Is it a normal phenomenon for pediatric patients to have brain leptomeningeal contrast enhancement on 3-tesla magnetic resonance imaging?

Determining whether sevoflurane sedation in children leads to“pseudo”prominent leptomeningeal contrast enhancement(pLMCE)on 3 Tesla magnetic resonance imaging will help reduce overdiagnosis by radiologists and clarify the pathophysiological changes of pLMCE.

Liver metastases:Contrast-enhanced ultrasound compared with computed tomography and magnetic resonance

The development of ultrasound contrast agents with excellent tolerance and safety profiles has notably improved liver evaluation with ultrasound(US)for several applications,especially for the detection of metastases.In particular,contrast enhanced ultrasonography(CEUS)allows the display of the parenchymal microvasculature,enabling the study and visualization of the enhancement patterns of liver lesions in real time and in a continuous manner in all vascular phases,which is similar to contrast-enhanced computed tomography(CT)and contrast-enhanced magnetic resonance imaging.Clinical studies have reported that the use of a contrast agent enables the visualization of more metastases with significantly improved sensitivity and specificity compared to baseline-US.Furthermore,studies have shown that CEUS yields sensitivities comparable to CT.In this review,we describe the state of the art of CEUS for detecting colorectal liver metastases,the imaging features,the literature reports of metastases in CEUS as well as its technique,its clinical role and its potential applications.Additionally,the updated international consensus panel guidelines are reported in this review with the inherent limitations of this technique and best practice experiences.

Discrimination of Metastatic from Non-metastatic Mesorectal Lymph Nodes in Rectal Cancer Using Quantitative Dynamic Contrast-Enhanced Magnetic Resonance Imaging

Preoperative detection of lymph nodes（LNs） metastasis is always highly challenging for radiologists nowadays. The utility of quantitative dynamic contrast-enhanced magnetic resonance imaging（QDCE-MRI） in identifying LNs metastasis is not well understood. In the present study, 59 patients with histologically proven rectal carcinoma underwent preoperative QDCE-MRI. The short axis diameter ratio, long axis diameter ratio, short-to-long axis diameter ratio and QDEC-MRI parameters（Ktrans, Kep, fPV and Ve） values were compared between the non-metastatic（n=44） and metastatic（n=35） LNs groups based on pathological examination. Compared with the non-metastatic group, the metastatic group exhibited significantly higher short axis diameter（7.558±0.668 mm vs. 5.427±0.285 mm）, Ktrans（0.483±0.198 min-1 vs. 0.218±0.116 min^-1） and Ve（0.399±0.118 vs. 0.203±0.096） values（all P〈0.05）. The short-to-long axis diameter ratio, long axis diameter ratio, Kep and fPV values did not show significant differences between the two groups. In conclusion, our results showed that for LNs larger than 5 mm in rectal cancer, there are distinctive differences in the Ktrans and Ve values between the metastatic and non-metastatic LNs, suggesting that QDCE-MRI may be potentially helpful in identifying LNs status.

Does sevoflurane sedation in pediatric patients lead to“pseudo”leptomeningeal enhancement in the brain on 3 Tesla magnetic resonance imaging?

BACKGROUND Prominent leptomeningeal contrast enhancement(LMCE)in the brain is observed in some pediatric patients during sedation for imaging.However,based on clinical history and cerebrospinal fluid analysis,the patients are not acutely ill and do not exhibit meningeal signs.Our study determined whether sevoflurane inhalation in pediatric patients led to this pattern of‘pseudo’LMCE(pLMCE)on 3 Tesla magnetic resonance imaging(MRI).AIM To highlight the significance of pLMCE in pediatric patients undergoing enhanced brain MRI under sedation to avoid misinterpretation in reports.METHODS A retrospective cross-sectional evaluation of pediatric patients between 0-8 years of age was conducted.The patients underwent enhanced brain MRI under inhaled sevoflurane.The LMCE grade was determined by two radiologists,and interobserver variability of the grade was calculated using Cohen’s kappa.The LMCE grade was correlated with duration of sedation,age and weight using the Spearman rho rank correlation.RESULTS A total of 63 patients were included.Fourteen(22.2%)cases showed mild LMCE,48(76.1%)cases showed moderate LMCE,and 1 case(1.6%)showed severe LMCE.We found substantial agreement between the two radiologists in detection of pLMCE on post-contrast T1 imaging(kappa value=0.61;P<0.001).Additionally,we found statistically significant inverse and moderate correlations between patient weight and age.There was no correlation between duration of sedation and pLMCE.CONCLUSION pLMCE is relatively common on post-contrast spin echo T1-weighted MRI of pediatric patients sedated by sevoflurane due to their fragile and immature vasculature.It should not be misinterpreted for meningeal pathology.Knowing pertinent clinical history of the child is an essential prerequisite to avoid radiological overcalling and the subsequent burden of additional investigations.

Dual-input two-compartment pharmacokinetic model of dynamic contrast-enhanced magnetic resonance imaging in hepatocellular carcinoma

AIM: To investigate the feasibility of a dual-input two-compartment tracer kinetic model for evaluating tumorous microvascular properties in advanced hepatocellular carcinoma(HCC). METHODS: From January 2014 to April 2015, we prospectively measured and analyzed pharmacokinetic parameters [transfer constant(K_(trans)), plasma flow(F_p), permeability surface area product(PS), efflux rate constant(k_(ep)), extravascular extracellular space volume ratio(V_e), blood plasma volume ratio(V_p), and hepatic perfusion index(HPI)] using dual-input two-compartment tracer kinetic models [a dual-input extended Tofts model and a dual-input 2-compartment exchange model(2CXM)] in 28 consecutive HCC patients. A well-known consensus that HCC is a hypervascular tumor supplied by the hepatic artery and the portal vein was used as a reference standard. A paired Student's t-test and a nonparametric paired Wilcoxon rank sum test were used to compare the equivalent pharmacokinetic parameters derived from the two models, and Pearson correlation analysis was also applied to observe the correlations among all equivalent parameters. The tumor size and pharmacokinetic parameters were tested by Pearson correlation analysis, while correlations among stage, tumor size and all pharmacokinetic parameters were assessed by Spearman correlation analysis. RESULTS: The F_p value was greater than the PS value(F_P = 1.07 m L/m L per minute, PS = 0.19 m L/m L per minute) in the dual-input 2CXM; HPI was 0.66 and 0.63 in the dual-input extended Tofts model and the dualinput 2CXM, respectively. There were no significant differences in the K_(ep), V_p, or HPI between the dual-input extended Tofts model and the dual-input 2CXM(P = 0.524, 0.569, and 0.622, respectively). All equivalent pharmacokinetic parameters, except for V_e, were correlated in the two dual-input two-compartment pharmacokinetic models; both Fp and PS in the dualinput 2CXM were correlated with K_(trans) derived from the dual-input extended Tofts model(P = 0.002, r = 0.566; P = 0.002, r = 0.570); K_(ep), V_p, and HPI between the two kinetic models were positively correlated(P = 0.001, r = 0.594; P = 0.0001, r = 0.686; P = 0.04, r = 0.391, respectively). In the dual input extended Tofts model, V_e was significantly less than that in the dual input 2CXM(P = 0.004), and no significant correlation was seen between the two tracer kinetic models(P = 0.156, r = 0.276). Neither tumor size nor tumor stage was significantly correlated with any of the pharmacokinetic parameters obtained from the two models(P > 0.05).CONCLUSION: A dual-input two-compartment pharmacokinetic model(a dual-input extended Tofts model and a dual-input 2CXM) can be used in assessing the microvascular physiopathological properties before the treatment of advanced HCC. The dual-input extended Tofts model may be more stable in measuring the V_e; however, the dual-input 2CXM may be more detailed and accurate in measuring microvascular permeability.

Texture analysis on parametric maps derived from dynamic contrast-enhanced magnetic resonance imaging in head and neck cancer

AIM: To investigate the merits of texture analysis on parametric maps derived from pharmacokinetic modeling with dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) as imaging biomarkers for the prediction of treatment response in patients with head and neck squamous cell carcinoma(HNSCC). METHODS: In this retrospective study,19 HNSCC patients underwent pre- and intra-treatment DCEMRI scans at a 1.5T MRI scanner. All patients had chemo-radiation treatment. Pharmacokinetic modeling was performed on the acquired DCE-MRI images,generating maps of volume transfer rate(Ktrans) and volume fraction of the extravascular extracellular space(ve). Image texture analysis was then employed on maps of Ktrans and ve,generating two texture measures: Energy(E) and homogeneity.RESULTS: No significant changes were found for the mean and standard deviation for Ktrans and ve between pre- and intra-treatment(P > 0.09). Texture analysis revealed that the imaging biomarker E of ve was significantly higher in intra-treatment scans,relative to pretreatment scans(P < 0.04). CONCLUSION: Chemo-radiation treatment in HNSCC significantly reduces the heterogeneity of tumors.

Diagnostic performance of contrast-enhanced ultrasound and enhanced magnetic resonance for breast nodules

In the current study, we sought to evaluate the diagnostic efficacies of conventional ultrasound（US）, contrastenhanced US（CEUS）, combined US and CEUS and magnetic resonance imaging（MRI） in detecting focal solid breast lesions. Totally 117 patients with 120 BI-RADS category 4A-5 breast lesions were evaluated by conventional US and CEUS, and MRI, respectively. SonoVue was used as contrast agent in CEUS and injected as an intravenous bolus; nodule scan was performed 4 minutes after bolus injection. A specific sonographic quantification software was used to obtain color-coded maps of perfusion parameters for the investigated lesion, namely the time-intensity curve.The pattern of contrast enhancement and related indexes regarding the time-intensity curve were used to describe the lesions, comparatively with pathological results. Histopathologic examination revealed 46 benign and 74 malignant lesions. Sensitivity, specificity, and accuracy of US in detecting malignant breast lesions were 90.14%, 95.92%, and 92.52%, respectively. Meanwhile, CE-MRI showed sensitivity, specificity, and accuracy of 88.73%, 95.92%, and91.67%, respectively. The area under the ROC curve for combined US and CEUS in discriminating benign from malignant breast lesions was 0.936, while that of MRI was 0.923, with no significant difference between them, as well as among groups. The time-intensity curve of malignant hypervascular fibroadenoma and papillary lesions mostly showed a fast-in/fast-out pattern, with no good correlation between them（kappa 〈0.20）. In conclusion, the combined use of conventional US and CEUS displays good agreement with MRI in differentiating benign from malignant breast lesions.

Dynamic contrast-enhanced magnetic resonance imaging of prostate cancer: A review of current methods and applications

In many areas of oncology, dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI) has proven to be a clinically useful, non-invasive functional imaging technique to quantify tumor vasculature and tumor perfusion characteristics. Tumor angiogenesis is an essential process for tumor growth, proliferation, and metastasis. Malignant lesions demonstrate rapid extravasation of contrast from the intravascular space to the capillary bed due to leaky capillaries associated with tumor neovascularity. DCE-MRI has the potential to provide information regarding blood flow, areas of hypoperfusion, and variations in endothelial permeability and microvessel density to aid treatment selection, enable frequent monitoring during treatment and assess response to targeted therapy following treatment. This review will discuss the current status of DCE-MRI in cancer imaging, with a focus on its use in imaging prostate malignancies as well as weaknesses that limit its widespread clinical use. The latest techniques for quantification of DCE-MRI parameters will be reviewed and compared.

Prediction of radiosensitivity in primary central nervous system germ cell tumors using dynamic contrast-enhanced magnetic resonance imaging

Objective： To evaluate the feasibility of dynamic contrast-enhanced magnetic resonance imaging（DCEMRI） for predicting tumor response to radiotherapy in patients with suspected primary central nervous system（CNS） germ cell tumors（GCTs）.Methods： DCE-MRI parameters of 35 patients with suspected primary CNS GCTs were obtained prior to diagnostic radiation, using the Tofts and Kermode model. Radiosensitivity was determined in tumors diagnosed 2 weeks after radiation by observing changes in tumor size and markers as a response to MRI. Taking radiosensitivity as the gold standard, the cut-off value of DCE-MRI parameters was measured by receiver operating characteristic（ROC） curve. Diagnostic accuracy of DCE-MRI parameters for predicting radiosensitivity was evaluated by ROC curve.Results： A significant elevation in transfer constant（K^trans） and extravascular extracellular space（Ve）（P=0.000）, as well as a significant reduction in rate constant（Kep）（P=0.000） was observed in tumors. K^trans, relative K^trans, and relative Kep of the responsive group were significantly higher than non-responsive groups. No significant difference was found in Kep, Ve, and relative Ve between the two groups. Relative K^trans showed the best diagnostic value in predicting radiosensitivity with a sensitivity of 100%, specificity of 91.7%, positive predictive value（PPV） of 95.8%, and negative predictive value（NPV） of 100%.Conclusions： Relative K^trans appeared promising in predicting tumor response to radiation therapy（RT）. It is implied that DCE-MRI pre-treatment is a requisite step in diagnostic procedures and a novel and reliable approach to guide clinical choice of RT.

Evaluation of tumor response to antiangiogenic therapy in patients with recurrent gliomas using contrast-enhanced perfusion-weighted magnetic resonance imaging techniques:A meta-analysis

BACKGROUND It is of vital importance to find radiologic biomarkers that can accurately predict treatment response. Usually, the initiation of antiangiogenic therapy causes a rapid decrease in the contrast enhancing tumor. However, the treatment response is observed only in a fraction of patients due to the partial radiological response secondary to stabilization of abnormal vessels which does not essentially indicate a true antitumor effect. Perfusion-weighted magnetic resonance imaging(PWMRI) techniques have shown implicitness as a strong imaging biomarker for gliomas since they give hemodynamic information of blood vessels. Hence, there is a rapid expansion of PW-MRI related studies and clinical applications.AIM To determine the diagnostic performance of PW-MRI techniques including:(A)dynamic contrast-enhanced magnetic resonance imaging(DCE-MRI); and(B)dynamic susceptibility contrast magnetic resonance imaging(DSC-MRI) for evaluating response to antiangiogenic therapy in patients with recurrent gliomas.METHODS Databases such as PubMed(MEDLINE included), EMBASE, and Google Scholar were searched for relevant original articles. The included studies were assessed for methodological quality with the Quality Assessment of Diagnostic Accuracy Studies 2 tool. Medical imaging follow-up or histopathological analysis was used as the reference standard. The data were extracted by two reviewers independently, and then the sensitivity, specificity, summary receiver operating characteristic curve, area under the curve(AUC), and heterogeneity were calculated using Meta-Disc 1.4 software.RESULTS This study analyzed a total of six articles. The overall sensitivity for DCE-MRI and DSC-MRI was 0.69 [95% confidence interval(CI): 0.53-0.82], and the specificity was 0.99(95%CI: 0.93-1) by a random effects model(DerSimonianeeLaird model). The likelihood ratio(LR) +, LR-, and diagnostic odds ratio(DOR)were 12.84(4.54-36.28), 0.35(0.22-0.53), and 24.44(7.19-83.06), respectively. The AUC(± SE) was 0.9921(± 0.0120), and the Q* index(± SE) was 0.9640(± 0.0323).For DSC-MRI, the sensitivity was 0.73, the specificity was 0.98, the LR+ was 7.82,the LR-was 0.32, the DOR was 31.65, the AUC(± SE) was 0.9925(± 0.0132), and the Q* index was 0.9649(± 0.0363). For DCE-MRI, the sensitivity was 0.41, the specificity was 0.97, the LR+ was 5.34, the LR-was 0.71, the DOR was 8.76, the AUC(± SE) was 0.9922(± 0.2218), and the Q* index was 0.8935(± 0.3037).CONCLUSION This meta-analysis demonstrated a beneficial value of PW-MRI(DSC-MRI and DCE-MRI) in monitoring the response of recurrent gliomas to antiangiogenic therapy, with reasonable sensitivity, specificity, +LR, and-LR.

Gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acidenhanced magnetic resonance imaging for evaluating fibrosis regression in chronic hepatitis C patients after direct-acting antiviral

BACKGROUND Direct acting antiviral(DAA)therapy has enabled hepatitis C virus infection to become curable,while histological changes remain uncontained.Few valid noninvasive methods can be confirmed for use in surveillance.Gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid(Gd-EOB-DTPA)is a liver-specific magnetic resonance imaging(MRI)contrast,related to liver function in the hepatobiliary phase(HBP).Whether Gd-EOB-DTPA-enhanced MRI can be used in the diagnosis and follow up of hepatic fibrosis in patients with chronic hepatitis C(CHC)has not been investigated.AIM To investigate the diagnostic and follow-up values of Gd-EOB-DTPA-enhanced MRI for hepatic histology in patients with CHC.METHODS Patients with CHC were invited to undergo Gd-EOB-DTPA-enhanced MRI and liver biopsy before treatment,and those with paired qualified MRI and liver biopsy specimens were included.Transient elastography(TE)and blood tests were also arranged.Patients treated with DAAs who achieved 24-wk sustained virological response(SVR)underwent Gd-EOB-DTPA-enhanced MRI and liver biopsy again.The signal intensity(SI)of the liver and muscle were measured in the unenhanced phase(UEP)(SI_(UEP-liver),SI_(UEP-muscle))and HBP(SI_(HBP-liver),SI_(HBP-muscle))via MRI.The contrast enhancement index(CEI)was calculated as[(SI_(HBP-liver)/SI_(HBP-muscle))]/[(SI_(UEP-liver)/SI_(UEP-muscle))].Liver stiffness measurement(LSM)was confirmed with TE.Serologic markers,aspartate aminotransferase-to-platelet ratio index(APRI)and Fibrosis-4(FIB-4),were also calculated according to blood tests.The grade of inflammation and stage of fibrosis were evaluated with the modified histology activity index(mHAI)and Ishak fibrosis score,respectively.Fibrosis regression was defined as a≥1-point decrease in the Ishak fibrosis score.The correlation between the CEI and liver pathology was evaluated.The diagnostic and follow-up values of the CEI,LSM,and serologic markers were compared.RESULTS Thirty-nine patients with CHC were enrolled[average age,42.3±14.4 years;20/39(51.3%)male].Twenty-one enrolled patients had eligible paired Gd-EOB-DTPA-enhanced MRI and liver tissues after achieving SVR.The mHAI median significantly decreased after SVR[baseline 6.0(4.5-13.5)vs SVR 2.0(1.5-5.5),Z=3.322,P=0.017],but the median stage of fibrosis did not notably change(P>0.05).Sixty pairs of qualified MRI and liver tissue samples were available for use to analyze the relationship between the CEI and hepatic pathology.The CEI was negatively correlated with the mHAI(r=-0.56,P<0.001)and Ishak score(r=-0.69,P<0.001).Further stratified analysis showed that the value of the CEI decreased with the progression of the stage of fibrosis rather than with the grade of necroinflammation.For patients with Ishak score≥5,the areas under receiver operating characteristics curve of the CEI,LSM,APRI,and FIB-4 were approximately at baseline,0.87–0.93,and after achieving SVR,0.83–0.91.The CEI cut-off value was stable(baseline 1.58 and SVR 1.59),but those of the APRI(from 1.05 to 0.24),FIB-4(from 1.78 to 1.28),and LSM(from 10.8 kpa to 7.1 kpa)decreased dramatically.The APRI and FIB-4 cannot be used as diagnostic means for SVR in patients with Ishak score≥3(P>0.05).Seven patients achieved fibrosis regression after achieving SVR.In these patients,the CEI median increased(from 1.71 to 1.83,Z=-1.981,P=0.048)and those of the APRI(from 1.71 to 1.83,Z=-2.878,P=0.004)and LSM(from 6.6 to 4.8,Z=-2.366,P=0.018)decreased.However,in patients without fibrosis regression,the medians of the APRI,FIB-4,and LSM also changed significantly(P<0.05).CONCLUSION Gd-EOB-DTPA-enhanced MRI has good diagnostic value for staging fibrosis in patients with CHC.It can be used for fibrotic-change monitoring post SVR in patients with CHC treated with DAAs.

Cerebral blood flow volume measurements of the carotid artery and ipsilateral branches using two-dimensional phase-contrast magnetic resonance angiography

The optimal velocity encoding of phase-contrast magnetic resonance angiography （PC MRA） in measuring cerebral blood flow volume （BFV） ranges from 60 to 80 cm/s. To verify the accuracy of two-dimensional （2D） PC MRA, the present study localized the region of interest at blood vessels of the neck using PC MRA based on three-dimensional time-of-flight sequences, and the velocity encoding was set to 80 cm/s. Results of the measurements showed that the error rate was 7.0±6.0% in the estimation of BFV in the internal carotid artery, the external carotid artery and the ipsilateral common carotid artery. There was no significant difference, and a significant correlation in BFV between internal carotid artery ＋ external carotid artery and ipsilateral common carotid artery. In addition, the BFV of the common carotid artery was correlated with that of the ipsilateral internal carotid artery. The main error was attributed to the external carotid artery and its branches. Therefore, after selecting the appropriate scanning parameters and protocols, 2D PC MRA is more accurate in the determination of BFV in the carotid arteries.

Role of pulmonary perfusion magnetic resonance imaging for the diagnosis of pulmonary hypertension:A review

Among five types of pulmonary hypertension,chronic thromboembolic pulmonary hypertension(CTEPH)is the only curable form,but prompt and accurate diagnosis can be challenging.Computed tomography and nuclear medicine-based techniques are standard imaging modalities to non-invasively diagnose CTEPH,however these are limited by radiation exposure,subjective qualitative bias,and lack of cardiac functional assessment.This review aims to assess the methodology,diagnostic accuracy of pulmonary perfusion imaging in the current literature and discuss its advantages,limitations and future research scope.

RETROSPECTIVE ANALYSIS OF MAGNETIC RESONANCE MYOCARDIAL DELAYED ENHANCEMENT

Objective To explore the imaging and related clinical characteristics of magnetic resonance （MR） delayed enhancement in patients with ischemic or nonischemic heart disease. Methods Thirty-two cases who underwent MR myocardial cine and delayed enhancement imaging from January 2004 to October 2006 were retrospectively analyzed. The cine sequence imaging included the four-chamber view and the left ventricular short axis view. The delayed enhancement imaging was taken 10 minutes after the infusion of gadolinium from the antecubital vein with a segmented inversion-recovery-prepared Tl-weighted fast gradient echo sequence. Patients underwent coronary computed tomography angiography （CTA） two weeks before or after the MR imaging examination. Combined with clinical history, the clinical and MR imaging characteristics of the patients who had delayed enhancement were analyzed. Results MR delayed enhancement could be found in 16 cases. Among them, 12 cases had ischemic heart disease. Their coronary CTA showed one to three vessel diseases. The delayed enhancement was transmural or subendocardium, and the area of delayed enhancement corresponded well with one or more coronary arteries which had severe stenosis or occlusion. Four cases had nonischemic heart diseases One case was dilated cardiomyopathy, with diffuse small midwall spots in delayed enhancemen and only 30% stenosis of the anterior descending coronary artery in coronary CTA. One case was hypertrophic cardiomyopathy, with delayed enhancement of strip- and patch-shaped at midwall of the hypertrophic myocardiurn. One case was restrictive cardiomyopathy, and the delayed enhancement was located in the area of subendocardium of both the right and left ventricles. Coronary CTA of these two cases were normal The other case was a mass of the lateral wall of the left ventricle, and the delayed enhancement with a clumpy shape was located in the lateral wall of the left ventricle. Conclusions MR myocardial delayed enhancement is not a specific sign of myocardial infarction of ischemic heart disease. Nonischemic heart diseases including all kinds of primary cardiomyopathy and some other diseases affecting myocardium can also cause delayed enhancement, but their characteristics are different. The differentiation of the etiology of the nonischemic heart disease with delayed enhancement relies upon the intimate connection with clinical history and the cine sequence MR images.

More Peripheral Visualization of Hepatic Arteries by Using Respiratory-Triggered 3D True Steady-State Free-Precession Projection Magnetic Resonance Angiographic Sequences with Time-Spatial Labeling Inversion Pulse

Purpose: To evaluate respiratory-triggered three-dimensional (3D) true steady-state free-precession (SSFP) projection magnetic resonance angiographic sequences with time-spatial labeling inversion pulse (Time-SLIP) for visualizing the hepatic arteries and to optimize the image acquisition protocol. Materials and Methods: A 1.5-T clinical magnetic resonance imager was used to perform abdominal magnetic resonance angiography (MRA) in 25 consecutive patients before transcatheter arterial chemoembolization or surgery. We compared two selective space-labeling inversion pulse (tag pulse) patterns (Patterns I and II, oblique and parallel tag pulses, respectively). Two experienced radiologists evaluated the number of hepatic arterial branches visible on the acquired MRA images, and the results were referenced with those on images from intra-arterial digital subtraction angiography. Results: Images were acquired from all patients. The two radiologists clearly visualized branches of the left and right hepatic arteries. More peripheral hepatic arterial branches were identified in MRA images captured by using tag pulse Pattern I than in those acquired by using Pattern II (P P > 0.05). Conclusion: Non-contrast-enhanced Time-SLIP hepatic MRA with true SSFP allowed selective visualization of peripheral hepatic vessels.

In vivo tracking of human adipose-derived stem cells labeled with ferumoxytol in rats with middle cerebral artery occlusion by magnetic resonance imaging

Ferumoxytol, an iron replacement product, is a new type of superparamagnetic iron oxide ap- proved by the US Food and Drug Administration. Herein, we assessed the feasibility of tracking transplanted human adipose-derived stem cells labeled with ferumoxytol in middle cerebral artery occlusion-injured rats by 3.0 T MRI in vivo. 1 × 104 human adipose-derived stem cells labeled with ferumoxytol-heparin-protamine were transplanted into the brains of rats with middle cerebral artery occlusion. Neurologic impairment was scored at 1, 7, 14, and 28 days after transplantation. T2-weighted imaging and enhanced susceptibility-weighted angiography were used to observe transplanted cells. Results of imaging tests were compared with results of Prussian blue staining. The modified neurologic impairment scores were significantly lower in rats transplanted with cells at all time points except I day post-transplantation compared with rats without transplantation. Regions with hypointense signals on T2-weighted and enhanced susceptibility-weighted angiography images corresponded with areas stained by Prussian blue, suggesting the presence of superparamagnetic iron oxide particles within the engrafted cells. Enhanced susceptibility-weighted angiography image exhibited better sensitivity and contrast in tracing ferumoxytol-heparin-protamine-labeled human adipose-derived stem ceils compared with T2-weighted imaging in routine MRI.

Intraoperative perfusion magnetic resonance imaging: Cutting-edge improvement in neurosurgical procedures

The goal in brain tumor surgery is to remove the maxi-mum achievable amount of the tumor, preventing damage to "eloquent" brain regions as the amount of brain tumor resection is one of the prognostic factors for time to tumor progression and median survival. To achieve this goal, a variety of technical advances have been in-troduced, including an operating microscope in the late 1950 s, computer-assisted devices for surgical navigation and more recently, intraoperative imaging to incorporate and correct for brain shift during the resection of the lesion. However, surgically induced contrast enhancement along the rim of the resection cavity hampers interpretation of these intraoperatively acquired magnetic resonance images. To overcome this uncertainty, perfusion techniques [dynamic contrast enhanced magnetic resonance imaging(DCE-MRI), dynamic susceptibility contrast magnetic resonance imaging(DSC-MRI)] have been introduced that can differentiate residual tumor from surgically induced changes at the rim of the resec-tion cavity and thus overcome this remaining uncer-tainty of intraoperative MRI in high grade brain tumor resection.

Clinical applications of advanced magnetic resonance imaging techniques for arthritis evaluation

Magnetic resonance imaging(MRI) has allowed a comprehensive evaluation of articular disease, increasing the detection of early cartilage involvement, bone erosions, and edema in soft tissue and bone marrow compared to other imaging techniques. In the era of functional imaging, new advanced MRI sequences are being successfully applied for articular evaluation in cases of inflammatory, infectious, and degenerative arthropathies. Diffusion weighted imaging, new fat suppression techniques such as DIXON, dynamic contrast enhanced-MRI, and specific T2 mapping cartilage sequences allow a better understanding of the physiopathological processes that underlie these different arthropathies. They provide valuable quantitative information that aids in their differentiation and can be used as potential biomarkers of articular disease course and treatment response.

Perfusion magnetic resonance imaging of the liver

Perfusion magnetic resonance imaging (MRI) studies quantify the microcirculatory status of liver parenchyma and liver lesions, and can be used for the detection of liver metastases, assessing the effectiveness of antiangiogenic therapy, evaluating tumor viability after anticancer therapy or ablation, and diagnosis of liver cirrhosis and its severity. In this review, we discuss the basic concepts of perfusion MRI using tracer kinetic modeling, the common kinetic models applied for analyses, the MR scanning techniques, methods of data processing, and evidence that supports its use from published clinical and research studies. Technical standardization and further studies will help to establish and validate perfusion MRI as a clinical imaging modality.

Pulmonary Sequestration: Three Dimensional Dynamic Contrast-enhanced MR Angiography and MRI

In order to evaluate the diagnostic value of three dimentional contrast enhanced MR angiography and MRI for pulmonary sequestration, 5 patients with pulmonary sequestration underwent 3D fast imaging by steady state precession (FISP) with a contrast medium and breath holding following chest radiography, CT and MR scans. The reconstructed MR angiography was performed using maximum intensity projection (MIP) and multiplanar reconstruction (MPR) techniques. It was found that the chest radiography showed pulmonary sequestration as a persistent area of opacity in the posterior basal segment of the left lower lobe, which was close to mediastinum in 2 cases and close to diaphragma in 3 cases. CT revealed a soft issue mass beyond descending aorta and lobar emphysema around the pulmonary sequestration. And the supplying vessel was documented in 2 cases on enhanced CT. MRI demonstrated a hyperintensity mass with respect to normal lung parenchyma on T1WI and T2WI, and the origin of the supplying vessel in 3 cases. The reconstructed CE MRA using MIP or MRP techniques clearly showed the supplying vessel and its course, branches as well as draining vessels. It was concluded that 3D CE MRA of demonstrating the supplying and draining vessels to pulmonary sequestration, together with plain MRI, can provide a diagnosis and aid in surgical planning without the need for DSA.