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Purpose: Gadolinium (Gd)-based contrast agents are primarily used for contrast-enhanced magnetic resonance lymphangiography (MRL). However, overcoming venous contamination issues remains challenging. This study aims to assess the MRL efficacy of the newly developed iron-based contrast agent (INV-001) that is specially designed to mitigate venous contamination issues. The study further explores the optimal dosage, including both injection volume and concentration, required to achieve successful visualization of the popliteal lymph nodes and surrounding lymphatic vessels., Procedures: All animals utilized in this study were male Sprague-Dawley (SD) rats weighing between 250 and 300 g. The contrast agents prepared were injected intradermally in the fourth phalanx of both hind limbs using a 30-gauge syringe in SD rats. MRL was performed every 16 min on a coronal 3D time-of-flight sequence with saturation bands using a 9.4-T animal machine., Results: Contrary to Gd-DOTA, which exhibited venous contamination in most animals irrespective of injection dosages and conditions, INV-001 showed no venous contamination. For Gd-DOTA, the popliteal lymph nodes and lymphatic vessels reached peak enhancement 16 min after injection from the injection site and then rapidly washed out. However, with INV-001, they reached peak enhancement between 16 and 32 min after injection, with prolonged visualization of the popliteal lymph node and lymphatic vessels. INV-001 at 0.45 μmol (15 mM, 30 μL) and 0.75 μmol (15 mM, 50 μL) achieved high scores for qualitative image analysis, providing good visualization of the popliteal lymph nodes and lymphatic vessels without issues of venous contamination, interstitial space enhancement, or lymph node enlargement., Conclusion: In MRL, INV-001, a novel T 1 contrast agent based on iron, enables prolonged enhancement of popliteal lymph nodes and lymphatic vessels without venous contamination., (© 2024. The Author(s), under exclusive licence to World Molecular Imaging Society.)

We aimed to conduct a proof-of-concept study of INV-001 in visualizing lymphatic vessels and nodes without venous contamination and to determine the optimal dose condition of INV-001 for magnetic resonance lymphangiography (MRL) in healthy beagles. MRL was performed using a 3.0-Tesla (T) whole body clinical magnetic resonance imaging (MRI) scanner. A dose-finding study of INV-001 for MRL in beagles (N = 6) was carried out according to an adaptive optimal dose finding design. For the reproducibility study (N = 6), MRL was conducted at selected INV-001 doses (0.056 and 0.112 mg Fe/kg) with a 15 mM concentration. Additionally, an excretion study (N = 3) of INV-001 was conducted by analyzing T 1 , T 2 , and T 2 * maps of the liver and kidney 48 h post-administration. INV-001 administration at doses of 0.056 and 0.112 mg Fe/kg (concentration: 15 mM) consistently demonstrated the visualization of contrast-enhanced lymphatic vessels and nodes without venous contamination in the beagles. The contrast enhancement effect was highest at 30 min after INV-001 administration, then gradually decreasing. No toxicity-related issues were identified during the study. After 48 h, the T 1 , T 2 , and T 2 * values in the liver and both kidneys were found to be comparable to the pre-administration values, indicating thorough INV-001 excretion. The optimal dosing conditions of INV-001 for MRL for contrast-enhanced visualization of lymphatic vessels and nodes exclusively with no venous contamination in beagles was determined to be 0.056 mg Fe/kg with a 15 mM concentration., (© 2024. The Author(s).)

Purpose: To evaluate the effects of a reference image and keyhole factor (K f ) selections for high-frequency substitution on keyhole imaging technique for applications in glutamate chemical exchange saturation transfer (GluCEST) imaging., Procedures: The CEST data were obtained using a 7.0 T MRI scanner. We used varied K f ranges that constituted from 16.67 to 75 % of the full k-space. The reference image was respectively selected for - 3 and + 3 ppm images that associated with the GluCEST calculation and the unsaturated image. The zero-padding algorithm was applied for the missing k-space lines in the low-frequency data collected to compare the results obtained from using the keyhole imaging technique. All the techniques were evaluated using a healthy rat group and extended to the status epilepticus rat group to explore their applicability and usability., Results: The calculated GluCEST signals and visually inspected results from the reconstructed GluCEST maps indicated that the combination of unsaturated image as a reference image, and over 50 % of K f showed consistent signals and image quality compared with the fully sampled CEST data., Conclusions: Combining the keyhole imaging technique with GluCEST imaging enables stable image reconstruction and quantitative evaluation, and this approach is potentially applicable in various CEST imaging applications.

Background: Hemorrhagic transformation increases mortality and morbidity in patients with acute ischemic stroke., Purpose: The purpose of this study is to evaluate the diagnostic performance of magnetic resonance imaging (MRI) for prediction of hemorrhagic transformation in acute ischemic stroke., Material and Methods: A systematic literature search of MEDLINE and EMBASE was performed up to 27 July 2018, including the search terms "acute ischemic stroke," "hemorrhagic transformation," and "MRI." Studies evaluating the diagnostic performance of MRI for prediction of hemorrhagic transformation in acute ischemic stroke were included. Diagnostic meta-analysis was conducted with a bivariate random-effects model to calculate the pooled sensitivity and specificity. Subgroup analysis was performed including studies using advanced MRI techniques including perfusion-weighted imaging, diffusion-weighted imaging, and susceptibility-weighted imaging., Results: Nine original articles with 665 patients were included. Hemorrhagic transformation is associated with high permeability, hypoperfusion, low apparent diffusion coefficient (ADC), and FLAIR hyperintensity. The pooled sensitivity was 82% (95% confidence interval [CI] 61-93) and the pooled specificity was 79% (95% CI 71-85). The area under the hierarchical summary receiver operating characteristic curve was 0.85 (95% CI 0.82-0.88). Although study heterogeneity was present in both sensitivity (I 2 =67.96%) and specificity (I 2 =78.93%), a threshold effect was confirmed. Studies using advanced MRI showed sensitivity of 92% (95% CI 70-98) and specificity of 78% (95% CI 65-87) to conventional MRI., Conclusion: MRI may show moderate diagnostic performance for predicting hemorrhage in acute ischemic stroke although the clinical significance of this hemorrhage is somewhat uncertain.

Objectives: To determine the diagnostic accuracy of magnetic resonance tumor regression grade (mrTRG) for pathological complete response (pCR) and its correlation with pathological findings., Methods: Original studies that investigated the correlation of mrTRG with pathological tumor regression grade and pathological T stage were identified in MEDLINE and EMBASE up until August 31, 2018, according to PRISMA guidelines. The search terms included colorectal cancer, chemoradiation therapy, magnetic resonance imaging, and response or regression. Meta-analytic summary sensitivity and specificity for pathologic complete response (pCR) and pathologic T1 or lower than T1 stage (≤ypT1) were calculated using a bivariate random-effects model. The sensitivity and specificity were calculated in both mrTRG 1 and mrTRG 1 or 2, respectively., Results: Six studies with 916 patients were included. The meta-analytic summary sensitivity and specificity of mrTRG 1 for pCR were 32.3% (95% CI, 18.2-50.6%) and 93.5% (95% CI, 91.5-95.1%), while for ≤ypT1 they were 31.8% (95% CI, 16.2-53.0%) and 94.7% (95% CI, 91.9-96.5%). On the contrary, sensitivity and specificity of mrTRG 1 or 2 for pCR were 69.9% (95% CI, 60.2-78.1%) and 62.2% (95% CI, 56.2-67.8%), while those for ≤ypT1 were 71.4% (95% CI, 61.6-79.6%) and 67.7% (95% CI, 59.8-74.7%)., Conclusions: mrTRG 1 showed high specificity for pCR and ≤ypT1, but suboptimal sensitivity. mrTRG 1 or 2 showed higher sensitivity for pCR and ≤ypT1, but lower specificity. Because of the suboptimal sensitivity of mrTRG 1, it might be limited as a criterion for less aggressive treatment after neoadjuvant chemoradiotherapy., Key Points: • Magnetic resonance tumor regression grade 1 shows high specificity for pCR and ≤ypT1, but suboptimal sensitivity. • Magnetic resonance tumor regression grade 1 or 2 shows higher sensitivity for pCR and ≤ypT1, but lower specificity than magnetic resonance tumor regression grade 1 alone.

Purpose: To evaluate the feasibility of motion correction in glutamate chemical exchange saturation transfer (GluCEST) imaging, using a rat model of epileptic seizure., Procedures: Epileptic seizure was induced in six male Wistar rats by intraperitoneal injection of kainic acid (KA). CEST data were obtained using a 7.0 T Bruker MRI scanner before and 3 h after KA injection. Retrospective motion correction was performed in CEST images using a gradient-based motion correction (GradMC) algorithm. GluCEST signals in the hippocampal regions were quantitatively evaluated with and without motion correction., Results: Calculated GluCEST signals differed significantly between the pre-KA injection group, regardless of motion-correction implementation, and the post-KA injection group with motion correction (3.662 ± 1.393 % / 3.726 ± 1.982 % for pre-KA injection group with/without motion correction vs. 6.996 ± 1.684 % for post-KA injection group with motion correction; all P < 0.05)., Conclusions: Our results clearly show that GradMC can be used in CEST imaging for efficient correction of seizure-like motion. The GradMC can be further implemented in various CEST imaging techniques to increase the accuracy of analysis.

Background: Glutamate chemical exchange saturation transfer (GluCEST) imaging has been widely used in brain psychiatric disorders. Glutamate signal changes may help to evaluate the sleep-related disorders, and could be useful in diagnosis., Purpose: To evaluate signal changes in the hippocampus and cortex of a rat model of stress-induced sleep disturbance using GluCEST., Study Type: Prospective animal study., Animal Model: Fourteen male Sprague-Dawley rats., Field Strength/sequence: 7.0T small bore MRI / fat-suppressed, turbo-rapid acquisition with relaxation enhancement (RARE) for CEST, and spin-echo, point-resolved proton MR spectroscopy ( 1 H MRS)., Assessment: Rats were divided into two groups: the stress-induced sleep-disturbance group (SSD, n = 7) and the control group (CTRL, n = 7), to evaluate and compare the cerebral glutamate signal changes. GluCEST data were quantified using a conventional magnetization transfer ratio asymmetry in the left- and right-side hippocampus and cortex. The correlation between GluCEST signal and glutamate concentrations, derived from 1 H MRS, was evaluated., Statistical Analysis: Wilcoxon rank-sum test between CEST signals and multiparametric MR signals, Wilcoxon signed-rank test between CEST signals on the left and right hemispheres, and a correlation test between CEST signals and glutamate concentrations derived from 1 H MRS., Results: Measured GluCEST signals showed significant differences between the two groups (left hippocampus; 4.23 ± 0.27% / 5.27 ± 0.42% [SSD / CTRL, P = 0.002], right hippocampus; 4.50 ± 0.44% / 5.04 ± 0.34% [P = 0.035], left cortex; 2.81 ± 0.38% / 3.56 ± 0.41% [P = 0.004], and right cortex; 2.95 ± 0.47% / 3.82 ± 0.26% [P = 0.003]). GluCEST signals showed positive correlation with glutamate concentrations (R 2 = 0.312; P = 0.038)., Data Conclusion: GluCEST allowed the visualization of cerebral glutamate changes in rats subjected to sleep disturbance, and may yield valuable insights for interpreting alterations in cerebral biochemical information., Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1866-1872., (© 2019 International Society for Magnetic Resonance in Medicine.)

Objectives: To systematically determine the diagnostic accuracy of 18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging ([ 18 F]FDG-PET/MRI) for the detection of liver metastases and evaluate the sources of heterogeneity in the reported results., Methods: PubMed and EMBASE databases were searched up until December 31, 2017, to identify original research studies reporting the diagnostic performance (Se and Sp) of PET/MRI for liver metastases, in comparison with PET/CT. Study quality was assessed using QUADAS-2. The summary Se and Sp of the studies were estimated using hierarchical modeling methods. To determine causes of study heterogeneity, the presence of a threshold effect was analyzed, and meta-regression analysis was performed., Results: Of 546 articles screened, eight suitable articles were identified, with seven for per-lesion analysis, and four for per-patient analysis. The meta-analytic summary Se and Sp for per-patient-based analysis were 99.2% (95% CI, 31.4-100.0%, I 2  = 89.4%) and 98.6% (95% CI, 84.0-99.9%, I 2  = 0.0%), respectively, while for per-lesion-based analysis they were 95.4% (95% CI, 78.3-99.2%, I 2  = 99.7%) and 99.3% (95% CI, 93.8-99.9%, I 2  = 96.5%). PET/MRI showed higher Se (95.4% vs. 68.3%) and Sp (99.3% vs. 95.8%) than PET/CT. Meta-regression analysis showed five significant factors affecting study heterogeneity: study subject characteristics, study design, MRI technique (DWI, HBP after injection of liver-specific contrast media), imaging review method, and reference standard., Conclusion: The diagnostic accuracy of [ 18 F]FDG-PET/MRI for liver metastasis was high overall, but substantial heterogeneity was found. Further randomized controlled studies or prospective studies are needed to investigate the role of PET/MRI in liver metastasis in comparison with PET/CT., Key Points: • [ 18 F]FDG-PET/MRI has high meta-analytic Se and Sp for the diagnosis of liver metastasis. • PET/MRI using DWI and HBP images significantly increased diagnostic accuracy. • Study heterogeneity was associated with subject characteristics, study design, MRI technique, image review method, and reference standard.

Objective: To evaluate predictive values of sarcopenia and visceral obesity measured from preoperative CT/MRIs for postoperative pancreatic fistula (POPF) after pancreaticoduodenectomy in patients with periampullary malignancies., Methods: From the prospectively constructed surgical registry, we included adult patients treated with pancreaticoduodenectomy. Based on CT/MRIs, body morphometric analysis was performed to evaluate the visceral obesity and sarcopenia, based on the areas of visceral fat and skeletal muscle measured at the L3 vertebrae level. We retrieved various perioperative factors from registry. As outcomes of postoperative complications, we evaluated POPF and major complications based on the Clavien-Dindo classification. Multivariate logistic regression analyses were performed., Results: From a total of 284 patients (163 males, 121 females) who met the inclusion/exclusion criteria, POPF, major complications, and 60-day mortality occurred in 52 (18.3%), 34 (12.0%), and 6 (2.1%), respectively. Sarcopenia and visceral obesity were noted in 123 (75.5%) and 66 (40.5%) of men and 68 (56.2%) and 53 (43.8%) of women, respectively. Combination of sarcopenia and obesity (sarcopenic obesity) was noted in 31.9% (52/163) of men and in 26.4% (32/121) of women. In multivariate logistic regression analyses, sarcopenic obesity was the only independent predictor for POPF (OR 2.65, 95% CI 1.43-4.93), and the vascular resection during pancreaticoduodenectomy was the only independent predictor for severe complications (OR 3.75, 95% CI 1.61-8.70)., Conclusion: Sarcopenic obesity might be highly predictive for POPF. Body morphometric analysis in preoperative CT/MRI combined with assessment of perioperative clinical features may help to identify high-risk patients and determine perioperative management strategies., Key Points: • Sarcopenic obesity might be predictive for postoperative pancreatic fistula after pancreaticoduodenectomy. • The vascular resection during pancreaticoduodenectomy might be predictive of major complications. • Body morphometric analysis might be helpful for identifying high-risk patients.

Background: Imaging studies, including computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET), have an essential role in the detection and localization of colorectal liver metastasis (CRLM)., Purpose: To systematically determine the diagnostic accuracy of multidetector row CT (MDCT), gadoxetate disodium-enhanced MRI, and PET/CT for diagnosing CRLM and the sources of heterogeneity between the reported results., Study Type: Systematic review and meta-analysis., Subjects: In all, 2151 lesions in CT studies, 2301 lesions in MRI studies, 1846 lesions in PET/CT studies, FIELD STRENGTH: 1.5T and 3.0T., Assessment: We identified research studies that investigated MDCT, gadoxetate disodium-enhanced MRI, and PET/CT to diagnose CRLM by performing a systematic search of PubMed MEDLINE and EMBASE. Study quality was assessed using Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2)., Statistical Tests: According to the types of imaging tests, study heterogeneity and the threshold effect were analyzed and the meta-analytic summary of sensitivity and specificity were estimated. Meta-regression analysis was performed to further investigate study heterogeneity., Results: Of the 860 articles screened, we found 36 studies from 24 articles reporting a diagnosis of CRLM (11 CT studies, 12 MRI studies, and 13 PET/CT studies). The meta-analytic summary sensitivity for CT, MRI, and PET/CT were 82.1% (95% confidence interval [CI], 74.0-88.1%), 93.1% (95% CI, 88.4-96.0%), and 74.1% (95% CI, 62.1-83.3%), respectively. The meta-analytic summary specificity for CT, MRI, and PET/CT were 73.5% (95% CI, 53.7-86.9%), 87.3% (95% CI, 77.5-93.2%), and 93.9% (95% CI, 83.9-97.8%), respectively. There was no threshold effect in any of the imaging tests. Neoadjuvant chemotherapy significantly decreased the sensitivity of CT and MRI (P < 0.01), although it did not significantly affect the sensitivity of PET/CT. The study design, type of reference standard, and study quality also affected the diagnostic performances of imaging studies., Data Conclusion: Despite the heterogeneous accuracy between studies, gadoxetate disodium-enhanced MRI showed the highest sensitivity, and gadoxetate disodium-enhanced MRI and PET/CT had similar specificities for diagnosing CRLM., Level of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1237-1250., (© 2017 International Society for Magnetic Resonance in Medicine.)

Objective: We determined the cost-effectiveness of two different diagnostic imaging strategies in guiding curative treatment of early-stage hepatocellular carcinoma (HCC)., Materials and Methods: We developed a decision analytic model using as its starting point a cohort of patients aged 55 years with early-stage HCC detected at dynamic multiphasic CT and with Child-Pugh class A cirrhosis. The model compared two strategies on the initial workup: conventional CT strategy using dynamic multiphasic CT only and gadoxetic acid-enhanced MRI strategy using additional gadoxetic acid-enhanced MRI after initial CT. A Markov cohort model simulated a cohort of patients after curative or adjuvant treatment, with follow-up over the remaining life expectancy. We analyzed mean life-years gain, quality-adjusted life-years (QALYs), costs per person, and incremental cost-effectiveness ratio (ICER). To evaluate results, we performed one-way, two-way, and probabilistic sensitivity analyses., Results: The life expectancies and QALY were 7.22 years and 5.08 for the conventional CT strategy and 7.79 years and 5.52 for the gadoxetic acid-enhanced MRI strategy, respectively. The expected costs were $99,770 for conventional CT and $105,025 for gadoxetic acid-enhanced MRI in the United States. The ICER with gadoxetic acid-enhanced MRI was $11,957, as opposed to that with conventional CT, which was lower than the cost-effectiveness threshold of $50,000/QALY. One-way, two-way, and probabilistic sensitivity analyses showed unchanged results over an acceptable range., Conclusion: Gadoxetic acid-enhanced MRI after CT is cost-effective for detecting additional HCC in patients with early-stage HCC who can undergo curative treatment (besides liver transplantation). The cost-effectiveness of gadoxetic acid-enhanced MRI may be considered in the management of patients with early-stage HCC during staging.

Objectives: We evaluated the cost-effectiveness of a gadoxetic acid-enhanced MRI (EOB-MRI) strategy compared with conventional MRI strategy and biopsy to differentiate focal nodular hyperplasia (FNH) from hepatocellular adenoma (HCA)., Methods: A decision tree model was constructed to compare the cost-effectiveness of EOB-MRI, conventional MRI with extracellular contrast agents, and biopsy as the initial diagnostic modality in patients with incidentally detected focal liver lesions suspected of being FNH or HCA. We analysed the cost and effectiveness, i.e. probability of successful diagnosis of each strategy. Costs were based on utilisation rates and Medicare reimbursements in the USA and South Korea., Results: In the base case analysis of our decision tree model, the effectiveness of the three strategies was similar. The cost of the EOB-MRI strategy ($1283 in USA, $813 in South Korea) was lowest compared with the biopsy strategy ($1725 in USA, $847 in South Korea) and the conventional MRI strategy ($1750 in USA, $962 in South Korea). One-way, two-way and probabilistic sensitivity analysis showed unchanged results over an acceptable range., Conclusions: EOB-MRI strategy is the most cost-effective strategy for differentiating FNH from HCA in patients with incidentally detected focal liver lesions in a non-cirrhotic liver., Key Points: • The effectiveness of the three strategies was similar. • The cost of the EOB-MRI strategy was lowest. • EOB-MRI strategy is the most cost-effective for differentiating FNH from HCA.

Objective: The purpose of this study is to evaluate the outcomes of hypovascular hypointense nodules in the hepatobiliary phase of gadoxetic acid-enhanced MRI and the risk factors for the hypervascular transformation of the nodules through a systematic review and meta-analysis., Materials and Methods: We searched the Ovid-MEDLINE and EMBASE databases for published studies of hypovascular hypointense nodules in patients with chronic liver disease. The pooled proportions of the overall and cumulative incidence rates at 1, 2, and 3 years for the transformation of hypovascular hypointense nodules into hypervascular hepatocellular carcinomas (HCCs) were assessed by using random-effects modeling. Metaregression analysis was performed., Results: Sixteen eligible studies with 944 patients and 1819 hypovascular hypointense nodules in total were included. The pooled overall rate of hypervascular transformation was 28.2% (95% CI, 22.7-33.6%; I 2 = 87.46%). The pooled 1-, 2-, and 3-year cumulative incidence rates were 18.3% (95% CI, 9.2-27.4%), 25.2% (95% CI, 12.2-38.2%), and 30.3% (95% CI, 18.8-41.9%), respectively. The metaregression analysis revealed that the mean initial nodule size (cutoff value, 9 mm) was a significant factor affecting the heterogeneity of malignant transformation., Conclusion: Hypovascular hypointense nodules detected in the hepatobiliary phase of gadoxetic acid-enhanced MRI carry a significant potential of transforming into hypervascular HCCs. The size of nodules is a significant risk factor for hypervascular transformation.

Objective: To simulate the B 1 -inhomogeneity-induced variation of pharmacokinetic parameters on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)., Materials and Methods: B 1 -inhomogeneity-induced flip angle (FA) variation was estimated in a phantom study. Monte Carlo simulation was performed to assess the FA-deviation-induced measurement error of the pre-contrast R 1 , contrast-enhancement ratio, Gd-concentration, and two-compartment pharmacokinetic parameters (K trans , v e , and v p )., Results: B 1 -inhomogeneity resulted in -23-5% fluctuations (95% confidence interval [CI] of % error) of FA. The 95% CIs of FA-dependent % errors in the gray matter and blood were as follows: -16.7-61.8% and -16.7-61.8% for the pre-contrast R 1 , -1.0-0.3% and -5.2-1.3% for the contrast-enhancement ratio, and -14.2-58.1% and -14.1-57.8% for the Gd-concentration, respectively. These resulted in -43.1-48.4% error for K trans , -32.3-48.6% error for the v e , and -43.2-48.6% error for v p . The pre-contrast R 1 was more vulnerable to FA error than the contrast-enhancement ratio, and was therefore a significant cause of the Gd-concentration error. For example, a -10% FA error led to a 23.6% deviation in the pre-contrast R 1 , -0.4% in the contrast-enhancement ratio, and 23.6% in the Gd-concentration. In a simulated condition with a 3% FA error in a target lesion and a -10% FA error in a feeding vessel, the % errors of the pharmacokinetic parameters were -23.7% for K trans , -23.7% for v e , and -23.7% for v p ., Conclusion: Even a small degree of B 1 -inhomogeneity can cause a significant error in the measurement of pharmacokinetic parameters on DCE-MRI, while the vulnerability of the pre-contrast R 1 calculations to FA deviations is a significant cause of the miscalculation.

Objective: To compare the breathing effects on dynamic contrast-enhanced (DCE)-MRI between controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA)-volumetric interpolated breath-hold examination (VIBE), radial VIBE with k-space-weighted image contrast view-sharing (radial-VIBE), and conventional VIBE (c-VIBE) sequences using a dedicated phantom experiment., Materials and Methods: We developed a moving platform to simulate breathing motion. We conducted dynamic scanning on a 3T machine (MAGNETOM Skyra, Siemens Healthcare) using CAIPIRINHA-VIBE, radial-VIBE, and c-VIBE for six minutes per sequence. We acquired MRI images of the phantom in both static and moving modes, and we also obtained motion-corrected images for the motion mode. We compared the signal stability and signal-to-noise ratio (SNR) of each sequence according to motion state and used the coefficients of variation (CoV) to determine the degree of signal stability., Results: With motion, CAIPIRINHA-VIBE showed the best image quality, and the motion correction aligned the images very well. The CoV (%) of CAIPIRINHA-VIBE in the moving mode (18.65) decreased significantly after the motion correction (2.56) ( p < 0.001). In contrast, c-VIBE showed severe breathing motion artifacts that did not improve after motion correction. For radial-VIBE, the position of the phantom in the images did not change during motion, but streak artifacts significantly degraded image quality, also after motion correction. In addition, SNR increased in both CAIPIRINHA-VIBE (from 3.37 to 9.41, p < 0.001) and radial-VIBE (from 4.3 to 4.96, p < 0.001) after motion correction., Conclusion: CAIPIRINHA-VIBE performed best for free-breathing DCE-MRI after motion correction, with excellent image quality.

Objectives: To evaluate the feasibility of test-bolus dynamic contrast-enhanced (DCE) MRI with CAIPIRINHA-VIBE for pancreatic malignancies., Methods: Thirty-two patients underwent DCE-MRI with CAIPIRINHA-VIBE after injection of 2 mL gadolinium. From the resulting time-intensity curve (TIC), we estimated the arterial (AP) and portal venous phase (PVP) scan timing for subsequent multiphasic MRI. DCE-MRI perfusion maps were generated, and perfusion parameters were calculated. The image quality was rated on a 5-point scale (1: poor, 5: excellent). Goodness-of-fit of the TIC was evaluated by Pearson's χ 2 test., Results: Test-bolus DCE-MRIs with high temporal (3 s) and spatial resolution (1 × 1 × 4 mm 3 ) were acquired with good-quality perfusion maps of Ktrans and iAUC (mean score 4.313 ± 0.535 and 4.125 ± 0.554, respectively). The mean χ 2 values for fitted TICs were 0.115 ± 0.082 for the pancreatic parenchyma and 0.784 ± 0.074 for pancreatic malignancies, indicating an acceptable goodness-of-fit. Test-bolus DCE-MRI was highly accurate in estimating the proper timing of AP (90.6 %) and PVP (100 %) of subsequent multiphasic MRI. Between pancreatic adenocarcinomas and neuroendocrine tumours, there were significant differences in the Ktrans (0.073 ± 0.058 vs. 0.308 ± 0.062, respectively; p = 0.007) and iAUC (1.501 ± 0.828 vs. 3.378 ± 0.378, respectively; p = 0.045)., Conclusions: Test-bolus DCE-MRI using CAIPIRINHA-VIBE is feasible for incorporating perfusion analysis of pancreatic tumours into routine multiphasic MRI., Key Points: • Test-bolus DCE-MRI using CAIPIRINHA-VIBE is feasible for perfusion analysis of pancreatic tumours. • CAIPIRINHA-VIBE enables DCE-MRI with high temporal and spatial resolution. • Test-bolus DCE-MRI is highly accurate in estimating the proper timing of multiphasic MRI.

This study aimed to compare the detectability of brain metastases using contrast-enhanced spin-echo (SE) and gradient-echo (GRE) T1-weighted images. The Ovid-MEDLINE and EMBASE databases were searched for studies on the detectability of brain metastases using contrast-enhanced SE or GRE images. The pooled proportions for the detectability of brain metastases were assessed using random-effects modeling. Heterogeneity among studies was determined using χ (2) statistics for the pooled estimates and the inconsistency index, I (2) . To overcome heterogeneity, subgroup analyses according to slice thickness and lesion size were performed. A total of eight eligible studies, which included a sample size of 252 patients and 1413 brain metastases, were included. The detectability of brain metastases using SE images (89.2 %) was higher than using GRE images (81.6 %; adjusted 84.0 %), but this difference was not statistically significant (p = 0.2385). In subgroup analysis of studies with 1-mm-thick slices and small metastases (<5 mm in diameter), 3-dimensional (3D) SE images demonstrated a higher detectability in comparison to 3D GRE images (93.7 % vs 73.1 % in 1-mm-thick slices; 89.5 % vs 59.4 % for small metastases) (p < 0.0001). Although both SE or GRE images are acceptable for detecting brain metastases, contrast-enhanced 3D SE images using 1-mm-thick slices are preferred for detecting brain metastases, especially small lesions (<5 mm in diameter).

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) is a promising tool for evaluating tumor vascularity, as it can provide vasculature-derived, functional, and quantitative parameters. To implement DCE-MRI parameters as biomarkers for monitoring the effect of antiangiogenic or vascular-disrupting treatment, two crucial elements of surrogate endpoint, ie, validation and qualification, should be satisfied. Although early studies have shown the accuracy and reliability of DCE-MRI parameters for evaluating treatment-driven vascular alterations, there have been an increasing number of studies demonstrating the limitations of DCE-MRI parameters as surrogate endpoints. Therefore, in order to improve the application of DCE-MRI parameters in drug development, it is necessary to establish a standardized evaluation method and to determine the correct therapeutics-oriented meaning of individual DCE-MRI parameter. In this regard, this article describes the biophysical background and data acquisition/analysis techniques of DCE-MRI while focusing on the validation and qualification issues. Specifically, the causes of disagreement and confusion encountered in the preclinical and clinical trials using DCE-MRI are presented in detail. Finally, considering these limitations, we present potential strategies to optimize implementation of DCE-MRI. J. Magn. Reson. Imaging 2016;44:251-264., (© 2016 Wiley Periodicals, Inc.)

This study aims to evaluate the value of perfusion MRI as a predictive/prognostic biomarker and a pharmacodynamic biomarker in patients with recurrent glioma treated with a bevacizumab-based regimen. We identified thirteen literature reports that investigated dynamic susceptibility-contrast (DSC) MRI or dynamic contrast-enhanced (DCE) MRI for predicting the patient outcome and analyzing the anti-angiogenic effect of bevacizumab by performing a systematic search of MEDLINE and EMBASE. The relative cerebral volume (rCBV) of DSC-MRI is currently the most common perfusion MRI parameter used as a predictive/prognostic biomarker. Pooled hazard ratios between responders and non-responders, as determined by rCBV, were 0.46 (95 % CI 0.28-0.76) for progression-free survival from five articles with a total 226 patients and 0.47 (95 % CI 0.29-0.76) for overall survival from six articles with a total 247 patients, and thus indicating that rCBV is helpful for predicting disease progression and the eventual outcome after treatment. Regarding the pharmacodynamic value of perfusion MRI parameters derived from either DSC-MRI or DCE-MRI, most perfusion MRI parameters (rCBV, Ktrans, CBVmax, Kpsmax, fpv, Ve and Kep) demonstrated a consistent decrease on the follow-up MRI after treatment, indicating that perfusion MRI may be helpful for evaluating the anti-angiogenic effect of a bevacizumab-based treatment regimen. However, the lack of standardization of imaging acquisition and analysis techniques for various perfusion MRI parameters needs to be resolved in the future. Despite these unsolved issues, the current evidence favoring the use of perfusion MRI as a predictive/prognostic or pharmacodynamic biomarker should be considered in patients with glioma treated using a bevacizumab-based regimen.

Objective: To validate radial acquisition of volumetric interpolated breath hold examination (Radial-VIBE) and the controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA-VIBE) sequences for dynamic contrast-enhanced MRI (DCE-MRI) by comparing them to conventional VIBE sequence using a phantom., Methods: On a DCE-MRI phantom containing various concentrations of NiCl2 solutions, six minutes of dynamic series and T1 mapping with variable flip angle methods were acquired using conventional VIBE, Radial-VIBE, and CAIPIRINHA-VIBE sequences on 3.0-T scanners. Signal stability and signal linearity were tested for dynamic series and the precision of R1 values were tested for T1 mapping series. The scans were repeatedly performed at two weeks and three months to test repeatability/reproducibility, assessed by within-subject coefficient of variation (WSCV)., Results: Signal stability over six minutes was excellent in all three sequences. Regarding the signal linearity, CAIPIRINHA-VIBE demonstrated the highest linear correlation (r=0.963), followed by conventional VIBE (r=0.959) and Radial-VIBE (r=0.953). Regarding the R1 precision, CAIPIRINHA-VIBE (r=0.985) was the most accurate, followed by conventional VIBE (r=0.861) and Radial-VIBE (r=0.442). CAIPIRINHA-VIBE showed excellent repeatability/reproducibility (WSCV, 1.79-6.71%) compared with Radial-VIBE (WSCV, 2.04-67.2%) and conventional VIBE (WSCV, 3.4-31.9%)., Conclusion: In terms of signal stability, signal linearity, R1 precision, and repeatability/reproducibility, CAIPIRINHA-VIBE demonstrated outstanding performance for DCE-MRI compared with Radial-VIBE and conventional VIBE., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Gadolinium ethoxybenzyl dimeglumine (gadoxetate) is a recently developed hepatocyte-specific MRI contrast medium. Gadoxetate demonstrates unique pharmacokinetic and pharmacodynamic properties, because its uptake in hepatocytes occurs via the organic anion transporting polypeptide (OATP) transporter expressed at the sinusoidal membrane, and its biliary excretion via the multidrug resistance-associated proteins (MRPs) at the canalicular membrane. Based on these characteristics, gadoxetate-enhanced MRI can provide functional information on hepatobiliary diseases, including liver function estimation, biliary drainage evaluation and characterization of hepatocarcinogenesis. In addition, understanding its mode of action can provide an opportunity to use gadoxetate for cellular and molecular imaging. Radiologists and imaging scientists should be familiar with the basic mechanism of gadoxetate and OATP/MRP transporters.

Nonalcoholic fatty liver disease (NAFLD) can lead to cirrhosis, hepatocellular carcinoma, and ultimately death. Magnetic resonance techniques are accurate, noninvasive methods for evaluating hepatic steatosis but, in animals, have not been fully validated against histologic findings. We sought to validate the MRI fat-signal fraction (MRI-FSF) used for diagnosing NAFLD in human nonclinical trials by comparing MRI data with histopathologic findings in C57BL/6J mice (n = 24) fed normal chow (controls) or a methionine- and choline-deficient (MCD) diet to induce NAFLD. Axial T2-weighted fast spin-echo images were used to examine the entire liver. For histopathologic analyses, liver slides were evaluated for hepatic steatosis according to the NAFLD activity score. Pearson correlation coefficient and receiver operating characteristics analyses were performed. According to the fat-fraction signal, the mean percentage of liver fat in mice with induced NAFLD was 57%, which correlated with the histologically determined steatosis grade. The proton-density fat fraction effectively distinguished severe from mild hepatic steatosis, with an AUC of 0.92. Evaluation accuracy decreased when lobular inflammation and hepatocellular ballooning were considered. This study showed strong concurrence between MRI-FSF and histopathologic steatosis in a murine model of NAFLD. MRI-FSF had moderate sensitivity and specificity in this context. These results confirm that the MRI is a useful biomarker of hepatic steatosis in NAFLD in murine model.

Accurate pharmacokinetic (PK) modeling of dynamic contrast enhanced MRI (DCE-MRI) in prostate cancer (PCa) requires knowledge of the concentration time course of the contrast agent in the feeding vasculature, the so-called arterial input function (AIF). The purpose of this study was to compare AIF choice in differentiating peripheral zone PCa from non-neoplastic prostatic tissue (NNPT), using PK analysis of high temporal resolution prostate DCE-MRI data and whole-mount pathology (WMP) validation. This prospective study was performed in 30 patients who underwent multiparametric endorectal prostate MRI at 3.0T and WMP validation. PCa foci were annotated on WMP slides and MR images using 3D Slicer. Foci ≥0.5cm(3) were contoured as tumor regions of interest (TROIs) on subtraction DCE (early-arterial - pre-contrast) images. PK analyses of TROI and NNPT data were performed using automatic AIF (aAIF) and model AIF (mAIF) methods. A paired t-test compared mean and 90th percentile (p90) PK parameters obtained with the two AIF approaches. Receiver operating characteristic (ROC) analysis determined diagnostic accuracy (DA) of PK parameters. Logistic regression determined correlation between PK parameters and histopathology. Mean TROI and NNPT PK parameters were higher using aAIF vs. mAIF (p<0.05). There was no significant difference in DA between AIF methods: highest for p90 volume transfer constant (K(trans)) (aAIF differences in the area under the ROC curve (Az) = 0.827; mAIF Az=0.93). Tumor cell density correlated with aAIF K(trans) (p=0.03). Our results indicate that DCE-MRI using both AIF methods is excellent in discriminating PCa from NNPT. If quantitative DCE-MRI is to be used as a biomarker in PCa, the same AIF method should be used consistently throughout the study., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Objective: We aimed to systematically review the gadoxetic acid-enhanced magnetic resonance imaging (Gd-EOB-DTPA-MRI) findings of focal nodular hyperplasia (FNH) and its diagnostic value., Methods: A thorough literature search was conducted in Ovid-MEDLINE and EMBASE databases to identify studies evaluating Gd-EOB-DTPA-MRI findings of FNH. To evaluate the frequency of characteristic imaging findings on Gd-EOB-DTPA-MRI, pooled proportions of high/iso signal intensity (SI) on the hepatobiliary phase (HBP), arterial enhancement, high/iso SI on the portal-venous phase (PVP) or equilibrium phase (EP), and the central scar were calculated. Meta-analysis was performed to evaluate the diagnostic accuracy of high/iso SI on HBP for distinguishing FNH from hepatocellular adenoma., Results: A review of 96 articles identified ten eligible articles with 304 patients with FNHs for meta-analysis. Pooled proportion of the Gd-EOB-DTPA-MRI findings showed that high/iso SI on the HBP, arterial enhancement, and high/iso SI on the PVP/EP were observed in 93% (95% CI, 90-97%), 99% (95% CI, 97-100%), and 97% (95% CI, 95-99%) of FNHs, respectively, while a central scar was observed in 61% of FNHs (95% CI, 47-74%). High/iso SI on the HBP was highly accurate for distinguishing FNH from hepatocellular adenoma, with a summary sensitivity of 93.9% (95% CI, 89.1-97.1%) and a specificity of 95.3% (95% CI, 88.4-98.7%)., Conclusions: High/iso SI on the HBP of Gd-EOB-DTPA-MRI is characteristic and a prevalent finding of FNHs and can be helpful in the management of patients with FNH., Key Points: • The vast majority (94-97 %) of FNHs show high/iso SI on HBP. • High/iso SI on HBP was accurate for distinguishing FNH from hepatocellular adenoma. • HBP of Gd-EOB-DTPA-MRI can reduce unnecessary biopsies for the diagnosis of FNHs.

Objective: To investigate the impact of liver magnetic resonance imaging (MRI) in staging evaluation of newly diagnosed colorectal cancer patients., Background: No clear guidelines regarding how to use liver MRI in evaluating newly diagnosed colorectal cancer., Methods: We included 863 adults who had newly diagnosed colorectal cancer without concomitant malignancies and received portal-phase contrast-enhanced abdominopelvic computed tomography (CT). Patients who had diminutive indeterminate hypoattenuating ["too-small-to-characterize" (TSTC)] hepatic lesions without other suspicious/indeterminate findings (TSTC-liver-on-CT), metastasis-negative hepatic findings (negative-liver-on-CT), and hepatic lesions suspicious or indeterminate for metastasis excluding TSTC lesions as seen on CT were identified. Per-patient rate of hepatic metastasis unsuspected by CT and the diagnostic yield of liver MRI for such lesions were assessed., Results: There were 261 TSTC-liver-on-CT patients, 464 negative-liver-on-CT patients, and 138 patients with suspicious hepatic findings on CT. Among TSTC-liver-on-CT patients, the rate of hepatic metastasis was 2.2% (5/230, excluding patients without follow-up) and the yield of liver MRI was 3% (3/96). Negative-liver-on-CT patients gave the MRI yield of 0% (0/94). Among negative-liver-on-CT patients, the rate of hepatic metastasis discovered within 6 months of curative surgery was 1.1% (4/350, excluding patients without follow-up) when the liver was cleared by negative CT alone and 2% (2/88, excluding patients without follow-up) when cleared also by negative MRI (P = 0.347). Among the patients who had suspicious hepatic findings on CT, the MRI yield was 25% (19/77)., Conclusions: The diagnostic yield of liver MRI for hepatic metastasis was very low in newly diagnosed colorectal cancer patients who showed TSTC hepatic lesions or metastasis-negative hepatic findings on CT. Staging liver MRI is likely unnecessary for them.

The purpose of this article is to provide a comprehensive update on the role of imaging in the diagnosis and management of penile cancer. Imaging plays a major role in the initial assessment, treatment planning, and follow-up of patients with penile carcinoma. MRI helps in assessing the T staging of the primary and in detecting local recurrence. PET/CT and CT are useful for detecting regional nodal and distant metastases.

Objectives: To evaluate the feasibility of free-breathing, dynamic contrast-enhanced (DCE) MRI of the abdomen and thorax using the radial-gradient-echo sequence with k-space weighted image contrast (KWIC) reconstruction., Methods: Institutional review board approval was obtained. Fourteen patients underwent free-breathing radial DCE-MRI. Radial MRI yielded full-frame images by gridding all k-space data and time-resolved subframe images by using KWIC reconstruction technique. Using subframe KWIC images, voxel-wise perfusion maps were created. For comparison, the breath-hold conventional Cartesian 3D-gradient-echo sequence (VIBE) was also performed during the equilibrium phase. The image qualities of radial and conventional VIBE images were compared quantitatively and qualitatively., Results: Radial DCE-MRI provided high spatial resolution (1.4 × 1.4 mm) and temporal resolution (4.1 s for subframe images) allowing voxel-wise perfusion mapping with negligible motion or streaking artefacts. There were no significant differences in SNR between full-frame radial images and conventional VIBE images (79.08 vs 74.80, P > 0.05). Overall image quality score of full-frame radial images was slightly lower than that of conventional VIBE images (3.88 ± 0.59 vs. 4.31 ± 0.97, P < 0.05), but provided clinically useful images., Conclusions: The free-breathing radial DCE-MRI can provide high spatial and temporal resolution while maintaining reasonably high image quality and thus is a feasible technique for DCE-MRI in the abdomen and thorax., Key Points: • Dynamic contrast-enhanced magnetic resonance imaging (DCE) MRI is important in oncological imaging • Radial MRI with k-space weighted image contrast (KWIC) reconstruction offers potential improvements • Radial DCE-MRI provides good image quality, reduced artefacts and high spatial/temporal resolution.

Purpose: To evaluate the diagnostic implications of the iterative decomposition of water and fat using echo-asymmetry and the least-squares estimation (IDEAL) technique to detect hepatic steatosis (HS) in potential liver donors using histopathology as the reference standard., Materials and Methods: Forty-nine potential liver donors (32 male, 17 female; mean age, 31.7 years) were included. All patients were imaged using the in- and out-of-phase (IOP) gradient-echo (GRE) and IDEAL techniques on a 1.5 T MR scanner. To estimate the hepatic fat fraction (FF), two reviewers performed regions-of-interest measurement in 15 areas of the liver seen on the IOP images and on the IDEAL-FF images. The magnetic resonance imaging (MRI) and pathology values of macrosteatosis were correlated using the Pearson correlation coefficient. We analyzed the diagnostic performance of IOP imaging and IDEAL for detecting HS., Results: The results of the hepatic-FF estimated on IDEAL were well correlated with the histologic degree of macrosteatosis (γ = 0.902, P < 0.001). IDEAL showed 100% sensitivity and 91% specificity for detecting HS, and IOP imaging showed 87.5% sensitivity and 97% specificity, respectively., Conclusion: IDEAL is a useful tool for the preoperative diagnosis of HS in potential living liver donors; it can also help to avoid unnecessary biopsies in these patients., (Copyright © 2012 Wiley Periodicals, Inc.)

Objectives: To determine the characteristic enhancing features of hepatocellular carcinoma (HCC) and arterial-enhancing pseudolesion (AEP) on gadoxetic acid (Primovist)-enhanced magnetic resonance imaging (MRI) and to assess its performance compared with that of multirow detector computed tomography (MDCT) for differentiating small HCC (< or =2 cm in diameter) from AEP in cirrhotic liver., Materials and Methods: A total of 69 patients with 97 small, arterial enhancing hepatic lesions (0.5-2 cm in diameter), ie, 44 HCCs and 53 AEPs, detected on gadoxetic acid-enhanced MRI, were included in this study. HCCs were diagnosed either through histopathology confirmation (n = 16) or by a combination of liver computed tomography (CT), angiographic findings, lipiodol CT, and AFP levels (n = 28). AEPs were diagnosed either through histopathology confirmation (n = 2) or were based on the angiographic findings, liver CT, and follow-up imaging (n = 51). Two radiologists jointly analyzed the morphologic features and the enhancement characteristics on the gadoxetic acid-enhanced MRI. Of the 69 study patients, 42 patients with 60 arterial enhancing lesions underwent quadruple-phase CT in addition to their MRI examination within 4 weeks before or after the MRI, and 2 other radiologists who were blinded to the final diagnosis independently reviewed the MRI and CT images in random order, at an interval of 2 weeks. Diagnostic performance was evaluated using receiver operating characteristics. The Kappa test was used to evaluate interobserver agreement., Results: Among 44 HCCs, 42 (95.4%) demonstrated low signal intensity (SI) and only 2 showed iso- or high SI on the hepatobiliary phase of gadoxetic acid-enhanced MRI. Alternatively, most AEPs showed iso SI on the hepatobiliary (n = 50, 94.3%) phase, and only 2 AEPs showed low SI. Compared with the diagnostic performance of the 2 imaging modalities, the mean areas under the receiver-operator characteristic curves on MR imaging were 0.975 for reviewer 1 and 0.966 for reviewer 2, whereas those of CT imaging were 0.892 for reviewer 1 and 0.888 for reviewer 2 (P = 0.069 and P = 0.106, respectively). The sensitivity for each reviewer with MR imaging (93.9% and 90.9%, respectively) was significantly higher than that with multiphasic CT (54.5%, in both) (P = 0.001 and 0.0018, respectively)., Conclusion: HCCs and AEPs show different enhancing features on the delayed dynamic and hepatobiliary phases of gadoxetic acid-enhanced MRI. Gadoxetic acid-enhanced MRI may, therefore, help to differentiate between HCC and AEP.

Purpose: To retrospectively evaluate the MR imaging features of early bile duct cancer and to correlate them with the clinicopathologic findings., Materials and Methods: This retrospective study was approved by our institutional review board, and informed consent was waived. Seventeen patients with surgically proven early bile duct cancer who had undergone preoperative MR cholangiopancreatography with gadolinium-enhanced MR imaging, were included in this study. Two, experienced radiologists evaluated the MR images in consensus regarding the following findings: tumor number and morphology; signal intensity of the tumor; sharpness of the outer border of the bile duct wall; enhancement pattern of the tumor; and the presence of enlarged peribiliary lymph nodes. Another radiologist measured the SNR of the tumor and bile duct wall on gadolinium-enhanced MRI during the dynamic phases to evaluate the tumor enhancement degree., Results: In all patients, MR imaging demonstrated single or multiple intraluminal bile duct masses showing a sharply defined outer margin. The most common enhancement pattern of the biliary lesions showed heterogeneous amorphous enhancement or heterogeneous enhancement with central, dot-like structures or vascular structures (76.5%, 13/17 patients). The difference of SNR between bile duct and tumor was greatest in the equilibrium phase (P < 0.05)., Conclusion: MRCP combined with dynamic contrast-enhanced MRI can be useful for detecting early bile duct cancers. Common MR findings of early bile duct cancer include one or more inhomogeneously enhancing intraductal masses with clear outer margins and preservation of the bile duct wall., ((c) 2008 Wiley-Liss, Inc.)

Background: To use the apparent diffusion coefficient (ADC) as reliable biomarkers, validation of MRI equipment performance and clinical acquisition protocols should be performed prior to application in patients. This study aims to validate various MRI equipment and clinical brain protocols for diffusion weighted imaging (DWI) using commercial phantom, and confirm the validated protocols in patients' images. Methods: The performance of four different scanners and clinical brain protocols were validated using a Quantitative Imaging Biomarker Alliance (QIBA) diffusion phantom and cloud-based analysis tool. We evaluated the performance metrics regarding accuracy and repeatability of ADC measurement using QIBA profile. The validated clinical brain protocols were applied to 17 patients, and image quality and repeatability of ADC were assessed. Results: The MRI equipment performance of all four MRI scanners demonstrated high accuracy in ADC measurement (ADC bias, −2.3% to −0.4%), excellent linear correlation to the reference ADC value (slope, 0.9 to 1.0; R2, 0.999–1.000), and high short-term repeatability [within-subject-coefficient-of-variation (wCV), 0% to 0.3%]. The clinical protocols were also validated by fulfilling QIBA claims with high accuracy (ADC bias, −3.1% to −0.7%) and robust repeatability (wCV, 0% to 0.1%). Brain DWI acquired using the validated clinical protocols showed ideal image quality (mean score ≥ 2.9) and good repeatability (wCV, 1.8–2.2). Conclusions: The whole process of standardization of DWI demonstrated the robustness of ADC with high accuracy and repeatability across diverse MRI equipment and clinical protocols in accordance with the QIBA claims. [ABSTRACT FROM AUTHOR]

Chemical exchange saturation transfer with glutamate (GluCEST) imaging is a novel technique for the non-invasive detection and quantification of cerebral Glu levels in neuromolecular processes. Here we used GluCEST imaging and 1H magnetic resonance spectroscopy (1H MRS) to assess in vivo changes in Glu signals within the hippocampus in a rat model of depression induced by a forced swim test. The forced swimming test (FST) group exhibited markedly reduced GluCEST-weighted levels and Glu concentrations when examined using 1H MRS in the hippocampal region compared to the control group (GluCEST-weighted levels: 3.67 ± 0.81% vs. 5.02 ± 0.44%, p < 0.001; and Glu concentrations: 6.560 ± 0.292 μmol/g vs. 7.133 ± 0.397 μmol/g, p = 0.001). Our results indicate that GluCEST imaging is a distinctive approach to detecting and monitoring Glu levels in a rat model of depression. Furthermore, the application of GluCEST imaging may provide a deeper insight into the neurochemical involvement of glutamate in various psychiatric disorders. [ABSTRACT FROM AUTHOR]

We propose a self-supervised machine learning (ML) algorithm for sequence-type classification of brain MRI using a supervisory signal from DICOM metadata (i.e., a rule-based virtual label). A total of 1787 brain MRI datasets were constructed, including 1531 from hospitals and 256 from multi-center trial datasets. The ground truth (GT) was generated by two experienced image analysts and checked by a radiologist. An ML framework called ImageSort-net was developed using various features related to MRI acquisition parameters and used for training virtual labels and ML algorithms derived from rule-based labeling systems that act as labels for supervised learning. For the performance evaluation of ImageSort-net (MLvirtual), we compare and analyze the performances of models trained with human expert labels (MLhumans), using as a test set blank data that the rule-based labeling system failed to infer from each dataset. The performance of ImageSort-net (MLvirtual) was comparable to that of MLhuman (98.5% and 99%, respectively) in terms of overall accuracy when trained with hospital datasets. When trained with a relatively small multi-center trial dataset, the overall accuracy was relatively lower than that of MLhuman (95.6% and 99.4%, respectively). After integrating the two datasets and re-training them, MLvirtual showed higher accuracy than MLvirtual trained only on multi-center datasets (95.6% and 99.7%, respectively). Additionally, the multi-center dataset inference performances after the re-training of MLvirtual and MLhumans were identical (99.7%). Training of ML algorithms based on rule-based virtual labels achieved high accuracy for sequence-type classification of brain MRI and enabled us to build a sustainable self-learning system. [ABSTRACT FROM AUTHOR]

The accurate differential diagnosis between autoimmune pancreatitis (AIP) and pancreatic ductal adenocarcinoma (PDAC) is clinically important. We aimed to determine significant MRI features for differentiating AIP from PDAC, including assessment of diffusion-weighted imaging (DWI). We performed a systematic search using three databases. The pooled diagnostic odds ratio was calculated using a bivariate random effects model to determine significant MRI features for differentiating AIP from PDAC. The pooled sensitivity and specificity were calculated. The qualitative systematic review for DWI assessment was performed. Of nine studies (775 patients), multiple main pancreatic duct (MPD) strictures, absence of upstream marked MPD dilatation, peripancreatic rim, and duct penetration sign were significant MRI features for differentiating AIP from PDAC. Absence of MPD dilatation had the highest pooled sensitivity (87%, 95% CI=68–96%), whereas peripancreatic rim had the highest pooled specificity (100%, 95% CI=88–100%). Of 12 studies evaluating DWI, seven reported statistically significant differences in apparent diffusion coefficient (ADC) values between AIP and PDAC; however, four reported lower ADC values in AIP than in PDAC, but three reported the opposite result. The four significant MRI features can be useful to differentiate AIP from PDAC, but DWI assessment might be limited. [ABSTRACT FROM AUTHOR]

Background: The latest International Myeloma Working Group (IMWG) guideline recommends low-dose whole-body (WB) computed tomography (CT) as the first-line imaging technique for the initial diagnosis of plasma cell disorders. Purpose: To evaluate diagnostic performances of CT and diffusion-weighted imaging (DWI) as the first-line imaging modalities and assess misclassification rates obtained following the guideline. Material and Methods: Two independent radiologists analyzed CT (acquired as PET/CT) and DWI (3-T; b-values = 50 and 900 s/mm2) of patients newly diagnosed with plasma cell disorder, categorizing the number of bone lesions. Diagnostic performance of CT and DWI was compared using the McNemar test, and misclassification rates were calculated with a consensus WB-MRI reading as the reference standard. Differences in lesion number categories were assessed using marginal homogeneity and kappa statistics. Results: Of 56 patients (36 men; mean age = 63.5 years), 39 had myeloma lesions. DWI showed slightly higher sensitivity for detecting myeloma lesions (97.4%) than CT (84.6%–92.3%; P > 0.05). CT showed significantly higher specificity (88.2%) than DWI (52.9%–58.8%; P <0.05). CT had a higher additional study requirement rate than DWI (7.7%–15.4% vs. 2.6%), but a lower unnecessary treatment rate (11.8% vs. 41.2%–47.1%). Both readers showed significant differences in categorization of the number of lesions on CT compared with the reference standard (P < 0.001), and one reader showed a significant difference on DWI (P = 0.006 and 0.098). Conclusion: CT interpreted according to the IMWG guideline is a diagnostically effective first-line modality with relatively high sensitivity and specificity. DWI alone may not be an acceptable first-line imaging modality because of low specificity. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the feasibility of a newly developed anticancer drug-releasing radiofrequency ablation (RFA) system in a porcine liver model. A 15-gauge drug-releasing cooled wet electrode (DRCWE) was newly developed to improve the RFA efficacy for creating a large ablation as well as for simultaneously delivering an anticancer drug to the tumor margin. Nine ablations in three pigs were performed by the DRCWE. The sectioned liver specimens were evaluated by measuring the ablation zone by a positron emission tomography/magnetic resonance imaging examination to investigate whether 18F-fluorodeoxyglucose was exactly diffused. Volumes of the ablation zones released drug injection volumes, circularity, retention rate defined as the ratio between an estimated and injection dose, and the standard uptake value were assessed. The drug-releasing RFA was technically successful without procedural-related complications. During the procedure, the color changes of the ablated zones of the liver were observed in all specimens. The mean drug injection volume was higher than the ablated volumes (17.21 ± 2.85 vs. 15.22 ± 2.30 cm3) and the circularity was 0.72 ± 0.08. Moreover, the retention rate was 72.89% ± 4.22% and the mean standard uptake value was 0.44 ± 0.05. The drug-releasing RFA system was feasible not only for local ablation but also for the delivery of anticancer drugs. The results of this study indicate that this novel strategy of localized RFA with a drug delivery system could be a promising option for the prevention of local recurrence rates. [ABSTRACT FROM AUTHOR]

Background: Use of the Liver Imaging Reporting and Data System (LI-RADS) is increasing, but the reported results for interreader agreement seem quite variable.Purpose: To systematically determine the interreader agreement of LI-RADS on magnetic resonance imaging (MRI) and to determine the sources of heterogeneity between the reported results.Study Type: Systematic review and meta-analysis.Subjects: Fifteen original articles with 2968 lesions.Field Strength: 1.5T and 3.0T.Assessment: Two reviewers independently performed the data extraction. The reviewers identified and reviewed the original articles reporting the interreader agreement of LI-RADS using MRI.Statistical Tests: The meta-analytic pooled intraclass correlation coefficient (ICC) for lesion size and kappa value (κ) for major features (arterial-phase hyperenhancement [APHE], nonperipheral washout [WO], enhancing capsule [EC]) and LI-RADS categorization (LR) were calculated using the random-effects model. Sensitivity analysis and meta-regression analysis were performed to explore the cause of study heterogeneity.Results: The meta-analytic pooled ICC of lesion size was 0.97 (95% confidence interval [CI], 0.94-1.00). Meta-analytic pooled κ of APHE, WO, EC, and LR were 0.72 (95% CI, 0.62-0.82), 0.69 (95% CI, 0.60-0.78), 0.66 (95% CI, 0.58-0.74), and 0.70 (95% CI, 0.56-0.85), respectively. Substantial study heterogeneity was noted in all five variables (I2  ≥ 89.1%, P < 0.001). Study design, type, and clarity of blinding review were factors that significantly influenced study heterogeneity (P ≤ 0.05).Data Conclusion: LI-RADS demonstrated overall substantial interreader agreement for major features and the category on MRI, but showed heterogeneous results between studies.Level Of Evidence: 3 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:795-804. [ABSTRACT FROM AUTHOR]

Background: Determining if a given patient with primary pancreatic adenocarcinoma (PDA) has hepatic metastasis is important for treatment planning. Several previous studies reported on the diagnostic performance of MRI for liver metastasis in patients with PDA. But the reported data are quite variable.Purpose: To systematically determine the diagnostic performance of MRI for liver metastasis in patients with PDA, including comparing it with computed tomography (CT).Study Type: Systemic review and meta-analysis.Subjects: In all, 457 patients from five eligible articles.Field Strength/sequence: Conventional MR sequences with or without contrast enhancement at 1.5T and 3T.Assessment: Two reviewers independently performed the data extraction. The reviewers identified and reviewed the original articles reporting the diagnostic performance of MRI for liver metastases in patients with PDA, including those articles making comparisons with CT.Statistical Tests: Meta-analytic summary sensitivity and specificity were calculated on a per-patient basis using a bivariate random effects model. We compared the meta-analytic summary sensitivity and specificity between MRI and CT.Results: The meta-analytic summary sensitivity and specificity were 85% (95% confidence interval [CI], 74-92%; I2 = 0%) and 98% (95% CI, 78-100%; I2 = 85%), respectively. In comparison with CT, MRI showed a higher sensitivity (85% vs. 75%) but similar specificity (98% vs. 94%).Data Conclusion: MRI had good overall diagnostic performance for liver metastasis in patients with PDA, with a higher sensitivity than CT.Level Of Evidence: 3 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:1737-1744. [ABSTRACT FROM AUTHOR]

Background and Aims: The Liver Imaging Reporting and Data System (LI‐RADS) category M (LR‐M) was introduced to preserve the high specificity of LI‐RADS algorithm for diagnosing hepatocellular carcinoma (HCC). We aimed to systematically determine the probability of the LR‐M for HCC and non‐HCC malignancy, and to determine the sources of heterogeneity between reported results. Methods: Original studies reporting the probability of LR‐M for HCC and non‐HCC malignancy on magnetic resonance imaging (MRI) were identified in MEDLINE and EMBASE. The meta‐analytic pooled percentages of HCC and non‐HCC in LR‐M were calculated. Meta‐regression analysis was performed to explore study heterogeneity. The meta‐analytic frequency of each LR‐M imaging feature was determined. Results: We found 10 studies reporting the diagnostic performance of LR‐M (1819 lesions in 1631 patients), and six reporting the frequency of LR‐M imaging features. The pooled percentages of HCC and non‐HCC malignancy for LR‐M were 28.2% (95% confidence interval [CI], 23.8%‐33.1%; I2 = 83%) and 69.6% (95% CI, 64.6%‐74.1%; I2 = 83%) respectively. The study type and MRI scanner field strength were significantly associated with study heterogeneity (P ≤.04). Of the seven imaging features, rim arterial phase hyperenhancement showed the highest frequency in both non‐HCC (48.9%; 95% CI, 43.0%‐54.8%) and HCC groups (9.8%; 95% CI, 6.9%‐13.6%). Conclusions: The LR‐M category most commonly included non‐HCC malignancy but also included 28.2% of HCC. Substantial study heterogeneity was noted, and it was significantly associated with study type and MRI scanner field strength. In addition, the frequency of LR‐M imaging features was variable. [ABSTRACT FROM AUTHOR]

Background: Quantification of abdominal muscle mass by cross-sectional imaging has been increasingly used to diagnose sarcopenia; however, the technical method for quantification has not been standardized yet. We aimed to determine an optimal method to measure the abdominal muscle area. Methods: Among 50 consecutive subjects who underwent abdominal CT and MRI for possible liver donation, total abdominal muscle area (TAMA) and total psoas muscle area (TPA) at the L3 inferior endplate level were measured by two blinded readers. Inter-scan agreement between CT and MRI and inter-reader agreement between the two readers were evaluated using intraclass correlation coefficient (ICC) and within-subject coefficient of variation (WSCV). To evaluate the effect of measurement level, one reader measured TAMA and TPA at six levels from the L2 to L4 vertebral bodies. Results: TAMA was a more reliable biomarker than TPA in terms of inter-scan agreement (ICC: 0.928 vs. 0.788 for reader 1 and 0.853 vs. 0.821 for reader 2, respectively; WSCV: 8.3% vs. 23.4% for reader 1 and 10.4% vs. 22.3% for reader 2, respectively) and inter-reader agreement (ICC: 0.986 vs. 0.886 for CT and 0.865 vs. 0.669 for MRI, respectively; WSCV: 8.2% vs. 16.0% for CT and 11.6% vs. 29.7% for MRI, respectively). In terms of the measurement level, TAMA did not differ from the L2inf to L4inf levels, whereas TPA increased with a decrease in measurement level. Conclusions: TAMA is a better biomarker than TPA in terms of inter-scan and inter-reader agreement and robustness to the measurement level. CT was a more reliable imaging modality than MRI. Our results support the use of TAMA measured by CT as a standard biomarker for abdominal muscle area measurement. [ABSTRACT FROM AUTHOR]

Recent advances in imaging technology have enabled the acquisition of anatomical and functional imaging from head to toe in a reasonably short scan time. Accordingly, whole body magnetic resonance imaging (WB-MRI) and diffusion-weighted imaging (WB-DWI) have gained recent attention for the management of musculoskeletal problems such as bone tumors and rheumatologic diseases. WB-MRI is especially useful in diagnosing systemic or widespread disease requiring whole body evaluation, such as bone metastases, multiple myeloma, lymphoma, neurofibromatosis, and spondyloarthropathies. Among WB-MRI sequences, the WB-DWI technique greatly increases the value of WB-MRI in the evaluation of disease extent and characterization as well as treatment monitoring. In support of the utilization of WB-MRI and WB-DWI in orthopedic clinics for various musculoskeletal diseases, we provide an overview of the technical aspects of WB-MRI and WB-DWI and their clinical applications in musculoskeletal tumors and rheumatic diseases. [ABSTRACT FROM AUTHOR]

Objectives: To systematically determine the diagnostic accuracy of 18-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging ([18F]FDG-PET/MRI) for the detection of liver metastases and evaluate the sources of heterogeneity in the reported results.Methods: PubMed and EMBASE databases were searched up until December 31, 2017, to identify original research studies reporting the diagnostic performance (Se and Sp) of PET/MRI for liver metastases, in comparison with PET/CT. Study quality was assessed using QUADAS-2. The summary Se and Sp of the studies were estimated using hierarchical modeling methods. To determine causes of study heterogeneity, the presence of a threshold effect was analyzed, and meta-regression analysis was performed.Results: Of 546 articles screened, eight suitable articles were identified, with seven for per-lesion analysis, and four for per-patient analysis. The meta-analytic summary Se and Sp for per-patient-based analysis were 99.2% (95% CI, 31.4-100.0%, I2 = 89.4%) and 98.6% (95% CI, 84.0-99.9%, I2 = 0.0%), respectively, while for per-lesion-based analysis they were 95.4% (95% CI, 78.3-99.2%, I2 = 99.7%) and 99.3% (95% CI, 93.8-99.9%, I2 = 96.5%). PET/MRI showed higher Se (95.4% vs. 68.3%) and Sp (99.3% vs. 95.8%) than PET/CT. Meta-regression analysis showed five significant factors affecting study heterogeneity: study subject characteristics, study design, MRI technique (DWI, HBP after injection of liver-specific contrast media), imaging review method, and reference standard.Conclusion: The diagnostic accuracy of [18F]FDG-PET/MRI for liver metastasis was high overall, but substantial heterogeneity was found. Further randomized controlled studies or prospective studies are needed to investigate the role of PET/MRI in liver metastasis in comparison with PET/CT.Key Points: • [ 18 F]FDG-PET/MRI has high meta-analytic Se and Sp for the diagnosis of liver metastasis. • PET/MRI using DWI and HBP images significantly increased diagnostic accuracy. • Study heterogeneity was associated with subject characteristics, study design, MRI technique, image review method, and reference standard. [ABSTRACT FROM AUTHOR]

Emerging evidence has suggested that hydrogen sulfide (H2S) may alleviate the cellular damage associated with cerebral ischemia/reperfusion (I/R) injury. In this study, we assessed using 1H-magnetic resonance imaging/magnetic resonance spectroscopy (1H-MRI/MRS) and histologic analysis whether H2S administration prior to reperfusion has neuroprotective effects. We also evaluated for differences in the effects of H2S treatment at 2 time points. 1H-MRI/MRS data were obtained at baseline, and at 3, 9, and 24 h after ischemia from 4 groups: sham, control (I/R injury), sodium hydrosulfide (NaHS)-30 and NaHS-1 (NaHS delivery at 30 and 1 min before reperfusion, respectively). The total infarct volume and the midline shift at 24 h post-ischemia were lowest in the NaHS-1, followed by the NaHS-30 and control groups. Peri-infarct volume was significantly lower in the NaHS-1 compared to NaHS-30 and control animals. The relative apparent diffusion coefficient (ADC) in the peri-infarct region showed that the NaHS-1 group had significantly lower values compared to the NaHS-30 and control animals and that NaHS-1 rats showed significantly higher relative T2 values in the peri-infarct region compared to the controls. The relative ADC value, relative T2 value, levels of N-acetyl-L-aspartate (NAA), and the NAA, glutamate, and taurine combination score (NGT) in the ischemic core region at 24 h post-ischemia did not differ significantly between the 2 NaHS groups and the control except that the NAA and NGT values were higher in the peri-infarct region of the NaHS-1 animals at 9 h post-ischemia. In the ischemic core and peri-infarct regions, the apoptosis rate was lowest in the NaHS-1 group, followed by the NaHS-30 and control groups. Our results suggest that H2S treatment has neuroprotective effects on the peri-infarct region during the evolution of I/R injury. Furthermore, our findings indicate that the administration of H2S immediately prior to reperfusion produces the highest neuroprotective effects. [ABSTRACT FROM AUTHOR]

Background: This study analyzes the clinicopathologic and radiologic characteristics of malignant serous cystic neoplasm (SCN) of the pancreas through systematic review and an institutional case report. Methods: A comprehensive literature search was performed in the MEDLINE database to identify studies on malignant SCNs of the pancreas that had detailed clinicopathologic and radiologic information. A computerized systematic search of our institutional database was also performed to identify cases of malignant SCN for addition to the systematic review. Using the final included cases, we analyzed the clinicopathologic and radiologic features of malignant SCNs of the pancreas. Results: A review of 136 candidate articles identified 26 studies with 26 cases that had detailed clinical information. Our institutional data search added one case. The systematic review of the 27 cases revealed that primary tumors (mean diameter 10.2 ± 4.0 cm) mainly involved the body and tail of the pancreas (n = 16) and frequently invaded adjacent organs (n = 19). Distant metastases occurred in 14 patients (synchronous, n = 5; metachronous, n = 8; both, n = 1), most commonly in the liver (n = 13). Imaging features of malignant SCNs of the pancreas were identical to the benign counterpart, except local invasion or distant metastases. The prognosis was excellent in that 17 were alive at the time of writing with a median follow-up period of 2 years. Conclusions: The malignant potential of SCNs of the pancreas should be considered in the diagnosis and management of patients with pancreatic SCNs. [ABSTRACT FROM AUTHOR]