Effects of repetitive freeze–thawing cycles on T2 and T2* of the Achilles tendon

Introduction

In this study we sought to evaluate the effects of multiple freezing and thawing cycles on two MR parameters to study Achilles tendon, T2 and T2*.

Materials and methods

Four fresh Achilles tendons were imaged on a 3T clinical scanner and again after 1, 2, 4, and 5 freeze–thaw cycles with spin-echo (SE) and ultrashort echo time (UTE) sequences. Regions of interest were manually drawn over the entire Achilles tendon and mono-exponential curves were used to determine T2 and T2* relaxation times.

Results

There was no statistically significant difference in mean T2 or T2* values between the fresh specimens and after subsequent cycles of freeze–thaw treatment (p > 0.1). Linear regression between SE T2 values at baseline and after successive freeze–thaw cycles demonstrated moderate agreement (r = 0.60) whereas UTE T2* values at baseline and after successive-freeze thaw cycles demonstrated strong agreement (r = 0.92).

Conclusion

These findings suggest that changes between specimens seen in vitro are due to factors other than frozen storage. Furthermore, our results suggest that there is stronger agreement between baseline (fresh) and successive freeze–thaw T2* values of tendon obtained with the UTE technique in comparison to T2 values obtained with a conventional clinical CPMG technique.     

T1ρ and T2 mapping of the proximal tibiofibular joint in relation to aging and cartilage degeneration

Objective

To study the effects of aging and cartilage degeneration of the proximal tibiofibular- and femorotibial joint (PTFJ, FTJ) on the cartilage of the PTFJ using T₁ρ and T₂ mapping.

Materials and methods

We performed sagittal T₁ρ and T₂ mapping of the PTFJ and FTJ on 55 subjects with knee disorders. We placed 3 regions of interest (ROIs) on images of the cartilage in the PTFJ, medial femoral condyle (MFC), and medial tibia plateau (MTP). Correlation analysis was performed for the T₁ρ and T₂ values of each ROI and the patient age and the osteoarthritic grade of the PTFJ and FTJ.

Results

The T₁ρ and T₂ values of the PTFJ were affected neither by aging nor the osteoarthritic grade of the FTJ. Values of the FTJ normalized to PTFJ values were correlated with the osteoarthritic grade of the FTJ in the MFC (r = 0.851 and 0.779, respectively) and the MTP (r = 0.635 and 0.762, respectively). There was a significant difference in the T₁ρ but not the T₂ value of the PTFJ and MFC between normal and mildly osteoarthritic cartilage of each joint.

Conclusion

We document that the T₁ρ and T₂ values of PTFJ cartilage were not affected by aging or cartilage degeneration in the FTJ. The T₁ρ value of the PTFJ may represent a useful internal standard reference for evaluating early degeneration of the FTJ.     

Lactate and T 2 measurements of synovial aspirates at 1.5 T: differentiation of septic from non-septic arthritis

OBJECTIVE: The aim of this study was to differentiate septic from non-septic arthritis by measuring lactate concentration with (1)H magnetic resonance spectroscopy (HMRS) and by estimating total protein content with the assessment of T (2) values. MATERIALS AND METHODS: In 30 patients with acute arthritis, synovial fluid was aspirated. Lactate concentrations were analyzed with single voxel HMRS at 1.5 T. T (2) relaxation times were mapped with a multi-spin echo sequence. All samples underwent microbiological testing and routine laboratory analysis to quantify lactate concentration and total protein content. Values obtained in septic and non-septic arthritis were compared with a Mann-Whitney U test. RESULTS: Synovial fluid from patients with septic arthritis (n = 10) had higher concentrations of lactate (11.4 +/- 4.0 mmol/L) and higher total protein content (51.8 +/- 10.7 g/L) than fluid obtained in non-septic arthritis (n = 20; 5.2 +/- 1.1 mmol/L and 40.4 +/- 6.9 g/L, respectively, p < 0.001 and <0.01, respectively). Measured lactate concentrations and T (2) relaxation times (as an indicator of total protein content) were moderately correlated to laboratory-confirmed lactate concentration (r (2) = 0.71) and total protein content (r (2) = 0.73). Markedly increased lactate concentrations (>6 mmol/L) in combination with low T (2) values (<550 ms) identify septic arthritis with a sensitivity of 70% and a specificity of 89%. CONCLUSION: Spectroscopic measurements of lactate concentration in combination with the estimation of protein content using T (2) may be of value in the differentiation of septic from non-septic arthritis.     

T1ρ and T2 mapping reveal the in vivo extracellular matrix of articular cartilage

Purpose:

To determine the relationship between changes in the extracellular matrix (ECM) and T_1ρ and T₂ values in vivo. The ECM is composed of proteoglycan (PG), collagen, and water. It has been unclear which of the ECM constituents affects T_1ρ and T₂ mapping in living human cartilage.

Materials and Methods:

Sagittal T_1ρ and T₂ maps were preoperatively obtained from 20 knee osteoarthritis patients. Osteochondral samples harvested from the resected tibial plateaus during total knee arthroplasty were consistent with the MRIs of the patients' knees. Parameters that included histological grading of cartilage degeneration, glycosaminoglycan (GAG) content (which constitutes PG), presence of collagen anisotropy and water content were evaluated along with T_1ρ and T₂ values, and statistical analysis was performed using multiple regression analysis.

Results:

T_1ρ and T₂ values were significantly correlated with the degree of cartilage degeneration (β = 0.397 and 0.357, respectively) and the GAG content (β = ?0.340 and ?0.244, respectively).

Conclusion:

The present study demonstrated that T_1ρ and T₂ values reflect the GAG content of the cartilage and can indicate cartilage degeneration in vivo. Use of these parameters can facilitate the noninvasive diagnosis and evaluation of cartilage degeneration. J. Magn. Reson. Imaging 2012;35:147‐155. © 2011 Wiley Periodicals, Inc.

     

Comparison of T2-weighted and contrast-enhanced T1-weighted MR imaging at 1.5?T for assessing the local extent of cervical carcinoma

Objective  

To compare two MR sequences at 1.5 T—T2-weighted and contrast-enhanced T1-weighted images—by using macroscopic sections to determine which image type enables the most accurate assessment of cervical carcinoma.     

Quantitative evaluation of knee cartilage and meniscus destruction in patients with rheumatoid arthritis using T1ρ and T2 mapping

ObjectiveTo calculate T1ρ and T2 values of articular cartilage and menisci in knee joints of patients with RA, and compare the values between RA patients and healthy volunteers, to gain insight into the pathogenesis of cartilage and meniscus degradation in patients with RA.Materials and methodsNine patients with RA and knee joints symptoms were enrolled in the study, twenty healthy volunteers without knee joint diseases were included as controls. Sagittal fat-saturated T1ρ and T2 mapping images were obtained on a 3T MR scanner (GE750, GE Healthcare, Waukesha, WI), using a dedicated 8-channel knee coil. In the T1rho mapping sequence, the amplitude of the spin-lock pulse was 500 Hz, spin lock durations = 10/20/30/50 ms. In the T2 mapping sequence,TR/TE were 1794/6.5, 13.4, 27, 40.7 ms. Both sequences were performed with the following parameters: flip angle (FA) = 90°, matrix: 320 × 256, FOV: 16 × 16 cm², slice thickness: 3 mm, bandwidth: 62.5 kHZ, and a total scan time of 5:11 min. T1ρ- and T2-mapping images were used for the segmentation of the articular cartilage of the patella, femoral trochlea, medial and lateral femoral condyle, medial and lateral tibial plateau. These images were also used for the segmentation of the anterior and posterior horns of the medial and lateral menisci with livewire semi-automatic segmentation algorithm of MATLAB. A Mann–Whitney U test was performed to compare the T1ρ and T2 values of the above mentioned regions between the two groups.ResultsT1ρ (Z = −3.913 to −2.121, P = 0.000–0.034) and T2 (Z = −3.866 to −2.216, P = 0.000–0.026) values of knee cartilage in patients with RA were higher than that in healthy volunteers, except the cartilage of the patella (T1ρ: Z = −1.273, P = 0.203,T2: Z = −0.236, P = 0.814) and lateral tibial plateau (T1ρ:Z = −1.037, P = 0.317). The T1ρ (Z = −1.462 to 0.572, P = 0.095–0.908) and T2 (Z = −1.461 to 0.278, P = 0.153–0.764) values of medial and lateral menisci showed no difference between the two groups.ConclusionPatients with RA exhibit diffuse knee cartilage destruction in the medial and lateral tibiofemoral joints and in the femoral trochlea. However, we found no increase in T1ρ and T2 values in menisci, this finding warrants further investigation.     

T2 and T2∗ mapping in ex situ porcine myocardium: myocardial intravariability,temporal stability and the effects of complete coronary occlusion

International Journal of Legal Medicine - Diagnosis of ischaemia-related sudden cardiac death in the absence of microscopic and macroscopic ischaemic lesions remains a challenge for medical...     

Comparative study of image quality between axial T2-weighted BLADE and turbo spin-echo MRI of the upper abdomen on 3.0 T

Objective

To compare image quality of turbo spin-echo (TSE) with BLADE [which is also named periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER)] on magnetic resonance imaging (MRI) for upper abdomen.

Materials and methods

This study involved the retrospective evaluation of 103 patients (63 males, 40 females; age range 19–76 years; median age 53.8 years) who underwent 3.0 T MRI with both conventional TSE T2-weighted imaging (T2WI) and BLADE TSE T2WI. Two radiologists assessed respiratory motion, gastrointestinal peristalsis, and vascular pulsation artifacts, as well as the sharpness of the liver and pancreas edges. Scores for all magnetic resonance (MR) images were recorded. Wilcoxon’s rank test was used to compare hierarchical data. Cohen’s kappa coefficient was adopted to analyze interobserver consistency.

Results

Compared to TSE T2WI, BLADE TSE T2WI reduced all of the examined motion artifacts and increased the sharpness of the liver and pancreas edges (all P < 0.05). Medium to good interobserver consistency was obtained for evaluating these indicators. The scanning time of BLADE TSE T2WI was 4–16 s shorter than that of conventional TSE T2WI.

Conclusion

Compared to TSE sequence, the BLADE technique can reduce the respiratory motion, gastrointestinal peristalsis, and vascular pulsation artifacts, while decreasing the scanning time and improving the anatomic detail and image quality.

     

Comparison of flow artifacts between 2D-FLAIR and 3D-FLAIR sequences at 3 T

It has been reported that 3D-FLAIR can reduce the flow artifact resulting from cerebrospinal fluid (CSF) at 1.5 T compared to 2D-FLAIR. Flow-related artifacts tend to be worse at 3 T than at 1.5 T. The purpose of this study was to compare the CSF flow artifacts of 2D-FLAIR and 3D-FLAIR sequences at 3 T in eight healthy volunteers. The grade of CSF-related artifacts were scored through observing the perimedullary cistern, cerebellopontine angle cisterns, fourth ventricule, prepontine cistern, suprasellar cistern, ambient cisterns, sylvian fissures, third ventricle and lateral ventricles. Grading was performed on either axial or sagittal images. The CSF in-flow artifact scores were significantly higher on axial 2D-FLAIR than on axial 3D-FLAIR MPR images in all areas except the bilateral sylvian fissures, and higher on sagittal 2D-FLAIR than on sagittal 3D-FLAIR MPR images in perimedullary, bilateral CP angle and suprasellar cisterns. The CSF-related flow artifacts were significantly reduced by 3D-FLAIR, while structures in the cistern were depicted more clearly, even at 3 T. Further study is necessary to compare the clinical efficacy between 2D-FLAIR and 3D-FLAIR in depicting subtle abnormalities.     

Comparison of left ventricular function assessment using phonocardiogram- and electrocardiogram-triggered 2D SSFP CINE MR imaging at 1.5 T and 3.0 T

Objective

As high-field cardiac MRI (CMR) becomes more widespread the propensity of ECG to interference from electromagnetic fields (EMF) and to magneto-hydrodynamic (MHD) effects increases and with it the motivation for a CMR triggering alternative. This study explores the suitability of acoustic cardiac triggering (ACT) for left ventricular (LV) function assessment in healthy subjects (n?=?14).

Methods

Quantitative analysis of 2D CINE steady-state free precession (SSFP) images was conducted to compare ACT’s performance with vector ECG (VCG). Endocardial border sharpness (EBS) was examined paralleled by quantitative LV function assessment.

Results

Unlike VCG, ACT provided signal traces free of interference from EMF or MHD effects. In the case of correct R-wave recognition, VCG-triggered 2D CINE SSFP was immune to cardiac motion effects—even at 3.0 T. However, VCG-triggered 2D SSFP CINE imaging was prone to cardiac motion and EBS degradation if R-wave misregistration occurred. ACT-triggered acquisitions yielded LV parameters (end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF) and left ventricular mass (LVM)) comparable with those derived from VCG-triggered acquisitions (1.5 T: ESV_VCG?=?(56?±?17) ml, EDV_VCG?=?(151?±?32) ml, LVM_VCG?=?(97?±?27) g, SV_VCG?=?(94?±?19) ml, EF_VCG?=?(63?±?5)% cf. ESV_ACT?=?(56?±?18) ml, EDV_ACT?=?(147?±?36) ml, LVM_ACT?=?(102?±?29) g, SV_ACT?=?(91?±?22) ml, EF_ACT?=?(62?±?6)%; 3.0 T: ESV_VCG?=?(55?±?21) ml, EDV_VCG?=?(151?±?32) ml, LVM_VCG?=?(101?±?27) g, SV_VCG?=?(96?±?15) ml, EF_VCG?=?(65?±?7)% cf. ESV_ACT?=?(54?±?20) ml, EDV_ACT?=?(146?±?35) ml, LVM_ACT?=?(101?±?30) g, SV_ACT?=?(92?±?17) ml, EF_ACT?=?(64?±?6)%).

Conclusions

ACT’s intrinsic insensitivity to interference from electromagnetic fields renders it suitable for clinical CMR.     

Sensitivity of T2-weighted FSE sequences towards physiological iron depositions in normal brains at 1.5 and 3.0 T

To evaluate the sensitivity of T2-weighted fast spin-echo (FSE) sequences to physiological iron depositions in normal brains at MR imaging field strengths of 1.5 and 3.0 T. T2-weighted FSE sequences acquired at 1.5 and 3.0 T clinical imaging systems (Gyroscan Intera, Philips Medical Systems, Best, The Netherlands) were compared by means of MRI in phantoms (n=6) and healthy volunteers (n=10). Contrast-to-noise ratios (CNRs) of tubes doped with iron oxides at different concentrations and of brain areas with physiological iron depositions (nucleus ruber, substantia nigra, globus pallidus) were calculated for either field strength. Apparent susceptibility effects of iron-containing brain structures were qualitatively analyzed by comparing the degree of visible hypointensity by a score system at either field strength. The mean CNR of iron oxide tubes and iron-containing brain areas was significantly decreased at 3.0 T. Qualitative analysis confirmed these measurements. Detection and diagnosis of brain disorders with altered iron content such as neurodegenerative parkinsonian disorders (NPD) or intracerebral hemorrhage should benefit from the increased sensitivity of T2-weighted FSE sequences to susceptibility effects at 3.0 T.     

Radiation treatment of exhaust gases—VI. Effects of CO and H2 on the removal of NO and NO2 in the moist mixture of O2 and N2

The effects of CO and H₂ on the removal of NO and NO₂ were studied in the mixture of H₂O, O₂ and N₂ irradiated by electron beams of 1.5 MeV energy at 120°C. In the NOH₂OO₂N₂ mixture, the NO removal and the corresponding NO₂ formation were enhanced markedly by the addition of CO or H₂, but not by CO₂. In the NO₂H₂OO₂N₂ mixture, the NO₂ removal was markedly suppressed by the addition of CO up to 0.88% and was not observed in the presence of CO above 1.5%. These effects of CO on the removal of NO and NO₂ may be brought about by the scavenging of OH radical by CO to produce H atom, leading to the formation of HO₂ radical which oxidizes NO to NO₂.     

T(1ρ) and T(2) quantitative magnetic resonance imaging analysis of cartilage regeneration following microfracture and mosaicplasty cartilage resurfacing procedures

Purpose

To examine T_1ρ (T1rho) and T₂ quantitative magnetic resonance imaging (MRI) in evaluating cartilage regeneration following microfracture (MFx) and mosaicplasty (MOS) cartilage resurfacing procedures.

Materials and Methods

Eighteen patients underwent MFx and eight patients underwent MOS to treat symptomatic focal cartilage defects. Quantitative T_1ρ and T₂ maps were acquired at 3–6 months and 1 year after surgery. The area of resurfacing was identified, and T_1ρ and T₂ values for the regenerated tissue (RT) and normal cartilage (NC) were acquired. RT/NC ratios were calculated to standardize absolute T_1ρ and T₂ values. Data were prospective, cross‐sectional, and nonrandomized.

Results

T_1ρ and T₂ showed good reanalysis reproducibility for RT and NC. Significant differences between RT and NC were present following MFx at 3–6 months for T_1ρ and T₂ values as well as following MOS at 3–6 months and 1 year for T_1ρ values. Following MFx, the T₂ RT/NC ratio was significantly different between 3–6 months and 1 year (P = 0.02), while the T_1ρ RT/NC ratio approached significance (P = 0.07). Following MOS, the T_1ρ and T₂ RT/NC ratios were not significantly different between the two timepoints.

Conclusion

T_1ρ and T₂ MRI are complementary and reproducible methods for quantitatively and noninvasively monitoring regeneration of RT following MFx and MOS. J. Magn. Reson. Imaging 2010;32:914–923. © 2010 Wiley‐Liss, Inc.     

Visualization of cranial nerves I–XII: value of 3D CISS and T2-weighted FSE sequences

The aim of this study was to evaluate the sensitivity of the three-dimensional constructive interference of steady state (3D CISS) sequence (slice thickness 0.7 mm) and that of the T2-weighted fast spin echo (T2-weighted FSE) sequence (slice thickness 3 mm) for the visualization of all cranial nerves in their cisternal course. Twenty healthy volunteers were examined using the T2-weighted FSE and the 3D CISS sequences. Three observers evaluated independently the cranial nerves NI–NXII in their cisternal course. The rates for successful visualization of each nerve for 3D CISS (and for T2-weighted FSE in parentheses) were as follows: NI, NII, NV, NVII, NVIII 40 of 40 (40 of 40), NIII 40 of 40 (18 of 40), NIV 19 of 40 (3 of 40), NVI 39 of 40 (5 of 40), NIX, X, XI 40 of 40 (29 of 40), and NXII 40 of 40 (4 of 40). Most of the cranial nerves can be reliably assessed when using the 3D CISS and the T2-weighted FSE sequences. Increasing the spatial resolution when using the 3D CISS sequence increases the reliability of the identification of the cranial nerves NIII–NXII. Received: 29 September 1999; Revised: 2 February 2000; Accepted: 21 March 2000     

Grading of small hepatocellular carcinomas (≤2 cm): correlation between histology,T2 and diffusion-weighted imaging

Objective:

To evaluate the capacity of diffusion-weighted imaging (DWI) to determine the histological grade of small-sized hepatocellular carcinomas (HCCs) in liver cirrhosis in comparison with T₂ weighted imaging.

Methods:

51 cirrhotic patients with 63 histologically proven HCCs ≤2 cm underwent abdominal MRI, including DWI (b-values 50, 400 and 800 s mm⁻²) and T₂ weighted sequences. HCCs were classified into well-differentiated HCCs (n = 37) and moderately differentiated HCCs (n = 26). Relative contrast ratios (RCRs) between the lesions and the surrounding liver were performed and compared between the two groups for T₂ weighted images, each b-value and apparent diffusion coefficients (ADCs). A receiver operating characteristic (ROC) analysis was performed to compare RCRs in T₂ and diffusion-weighted images.

Results:

We found significant differences in RCRs between well-differentiated vs moderately differentiated HCCs for b = 50, 400 and 800 s mm⁻² and T₂ weighted images (1.35 ± 0.36 vs 1.86 ± 0.62; 1.35 ± 0.38 vs 1.82 ± 0.60; 1.27 ± 0.30 vs 1.74 ± 0.53; 1.14 ± 0.18 vs 1.43 ± 0.28, respectively; p < 0.001), whereas no significant differences were observed in ADC and ADC RCR (1.05 ± 0.19 vs 0.99 ± 0.15 and 1.1 ± 0.22 vs 1.09 ± 0.23; p = 0.16 and p = 0.82, respectively). No significant difference was found in the areas under the ROC curve for RCRs of T₂ weighted images and every DWI b-value (p = 0.18).

Conclusion:

The RCR measurement performed in DWI 50, 400 and 800 b-values and T₂ demonstrated a significant difference between well-differentiated and moderately differentiated small-sized HCCs. Furthermore, no difference was shown by using either ADC or ADC RCR.

Advances in knowledge:

DWI with RCR measurement may be a valuable tool for non-invasively predicting the histological grade of small HCCs.Recent advances in liver imaging techniques and a better understanding of imaging findings have facilitated the detection of small nodules in cirrhotic livers. Nodular lesions ≤2 cm against a background of cirrhosis are diagnostically challenging in daily practice.¹ The early and accurate diagnosis of hepatocellular carcinomas (HCCs) is of great importance because the best treatment results are obtained in patients with small and non-invasive HCCs.^2,3 If small HCCs are not treated, they can grow aggressively and microscopic vascular invasion can occur before the 2-cm cut-off size for small HCCs.¹ Fukuda et al⁴ reported that moderately and poorly differentiated HCCs ≤2 cm have a greater tendency towards microvascular invasion, meaning that the malignant potential of small HCCs should also be taken into account when selecting a treatment. Therefore, the accurate distinction of well-differentiated HCCs from less well-differentiated HCCs is also considered an important issue in planning of the therapeutic strategy, even if the tumour is small.^5,6 Considering that histological confirmation of small suspicious hepatic nodules before treatment is often not possible owing to their location in the liver or the risks of track seeding, the role of a non-invasive pre-operative imaging technique for the discrimination of moderate to poorly differentiated HCCs from well-differentiated HCCs is important. Diffusion-weighted imaging (DWI) allows the characterization of microscopic proton displacement and has profoundly improved oncological imaging. Owing to the recent advances in MRI technology, DWI can be applied to liver imaging with improved image quality.⁷ Several clinical trials have demonstrated the benefit of DWI in the detection and characterization of focal liver lesions.^8–11 There have been attempts to correlate DWI findings with the histological grading of HCCs using signal intensity (SI) and apparent diffusion coefficient (ADC) values, but no consensus in the results was obtained.^12–18 To the best of our knowledge, the interplay between DWI and histopathological factors in a cohort of patients with exclusively small HCCs (<2 cm) has not been specifically investigated. The purpose of the present study was to investigate whether or not diffusion-weighted (DW) images and ADC could determine the histological grading of HCCs <2 cm in diameter.     

Measurement of liver T₁ and T₂ relaxation times in an experimental mouse model of liver fibrosis

Purpose:

To characterize changes in relaxation times of liver using quantitative magnetic resonance imaging (MRI) in an experimental mouse model of liver fibrosis. Quantitative MRI is a potentially robust method to characterize liver fibrosis. However, correlation between relaxation times and fibrosis stage has been controversial.

Materials and Methods:

Liver fibrosis was induced in male adult C57BL/6N mice (22–25 g; n = 12) by repetitive dosing of carbon tetrachloride (CCl₄). The animals were examined with a series of spin‐echo (SE) images with varying TRs and multiecho SE imaging sequence at 7 T before and 2, 4, 6, and 8 weeks after CCl₄ insult. Hepatic T₁ and T₂ values were measured. Histology was performed with hematoxylin‐eosin staining and Masson's trichrome staining.

Results:

Significant increase (P < 0.001) in hepatic T₁ was found at 2, 4, 6, and 8 weeks following CCl₄ insult as compared with that before insult. Meanwhile, hepatic T₂ at 2, 4, 6, and 8 weeks after CCl₄ insult was significantly higher (P < 0.001) than that before the insult. Liver histology showed collagen deposition, edema, and infiltration of inflammatory cells in livers with CCl₄ insult.

Conclusion:

Both longitudinal and transverse relaxation times may serve as robust markers for liver fibrosis. With the advent of single breath‐hold sequences for MR relaxometry, quantitative mapping of relaxation times can be routinely and reliably performed in abdominal organs and hence may be valuable and robust in detecting liver fibrosis at early phase and monitoring its progression. J. Magn. Reson. Imaging 2012;36:152–158. © 2012 Wiley Periodicals, Inc.