Fast Spin-echo Magnetic Resonance Imaging Research Articles

Denoising of three-dimensional fast spin echo magnetic resonance images of knee joints using spatial-variant noise-relevant residual learning of convolution neural network

PurposeTwo-dimensional (2D) fast spin echo (FSE) techniques play a central role in the clinical magnetic resonance imaging (MRI) of knee joints. Moreover, three-dimensional (3D) FSE provides high-isotropic-resolution magnetic resonance (MR) images of knee joints, but it has a reduced signal-to-noise ratio compared to 2D FSE. Deep-learning denoising methods are a promising approach for denoising MR images, but they are often trained using synthetic noise due to challenges in obtaining true noise distributions for MR images. In this study, inherent true noise information from two number of excitations (2-NEX) acquisition was used to develop a deep-learning model based on residual learning of convolutional neural network (CNN), and this model was used to suppress the noise in 3D FSE MR images of knee joints. MethodsA deep learning-based denoising method was developed. The proposed CNN used two-step residual learning over parallel transporting and residual blocks and was designed to comprehensively learn real noise features from 2-NEX training data. ResultsThe results of an ablation study validated the network design. The new method achieved improved denoising performance of 3D FSE knee MR images compared with current state-of-the-art methods, based on the peak signal-to-noise ratio and structural similarity index measure. The improved image quality after denoising using the new method was verified by radiological evaluation. ConclusionA deep CNN using the inherent spatial-varying noise information in 2-NEX acquisitions was developed. This method showed promise for clinical MRI assessments of the knee, and has potential applications for the assessment of other anatomical structures.

SynthStrip: skull-stripping for any brain image

The removal of non-brain signal from magnetic resonance imaging (MRI) data, known as skull-stripping, is an integral component of many neuroimage analysis streams. Despite their abundance, popular classical skull-stripping methods are usually tailored to images with specific acquisition properties, namely near-isotropic resolution and T1-weighted (T1w) MRI contrast, which are prevalent in research settings. As a result, existing tools tend to adapt poorly to other image types, such as stacks of thick slices acquired with fast spin-echo (FSE) MRI that are common in the clinic. While learning-based approaches for brain extraction have gained traction in recent years, these methods face a similar burden, as they are only effective for image types seen during the training procedure. To achieve robust skull-stripping across a landscape of imaging protocols, we introduce SynthStrip, a rapid, learning-based brain-extraction tool. By leveraging anatomical segmentations to generate an entirely synthetic training dataset with anatomies, intensity distributions, and artifacts that far exceed the realistic range of medical images, SynthStrip learns to successfully generalize to a variety of real acquired brain images, removing the need for training data with target contrasts. We demonstrate the efficacy of SynthStrip for a diverse set of image acquisitions and resolutions across subject populations, ranging from newborn to adult. We show substantial improvements in accuracy over popular skull-stripping baselines – all with a single trained model. Our method and labeled evaluation data are available at https://w3id.org/synthstrip.

Feasibility of salt pads to improve fat suppression in low-field MRI systems

IntroductionFat-suppressed images are essential in clinical practice but are often affected by magnetic field inhomogeneity, resulting in poor image quality. We hypothesized that salt (99% sodium chloride [NaCl]) could be used as a magnetic field uniformity assist pad and verified whether salt pads improve magnetic field uniformity and the fat suppression effect in low-field magnetic resonance imaging (MRI) systems. MethodsWe conducted a small clinical study where coronal 2D fast spin-echo T2-weighted MRI with fat suppression was performed. The subjects were 10 healthy volunteers (six men and four women) with no surgical history, with a mean age of 20.5 years (range, 20–30 years). In the clinical study, we performed physical and visual evaluation by imaging a subject's knee with and without salt pads. ResultsThe results of the clinical study indicated that the use of salt pads improved the magnetic field uniformity, thus increasing the fat suppression effect. ConclusionsSalt pads improved the homogeneity of the magnetic field and the fat suppression effect in low-field MRI systems. Implications for practiceThe use of salt pads in low-field MRI systems could provide more accurate fat suppression images.

Evaluation of lymph nodes in oral squamous cell carcinoma by diffusion-weighted magnetic resonance imaging, apparent diffusion coefficient mapping, and fast-spin echo magnetic resonance imaging

Objectives: To evaluate cervical lymph nodes in OSCC with fast spin echo MRI. ii) To evaluate cervical lymph nodes in OSCC with Diffusion Weighted MRI & estimate its ADC value. iii) To compare the findings of cervical lymph nodes in OSCC with diffusion-weighted MRI, ADC mapping and fast spin echo MRI with histopathology. Methods: The study was conducted on 25 histopathologically proven OSCC patients. Enlarged cervical lymph nodes were assessed by Fast spin echo MRI and diffusion weighted MRI. Cervical lymph nodal status in OSCC regarding whether it is benign or malignant was evaluated by diffusion-weighted MRI, ADC mapping and Fast Spin Echo MRI characteristics. These values were compared on post operative histopathology for lymph nodal metastasis. Results: By fast spin echo MRI: Number of true-positive was 05 (4.23%). Number of false-positive was 05(4.23%). Sensitivity was 32.25%. Specificity was 95.10%. Accuracy was 50% positive predictive value (PPV) was 50%. Negative predictive value (NPV) was 86.44%. By DWI MRI: Number of true-positive was 12 (10.16%). Number of false-positive was 12 (10.16%). Sensitivity was 75%. Specificity was 88.24%. Accuracy was 96.69%. PPV was 50%. NPV was 86.44%. Conclusions: DW imaging performed with ADC values showed higher accuracy than fast spin-echo MRI and can provide added value in cervical nodal metastases in OSCC.

Tumor grade estımatıon of clear cell and papıllary renal cell carcınomas usıng contrast-enhanced MDCT and FSE T2 weıghted MR ımagıng: radıology-pathology correlatıon.

Discrimination of low grade (grade 1-2) renal tumors from high grade (grade 3-4) ones carries crucial importance in terms of the management of these patients and also in the decision-making of appropriate treatment strategies. Our aim was to investigate whether contrast-enhanced multidetector computed tomography (MDCT) and T2 weighted fast spin echo (FSE) magnetic resonance imaging (MRI) could play a specific role in the discrimination of low grade versus high grade tumors in clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) patients. In this study, we retrospectively evaluated 66 RCC patients based on histopathologic findings who had underwent either partial or total nephrectomies. Our cohort consisted of 52 ccRCC and 14 pRCC patients, of whom 50 were male (%76) and 16 were female (%24). Among the 52 ccRCC patients, 18 had both cortico-medullary phase contrast-enhanced CT and MRI, 15 had only cortico-medullary phase CT and 19 had only MRI examination. In the pRCC group, 8 patients had both cortico-medullary phase contrast-enhanced CT and MRI, 3 had only cortico-medullary phase CT and 3 had only MRI. We both calculated mean tumor attenuation values on cortico-medullary phase MDCT images as HU (hounsfield unit) and also tumor mean signal intensity values on FSE T2 weighted MR images, using both region of interest and whole lesion measurements including normal renal cortex. The obtained values were compared with the grading results of the ccRCC and pRCC tumors according to the WHO/International Society of Urological Pathology grading system. A significant positive correlation was found between the mean attenuation values of both tumor subtypes on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade tumors exhibited higher mean attenuation values (74.3 ± 22.3 HU) than the low grade tumors (55.2 ± 23.7 HU) in both subtypes. However, a statistically significant correlation was not found between the mean signal intensity values of the two tumor subtypes on FSE T2 weighted MR images and their grades (p > 0.05). Low grade tumors had a mean signal intensity value of 408.9 ± 44.6, while high grade tumors showed a value of 382.1 ± 44.2. The analysis of the ccRCC group patients, yielded a statistically significant correlation between the mean signal intensity values on T2 weighted images and tumor grading (p < 0.001). Low grade (grade 1-2) ccRCC patients exhibited higher mean signal intensity values (475.7 ± 51.3), as compared to those of high grade (grade 3-4) (418.5 ± 45.7) tumors. On the other hand, analysis of the pRCC group patients revealed that there was a significant correlation between the mean attenuation values of tumors on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade papillary subtype tumors (54.2 ± 25.2) showed higher mean attenuation values than the low grade (35.5 ± 18.8) ones. Contrast-enhanced MDCT and T2 weighted FSE MRI can play a considerable role in the discrimination of low grade versus high grade tumors of both subtype RCC patients. Thus, these non-invasive evaluation techniques may have positive impact on the determination of the management and treatment strategies of these patients.

3D MRI: Technical Considerations and Practical Integration.

One of the main advantages of three-dimensional (3D) magnetic resonance imaging (MRI) is the possibility of isotropic voxels and reconstructed planar cuts through the volumetric data set in any orientation with multiplanar reformation software through real-time evaluation. For example, reformats by the radiologist during reporting allows exploitation of the full potential of isotropic 3D volumetric acquisition or through standardized retrospective reformats of thicker predefined slices of an isotropic volumetric data set by technologists. The main challenges for integrating 3D fast spin echo (FSE) and turbo spin-echo (TSE) MRI in clinical practice are a long acquisition time and some artifacts, whereas for integrating 3D gradient-recalled echo protocols, the main challenges are lower signal-to-noise ratios (SNRs) and the inability to produce intermediate, and T2-weighted contrast. The implementation of bidirectional parallel imaging acquisition and random undersampling acceleration strategies of 3D TSE pulse sequences substantially shortens the examination time with only minor SNR reductions. This article provides an overview of general technical considerations of 3D FSE and TSE sequences in musculoskeletal MRI. It also describes how these sequences achieve efficient data acquisition and reviews the main advantages and challenges for their introduction to clinical practice.

Distribution of Bone Contusion Patterns in Acute Noncontact Anterior Cruciate Ligament–Torn Knees

Background: Bone contusions are commonly observed on magnetic resonance imaging (MRI) in individuals who have sustained a noncontact anterior cruciate ligament (ACL) injury. Time from injury to image acquisition affects the ability to visualize these bone contusions, as contusions resolve with time. Purpose: To quantify the number of bone contusions and their locations (lateral tibial plateau [LTP], lateral femoral condyle [LFC], medial tibial plateau [MTP], and medial femoral condyle [MFC]) observed on MRI scans of noncontact ACL-injured knees acquired within 6 weeks of injury. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We retrospectively reviewed clinic notes, operative notes, and imaging of 136 patients undergoing ACL reconstruction. The following exclusion criteria were applied: MRI scans acquired beyond 6 weeks after injury, contact ACL injury, and previous knee trauma. Fat-suppressed fast spin-echo T2-weighted MRI scans were reviewed by a blinded musculoskeletal radiologist. The number of contusions and their locations (LTP, LFC, MTP, and MFC) were recorded. Results: Contusions were observed in 135 of 136 patients. Eight patients (6%) had 1 contusion, 39 (29%) had 2, 41 (30%) had 3, and 47 (35%) had 4. The most common contusion patterns within each of these groups were 6 (75%) with LTP for 1 contusion, 29 (74%) with LTP/LFC for 2 contusions, 33 (80%) with LTP/LFC/MTP for 3 contusions, and 47 (100%) with LTP/LFC/MTP/MFC for 4 contusions. No sex differences were detected in contusion frequency in the 4 locations (P > .05). Among the participants, 50 (37%) had medial meniscal tears and 52 (38%) had lateral meniscal tears. Conclusion: The most common contusion patterns observed were 4 locations (LTP/LFC/MTP/MFC) and 3 locations (LTP/LFC/MTP).

Comparison of cortico-medullary phase contrast-enhanced MDCT and T2-weighted MR imaging in the histological subtype differentiation of renal cell carcinoma: radiology-pathology correlation.

PurposeRenal cell carcinoma (RCC) subtype differentiation is of crucial importance in the management and prognosis of these patients. In this study, we investigated the usefulness of unenhanced and cortico-medullary phase contrast-enhanced multidetector-row computed tomography (MDCT) and T2-weighted fast spin-echo (FSE) magnetic resonance imaging (MRI) modalities in the discrimination of the 3 main subtype RCC patients in correlation with their histopathological findings.Material and methodsA total of 80 pathologically proven RCC patients who had undergone either partial or total nephrectomy were retrospectively investigated in this study. Their histological subtypes were 54 clear cell renal cell carcinoma (ccRCC), 15 papillary renal cell carcinoma (pRCC), and 11 chromophobe renal cell carcinoma (cRCC), based on pathological evaluation. There were 62 male (77.5%) and 18 female (22.5%) patients. Among the 54 ccRCC patients, 29 patients had both non-contrast and cortico-medullary phase CT, 1 had only non-contrast CT, 5 only had cortico-medullary phase CT, and 38 had MRI examination. In the pRCC group, 10 patients had both non-contrast and cortico-medullary phase CT, 1 had only non-contrast CT, 1 had only cortico-medullary phase CT, and 12 had MRI. Finally, in the remaining 11 cRCC patients, 9 had both non-contrast and cortico-medullary phase CT, and only 5 had MRI. We calculated both tumour attenuation values as HU (Hounsfield units) on unenhanced and cortico-medullary phase MDCT images and also tumour mean signal intensity values on FSE T2-weighted MRI images by using the region of interest (ROI) including normal renal cortex measurements. Besides quantitative evaluation, we also performed qualitative visual assessment of tumours on contrast-enhanced MDCT and FSE T2-weighted MRI.ResultsThere was no statistically significant difference among the attenuation values of the 3 tumour subtypes on pre-contrast CT images. ccRCC demonstrated a prominent degree of contrast enhancement compared to the chromophobe and papillary ones on cortico-medullary phase MDCT. We found no statistically significant difference between chromophobe and papillary subtypes, although chromophobe tumours showed slightly higher attenuation values compared to papillary ones. ccRCCs usually demonstrated a heterogenous contrast enhancement on cortico-medullary phase CT images, while the papillary subtype usually had a homogenous appearance on visual assessment. On FSE T2-weighted MR images, the signal intensity values of ccRCC patients were found to be significantly higher than both chromophobe and papillary subtypes. Although cRCC patients had a prominently lower T2 signal intensity than clear cell subtype, there was no statistically significant signal intensity difference between chromophobe and papillary subtypes. Regarding visual assessment, papillary subtype tumours showed a mostly homogenous appearance on T2-weighted images and a statistically significant difference was present. On the other hand, there was no significant difference of visual assessment of the clear cell and chromophobe subtypes.ConclusionsThe measurement of the attenuation values on cortico-medullary phase MDCT and the mean signal intensity values on FSE T2-weighted MRI can provide useful information in the differentiation of RCC main subtypes. Also, visual assessment of tumours on both modalities can contribute to this issue by providing additional imaging properties.

The locus coeruleus: In‐vivo characterization with advanced MRI methods and associations with memory in older adults at risk for Alzheimer’s disease

AbstractBackgroundThe locus coeruleus (LC) is the brain’s main source of norepinephrine and plays a key role in modulating attention and memory processes. In Alzheimer’s disease (AD), the LC has been identified as an early site of tau accumulation and this tau pathology may spread via its connections to the transentorhinal cortex (TEC). Historically, this region has been nearly impossible to study in vivo. However, recent advances in structural magnetic resonance imaging (MRI) have provided opportunities to capture the integrity of LC neurons and their projections. We utilized a combination of neuromelanin‐sensitive and diffusion tensor MRI to examine LC integrity and its role in memory.Method31 older adults (26 cognitively normal; 5 MCI) underwent T1 fast spin echo and diffusion MRI scans as well as neuropsychological testing. Bilateral LC contrast ratios (CRs) were calculated as neuromelanin‐related signal intensities relative to a reference region. In a subset of participants (n=12; 10 cognitively normal, 2 MCI) LC‐TEC white matter pathways were reconstructed using probabilistic tractography in FSL and average fractional anisotropy (FA) was extracted. Logical Memory and CVLT‐2 were used to assess verbal learning and memory.ResultResults revealed lower bilateral LC‐CRs was associated with poorer performance on measures of story learning (LMI; r=0.425, p=.045) and word‐list recall (CVLT‐2 Short Delay Recall: r=.481, p=.006; CVLT‐2 Long Delay Recall: r=.375, p=.038). Tractography analyses indicated that higher FA of the left LC‐TEC tract was associated with poorer story learning (LM1: r=‐.651, p=.02), whereas higher FA of the right LC‐TEC tract was associated with poorer word‐list recall (CVLT‐2 Short Delay Recall: r=‐.599, p=.039; CVLT‐2 Short Delay Cued Recall, r=‐.705, p=.01).ConclusionPreliminary results indicate that neuromelanin and tractography MRI methods can be utilized for in vivo characterization of the human LC. Lower neuromelanin signal, but higher FA is associated with poorer memory performance in a sample of cognitively normal and MCI adults. Greater tau pathology may alter the LC signal and encroaching tau accumulation in the LC‐TEC pathway may initiate neuroinflammatory processes reflected by increased FA. Future work is needed to understand the temporal course and nature of LC changes across the aging‐MCI‐AD continuum.

Correlation of hip capsule morphology with patient symptoms from femoroacetabular impingement.

The relationship between morphological characteristics of the hip capsule and patient symptoms in the setting of femoroacetabular impingement (FAI) is undefined. In this study, patients with symptomatic FAI prospectively underwent 3T magnetic resonance (MR) imaging of the affected hip and completed the hip disability and osteoarthritis outcome score (HOOS) to determine the correlation between hip capsule anatomy and patient symptoms. Anterior hip capsule volume, posterior capsule volume, anterior-posterior capsule volume ratio, and proximal-distal volume ratio in the anterior capsule were quantified and measured using axial-oblique intermediate-weighted 3D fast spin echo MR images. A total of 35 patients (35 hips) were included for analysis (mean age: 30.6 years; mean body mass index [BMI]: 24.9 kg/m2 ; 57% male). The mean alpha angle was 62.2° ± 4.7°, the mean anterior hip capsule volume was 1705.1 ± 450.3 mm3 , the mean posterior hip capsule volume was 1284.8 ± 268.5 mm3 , the mean anterior to posterior capsule volume ratio was 1.1 ± 0.39, and the mean proximal to distal volume ratio of the anterior capsule was 0.65 ± 0.28. There was no correlation between age, gender, or BMI, and any hip capsule characteristics. Worse scores on the HOOS pain scale were correlated with increased anterior to posterior volume ratio (r = -.38; 95% confidence interval: -0.06 to -0.63). In conclusion, hip capsule morphology correlates with patient symptoms in the setting of FAI as increased anterior capsular volume, relative to posterior capsular volume, is associated with greater patient pain.

T2-relaxation mapping and fat fraction assessment to objectively quantify clinical activity in thyroid eye disease: an initial feasibility study.

Imaging in thyroid eye disease (TED) is used to exclude other diagnoses, assess for apical crowding and plan surgery. But to quantify TED activity objectively, subjective clinical scoring assessments remain the norm. Magnetic resonance imaging (MRI) T2-relaxation times correlate with extra-ocular muscle (EOM) inflammation, but are confounded by signal from fat. We investigated whether T2-relaxation mapping in combination with fat fraction (FF) measurements could quantify disease activity in EOMs objectively. Sixty-two TED patients and six controls were enroled for coronal short tau inversion recovery (STIR), T2 multi-echo fast-spin echo and multi-echo fast-gradient echo MRI of the orbits. STIR signal intensity ratios (SIRs), T2-relaxation times and percentage FF were derived for inferior, lateral, superior and medial recti bilaterally. Twelve patients were re-scanned following immunosuppressive treatment. The results found a positive correlation for all subjects between T2 and SIR (p < 0.001), but only mean T2 differed significantly between patients and controls (p < 0.001). We measured FF in EOMs for the first time and found it greater in TED (p < 0.001). There was also a significant reduction in mean T2 after treatment, with a corresponding reduction in the clinical activity score (CAS) in almost all patients. We show that T2-relaxation times differentiate between normal and inflamed EOMs and are responsive to treatment. Combined, uniquely, with FF measurement in EOMs, an objective, quantitative marker of inflammation in TED-affected muscles could be derived. T2-relaxation times mirrored improvements in CAS after treatment, occasionally preceding them. Rarely, they diverged, suggesting limitations in the CAS as a disease burden marker.

Extraocular muscle sampled volume in Graves' orbitopathy using 3-T fast spin-echo MRI with iterative decomposition of water and fat sequences.

BackgroundCurrent magnetic resonance imaging (MRI) techniques for measuring extraocular muscle (EOM) volume enlargement are not ideally suited for routine follow-up of Graves’ ophthalmopathy (GO) because the difficulty of segmenting the muscles at the tendon insertion complicates and lengthens the study protocol.PurposeTo measure the EOM sampled volume (SV) and assess its correlation with proptosis.Material and MethodsA total of 37 patients with newly diagnosed GO underwent 3-T MRI scanning with iterative decomposition of water and fat (IDEAL) sequences with and without contrast enhancement. In each patient, the three largest contiguous coronal cross-sectional areas (CSA) on the EOM slices were segmented using a polygon selection tool and then summed to compute the EOM-SV. Proptosis was evaluated with the Hertel index (HI). The relationships between the HI value and EOM-SV and between HI and EOM-CSA were compared and assessed with Pearson’s correlation coefficient and the univariate regression coefficient. Inter-observer and intra-observer variability were calculated.ResultsHI showed a stronger correlation with EOM-SV (P < 0.001; r = 0.712, r2 = 0.507) than with EOM-CSA (P < 0.001; r = 0.645 and r2 = 0.329). The intraclass correlation coefficient indicated that the inter-observer agreement was high (0.998). The standard deviation between repeated measurements was 1.9–5.3%.ConclusionIDEAL sequences allow for the measurement EOM-SV both on non-contrast and contrast-enhanced scans. EOM-SV predicts proptosis more accurately than does EOM-CSA. The measurement of EOM-SV is practical and reproducible. EOM-SV changes of 3.5–8.3% can be assumed to reflect true volume changes.

Patellar tendon enthesis abnormalities and their association with knee pain and structural abnormalities in older adults

Purpose: The patellar tendon works together with the quadriceps tendon to enable knee flexion. Its attachment site (enthesis) is at risk of micro damage and degeneration. Recent studies suggest that enthesis abnormalities are associated with development of osteoarthritis through the synovio-entheseal complex. However, no studies have assessed the presence of patellar enthesis abnormalities in older adults and its association with osteoarthritis outcomes. Therefore, we aimed to describe associations between presence of patellar tendon enthesis (PTE) abnormalities visible on magnetic resonance (MR) images at baseline and knee pain, physical function limitations, and osteoarthritic structural abnormalities both cross-sectionally and longitudinally over 10.7 years. Methods: Patellar tendon enthesis abnormalities, defined as presence of abnormal bone signal and/or bone erosion were measured on T2-weighted fat suppressed fast spin echo MR images at baseline in 961 community-dwelling older adults. Knee pain and physical function limitation score were assessed using WOMAC at baseline and 10.7 years. Tibial, femoral, and patella bone marrow lesions (BMLs), cartilage volume and cartilage defects were assessed at baseline and 10.7 years, tibial bone area at baseline and 2.7 years, and infrapatellar fat pad area at baseline using validated methods. Associations were assessed using hurdle, log binomial, linear, and mixed models, after adjusting for confounders. Results: 20% of participants had bone signal and/or erosion at PTE. Cross-sectionally, presence of PTE abnormalities were associated with greater intensity of pain while going up and down stairs (β = 0.22 (95% CI; 0.03, 0.41)), greater risk of having a femoral (RR = 1.46 (1.22, 1.90)) BML, greater lateral tibial bone area (β = 25.95 (1.00, 50.91)), smaller infrapatellar fat pad area (β = −0.26 (−0.46, −0.05)), and a worse tibial cartilage defect score (RR = 1.70 (1.16, 2.47), after adjustment for age, sex, BMI, and structural confounders. Longitudinally, presence of PTE abnormalities at baseline predicted an increased risk of deleterious changes in tibial BML size (RR = 1.52 (1.12, 2.05)) only over 10.7 years but not pain or other structural changes. Conclusions: Patellar tendon enthesis abnormalities are common in the elderly. The presence of cross-sectional but not longitudinal associations suggests they commonly co-exist with other knee structural abnormalities. This suggests they may not be a major player in symptom development or structural changes with the exception of tibial BMLs.

Magnetic Resonance Imaging T2 Values of Stifle Articular Cartilage in Normal Beagles.

The purpose of this study was to evaluate regional differences of canine stifle articular cartilage using the quantitative magnetic resonance imaging (MRI) technique of T2 mapping. Fourteen stifle joints from seven juvenile male Beagle dogs with no evidence or prior history of pelvic limb lameness were imaged ex vivo using standard of care fast spin echo MRI and quantitative T2 mapping protocols. Regions of interest were compared between the femoral, patellar and tibial cartilages, as well as between the lateral and medial femorotibial compartments. Limbs were processed for histology with standard stains to confirm normal cartilage. The average T2 value of femoral trochlear cartilage (37.5 ± 2.3 ms) was significantly prolonged (p < 0.0001) as compared with the femoral condylar, patellar and tibial condylar cartilages (33.1 ± 1.5 ms, 32.8 ± 2.3 ms, and 28.0 ± 1.7 ms, respectively). When comparing medial and lateral condylar compartments, the lateral femoral condylar cartilage had the longest T2 values (34.8 ± 2.8 ms), as compared with the medial femoral condylar cartilage (30.9 ± 1.9 ms) and lateral tibial cartilage (29.1 ± 2.3 ms), while the medial tibial cartilage had the shortest T2 values (26.7 ± 2.4 ms). As seen in other species, regional differences in T2 values of the canine stifle joint are identified. Understanding normal regions of anticipated prolongation in different joint compartments is needed when using quantitative imaging in models of canine osteoarthritis.

High resolution hemodynamic profiling of murine arteriovenous fistula using magnetic resonance imaging and computational fluid dynamics

BackgroundArteriovenous fistula (AVF) maturation failure remains a major cause of morbidity and mortality in hemodialysis patients. The two major etiologies of AVF maturation failure are early neointimal hyperplasia development and persistent inadequate outward remodeling. Although hemodynamic changes following AVF creation may impact AVF remodeling and contribute to neointimal hyperplasia development and impaired outward remodeling, detailed AVF hemodynamics are not yet fully known. Since murine AVF models are valuable tools for investigating the pathophysiology of AVF maturation failure, there is a need for a new approach that allows the hemodynamic characterization of murine AVF at high resolutions.MethodsThis methods paper presents a magnetic resonance imaging (MRI)-based computational fluid dynamic (CFD) method that we developed to rigorously quantify the evolving hemodynamic environment in murine AVF. The lumen geometry of the entire murine AVF was reconstructed from high resolution, non-contrast 2D T2-weighted fast spin echo MRI sequence, and the flow rates of the AVF inflow and outflow were extracted from a gradient echo velocity mapping sequence. Using these MRI-obtained lumen geometry and inflow information, CFD modeling was performed and used to calculate blood flow velocity and hemodynamic factors at high resolutions (on the order of 0.5 μm spatially and 0.1 ms temporally) throughout the entire AVF lumen. We investigated both the wall properties (including wall shear stress (WSS), wall shear stress spatial gradient, and oscillatory shear index (OSI)) and the volumetric properties (including vorticity, helicity, and Q-criterion).ResultsOur results demonstrate increases in AVF flow velocity, WSS, spatial WSS gradient, and OSI within 3 weeks post-AVF creation when compared to pre-surgery. We also observed post-operative increases in flow disturbances and vortices, as indicated by increased vorticity, helicity, and Q-criterion.ConclusionsThis novel protocol will enable us to undertake future mechanistic studies to delineate the relationship between hemodynamics and AVF development and characterize biological mechanisms that regulate local hemodynamic factors in transgenic murine AVF models.

Cross-Sectional and Longitudinal Associations Between Serum Levels of High-Sensitivity C-Reactive Protein, Knee Bone Marrow Lesions, and Knee Pain in Patients With Knee Osteoarthritis.

To describe associations between serum high-sensitivity C-reactive protein (hsCRP), knee bone marrow lesions (BMLs), and knee pain, cross-sectionally and longitudinally, in patients with knee osteoarthritis (OA). Patients (n = 192) with symptomatic knee OA (mean age 63 years, range 50-79, women 53%) were assessed at baseline and after 24 months. Serum hsCRP was measured using enzyme-linked immunosorbent assay. Knee BMLs were scored using the modified Whole-Organ Magnetic Resonance Imaging (MRI) Score from T2-weighted fat-supressed fast spin-echo MRI. Knee pain was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index. Quartiles of baseline serum hsCRP were associated with the presence of knee BMLs (prevalence ratio 1.07 per quartile [95% confidence interval (95% CI) 1.00, 1.15]) and total knee pain scores (β 13.66 per quartile [95% CI 2.26, 25.07]) in multivariable analyses. Longitudinally, higher baseline hsCRP was associated with an increase in BML score (risk ratio 1.37 per quartile [95% CI 1.10, 1.70]), and change in hsCRP was positively associated with change in BML score (β 0.19 [95% CI 0.05, 0.34]) in adjusted analyses. Baseline hsCRP was not associated with change in total knee pain, but change in hsCRP was positively and significantly associated with change in total knee pain (β 4.71 [95% CI 0.48, 8.94]). This became nonsignificant after adjustment for changes in BML score. In patients with knee OA, serum hsCRP is associated with knee BML scores and, to a lesser extent, pain both cross-sectionally and longitudinally, suggesting that inflammation is linked with BMLs and their associated pain.

Can Signal Abnormalities Detected with MR Imaging in Knee Articular Cartilage Be Used to Predict Development of Morphologic Cartilage Defects? 48-Month Data from the Osteoarthritis Initiative.

Purpose To determine the incidence with which morphologic articular cartilage defects develop over 48 months in cartilage with signal abnormalities at baseline magnetic resonance (MR) imaging in comparison with the incidence in articular cartilage without signal abnormalities at baseline. Materials and Methods The institutional review boards of all participating centers approved this HIPAA-compliant study. Right knees of 90 subjects from the Osteoarthritis Initiative (mean age, 55 years ± 8 [standard deviation]; 51% women) with cartilage signal abnormalities but without morphologic cartilage defects at 3.0-T MR imaging and without radiographic osteoarthritis (Kellgren-Lawrence score, 0-1) were frequency matched for age, sex, Kellgren-Lawrence score, and body mass index with right knees in 90 subjects without any signal abnormalities or morphologic defects in the articular cartilage (mean age, 54 years ± 5; 51% women). Individual signal abnormalities (n = 126) on intermediate-weighted fast spin-echo MR images were categorized into four subgrades: subgrade A, hypointense; subgrade B, inhomogeneous; subgrade C, hyperintense; and subgrade D, hyperintense with swelling. The development of morphologic articular cartilage defects (Whole-Organ MR Imaging Score ≥2) at 48 months was analyzed on a compartment level and was compared between groups by using generalized estimating equation logistic regression models. Results Cartilage signal abnormalities were more frequent in the patellofemoral joint than in the tibiofemoral joint (59.5% vs 39.5%). Subgrade A was seen more frequently than were subgrades C and D (36% vs 22%). Incidence of morphologic cartilage defects at 48 months was 57% in cartilage with baseline signal abnormalities, while only 4% of compartments without baseline signal abnormalities developed morphologic defects at 48 months (all compartments combined and each compartment separately, P < .01). The development of morphologic defects was not significantly more likely in any of the subgrades (P = .98) and was significantly associated with progression of bone marrow abnormalities (P = .002). Conclusion Knee cartilage signal abnormalities detected with MR imaging are precursors of morphologic defects with osteoarthritis and may serve as imaging biomarkers with which to assess risk for cartilage degeneration. (©) RSNA, 2016.

Temporal bone congenital anomalies and variatons

Background: We aimed to review the imaging findings of the most common congenital anomalies of the temporal bone and variations of the anatomic landmarks. Material and methods: We retrospectively reviewed the 1 , 894 temporal bone computed tomography (CT) and 986 temporal bone magnetic resonance imaging (MRI) with regard to congenital anomaly and accompanying pathologies. Thin-section CT and thin-section T2-weighted gradient echo or fast spin-echo MRI was performed to identify malformations. The cases were admitted to our hospital with hearing loss, tinnitus, vertigo and non-specific infection complaints. Results: We detected 22 cases with a temporal anomaly among 1,894 temporal CT and 986 temporal MRI images. We discussed the most common congenital anomalies of the temporal bone with imaging findings of our cases. Conclusion: This clinical/imaging review illustrates and reviews congenital abnormalities of the temporal bone: external, middle, and inner ear anomalies, vascular malformations, and variations in high-resolution CT and MR images.

Are 3D FSE MRI sequences of the knee at 1.5 T effective in the detection of meniscal and ligament tears? How useful are they?

Radiol Bras. 2016 Mar/Abr;49(2):V–VI The use of fast spin-echo (FSE) magnetic resonance imaging (MRI) sequences is the most versatile way of evaluating the musculoskeletal system. Anisotropic, two-dimensional (2D) sequences have greater resolution in the acquisition plane whereas the voxel resolution in isotropic three-dimensional (3D) volumetric sequences is the same in all planes with no loss of spatial resolution and with no distortion. Initially, 3D gradient-echo sequences which had acceptable acquisition time and high resolution but inadequate tissue contrast were the standard for evaluating the musculoskeletal system. As of 2007, technological advances led to more consistent use of 3D FSE sequences in such evaluations, because 3D FSE sequences provide greater tissue contrast for clinical application in the knee than do 3D gradient-echo sequences. Imaging studies of the knee structures can require the use of oblique planes with special orientation. That is the case of anterior cruciate ligament evaluation, a common situation on the daily practice. In 2007, Rajeswaran et al. highlighted the value of using oblique planes to evaluate the popliteofibular ligament, which plays a role in instability related to lesions of the posterolateral corner structures of the knee. Evaluations of the articular cartilage of the knee can also benefit from the use of 3D isotropic volumetric sequences due to its capacity to reformat in different planes and its greater spatial resolution which improves the characterization of cartilagineous lesions. This last characteristic has a particular application in the femoral trochlea. The articular cartilage evaluation in this area, using axial planes with the usual angulation, has certain limitations. The sagittal plane is called in order to complement this evaluation, although it can be less precise due to partial volume effects. Para-axial slices, perpendicular to the articular surface of the trochlea, can better define injury in this area. Regarding the detection of ligament and meniscal injuries, the performance of volumetric sequences is similar to that of 2D sequences, although the quality of 3D images is considered inferior to that of 2D images. Although some authors question the real value of 3D FSE sequences for the diagnosis of meniscal and cartilaginous lesions in

Contrast-enhanced synthetic MRI for the detection of brain metastases.

BackgroundSynthetic magnetic resonance imaging (MRI), a technique that enables creation of various contrast-weighted images from a single MRI quantification scan, is a useful clinical tool. However, there are currently no reports examining the use of contrast-enhanced synthetic MRI for detecting brain metastases.PurposeTo assess whether contrast-enhanced synthetic MRI is suitable for detecting brain metastases.Material and MethodsTen patients with a combined total of 167 brain metastases who underwent quantitative MRI and conventional T1-weighted inversion recovery fast spin-echo (conventional T1IR) MRI before and after administration of a contrast agent were included in the study. Synthetic T1IR and T1-weighted (synthetic T1W) images were produced after parameter quantification. Lesion-to-white matter contrast and contrast-to-noise ratio were calculated for each image. The number of visible lesions in each image was determined by two neuroradiologists.ResultsThe mean lesion-to-white matter contrast and mean contrast-to-noise ratio of the synthetic T1IR images were significantly higher than those of the synthetic T1W (P < 0.001 and P < 0.001, respectively) and conventional T1IR (P = 0.04 and P = 0.002, respectively) images. Totals of 130 and 124 metastases were detected in the synthetic T1IR images by the first and second radiologists, respectively. The corresponding numbers were 91 and 85 in the synthetic T1W images and 119 and 119 in the conventional T1IR images. Statistical significance was not found among detected numbers of lesions.ConclusionSynthetic T1IR imaging created better contrast compared with synthetic T1W or conventional T1IR imaging. The ability to detect brain metastases was comparable among these imaging.