Conventional Spin-echo Sequences Research Articles

Magnetic resonance imaging subtraction vs. pre- and post-contrast 3D gradient recalled echo fat suppressed imaging for evaluation of the canine and feline brain.

Subtraction magnetic resonance imaging (MRI) has been reported to increase accuracy in the diagnosis of meningeal and inflammatory brain diseases in small animals. 3D T1W gradient recalled echo (GRE) techniques have been proposed as a suitable alternative to conventional spin echo sequences in imaging the canine brain. The aim of this study was to compare subtraction images and paired pre- and post-contrast 3D T1W GRE fat suppressed (FS) images in canine and feline MRI studies using clinical diagnosis as the gold standard. Paired pre- and post-contrast T1W 3D FS GRE images and individual subtraction images of 100 small animal patients were randomized and independently evaluated by 2 blinded observers. Diagnosis categories were "normal," "inflammatory," "neoplastic," and "other." Clinical diagnosis was made in the same categories and served as the gold standard. Image interpretation results were compared to the clinical diagnosis. Interobserver agreement was determined. Clinically, 41 studies were categorized as "normal," 18 as "inflammatory," 28 as "neoplastic," and 13 as "other." The agreement of the pre- and post-contrast GRE images with the gold standard was significantly higher than that of the subtraction images (k = 0.7491 vs. k = 0.5924; p = 0.0075). The largest sources of error were misinterpretation of "other" as "normal" and "normal" as "inflammatory." There was no significant difference between the two observers (p = 0.8820). Based on this study, subtraction images do not provide an advantage to paired pre- and post-contrast FS GRE images when evaluating the canine and feline brain.

7 T Lesion-Attenuated Magnetization-Prepared Gradient Echo Acquisition for Detection of Posterior Fossa Demyelinating Lesions in Multiple Sclerosis.

Detection of infratentorial demyelinating lesions in multiple sclerosis (MS) presents a challenge in magnetic resonance imaging (MRI), a difficulty that is further heightened in 7 T MRI. This study aimed to assess the efficacy of a novel MRI approach, lesion-attenuated magnetization-prepared gradient echo acquisition (LAMA), for detecting demyelinating lesions within the posterior fossa and upper cervical spine on 7 T MRI and contrast its performance with conventional double-inversion recovery (DIR) and T2-weighted turbo spin echo sequences. We conducted a retrospective cross-sectional study in 42 patients with a confirmed diagnosis of MS. All patients had 7 T MRI that incorporated LAMA, 3D DIR, and 2D T2-weighted turbo spin echo sequences. Three readers assessed lesion count in the brainstem, cerebellum, and upper cervical spinal cord using both DIR and T2-weighted images in one session. In a separate session, LAMA was analyzed alone. Contrast-to-noise ratio was also compared between LAMA and the conventional sequences. Lesion counts between methods were assessed using nonparametric Wilcoxon signed rank test. Interrater agreement in lesion detection was estimated by intraclass correlation coefficients. LAMA identified a significantly greater number of lesions than DIR + T2 (mean 6.4 vs 3.0; P < 0.001). LAMA also exhibited better interrater agreement (intraclass correlation coefficient [95% confidence interval], 0.75 [0.41-0.88] vs 0.61 [0.35-0.78]). The contrast-to-noise ratio for LAMA (3.7 ± 0.9) significantly exceeded that of DIR (1.94 ± 0.7) and T2 (1.2 ± 0.7) (all P's < 0.001). In cases with no lesions detected using DIR + T2, at least 1 lesion was identified in 83.3% with LAMA. Across all analyzed brain regions, LAMA consistently detected more lesions than DIR + T2. LAMA significantly improves the detection of infratentorial demyelinating lesions in MS patients compared with traditional methods. Integrating LAMA with standard magnetization-prepared 2 rapid acquisition gradient echo acquisition provides a valuable tool for accurately characterizing the extent of MS disease.

Ultrashort echo time pulse sequences for visualization of deep peripheral fasciae and epimysium in porcine models with histologic correlations.

The deep peripheral fascia and epimysium are vital for muscle and tendon support, but their tight proton composition results in hypointense signals in conventional spin echo sequences. Ultrashort echo time (UTE) magnetic resonance imaging (MRI), using microsecond TE values, may visualize these structures. The purpose of this study was to evaluate whether UTE pulse sequence with a three-dimensional cone trajectory (3D UTE), with or without fat suppression (FS), can be used to visualize the fascia and epimysium using porcine lower legs as an example. The anterior soft tissues of porcine lower legs were dissected and partially separated into distinct layers to expose the deep peripheral fascia, epimysium, and muscle. Axial 3D UTE and 3D UTE FS imaging using dual-echo acquisition and echo subtraction were performed both before and after dissection. Prior to dissection, the thickness, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) of structures believed to be deep peripheral fascia and epimysium were measured in both 3D UTE and 3D UTE FS. Post-dissection images were also analyzed to measure the SNRs and CNRs for the deep peripheral fascia and epimysium. Histological evaluations were carried out to verify the identities of the deep peripheral fascia and epimysium, as well as their thickness, and these measurements were compared to imaging findings. In pre-dissection images obtained with 3D UTE and 3D UTE FS, both the deep peripheral fascia and epimysium exhibited high signal intensity. In the subtraction images, the mean thickness of the deep fascia was 0.87 mm, and that of the epimysium was 0.80 mm when imaged with 3D UTE. This is compared to measurements of 0.77 and 0.22 mm in 3D UTE FS, respectively. Histological analyses confirmed the thickness of the deep peripheral fascia and epimysium as 0.65 and 0.14 mm, respectively. In the post-dissection images, the deep fascia continued to display high signal intensity when compared with adjacent soft tissues, consistent with the histological findings. Meanwhile, the epimysium showed very low CNRs. 3D UTE and 3D UTE FS can be used to visualize the deep peripheral fascia with high signal intensity and contrast but are insufficient to show signal intensity in the epimysium.

Differentiating brain metastasis from glioblastoma by time-dependent diffusion MRI

BackgroundThis study was designed to investigate the use of time-dependent diffusion magnetic resonance imaging (MRI) parameters in distinguishing between glioblastomas and brain metastases.MethodsA retrospective study was conducted involving 65 patients with glioblastomas and 27 patients with metastases using a diffusion-weighted imaging sequence with oscillating gradient spin-echo (OGSE, 50 Hz) and a conventional pulsed gradient spin-echo (PGSE, 0 Hz) sequence. In addition to apparent diffusion coefficient (ADC) maps from two sequences (ADC50Hz and ADC0Hz), we generated maps of the ADC change (cADC): ADC50Hz − ADC0Hz and the relative ADC change (rcADC): (ADC50Hz − ADC0Hz)/ ADC0Hz × 100 (%).ResultsThe mean and the fifth and 95th percentile values of each parameter in enhancing and peritumoral regions were compared between glioblastomas and metastases. The area under the receiver operating characteristic curve (AUC) values of the best discriminating indices were compared. In enhancing regions, none of the indices of ADC0Hz and ADC50Hz showed significant differences between metastases and glioblastomas. The mean cADC and rcADC values of metastases were significantly higher than those of glioblastomas (0.24 ± 0.12 × 10−3mm2/s vs. 0.14 ± 0.03 × 10−3mm2/s and 23.3 ± 9.4% vs. 14.0 ± 4.7%; all p < 0.01). In peritumoral regions, no significant difference in all ADC indices was observed between metastases and glioblastomas. The AUC values for the mean cADC (0.877) and rcADC (0.819) values in enhancing regions were significantly higher than those for ADC0Hz5th (0.595; all p < 0.001).ConclusionsThe time-dependent diffusion MRI parameters may be useful for differentiating brain metastases from glioblastomas.

Fast spin-echo approach for accelerated B1 gradient-based MRI.

To expand on the previously developed -encoding technique, frequency-modulated Rabi-encoded echoes (FREE), to perform accelerated image acquisition by collecting multiple lines of k-space in an echo train. FREE uses adiabatic full-passage pulses and a spatially varying RF field to encode unique spatial information without the use of traditional B0 gradients. The original implementation relied on acquiring single lines of k-space, leading to long acquisitions. In this work, an acceleration scheme is presented in which multiple echoes are acquired in a single shot, analogous to conventional fast spin-echo sequences. Theoretical analysis and computer simulations investigated the feasibility of this approach and presented a framework to analyze important imaging parameters of FREE-based sequences. Experimentally, the multi-echo approach was compared with conventional phase-encoded images of the human visual cortex using a simple surface transceiver coil. Finally, different contrasts demonstrated the clinical versatility of the new accelerated sequence. Images were acquired with an acceleration factor of 3.9, compared with the previous implementation of FREE, without exceeding specific absorption rate limits. Different contrasts can easily be acquired without major modifications, including inversion recovery-type images. FREE initially illustrated the feasibility of performing slice-selective 2D imaging of the human brain without the need for a B0 gradient along the y-direction. The multi-echo version maintains the advantages that encoding provides but represents an important step toward improving the clinical feasibility of such sequences. Additional acceleration and more advanced reconstruction techniques could further improve the clinical viability of FREE-based techniques.

A polynomial regression-based approach to estimate relaxation rate maps suitable for multiparametric segmentation of clinical brain MRI studies in multiple sclerosis

Background and ObjectiveRelaxation parameter maps (RPMs) calculated from spin-echo data have provided a basis for the segmentation of normal brain tissues and white matter lesions in multiple sclerosis (MS) MRI studies. However, Conventional Spin-Echo (CSE) sequences, once the core of clinical MRI studies, have been largely replaced by faster ones, which do not allow the calculation a-posteriori of RPMs from clinical studies. Aim of the study was to develop and validate a method to estimate RPMs (pseudo-RPMs) from routine clinical MRI protocols (including 3D-Gradient Echo T1w, FLAIR and fast-T2w sequences), suitable for fully automatic multiparametric segmentation of normal-appearing and pathological brain tissues in MS. MethodsThe proposed method processes spatially normalized clinical MRI studies through a multistep pipeline, to collect a set of data points of matched signal intensities (from MRI studies) and relaxation parameters (from a CSE-derived digital template and an MS lesion database), which are then fitted by a multiple and multivariate 4-th degree polynomial regression, providing pseudo-RPMs. The method was applied to a dataset of 59 clinical MRI studies providing pseudo-RPMs that were segmented through a method originally developed for the CSE-derived RPMs. Results of the segmentation in 12 studies were used to iteratively optimize method parameters. Accuracy of segmentation of normal-appearing brain tissues from the pseudo-RPMs was assessed by comparing their age-related changes, as measured in 47 clinical studies, against those measured acquired using CSE sequences in a comparable dataset of 47 patients. Lesion segmentation was validated against manual segmentation carried out by three neuroradiologists. ResultsAge-related changes of normal-appearing brain tissue volumes measured using the pseudo-RPMs substantially overlapped those measured using the RPMs obtained from CSE sequences, and segmentation of MS lesions showed a moderate-high spatial overlap with manual segmentation, comparable to that achieved by the widely used Lesion Segmentation Tool on FLAIR images, with a greater volumetric agreement. ConclusionsThe proposed approach allows calculation from clinical studies of pseudo-RPMs, which are equivalent to those obtainable from CSE sequences, avoiding the need for the acquisition of additional, dedicated sequences for segmentation purposes.

Assessment of 2D conventional and synthetic MRI in multiple sclerosis.

To qualitatively and quantitatively compare synthetic and conventional MRI sequences acquired on a 1.5-T system for patients with multiple sclerosis (MS). Prospective study that involved twenty-seven consecutive relapsing-remitting MS patients scanned on a 1.5-T MRI scanner. The MRI protocol included 2D transverse conventional spin-echo sequences: proton density-weighted (PD), T2-weighted, T2-FLAIR, and T1-weighted. Synthetic images were generated using 2D transverse QRAPMASTER and SyMRI software with the same voxel size, repetition, echo, and inversion times as the conventional sequences. Four raters performed a crosstab qualitative analysis that involved evaluating global image quality, contrast, flow artefacts, and confidence in lesion assessment introducing the concepts of predominance, agreement, and disagreement. A quantitative analysis was also performed and included evaluating the number of lesions (periventricular, juxtacortical, brainstem, and cerebellum) and the contrast-to-noise ratio between regions (CSF, white matter, grey matter, lesions). The global image quality assessment showed predominance for better scores for conventional sequences over synthetic sequences, whereas contrast, confidence in lesion assessment, and flow artefacts showed predominance for agreement between sequences. There was predominance for disagreement between all pairs of raters in most of the evaluated qualitative parameters. Synthetic PD and T2-FLAIR images showed higher contrast-to-noise ratios than the corresponding conventional images for most comparison between regions. There were no significant differences in the number of lesions detected for most of the study regions between conventional and synthetic images. Synthetic MRI can be potentially used as an alternative to conventional brain MRI sequences in the assessment of MS.

Spiral gradient echo versus cartesian turbo spin echo imaging for sagittal contrast-enhanced fat-suppressed T1 weighted spine MRI: an inter-individual comparison study.

To compare a novel 3D spiral gradient echo (GRE) sequence with a conventional 2D cartesian turbo spin echo (TSE) sequence for sagittal contrast-enhanced (CE) fat-suppressed (FS) T1 weighted (T1W) spine MRI. In this inter-individual comparison study, 128 patients prospectively underwent sagittal CE FS T1W spine MRI with either a 2D cartesian TSE ("TSE", 285 s, 64 patients) or a 3D spiral GRE sequence ("Spiral", 93 s, 64 patients). Between both groups, patients were matched in terms of anatomical region (cervical/thoracic/lumbar spine and sacrum). Three readers used 4-point Likert scales to assess images qualitatively in terms of overall image quality, presence of artifacts, spinal cord visualization, lesion conspicuity and quality of fat suppression. Spiral achieved a 67.4% scan time reduction compared to TSE. Interreader agreement was high (alpha=0.868-1). Overall image quality (4;[3,4] vs 3;[3,4], p<0.001 - p=0.002 for all readers), presence of artifacts (4;[3,4] vs 3;[3,4] p=0.027 - p=0.046 for all readers), spinal cord visualization (4;[4,4] vs 4;[3,4], p<0.001 for all readers), lesion conspicuity (4;[4,4] vs 4;[4,4], p=0.016 for all readers) and quality of fat suppression (4;[4,4] vs 4;[4,4], p=0.027 - p=0.033 for all readers), were all deemed significantly improved by all three readers on Spiral images as compared to TSE images. We demonstrate the feasibility of a novel 3D spiral GRE sequence for improved and rapid sagittal CE FS T1W spine MRI. A 3D spiral GRE sequence allows for improved sagittal CE FS T1W spine MRI at very short scan times.

Intraindividual Comparison between the Contrast-Enhanced Golden-Angle Radial Sparse Parallel Sequence and the Conventional Fat-Suppressed Contrast-Enhanced T1-Weighted Spin-Echo Sequence for Head and Neck MRI.

The golden-angle radial sparse parallel-volumetric interpolated breath-hold (GRASP-VIBE) sequence is a recently introduced imaging technique with high resolution. This study compared the image quality between conventional fat-suppressed T1-weighted TSE and GRASP-VIBE after gadolinium enhancement in the head and neck region. Data from 65 patients with clinical indications for head and neck MR imaging between September 2020 and January 2021 were retrospectively reviewed. Two radiologists assessed the overall image quality, overall artifacts, and image conspicuities in the oropharynx, hypopharynx, and cervical lymph nodes according to 5-point scores (best score: 5). Interobserver agreement was assessed using weighted κ statistics. The SNR and contrast-to-noise ratio were calculated and compared between the 2 sequences using a paired Wilcoxon signed rank test. The analysis included 52 patients (mean age, 60 [SD, 14 ] years; male, 71.2% [37/52]) who were mostly diagnosed with head and neck malignancies (94.3% [50/52]). κ statistics ranged from slight agreement in cervical lymph node conspicuity (κ = 0.18) to substantial agreement in oropharyngeal mucosal conspicuity (κ = 0.80) (κ range, 0.18-0.80). Moreover, GRASP-VIBE demonstrated significantly higher mean scores in overall image quality (4.68 [SD, 0.41] versus 3.66 [SD, 0.73]), artifacts (4.47 [SD, 0.48] versus 3.58 [SD, 0.71]), oropharyngeal mucosal conspicuity (4.85 [SD, 0.41] versus 4.11 [SD, 0.79]), hypopharyngeal mucosal conspicuity (4.84 [SD, 0.34] versus 3.58 [SD, 0.81]), and cervical lymph node conspicuity (4.79 [SD, 0.32] versus 4.08 [SD, 0.64]) than fat-suppressed T1-weighted TSE (all, P < .001). Furthermore, GRASP-VIBE demonstrated a higher SNR (22.8 [SD, 11.5] versus 11.3 [SD, 5.6], P < .001) and contrast-to-noise ratio (4.7 [SD, 5.4] versus 2.3 [SD, 2.7], P = .059) than fat-suppressed T1-weighted TSE. GRASP-VIBE provided better image quality with fewer artifacts than conventional fat-suppressed T1-weighted TSE for the head and neck regions.

Pediatric MR lung imaging with 3D ultrashort-TE in free breathing: Are we past the conventional T2 sequence?

Magnetic resonance imaging (MRI) of the lungs is challenging for several reasons, mainly due to the respiratory motion, low proton density, and rapid T2* decay. Recent MR sequences with ultrashort TE (UTE) coupled with respiratory compensation promise to overcome these obstacles. So far, there are very few studies on the relevance of these sequences in children. The aim of the study was to compare the diagnostic value of a respiratory-self-gated three-dimensional UTE sequence versus a conventional respiratory-triggered T2-weighted turbo spin echo (T2-TSE) sequence in a pediatric collective. Seventy-one patients between 0 and 18 years of age, who were scheduled for a thoracic MRI based on diverse clinical indications, were examined on a 3T MRI system. The UTE and T2-TSE sequences were evaluated by two readers regarding quality features and visualization of eight common pathology patterns. The image quality of both sequences was equally high, with UTE depicting pleural and central bronchi more clearly. In pathologies, UTE was superior to T2-TSE for so-called "MR-negative pathologies", significant for air trapping, and in tendency for bullae and cysts. In all remaining pathologies, T2-TSE proved to be at least equivalent to UTE. At present, UTE cannot serve as a universal replacement for conventional T2-TSE for all pathologies. It yields, however, a substantial benefit in the context of hyperinflation, emphysema, cysts, or pathologies of the bronchial system.

Comparison of metal artifact reduction techniques in magnetic resonance imaging of carbon-reinforced PEEK and titanium spinal implants.

Carbon-reinforced PEEK (C-FRP) implants are non-magnetic and have increasingly been used for the fixation of spinal instabilities. To compare the effect of different metal artifact reduction (MAR) techniques in magnetic resonance imaging (MRI) on titanium and C-FRP spinal implants. Rod-pedicle screw constructs were mounted on ovine cadaver spine specimens and instrumented with either eight titanium pedicle screws or pedicle screws made of C-FRP and marked with an ultrathin titanium shell. MR scans were performed of each configuration on a 3-T scanner. MR sequences included transaxial conventional T1-weighted turbo spin echo (TSE) sequences, T2-weighted TSE, and short-tau inversion recovery (STIR) sequences and two different MAR-techniques: high-bandwidth (HB) and view-angle-tilting (VAT) with slice encoding for metal artifact correction (SEMAC). Metal artifact degree was assessed by qualitative and quantitative measures. There was a much stronger effect on artifact reduction with using C-FRP implants compared to using specific MRI MAR-techniques (screw shank: P < 0.001; screw tulip: P < 0.001; rod: P < 0.001). VAT-SEMAC sequences were able to reduce screw-related signal loss artifacts in constructs with titanium screws to a certain degree. Constructs with C-FRP screws showed less artifact-related implant diameter amplification when compared to constructs with titanium screws (P < 0.001). Constructs with C-FRP screws are associated with significantly less artifacts compared to constructs with titanium screws including dedicated MAR techniques. Artifact-reducing sequences are able to reduce implant-related artifacts. This effect is stronger in constructs with titanium screws than in constructs with C-FRP screws.

Diffusion in Sephadex Gel Structures: Time Dependency Revealed by Multi-Sequence Acquisition over a Broad Diffusion Time Range.

It has been increasingly reported that in biological tissues diffusion-weighted MRI signal attenuation deviates from mono-exponential decay, especially at high b-values. A number of diffusion models have been proposed to characterize this non-Gaussian diffusion behavior. One of these models is the continuous-time random-walk (CTRW) model, which introduces two new parameters: a fractional order time derivative α and a fractional order spatial derivative β. These new parameters have been linked to intravoxel diffusion heterogeneities in time and space, respectively, and are believed to depend on diffusion times. Studies on this time dependency are limited, largely because the diffusion time cannot vary over a board range in a conventional spin-echo echo-planar imaging sequence due to the accompanying T2 decays. In this study, we investigated the time-dependency of the CTRW model in Sephadex gel phantoms across a broad diffusion time range by employing oscillating-gradient spin-echo, pulsed-gradient spin-echo, and pulsed-gradient stimulated echo sequences. We also performed Monte Carlo simulations to help understand our experimental results. It was observed that the diffusion process fell into the Gaussian regime at extremely short diffusion times whereas it exhibited a strong time dependency in the CTRW parameters at longer diffusion times.

Three-Dimensional Magnetic Resonance Fingerprinting in Neonates: Quantifying Regional Difference and Maturation in the Brain.

Magnetic resonance fingerprinting (MRF) allows the simultaneous measurement of multiple tissue properties in a single acquisition. Three-dimensional (3D) MRF with high spatial resolution can be used for neonatal brain imaging. The aim of this study is to apply 3D MRF to neonates and show regional differences and maturation in the brain. In this prospective study, 3D MRF using hybrid radial-interleaved acquisition was performed on phantoms and neonates from December 2019 to October 2020. For the reconstruction of 3D MRF, singular value decomposition was applied to reduce reconstruction time, and the iterative reconstruction technique was applied to improve image quality. The accuracies of T1 and T2 values derived from 3D MRF were evaluated in a phantom experiment. Regional T1 and T2 values were obtained from neonates' brain T1 and T2 maps derived from 3D MRF. Regional T1 and T2 values were compared, and their changes according to corrected gestational age were evaluated. The acquisition time for 3D MRF with a spatial resolution of 0.7 × 0.7 × 2 mm3 was less than 5 minutes. The phantom study showed high correlation between T1 and T2 values derived from 3D MRF and those from conventional spin echo sequences (T1, R2 = 0.998, P < 0.001; T2, R2 = 0.998, P < 0.001). Three-dimensional MRF was performed in 25 neonates (15 boys, 10 girls; median corrected gestational age, 263 days; interquartile range, 10 days). In neonates, T1 and T2 values differed in the frontal (median [interquartile range], 2785 [2684-2888] milliseconds and 189.8 [176.7-222.9] milliseconds), parietal (2849 [2741-2950] milliseconds and 191.6 [167.5-232.9] milliseconds), and occipital white matter (2621 [2513-2722] milliseconds and 162.9 [143.5-186.1] milliseconds), showing lower values in occipital white matter (P < 0.001). Regional T1 values showed a negative relationship with corrected gestational age (coefficient, -0.775 to -0.480; P < 0.05). Fast and high spatial resolution 3D MRF was applied to neonates. T1 and T2 maps derived from 3D MRF enabled the quantification of regional differences and maturation in the neonatal brain.

Qualitative and Quantitative Analysis of a Spiral Gradient Echo Sequence for Contrast-Enhanced Fat-Suppressed T1-Weighted Spine Magnetic Resonance Imaging.

Pulse sequences with non-Cartesian k-space sampling enable improved imaging in anatomical areas with high degrees of motion artifacts. We analyzed a novel spiral 3-dimensional (3D) gradient echo (GRE) magnetic resonance imaging (MRI) sequence ("spiral," 114.7 ± 11 seconds) and compared it with a radial 3D GRE ("vane," 216.7 ± 2 seconds) and a conventional Cartesian 2D turbo spin echo (TSE) sequence ("TSE," 266.7 ± 82 seconds) for contrast-enhanced fat-suppressed T1-weighted spine imaging. Forty consecutive patients referred for contrast-enhanced MRI were prospectively scanned with all 3 sequences. A qualitative analysis was performed by 3 readers using 4- or 5-point Likert scales to independently grade images in terms of overall image quality, occurrence of artifacts, lesion conspicuity, and conspicuity of nerve roots. The numbers of visible nerve roots per sequence and patient were counted in consensus. Coefficient of variation measurements were performed for the paravertebral musculature (CVPM) and the spinal cord (CVSC). Spiral (median [interquartile range], 5 [4-5]) exhibited improved overall image quality in comparison to TSE (3 [3-4]) and vane (4 [4-5]; both P < 0.001). Vane surpassed TSE in terms of overall image quality (P < 0.001). Spiral (4 [3.75-4]) and vane (3.5 [3-4]) presented with less artifacts than TSE (3 [2.75-3.25]; both P < 0.001). Spiral (4 [4-5]) outperformed vane (4 [3-5]; P = 0.01) and TSE (4 [3-4]; P = 0.04) in terms of lesion conspicuity. Conspicuity of nerve roots was superior on spiral (3 [3-4]) and vane (4 [3-4]) when compared with TSE (1.5 [1-2]; both P < 0.001). Readers discerned significantly more nerve roots on spiral (4 [2.75-8]) and vane (4 [3.75-7.25]) images when compared with TSE (2 [0-4]; both P < 0.001). Interreader agreement ranged from moderate (α = 0.639) to almost perfect (α = 0.967). CVPM and CVSC were significantly lower on spiral as compared with vane and TSE (P < 0.001, P = 0.04). Vane exhibited lower CVPM and CVSC than TSE (P < 0.001, P = 0.01). A novel spiral 3D GRE sequence improves contrast-enhanced fat-suppressed T1-weighted spinal imaging qualitatively and quantitatively in comparison with a conventional Cartesian 2D TSE sequence and to a lesser extent with a radial 3D GRE sequence at shorter scan times.

Clinical implementation of accelerated T2 mapping: Quantitative magnetic resonance imaging as a biomarker for annular tear and lumbar disc herniation

ObjectivesThis study evaluates GRAPPATINI, an accelerated T2 mapping sequence combining undersampling and model-based reconstruction to facilitate the clinical implementation of T2 mapping of the lumbar intervertebral disc.MethodsFifty-eight individuals (26 females, 32 males, age 23.3 ± 8.0 years) were prospectively examined at 3 T. This cohort study consisted of 19 patients, 20 rowers, and 19 volunteers. GRAPPATINI was conducted with the same parameters as a conventional 2D multi-echo spin-echo (MESE) sequence in 02:27 min instead of 13:18 min. Additional T2 maps were calculated after discarding the first echo (T2-WO1ST) and only using even echoes (T2-EVEN). Segmentation was done on the four most central slices. The resulting T2 values were compared for all four measurements.ResultsT2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1ST of the nucleus pulposus of normal discs differed significantly from those of bulging discs or herniated discs (all p < 0.001). For the posterior annular region, only T2-GRAPPATINI showed a significant difference (p = 0.011) between normal and herniated discs. There was a significant difference between T2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1ST of discs with and without an annular tear for the nucleus pulposus (all p < 0.001). The nucleus pulposus’ T2 at different degeneration states showed significant differences between all group comparisons of Pfirrmann grades for T2-GRAPPATINI (p = 0.000–0.018), T2-MESE (p = 0.000–0.015), T2-EVEN (p = 0.000–0.019), and T2-WO1ST (p = 0.000–0.015).ConclusionsGRAPPATINI facilitates the use of T2 values as quantitative imaging biomarkers to detect disc pathologies such as degeneration, lumbar disc herniation, and annular tears while simultaneously shortening the acquisition time from 13:18 to 2:27 min.Key Points• T2-GRAPPATINI, T2-MESE, T2-EVEN, and T2-WO1STof the nucleus pulposus of normal discs differed significantly from those of discs with bulging or herniation (all p < 0.001).• The investigated T2mapping techniques differed significantly in discs with and without annular tearing (all p < 0.001).• The nucleus pulposus’ T2showed significant differences between different stages of degeneration in all group comparisons for T2-GRAPPATINI(p = 0.000–0.018), T2-MESE(p = 0.000–0.015), T2-EVEN(p = 0.000–0.019), and T2-WO1ST(p = 0.000–0.015).

Outpacing movement \u2014 ultrafast volume coverage in neuropediatric magnetic resonance imaging

BackgroundConventional MRI sequences are often affected in neuropediatric imaging by unavoidable movements. Therefore, children younger than 6 years usually have to be examined under sedation/anesthesia. A new real-time MRI technique with automatic slice advancement allows for motion-robust T2-weighted volume coverage of the whole brain within a few seconds in adults.ObjectiveTo evaluate to which extent the new volume coverage method can be used to visualize cerebrospinal fluid and reduce the need for anesthesia in children.Materials and methodsWe assessed 30 children ages 6 years and younger with suspected or proven hydrocephalus, hygroma or macrocephalus using volume coverage sequences with 20 slices per second in three planes. If necessary, a parent was placed in the bore together with the child for calming and gentle immobilization. We compared visualization of cerebrospinal fluid spaces and course of the shunt catheter in volume coverage sequences vs. fast spin-echo sequences.ResultsThe clinical issue could be sufficiently assessed in all children with use of volume coverage sequences, whereas conventional fast spin-echo sequences performed moderately to poorly. Visualization of the tip of a shunt failed in 16% of volume coverage scans and 27% of turbo spin-echo scans. A subsequent examination under anesthesia was never necessary. None of the examinations had to be stopped prematurely.ConclusionThe motion-robust volume coverage sequences with T2-type contrast can be used to avoid sedation of children in the evaluation of cerebrospinal fluid spaces, even in the presence of vigorous motion. For other indications and contrasts, the technique must still be evaluated.

Accelerated metallic artifact reduction imaging using spectral bin modulation of multiacquisition variable-resonance image combination selective imaging

ObjectivesTo assess the clinical utility of a prototype sequence for metal artifact reduction, the multiacquisition variable–resonance image combination selective (MAVRIC-SL) at 3 T. This sequence allows a surgical prosthesis-dependent reduction in the number of spectral bins. We compared the prototype MAVRIC SL to the conventional two-dimensional fast spin-echo (FSE) sequences and MAVRIC SL images acquired with all spectral bins to those acquired with the optimized number of spectral bins. MethodsMAVRIC SL images were acquired in 25 image sets from August 2017 to April 2018. For each subject, the optimized number of spectral bins was determined using a short spectral calibration scan. The image sets obtained with magnetic resonance imaging that were used for the analysis consisted of MAVRIC-SL proton density (PD)-weighted or short inversion time inversion recovery (STIR) images acquired with all 24 spectral bins, the corresponding images with the optimized number of spectral bins, and the conventional two-dimensional FSE or STIR PD-weighted images. A musculoskeletal radiologist reviewed and scored the images using a five-point scale for artifact reduction around the prosthesis and visualization of the prosthesis and peri-prosthetic tissues. Quantitative evaluation of the peri-prosthetic tissues was also performed. The Wilcoxon rank-sum test was used to test for significance. ResultsThe MAVRIC SL images enabled a significantly improved reduction in metallic artifacts compared to the conventional two-dimensional FSE sequences. The optimized number of spectral bins ranged from 6 to 20, depending on the prosthesis susceptibility difference, size, and orientation to the B0 field. The scan times significantly decreased with a reduced number of spectral bins (354.0 ± 139.1 versus 283.0 ± 89.6 s; 20% reduced scan time; p < .05). Compared to the MAVRIC SL images acquired with all 24 bins, the artifact reduction and visualization of the prosthesis and peri-prosthetic tissues on the MAVRIC SL images acquired with calibrated bins were not significantly different. ConclusionsCompared to the MAVRIC SL images acquired with all 24 spectral bins, those acquired with an optimized number of spectral bins can reduce metallic artifacts with no significant image quality degradation while providing reduced scan time.

Focal nodular marrow hyperplasia: Imaging features of 53 cases.

To describe the characteristic imaging features of focal nodular marrow hyperplasia (FNMH). Retrospective review of all patients with a diagnosis of FNMH between January 2007 and September 2019. The study included 53 patients, 7 males and 46 females with a mean age of 58 years (range 12-95 years). All had MRI with conventional spin echo sequences showing a poorly defined round/oval lesion with mild T1W iso/hyperintensity compared to skeletal muscle, low T2W turbo spin echo (TSE) signal intensity (SI) compared to marrow fat and variable SI on STIR, but never associated with reactive marrow oedema. All 53 patients had follow-up MRI, with all lesions remaining stable or partially resolving. In-phase (IP) and out-of-phase (OP) chemical shift imaging (CSI) was obtained in 31 of these, with 28 (90.3%) showing >20% SI drop on the OP sequence, while 3 (9.7%) demonstrated <20% SI drop. CT was available in 26 cases, 17 (65.4%) showing mild medullary sclerosis. Single-photon emission computed tomography CT (SPECT-CT) was available in four cases and Flourodeoxyglucose positron emission tomography CT (FDG PET-CT) in 2, all showing increased uptake. Focal uptake was also seen in three of eight patients who had undergone whole body bone scintigraphy. Only one lesion was biopsied, confirming FNMH. The imaging appearances of FNMH have been described on various modalities, particularly MRI with emphasis on the role of IP and OP CSI typically demonstrating >20% SI reduction. FNMH should be recognised and treated as a 'do not touch' lesion which does not require biopsy or prolonged follow-up. We describe and clarify the imaging characteristics of FNMH on MRI, including CSI, CT and various nuclear medicine modalities. An imaging algorithm is suggested for allowing a non-invasive diagnosis.

To measure T1 of short T2 species using an inversion recovery prepared three-dimensional ultrashort echo time (3D IR-UTE) method: A phantom study

PurposeTo demonstrate the feasibility of a new method for measuring T1 of short T2 species based on an adiabatic inversion recovery-prepared three-dimensional ultrashort echo time Cones (3D IR-UTE-Cones) sequence. MethodsT1 values for short T2 species were quantified using 3D IR-UTE-Cones data acquired with different repetition times (TRs) and inversion times (TIs). An inversion efficiency factor Q was introduced into the fitting model to accurately calculate T1 values for short T2 species. Experiments were performed on twelve MnCl2 aqueous solution phantoms with a wide range of T1 values and T2* values on a 3 T clinical MR system to verify the efficacy of the proposed method. For comparison, a variable flip angle UTE (VFA-UTE) sequence, a variable TR UTE (VTR-UTE) sequence, and a conventional 2D IR fast spin echo (IR-FSE) sequence were also used to quantify T1 values of those phantoms. T1 values were compared between all performed sequences. ResultsThe proposed 3D IR-UTE-Cones method provided higher contrast images of short T2 phantoms and measured much shorter T1 values than the VFA-UTE, VTR-UTE and 2D IR-FSE methods. T1 values as short as 2.95 ms could be measured by the 3D IR-UTE-Cones sequence. The 3D IR-UTE-Cones methods with different TRs were applied to different ranges of T1 measurement, and the scan time was significantly decreased by using 5 TIs along the recovery curves to perform fitting with comparable accuracy. ConclusionThe 3D IR-UTE-Cones sequence could accurately measure short T1 values while providing high contrast images of short T2 species.

Age related T2-FSE-MRI basal ganglia and inter-nuclei changes in normal aging

To evaluate clinically easy to obtain parameters such as area and T2 MR signal intensity (SI) profiles from right and left caudate, putamen and thalamus nuclei and to describe age-related and inter-nuclei changes in both genders in healthy subjects, 71 healthy subjects (22–80 years old, 52 females) were evaluated with 1.5 T MRI conventional axial T2-Fast axial spin echo sequences obtaining SI and cross-sectional areas from caudate, putamen and thalamus nuclei using manually defined ROIs. Regression analysis were performed between age and MR parameters for inter-nuclei, gender and hemisphere side. Male basal ganglia show lower SI than those from females. Aging was differentially associated to a progressive lowering of basal nuclei SI in both genders. Male basal ganglia show SI changes following a positive quadratic function. Aging modifies differentially SI from all nuclei pair combination in both genders, showing mainly negative quadratic function. Age-related reduction of female caudate and a right lateralization for caudate nucleus SI in both genders were found. Healthy age-related nonlinear changes in SI from basal ganglia were defined for both genders. Basal ganglia show differential age-related changes. These results can be helpful to differentiate normal from abnormal aging changes.