Axial T2-weighted Spin-echo Images Research Articles

Correction of Motion Artifacts Using a Multiscale Fully Convolutional Neural Network.

Motion artifacts are a frequent source of image degradation in the clinical application of MR imaging (MRI). Here we implement and validate an MRI motion-artifact correction method using a multiscale fully convolutional neural network. The network was trained to identify motion artifacts in axial T2-weighted spin-echo images of the brain. Using an extensive data augmentation scheme and a motion artifact simulation pipeline, we created a synthetic training dataset of 93,600 images based on only 16 artifact-free clinical MRI cases. A blinded reader study using a unique test dataset of 28 additional clinical MRI cases with real patient motion was conducted to evaluate the performance of the network. Application of the network resulted in notably improved image quality without the loss of morphologic information. For synthetic test data, the average reduction in mean squared error was 41.84%. The blinded reader study on the real-world test data resulted in significant reduction in mean artifact scores across all cases (P < .03). Retrospective correction of motion artifacts using a multiscale fully convolutional network is promising and may mitigate the substantial motion-related problems in the clinical MRI workflow.

Predicting Carotid Plaque Characteristics Using Quantitative Color-Coded T1-Weighted MR Plaque Imaging: Correlation with Carotid Endarterectomy Specimens

MR plaque imaging is used to evaluate the risk of embolic complications during carotid endarterectomy and carotid artery stent placement. However, its performance for characterizing intraplaque components has varied across studies and is generally suboptimal. Hence, we correlated MR imaging results with histologic findings to determine whether a combination of high-contrast T1-weighted imaging and quantitative image analysis could readily determine plaque characteristics. We prospectively examined 40 consecutive patients before carotid endarterectomy by using a 1.5T scanner and axial T1-weighted spin-echo images under optimized scanning conditions. The percentage areas of intraplaque fibrous tissue, lipid/necrosis, and hemorrhage were calculated automatically by using the software with previously reported cutoff values and were compared with those of the specimens. The thickness of the fibrous cap was also measured manually. The percentage areas of fibrous, lipid/necrotic, and hemorrhagic components were 5.7%-98.7%, 1.3%-65.7%, and 0%-82.0%, respectively, as determined by the MR images, whereas the corresponding values were 4.8%-92.3%, 7.0%-93.8%, and 0%-70.4%, respectively, as determined by histologic examination. Significant positive correlation and agreement were observed between MR images and histologic specimens (r = 0.92, 0.79, and 0.92; intraclass correlation coefficients = 0.91, 0.67, and 0.89; respectively). Thickness of the fibrous caps on MR images (0.21-0.87 mm) and in the specimens (0.14-0.83 mm) also showed positive correlation and agreement (r = 0.61, intraclass correlation coefficient = 0.59). Quantitative analysis of high-contrast T1-weighted images can accurately evaluate the composition of carotid plaques in carotid endarterectomy candidates.

Validation of Dual Energy X-Ray Absorptiometry Measures of Abdominal Fat by Comparison with Magnetic Resonance Imaging in an Indian Population

ObjectiveAbdominal adiposity is an important risk factor for diabetes and cardiovascular disease in Indians. Dual energy X-ray absorptiometry (DXA) can be used to determine abdominal fat depots, being more accessible and less costly than gold standard measures such as magnetic resonance imaging (MRI). DXA has not been fully validated for use in South Asians. Here, we determined the accuracy of DXA for measurement of abdominal fat in an Indian population by comparison with MRI.Design146 males and females (age range 18–74, BMI range 15–46 kg/m2) from Hyderabad, India underwent whole body DXA scans on a Hologic Discovery A scanner, from which fat mass in two abdominal regions was calculated, from the L1 to L4 vertebrae (L1L4) and from the L2 to L4 vertebrae (L2L4). Abdominal MRI scans (axial T1-weighted spin echo images) were taken, from which adipose tissue volumes were calculated for the same regions.ResultsIntra-class correlation coefficients between DXA and MRI measures of abdominal fat were high (0.98 for both regions). Although at the level of the individual, differences between DXA and MRI could be large (95% of DXA measures were between 0.8 and 1.4 times MRI measures), at the sample level, DXA only slightly overestimated MRI measures of abdominal fat mass (mean difference in L1L4 region: 2% (95% CI:0%, 5%), mean difference in L2L4 region:4% (95% CI: 1%, 7%)). There was evidence of a proportional bias in the association between DXA and MRI (correlation between difference and mean −0.3), with overestimation by DXA greater in individuals with less abdominal fat (mean bias in leaner half of sample was 6% for L1L4 (95%CI: 2, 11%) and 7% for L2L4 (95% CI:3,12%).ConclusionsDXA measures of abdominal fat are suitable for use in Indian populations and provide a good indication of abdominal adiposity at the population level.

Topography mapping of whole body adipose tissue using A fully automated and standardized procedure

To obtain quantitative measures of human body fat compartments from whole body MR datasets for the risk estimation in subjects prone to metabolic diseases without the need of any user interaction or expert knowledge. Sets of axial T1-weighted spin-echo images of the whole body were acquired. The images were segmented using a modified fuzzy c-means algorithm. A separation of the body into anatomic regions along the body axis was performed to define regions with visceral adipose tissue present, and to standardize the results. In abdominal image slices, the adipose tissue compartments were divided into subcutaneous and visceral compartments using an extended snake algorithm. The slice-wise areas of different tissues were plotted along the slice position to obtain topographic fat tissue distributions. Results from automatic segmentation were compared with manual segmentation. Relatively low mean deviations were obtained for the class of total tissue (4.48%) and visceral adipose tissue (3.26%). The deviation of total adipose tissue was slightly higher (8.71%). The proposed algorithm enables the reliable and completely automatic creation of adipose tissue distribution profiles of the whole body from multislice MR datasets, reducing whole examination and analysis time to less than half an hour.

Postural Changes of the Dural Sac in the Lumbar Spines of Asymptomatic Individuals Using Positional Stand-Up Magnetic Resonance Imaging

Positional magnetic resonance imaging (MRI) study of control subjects. To determine dimensional changes in the lumbar dural sac as a function of posture, and to establish changes between the supine, erect and seated positions. Studies using computerized tomography and MRI were done to determine the mechanical effects on the lumbar spinal canal in the different positions. There has been no consecutive study, however, in which normal individuals were investigated for positional changes of the dural sac, including true standing position. Thirty-two male asymptomatic volunteers were recruited. The examination was performed using a new MRI system. All subjects were examined with sagittal T2 and axial T1-weighted spin-echo images. The subjects were studied in the supine, standing, and sitting positions. The measurements were made using OSIRIS software (Digital Imaging Unit University Hospital of Geneva, Geneva, Switzerland). On axial images, dural sac cross-sectional area and anteroposterior (AP) dural sac diameter were measured at the level of the L3/4, L4/5, and L5/S1 discs. On midsagittal images, AP dural sac diameter and the upper-endplate angles of L1 and S1 were measured. We found a disc degeneration or disc protrusion in 41% (12/29) of the subjects, but there was no obvious compression of the dural sac. Depending on the postures, the mean dural sac cross-sectional area and AP dural sac diameter changed. At all levels, mean dural sac cross-sectional area in the supine position was significantly smaller than in other postures. The dural area decreased most at the L5/S1 level due to positional change from standing to supine. The largest dural area at the L5/S1 level was in sitting extended. AP dural sac diameter on axial and midsagittal images showed a similar tendency. A significant posture-dependent difference of the dural sac cross-sectional area at the level of intervertebral disc in asymptomatic volunteers has been demonstrated. When the posture changed from supine to standing position, lumbar dural sac volume expanded by the increased pressure of cerebrospinal fluid, and the dural sac cross-sectional area increased. The smallest values were found in the supine position.

Patterns of gadopentetate-enhanced MR imaging of radiocarpal joints of healthy subjects.

The aim of our study was to evaluate prospectively the grades and patterns of gadopentetate-enhanced MR imaging in the radiocarpal joints of healthy subjects after IV contrast administration. The study included 18 healthy subjects (nine men, nine women; age range, 24-34 years; mean age, 30.8 years). We obtained coronal T1-weighted spin-echo images with fat suppression before and after IV administration of gadopentetate dimeglumine and additional axial T1-weighted spin-echo images after contrast administration. Patterns of signal-intensity enhancement in and around the radiocarpal joints were evaluated qualitatively and quantitatively. In eight (44.4%) of 18 healthy subjects, enhancement of the radiocarpal joints was seen and exclusively located in the region of the prestyloid recess. Enhancement patterns were bandlike in three (16.7%) of 18 healthy subjects, homogeneous in another three (16.7%) of 18, and nodular in two (11.1%) of 18. After IV administration of gadopentetate, signal-intensity enhancement in the radiocarpal joint is frequently seen in healthy subjects and is not predictive of inflammatory joint disease. If contrast enhancement is present, three distinct patterns are usually revealed, all invariably located in the region of the prestyloid recess.

Hippocampal sclerosis: correlation of MR imaging findings with surgical outcome.

ObjectiveAtrophy and a high T2 signal of the hippocampus are known to be the principal MR imaging findings of hippocampal sclerosis. The purpose of this study was to determine whether or not individual MRI findings correlate with surgical outcome in patients with this condition.Materials and MethodsPreoperative MR imaging findings in 57 consecutive patients with pathologically-proven hippocampal sclerosis who underwent anterior temporal lobectomy and were followed-up for 24 months or more were retrospectively reviewed, and the results were compared with the postsurgical outcome (Engel classification). The MR images included routine sagittal T1-weighted and axial T2-weighted spin-echo images, and oblique coronal T1-weighted 3D gradient-echo and T2-weighted 2D fast spin-echo images obtained on either a 1.5 T or 1.0 T unit. The images were visually evaluated by two neuroradiologists blinded to the outcome; their focus was the presence or absence of atrophy and a high T2 hippocampal signal.ResultsHippocampal atrophy was seen in 96% of cases (55/57) [100% (53/53) of the good outcome group (Engel class I and II), and 50% (2/4) of the poor outcome group (class III and IV)]. A high T2 hippocampal signal was seen in 61% of cases (35/57) [62% (33/53) of the good outcome group and 50% (2/4) of the poor outcome group]. All 35 patients with a high T2 signal had hippocampal atrophy. 'Normal' hippocampus, as revealed by MR imaging, occurred in 4% of patients (2/57), both of whom showed a poor outcome (Engel class III). The presence or absence of hippocampal atrophy correlated well with surgical outcome (p<0.01). High T2 signal intensity did not, however, significantly correlate with surgical outcome (p>0.05).ConclusionCompared with a high T2 hippocampal signal, hippocampal atrophy is more common and correlates better with surgical outcome. For the prediction of this, it thus appears to be the more useful indicator.

MR Appearance of Metastatic Melanotic Melanoma in the Breast: Case Reports

A 34-year-old Chinese woman complaining of multiple breast lumps was referred to a local Breast Clinic. She had malignant melanoma of the left middle finger and amputation had been performed 3 months earlier. Fine needle aspiration was performed on two of the breast lumps and they were diagnosed as melanotic melanoma. The pleomorphic malignant cells were immunoreactive for S100 protein and HMB 45. Ultrasound (US) was later performed which showed more than five well circumscribed hypoechoic masses, ranging in size from 0.5 to 1.5 cm, in both breasts. Mammography was performed, which showed three medium density well circumscribed masses in the right breast. There was no axillary adenopathy. Magnetic resonance imaging (MRI) of both breasts was performed with a 1.5T superconductive MR imager (Signa Advantage, GE Medical Systems, Milwaukee, U.S.A.) and a bilateral phased array breast coil. Pre-contrast medium axial T1-weighted spin-echo (TR/TE 1⁄4 500/12) with fat saturation and sagittal T2-weighted fast spin-echo (TR/TE 1⁄4 3440/126, ETL 1⁄4 12) images were acquired with 4 mm thick sections, 1 mm gap, a 256 × 192 matrix and two excitations. After intravenous administration of gadopentetate dimeglumine (0.2 mmol/kg), fat-suppressed axial T1-weighted spinecho images were taken. There were more than five abnormal masses in both breasts, ranging in size from 0.5 to 1.5 cm. The masses yielded high signal on T1-weighted (Fig. 1), low signal on T2-weighted (Fig. 2) and showed decreased signal intensity after contrast medium injection (Fig. 3). In the clinical work-up, there was no evidence of other metastases. Bilateral mastectomy was performed. A specimen photograph was taken (Fig. 4) and MRI was performed (Fig. 5). The patient was followed-up in the Breast Clinic.

Deep cerebral venous thrombosis: imaging in eight cases.

Deep cerebral venous thrombosis (DCVT) is a rare, potentially fatal disease. We carried out a retrospective analysis of eight patients presenting with DCVT, using CT and MRI data. Digital subtraction angiography (DSA), MR angiography (MRA) (2D phase-contrast), and angiography were performed in four, four and two patients, respectively. Direct (venous abnormalities) and indirect (parenchymatous involvement) signs of thrombosis were assessed. Follow-up MRI and MRA were performed on two patients. CT was initially normal in two patients, demonstrated a "cord sign" in deep veins in five and deep venous infarcts in three. When performed within a week of admission (seven patients), MRI showed thrombosis as into intense or high signal in deep veins on sagittal T1-weighted spin-echo images in all patients, and on axial T2-weighted spin-echo images in two. Deep venous infarcts were found in five patients. Direct or indirect signs of sagittal or lateral sinus thrombosis were present on CT in two patients and on MRI in five. CT angiography, MRA and DSA were concordant with MRI findings. CT venography showed persistent flow in thrombosed veins. MRI follow-up demonstrated progressive deep venous recanalisation.

Magnetresonanztomographie ohne und mit Gadolinium-DTPA zur Beurteilung von Nierentransplantaten

To determine the value of MR imaging in differentiating the various causes of human renal allograft dysfunction. A total of 123 human renal allografts (normal n = 20, acute rejection n = 57, acute tubular necrosis n = 14, interstitial fibrosis n = 11, chromic allograft glomerulopathy n = 11, cyclosporine nephrotoxicity n = 3, cortical necrosis n = 7) were investigated by means of MR imaging. Axial T1-weighted spin-echo images and coronal T1-weighted gradient-echo images were obtained before and after Gd-DTPA injection. Diagnostic parameters included corticomedullary contrast and allograft size and shape on the pre-contrast sequences. None of the diagnostic parameters used could differentiate among the various diagnostic groups. Diagnostic of cortical necrosis could be made only on post-contrast scans. Contrast-enhanced scans were superior to pre-contrast images in detection of focal allograft lesions. Otherwise, contrast-enhanced scans did not provide any more information than pre-contrast studies. Spin-echo and gradient-echo sequences displayed the same diagnostic value. MR imaging has a limited value in differentiating the various causes of renal allograft dysfunction.

T2-weighted and dynamic enhanced MRI in acute pancreatitis: Comparison with contrast enhanced CT

The purpose of this study was to compare T2-weighted and dynamic contrast enhanced MRI with contrast enhanced CT in patients with severe acute pancreatitis. Thirty-two patients were examined using axial T2-weighted spin-echo imaging (TR 1801, TE 15/90) and a multi-slice rapid gradient-echo sequence (TR 135, TE 4, FA 80 degrees) (FLASH) in axial and coronal planes. Fifteen 5 mm axial slices at 10 mm intervals were acquired during a single breath-hold of 19 s before, and at 10 and 40 s after a bolus injection of Gd-DTPA. Additional FLASH images in the coronal plane were obtained 2 min after injection of contrast medium. MR was compared with contemporary enhanced CT by two blinded observers who scored pancreatic viability and the content of intra and extra-pancreatic fluid collections. The presence of gas, calcification and haemorrhage was noted. Abnormalities in adjacent organs, evidence of vascular occlusion and indicators of aetiology were also recorded. MR and CT were concordant in distinguishing viable pancreatic tissue from areas of necrosis. MR appeared to be more effective than CT in characterizing the content of fluid collections and in demonstrating gall stones, although CT remains superior in detecting flecks of gas and calcification. MR carries some advantages over CT and can be regarded as an alternative primary technique in patients with severe pancreatitis.

Efficacy of MR imaging in patients suspected of having Morton's neuroma.

The purpose of our study was to evaluate the role of MR imaging in patients with suspected Morton's neuroma and to assess the value of various MR sequences in this diagnosis. Thirty-two consecutive patients with suspected Morton's neuroma were studied using a 1.0-T MR scanner. Axial T1- and T2-weighted spin-echo, short inversion time inversion recovery, and enhanced T1-weighted fat-suppressed spin-echo images were obtained on each patient. Eighteen intermetatarsal spaces in 16 of the 32 patients were evaluated surgically. Contrast-to-noise ratios for Morton's neuroma versus surrounding fat were calculated and standardized for imaging times. In 15 of 18 intermetatarsal spaces, a Morton's neuroma was surgically proven. Thirteen true-positive, two false-negative, three true-negative, and no false-positive MR diagnoses were given. In six of 15 proven neuromas, the clinical examiner was not able to identify the correct intermetatarsal space. The MR diagnoses in the 16 remaining patients who did not undergo surgery were Morton's neuroma (n = 8), stress fracture (n = 1), foreign body reaction (n = 1), tendon sheath ganglion (n = 1), postoperative changes (n = 2), and no abnormality (n = 3). Standardized contrast-to-noise ratios (+/- SD) were 2.42 +/- 0.72 for T1-weighted images; 1.43 +/- 1.13 for T2-weighted images; 1.26 +/- 1.47 for short inversion time inversion recovery images; and 0.83 +/- 0.59 gadolinium-enhanced fat-suppressed images. The differences were statistically significant for the T1-weighted spin-echo images versus the three other sequences (p = .001-.018), but not among the other sequences (p = .209-.710). MR imaging is accurate in diagnosing Morton's neuroma and may be important for correct localization. A limited examination employing axial T1-weighted spin-echo images is adequate; additional sequences should be employed only for differential diagnosis.

Spinal cord ependymomas: MR imaging features.

To assess the magnetic resonance (MR) imaging characteristics of spinal intramedullary ependymomas. MR images obtained in 25 patients (aged 12-73 years) with proved intramedullary ependymomas were retrospectively reviewed. T1- and T2-weighted images were obtained in all patients. Gadopentetate dimeglumine was intravenously administered in 23 patients; enhanced sagittal and axial T1-weighted spin-echo images were reviewed. All tumors had hyperintense signal on T2-weighted images. In the 23 patients who received contrast material, all tumors became enhanced; enhancement was heterogeneous in 15 patients and homogeneous in eight patients. Twenty tumors had sharply defined, enhanced borders. Nineteen tumors were centrally located in the spinal cord. A hypointense rim on T2-weighted images was noted in five patients. Intramedullary ependymomas become enhanced after administration of gadopentetate dimeglumine; the enhanced borders are usually sharply marginated. They are characteristically located centrally in an expanded spinal cord. Hemosiderin is often present at the periphery of cervical ependymomas.

MR imaging of the liver: breath-hold T1-weighted MP-GRE compared with conventional T2-weighted SE imaging--lesion detection, localization, and characterization.

To compare breath-hold T1-weighted magnetization-prepared gradient-echo (MP-GRE) imaging with conventional T2-weighted spin-echo (SE) imaging in evaluation of focal liver disease. Images of 68 patients evaluated for focal liver disease were reviewed. Five sets of images were analyzed: axial, sagittal, and coronal breath-hold T1-weighted MP-GRE images, axial T2-weighted SE images, and a compilation of axial, sagittal, and coronal (three-plane) T1-weighted MP-GRE images. Lesion signal intensity (SI) and signal difference-to-noise (SD/N) ratios were calculated. Lesions were detected, localized, and characterize more accurately (P < .05-.001) and with greater confidence on three-plane T1-weighted MP-GRE images than on almost all single-plane images. Mean SI ratios of nonsolid and solid lesions on MP-GRE and SE images were significantly different at all lesion sizes; mean SD/N ratio was significantly different only for large lesions. Lesion detection, localization, and characterization can be accurately and confidently performed with three-plane T1-weighted MP-GRE breath-hold imaging, potentially obviating conventional T2-weighted SE imaging.

Development of the human cerebellum observed with high-field-strength MR imaging.

A retrospective study of 160 pediatric subjects, aged 32-410 weeks after conception, was conducted to determine the normal developmental patterns of the human cerebellum by means of magnetic resonance (MR) imaging. On the basis of axial T2-weighted spin-echo images (repetition time, 3,000 msec; echo time, 120 msec), which provided the best contrast between gray matter and white matter, five distinct developmental stages were defined. At term, the medial lemnisci as well as the parasagittal cerebellum were myelinated. The appearance of myelin in the middle cerebellar peduncles and the basilar pons preceded that in the corpus medullare of the cerebellum. The normal age ranges for the different stages were defined with statistical analysis. These ranges are applicable to the daily routine of image interpretation. The sequence of myelination in the cerebellum observed at MR imaging correlates with the known patterns observed in pathologic studies but lags behind by an average of 6 months.