scholarly journals Quantitative magnetic resonance imaging of meniscal pathology ex vivo

2021 ◽  
Author(s):  
Won C. Bae ◽  
Anthony S. Tadros ◽  
Tim Finkenstaedt ◽  
Jiang Du ◽  
Sheronda Statum ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Spin Echo ◽  
Relaxation Times ◽  
T2 Relaxation ◽  
Quantitative Magnetic Resonance Imaging ◽  
Significant Group ◽  
Ultrashort Echo Time ◽  
Meniscal Pathology ◽  
Conventional Spin Echo ◽  
Fiber Organization

Abstract Objective To determine the ability of conventional spin echo (SE) T2 and ultrashort echo time (UTE) T2* relaxation times to characterize pathology in cadaveric meniscus samples. Materials and methods From 10 human donors, 54 triangular (radially cut) meniscus samples were harvested. Meniscal pathology was classified as normal (n = 17), intrasubstance degenerated (n = 33), or torn (n = 4) using a modified arthroscopic grading system. Using a 3-T MR system, SE T2 and UTE T2* values of the menisci were determined, followed by histopathology. Effect of meniscal pathology on relaxation times and histology scores were determined, along with correlation between relaxation times and histology scores. Results Mean ± standard deviation UTE T2* values for normal, degenerated, and torn menisci were 3.6 ± 1.3 ms, 7.4 ± 2.5 ms, and 9.8 ± 5.7 ms, respectively, being significantly higher in degenerated (p < 0.0001) and torn (p = 0.0002) menisci compared to that in normal. In contrast, the respective mean SE T2 values were 27.7 ± 9.5 ms, 25.9 ± 7.0 ms, and 35.7 ± 10.4 ms, without significant differences between groups (all p > 0.14). In terms of histology, we found significant group-wise differences (each p < 0.05) in fiber organization and inner-tip surface integrity sub-scores, as well as the total score. Finally, we found a significant weak correlation between UTE T2* and histology total score (p = 0.007, Rs2 = 0.19), unlike the correlation between SE T2 and histology (p = 0.09, Rs2 = 0.05). Conclusion UTE T2* values were found to distinguish normal from both degenerated and torn menisci and correlated significantly with histopathology.

scholarly journals Evaluation of malignant effusions using MR-based T1 mapping

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
D. Kuetting ◽  
J. Luetkens ◽  
A. Faron ◽  
A. Isaak ◽  
U. Attenberger ◽  
...  
Keyword(s):  
T1 Mapping ◽  
Ex Vivo ◽  
Diagnostic Yield ◽  
Spin Echo ◽  
Relaxation Times ◽  
Inversion Recovery ◽  
Malignant Effusions ◽  
Mapping Techniques ◽  
Set Up ◽  
Post Hoc

AbstractOur aim was to investigate the diagnostic yield of rapid T1-mapping for the differentiation of malignant and non-malignant effusions in an ex-vivo set up. T1-mapping was performed with a fast modified Look-Locker inversion-recovery (MOLLI) acquisition and a combined turbo spin-echo and inversion-recovery sequence (TMIX) as reference. A total of 13 titrated albumin-solutions as well as 48 samples (29 ascites/pleural effusions from patients with malignancy; 19 from patients without malignancy) were examined. Samples were classified as malignant-positive histology, malignant-negative histology and non-malignant negative histology. In phantom analysis both mapping techniques correlated with albumin-content (MOLLI: r = − 0.97, TMIX: r = − 0.98). MOLLI T1 relaxation times were shorter in malignancy-positive histology fluids (2237 ± 137 ms) than in malignancy-negative histology fluids (2423 ± 357 ms) as well as than in non-malignant-negative histology fluids (2651 ± 139 ms); post hoc test for all intergroup comparisons: < 0.05. ROC analysis for differentiation between malignant and non-malignant effusions (malignant positive histology vs. all other) showed an (AUC) of 0.89 (95% CI 0.77–0.96). T1 mapping allows for non-invasive differentiation of malignant and non-malignant effusions in an ex-vivo set up.

scholarly journals Performance evaluation of a PET insert for preclinical MRI in stand-alone PET and simultaneous PET–MRI modes

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Gaelle Emvalomenos ◽  
Sofie Trajanovska ◽  
Binh T. T. Pham ◽  
Peter Doughty ◽  
Jerome Burnet ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Spin Echo ◽  
Relaxation Times ◽  
Temperature Stability ◽  
Effect Of Temperature ◽  
Fast Spin Echo ◽  
T2 Relaxation ◽  
Absolute Sensitivity ◽  
Field Homogeneity ◽  
T1 And T2

Abstract Background This study aimed to evaluate the performance of a preclinical PET insert in three configurations: as a stand-alone unit outside the MRI bore, inside the bore of a cryogen-free 3T MRI and, finally, while performing simultaneous PET/MRI studies. Methods The PET insert consists of two rings of six detectors, each detector comprising 8 × 12 SiPMs reading out dual offset layers of pixelated LYSO crystals with a 1.4-mm pitch. The inner diameter is 60 mm, transaxial field of view (FoV) 40 mm and axial FoV 98 mm. Evaluation was based on NEMA NU 4-2008 guidelines with appropriate modifications. Spatial resolution and sensitivity were measured inside and outside the MR bore. Image quality, count rate and quantitative performance were measured in all three configurations. The effect of temperature stability on PET sensitivity during fast spin echo sequences was also evaluated. B0 field homogeneity and T1 and T2 relaxation times were measured using a water-filled phantom, with and without simultaneous PET operation. Finally, PET and MRI scans of a mouse injected with 10 MBq [18F]NaF and a mouse injected with 16 MBq [18F]FDG were performed in sequential and simultaneous modes. Results Peak absolute sensitivity was 10.15% with an energy window of 250–750 keV. Absolute sensitivity values outside and inside the MR bore with MR idle agreed to within 0.1%. Outside the MR bore, spatial resolution was 1.21/1.59 mm FWHM (radial/tangential) 5 mm from the centre of the FoV which compared well with 1.19/1.26 mm FWHM inside the MR bore. There were no substantial differences between all three scan configurations in terms of peak NEC rate (175 kcps at 17 MBq), scatter or random fractions. Uniformity and recovery coefficients were also consistent between scanning modes. B0 field homogeneity and T1 and T2 relaxation times were unaltered by the presence of the PET insert. No significant differences were observed between sequential and simultaneous scans of the animals. Conclusions We conclude that the performance of the PET insert and MRI system is not significantly affected by the scanning mode.

Performance Evaluation of a PET Insert for Preclinical MRI in Standalone PET and Simultaneous PET-MRI Modes

2021 ◽  
Author(s):  
Gaelle Emvalomenos ◽  
Sofie Trajanovska ◽  
Binh T.T. Pham ◽  
Peter Doughty ◽  
Jerome Burnet ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Spin Echo ◽  
Relaxation Times ◽  
Temperature Stability ◽  
Effect Of Temperature ◽  
Fast Spin Echo ◽  
T2 Relaxation ◽  
Absolute Sensitivity ◽  
Field Homogeneity ◽  
T1 And T2

Abstract Background: This study aimed to evaluate the performance of a preclinical PET insert in three configurations: as a standalone unit outside the MRI bore, inside the bore of a cryogen-free 3T MRI and, finally, while performing simultaneous PET/MRI studies.Methods: The PET insert consists of 2 rings of 6 detectors, each detector comprising 8x12 SiPMs reading out dual offset layers of pixelated LYSO crystals with a 1.4mm pitch. The inner diameter is 60mm, transaxial Field of View (FoV) 40mm and axial FoV 98mm. Evaluation was based on NEMA NU 4-2008 guidelines with appropriate modifications. Spatial resolution and sensitivity were measured inside and outside the MR bore. Image quality, count rate and quantitative performance were measured in all three configurations. The effect of temperature stability on PET sensitivity during fast spin echo sequences was also evaluated. B0 field homogeneity, T1 and T2 relaxation times were measured using a water-filled phantom, with and without simultaneous PET operation. Finally, PET and MRI scans of a mouse injected with 10 MBq [18F]NaF and a mouse injected with 16 MBq [18F]FDG were performed in sequential and simultaneous modes. Results: Peak absolute sensitivity was 10.15% with an energy window of 250-750 keV. Absolute sensitivity values outside and inside the MR bore with MR idle agreed to within 0.1%. Outside the MR bore spatial resolution was 1.21/1.59 mm FWHM (radial/tangential) 5mm from the centre of the FoV which compared well with 1.19/1.26mm FWHM inside the MR bore. There were no substantial differences between all three scan configurations in terms of peak NEC rate (175 kcps at 17MBq), scatter or random fractions. Uniformity and recovery coefficients were also consistent between scanning modes. B0 field homogeneity and T1 and T2 relaxation times were unaltered by the presence of the PET insert. No significant differences were observed between sequential and simultaneous scans of the animals.Conclusion: We conclude that performance of the PET insert and MRI system are not significantly affected by scanning mode.

055 — (PEI0174) Astrogliosis is associated with increased in vivo and ex vivo MRI T2 relaxation times in the hippocampus of patients with TLE

2014 ◽  
Vol 38 ◽  
pp. 205-206 ◽  
Author(s):  
J.E. Peixoto-Santos ◽  
T.R. Velasco ◽  
J.A. Assirati ◽  
C.G. Carlotti ◽  
R.C. Scandiuzzi ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Relaxation Times ◽  
T2 Relaxation

Quantitative magnetic resonance imaging of upper airways musculature in an animal model of sleep apnea

1996 ◽  
Vol 81 (3) ◽  
pp. 1339-1346 ◽  
Author(s):  
H. M. Schotland ◽  
E. K. Insko ◽  
K. A. Panckeri ◽  
J. S. Leigh ◽  
A. I. Pack ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Animal Model ◽  
Sleep Apnea ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Upper Airway ◽  
Resonance Imaging ◽  
T2 Relaxation ◽  
Quantitative Magnetic Resonance Imaging ◽  
Quantitative Magnetic Resonance

Electromyographic studies of patients with sleep apnea and of the English bulldog, an animal model of sleep apnea, indicate that there is increase activity of the airways dilator muscles. The muscles, when biopsied, show both adaptation and muscle injury. In this study we have utilized quantitative magnetic resonance imaging to characterize changes in the upper airway musculature of the bulldog in vivo. The imaging procedure utilized provided a quantitative measurement of the T2 relaxation times of airway muscle (geniohyoid, sternohyoid, sternothyroid, thyropharyngeus, and hyopharyngeus) and nonairway muscles spatially localized to submillimeter-resolution levels. Quantitative differences between the medians and distributions of T2 relaxation times of airway vs. nonairway muscles were demonstrated. These differences were related to the degree of sleep-disordered breathing. The changes observed are compatible with the hypothesis that there is both increased edema and fibrosis in upper airway muscle in sleep apnea.

Quantification of T1, T2 relaxation times from Magnetic Resonance Fingerprinting radially undersampled data using analytical transformations

2021 ◽  
Vol 80 ◽  
pp. 81-89
Author(s):  
Nikolaos Dikaios ◽  
Nicholas E. Protonotarios ◽  
Athanasios S. Fokas ◽  
George A. Kastis
Keyword(s):  
Magnetic Resonance ◽  
Relaxation Times ◽  
T2 Relaxation ◽  
Undersampled Data
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