MR Relaxometry Research Articles

3.0T relaxation time measurements of human lymph nodes in adults with and without lymphatic insufficiency: Implications for magnetic resonance lymphatic imaging.

The purpose of this work was to quantify 3.0T (i) T1 and T2 relaxation times of in vivo human lymph nodes (LNs) and (ii) LN relaxometry differences between healthy LNs and LNs from patients with lymphatic insufficiency secondary to breast cancer treatment-related lymphedema (BCRL). MR relaxometry was performed over bilateral axillary regions at 3.0T in healthy female controls (105 LNs from 20 participants) and patients with BCRL (108 LNs from 20 participants). Quantitative T1 maps were calculated using a multi-flip-angle (20, 40, 60°) method with B1 correction (dual-TR method, TR1 /TR2 =30/130ms), and T2 maps using a multi-echo (TE =9-189ms; 12ms intervals) method. T1 and T2 were quantified in the LN cortex and hilum. A Mann-Whitney U-test was applied to compare LN relaxometry values between patients and controls (significance, two sided, p<0.05). Linear regression was applied to evaluate how LN relaxometry varied with age, BMI, and clinical indicators of disease. LN substructure relaxation times (mean±standard deviation) in healthy controls were T1 cortex, 1435±391ms; T1 hilum, 714±123ms; T2 cortex, 102±12ms, and T2 hilum, 119±21ms. T1 of the LN cortex was significantly reduced in the contralateral axilla of BCRL patients compared with the axilla on the surgical side (p<0.001) and compared with bilateral control values (p<0.01). The LN cortex T1 asymmetry discriminated cases from controls (p=0.004) in a multiple linear regression, accounting for age and BMI. Human 3.0TT1 and T2 relaxation times in axillary LNs were quantified for the first time in vivo. Measured values are relevant for optimizing acquisition parameters in anatomical lymphatic imaging sequences, and can serve as a reference for novel functional and molecular LN imaging methods that require quantitative knowledge of LN relaxation times.

OA017] Fabrication of an anthropomorphic neonatal 3D printed head phantom, to be utilized as a quality assurance means for the optimization of the neonatal brain T1 and T2 weighted sequences on a 1.5T clinical MRI system

Purpose To develop an anthropomorphic neonatal 3D printed head phantom which could be used as a quality assurance means for the overall optimization of the neonatal brain clinical T1-weighted (T1w) and T2-weighted (T2w) MRI pulse sequences. Materials and Methods Tissue-mimicking materials simulating the MR relaxation times of gray and white matter of the neonatal brain were fabricated and enclosed in five glass tube vials. A 3D printed neonatal head anthropomorphic phantom, with radiologically bone-equivalent material was fabricated using anonymized CT scans of a specific neonatal subject. The aforementioned tube vials were encapsidated inside the neonatal head phantom cavity. The anthropomorphic phantom with the encapsidated neonatal brain tissue mimicking glass vials underwent quantitative MR relaxometry utilizing an Inversion Recovery Turbo Spin Echo (IRTSE) sequence to estimate T1 relaxation times and a Car-Purcell-Meiboom-Gill (CPMG) sequence to estimate T2 relaxation times on a clinical 1.5T MRI system. Based on the relaxometric T1 and T2 measurements, the optimal TR and TE values at which the maximum Contrast to Noise Ratio (CNR) between neonatal gray and white matter was recorded were used for the final optimization of the clinical T1w and T2w clinical sequences respectively. Results T1 and T2 relaxation times of the tissue mimicking materials were in concordance with the relaxation times of a real neonatal brain subject. Clinical MRI system’s reproducibility for T1 and T2 measurements remained The anthropomorphic neonatal 3D printed head phantom served as an excellent means for the general optimization of the geometrical, MR signaling and RF safety characteristics, as well as the optimal acquisition times of the clinical neonatal T1w and T2w MRI pulse sequences. Optimal values for the TR and TE MRI parameters were assessed in reference to the maximum CNR between neonatal brain gray and white matter. These were: (TR/TE = 1200 ms/10 ms) for the T1wSE and (TR/TE = 9500 ms/280 ms) for the (T2wTSE) sequences respectively. Conclusion Overall clinical T1w and T2w sequence optimization for neonatal brain imaging at a 1.5T clinical MRI system was accomplished with the aid of an anthropomorphic neonatal 3D printed head phantom encapsidated with neonatal brain tissue mimicking materials.

P045] Neonatal brain: Contrast to noise ratio (CNR) optimization of T1-weighted (T1W) and T2-weighted (T2W) sequences at multiple 1.5T MRI systems, utilizing a neonatal brain tissue mimicking phantom

Purpose To optimize clinical T1w and T2w sequences at multiple 1.5T MRI systems of different vendors, using an in house developed phantom simulating neonatal brain relaxometric characteristics. Materials Methods A neonatal brain phantom, fabricated from paramagnetically doped agarose gel solutions, underwent quantitative MR relaxometry utilizing an Inversion Recovery Spin Echo (IRTSE) method to estimate T1 relaxation times and a Car-Purcell-Meiboom-Gill (CPMG) method to estimate T2 relaxation times at multiple 1.5T MRI systems. Multi-TI turbo spin-echo and multi-TE spin-echo sequences were utilized for direct T1 and T2 relaxation time measurements. Results Signal data S(TR, TE) were reproduced mathematically according to the standard SE signal acquisition equation: S(TR, TE) = PD*(1-exp(-TR/T1)*(exp(-TE/T2). Consequently, TR and TE values at which the maximum CNR between neonatal gray and white matter was recorded were used for the final optimization of T1w and T2w clinical sequences respectively. Based on the above values, TR and TE parameters were modified resulting in an optimized T1wSE sequence TR/TE = 1200 ms/10 ms and an optimized T2wTSE sequence TR/TE = 9500 ms/280 ms as estimated on a clinical MAGNETOM Sonata 1.5T system. Clinical MRI inter-equipment variability for T1 and T2 measurements remained TR and TE parameter variation in optimized T1w and T2w sequences remained less than 7% amongst the selected MRI systems included in this study. Conclusions CNR optimization of T1w and T2w sequences for neonatal brain imaging at multiple 1.5T clinical MRI systems was accomplished with the aid of an in house developed tissue-mimicking phantom.

Demonstration of differences in colonic volumes, transit, chyme consistency, and response to psyllium between healthy and constipated subjects using magnetic resonance imaging.

In functional gastrointestinal disorders a lack of objective biomarkers limits evaluation of underlying mechanisms. We aimed to demonstrate the utility of magnetic resonance imaging for this task using psyllium, an effective constipation treatment, in patients and controls. Two crossover studies: (i) adults without constipation (controls, n=9) took three treatments in randomized order for 6days - maltodextrin (placebo), psyllium 3.5g t.d.s and 7g t.d.s., (ii) adults with chronic constipation (patients, n=20) took placebo and psyllium 7g t.d.s. for 6days. MRI was performed fasting and postprandially on day 6. Measurements included small bowel and ascending colon water content, colonic volume, transit time, and MR relaxometry (T1, T2) to assess colonic chyme. Stool water percentage was measured. 7g psyllium t.d.s. increased fasting colonic volumes in controls from median 372mL (IQR 284-601) to 578mL (IQR 510-882), and in patients from median 831mL (IQR 745-934) to 1104mL (847-1316), P<.05. Mean postprandial small bowel water was higher in controls and patients after 7g psyllium t.d.s. vs placebo. Whole gut transit was slower in patients than controls (P<.05). T1 of the descending colon chyme (fasting) was lower in patients (213ms, 176-420) than controls (440ms, 352-884, P<.05) on placebo, but increased by 7g psyllium t.d.s. (590ms, 446-1338), P<.001. Descending colon T1 correlated with baseline stool water content and stool frequency on treatment. MRI measurements can objectively demonstrate the mode of action of therapy targeting intestinal fluid content in constipation.

PO-410 Cytotoxicity and genotoxicity of new gadolinium, iron oxide, cobalt ferrite and graphene oxide nanoparticles on some tumour cell lines in vitro

ABSTRACT Introduction Nanoparticles (NPs) are increasingly used in cancer therapy as delivery agents and in the diagnosis of malignant diseases as contrast agents for magnetic resonance imaging (MRI). The aim of this work was in vitro assessments of Gd-NPs, Fe-NPs, CoFe-NPs and Graphene Oxide-NPs cytotoxicity and genotoxicity on some tumour and normal human cell lines. Material and methods The investigated new nanomaterials were prepared and characterised by standard methods XRD, FTIR, SEM, TEM, AFM and MR relaxometry measurements. Cytotoxic activity of investigated compounds was performed by 72 hour MTT test. Target cells used were MDA-MB-453, HeLa and K562 malignant cells and MRC-5 was used as normal control cells. Genotoxicity of Gd-NP was evaluated by the Comet assay on the model of normal MRC-5 cells. DNA strand break levels were determined and expressed as% tail DNA. Results and discussions All investigated nanoparticle materials exerted a dose dependent cytotoxicity towards investigated cell lines with moderate to low selectivity in their action to tumour cells in comparison to normal control cells. Concentrations inducing 50% decrease in cell survival (IC50) showed that Gd-NPs possess moderate cytotoxicity and selectivity with IC50 value of 297 µg/mL on K562 cells and IC50=740 µg/mL for control MRC-5 cells. Likewise, Fe-NPs did not show toxicity on normal MRC-5 cells (IC50 >1000 µg/mL), but possess moderate toxicity to all tumour cells (IC50=336 µg/mL, 406 µg/mL and 682 µg/mL for K562, MDA-MB-453 and HeLa cells respectively). Graphene oxide-NPs showed very strong toxicity to all investigated cell lines and low selectivity with IC50 values in the range of 2.13 µg/mL (K562 cells) to 3.30 µg/mL (control MRC-5 cells). CoFe-NPs also showed strong toxicity, but to a lesser extent compared to graphene oxide (the IC50 values for all tested cell lines were in the range 19–40 µg/mL).Evaluation of genotoxicity by the Comet assay after treatment of MRC-5 cells with Gd-NPs showed no effect on DNA strand break levels at doses up to 750 µg/ml. The DNA is damaged only at very high concentrations applied (≥1125 µg/mL). Conclusion Results obtained showed that Graphene Oxide-NPs and CoFe-NPs have very strong nonselective toxicity, but gadolinium and Fe nanomaterials due to a moderate selectivity in toxicity to tumour cells could be promising agents for further research and the use in the diagnostics and treatment of cancers.

Inter-method reproducibility of biexponential R2 MR relaxometry for estimation of liver iron concentration.

To assess the reproducibility of biexponential R2 -relaxometry MRI for estimation of liver iron concentration (LIC) between proprietary and nonproprietary analysis methods. This single-center retrospective study, approved by investigational review board and compliant with the Health Insurance Portability and Accountability Act, included 40 liver MRI exams in 38 subjects with suspected or known iron overload. From spin-echo images of the liver, acquired at 5 different echo times (TE = 6-18 ms), biexponential R2 maps were calculated using 1 proprietary (FerriScan, Resonance Health Ltd., Claremont WA, Australia) and 3 nonproprietary (simulated annealing, nonlinear least squares, dictionary search) analysis methods. Each subject's average liver R2 value was converted to LIC using a previously validated calibration curve. Inter-method reproducibility for liver R2 and LIC were assessed for linearity using linear regression analysis and absolute agreement using intraclass correlation and Bland-Altman analysis. For point estimates, 95% confidence intervals were calculated; P values < 0.05 were considered statistically significant. Linearity between the proprietary and nonproprietary methods was excellent across the observed range for R2 (20-312 s-1 ) and LIC (0.4-52.2 mg/g), with all coefficients of determination (R2 ) ≥ 0.95. No statistically significant bias was found (slope estimates ∼ 1; intercept estimates ∼ 0; P values > 0.05). Agreement between the 4 methods was excellent for both liver R2 and LIC (intraclass correlations ≥ 0.97). Bland-Altman 95% limits of agreement in % difference between the proprietary and nonproprietary methods were ≤ 9% and ≤ 16% for R2 and LIC, respectively. Biexponential R2 -relaxometry MRI for LIC estimation is reproducible between proprietary and nonproprietary analysis methods.

PROBING IN VIVO MICROSTRUCTURE WITH T 1-T 2 RELAXATION CORRELATION SPECTROSCOPIC IMAGING.

Quantitative MR relaxometry can provide unique subvoxel information about the microscopic tissue compartments that are present in a large imaging voxel. However, unambiguously distinguishing between these tissue compartments continues to be challenging with conventional methods due to the illposedness of the inverse problem. This paper describes a new imaging approach, which we call T 1 Relaxation-T 2 Relaxation Correlation Spectroscopic Imaging (RR-CSI), that uses two-dimensional relaxation encoding combined with spatially-constrained reconstruction to help overcome illposedness. Results are shown with real data, including what we believe to be the first in vivo demonstration of multidimensional relaxation correlation spectroscopic imaging.

A diffusion model-free framework with echo time dependence for free-water elimination and brain tissue microstructure characterization.

PurposeThe compartmental nature of brain tissue microstructure is typically studied by diffusion MRI, MR relaxometry or their correlation. Diffusion MRI relies on signal representations or biophysical models, while MR relaxometry and correlation studies are based on regularized inverse Laplace transforms (ILTs). Here we introduce a general framework for characterizing microstructure that does not depend on diffusion modeling and replaces ill‐posed ILTs with blind source separation (BSS). This framework yields proton density, relaxation times, volume fractions, and signal disentanglement, allowing for separation of the free‐water component.Theory and MethodsDiffusion experiments repeated for several different echo times, contain entangled diffusion and relaxation compartmental information. These can be disentangled by BSS using a physically constrained nonnegative matrix factorization.ResultsComputer simulations, phantom studies, together with repeatability and reproducibility experiments demonstrated that BSS is capable of estimating proton density, compartmental volume fractions and transversal relaxations. In vivo results proved its potential to correct for free‐water contamination and to estimate tissue parameters.ConclusionFormulation of the diffusion‐relaxation dependence as a BSS problem introduces a new framework for studying microstructure compartmentalization, and a novel tool for free‐water elimination.

Quantitative MR Evaluation of Chronic Pancreatitis: Extracellular Volume Fraction and MR Relaxometry.

The purpose of this study was to determine if extracellular volume fraction and T1 mapping can be used to diagnose chronic pancreatitis (CP). This HIPAA-compliant study analyzed 143 consecutive patients with and without CP who underwent MR imaging between May 2016 and February 2017. Patients were selected for the study according to inclusion and exclusion criteria that considered history and clinical and laboratory findings. Eligible patients (n = 119) were grouped as normal (n = 60) or with mild (n = 22), moderate (n = 27), or severe (n = 10) CP on the basis of MRCP findings using the Cambridge classification as the reference standard. T1 maps were acquired in unenhanced and late contrast-enhanced phases using a 3D dual flip-angle gradient-echo sequence. All patients were imaged on the same 3-T scanner using the same imaging parameters, contrast agent, and dosage. Mean extracellular volume fractions and T1 relaxation times were significantly different within the study groups (one-way ANOVA, p < 0.001). Using the AUC curve analysis, extracellular volume fraction of > 0.27 showed 92% sensitivity (54/59) and 77% specificity (46/60) for the diagnosis of CP (AUC = 0.90). A T1 relaxation time of > 950 ms revealed 64% sensitivity (38/59) and 88% specificity (53/60) (AUC = 0.80). Combining extracellular volume fraction and T1 mapping yielded sensitivity of 85% (50/59) and specificity of 92% (55/60) (AUC = 0.94). Extracellular volume fraction and T1 mapping may provide quantitative metrics for determining the presence and severity of acinar cell loss and aid in the diagnosis of CP.

Quantification of MRI visibility and artifacts at 3T of liquid fiducial marker in a pancreas tissue-mimicking phantom.

X-ray-based position verification of the target volume in image-guided radiation therapy (IGRT) of patients with pancreatic ductal adenocarcinoma (PDAC) is currently performed on solid fiducial markers that are implanted under endoscopic ultrasonography. A new biodegradable liquid fiducial marker has recently been introduced. To assess its potential use for magnetic resonance imaging (MRI)-guided photon or proton radiotherapy of PDAC, the MRI visibility and artifacts of this marker were quantified and compared against solid gold markers. Different spherical volumes (10 μL, 25 μL, 50 μL, and 100 μL) of a biodegradable liquid fiducial marker as well as seven differently sized and oriented solid gold (0.35 mm diameter; 5 mm and 10 mm length) and iron-gold alloy fiducial markers (0.28 mm diameter; 1 cm and 2 cm length) were implanted in a spherical gel phantom, mimicking the proton spin relaxation properties of healthy pancreatic tissue at 3 Tesla. MR relaxometry was performed to quantify the size and magnitude of the decrease in the effective transversal relaxation time T2∗ and relative proton density ρ(H) as a measure of potential visibility and to quantify the size and magnitude of the increase in magnetic field inhomogeneity ΔB0 as a measure of potential signal artifacts. The phantom was scanned in a 3.0 T PET/MR scanner with an eight-channel head coil. The solid fiducial markers showed a direct linear relationship between the potentially visible size and artifact size. The liquid fiducial marker showed a tendency toward a potentially visible size at smaller artifacts. Liquid markers from 25 to 100 μL generated visible volumes comparable to the size of the solid markers. The magnitude of visibility was the highest for the liquid fiducial marker with volumes of 25-100 μL showing no correlation with the magnitude of artifact. The solid markers showed a strong nonlinear correlation between magnitude of visibility and artifact, whereas the solid marker consisting of a gold-iron alloy induced the strongest artifacts. The liquid fiducial marker causes signal voids on MRI due to its absence of water hydrogen atoms without strongly affecting the magnetic field in the surrounding tissue. The alteration of the static magnetic field was found to be the main effect leading to the visibility of the solid fiducial markers. Hence, especially when a low level of image distortion is required, MRI characteristics of the liquid marker surpass those of solid gold markers currently being used for IGRT of PDAC.

Specific visualization of neuromelanin-iron complex and ferric iron in the human post-mortem substantia nigra using MR relaxometry at 7T

Neuromelanin (NM) is an endogenous iron chelating molecule of pigmented neurons in the human substantia nigra (SN). Along with the increase in iron deposition, the reduction in NM-containing dopaminergic neurons and the variation of iron load on NM are generally considered to be important factors participating to pathogenesis of Parkinson's disease (PD). The aim of this study was to non-invasively delineate the spatial distributions of paramagnetic magnetic susceptibility perturbers, such as NM-iron complex and ferric iron in SN. Multiple quantitative MR parameters of T1, T2, T2*, susceptibility weighted image (SWI), quantitative susceptibility map (QSM), and T1 weighted image with magnetization transfer (MT) effects were acquired for six post-mortem SN samples without a history of neurological disease. Co-registered quantitative histological validations were performed to identify and correlate NM pigments, iron deposits, and myelin distributions with respect to associated MR parameters. The regions with NM pigments and iron deposits showed positive magnetic susceptibility (paramagnetic) values, while myelinated areas showed negative magnetic susceptibility (diamagnetic) values from the QSM. The region of reduced T2 values in SN mostly coincided with high iron deposits, but not necessarily with the NM pigments. The correlations between T2*/T2 (or T2*/T22) values and NM pigments were higher than those between T2* values and NM pigments, due to the effective size differences between NM-iron complex and ferric iron. Consequently, separate segmentations of ferric iron from the T2 map and NM-iron complex from the T2*/T2 map (or T2*/T22 map) were possible with the boundary of the SN determined from the T1 weighted image.

Direct diffusion tensor estimation using a model-based method with spatial and parametric constraints.

To develop a new model-based method with spatial and parametric constraints (MB-SPC) aimed at accelerating diffusion tensor imaging (DTI) by directly estimating the diffusion tensor from highly undersampled k-space data. The MB-SPC method effectively incorporates the prior information on the joint sparsity of different diffusion-weighted images using an L1-L2 norm and the smoothness of the diffusion tensor using a total variation seminorm. The undersampled k-space datasets were obtained from fully sampled DTI datasets of a simulated phantom and an ex-vivo experimental rat heart with acceleration factors ranging from 2 to 4. The diffusion tensor was directly reconstructed by solving a minimization problem with a nonlinear conjugate gradient descent algorithm. The reconstruction performance was quantitatively assessed using the normalized root mean square error (nRMSE) of the DTI indices. The MB-SPC method achieves acceptable DTI measures at an acceleration factor up to 4. Experimental results demonstrate that the proposed method can estimate the diffusion tensor more accurately than most existing methods operating at higher net acceleration factors. The proposed method can significantly reduce artifact, particularly at higher acceleration factors or lower SNRs. This method can easily be adapted to MR relaxometry parameter mapping and is thus useful in the characterization of biological tissue such as nerves, muscle, and heart tissue.

Gd-EOB-DTPA-enhanced MR relaxometry for the detection and staging of liver fibrosis

Gd-EOB-DTPA, a liver-specific contrast agent with T1-shortening effects, is routinely used in clinical routine for detection and characterization of focal liver lesions and has recently received increasing attention as a tool for the quantitative analyses of liver function. We report the relationship between the extent of Gd-EOB-DTPA- induced T1 relaxation and the degree of liver fibrosis, which was assessed according to the METAVIR score. For the T1 relaxometry, a transverse 3D VIBE sequence with inline T1 calculation was acquired prior to and 20 minutes after Gd-EOB-DTPA administration. The reduction rates of the T1 relaxation time (rrT1) between the pre- and postcontrast images were calculated, and the optimal cutoff values for the fibrosis stages were determined with receiver operating characteristic (ROC) curve analyses. The rrT1 decreased with the severity of liver fibrosis and regression analysis revealed a significant correlation of the rrT1 with the stage of liver fibrosis (r = −0.906, p < 0.001). ROC analysis revealed sensitivities ≥78% and specificities ≥94% for the differentiation of different fibrosis stages. Gd-EOB-DTPA–enhanced T1 relaxometry is a reliable tool for both the detection of initial hepatic fibrosis and the staging of hepatic fibrosis.

Transverse Relaxation Rate of Cyst Fluid Can Predict Malignant Transformation of Ovarian Endometriosis.

Purpose:Heme and iron accumulation due to repeated hemorrhage in endometriosis may contribute to a pivotal role in carcinogenesis. We evaluate the clinical application of MR relaxometry in a series of ovarian endometriosis (OE) and endometriosis-associated ovarian cancer (EAOC).Materials and Methods:A prospective study of diagnostic accuracy was conducted among 82 patients (67 OE and 15 EAOC) to compare MR relaxometry and biochemical measurement of cyst fluid total iron concentration. Transverse relaxation rate R2 value was determined using a single-voxel, multi-echo MR sequence (HISTO) by a 3T-MR system. Phantom experiments were also performed to assess the correlation between the ex vivo R2 values and total iron concentrations.Results:Both the results of phantom experiments and in vivo human data confirmed that in vivo R2 values were highly correlated with total iron concentrations. Compared to OE, EAOC exhibit decreased in vivo R2 values and total iron levels, regardless of their age, menopausal status and cyst size. The use of in vivo R2 values retained excellent accuracy in distinguishing EAOC versus OE (sensitivity and specificity: 86% and 94%).Conclusions:We have demonstrated that MR relaxometry provides a noninvasive predictive tool to discriminate between EAOC and OE.

Volume of Interest Analysis of Spatially Normalized PRESTO Imaging to Differentiate between Parkinson Disease and Atypical Parkinsonian Syndrome.

Purpose:Various magnetic resonance imaging (MRI) techniques including T2*-weighted imaging, susceptibility-weighted imaging, and MR relaxometry had been performed to evaluate different patterns of brain iron depositions in Parkinsonian syndrome. The aim of the present study was to evaluate the diagnostic value of a volume of interest (VOI) analysis on the principles of echo shifting with a train of observations (PRESTO) imaging using the statistical parametric mapping (SPM) 8 and the WFU PickAtlas program for the diagnosis of Parkinsonian syndrome.Methods:Fifty subjects, including 13 with the Parkinsonian variant of multiple system atrophy (MSA-P), 12 with progressive supranuclear palsy (PSP), 12 with Parkinson’s disease (PD) and 13 controls were evaluated in this study. After the spatial normalization of PRESTO images on SPM8, the WFU PickAtlas program was performed to create target VOIs in the putamen, red nucleus, substantia nigra, subthalamic nucleus, and dentate nucleus. The signal intensity ratio (SIR) was calculated by normalizing the signal of each VOI to that of the cerebrospinal fluid space. These SIRs were used as determinants in receiver operating characteristic (ROC) analyses.Results:SIR of the putamen was significantly lower in MSA-P than in PSP (P = 0.0051) and controls (P = 0.0004). In contrast, SIR of the red nucleus was significantly lower in PSP than in MSA-P (P = 0.0003), PD (P = 0.0029), and controls (P = 0.0011). In ROC analyses, SIR of the putamen exhibited the highest areas under the curves (AUCs) of 0.83 (vs. PSP) and 0.91 (vs. controls) in the diagnosis of MSA-P. On the other hand, SIR of the red nucleus exhibited the highest AUCs of 0.87 (vs. MSA-P), 0.90 (vs. PD), and 0.89 (vs. controls) in the diagnosis of PSP.Conclusions:The VOI analysis based on spatially normalized PRESTO images may be useful for depicting hypointensity, indicative of abnormal iron depositions, of the putamen and red nucleus in the diagnosis of MSA-P and PSP.

Buy one, get two for free: simultaneous knee T2 mapping and morphological analysis on synthetic images using grappatini

Introduction: Today, intermediate-weighted (IW) and T2-weighted (T2w) Turbo Spin Echo (TSE) sequences with fat suppression are most commonly used to clinically assess morphological abnormalities of joint structures. In addition, quantitative analysis of the musculoskeletal system using MR relaxometry techniques such as T2 mapping has gained interest in recent years. This is in particular the case for imaging of osteoarthritis, since T2 values can be used as a non-invasive biomarker of early degenerative disease of cartilage and meniscus. The acquisition of both morphological and quantitative sequences is however time consuming. We suggest using a fast quantitative T2 mapping technique that allows the generation of synthetic images with different TEs, allowing a significant decrease in acquisition time while preserving image quality in comparison to the consecutive acquisition of morphological and quantitative sequences.

Superparamagnetic Fe3O4 Nanoparticles: Synthesis by Thermal Decomposition of Iron(III) Glucuronate and Application in Magnetic Resonance Imaging.

Monodisperse superparamagnetic Fe3O4 nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe3O4 nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis(ethane-2,1-diyl)phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG-P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG-P&Fe3O4 nanoparticles were tested on rat mesenchymal stem cells to determine the particle toxicity and their ability to label the cells. MR relaxometry confirmed that the PMG-P&Fe3O4 nanoparticles had high relaxivity but rather low cellular uptake. Nevertheless, the labeled cells still provided visible contrast enhancement in the magnetic resonance image. In addition, the cell viability was not compromised by the nanoparticles. Therefore, the PMG-P&Fe3O4 nanoparticles have the potential to be used in biomedical applications, especially as contrast agents for magnetic resonance imaging.

In vivo dentate nucleus MRI relaxometry correlates with previous administration of Gadolinium-based contrast agents.

To evaluate changes in T1 and T2* relaxometry of dentate nuclei (DN) with respect to the number of previous administrations of Gadolinium-based contrast agents (GBCA). In 74 relapsing-remitting multiple sclerosis (RR-MS) patients with variable disease duration (9.8±6.8 years) and severity (Expanded Disability Status Scale scores:3.1±0.9), the DN R1 (1/T1) and R2* (1/T2*) relaxation rates were measured using two unenhanced 3D Dual-Echo spoiled Gradient-Echo sequences with different flip angles. Correlations of the number of previous GBCA administrations with DN R1 and R2* relaxation rates were tested, including gender and age effect, in a multivariate regression analysis. The DN R1 (normalized by brainstem) significantly correlated with the number of GBCA administrations (p<0.001), maintaining the same significance even when including MS-related factors. Instead, the DN R2* values correlated only with age (p=0.003), and not with GBCA administrations (p=0.67). In a subgroup of 35 patients for whom the administered GBCA subtype was known, the effect of GBCA on DN R1 appeared mainly related to linear GBCA. In RR-MS patients, the number of previous GBCA administrations correlates with R1 relaxation rates of DN, while R2* values remain unaffected, suggesting that T1-shortening in these patients is related to the amount of Gadolinium given. • In multiple sclerosis, previous Gadolinium administrations correlate with dentate nuclei T1 relaxometry. • Such correlation is linked to linear Gadolinium chelates and unrelated to disease duration or severity. • Dentate nuclei T2* relaxometry is age-related and independent of previous Gadolinium administrations. • Changes in dentate nuclei T1 relaxometry are not determined by iron accumulation. • MR relaxometry can quantitatively assess Gadolinium accumulation in dentate nuclei.

T1 correlates age: A short-TE MR relaxometry study in vivo on human cortical bone free water at 1.5 T

Large pores of human cortical bone (>30μm) are filled with fluids, essentially consisting of water, suggesting that cortical bone free water can be considered as a reliable surrogate measure of cortical bone porosity and hence quality. Signal from such pores can be reliably captured using Short Echo Time (STE) pulse sequence with echo-time in the range of 1–1.5msec (which should be judiciously selected correspond to T2⁎ value of free water molecules). Furthermore, it is well-known that cortical bone T1-relaxivity is a function of its geometry, suggesting that cortical bone free water increases with age. In this work, we quantified cortical bone free water longitudinal relaxation time (T1) by a Dual-TR technique using STE pulse sequence. In the sequel, we investigated relationship between STE-derived cortical bone free water T1-values and age in a group of healthy volunteers (thirty subjects covering the age range of 20–70years) at 1.5T. Preliminary results showed that cortical bone free water T1 highly correlates with age (r2=0.73, p<0.0001), representing cortical bone free water T1 as a reliable indicator of cortical bone porosity and age-related deterioration. It can be concluded that STE-MRI can be utilized as proper alternative in quantifying cortical bone porosity parameters in-vivo, with the advantages of widespread clinical availability and being cost-effective.

Magnetic resonance imaging of pathogenic protozoan parasite Entamoeba histolytica labeled with superparamagnetic iron oxide nanoparticles.

The aim of this study was to establish a noninvasive tracking of the pathogenic parasite Entamoeba histolytica (Eh) after superparamagnetic iron oxide (SPIO) labeling by magnetic resonance imaging (MRI) on a single-cell level in vitro and in vivo in a mouse model for amebic liver abscess (ALA). Local institutional review committee on animal care approved all animal experiments. Entamoeba histolytica trophozoites were labeled with SPIO nanoparticles (SPIO-Eh). The uptake of SPIO by Eh was optimized using flow cytometry and visualized by bright field, fluorescence, and transmission electron microscopy. The viability of SPIO-Eh was assessed in vitro by determination of growth and ingestion rate of red blood cells. Migration of SPIO-Eh was proven by in vitro MRI in a preclinical 7 T MRI system using continually repeated MRI scans. In vivo distribution of SPIO-Eh within the mouse liver was assessed qualitatively and quantitatively by serial respiration-triggered T2*-weighted MRI, T2-weighted MRI, and R2* MR relaxometry up to 5 days after injection and correlated with immunohistology of the liver sections after removal. Entamoeba histolytica can be efficiently labeled with SPIO without influence on parasite growth rate or phagocytic capacity. In vitro dynamic MRI allowed real-time migration monitoring and determination of velocity of single SPIO-Eh. In vivo SPIO-Eh showed signal decrease in T2*-weighted and increase of R2* in ALA formations. Motility of SPIO-Eh was necessary to induce ALA formations. The present study demonstrates the feasibility of an efficient magnetic labeling and a noninvasive in vitro and in vivo MR tracking of the pathogenic protozoan Eh in a mouse model for ALA, thus representing in future a noninvasive imaging tool to study parasite, as well as on host-specific pathomechanisms.