Reliability of magnetic resonance elastography using multislice two-dimensional spin-echo echo-planar imaging (SE-EPI) and three-dimensional inversion reconstruction for assessing renal stiffness.

BACKGROUND: To evaluate the reliability of MRE using a spin-echo echo-planar imaging (SE-EPI) renal MRE technique in healthy volunteers. METHODS: Institutional review board approved prospective study in which all participants provided written informed consent. Sixteen healthy volunteers comprising seven males and nine females with a median age of 35 years (age range: 23 to 59 years) were included. Coronal 90 Hz and 60 Hz MRE acquisitions were performed twice within a 30-min interval between examinations. Renal MRE reliability was assessed by (i) test-retest repeatability, and (ii) inter-rater agreement between two independent readers. The MRE-measured averaged renal stiffness values were evaluated using: intraclass correlation coefficient (ICC), Bland-Altman and the within-subject coefficient of variation (COV). RESULTS: For test-retest repeatability, Bland-Altman showed a mean stiffness difference between examinations of 0.07 kPa (95% limits of agreement: -1.41, 1.54) at 90 Hz and 0.01 kPa (95% limits of agreement: -0.51, 0.53) at 60 Hz. Coefficient of repeatability was 1.47 kPa and 0.52 kPa at 90 Hz and 60 Hz, respectively. The within-subject COV was 13.6% and 7.7% at 90 Hz and 60 Hz, respectively. ICC values were 0.922 and 0.907 for test-retest repeatability and 0.998 and 0.989 for inter-rater agreement, respectively (P < 0.001). CONCLUSION: SE-EPI renal MRE is a reliable technique.

Magnetic resonance elastography in the detection of hepatorenal syndrome in patients with cirrhosis and ascites.

OBJECTIVE: Hepatorenal syndrome (HRS) is the most lethal cause of renal impairment in cirrhosis. Magnetic resonance elastography (MRE) is a diagnostic test that characterises tissues based on their biomechanical properties. The aim of this study was to assess the feasibility of MRE for detecting HRS in cirrhotic patients. METHODS: A prospective diagnostic investigation was performed. Renal MRE was performed on 21 hospitalised patients with cirrhosis and ascites. Six patients had HRS, one patient had non-HRS renal impairment, and 14 patients had normal renal function. The MRE-measured renal stiffness was compared against the clinical diagnosis as determined by clinical review alongside laboratory and radiologic results. RESULTS: The MRE-measured renal stiffness was significantly lower in patients with HRS (median stiffness of 3.30 kPa at 90 Hz and 2.62 kPa at 60 Hz) compared with patients with normal renal function (median stiffness of 5.08 kPa at 90 Hz and 3.41 kPa at 60 Hz) (P ≤ 0.014). For the detection of HRS, MRE had an area under the receiver operating characteristic curve of 0.94 at 90 Hz and 0.89 at 60 Hz. MRE had excellent inter-rater agreement, as assessed by Bland-Altman and intraclass correlation coefficient (> 0.9). CONCLUSION: MRE shows potential in the detection of HRS. KEY POINTS: • Magnetic resonance elastography (MRE) shows promise in the detection of hepatorenal syndrome. • MRE has the potential to track renal disease in a clinical population. • MRE is a reliable diagnostic test with excellent inter-rater agreement.

Interactive neonatal gastrointestinal magnetic resonance imaging using fruit juice as an oral contrast media.

BACKGROUND: The objective was to evaluate the use of fruit juice with an interactive inversion recovery (IR) MR pulse sequence to visualise the gastrointestinal tract. METHODS: We investigated the relaxation properties of 12 different natural fruit juices in vitro, to identify which could be used as oral contrast. We then describe our initial experience using an interactive MR pulse sequence to allow optimal visualisation after administering pineapple juice orally, and suppressing pre-existing bowel fluid contents, with variable TI in three adult and one child volunteer. RESULTS: Pineapple juice (PJ) had both the shortest T1 (243 ms) and shortest T2 (48 ms) of the fruit juices tested. Optimal signal differentiation between pre-existing bowel contents and oral PJ administration was obtained with TIs of between 900 and 1100 ms. CONCLUSION: The use of an inversion recovery preparation allowed long T1 pre-existing bowel contents to be suppressed whilst the short T1 of fruit juice acts as a positive contrast medium. Pineapple juice could be used as oral contrast agent for neonatal gastrointestinal magnetic resonance imaging.

Initial clinical evaluation of a non-contrast-enhanced MR angiography method in the distal lower extremities.

PURPOSE: To report the initial experience and diagnostic performance applying a novel flow-dependent non-contrast-enhanced MR angiography (NCE-MRA) method, in patients with suspected peripheral vascular disease, in comparison with established contrast-enhanced MRA (CE-MRA). METHODS: The lower legs of 34 patients were imaged at 1.5 T with both NCE-MRA and CE-MRA. The NCE-MRA method consisted of a cardiac-gated balanced-SSFP sequence with controllable flow-suppression preparation. Flow-suppressed and unsuppressed datasets were subtracted to obtain angiograms. Two experienced radiologists assessed both NCE-MRA and CE-MRA images, first independently and then in consensus to resolve significant disagreements. Signal loss, vessel conspicuity, vascular disease, venous contamination, artifacts, and diagnostic confidence were assessed. RESULTS: Using the CE-MRA as the "gold standard," the per-segment sensitivity and specificity for detection of significant disease were 81.7% and 90.9%, respectively. Mean diagnostic confidence (scale 0-4) was 3.4 for NCE-MRA and 3.9 for CE-MRA. Most vessel segments were well visualized but the popliteal arteries often suffered some technique-related signal loss. CONCLUSIONS: The NCE-MRA method was able to visualize most vessel segments with good or excellent confidence, few artifacts, and excellent background suppression, giving moderate agreement with CE-MRA. However, some segments were poorly visualized, probably due to flow profile distortion in these patients.

Evaluation of depth of myometrial invasion and overall staging in endometrial cancer: comparison of diffusion-weighted and dynamic contrast-enhanced MR imaging.

PURPOSE: To compare the diagnostic performance of diffusion-weighted (DW) magnetic resonance (MR) imaging with that of dynamic contrast material-enhanced (DCE) MR imaging in evaluating the depth of myometrial invasion and overall stage in patients with endometrial cancer. MATERIALS AND METHODS: The institutional review board approved this retrospective study; patient consent was not required. From May 2008 to February 2010, 48 women with endometrial cancer underwent preoperative MR imaging, including T1- and T2-weighted imaging, DW MR imaging (b=0 and 800 sec/mm2) and DCE MR imaging. Two radiologists independently interpreted the depth of myometrial invasion, overall stage, and presence of pitfalls associated with inaccurate assessment of myometrial invasion at T1- and T2-weighted imaging, DW MR imaging, and DCE MR imaging. Myometrial invasion and overall stage were compared by using the McNemar test, and κ statistics were used for reader agreement. RESULTS: For assessing the depth of myometrial invasion, diagnostic accuracy, sensitivity, and specificity, respectively, were as follows: DW MR imaging-reader 1, 90%, 84%, and 100%; reader 2, 85%, 84%, and 88%; DCE MR imaging-reader 1, 71%, 61%, and 88%; reader 2, 79%, 77%, and 82%. The improvement in diagnostic accuracy for reader 1 was significant (P=.035). For myometrial invasion, κ values were 0.75 with DW MR imaging and 0.26 with DCE MR imaging. There was no association between inaccurate assessment of myometrial invasion and standard pitfalls with DW MR imaging. Readers 1 and 2 correctly staged more patients by using DW MR imaging (39 and 38 patients, respectively) than by using DCE MR imaging (29 and 30 patients, respectively) (P<.05). For overall stage, κ values were 0.74 with DW MR imaging and 0.22 with DCE MR imaging. CONCLUSION: DW MR imaging has superior diagnostic accuracy in the assessment of myometrial invasion and significantly higher staging accuracy compared with DCE MR imaging.

Advanced ovarian cancer: multiparametric MR imaging demonstrates response- and metastasis-specific effects.

PURPOSE: To investigate the role of multiparametric magnetic resonance (MR) imaging in the evaluation of response to platinum-based neoadjuvant chemotherapy in advanced ovarian cancer and to compare imaging parameters between primary ovarian mass and metastatic disease. MATERIALS AND METHODS: Evaluable patients suspected of having advanced ovarian carcinoma were enrolled in a prospective protocol-driven study. Research ethics committee approval and written informed consent were obtained. Multiparametric MR imaging (diffusion-weighted MR imaging, dynamic contrast material-enhanced [DCE] MR imaging, and hydrogen 1 MR spectroscopy) was performed with a 3.0-T wholebody MR imaging system. Three marker lesions-primary ovarian mass, omental cake, and peritoneal deposit-were outlined by a radiologist on apparent diffusion coefficient (ADC) and vascular signal fraction (VSF) maps and on DCE MR images. Comparisons of mean ADC, mean VSF, DCE MR imaging parameters, and choline concentration between responders and nonresponders were based on Response Evaluation Criteria in Solid Tumors and CA-125 criteria. RESULTS: Twenty-two patients were evaluable. The mean ADC for peritoneal metastases was lower than that for ovarian (P = .015) and omental (P = .006) sites. There were no differences in pretreatment DCE MR imaging parameters between tumor sites. After treatment, responders showed a significantly larger increase in ADC (P = .021) and fractional volume of the extravascular extracellular space (v(e)) (P = .025) of ovarian lesions compared with nonresponders, but there was no change in ADC at other sites. Pre- and posttreatment values of choline concentration of ovarian lesions were lower in responders (P = .025) than in nonresponders (P = .010). CONCLUSION: The significant differences in baseline ADCs among primary ovarian cancer, omental cake, and peritoneal deposits indicate that diffusivity profiles may be tumor-site dependent, suggesting biologic heterogeneity of disease. ADC and v(e) parameters correlated with the cytotoxic effects of platinum-based therapy and may be useful response markers, while choline concentration predicted but did not reflect response.

Repeatability of edited lactate and other metabolites in astrocytoma at 3T.

PURPOSE: To assess the repeatability of measurement of lactate and other metabolites in tumors using magnetic resonance spectroscopy (MRS). MATERIALS AND METHODS: MRS with spectral editing for lactate was performed on 10 patients with astrocytoma (two Grade III, eight Grade IV) using an 8-channel receive coil at 3T. Lactate, lipid, choline, creatine, and N-acetyl aspartate (NAA) signals were measured in regions of tumor and contralateral white matter. Metabolites were quantified relative to unsuppressed water using LCModel fitting software. RESULTS: The within-patient coefficients of variation were ≈16% (tumor lactate), 6%-8% (tumor choline and contralateral choline, creatine, and NAA), and 22% (tumor lipid). As expected due to their low concentration in normal tissue, lactate and lipid were not reliably detected in white matter but were found at high levels in most tumors. NAA and creatine were lower in tumors than in normal white matter, and choline varied between above- and below-normal values. No consistent short-term variation in metabolite levels was observed, despite differences in the time elapsed since administration of contrast agent. CONCLUSION: MRS appears repeatable enough to provide longitudinal measures of metabolite content in tumors and contralateral tissue in the brain in vivo.

A comparison of MR elastography and 31P MR spectroscopy with histological staging of liver fibrosis.

OBJECTIVES: Conventional imaging techniques are insensitive to liver fibrosis. This study assesses the diagnostic accuracy of MR elastography (MRE) stiffness values and the ratio of phosphomonoesters (PME)/phosphodiesters (PDE) measured using (31)P spectroscopy against histological fibrosis staging. METHODS: The local research ethics committee approved this prospective, blinded study. A total of 77 consecutive patients (55 male, aged 49 ± 11.5 years) with a clinical suspicion of liver fibrosis underwent an MR examination with a liver biopsy later the same day. Patients underwent MRE and (31)P spectroscopy on a 1.5 T whole body system. The liver biopsies were staged using an Ishak score for chronic hepatitis or a modified NAS fibrosis score for fatty liver disease. RESULTS: MRE increased with and was positively associated with fibrosis stage (Spearman's rank = 0.622, P < 0.001). PME/PDE was not associated with fibrosis stage (Spearman's rank = -0.041, p = 0.741). Area under receiver operating curves for MRE stiffness values were high (range 0.75-0.97). The diagnostic utility of PME/PDE was no better than chance (range 0.44-0.58). CONCLUSIONS: MRE-estimated liver stiffness increases with fibrosis stage and is able to dichotomise fibrosis stage groupings. We did not find a relationship between (31)P MR spectroscopy and fibrosis stage. KEY POINTS: Magnetic resonance elastography (MRE) and MR spectroscopy can both assess the liver. MRE is superior to ( 31 ) P MR spectroscopy in staging hepatic fibrosis. MRE is able to dichotomise liver fibrosis stage groupings. Gradient-echo MRE may be problematic in genetic haemochromatosis.

Prostate cancer metabolite quantification relative to water in 1H-MRSI in vivo at 3 Tesla.

(1)H magnetic resonance spectroscopic imaging was performed on 16 men with suspected prostate cancer using an 8-channel external receive coil at 3 T. Choline and citrate (Cit) signals were measured in prostate lesions and normal-appearing peripheral zone as identified on T(2)-weighted images. Metabolites were quantified relative to unsuppressed water from a separately acquired magnetic resonance spectroscopic imaging dataset using LCModel. Validation experiments were also performed in a phantom containing physiological concentrations of choline, Cit, and creatine. In vitro, fair agreement between measured and true concentrations was observed, with the greatest discrepancy being a 35% underestimation of Cit. In vivo, one dataset was rejected for failure to meet the quality criterion of linewidth <15 Hz, and in 6 of 15 subjects, insufficient normal-appearing peripheral zone tissue was identified for study. Lesions were found to have higher choline and choline/Cit, and lower Cit, than normal-appearing peripheral zone. The smaller skew of data obtained using water normalization in comparison with metabolite ratios suggests potential usefulness in longitudinal tumor monitoring and in studies of treatment effects.

Interactive magnetic resonance voiding cystourethrography (iMRVC) for vesicoureteric reflux (VUR) in unsedated infants: a feasibility study.

OBJECTIVES: The current reference standard for diagnosing vesicoureteric reflux is the X-ray-based Micturating CystoUrethroGram (MCUG). The aim of this study was to evaluate the feasibility of performing interactive Magnetic Resonance voiding cysto-urethrography (iMRVC) in un-sedated infants. METHODS: Twelve infants underwent conventional single-cycle MCUG followed by iMRVC. In iMRVC, patients were examined using an in-house developed fluoroscopic pulse sequence, which allows on-the-fly control of image contrast and geometry. A single acquisition was performed during bladder filling, during and after micturition, with interactive control over imaging parameters. Images were assessed for diagnostic quality and presence of VUR. RESULTS: Every case of reflux identified with MCUG was identified on iMRVC (100% sensitivity). Over 24 renal units, there was 88% concordance (21/24) according to the presence of reflux between the two methods. There were three "false positives" detected by MRI, giving a specificity of 83.3%, PPV of 66.7% and NPV of 100%. CONCLUSION: iMRVC is a feasible method for evaluating the renal tract in infants without the need for radiation or sedation. A formal evaluation is required to establish its diagnostic potential.

Dynamic contrast-enhanced MRI in ovarian cancer: Initial experience at 3 tesla in primary and metastatic disease.

The aim of this study was to develop and demonstrate a methodology for dynamic contrast-enhanced MRI at 3 T in patients with advanced ovarian cancer and to report the results from pharmacokinetic modeling of the data. Nineteen patients with suspected advanced ovarian carcinoma (FIGO stage 3 or higher) were enrolled in this prospective study. Up to three marker lesions were identified: primary ovarian mass, omental ''cake'', and peritoneal deposits. Dynamic contrast-enhanced MRI was performed using a three-dimensional T(1)-weighted gradient-echo acquisition with a temporal resolution of 1.6 sec, following intravenous administration of 0.1 mmol/kg gadobutrol. Precontrast T(1) mapping, using an inversion-recovery fast gradient-echo sequence, was also performed. Imaging was completed in 18/19 patients, although two were subsequently excluded based on pathology results. Pharmacokinetic modeling of the data was performed according to the extended Kety model, using an arterial input function formed by concatenation of the Fritz-Hansen and Weinmann curves. No statistically significant differences were found between the results for the three marker lesions. In the future, this work will allow kinetic modeling results from ovarian dynamic contrast-enhanced MRI to be correlated with response to treatment. The high temporal resolution allows good characterization of the rapid contrast agent uptake in these vascular tumors.

Apparent diffusion coefficient and vascular signal fraction measurements with magnetic resonance imaging: feasibility in metastatic ovarian cancer at 3 Tesla: technical development.

This prospective study aims to evaluate the feasibility of DWI at 3 Tesla in patients with advanced ovarian cancer and investigate the differences in vascular signal fraction (VSF) and apparent diffusion coefficient (ADC) values between primary ovarian mass and metastatic disease. Twenty patients with suspected advanced ovarian carcinoma were enrolled in the study. High-resolution T2W FRFSE images were used to confirm the position of three marker lesions: primary ovarian mass, omental cake and peritoneal deposit. Multislice DWI was acquired in a single breath-hold using multiple b-values. The three marker lesions were outlined by an experienced radiologist on ADC and VSF maps. Ovarian lesions showed the highest ADC values. The mean ADC value for peritoneal deposits was significantly lower than for both ovarian lesions (p = 0.03) and omental cake (p = 0.03). The VSF for omental cake was significantly higher than for ovarian lesions (p = 0.01) and peritoneal deposits (p = 0.04). There was a significant positive correlation between ADC and VSF for peritoneal deposits (p = 0.04). DWI in advanced ovarian cancer is feasible at 3 T. There are significant differences in baseline ADC and VSF values between ovarian cancer, omental cake and peritoneal deposits that may explain the mixed treatment response that occurs at different disease sites.

MR elastography: Spleen stiffness measurements in healthy volunteers--preliminary experience.

OBJECTIVE: The purpose of this article is to establish the range of normal splenic stiffness in healthy volunteers using MR elastography (MRE) and to investigate any correlation with physiologic parameters and driver position. SUBJECTS AND METHODS: Sixteen volunteers (mean [+/- SD] age, 37 +/- 9 years) with no history of gastrointestinal, hepatobiliary, or cardiovascular disease were recruited. The MRI protocol included T2-weighted axial and gradient-echo MRE sequences using steady-state 60-Hz excitation. Two MRE acquisitions were performed, one with the driver placed on the right side of the abdomen and the other with the driver placed on the left side. Volunteers' body mass index (BMI), arterial mean blood pressure, age, spleen volume, and liver stiffness were also determined. Two radiologists independently measured the spleen stiffness on the MRE inversion images. The correlations between spleen stiffness and BMI, arterial mean blood pressure, age, spleen volume, and liver stiffness were quantified. RESULTS: Sixteen volunteers underwent MRE. With the driver placed on the right side of the abdomen, the mean splenic stiffness was 3,565 +/- 586 Pa (range, 2,353-4,442 Pa); with the driver on the left side of the abdomen, the mean splenic stiffness was significantly (p < 0.004) different (4,255 +/- 625 Pa; range, 3,194-5,581 Pa). No significant correlation was found between spleen stiffness and BMI, arterial mean blood pressure, age, spleen volume, and liver stiffness (all p > 0.05) CONCLUSION: These preliminary results in a small number of healthy volunteers show that spleen stiffness is not significantly correlated with BMI, arterial mean blood pressure, spleen volume, or liver stiffness. A significant difference was observed using different driver positions.

Metabolic characterization of primary and metastatic ovarian cancer by 1H-MRS in vivo at 3T.

(1)H-MRS was performed on 12 women (age range 45-72) with ovarian cancer of FIGO stage 3 or above using a 3T MRI system with an 8-channel cardiac receive coil. Respiratory-triggered PRESS-localized spectra (TE = 144 ms) were obtained separately from an ovarian mass and from metastatic disease. Peak areas were quantified relative to unsuppressed water using LCModel and spectra were discarded if LCModel reported signal-to-noise ratio (SNR) < 3 or if no metabolites were reported with standard deviation (SD) < 30%. The cystic fraction of each voxel was estimated by thresholding T(2)-weighted images, and this was used both to correct the reported metabolite concentrations and to calculate an expected SNR of choline using the measured SNR of water. Choline was detected in 10/12 primary tumors and 5/11 metastatic lesions (range 2.0-16.6 mM). Of the 8/23 failures, 7 had a predicted choline SNR < 2, confirming that the failure to detect choline could be explained by technical problems. Glycine was observed in one benign lesion. (1)H-MRS can be used to quantify choline in primary and metastatic masses in ovarian cancer, but the moderately high rate of failure to detect choline necessitates careful recording of data quality parameters to discriminate true from false negatives.

Added value of dynamic contrast-enhanced magnetic resonance imaging in predicting advanced stage disease in patients with endometrial carcinoma.

AIM: To assess the added value of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) in predicting advanced stage disease in patients with endometrial carcinoma. MATERIALS AND METHODS: Fifty patients with endometrial carcinoma underwent preoperative MRI assessment in a single gynecological cancer center during a 2-year period. Magnetic resonance imaging examinations included high-resolution sagittal, axial, and axial-oblique T2-weighted images (T2WI) of the pelvis, and axial T1-weighted images (T1WI) of the pelvis and upper abdomen followed by DCE-MRI using a multiphase 3-dimensional gradient refocused echo T1WI sequence. The T2W images were evaluated initially, and local and overall staging was assigned according to the FIGO classification. An identical scoring system was used to evaluate the combination of DCE-MRI and T2WI. The presence of potential pitfalls in the accurate assessment of depth of myometrial invasion (leiomyoma, adenomyosis, loss of junctional zone definition, polypoid tumor, poor tumor-to-myometrium contrast, and tumor extension to uterine cornu) was also recorded. Surgical histology constituted the standard of reference. RESULTS: The depth of myometrial invasion was correctly determined in 78% (39/50) of the cases on T2WI alone, increasing to 92% (46/50) with the addition of DCE-MRI (95% confidence interval for improvement, 4.4%-23.6%, P = 0.016). The addition of DCE-MRI led to the correct detection of deep myometrial invasion in all cases. Tumor extension to uterine cornu was the only variable significantly associated (P = 0.014) with incorrect estimation of depth of myometrial invasion. CONCLUSIONS: The addition of multiphase 3-dimensional DCE-MRI to T2WI can effectively assess the depth of myometrial invasion in endometrial carcinoma and may be a useful tool to guide the surgical approach.

Measuring carotid stenosis on contrast-enhanced magnetic resonance angiography: diagnostic performance and reproducibility of 3 different methods.

BACKGROUND AND PURPOSE: The aim of this study was to compare diagnostic performance and reproducibility of 3 different methods of quantifying stenosis on contrast-enhanced magnetic resonance angiography (CEMRA), with intra-arterial digital subtraction angiography (DSA) as the reference standard. METHODS: 167 symptomatic patients scheduled for DSA, after screening Doppler ultrasound, were prospectively recruited to undergo CEMRA. Severity of stenosis was measured according to the North American Symptomatic Trial Collaborators (NASCET), European Carotid Surgery Trial (ECST), and the common carotid (CC) methods. Measurements for each method were made for 284 vessels (142 included patients) on both CEMRA and DSA in a blinded and randomized manner by 3 independent attending neuroradiologists. RESULTS: Significant differences in prevalence of severe stenosis were seen with the 3 methods on both DSA and CEMRA, with ECST yielding the least and NASCET the most cases of severe stenosis. Overall, all 3 methods performed similarly well in terms of intermodality correlation and agreement. No significant differences in interobserver agreement were found on either modality. With CEMRA, however, we found a significantly lower sensitivity for detection of severe stenosis with ECST (79.8%) compared with NASCET (93.0%), with DSA as reference standard. CONCLUSIONS: Uniformity of carotid stenosis measurement methods is desirable because patient management may otherwise differ substantially. All 3 methods are adequate for use with DSA. With CEMRA, however, this study supports use of the NASCET method because of improved sensitivity for detecting severe stenosis.

In vivo detection of macrophages in human carotid atheroma: temporal dependence of ultrasmall superparamagnetic particles of iron oxide-enhanced MRI.

UNLABELLED: Background- It has been suggested that inflammatory cells within vulnerable plaques may be visualized by superparamagnetic iron oxide particle-enhanced MRI. The purpose of this study was to determine the time course for macrophage visualization with in vivo contrast-enhanced MRI using an ultrasmall superparamagnetic iron oxide (USPIO) agent in symptomatic human carotid disease. METHODS: Eight patients scheduled for carotid endarterectomy underwent multisequence MRI of the carotid bifurcation before and 24, 36, 48, and 72 hours after Sinerem (2.6 mg/kg) infusion. RESULTS: USPIO particles accumulated in macrophages in 7 of 8 patients given Sinerem. Areas of signal intensity reduction, corresponding to USPIO/macrophage-positive histological sections, were visualized in all 7 of these patients, optimally between 24 and 36 hours, decreasing after 48 hours, but still evident up to 96 hours after infusion. CONCLUSIONS: USPIO-enhanced MRI of carotid atheroma can be used to identify macrophages in vivo. The temporal change in the resultant signal intensity reduction on MRI suggests an optimal time window for the detection of macrophages on postinfusion imaging.

MRI without magnet removal in neurofibromatosis type 2 patients with cochlear and auditory brainstem implants.

OBJECTIVE: To assess the impact on image quality of MRI without magnet removal in cochlear implant (CI) and auditory brainstem implant (ABI) users with neurofibromatosis type 2 (NF2). STUDY DESIGN: Prospective cohort. SETTING: Tertiary center for cochlear and auditory brainstem implantation. PATIENTS: Thirteen patients (10 ABI, 3CI) with NF2 underwent a total of 76 MRI scans. INTERVENTIONS: MRI without magnet removal. MAIN OUTCOME MEASURE: Ability to visualize the ipsilateral and contralateral cerebellopontine angles (CPAs) and internal auditory meati (IAM) with head MRI. RESULTS: Of the 76 scans, 40 were of the head, 28 of the spine and 8 of other regions. Scanning was performed with a tight head bandage and plastic card. There were no cases of altered implant function or demagnetization of the device magnet.A grading system was used to assess the view of the ipsilateral IAM-CPA. In 85% of head scans, the view was unimpaired (Grade 0). In 13%, there was distortion (Grade 1). In 2% (1 case), the view was entirely obscured by artifact (Grade 2). Views of the contralateral CPA and IAM were unimpaired in all cases. The best 3 sequences for the depiction of the ipsilateral IAM-CPA (percent graded as 0) were as follows: axial 3D inversion recovery prepared fast spoiled gradient echo (100%), 2 mm coronal T1W of the IAM-CPA (88.9%), and 2 mm axial T1W of the IAM-CPA (76.9%). CONCLUSION: MRI scanning without magnet removal is safe and well tolerated in NF2 patients with auditory implants. With appropriate MRI sequences, the image quality is not significantly impaired.

Interactive magnetic resonance imaging for paediatric vesicoureteric reflux (VUR).

OBJECTIVES: The current gold standard for diagnosing vesicoureteric reflux in unsedated infants is the X-ray-based Micturating CystoUrethroGram (MCUG). The aim of this study was to assess the diagnostic performance of interactive MRI for voiding cysto-urethrography (iMRVC). METHODS: 25 infants underwent conventional MCUG followed by iMRVC. In iMRVC, patients were examined using a real-time MR technique, which allows interactive control of image contrast and imaging plane location, before, during and after micturition. Images were assessed for presence and grade of VUR. Parental feedback on both procedures was evaluated. RESULTS: iMRVC gave a sensitivity of 100%, specificity of 90.5% (95% CI: 81.6-99.4%), PPV of 66.7% and NPV of 100% in this population. There was 88% concordance (44/50 renal units) according to the presence of VUR between the two methods, with iMRVC up-grading VUR in 6 units (12%). There was very good agreement regarding VUR grade: Kappa=0.66±0.11 (95% CI 0.43-0.88). 60% of parents preferred the MRI, but did not score the two tests differently. CONCLUSION: Interactive MRI allows dynamic imaging of the whole urinary tract without ionising radiation exposure. iMRVC gives comparable results to the MCUG, and is acceptable to parents.

Validity of a new abdominal bioelectrical impedance device to measure abdominal and visceral fat: comparison with MRI.

Abdominal fat, and in particular, visceral adipose tissue (VAT), is the critical fat depot associated with metabolic aberrations. At present, VAT can only be accurately measured by computed tomography or magnetic resonance imaging (MRI). This study was designed to compare a new abdominal bioelectrical impedance (BIA) device against total abdominal adipose tissue (TAAT) and VAT area measurements made from an abdominal MRI scan, and to assess its reliability and accuracy. One-hundred twenty participants were recruited, stratified by gender and BMI. Participants had triplicate measures of abdominal fat and waist circumference (WC) with the AB-140 (Tanita, Tokyo, Japan) and WC measurements using a manual tape measure. A single abdominal MRI scan was performed as the reference method. Triplicate measures with the AB-140 showed excellent precision for "visceral fat level," trunk fat %, and WC. AB-140 "visceral fat level" showed significantly stronger correlations with MRI TAAT area than with MRI VAT area (r = 0.94 vs. 0.65 in men and 0.92 vs. 0.64 in women). AB-140 WC showed good correlation with manual WC measurements (r = 0.95 in men and 0.90 in women). AB-140 and manual WCs showed comparable correlations with MRI TAAT area (r = 0.92 and 0.96 in men and 0.88 and 0.88 in women). AB-140 is a simple, quick, and precise technique to measure abdominal fat and WC in healthy adults. It provides a useful proxy for TAAT measured by MRI, comparable to the correlation obtained with manual WC measurements. Neither the AB-140 abdominal fat measures nor WC measurement appear to provide a useful proxy measure of VAT.