3D T1-weighted Gradient-echo Sequence Research Articles

Data-Driven Modification of the LI-RADS Major Feature System on Gadoxetate Disodium-Enhanced MRI: Toward Better Sensitivity and Simplicity.

The Liver Imaging Reporting and Data System (LI-RADS) is widely accepted as a reliable diagnostic scheme for hepatocellular carcinoma (HCC) in at-risk patients. However, its application is hampered by substantial complexity and suboptimal diagnostic sensitivity. To propose data-driven modifications to the LI-RADS version 2018 (v2018) major feature system (rLI-RADS) on gadoxetate disodium (EOB)-enhanced magnetic resonance imaging (MRI) to improve sensitivity and simplicity while maintaining high positive predictive value (PPV) for detecting HCC. Retrospective. Two hundred and twenty-four consecutive at-risk patients (training dataset: 169, independent testing dataset: 55) with 742 LR-3 to LR-5 liver observations (HCC: N=498 [67%]) were analyzed from a prospective observational registry collected between July 2015 and September 2018. 3.0 T/T2-weighted fast spin-echo, diffusion-weighted spin-echo based echo-planar and three-dimensional (3D) T1-weighted gradient echo sequences. All images were evaluated by three independent abdominal radiologists who were blinded to all clinical, pathological, and follow-up information. Composite reference standards of either histopathology or imaging follow-up were used. In the training dataset, LI-RADS v2018 major features were used to develop rLI-RADS based on their associated PPV for HCC. In an independent testing set, diagnostic performances of LI-RADS v2018 and rLI-RADS were computed using a generalized estimating equation model and compared with McNemar's test. A P value <0.05 was considered statistically significant. The median (interquartile range) size of liver observations was 13 mm (7-27 mm). The diagnostic table for rLI-RADS encompassed 9 cells, as opposed to 16 cells for LI-RADS v2018. In the testing set, compared to LI-RADS v2018, rLI-RADS category 5 demonstrated a significantly superior sensitivity (76% vs. 61%) while maintaining comparably high PPV (92.5% vs. 94.1%, P=0.126). Compared with LI-RADS v2018, rLI-RADS demonstrated improved simplicity and significantly superior diagnostic sensitivity for HCC in at-risk patients. 3 TECHNICAL EFFICACY STAGE: 2.

High-resolution vessel wall magnetic resonance imaging for depicting imaging features of unruptured intracranial vertebrobasilar dissecting aneurysms.

ObjectiveTo demonstrate the application value of high-resolution vessel wall magnetic resonance imaging (HR-VW-MRI) for depicting the imaging features of unruptured intracranial vertebrobasilar dissecting aneurysms (VBDAs).MethodsHR-VW-MRI data of 49 patients with suspected unruptured VBDAs were retrospectively analyzed. The presence of intramural hematomas (IMH), double lumens, intimal flaps, and outer diameter enlargements were recorded. Specificity and sensitivity were calculated for both two-dimensional (2D) and three-dimensional (3D) sequences. Additionally, IMH volumes were measured and posterior inferior cerebellar artery (PICA) involvement was analyzed.ResultsThirty-five VBDAs were confirmed in 34 patients. The overall sensitivity and specificity were 0.889 (95% confidence interval [CI]: 0.730–0.964) and 0.769 (95% CI: 0.460–0.938) for 2D sequences, and 0.917 (95% CI: 0.764–0.978) and 0.846 (95% CI: 0.537–0.973) for 3D sequences, respectively. Intimal flaps were detected in 57.1%, 87.5%, and 71.4% of all cases on 2D pre-contrast T1-weighted, contrast-enhanced T1-weighted, and 3D T1-weighted black-blood (BB) images, respectively. There was no significant difference in IMH volume between 3D T1-weighted BB and magnetization-prepared rapid gradient-echo sequences. PICA involvement was best visualized using 3D T1 sequences.Conclusion3D T1-weighted BB MRI provided good visualization of VBDA features, with large coverage, and was useful for detecting dissection flaps.

Optimal sequences and sequence parameters for GBCA-enhanced MRI of the glymphatic system: a systematic literature review

The glymphatic system (GS) is a recently discovered waste clearance system in the brain. To evaluate the most promising magnetic resonance imaging (MRI) sequence(s) and the most optimal sequence parameters for glymphatic MRI (gMRI) 4-24 h after administration of gadolinium-based contrast agent (GBCA). Multiple literature databases were systematically searched for articles regarding gMRI or MRI of the perilymph in the inner ear until 11 May 2020. All relevant MRI sequence parameters were tabulated for qualitative analysis. Their potential was assessed based on detection of low dose GBCA, primarily measured as signal intensity (SI) ratio. Thirty articles were included in the analysis. Three-dimensional fluid attenuated inversion recovery (3D-FLAIR), 3D Real Inversion Recovery (3D-Real IR), and multiple 3D T1-weighted gradient echo sequences were used. In perilymph, 3D-FLAIR with a TE of at least 400 ms yielded the highest SIRs. In the qualitative analysis of inner ear studies using 3D-FLAIR, TR was in the range of 4400-10,000 ms, TI 1500-2600 ms, refocusing flip angle (rFA) (range 120°-180°), and echo train length (ETL) 23-173. In the gMRI studies, quantitative analysis was not possible. In the qualitative analysis, 3D-FLAIR was used in the majority (8/12) of the studies, usually with TR 4800-9000 ms, TI 1650-2500 ms, TE 311-561 ms, rFA 90°-120°, and ETL 167-278. Long TE 3D-FLAIR is the most promising sequence for detection of low-dose GBCA in the GS. Clinical and/or phantom studies on other MRI parameters are needed for further optimization of gMRI.

A novel spectrally selective fat saturation pulse design with robustness to B0 and B1 inhomogeneities: A demonstration on 3D T1-weighted breast MRI at 3 T

Spectrally selective fat saturation (FatSat) sequence is commonly used to suppress signal from adipose tissue. Conventional SINC-shaped pulses are sensitive to B0 off-resonance and B1+ offset. Uniform fat saturation with large spatial coverage is especially challenging for the body and breast MRI. The aim of this study is to develop spectrally selective FatSat pulses that offer more immunity to B0/B1+ field inhomogeneities than SINC pulses and evaluate them in bilateral breast imaging at 3T. Optimized composite pulses (OCP) were designed based on the optimal control theory with robustness to a targeted B0/ B1+ conditions. OCP pulses also allows flexible flip angles to meet different requirements. Comparisons with the vendor-provided SINC pulses were conducted by numerical simulation and in vivo scans using a 3D T1-weighted (T1w) gradient-echo (GRE) sequence with coverage of the whole-breast. Simulation revealed that OCP pulses yielded almost half of the transition band and much less sensitivity to B1+ inhomogeneity compared to SINC pulses with B0 off-resonance within ±200Hz and B1+ scale error within ±0.3 (P<0.001). Across five normal subjects, OCP FatSat pulses produced 25-41% lower residual fat signals (P<0.05) with 27-36% less spatial variation (P<0.05) than SINC. In contrast to conventional SINC-shaped pulses, the newly designed OCP FatSat pulses mitigated challenges of wide range of B0/ B1+ field inhomogeneities and achieved more uniform fat suppression in bilateral breast T1w imaging at 3T.

Prediction of post-hepatectomy liver failure using gadoxetic acid-enhanced magnetic resonance imaging for hepatocellular carcinoma with portal vein invasion

PurposeAccurate prediction of post-hepatectomy liver failure (PHLF) is important in advanced hepatocellular carcinoma (HCC). We aimed to retrospectively evaluate the utility of gadoxetic acid-enhanced MRI for predicting PHLF in patients who underwent anatomic hepatectomy for HCC with portal vein invasion. MethodsForty-one patients (32 men, 9 women) were included. Hepatobiliary-phase MR images were acquired 20 min after injection of gadoxetic acid using a 3D fat-suppressed T1-weighted spoiled gradient-echo sequence. Liver-spleen ratio (LSR), remnant hepatocellular uptake index (rHUI), and HUI were calculated. The severity of PHLF was defined according to the International Study Group of Liver Surgery. Differences in LSR between the resected liver and the remnant liver, and HUI and rHUI/HUI between no/mild and severe PHLF were compared using the Wilcoxon signed-rank test and Wilcoxon rank-sum test, respectively. Univariate and multivariate logistic regression analyses were performed to identify predictors of severe PHLF. Areas under the receiver operating characteristic curves (AUCs) of rHUI and rHUI/HUI were calculated for predicting severe PHLF. ResultsNine patients developed severe PHLF. LSR of the remnant liver was significantly higher than that of the resected liver (P < 0.001). Severe PHLF demonstrated significantly lower rHUI (P < 0.001) and rHUI/HUI (P < 0.001) compared with no/mild PHLF. Multivariate logistic regression analysis showed that decreased rHUI (P = 0.012, AUC=0.885) and rHUI/HUI (P = 0.002, AUC=0.852) were independent predictors of severe PHLF. ConclusionGadoxetic acid-enhanced MRI can be a promising noninvasive examination for assessing global and regional liver function, allowing estimation of the functional liver remnant and accurate prediction of severe PHLF before hepatic resection.

Update on MR imaging of the pulmonary vasculature

Magnetic resonance imaging (MRI) plays an increasingly important role in the non-invasive evaluation of the pulmonary vasculature. MR angiographic (MRA) techniques provide morphological information, while MR perfusion techniques provide functional information of the pulmonary vasculature. Contrast-enhanced MRA can be performed at high spatial resolution using 3D T1-weighted spoiled gradient echo sequence or at high temporal resolution using time-resolved techniques. Non-contrast MRA can be performed using 3D steady state free precession, double inversion fast spin echo, time of flight or phase contrast sequences. MR perfusion can be done using dynamic contrast-enhanced technique or using non-contrast techniques such as arterial spin labelling and time-resolved imaging of lungs during free breathing with Fourier decomposition analysis. MRI is used in the evaluation of acute and chronic pulmonary embolism, pulmonary hypertension and other vascular abnormalities, congenital anomalies and neoplasms. In this article, we review the different MR techniques used in the evaluation of pulmonary vasculature and its clinical applications.

3D T1-weighted contrast-enhanced brain MRI in children using a fat-suppressed golden angle radial acquisition: an alternative to Cartesian inversion-recovery imaging

BackgroundT1-weighted post-contrast MRI is essential in brain protocols. We demonstrate the feasibility and utility of a 3D non-Cartesian radial acquisition in children. PurposeTo compare bulk motion artifacts, image quality, and lesion conspicuity in 3D T1-weighted post-contrast brain MRI between a new fat-suppressed radial gradient-echo and a traditional non-fat-suppressed inversion-recovery Cartesian gradient-echo sequence. Material and methodsImages from 53 patients acquired at 3 Tesla were compared. Three radiologists rated the images in three categories, including the presence of bulk motion and whether it impacted diagnosis, whether one sequence was preferred over the other in overall image quality and conspicuity of vascular structures and lesions, and whether diagnosis was possible if only the new fat-suppressed radial acquisition was obtained. ResultsThe Fleiss' kappa for inter-rater agreement was 0.67 for bulk motion and 0.54 for sequence preference. Of the 53 cases, 56% were identified to have significant motion on conventional imaging, while only 13% had motion artifacts on the radial acquisition (p < 0.05). There were no cases where motion was seen on the radial acquisition but not on conventional imaging. Both sequences were equally preferred in 87% of the cases. All radiologists agreed that the radial approach had lower gray-white matter contrast than the conventional inversion-recovery method, but preferred the former for making diagnosis in uncooperative patients. ConclusionWe demonstrate the potential utility of a fat-suppressed 3D T1-weighted post-contrast brain gradient-echo sequence in children. The technique is useful in non-sedate pediatric imaging due to its reduced sensitivity to bulk motion.

Combination of free-breathing radial 3D fat-suppressed T1-weighted gradient-echo sequence with diffusion weighted images: Potential for differentiating malignant from benign peripheral solid pulmonary masses

ObjectivesHigh resolution CT is the most commonly used radiological method for differentiating benign from malignant peripheral solid pulmonary masses, however, some of them are not easily diagnosed by morphology alone. Furthermore, due to the radiation dose, it is unsuitable for patients with disorders requiring repeated examinations over prolonged periods. The aims of this study were to evaluate whether a combination of diffusion-weighted images (DWI) and free-breathing radial 3D fat-suppressed T1-weighted gradient echo (radial volumetric interpolated breath-hold examination, radial VIBE) sequence can enable discrimination between benign from malignant peripheral solid pulmonary masses. Materials and methodsBoth chest CT scan and MR imaging with radial VIBE and DWI were obtained from 47 patients; 30 males and 17 females (mean age 64 years old; age range 48–83 years old). Benign and malignant peripheral solid pulmonary masses were conclusively identified by pathology results. Two radiologists independently reviewed all the images and record radiological features including morphological signs on radial VIBE, CT images, and ADC value. Receiver operating characteristic (ROC) was used to analyze the capability of radial VIBE as well as DWI to distinguish malignant from benign peripheral solid pulmonary masses. ResultsIn 77% of patients, malignant peripheral solid pulmonary masses were found. Morphological signs of mediastinal lymph node enlargement and lobulation were more easily found in malignant masses in both radial VIBE (mediastinal lymph node enlargement: p = 0.033, lobulation: p = 0.039) and CT (mediastinal lymph node enlargement: p = 0.004, lobulation: p = 0.012). The ADC value were also significant difference between benign and malignant groups (p = 0.001). Combined ADC value with radial VIBE was a most specific test than routine-dose CT (86.1% vs 75%, p < 0.001), but less sensitive than routine-dose CT (81.8% vs 90.9%; p < 0.001) for malignant peripheral solid pulmonary masses detection. Diagnostic accuracy was 89% for combining ADC value with radial VIBE, and 85% for routine-dose CT. ConclusionsCombination of morphological signs and ADC value seems to improve differentiating malignant from benign peripheral solid pulmonary masses. Especially in patients unable to endure radiation exposure, suspend respiration, radial VIBE provides similar morphological signs displaying to those on routine-dose CT.

47. Effect of Antipsychotic Medication on Hippocampal Function and Neurochemistry: A Longitudinal Study in Patients With Schizophrenia

Background: Our prior studies with PET and 15O have shown associations between hippocampal function and treatment response to antipsychotic drugs (APDs). In addition, we found elevated hippocampal glutamate in unmedicated patients with schizophrenia (SZ) but not in medicated. Here, we use a longitudinal design to evaluate the relationship between glutamate and function of the hippocampus in SZ in relation to treatment response to APDs. Methods: 34 SZ were scanned while unmedicated and after 6 weeks of APD. 23 matched healthy controls were also scanned twice six weeks apart. Imaging was done on a 3T head-only scanner equipped with a circularly polarized transmit/receive head coil. A high-resolution structural scan was acquired using the 3D T1-weighted magnetization-prepared rapid acquisition gradient-echo sequence ([TR/TE/ TI] = 2300/3.93/1100ms; flip angle = 12°; 256 × 256 matrix; and 1mm isotropic voxels). Eyes open resting-state fMRI (rsfMRI) was acquired using the gradient recalled echo-planar-imaging sequence (TR/TE = 2000/30ms, flip angle = 70°, field of view = 192mm3, 6mm slice thickness, 1mm gap, 30 axial slices, 225 acquisitions). rsfMRI data were preprocessed and analyzed using CONN toolbox and SPM12. Resting-state magnetic resonance spectroscopy was collected with a voxel prescribed in the left hippocampus (2.7 × 1.5 × 1cm) using the PRESS sequence optimized for glutamate (TR/TE = 2000/80ms, spectral bandwidth = 1024 points, 640 averages) and analyzed in jMRUI. A median split was used to separate SZ into treatment responders and non-responders (calculated as percent change in BPRS positive symptoms). Results: Before treatment, those who subsequently responded to treatment were characterized by significantly elevated glutamate levels compared to both healthy controls and nonresponders. Treatment responders but not non-responders or healthy controls glutamate levels significantly decreased over the 6-week course of treatment. Additionally, treatment responders demonstrated reduced hippocampal blood oxygen-level-dependent (BOLD) fMRI signal compared to healthy controls and nonresponders. Conclusion: Before treatment, both hippocampal glutamate levels and hippocampal BOLD signal appear to differentiate good treatment responders from poor treatment responders.

基于表面的形态测量学：3T与7T高分辨磁共振结构成像受试者内比较

ObjectiveHigh resolution structural MR imaging can reveal structural characteristics of cerebral cortex and provide an insight into normal brain development and neuropsychological diseases. The aim of this study was to compare cortical structural characteristics of normal human brain between 3T and 7T MRI systems using surface-based morphometry based on high resolution structural MR imaging. Methods Twelve healthy volunteers were scanned by both 3T with 3D T1-weighted fast spoiled gradient recalled echo (3D T1-FSPGR) sequence and 7T with 3D T1-weighted magnetization-prepared rapid gradient echo (3D T1-MPRAGE) sequence. MRI data were processed with FreeSurfer. The cortical thickness, white and gray matter surface area, convexity, and curvature from data of 3T and 7T were measured and compared by paired t-test. Results Measurements of mean cortical thickness, total white matter surface area and gray matter surface area of 3T were larger than those of 7T (left hemisphere: P=0.000, 0.006, 0.020 respectively; right hemisphere: P=0.000, 0.000, 0.000 respectively). Surface-based morphometry over the whole brain demonstrated both reduced and increased measurements of cortical thickness, white and gray surface area, convexity, and curvature at 7T compared to 3T. Conclusions Inconsistency of brain structural attribute between 3T and 7T was confirmed, and researchers should be cautious about data when using ultrahigh field MR system to investigate brain structural changes.

Free-breathing dynamic liver examination using a radial 3D T1-weighted gradient echo sequence with moderate undersampling for patients with limited breath-holding capacity

PurposeTo compare free-breathing radial VIBE with moderate undersampling (us-radial-VIBE) with a standard breathhold T1-weighted volumetric interpolated sequence (3D GRE VIBE) in patients unable to suspend respiration during dynamic liver examination. Material and methods23 consecutive patients underwent dynamic liver MR examination using the free-breathing us-radial-VIBE sequence as part of their oncologic follow-up. All patients were eligible for the free-breathing protocol due to severe respiratory artifacts at the planning or precontrast sequences. The us-radial-VIBE acquisitions were compared to the patientś last staging liver MRI including a standard breathhold 3D GRE VIBE.For an objective image evaluation, signal intensity (SI), image noise (IN), signal-to-noise ratio (SNR) and contrast-enhancement ratio (CER) were compared. Representative image quality parameters, including typical artifacts were independently, retrospectively and blindly scored by four readers. ResultsUs-radial-VIBE had significant lower SNR (p<0.0001) and higher IN (p<0.0001), whereas SI did not differ (p=0.62). Temporal resolution assessed with CER in the arterial phase showed higher values for us-radial-VIBE (p=0.028). Subjective image quality parameters received generally slightly higher scores for 3D GRE VIBE. In a smaller subgroup comprising patients with severe respiratory artifacts also at reference breathhold 3D GRE VIBE examination, us-radial-VIBE showed significantly higher image quality scores. Furthermore, there were generally more severe respiratory artifacts in 3D GRE VIBE, whereas streaking was characteristic in almost all us-radial-VIBE acquisitions but did not affect diagnostic validity. ConclusionFree-breathing dynamic liver imaging using us-radial-VIBE delivers accurate temporal resolution, low motion artifact susceptibility and good image quality and represents a promising alternative in patients unable to suspend respiration.

Clinical evaluation of three‐dimensional late enhancement MRI

To assess the diagnostic value of three-dimensional late enhancement (3D-LGE) for the detection of myocardial necrosis in a routine clinical setting. 3D-LGE has been proposed as a novel magnetic resonance (MR) technique for the accurate detection of myocardial scar in both the ventricles and atria. Its performance in clinical practice has been poorly examined. Fifty-seven patients referred for cardiac MR examination including scar imaging were prospectively enrolled. Gadolinium enhanced single breathhold 3D T1-weighted gradient-echo inversion recovery sequence and a conventional 2D-LGE sequence were performed using a 1.5 Tesla clinical MR imaging system. The presence, pattern and transmurality of LGE, diagnostic accuracy and level of diagnostic confidence as well as image quality (median quality, mean LGE signal intensity, sharpness, virtual scan time) were graded on a 4-point scale. Interpretable images were obtained in 52/57 2D-LGE and in 47/57 3D high-resolution exams. LGE was detected in 10 patients with ischemic pattern, 9 with nonischemic pattern, while it was absent in 28, resulting in a total of 47 complete datasets. The detection of global and segmental LGE as well as its transmural extent were similar for both techniques (P = 0.65, P = 0.305, and P = 0.15, respectively). Image quality (median quality, LGE/ myocardial and LGE/ blood pool sharpness) was similar for both techniques (P = 0.740, P = 0.34, and P = 1.00, respectively), but LGE signal intensity was higher with 2D (P = 0.020). 3D-LGE diagnostic and quality scores were comparable to 2D-LGE in a routine clinical setting. Further technical refinement is required for 3D LGE to offer a reliable alternative for high quality scar imaging. 2 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;45:1675-1683.

Nodal staging in rectal cancer: why is restaging after chemoradiation more accurate than primary nodal staging?

PurposeThis study aims to explore the influence of chemoradiation treatment (CRT) on rectal cancer nodes and to generate hypotheses why nodal restaging post-CRT is more accurate than at primary staging.MethodsThirty-nine patients with locally advanced rectal cancer underwent MRI pre- and post-CRT. All visible mesorectal nodes were measured on a 3D T1-weighted gradient echo (3D T1W GRE) sequence with 1-mm3 voxels and matched between pre- and post-CRT-MRI and with histology by lesion-by-lesion matching. Change in number and size of nodes was compared between pre- and post-CRT-MRI. ROC curves were constructed to assess diagnostic performance of size.ResultsEight hundred ninety-five nodes were found pre-CRT: 44 % disappeared and 40 % became smaller post-CRT. Disappearing nodes were initially significantly smaller than nodes that remained visible post-CRT: 2.9 mm vs. 3.8 mm. cN+ stage was predicted in 97 % pre-CRT and 36 % of patients had ypN+ post-CRT. ypN+ patients had significantly larger nodes than ypN0 patients both pre- and post-CRT. Optimal size cutoff for post-CRT ypN stage prediction was 2.5 mm (area under the curve (AUC) of 0.78) at MRI.ConclusionsAfter CRT, most lymph nodes become smaller, and many disappear. Size predicts disappearance and node positivity. Together with a low prevalence of ypN+, this can explain the higher accuracy of nodal staging after CRT than in a primary staging setting, possibly of use when considering organ-preserving strategies after CRT.

Automatic differentiation of placental perfusion compartments by time-to-peak analysis in mice

IntroductionThe aim of this study was to develop an automatic differentiation of two perfusion compartments within the mouse placenta based on times of maximal contrast enhancement for a detailed and reproducible perfusion assessment. MethodsPlacentas (n = 17) from pregnant BALB/c mice (n = 10) were examined in vivo at 7T on gestation day 16.5. Coronal dual-echo 3D T1-weighted gradient-echo sequences were acquired after application of contrast agent for dynamic MRI. An adapted gamma variate function was fitted to the discrete concentration time curves to evaluate the effect of noise on perfusion and segmentation results. Time-to-peak maps based on fitted and discrete curves of each placenta were used to classify each voxel into the high- or low-blood flow compartment using k-means clustering. Perfusion analysis was performed using the steepest slope model and also applied to fitted and discrete curves. Results were compared to manually defined compartments from two independent observers using the Dice coefficient D. ResultsManually defined placental areas of high-flow and low-flow were similar to the automatic segmentation for discrete (D = 0.76/0.75; D = 0.76/0.79) and fitted (D = 0.80/0.80; D = 0.81/0.82) concentration time curves. Mean perfusion values of discrete and fitted curves ranged in the high-flow compartment from 134 to 142 ml/min/100 ml (discrete) vs. 138–143 ml/min/100 ml (fitted) and in the low-flow compartment from 91 to 94 ml/min/100 ml (discrete) vs. 74–82 ml/min/100 ml (fitted). DiscussionOur novel approach allows the automatic differentiation of perfusion compartments of the mouse placenta. The approach may overcome limitations of placental perfusion analyses caused by tissue heterogeneity and a potentially biased selection of regions of interest.

Imaging of articular cartilage: current concepts.

Magnetic resonance imaging (MRI) is the gold standard method for non-invasive assessment of joint cartilage, providing information on the structure, morphology and molecular composition of this tissue. There are certain minimum requirements for a MRI study of cartilage tissue: machines with a high magnetic field (> 1.5 Tesla); the use of surface coils; and the use of T2-weighted, proton density-weighted fast-spin echo (T2 FSE-DP) and 3D fat-suppressed T1-weighted gradient echo (3D-FS T1W GRE) sequences. For better contrast between the different joint structures, MR arthography is a method that can highlight minimal fibrillation or fractures of the articular surface and allow evaluation of the integrity of the native cartilage-repair tissue interface. To assess the biochemical composition of cartilage and cartilage repair tissue, various techniques have been proposed for studying proteoglycans [dGEMRIC, T1rho mapping, sodium (23Na) imaging MRI, etc.], collagen, and water distribution [T2 mapping, "magnetisation transfer contrast", diffusion-weighted imaging (DWI), and so on]. Several MRI classifications have been proposed for evaluating the processes of joint degeneration (WORMS, BLOKS, ICRS) and post-surgical maturation of repair tissue (MOCART, 3D MOCART). In the future, isotropic 3D sequences set to improve image quality and facilitate the diagnosis of disorders of articular structures adjacent to cartilage.

Evaluation of microvascular permeability with dynamic contrast-enhanced MRI for the differentiation of primary CNS lymphoma and glioblastoma: radiologic-pathologic correlation.

Dynamic contrast-enhanced MR imaging can provide in vivo assessment of the microvasculature in intracranial tumors. The aim of the present study was to evaluate the diagnostic performance of dynamic contrast-enhanced MR imaging derived vascular permeability parameters, including the volume transfer constant, the volume of extravascular extracellular space, and the flux rate constant between the extravascular extracellular space and plasma, for the differentiation of primary CNS lymphoma and glioblastoma. Sixty glioblastomas and 11 primary central nervous system lymphomas were included. Pretreatment T1-weighted dynamic contrast-enhanced MR imaging with a 3D T1-weighted spoiled gradient-echo sequence was performed on a 3T MR imaging scanner. Perfusion parameters (volume transfer constant, the volume of extravascular extracellular space, and the flux rate constant) were measured on the basis of the Tofts-Kernmode model. The Mann-Whitney U test and receiver operating characteristic analysis were used to compare those parameters between primary central nervous system lymphoma and glioblastoma. Histopathologic correlation of dynamic contrast-enhanced MR imaging findings was performed by using reticulin staining and CD31 immunohistochemistry. Median volume transfer constant and flux rate constant values were significantly higher in primary central nervous system lymphoma (0.145 ± 0.057 and 0.396 ± 0.088) than in glioblastoma (0.064 ± 0.021 and 0.230 ± 0.058) (P < .001, respectively). Median volume of extravascular extracellular space values did not differ significantly between primary central nervous system lymphoma (0.434 ± 0.165) and glioblastoma (0.319 ± 0.107). On receiver operating characteristic analysis, volume transfer constant had the best discriminative value for differentiating primary central nervous system lymphoma and glioblastoma (threshold, 0.093; sensitivity, 90.9%; specificity, 95.0%). Histopathologic evaluation revealed intact vascular integrity in glioblastoma despite endothelial proliferation, whereas primary central nervous system lymphoma demonstrated destroyed vessel architecture, thereby promoting vascular disintegrity. Primary central nervous system lymphoma demonstrated significantly higher volume transfer constant and flux rate constant values compared with glioblastoma, implying a higher vascular permeability in primary central nervous system lymphoma. These findings confirm initial observations from perfusion CT and dynamic contrast-enhanced MR imaging studies, correlating with underlying histopathologic features, and may be useful in distinguishing primary central nervous system lymphoma from glioblastoma.

Radial MRI during free breathing in contrast-enhanced hepatobiliary phase imaging

Use of gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) for diagnosis of hepatic tumors has been previously reported. Fat-saturated 3D T1-weighted gradient echo sequence (TIGRE) imaging using a breath-hold technique is usually used for dynamic studies and hepatobiliary phase Gd-EOB-DTPA-enhanced magnetic resonance imaging (MRI). In cases where the patient has difficulty holding their breath, this scanning method can be difficult. To investigate the usefulness of a fat-saturated T1-weighted spin-echo (SE) sequence using a radial read-out (radial acquisition regime-SE, RADAR-SE) during free breathing for hepatobiliary phase Gd-EOB-DTPA-enhanced MRI. Images were acquired at 1.5 T. First, a phantom with diluted Gd-EOB-DTPA was scanned using the TIGRE sequence and the RADAR-SE sequence. Contrast ratios of the sequences were compared. Next, the hepatobiliary phase was imaged in 62 patients using the TIGRE sequence with breath-hold and the RADAR-SE during free breathing. Qualitative and quantitative evaluations were compared. In the phantom study, RADAR-SE had a higher contrast ratio than TIGRE. In the clinical study, artifacts were more conspicuous in RADAR-SE compared to TIGRE images in the qualitative evaluation. However, RADAR-SE images were equal to or better than TIGRE images in patients who had difficulty holding their breath. The signal intensity ratio of the liver was statistically higher using RADAR-SE than TIGRE. RADAR-SE can be useful for hepatobiliary phase Gd-EOB-DTPA-enhanced MRI in patients who have difficulty holding their breath.

Can magnetic resonance imaging at 3.0‐Tesla reliably detect patients with endometriosis? Initial results

The aim of this study was to determine whether an optimized 3.0-Tesla magnetic resonance imaging (MRI) protocol is sensitive and specific enough to detect patients with endometriosis. This was a prospective cohort study with consecutive patients. Forty consecutive patients with clinical suspicion of endometriosis underwent 3.0-Tesla MRI, including a T2-weighted high-resolution fast spin echo sequence (spatial resolution=0.75 ×1.2 ×1.5 mm³) and a 3D T1-weighted high-resolution gradient echo sequence (spatial resolution=0.75 ×1.2 × 2.0 mm³). Two radiologists reviewed the dataset with consensus reading. During laparoscopy, which was used as reference standard, all lesions were characterized according to the revised criteria of the American Fertility Society. Patient-level and region-level sensitivities and specificities and lesion-level sensitivities were calculated. Patient-level sensitivity was 42% for stage I (5/12) and 100% for stages II, III and IV (25/25). Patient-level specificity for all stages was 100% (3/3). The region-level sensitivity and specificity was 63% and 97%, respectively. The sensitivity per lesion was 61% (90% for deep lesions, 48% for superficial lesions and 100% for endometriomata). The detection rate of obliteration of the cul-the-sac was 100% (10/10) with no false positive findings. The interreader agreement was substantial to perfect (kappa=1 per patient, 0.65 per lesion and 0.71 for obliteration of the cul-the-sac). An optimized 3.0-Tesla MRI protocol is accurate in detecting stage II to stage IV endometriosis.

Establishment of a Swine Model for Validation of Perfusion Measurement by Dynamic Contrast-Enhanced Magnetic Resonance Imaging

The aim of the study was to develop a suitable animal model for validating dynamic contrast-enhanced magnetic resonance imaging perfusion measurements. A total of 8 pigs were investigated by DCE-MRI. Perfusion was determined on the hind leg musculature. An ultrasound flow probe placed around the femoral artery provided flow measurements independent of MRI and served as the standard of reference. Images were acquired on a 1.5 T MRI scanner using a 3D T1-weighted gradient-echo sequence. An arterial catheter for local injection was implanted in the femoral artery. Continuous injection of adenosine for vasodilation resulted in steady blood flow levels up to four times the baseline level. In this way, three different stable perfusion levels were induced and measured. A central venous catheter was used for injection of two different types of contrast media. A low-molecular weight contrast medium and a blood pool contrast medium were used. A total of 6 perfusion measurements were performed with a time interval of about 20–25 min without significant differences in the arterial input functions. In conclusion the accuracy of DCE-MRI-based perfusion measurement can be validated by comparison of the integrated perfusion signal of the hind leg musculature with the blood flow values measured with the ultrasound flow probe around the femoral artery.

Dynamic contrast-enhanced and ultra-high-resolution breast MRI at 7.0 Tesla

To assess the feasibility of 7-T contrast-enhanced breast MRI in patients with suspicious masses. Twenty patients with 23 suspicious breast masses on conventional imaging (mean size 13 mm, range 5-27 mm) were examined at 7 T. The MRI protocol included a dynamic series with injection of 0.1 mmol/kg gadobutrol (seven consecutive 3D T1-weighted gradient echo sequences, resolution 1 × 1 × 2 mm(3), temporal resolution 63 s) and ultra-high-resolution imaging (T1-weighted 3D gradient echo sequence, resolution 0.45 × 0.57 × 0.45 mm(3)). Two observers (R1 and R2) independently judged the examinations on image quality and classified lesions according to BI-RADS. The added value of ultra-high-resolution imaging was assessed. The image quality was deemed excellent in 1 and 0, good in 10 and 12, sufficient in 8 and 8, and insufficient in 1 and 0 for R1 and R2 respectively. Twenty of the 23 lesions were identified at 7-T MRI by both observers. All histopathologically proven malignant lesions (n = 19) were identified and classified as BI-RADS-MRI 4 or 5. Ultra-high-resolution imaging increased reader confidence in 88 % (R1) and 59 % (R2) of acquisitions. The study shows the feasibility of dynamic contrast-enhanced 7-T breast MRI, where all malignant mass lesions were identified by two observers. • Magnetic resonance imaging is important in the evaluation of breast cancer. • Recently, 7-T MRI has become available. • The 7-T dynamic contrast-enhanced breast MRI is feasible in patients. • The 7-T breast examinations are amenable to evaluation according to BI-RADS.