Differences between spinal cord injury and cervical compressive myelopathy in intramedullary high-intensity lesions on T2-weighted magnetic resonance imaging: A retrospective study

Increases in aging populations have raised the number of patients with cervical spinal cord injury (SCI) without fractures due to compression of the cervical spinal cord. In such patients, it is necessary to clarify whether SCI or cervical compressive myelopathy (CCM) is the cause of disability after trauma. This study aimed to clarify the differences in magnetic resonance imaging (MRI) features between SCI and CCM. Overall, 60 SCI patients and 60 CCM patients with intramedullary high-intensity lesions on T2-weighted MRI were included in this study. The longitudinal lengths of the intramedullary T2 high-intensity lesions were measured using sagittal MRI sections. Snake-eye appearance on axial sections was assessed as a characteristic finding of CCM. The T2 values of the high-intensity lesions and normal spinal cords at the first thoracic vertebra level were measured, and the contrast ratio was calculated using these values. The longitudinal length of T2 high-intensity lesions was significantly longer in SCI patients than in CCM patients. Snake-eye appearance was found in 26 of the 60 CCM patients, but not in SCI patients. On both the sagittal and axial images, the contrast ratio was significantly higher in the SCI group than in the CCM group. Based on these results, a diagnostic scale was created. This scale made it possible to distinguish between SCI and CCM with approximately 90% accuracy.

Relationship Between Pituitary Siderosis and Endocrinological Disorders in Pediatric Patients with Beta-Thalassemia

Introduction

Excess iron accumulation occurs mainly in organs such as reticuloendothelial cells, the pituitary gland, and the pancreas in beta-thalassemia because of blood transfusions. In the present study, it was aimed to investigate the relationship between T2* values on magnetic resonance imaging (MRI) and clinically diagnosed pituitary endocrinological disorders in children with thalassemia major.

Methods

This study enrolled patients diagnosed with beta-thalassemia at pediatric hematology outpatient clinics. In the study, in addition to the medical history of the patients, routinely performed tests, including hemoglobin electrophoresis, routine biochemical tests, and tests for pubertal development (follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, testosterone, etc.), as well as iron deposition measured by hepatic MRI T2* (STAR) sequence, were retrospectively assessed. A total of 29 patients were enrolled.

Results

Hypothyroidism was detected in 34.6% (9/26) of patients, short stature in 37% (10/27), and pubertal retardation in 50% (14/28) of the patients. There was no significant correlation between hypothyroidism and pituitary MRI T2* values. No significant correlation was found between laboratory parameters and pituitary MRI examination. Although the sensitivity of T2* levels could rise above 80%, their specificity remained low. This is one of the major limitations of the pituitary MR T2* study for the prediction of short stature. The best lower cut-off level of MR T2* to predict short stature was found 14.6 ms.

Conclusion

The diagnostic specificity pituitary MR examination levels for short stature were detected as low. Thus, the clinical standardization and validation of pituitary MR T2* values examination are needed before clinical follow-up and multifaceted studies are needed.

T2 mapping of the heart with a double-inversion radial fast spin-echo method with indirect echo compensation

BACKGROUND

The abnormal signal intensity in cardiac T2-weighted images is associated with various pathologies including myocardial edema. However, the assessment of pathologies based on signal intensity is affected by the acquisition parameters and the sensitivities of the receiver coils. T2 mapping has been proposed to overcome limitations of T2-weighted imaging, but most methods are limited in spatial and/or temporal resolution. Here we present and evaluate a double inversion recovery radial fast spin-echo (DIR-RADFSE) technique that yields data with high spatiotemporal resolution for cardiac T2 mapping.

METHODS

DIR-RADFSE data were collected at 1.5 T on phantoms and subjects with echo train length (ETL) = 16, receiver bandwidth (BW) = ±32 kHz, TR = 1RR, matrix size = 256 × 256. Since only 16 views per echo time (TE) are collected, two algorithms designed to reconstruct highly undersampled radial data were used to generate images for 16 time points: the Echo-Sharing (ES) and the CUrve Reconstruction via pca-based Linearization with Indirect Echo compensation (CURLIE) algorithm. T2 maps were generated via least-squares fitting or the Slice-resolved Extended Phase Graph (SEPG) model fitting. The CURLIE-SEPG algorithm accounts for the effect of indirect echoes. The algorithms were compared based on reproducibility, using Bland-Altman analysis on data from 7 healthy volunteers, and T2 accuracy (against a single-echo spin-echo technique) using phantoms.

RESULTS

Both reconstruction algorithms generated in vivo images with high spatiotemporal resolution and showed good reproducibility. Mean T2 difference between repeated measures and the coefficient of repeatability were 0.58 ms and 2.97 for ES and 0.09 ms and 4.85 for CURLIE-SEPG. In vivo T2 estimates from ES were higher than those from CURLIE-SEPG. In phantoms, CURLIE-SEPG yielded more accurate T2s compared to reference values (error was 7.5-13.9% for ES and 0.6-2.1% for CURLIE-SEPG), consistent with the fact that CURLIE-SEPG compensates for the effects of indirect echoes. The potential of T2 mapping with CURLIE-SEPG is demonstrated in two subjects with known heart disease. Elevated T2 values were observed in areas of suspected pathology.

CONCLUSIONS

DIR-RADFSE yielded TE images with high spatiotemporal resolution. Two algorithms for generating T2 maps from highly undersampled data were evaluated in terms of accuracy and reproducibility. Results showed that CURLIE-SEPG yields T2 estimates that are reproducible and more accurate than ES.

Differences in somatosensory and motor improvement during temporary functional deafferentation in stroke patients and healthy subjects

Temporary functional deafferentation is of interest to become an additional tool in neurorehabilitative treatments. Temporary functional deafferentation is known to improve sensory and motor outcomes in chronic stroke patients and healthy subjects. The present study soughts to indicate differences in the efficiency of pharmacologically induced temporary functional deafferentation between chronic stroke patients and matched healthy subjects. 46 chronic stroke patients and 20 age- and gender-matched healthy subjects were deafferented on one forearm by an anesthetic cream. Somatosensory performance was assessed using von-Frey Hair testing and Grating orientation task; motor performance was assessed by means of a shape-sorter-drum task. Grating orientation task and shape-sorter-drum task were significantly improved during temporary functional deafferentation in stroke patients but not in healthy subjects. Von-Frey Hair testing revealed no improvement of absolute tactile thresholds during temporary functional deafferentation in both groups. Furthermore, the stroke patients showed deficits at baseline measurement in all assessments except the von-Frey Hair test. Temporary functional deafferentation of a forearm by an anesthetic cream results in improvements of motor performance and somatosensory discrimination in stroke patients but not in healthy subjects. Therefore, it is reasonable to test in a next step whether temporary functional deafferentation might become an additional tool in motor rehabilitation of post stroke patients.

Regional variation in T1ρ and T2 times in osteoarthritic human menisci: correlation with mechanical properties and matrix composition

OBJECTIVE

Changes in T1ρ and T2 magnetic resonance relaxation times have been associated with articular cartilage degeneration, but similar relationships for meniscal tissue have not been extensively investigated. This work examined relationships between T1ρ and T2 measurements and biochemical and mechanical properties across regions of degenerate human menisci.

DESIGN

Average T1ρ and T2 relaxation times were determined for nine regions each of seven medial and 13 lateral menisci from 14 total knee replacement patients. Sulfated glycosaminoglycan (sGAG), collagen and water contents were measured for each region. Biomechanical measurements of equilibrium compressive, dynamic compressive and dynamic shear moduli were made for anterior, central and posterior regions.

RESULTS

T1ρ and T2 times showed similar regional patterns, with longer relaxation times in the (radially) middle region compared to the inner and outer regions. Pooled over all regions, T1ρ and T2 times showed strong correlations both with one another and with water content. Correlations with biochemical content varied depending on normalization to wet or dry mass, and both imaging parameters showed stronger correlations with collagen compared to sGAG content. Mechanical properties displayed moderate inverse correlations with increasing T1ρ and T2 times and water content.

CONCLUSION

Both T1ρ and T2 relaxation times correlated strongly with water content and moderately with mechanical properties in osteoarthritic menisci, but not as strongly with sGAG or collagen contents alone. While the ability of magnetic resonance imaging (MRI) to detect early osteoarthritic changes remains the subject of investigation, these results suggest that T1ρ and T2 relaxation times have limited ability to detect compositional variations in degenerate menisci.

Radiofrequency (RF) coil impacts the value and reproducibility of cartilage spin-spin (T2) relaxation time measurements

INTRODUCTION

T2 (spin-spin) relaxation time is frequently used for compositional assessment of articular cartilage. However little is known about the influence of magnetic resonance (MR) system components on these measurements. The reproducibility and range of cartilage T2 values were evaluated using different extremity radiofrequency (RF) coils with potential differences in flip angle uniformity and signal-to-noise ratio (SNR).

METHOD

Ten knees underwent 3 T MR exams using RF coils with different SNR: quadrature transmit/receive (QTR); quadrature transmit/eight-channel phased-array receive (QT8PAR). Each knee was scanned twice per coil (four exams total). T2 values were calculated for the central medial and lateral femoral (cMF, cLF) and medial and lateral tibial (MT, LT) cartilage.

RESULTS

The flip angle varied across a central 40 mm diameter region-of-interest of each coil by <1.5%. However SNR was significantly higher using QT8PAR than QTR (P < 0.001). T2 values for cMF (50.7 msec/45.9 msec) and MT (48.2 msec/41.6 msec) were significantly longer with QT8PAR than QTR (P < 0.05). T2 reproducibility was improved using QT8PAR for cMF and cLF (4.8%/5.8% and 4.1%/6.5%; P < 0.001), similar for LT (3.8%/3.6%; P = 1.0), and worse for MT (3.7%/3.3%; P < 0.001). T2 varied spatially, with cLF having the longest (52.0 msec) and the LT having the shortest (40.6 msec) values. All deep cartilage had significantly longer, and less variable, T2 values using QT8PAR (higher SNR; P < 0.03).

CONCLUSIONS

SNR varied spatially (significant) depending upon coil, but refocusing flip angle only slightly. With higher SNR, significantly longer T2 values were measured for deep (all plates) and global (MT, cMF) cartilage. T2 values varied by depth and plate, in agreement with prior studies.

Magnetic transfer contrast accurately localizes substantia nigra confirmed by histology

BACKGROUND

Magnetic resonance imaging (MRI) has multiple contrast mechanisms. Like various staining techniques in histology, each contrast type reveals different information about the structure of the brain. However, it is not always clear how structures visible in MRI correspond to structures previously identified by histology. The purpose of this study was to determine if magnetic transfer contrast (MTC) or T2 contrast MRI was better at delineating the substantia nigra (SN).

METHODS

MRI scans were acquired in vivo from two nonhuman primates (NHPs). The NHPs were subsequently euthanized, perfused, and their brains sectioned for histologic analyses. Each slice was photographed before sectioning. Each brain was sectioned into approximately 500 sections, 40 μm each, encompassing most of the cortex, midbrain, and dorsal parts of the hindbrain. Levels corresponding to anatomic MRI images were selected. From these, adjacent sections were stained using Kluver-Barrera (myelin and cell bodies) or tyrosine hydroxylase (dopaminergic neurons) immunohistochemistry. The resulting images were coregistered to the block-face images using a moving least squares algorithm with similarity transformations. MR images were similarly coregistered to the block-face images, allowing the structures on MRI to be identified with structures on the histologic images.

RESULTS

We found that hyperintense (light) areas in MTC images were coextensive with the SN as delineated histologically. The hypointense (dark) areas in T2-weighted images were not coextensive with the SN but extended partially into the SN and partially into the cerebral peduncles.

CONCLUSIONS

MTC is more accurate than T2-weighting for localizing the SN in vivo.

T2-based arterial spin labeling measurements of blood to tissue water transfer in human brain

PURPOSE

To investigate blood to tissue water transfer in human brain, in vivo and spatially resolved using a T2-based arterial spin labeling (ASL) method with 3D readout.

MATERIALS AND METHODS

A T2-ASL method is introduced to measure the water transfer processes between arterial blood and brain tissue based on a 3D-GRASE (gradient and spin echo) pulsed ASL sequence with multiecho readout. An analytical mathematical model is derived based on the General Kinetic Model, including blood and tissue compartment, T1 and T2 relaxation, and a blood-to-tissue transfer term. Data were collected from healthy volunteers on a 3 T system. The mean transfer time parameter T(bl → ex) (blood to extravascular compartment transfer time) was derived voxelwise by nonlinear least-squares fitting.

RESULTS

Whole-brain maps of T(bl → ex) show stable results in cortical regions, yielding different values depending on the brain region. The mean value across subjects and regions of interest (ROIs) in gray matter was 440 ± 30 msec.

CONCLUSION

A novel method to derive whole-brain maps of blood to tissue water transfer dynamics is demonstrated. It is promising for the investigation of underlying physiological mechanisms and development of diagnostic applications in cerebrovascular diseases.

Relationship between trabecular bone structure and articular cartilage morphology and relaxation times in early OA of the knee joint using parallel MRI at 3 T

OBJECTIVE

To evaluate trabecular bone structure in relationship with cartilage parameters in distal femur and proximal tibia of the human knee at 3Tesla (3T) using high-resolution magnetic resonance imaging (MRI) with parallel imaging.

METHOD

Sixteen healthy controls and 16 patients with mild osteoarthritis (OA) were studied using a 3T magnetic resonance (MR) scanner and an eight-channel phased-array knee coil. Axial 3D GeneRalized Autocalibrating Partially Parallel Acquisition (GRAPPA)-based phase cycled Fast Imaging Employing Steady State Acquisition (FIESTA-c) images were acquired in order to quantify the trabecular bone structure. For assessing cartilage morphology (thickness, volume), sagittal high-resolution 3D spoiled gradient echo (SPGR) images were acquired. In a subset of the subjects, sagittal images were acquired for measuring T1rho and T2 relaxation times, using 3D T1rho and T2 mapping techniques.

RESULTS

Good measurement reproducibility was observed for bone parameters, the coefficients of variations (CVs) ranging from 1.8% for trabecular number (app. Tb.N) to 5.5% for trabecular separation (app. Tb.Sp). Significant differences between control and OA groups were found for bone volume fraction bone volume over total volume (app. BV/TV) and app. Tb.Sp in all compartments. Significantly increased values in T1rho and T2 were demonstrated in OA patients compared with controls at the femur, but not at the tibia. T1rho was negatively correlated with app. BV/TV, app. Tb.N and app. Tb.Sp both at the medial femoral condyle (MFC) and lateral tibia (LT), while T2 was only correlated at the LT. Also, medial tibia (MT) T1rho was negatively correlated with app. BV/TV (R(2)=-0.49, P<0.05) and app. Tb.N (R(2)=-0.42, P<0.05) from the opposite side of lateral femoral condyle (LFC). Significant correlations were found between trabecular bone parameters and cartilage thickness and normalized volume, mainly at LT, tibia (T) and femur (F).

CONCLUSION

At this early stage of OA, an overall decrease in bone structure parameters and an increase in cartilage parameters (T1rho, T2) were noticed in patients. Trabecular bone structure correlated with articular cartilage parameters suggesting that loss of mineralized bone is associated with cartilage degeneration.