Reproducibility Of T1 Research Articles

Are T1-Weighted Three-Dimensional Magnetic Resonance Images Inferior to T2-Weighted Images for Diagnosing Lumbar Foraminal Stenosis in the Fifth Lumbar Nerve Root? A Prospective, Comparative Study in Identical Patients.

Imaging analysis of foraminal stenosis in the fifth lumbar (L5) nerve root remains to be a challenge because of the anatomical complexity of the lumbosacral transition. T2-weighted three-dimensional (3D) magnetic resonance images (MRI) have been dominantly used for diagnosis of lumbar foraminal stenosis, while the reliability of T1-weighted images (WI) has also been proven. In this study, we aim to compare the reliability and reproducibility of T1- and T2-weighted 3D MRI in diagnosing lumbar foraminal stenosis (LFS) of the L5 nerve root. In this study, 39 patients with unilateral L5 radiculopathy (20 had L4-L5 intracanal stenosis; 19 had L5-S foraminal stenosis) were enrolled, prospectively. T1- and T2-weighted 3D lumbar MRI were obtained from each patient. T1WI and T2WI were blinded and then separately reviewed twice by four examiners randomly. The examiners were instructed to answer the side of LFS or absence of LFS. The correct answer rate, sensitivity, specificity, and area under the curve were analyzed and compared between T1WI and T2WI. Also, intra- and interobserver agreements were calculated using kappa (κ)-statistics and compared in the same manner. The average correct answer rate, sensitivity, specificity, and area under the curve of the T1WI/T2WI were 84.6%/80.1%, 82.9%/80.3%, 86.3%/81.3%, and 0.846/0.801, respectively. The intraobserver κ-values of the four examiners ranged from 0.692 to 0.916 (average: 0.762) and from 0.669 to 0.801 (average: 0.720) for T1WI and T2WI, respectively. The interobserver κ-values calculated in a round-robin manner (24 combinations in total) ranged from 0.544 to 0.790 (average: 0.657) and from 0.524 to 0.828 (average: 0.652), respectively. As per our findings, T1- and T2-weighted 3D MRI were determined to have nearly equivalent reliability and reproducibility in terms of diagnosing LFS of the L5 nerve root.

Accuracy, repeatability, and reproducibility of T1 and T2 relaxation times measurement by 3D magnetic resonance fingerprinting with different dictionary resolutions

ObjectivesTo assess the accuracy, repeatability, and reproducibility of T1 and T2 relaxation time measurements by three-dimensional magnetic resonance fingerprinting (3D MRF) using various dictionary resolutions.MethodsThe ISMRM/NIST phantom was scanned daily for 10 days in two 3 T MR scanners using a 3D MRF sequence reconstructed using four dictionaries with varying step sizes and one dictionary with wider ranges. Thirty-nine healthy volunteers were enrolled: 20 subjects underwent whole-brain MRF scans in both scanners and the rest in one scanner. ROI/VOI analyses were performed on phantom and brain MRF maps. Accuracy, repeatability, and reproducibility metrics were calculated.ResultsIn the phantom study, all dictionaries showed high T1 linearity to the reference values (R2 > 0.99), repeatability (CV < 3%), and reproducibility (CV < 3%) with lower linearity (R2 > 0.98), repeatability (CV < 6%), and reproducibility (CV ≤ 4%) for T2 measurement. The volunteer study demonstrated high T1 reproducibility of within-subject CV (wCV) < 4% by all dictionaries with the same ranges, both in the brain parenchyma and CSF. Yet, reproducibility was moderate for T2 measurement (wCV < 8%). In CSF measurement, dictionaries with a smaller range showed a seemingly better reproducibility (T1, wCV 3%; T2, wCV 8%) than the much wider range dictionary (T1, wCV 5%; T2, wCV 13%). Truncated CSF relaxometry values were evident in smaller range dictionaries.ConclusionsThe accuracy, repeatability, and reproducibility of 3D MRF across various dictionary resolutions were high for T1 and moderate for T2 measurements. A lower-resolution dictionary with a well-defined range may be adequate, thus significantly reducing the computational load.Key Points• A lower-resolution dictionary with a well-defined range may be sufficient for 3D MRF reconstruction.• CSF relaxation times might be underestimated due to truncation by the upper dictionary range.• Dictionary with a higher upper range might be advisable, especially for CSF evaluation and elderly subjects whose perivascular spaces are more prominent.

Multicenter Repeatability and Reproducibility of MR Fingerprinting in Phantoms and in Prostatic Tissue.

PurposeTo evaluate multicenter repeatability and reproducibility of T1 and T2 maps generated using MR fingerprinting (MRF) in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and in prostatic tissues.MethodsMRF experiments were performed on 5 different 3 Tesla MRI scanners at 3 different institutions: University Hospitals Cleveland Medical Center (Cleveland, OH), Brigham and Women's Hospital (Boston, MA) in the United States, and Diagnosticos da America (Rio de Janeiro, RJ) in Brazil. Raw MRF data were reconstructed using a Gadgetron‐based MRF online reconstruction pipeline to yield quantitative T1 and T2 maps. The repeatability of T1 and T2 values over 6 measurements in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom was assessed to demonstrate intrascanner variation. The reproducibility between the 4 clinical scanners was assessed to demonstrate interscanner variation. The same‐day test–retest normal prostate mean T1 and T2 values from peripheral zone and transitional zone were also compared using the intraclass correlation coefficient and Bland–Altman analysis.ResultsThe intrascanner variation of values measured using MRF was less than 2% for T1 and 4.7% for T2 for relaxation values, within the range of 307.7 to 2360 ms for T1 and 19.1 to 248.5 ms for T2. Interscanner measurements showed that the T1 variation was less than 4.9%, and T2 variation was less than 8.1% between multicenter scanners. Both T1 and T2 values in in vivo prostatic tissue demonstrated high test–retest reliability (intraclass correlation coefficient > 0.92) and strong linear correlation (R 2 > 0.840).ConclusionProstate MRF measurements of T1 and T2 are repeatable and reproducible between MRI scanners at different centers on different continents for the above measurement ranges.

Determining the longitudinal accuracy and reproducibility of T1 and T2 in a 3T MRI scanner.

PurposeTo determine baseline accuracy and reproducibility of T1 and T2 relaxation times over 12 months on a dedicated radiotherapy MRI scanner.MethodsAn International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) System Phantom was scanned monthly on a 3T MRI scanner for 1 year. T1 was measured using inversion recovery (T1‐IR) and variable flip angle (T1‐VFA) sequences and T2 was measured using a multi‐echo spin echo (T2‐SE) sequence. For each vial in the phantom, accuracy errors (%bias) were determined by the relative differences in measured T1 and T2 times compared to reference values. Reproducibility was measured by the coefficient of variation (CV) of T1 and T2 measurements across monthly scans. Accuracy and reproducibility were mainly assessed on vials with relaxation times expected to be in physiological ranges at 3T.ResultsA strong linear correlation between measured and reference relaxation times was found for all sequences tested (R 2 > 0.997). Baseline bias (and CV[%]) for T1‐IR, T1‐VFA and T2‐SE sequences were +2.0% (2.1), +6.5% (4.2), and +8.5% (1.9), respectively.ConclusionsThe accuracy and reproducibility of T1 and T2 on the scanner were considered sufficient for the sequences tested. No longitudinal trends of variation were deduced, suggesting less frequent measurements are required following the establishment of baselines.

Comprehensive Evaluation of B&lt;sub&gt;1&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;-corrected FISP-based Magnetic Resonance Fingerprinting: Accuracy, Repeatability and Reproducibility of T&lt;sub&gt;1&lt;/sub&gt; and T&lt;sub&gt;2&lt;/sub&gt; Relaxation Times for ISMRM/NIST System Phantom and Volunteers

Purpose:This study aimed to evaluate comprehensively; accuracy, repeatability and reproducibility of T1 and T2 relaxation times measured by magnetic resonance fingerprinting using -corrected fast imaging with steady-state precession (FISP–MRF).Methods:The International Society of Magnetic Resonance in Medicine/National Institute of Standards and Technology (ISMRM/NIST) phantom was scanned for 100 days, and six healthy volunteers for 5 days using a FISP–MRF prototype sequence. Accuracy was evaluated on the phantom by comparing relaxation times measured by FISP–MRF with the reference values provided by the phantom manufacturer. Daily repeatability was characterized as the coefficient of variation (CV) of the measurements over 100 days for the phantom and over 5 days for volunteers. In addition, the cross-scanner reproducibility was evaluated in volunteers.Results:In the phantom study, T1 and T2 values from FISP–MRF showed a strong linear correlation with the reference values of the phantom (R2 = 0.9963 for T1; R2 = 0.9966 for T2). CVs were <1.0% for T1 values larger than 300 ms, and <3.0% for T2 values across a wide range. In the volunteer study, CVs for both T1 and T2 values were <5.0%, except for one subject. In addition, all T2 values estimated by FISP–MRF in vivo were lower than those measured with conventional mapping sequences reported in previous studies. The cross-scanner variation of T1 and T2 showed good agreement between two different scanners in the volunteers.Conclusion:-corrected FISP-MRF showed an acceptable accuracy, repeatability and reproducibility in the phantom and volunteer studies.

Reproducibility of in vivo magnetic resonance imaging T1 rho and T2 relaxation time measurements of hip cartilage at 3.0T in healthy volunteers.

To assess the T1 ρ and T2 values in the hip cartilage of healthy volunteers and to evaluate the reproducibility of these measurements. The right hip joint of 30 asymptomatic volunteers was explored with 3T magnetic resonance imaging (MRI). Quantitative 3D T1 ρ- and T2 -maps sequences were repeated twice with a 30-minute delay (immediate reproducibility). The same protocol was repeated 14 days later (short-term reproducibility). Immediate and short-term reproducibility were estimated using coefficients of variation and correlation concordance coefficients (CCC). The precisions of the measurements were estimated by the ratio of the standard deviations. A mixed linear model was used to analyze the effect of patient's characteristics on T1 ρ and T2 values. Immediate reproducibility was significantly better than short-term reproducibility for T1 ρ (CCC of 0.75 versus 0.55; P = 0.007) and T2 (CCC 0.65 versus 0.32; P < 0.001). The precisions of the measurements were estimated between 5.5% and 9.1%. Median T1 ρ values were 6.0 msec higher in women than in men (P = 0.006), with no significant influence of age, body mass index (BMI), or sports activity. Median T2 values were not significantly different between men and women (0.4 msec lower in women; P = 0.76). There was no significant influence of age, BMI, or sports activity. T1 ρ and T2 values were lower in lateral regions than in medial regions (4.9 msec and 2.5 msec lower respectively; P < 0.0001). Immediate reproducibility of T1 ρ and T2 values is better than short-term, with limited effect of 30 minutes decubitus. T1 ρ values are significantly higher in women. 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1022-1033.

Modified look-locker inversion recovery T1 mapping indices: assessment of accuracy and reproducibility between MRI scanners

Background Cardiac magnetic resonance (CMR) T1 mapping indices, including T1 time, partition coefficient (l), and extracellular volume fraction (ECV) measurements, are a group of emerging noninvasive, quantitative imaging biomarkers that can be used to assess diffuse myocardial fibrosis. Similar to other quantitative MRI measurements, T1 mapping results can be influenced by multiple scanner dependent factors, such as field strength, gradient systems, coil configuration, pulse sequence design, and artifacts related to field inhomogeneity and eddy currents. The purpose of this ex-vivo phantom, multicenter study was to investigate how scanner and field strength variation affected the accuracy and precision of T1 mapping indices. Methods MR studies were performed on two 1.5T (1 Philips, 1 Siemens) and three 3T (2 Philips, 1 Siemens) scanners. Two sets of four phantoms were made to mimic the T1/T2 of pre- and post-contrast myocardium and blood at 1.5T and 3T. T1 mapping using modified look locker with inversion recovery (MOLLI) was performed with simulated heart rate of 40-100bpm using a standard 17 heart beat and a shorter 11 heart beat MOLLI protocol. Inversion recovery spin echo (IR-SE) sequence with TR = 10 sec was acquired during the same session to estimate the reference T1. The phantoms were taken out the magnet after IR-SE and all MOLLI protocols were re-scanned after 10 min to evaluate inter-scan reproducibility. The partition coefficient (l) was estimated by ΔR1myocardium/ΔR1blood. General linear model was used to compare the accuracy and reproducibility of T1 and l across field strength, scanners and protocols. Results The IR-SE T1 values were significantly different across scanners within the same field strength. The average partition coefficient estimated from IR-SE was 43.7% (1.5T) and 46.0% (3T), similar to normal in-vivo values. Accuracy was defined as the percent error between MOLLI and IR-SE, and scan/re-scan reproducibility was reported as the relative percent mean difference between the two back to back MOLLI scans. T1 and l accuracy both varied significantly between different scanners (p<0.0001 for both T1 and l) and across heart rates (p<0.0001 for T1 and p=0.001 for l). However, neither varied across the standard 17HB and 11HB protocols (p=0.177 for T1 and p=0.574 for lamda). Additionally, field strength significantly affected T1 accuracy but not l accuracy (p<0.0001 for T1 vs. p=0.109 for l). In addition to less variability in accuracy, l also had lower percent error overall between scan repetitions, or higher scan/re-scan reproducibility, than T1 measurements (4.59% vs. 5.54%).

Deuterium NMR Study of Unstable Phenomena and Water Molecular Dynamics in Samarium Nitrate Hexahydrate Crystal

Deuterium NMR spectra, spin−lattice relaxation time T1, and differential thermal analysis (DTA) were measured for Sm(NO3)3·6D2O. The magnetization recovery can be divided into two components. From deuterium NMR spectra and T1, the short and the long components of T1 were found to be mainly dominated by the 180° flip of the crystallization and the coordinated water molecules, respectively. For the nonannealed sample, the reproducibility of T1 was observed. The influence of the instability was not seen in the long component of T1. The results of the long component of T1 gave the activation energy Ea = 20 kJ mol-1 and the correlation time at infinite temperature τc0 = 7.8 × 10-12 s for the 180° flip of the coordinated water molecule. The motion of the crystallization water at low temperatures can be explained by the 180° flip in the asymmetric double minimum potential. τc0 = 1.2 × 10-12 s, Ea = 16 kJ mol-1, and the energy difference in the potential wells ΔE = 2.0 kJ mol-1 were obtained for the 180° flip of ...

Reproducibility of relaxation and spin-density parameters in phantoms and the human brain measured by MR imaging at 1.5 T.

The reproducibility of T1, T2, and proton density, measured in phantoms and the human brain was evaluated by proton imaging techniques. The sequence used to derive T1 and density values was a multiple-saturation recovery which consists of four pairs of 90 degrees pulses, followed by a 180 degrees phase reversal pulse, generating four T1-weighted images. T2 was derived from a multiple-echo sequence, generating four T2-weighted images. The data were analyzed by fitting the pixel intensities to the respective equations by means of nonlinear multiparameter least-squares analysis. Short-term reproducibility between four consecutive scans was evaluated to be 1-4% depending on location with a phantom covering the entire span of physiologic T1 and T2 values. A second phantom containing a series of identical samples served to study the dependence of the apparent T1 and T2 on position, both radially and axially, with respect to magnet isocenter. Reproducibility across the field of view was found to be better than 7% (T1 and T2). This phantom was further used to evaluate effects of long-term reproducibility, which at each location varied from 5-14% (T1) and 2-10% (T2). Finally, interinstrument reproducibility, tested by means of the same protocol on three different instruments, all operating at the same magnetic field and using largely identical hardware for each location, was found to be 1-14% (T1) and 2-10% (T2). The positional dependence of the apparent relaxation times appears to be systematic and may be due to variations in the effective field, caused by magnet and rf inhomogeneity. Finally, brain tissue relaxation and spin-density data were determined using the same protocol in 37 scans performed on 27 normal volunteers. The tissues analyzed were putamen, thalamus, caudate nucleus, centrum semiovale, internal capsule, and corpus callosum. Excellent accordance was further obtained between left and right hemispheres.

Reproducibility of T1 and T2 relaxation times calculated from routine MR imaging sequences: phantom study.

Measurement of T1 and T2 relaxation times has been sought as one fundamental way to characterize tissue. Relaxation times can be calculated from routine spin-echo (SE) imaging sequences using two distinct repetition times (TRs), each with two SE samplings of signal intensity. Previous reports have quantified relaxation times without discussing the variation in their measurements. By imaging a phantom containing different samples with known T1 and T2 relaxation times on three separate occasions, the variation in relaxation time measurements inherent in different routine imaging sequences was studied. For the present study a more complete and accurate equation was used to calculate T1 values. The variation in T1 and T2 relaxation times for samples with relaxation times similar to solid tissue was 2%-4%. The amount of variability in calculated relaxation times was found to be dependent on the magnitude of the relaxation times themselves. However, the mean values were independent of the imaging sequences used to calculate the relaxation times. No significant differences were seen between left-to-right or section-to-section position within the same study or between studies performed on different occasions. The variability in the calculated T1 was dependent on the pair of TR sequences used to calculate T1. Samples with long T1 and T2 relaxation times, similar to many body fluids, had much larger variability. A computer simulation of measurement error was created to explain these results. This study indicates that properly performed routine imaging studies do yield reproducible T1 and T2 measurements.