliary obstruction. © RSNA, 2017 Online supplemental material is available for this article.

Transient Bone Marrow Edema Syndrome versus Osteonecrosis: Perfusion Patterns at Dynamic Contrast-enhanced MR Imaging with High Temporal Resolution Can Allow Differentiation.

Purpose To prospectively evaluate the perfusion patterns at quantitative dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging of transient bone marrow edema syndrome (TBMES) and avascular osteonecrosis. Materials and Methods Institutional review board approval and written informed consent were obtained. Thirty-two patients (21 men, 11 women; mean age, 48 years; 26 hips, 10 knees) underwent conventional MR imaging and a dynamic contrast-enhanced three-dimensional spoiled gradient-echo sequence at 3 T. Parameter maps for mean transit time (MTT) and plasma flow (PF) were evaluated qualitatively and quantitatively. Differences in perfusion patterns were analyzed by using the Fisher exact test. Regions of interest were drawn in areas of high PF and long MTT on each parametric map. Mean, median, standard deviation, minimum, and maximum values were determined. TBMES and osteonecrosis were compared statistically by using the Mann-Whitney U and Wilcoxon signed-rank tests, with a P value of less than .05 considered indicative of a significant difference. Results Nineteen joints with TBMES and 17 joints with osteonecrosis were evaluated. TBMES joints showed a subchondral elongated area of high PF and low MTT that was surrounded by an area of long MTT and low PF. Osteonecrosis joints showed a subchondral area with low or no detectable PF and MTT adjacent to the joint surface, which was surrounded by a rim of high PF and intermediate MTT. Patterns for TBMES and osteonecrosis did not overlap. A significant difference (P < .001) in PF in the immediate subchondral area was found between TBMES and osteonecrosis; in joints with osteonecrosis, this was comparable to background noise, and therefore, could not be quantified. In the circumscribed rim of high PF and intermediate MTT, which was only found in joints with osteonecrosis, mean ± standard deviation PF was 18.9 mL/100 mL per minute ± 11.0 and mean MTT was 213.3 seconds ± 56.8. No significant difference between TBMES and osteonecrosis was found for MTT (P = .09) and PF (P = .75) in the surrounding area. Conclusion Parameter maps derived at dynamic contrast-enhanced MR imaging with high temporal resolution can allow differentiation of osteonecrosis from TBMES in hip and knee joints. © RSNA, 2016 Online supplemental material is available for this article.

Imaging Biomarkers of Tumor Response in Neuroendocrine Liver Metastases Treated with Transarterial Chemoembolization: Can Enhancing Tumor Burden of the Whole Liver Help Predict Patient Survival?

Purpose To investigate whether whole-liver enhancing tumor burden [ETB] can serve as an imaging biomarker and help predict survival better than World Health Organization (WHO), Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST (mRECIST), and European Association for the Study of the Liver (EASL) methods in patients with multifocal, bilobar neuroendocrine liver metastases (NELM) after the first transarterial chemoembolization (TACE) procedure. Materials and Methods This HIPAA-compliant, institutional review board-approved retrospective study included 51 patients (mean age, 57.8 years ± 13.2; range, 13.5-85.8 years) with multifocal, bilobar NELM treated with TACE. The largest area (WHO), longest diameter (RECIST), longest enhancing diameter (mRECIST), largest enhancing area (EASL), and largest enhancing volume (ETB) were measured at baseline and after the first TACE on contrast material-enhanced magnetic resonance images. With three-dimensional software, ETB was measured as more than 2 standard deviations the signal intensity of a region of interest in normal liver. Response was assessed with WHO, RECIST, mRECIST, and EASL methods according to their respective criteria. For ETB response, a decrease in enhancement of at least 30%, 50%, and 65% was analyzed by using the Akaike information criterion. Survival analysis included Kaplan-Meier curves and Cox regressions. Results Treatment response occurred in 5.9% (WHO criteria), 2.0% (RECIST), 25.5% (mRECIST), and 23.5% (EASL criteria) of patients. With 30%, 50%, and 65% cutoffs, ETB response was seen in 60.8%, 39.2%, and 21.6% of patients, respectively, and was the only biomarker associated with a survival difference between responders and nonresponders (45.0 months vs 10.0 months, 84.3 months vs 16.7 months, and 85.2 months vs 21.2 months, respectively; P < .01 for all). The 50% cutoff provided the best survival model (hazard ratio [HR]: 0.2; 95% confidence interval [CI]: 0.1, 0.4). At multivariate analysis, ETB response was an independent predictor of survival (HR: 0.2; 95% CI: 0.1, 0.6). Conclusion Volumetric ETB is an early treatment response biomarker and surrogate for survival in patients with multifocal, bilobar NELM after the first TACE procedure. © RSNA, 2016.

Blood-Brain Barrier Leakage in Patients with Early Alzheimer Disease.

Purpose To investigate whether the blood-brain barrier (BBB) leaks blood-circulating substances in patients with early forms of Alzheimer disease (AD), and if so, to examine the extent and pattern of leakage. Materials and Methods This study was approved by the local medical ethical committees of the Maastricht University Medical Center and Leiden University Medical Center, and written informed consent was obtained from all subjects. For this pilot study, 16 patients with early AD and 17 healthy age-matched control subjects underwent dynamic contrast material-enhanced magnetic resonance (MR) imaging sequence with dual time resolution for 25 minutes. The Patlak graphical approach was used to quantify the BBB leakage rate and local blood plasma volume. Subsequent histogram analysis was used to determine the volume fraction of the leaking brain tissue. Differences were assessed with linear regression analysis, adjusted for confounding variables. Results The BBB leakage rate was significantly higher in patients compared with that in control subjects in the total gray matter (P < .05) and cortex (P = .03). Patients had a significantly higher volume fraction of the leaking brain tissue in the gray matter (P = .004), normal-appearing white matter (P < .04), deep gray matter (P = .01), and cortex (P = .004). When all subjects were considered, scores on the Mini-Mental State Examination decreased significantly with increasing leakage in the deep gray matter (P = .007) and cortex (P < .05). Conclusion The results of this study showed global BBB leakage in patients with early AD that is associated with cognitive decline. A compromised BBB may be part of a cascade of pathologic events that eventually lead to cognitive decline and dementia. ©RSNA, 2016 Online supplemental material is available for this article.

Predictors of Clinical Outcome after Prostate Artery Embolization with Spherical and Nonspherical Polyvinyl Alcohol Particles in Patients with Benign Prostatic Hyperplasia.

Purpose To assess predictors of outcome after prostate artery embolization (PAE) for benign prostatic hyperplasia with spherical particle polyvinyl alcohol (sPVA) and compare outcomes with the use of nonspherical particle polyvinyl alcohol (nsPVA). Materials and Methods This was a single-center retrospective institutional review board-approved study conducted from 2009 to 2015 in patients undergoing PAE with sPVA (n = 186; mean age ± standard deviation, 65.5 years ± 7.7) and nsPVA (n = 300; mean age, 65.3 years ± 7.6). The two cohorts were compared and analyzed for predictors of outcome with a Cox proportional hazards model and linear regression. Post-PAE prostate ischemia was measured with contrast material-enhanced magnetic resonance (MR) imaging in 23 patients with nsPVA and 25 patients with sPVA. The 24-hour post-PAE prostate-specific antigen (PSA) level was registered in 133 patients with sPVA. Prognostic values of MR imaging and PSA levels 24 hours after PAE were assessed with Cox and random-effects regressions. Results Predictors of clinical failure were older age (age over 65 years, P = .002), unilateral procedure (P = .002), and higher baseline International Prostate Symptom Score (IPSS, P = .033). Adjusted hazard ratio for clinical failure of sPVA was 1.273 (P = .16). Acute urinary retention was a predictor of lower IPSS after PAE (P = .002). The mean proportion of prostate ischemia was 11% with sPVA and 10% with nsPVA (P = .65). Lower IPSS after PAE was associated with a higher proportion of prostate ischemia (P = .009). Patients with a PSA level of at least 75 ng/mL (75 μg/L) 24 hours after PAE had a greater decrease in IPSS (P = .01). Prostate ischemic volume and PSA level 24 hours after PAE were correlated (Pearson r = 0.64, P = .014). Conclusion Clinical outcome was similar after PAE with sPVA and nsPVA. Younger age (up to 65 years), bilateral PAE, lower baseline IPSS, and acute urinary retention were predictors of better clinical outcome. The PSA level 24 hours after PAE correlated with prostate ischemia, and both correlated with clinical outcome. (©) RSNA, 2016.

Tumor Heterogeneity in Lung Cancer: Assessment with Dynamic Contrast-enhanced MR Imaging.

Purpose To evaluate histogram and texture parameters on pretreatment dynamic contrast material-enhanced (DCE) magnetic resonance (MR) images in lung cancer in terms of temporal change, optimal time for analysis, and prognostic potential. Materials and Methods This retrospective study was approved by the institutional review board, and the requirement to obtain informed consent was waived. Thirty-eight patients with pathologically proved lung cancer undergoing standard pretreatment DCE MR imaging were included. A fat-suppressed, T1-weighted, volume-interpolated breath-hold MR sequence was performed every 30 seconds for 300 and 480 seconds after contrast material administration. A region of interest was manually drawn in the largest cross-sectional area of the tumor on DCE MR images to extract semiquantitative perfusion, histogram, and texture parameters. Predictability of 2-year progression-free survival (PFS) was analyzed by using the Kaplan-Meier method and Cox regression analysis. Results MR histogram and texture parameters increased rapidly 30-60 seconds after contrast material administration. Standard deviation and entropy then plateaued, whereas skewness and kurtosis rapidly decreased. Univariate Cox regression analysis revealed that standard deviation and entropy were significant predictors of survival; their statistical significance was preserved from 60 to 300 seconds, with the smallest P values (P ≤ .001) occurring from 120 to 180 seconds. At multivariate Cox regression analysis, entropy was the sole significant predictor of 2-year PFS (hazard ratio at 180 seconds, 10.098 [95% confidence interval: 1.579, 64.577], P = .015; hazard ratio at 120 seconds: 11.202 [95% confidence interval: 1.761, 71.260], P = .010). Conclusion Histogram and texture parameter changes varied after contrast material injection. The 120-180-second window after contrast material injection was optimal for MR imaging-derived texture parameter and entropy at DCE MR imaging. (©) RSNA, 2016 Online supplemental material is available for this article.

Computer-Aided Diagnosis Scheme for Distinguishing Between Benign and Malignant Masses in Breast DCE-MRI.

Our purpose in this study was to develop a computer-aided diagnosis (CAD) scheme for distinguishing between benign and malignant breast masses in dynamic contrast material-enhanced magnetic resonance imaging (DCE-MRI). Our database consisted 90 DCE-MRI examinations, each of which contained four sequential phase images; this database included 28 benign masses and 62 malignant masses. In our CAD scheme, we first determined 11 objective features of masses by taking into account the image features and the dynamic changes in signal intensity that experienced radiologists commonly use for describing masses in DCE-MRI. Quadratic discriminant analysis (QDA) was employed to distinguish between benign and malignant masses. As the input of the QDA, a combination of four objective features was determined among the 11 objective features according to a stepwise method. These objective features were as follows: (i) the change in signal intensity from 2 to 5min; (ii) the change in signal intensity from 0 to 2min; (iii) the irregularity of the shape; and (iv) the smoothness of the margin. Using this approach, the classification accuracy, sensitivity, and specificity were shown to be 85.6% (77 of 90), 87.1% (54 of 62), and 82.1% (23 of 28), respectively. Furthermore, the positive and negative predictive values were 91.5% (54 of 59) and 74.2% (23 of 31), respectively. Our CAD scheme therefore exhibits high classification accuracy and is useful in the differential diagnosis of masses in DCE-MRI images.

Effect of Radiofrequency Transmit Field Correction on Quantitative Dynamic Contrast-enhanced MR Imaging of the Breast at 3.0 T.

To investigate the effects of radiofrequency transmit field (B1(+)) correction on (a) the measured T1 relaxation times of normal breast tissue and malignant lesions and (b) the pharmacokinetically derived parameters of malignant breast lesions at 3 T. Ethics approval and informed consent were obtained. Between May 2013 and January 2014, 30 women (median age, 58 years; range, 32-83 years) with invasive ductal carcinoma of at least 10 mm were recruited to undergo dynamic contrast material-enhanced magnetic resonance (MR) imaging before surgery. B1(+) and T1 mapping sequences were performed to determine the effect of B1(+) correction on the native tissue relaxation time (T10) of fat, parenchyma, and malignant lesions in both breasts. Pharmacokinetic parameters were calculated before and after correction for B1(+) variations. Results were correlated with histologic grade by using the Kruskal-Wallis test. Measurements showed a mean 37% flip angle difference between the right and left breast, which resulted in a 61% T10 difference in fat and a 41.5% difference in parenchyma between the two breasts. The T1 of lesions in the right breast increased by 58%, whereas that of lesions in the left breast decreased by 30% after B1(+) correction. The whole-tumor transendothelial permeability across the vascular compartment(K(trans)) of lesions in the right breast decreased by 41%, and that of lesions in the left breast increased by 46% after correction. A systematic increase in K(trans) was observed, with significant differences found across the histologic grades (P < .001). The effect size of B1(+) correction on K(trans) calculation was large for lesions in the right breast and moderate for lesions in the left breast (Cohen effect size, d = 0.86 and d = 0.59, respectively). B1(+) correction demonstrates a substantial effect on the results of quantitative dynamic contrast-enhanced analysis of breast tissue at 3 T, which propagates into the pharmacokinetic analysis of tumors that is dependent on whether the tumor is located in the right or left breast.

T1-weighted Dynamic Contrast-enhanced MR Imaging of the Lung in Asthma: Semiquantitative Analysis for the Assessment of Contrast Agent Kinetic Characteristics

To evaluate the contrast agent kinetics of dynamic contrast material-enhanced (DCE) magnetic resonance (MR) imaging in healthy lungs and asthmatic lungs by using non-model-based semiquantitative parameters and to explore the relationships with pulmonary function testing and eosinophil level. The study was approved by the National Research Ethical Committee (reference no. 11/NW/0387), and written informed consent was obtained from all individuals. Ten healthy subjects and 30 patients with asthma underwent pulmonary function tests, blood and sputum eosinophil counts, and 1.5-T DCE MR imaging within 7 days. Semiquantitative parameters of contrast agent kinetics were calculated from the relative signal intensity-time course curves on a pixel-by-pixel basis and were summarized by using whole-lung median values. The distribution heterogeneity was assessed by using the regional coefficient of variation. DCE MR imaging readouts were compared between groups by using one-way analysis of variance, and the relationships with pulmonary function testing and eosinophil counts were assessed by using Pearson correlation analysis. Asthmatic patients showed significantly lower peak enhancement (P < .001) and initial areas under the relative signal intensity curve in the first 60 seconds (P = .002) and significantly reduced late-phase washout slope (P = .002) when compared with healthy control subjects. The distribution heterogeneity of bolus arrival time (P = .029), time to peak (P = .008), upslope of the first-pass peak (P = .011), and late-phase washout slope (P = .032), estimated by using the median coefficient of variation, were significantly higher in asthmatic patients than in healthy control subjects. These imaging readouts also showed significant linear correlations with measurements of pulmonary function testing but not with eosinophil level in patients with asthma. The contrast agent kinetic characteristics of T1-weighted DCE MR images of asthmatic lungs are different from those of healthy lungs and are related to measurements of pulmonary function testing but not to eosinophil level.

Improving the Accuracy of Computer-aided Diagnosis for Breast MR Imaging by Differentiating between Mass and Nonmass Lesions.

To determine suitable features and optimal classifier design for a computer-aided diagnosis (CAD) system to differentiate among mass and nonmass enhancements during dynamic contrast material-enhanced magnetic resonance (MR) imaging of the breast. Two hundred eighty histologically proved mass lesions and 129 histologically proved nonmass lesions from MR imaging studies were retrospectively collected. The institutional research ethics board approved this study and waived informed consent. Breast Imaging Reporting and Data System classification of mass and nonmass enhancement was obtained from radiologic reports. Image data from dynamic contrast-enhanced MR imaging were extracted and analyzed by using feature selection techniques and binary, multiclass, and cascade classifiers. Performance was assessed by measuring the area under the receiver operating characteristics curve (AUC), sensitivity, and specificity. Bootstrap cross validation was used to predict the best classifier for the classification task of mass and nonmass benign and malignant breast lesions. A total of 176 features were extracted. Feature relevance ranking indicated unequal importance of kinetic, texture, and morphologic features for mass and nonmass lesions. The best classifier performance was a two-stage cascade classifier (mass vs nonmass followed by malignant vs benign classification) (AUC, 0.91; 95% confidence interval (CI): 0.88, 0.94) compared with one-shot classifier (ie, all benign vs malignant classification) (AUC, 0.89; 95% CI: 0.85, 0.92). The AUC was 2% higher for cascade (median percent difference obtained by using paired bootstrapped samples) and was significant (P = .0027). Our proposed two-stage cascade classifier decreases the overall misclassification rate by 12%, with 72 of 409 missed diagnoses with cascade versus 82 of 409 missed diagnoses with one-shot classifier. Separately optimizing feature selection and training classifiers for mass and nonmass lesions improves the accuracy of CAD for breast MR imaging. By cascading classifiers, we achieved a significant improvement in performance with respect to the use of a one-shot classifier. Our cascaded classifier may provide an advantage for screening women at high risk for breast cancer, in whom the ability to diagnose cancers at an early stage is of primary importance.

MR Enterography for the Evaluation of Small-Bowel Inflammation in Crohn Disease by Using Diffusion-weighted Imaging without Intravenous Contrast Material: A Prospective Noninferiority Study.

To determine whether magnetic resonance (MR) enterography performed with diffusion-weighted imaging (DWI) without intravenous contrast material is noninferior to contrast material-enhanced (CE) MR enterography for the evaluation of small-bowel inflammation in Crohn disease. Institutional review board approval and informed consent were obtained for this prospective noninferiority study. Fifty consecutive adults suspected of having Crohn disease underwent clinical assessment, MR enterography, and ileocolonoscopy within 1 week. MR enterography included conventional imaging and DWI (b = 900 sec/mm(2)). In 44 patients with Crohn disease, 171 small-bowel segments that were generally well distended and showed a wide range of findings, from normalcy to severe inflammation (34 men, 10 women; mean age ± standard deviation, 26.9 years ± 6.1), were selected for analysis. Image sets consisting of (a) T2-weighted sequences with DWI and (b) T2-weighted sequences with CE T1-weighted sequences were reviewed by using a crossover design with blinding and randomization. Statistical analyses included noninferiority testing regarding proportional agreement between DWI and CE MR enterography for the identification of bowel inflammation with a noninferiority margin of 80%, correlation between DWI and CE MR enterography scores of bowel inflammation severity, and comparison of accuracy between DWI and CE MR enterography for the diagnosis of terminal ileal inflammation by using endoscopic findings as the reference standard. The agreement between DWI and CE MR enterography for the identification of bowel inflammation was 91.8% (157 of 171 segments; one-sided 95% confidence interval: ≥88.4%). The correlation coefficient between DWI and CE MR enterography scores was 0.937 (P < .001). DWI and CE MR enterography did not differ significantly regarding the sensitivity and specificity for the diagnosis of terminal ileal inflammation (P > .999). DWI and CE MR enterography concurred in the diagnosis of penetrating complications in five of eight segments. DWI MR enterography was noninferior to CE MR enterography for the evaluation of inflammation in Crohn disease in generally well-distended small bowel, except for the diagnosis of penetration.

The Diagnostic Performance of Dynamic Contrast-enhanced MR Imaging for Detection of Small Hepatocellular Carcinoma Measuring Up to 2 cm: A Meta-Analysis.

To determine the performance of dynamic contrast material-enhanced magnetic resonance (MR) imaging in the diagnosis of small (≤2-cm) hepatocellular carcinoma (HCC) and to identify factors that influence this performance. Medline and Embase databases were searched for studies performed from January 2000 to March 2014 in which the performance of MR imaging was reported for the detection of HCC up to 2 cm on either a lesion- or patient-based level, with sufficient data to construct 2 × 2 contingency tables. Diagnostic performance was quantitatively pooled for all studies by using a bivariate random-effects model with exploration involving subgroup analysis, meta-regression, and determination of study heterogeneity. Twenty-two studies with 1387 small HCC lesions in 1908 patients met inclusion criteria. Heterogeneity was higher for sensitivity (range, 30%-99%) than specificity (range, 61%-100%). Overall sensitivity was 78% (95% confidence interval [CI]: 68%, 85%; I(2) = 89%), and overall specificity was 92% (95% CI: 88%, 95%; I(2) = 69%). The primary potential source of bias was use of explant as the reference standard in only 13% of studies, although lower sensitivity in such studies was not significant (59% vs 80%, P = .165). Sensitivities were significantly higher for studies that originated from Asia compared with those that originated elsewhere (89% vs 71%, P = .028), those performed with hepatobiliary phase imaging compared with those without (87% vs 65%, respectively; P = .004), and those in which gadoxetate disodium was used versus an extracellular agent (92% vs 67%, P ≤ .001). Specificity was not significantly different between subgroups (P ≥ .122). At pairwise meta-regression analysis with either study origin from Asia or performance of hepatobiliary phase imaging, only gadoxetate disodium contrast agent showed significant independent association with higher sensitivity (P = .002-.007). Results of this meta-analysis suggest that dynamic contrast-enhanced MR imaging has moderate sensitivity and excellent specificity in the detection of HCC up to 2 cm. Gadoxetate disodium contrast agent showed the strongest association with increased sensitivity.

Association between Parenchymal Enhancement of the Contralateral Breast in Dynamic Contrast-enhanced MR Imaging and Outcome of Patients with Unilateral Invasive Breast Cancer.

To retrospectively investigate whether parenchymal enhancement in dynamic contrast material-enhanced magnetic resonance (MR) imaging of the contralateral breast in patients with unilateral invasive breast cancer is associated with therapy outcome. After obtaining approval of the institutional review board and patients' written informed consent, 531 women with unilateral invasive breast cancer underwent dynamic contrast-enhanced MR imaging between 2000 and 2008. The contralateral parenchyma was segmented automatically, in which the mean of the top 10% late enhancement was calculated. Cox regression was used to test associations between parenchymal enhancement, patient and tumor characteristics, and overall survival and invasive disease-free survival. Subset analyses were performed and stratified according to immunohistochemical subtypes and type of adjuvant treatment received. Median follow-up was 86 months. Age (P < .001) and immunohistochemical subtype (P = .042) retained significance in multivariate analysis for overall survival. In patients with estrogen receptor-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer (n = 398), age (P < .001), largest diameter on MR images (P = .049), and parenchymal enhancement (P = .011) were significant. In patients who underwent endocrine therapy (n = 174), parenchymal enhancement was the only significant covariate for overall survival and invasive disease-free survival (P < .001). Results suggest that parenchymal enhancement in the contralateral breast of patients with invasive unilateral breast cancer is significantly associated with long-term outcome, particularly in patients with estrogen receptor-positive, human epidermal growth factor receptor 2-negative breast cancer. Lower value of the mean top 10% enhancement of the parenchyma shows potential as a predictive biomarker for relatively poor outcome in patients who undergo endocrine therapy. These results should, however, be validated in a larger study.

Identifying Staging Markers for Hepatocellular Carcinoma before Transarterial Chemoembolization: Comparison of Three-dimensional Quantitative versus Non–three-dimensional Imaging Markers

Purpose To test and compare the association between radiologic measurements of lesion diameter, volume, and enhancement on baseline magnetic resonance (MR) images with overall survival and tumor response in patients with unresectable hepatocellular carcinoma (HCC) treated with transarterial chemoembolization (TACE). Materials and Methods This HIPAA-compliant retrospective, single-institution analysis was approved by the institutional review board, with waiver of informed consent. It included 79 patients with unresectable HCC who were treated with TACE. Baseline arterial phase contrast material-enhanced (CE) MR imaging was used to measure the overall and enhancing tumor diameters. A segmentation-based three-dimensional quantification of the overall and enhancing tumor volumes was performed in each patient. Numeric cutoff values (5 cm for diameters and 65 cm(3) for volumes) were used to stratify the patient cohort in two groups. Tumor response rates according to Response Evaluation Criteria in Solid Tumors (RECIST), modified RECIST (mRECIST), and European Association for the Study of the Liver (EASL) guidelines were recorded for all groups. Survival was evaluated by using Kaplan-Meier analysis and was compared by using Cox proportional hazard ratios (HRs) after univariate and multivariate analysis. Results Stratification according to overall and enhancing tumor diameters did not result in a significant separation of survival curves (HR, 1.4; 95% confidence interval [CI]: 0.7, 2.5; P = .234; and HR, 1.6; 95% CI: 0.9, 2.8; P = .08, respectively). The stratification according to overall and enhancing tumor volume achieved significance (HR, 1.8; 95% CI: 0.9, 3.4; P = .022; and HR, 1.8; 95% CI: 1.1, 3.1; P = .017, respectively). As for tumor response, higher response rates were observed in smaller lesions compared with larger lesions, when the 5-cm threshold (27% vs 15% for mRECIST and 45% vs 24% for EASL) was used. Conclusion As opposed to anatomic tumor diameter as the most commonly used staging marker, volumetric assessment of lesion size and enhancement on baseline CE MR images is strongly associated with survival of patients with HCC who were treated with TACE.