3D FLASH Sequence Research Articles

Prospective motion correction for brain MRI using spherical navigators.

To demonstrate for the first time the feasibility of performing prospective motion correction using spherical navigators (SNAVs). SNAVs were interleaved in a 3D FLASH sequence with an additional short baseline scan (6.8 s) for fast rotation estimation. Assessment of SNAV-based prospective motion correction was performed in six volunteers. Participant motion was guided using randomly generated stepwise prompts as well as prompts derived from real motion cases. Experiments were performed on a 3 T MRI scanner using a 32-channel head coil. When optimized for real-time application, SNAV-based motion estimates were computed in 25.8 ± 1.3 ms. Phantom-based quantification of rotation and translation accuracy indicated mean absolute errors of 0.10 ± 0.09° and 0.25 ± 0.14 mm, respectively. Implementing SNAV-based motion estimates for prospective motion correction led to a clear improvement in image quality with minimal increase in scan time (<5%). Optimization of SNAV processing for real-time application enables prospective motion correction with low latency and minimal scan time requirements.

Super-Resolved Dynamic 3D Reconstruction of the Vocal Tract during Natural Speech.

MRI is the gold standard modality for speech imaging. However, it remains relatively slow, which complicates imaging of fast movements. Thus, an MRI of the vocal tract is often performed in 2D. While 3D MRI provides more information, the quality of such images is often insufficient. The goal of this study was to test the applicability of super-resolution algorithms for dynamic vocal tract MRI. In total, 25 sagittal slices of 8 mm with an in-plane resolution of 1.6 × 1.6 mm2 were acquired consecutively using a highly-undersampled radial 2D FLASH sequence. The volunteers were reading a text in French with two different protocols. The slices were aligned using the simultaneously recorded sound. The super-resolution strategy was used to reconstruct 1.6 × 1.6 × 1.6 mm3 isotropic volumes. The resulting images were less sharp than the native 2D images but demonstrated a higher signal-to-noise ratio. It was also shown that the super-resolution allows for eliminating inconsistencies leading to regular transitions between the slices. Additionally, it was demonstrated that using visual stimuli and shorter text fragments improves the inter-slice consistency and the super-resolved image sharpness. Therefore, with a correct speech task choice, the proposed method allows for the reconstruction of high-quality dynamic 3D volumes of the vocal tract during natural speech.

Exploring atherosclerosis imaging with contrast-enhanced MRI using PEGylated ultrasmall iron oxide nanoparticles.

Plaque rupture is a critical concern due to its potential for severe outcomes such as cerebral infarction and myocardial infarction, underscoring the urgency of noninvasive early diagnosis. Magnetic resonance imaging (MRI) has gained prominence in plaque imaging, leveraging its noninvasiveness, high spatial resolution, and lack of ionizing radiation. Ultrasmall iron oxides, when modified with polyethylene glycol, exhibit prolonged blood circulation and passive targeting toward plaque sites, rendering them conducive for MRI. In this study, we synthesized ultrasmall iron oxide nanoparticles of approximately 3nm via high-temperature thermal decomposition. Subsequent surface modification facilitated the creation of a dual-modality magnetic resonance/fluorescence probe. Upon intravenous administration of the probes, MRI assessment of atherosclerotic plaques and diagnostic evaluation were conducted. The application of Flash-3D sequence imaging revealed vascular constriction at lesion sites, accompanied by a gradual signal amplification postprobe injection. T1-weighted imaging of the carotid artery unveiled a progressive signal ratio increase between plaques and controls within 72h post-administration. Fluorescence imaging of isolated carotid arteries exhibited incremental lesion-to-control signal ratios. Additionally, T1 imaging of the aorta demonstrated an evolving signal enhancement over 48h. Therefore, the ultrasmall iron oxide nanoparticles hold immense promise for early and noninvasive diagnosis of plaques, providing an avenue for dynamic evaluation over an extended time frame.

Reproducibility of lung perfusion and ventilation derived using phase-resolved functional lung (PREFUL) MRI imaging

Abstract Background There is a growing demand for non-invasive imaging biomarkers of lung function, allowing more sensitive and timely decision making to achieve better patient outcomes. Recently developed Fourier decomposition MRI methods enable quantitative assessment of lung performance. Objectives To assess intra- and inter-observer agreement of lung perfusion and ventilation derived using the free-breathing, contrast agent-free, phase-resolved functional lung (PREFUL) imaging. Methods Fifty patients with acute ST-segment elevation myocardial infarction underwent CMR imaging using a 3 T MRI scanner (MAGNETOM Skyra). Coronal images were acquired during free breathing, covering the entire lung using a phase-resolved functional lung 2D FLASH sequence. The main scan parameters were: temporal resolution = 2.1 ms, number of measurements = 250. The lung perfusion and ventilation maps were generated (Figure 1). The analysis of the images was performed using prototype software (MR Lung Prototype version 2.0) by two independent observers. Analysis was repeated after four weeks to assess intra-observer agreement. Results PREFUL imaging and analysis were fast with a 35 second scan time and up to one minute post-processing time for a complete quantitative assessment. The lung perfusion and ventilation demonstrated excellent intra-observer (ICC 0.928 (0.870 to 0.959) and 0.994 (0.990 to 0.997) for mean perfusion and ventilation respectively) and inter-observer agreement (ICC 0.966 (0.940 to 0.981) and 0.992 (0.985 to 0.996) for mean perfusion and ventilation respectively). Bland-Altman plots demonstrate intra- and inter-observer reproducibility for lung perfusion and ventilation (Figure 2). Conclusion The lung perfusion and ventilation derived using phase-resolved functional lung (PREFUL) MRI imaging are highly reproducible. The Fourier decomposition method may allow fast quantitative evaluation of lung function. Funding Acknowledgement Type of funding sources: Public Institution(s). Main funding source(s): Hospital of Lithuanian University of Health Sciences

3D-MRI versus 3D-CT in the evaluation of glenoid deformity in glenohumeral arthritis using Dixon 3D FLASH sequence.

To compare MRI with 3D reconstructions and 3D-CT with respect to assessment of glenoid wear in osteoarthritic shoulders. 3D reconstructions were generated for CT and MR (utilizing the Dixon technique) imaging performed on 29 osteoarthritic shoulders. Two reviewers independently performed glenoid morphometric measurements and evaluated glenoid erosion. Mean differences between the two modalities were calculated. Inter-observer agreement was calculated using kappa coefficient. The combined mean absolute difference (bias) in glenoid version between 3D-CT and 3D-MRI was 2.7° ± 1.6° (range 0.15-7.85, P value = 0.7). The combined mean absolute difference in glenoid inclination between 3D-CT and 3D-MRI was 6.8° ± 4.1° (range 0.8°-15.75°, P value = 0.17). No significant inter-reader variation in glenoid version and inclination measurements on 3D-CT and 3D-MRI was found (P > 0.05). The inter-reader reliability for both CT and MRI was high for Walch grading of glenoid bone loss (κ = 1, κ = 0.81, respectively). 3D-MRI is comparable to 3D-CT with respect to axial glenoid bone loss, as measured by glenoid version. However, for coronal bone loss estimation, measured by glenoid inclination, 3D-CT remains the gold standard. Thus, 3D-MR can be used as an alternative for preoperative assessment of glenoid version in arthritic shoulders.

Development of an MRI-Guided Approach to Selective Internal Radiation Therapy Using Holmium-166 Microspheres.

Simple SummarySelective internal radiation therapy (SIRT) is a treatment for patients with liver cancer that involves the injection of radioactive microspheres into the liver artery. For a successful treatment, it is important that tumours are adequately covered with these microspheres; however, there is currently no method to assess this intraoperatively. As holmium microspheres are paramagnetic, MRI can be used to visualize the holmium deposition directly after administration, and possibly to adapt the treatment if necessary. In order to exploit this advantage and provide a personally optimized approach to SIRT, the administration could ideally be performed within a clinical MRI scanner. It is, however, unclear whether all materials (catheters, administration device) used during the procedure are safe for use in the MRI suite. Additionally, we explore the capability of MRI to visualize the microspheres in near real-time during injection, which would be a requirement for successful MRI-guided treatment. We further illustrate our findings with an initial patient case.Selective internal radiation therapy (SIRT) is a treatment modality for liver tumours during which radioactive microspheres are injected into the hepatic arterial tree. Holmium-166 (166Ho) microspheres used for SIRT can be visualized and quantified with MRI, potentially allowing for MRI guidance during SIRT. The purpose of this study was to investigate the MRI compatibility of two angiography catheters and a microcatheter typically used for SIRT, and to explore the detectability of 166Ho microspheres in a flow phantom using near real-time MRI. MR safety tests were performed at a 3 T MRI system according to American Society for Testing of Materials standard test methods. To assess the near real-time detectability of 166Ho microspheres, a flow phantom was placed in the MRI bore and perfused using a peristaltic pump, simulating the flow in the hepatic artery. Dynamic MR imaging was performed using a 2D FLASH sequence during injection of different concentrations of 166Ho microspheres. In the safety assessment, no significant heating (ΔTmax 0.7 °C) was found in any catheter, and no magnetic interaction was found in two out of three of the used catheters. Near real-time MRI visualization of 166Ho microsphere administration was feasible and depended on holmium concentration and vascular flow speed. Finally, we demonstrate preliminary imaging examples on the in vivo catheter visibility and near real-time imaging during 166Ho microsphere administration in an initial patient case treated with SIRT in a clinical 3 T MRI. These results support additional research to establish the feasibility and safety of this procedure in vivo and enable the further development of a personalized MRI-guided approach to SIRT.

Estimation of laminar BOLD activation profiles using deconvolution with a physiological point spread function

BackgroundThe specificity of gradient echo (GE)-BOLD laminar fMRI activation profiles is degraded by intracortical veins that drain blood from lower to upper cortical layers, propagating activation signal in the same direction. This work describes an approach to obtain layer specific profiles by deconvolving the measured profiles with a physiological Point Spread Function (PSF). New methodIt is shown that the PSF can be characterised by a TE-dependent peak to tail (p2t) value that is independent of cortical depth and can be estimated by simulation. An experimental estimation of individual p2t values and the sensitivity of the deconvolved profiles to variations in p2t is obtained using laminar data measured with a multi-echo 3D-FLASH sequence. These profiles are echo time dependent, but the underlying neuronal response is the same, allowing a data-based estimation of the PSF. ResultsThe deconvolved profiles are highly similar to the gold-standard obtained from extremely high resolution 3D-EPI data, for a range of p2t values of 5–9, which covers both the empirically determined value (6.8) and the value obtained by simulation (6.3). -Comparison with Existing Method(s) Corrected profiles show a flatter shape across the cortex and a high level of similarity with the gold-standard, defined as a subset of profiles that are unaffected by intracortical veins. ConclusionsWe conclude that deconvolution is a robust approach for removing the effect of signal propagation through intracortical veins. This makes it possible to obtain profiles with high laminar specificity while benefitting from the higher efficiency of GE-BOLD sequences.

3D fast low-angle shot (FLASH) technique for 3T contrast-enhanced brain MRI in the inpatient and emergency setting: comparison with 3D magnetization-prepared rapid gradient echo (MPRAGE) technique.

To retrospectively evaluate the diagnostic performance of a 1-min contrast-enhanced 3D-FLASH pulse sequence for detecting intracranial enhancing lesions compared to standard contrast-enhanced 3D-MPRAGE pulse sequence. Contrast-enhanced 3D-FLASH (acquisition time 49s) and contrast-enhanced 3D-MPRAGE (4min 35s) pulse sequences were performed consecutively in 110 inpatient/emergency department 3T MRI brain examinations and analyzed by two independent neuroradiologist readers. For each sequence, the readers recorded (1) number of enhancing intracranial lesions; (2) intracranial susceptibility artifact (presence or absence; mm depth of intracranial signal loss); and (3) motion artifact (none, mild, moderate, severe). Inter and intra-reader agreement and reader accuracy relative to a reference standard were determined, and sequence comparison with respect to susceptibility and motion artifacts was performed. There was substantial intra-reader, inter-sequence agreement [reader 1, κ = 0.70 (95% CI: [0.60, 0.81]); reader 2, κ = 0.70 (95% CI: [0.59, 0.82])] and substantial intra-sequence, inter-reader agreement [3D-MPRAGE assessment, κ = 0.76 (95% CI: [0.66, 0.86]); 3D-FLASH assessment, κ = 0.86 (95% CI: [0.77, 0.94]) for detection of intracranial enhancing lesions. For both readers, the diagnostic accuracy of 3D-FLASH and 3D-MPRAGE was similar (3D-MPRAGE: 86.4 and 88.1%; 3D-FLASH: 88.2 and 84.5%), with no inter-sequence diagnostic accuracy discordancy between the sequences for either reader. 3D-FLASH was associated with less susceptibility artifact (p < 0.001 both readers) and less motion artifact (p < 0.001 both readers). On 3T brain MRI in the inpatient and emergency department setting, 1-min 3D-FLASH pulse sequence achieved comparable diagnostic performance to 4.5min 3D-MPRAGE pulse sequence for detecting enhancing intracranial lesions, with reduced susceptibility and motion artifacts.

An MRI Investigating of the Lower Limb Musculature in Patients with Chronic Inflammatory Demyelinating Polyneuropathy

IntroductionChronic inflammatory demyelinating polyneuropathy (CIDP) is an autoimmune disease characterized by peripheral nerve demyelination. Patients present with sensory and motor deficits, including symmetrical diffused muscle weakness especially in distal muscles. Studies have focused mainly on the neuropathic aspects of CIDP and its involvement in paresis, showing lesions in various nerve plexes including the lumbar nerve roots. Weakness in patients with CIDP has been reported predominantly in the distal musculature. However, changes in muscle quality and quantity have not been explored systematically throughout the lower limb. Thus, the purpose of this study was to use magnetic resonance imaging (MRI) to compare anatomical differences in the quadriceps femoris and triceps surae muscle complexes in a group of patients with CIDP and control subjects.MethodsTo date, five patients with CIDP (3 males, 2 females) and six healthy controls (4 males, 2 females) and matched on age (45 to 68 years) have been investigated. On separate days, MRI (T1) of the lower limb musculature was acquired via serial axial plane scans in a 3.0‐Tesla magnet with a 3D FLASH sequence: (0.9mm slice thickness with slice separation of 1mm ranging from 280 to 400 slices). All MRI scans were analyzed using OsiriX imaging processing software. On a single thigh slice (two‐thirds distance proximal to distal) and leg slice (one‐third distance proximal to distal) total muscle area was computed for the quadriceps femoris (rectus femoris, vastus lateralis, vastus intermedius, vastus medialis), and the triceps surae (soleus, lateral and medial gastrocnemii) groups, respectively. Contractile muscle area (fat and connective tissue removed) for each muscle group was determined using a pixel threshold intensity algorithm. Percentage of fat infiltration was computed by subtracting contractile muscle area from total muscle area.ResultsPatients with CIDP had ~24% less total anatomical cross‐sectional area (ACSA) in both quadriceps femoris and the triceps surae compared to controls. Patients with CIDP, however had ~35% less contractile muscle tissue in the quadriceps femoris whereas the triceps surae were ~51% lower in contractile tissue, compared with controls. The ACSA of the triceps surae of CIDP patients consisted of ~40% fat whereas the quadriceps femoris ACSA had ~16% fat infiltration. Furthermore, the control group's ACSA consisted of ~9% and 5% fat, respectively in the triceps surae and quadriceps.ConclusionPatients with CIDP have less total thigh ACSA with increased intramuscular fat infiltration compared with controls indicative of lower muscle quality in CIDP. Fatty infiltration in the CIDP group are greater in the anterior thigh compared to posterior leg. This indicates that in addition to lower muscle quantity and quality in CIDP, distal musculature seems to be affected to a greater degree by the nerve impairments noted in CIDP.Support or Funding InformationSupported by NSERCThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

3D-MRI versus 3D-CT in the evaluation of osseous anatomy in femoroacetabular impingement using Dixon 3D FLASH sequence.

To determine if hip 3D-MR imaging can be used to accurately demonstrate femoral and acetabular morphology in the evaluation of patients with femoroacetabular impingement. We performed a retrospective review at our institution of 17 consecutive patients (19 hips) with suspected femoroacetabular impingement who had both 3D-CT and 3D-MRI performed of the same hip. Two fellowship-trained musculoskeletal radiologists reviewed the imaging for the presence and location of cam deformity, anterior-inferior iliac spine variant, lateral center-edge angle, and neck-shaft angle. Findings on 3D-CT were considered the reference standard. The amount of radiation that was spared following introduction of 3D-MRI was also assessed. All 17 patients suspected of FAI had evidence for cam deformity on 3D-CT. There was 100% agreement for diagnosis (19 out of 19) and location (19 out of 19) of cam deformity when comparing 3D-MRI with 3D-CT. There were 3 type I and 16 type II anterior-inferior iliac spine variants on 3D-CT imaging with 89.5% (17 out of 19) agreement for the anterior-inferior iliac spine characterization between 3D-MRI and 3D-CT. There was 64.7% agreement when comparing the neck-shaft angle (11 out of 17) and LCEA (11 out of 17) measurements. The use of 3D-MRI spared each patient an average radiation effective dose of 3.09 mSV for a total reduction of 479 mSV over a 4-year period. 3D-MR imaging can be used to accurately diagnose and quantify the typical osseous pathological condition in femoroacetabular impingement and has the potential to eliminate the need for 3D-CT imaging and its associated radiation exposure, and the cost for this predominantly young group of patients.

Head motion measurement and correction using FID navigators.

To develop a novel framework for rapid, intrinsic head motion measurement in MRI using FID navigators (FIDnavs) from a multichannel head coil array. FIDnavs encode substantial rigid-body motion information; however, current implementations require patient-specific training with external tracking data to extract quantitative positional changes. In this work, a forward model of FIDnav signals was calibrated using simulated movement of a reference image within a model of the spatial coil sensitivities. A FIDnav module was inserted into a nonselective 3D FLASH sequence, and rigid-body motion parameters were retrospectively estimated every readout time using nonlinear optimization to solve the inverse problem posed by the measured FIDnavs. This approach was tested in simulated data and in 7 volunteers, scanned at 3T with a 32-channel head coil array, performing a series of directed motion paradigms. FIDnav motion estimates achieved mean absolute errors of 0.34 ± 0.49 mm and 0.52 ± 0.61° across all subjects and scans, relative to ground-truth motion measurements provided by an electromagnetic tracking system. Retrospective correction with FIDnav motion estimates resulted in substantial improvements in quantitative image quality metrics across all scans with intentional head motion. Quantitative rigid-body motion information can be effectively estimated using the proposed FIDnav-based approach, which represents a practical method for retrospective motion compensation in less cooperative patient populations.

Optimization of ZD2 Peptide Targeted Gd(HP-DO3A) for Detection and Risk-Stratification of Prostate Cancer with MRI.

The aim of this work is to optimize a peptide targeted macrocyclic MRI contrast agent for detection and risk-stratification of aggressive prostate cancer. The optimized agent was prepared using click chemistry in the presence of CuSO4 and ascorbate at room temperature. The T1 and T2 relaxivities of ZD2-N3-Gd(HP-DO3A) are 5.44 and 7.10 mM-1 s-1 at 1.4 T, and 5.53 and 7.81 mM-1 s-1 at 7 T, respectively, higher than the previously reported ZD2-Gd(HP-DO3A). The specific tumor enhancement of the agent was investigated in male nude mice bearing aggressive PC3 human prostate cancer xenografts and slow-growing LNCaP tumor xenografts. Contrast enhanced MR images were acquired using a 2D spin-echo sequence and a 3D FLASH sequence with a 7 T small animal scanner. ZD2-N3-Gd(HP-DO3A) produced robust contrast enhancement in aggressive PC3 tumors and little enhancement in slow-growing LNCaP tumors. It produced 400% and 100% CNR increases in the T1-weighted 2D spin-echo MR images and 3D FLASH images of PC3 tumors, respectively, for at least 30 min at a dose of 0.1 mmol/kg. In contrast, less than 20% CNR increase was observed in the LNCaP tumors with both sequences. The optimized targeted contrast agent has higher relaxivities and are effective to detect aggressive PC3 tumors and differentiate the aggressive cancer from the slow-growing LNCaP prostate cancer in contrast enhanced MRI. ZD2-N3-Gd(HP-DO3A) has the promise for accurate detection and risk-stratification of aggressive prostate cancer.

Gd-EOB-DTPA-enhanced MRI for quantitative assessment of liver organ damage after partial hepatic ischaemia reperfusion injury: correlation with histology and serum biomarkers of liver cell injury.

To evaluate Gd-EOB-DTPA-enhanced MRI for quantitative assessment of liver organ damage after hepatic ischaemia reperfusion injury (IRI) in mice. Partial hepatic IRI was induced in C57Bl/6 mice (n = 31) for 35, 45, 60 and 90 min. Gd-EOB-DTPA-enhanced MRI was performed 1 day after surgery using a 3D-FLASH sequence. A subgroup of n = 9 animals with 60 min IRI underwent follow-up with MRI and histology 7 days after IRI. The total liver volume was determined by manual segmentation of the entire liver. The volume of functional, contrast-enhanced liver parenchyma was quantified by a region growing algorithm (visual threshold) and an automated segmentation (Otsu's method). The percentages of functional, contrast-enhanced and damaged non-enhanced parenchyma were calculated according to these volumes. MRI data was correlated with serum liver enzyme concentrations and histologically quantified organ damage using periodic acid-Schiff (PAS) staining. The percentage of functional (contrasted) liver parenchyma decreased significantly with increasing ischaemia times (control, 94.4 ± 3.3%; 35 min IRI, 89.3 ± 4.1%; 45 min IRI, 87.9 ± 3.3%; 60 min IRI, 68 ± 10.5%, p < 0.001 vs. control; 90 min IRI, 55.9 ± 11.5%, p < 0.001 vs. control). The percentage of non-contrasted liver parenchyma correlated with histologically quantified liver organ damage (r = 0.637, p < 0.01) and serum liver enzyme elevations (AST r = 0.577, p < 0.01; ALT r = 0.536, p < 0.05). Follow-up MRI visualized recovery of functional liver parenchyma (71.5 ± 8.7% vs. 84 ± 2.1%, p < 0.05), consistent with less histological organ damage on day 7. We demonstrated the feasibility of Gd-EOB-DTPA-enhanced MRI for non-invasive quantification of damaged liver parenchyma following IRI in mice. This novel methodology may refine the characterization of liver disease and could have application in future studies targeting liver organ damage. • Prolonged ischaemia times in partial liver IRI increase liver organ damage. • Gd-EOB-DTPA-enhanced MRI at hepatobiliary phase identifies damaged liver volume after hepatic IRI. • Damaged liver parenchyma quantified with MRI correlates with histological liver damage. • Hepatobiliary phase Gd-EOB-DTPA-enhanced MRI enables non-invasive assessment of recovery from liver injury.

Acceleration techniques and their impact on arterial input function sampling: Non-accelerated versus view-sharing and compressed sensing sequences

PurposeThe aim was to investigate the variation of the arterial input function (AIF) within and between various DCE MRI sequences. Material and methodsA dynamic flow-phantom and steady signal reference were scanned on a 3T MRI using fast low angle shot (FLASH) 2d, FLASH3d (parallel imaging factor (P) = P0, P2, P4), volumetric interpolated breath-hold examination (VIBE) (P = P0, P3, P2 × 2, P2 × 3, P3 × 2), golden-angle radial sparse parallel imaging (GRASP), and time-resolved imaging with stochastic trajectories (TWIST). Signal over time curves were normalized and quantitatively analyzed by full width half maximum (FWHM) measurements to assess variation within and between sequences. ResultsThe coefficient of variation (CV) for the steady signal reference ranged from 0.07-0.8%. The non-accelerated gradient echo FLASH2d, FLASH3d, and VIBE sequences showed low within sequence variation with 2.1%, 1.0%, and 1.6%. The maximum FWHM CV was 3.2% for parallel imaging acceleration (VIBE P2 × 3), 2.7% for GRASP and 9.1% for TWIST. The FWHM CV between sequences ranged from 8.5–14.4% for most non-accelerated/accelerated gradient echo sequences except 6.2% for FLASH3d P0 and 0.3% for FLASH3d P2; GRASP FWHM CV was 9.9% versus 28% for TWIST. ConclusionMRI acceleration techniques vary in reproducibility and quantification of the AIF. Incomplete coverage of the k-space with TWIST as a representative of view-sharing techniques showed the highest variation within sequences and might be less suited for reproducible quantification of the AIF

Investigating the Triceps Surae in Chronic Inflammatory Demyelinating Polyneuropathy Patients using Magnetic Resonance Imaging

IntroductionChronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired autoimmune disease, primarily characterized by peripheral nerve demyelination. Patients present with sensory and motor deficits, including but not limited to symmetrical diffused muscle weakness. Studies to date have mainly focused on the neuropathic aspects of CIDP and its involvement in paresis. Impairments in skeletal muscle quality and quantity may be a consequence of motor nerve deficits, but these aspects have not been investigated comprehensively. Thus, the purpose of this study was to use magnetic resonance imaging (MRI) to explore anatomical and functional differences in the triceps surae muscle complex in a group with CIDP with a healthy control group.MethodsTo date, five patients with CIDP and six healthy control subjects were matched on anthropomorphic characteristics. Both groups underwent isometric plantar flexion strength measurements on a custom dynamometer. On separate days, MRI (T1 and T2) of the leg musculature was acquired via serial axial plane scans in a 3.0‐Tesla magnet. All MRI scans were analyzed using OsiriX imaging processing software. Total muscle volume was computed using the T1 weighted anatomical images with a 3D FLASH sequence: (0.9mm slice thickness with slice separation of 1mm ranging from 280 to 400 slices). T2 weighted relaxation times were determined from images with a spin‐echo sequence (5.0mm slice thickness; 16 echoes between 13.2–211.2ms). Both total volume (T1) and relaxation times (T2) were calculated separately for the three components of the triceps surae: soleus, medial gastrocnemius (MG), and lateral gastrocnemius (LG).ResultsCIDP patients had ~34% less plantar flexion strength compared with controls. CIDP patients had ~14%, ~28% and ~38% smaller muscle total volumes in the soleus, MG and LG, respectively, compared to controls. When strength was normalized to total triceps surae volume it was ~26% lower in CIDP. T2 relaxation times were significantly longer in CIDP with the soleus, MG and LG showing ~37%, ~31% and ~29% longer relaxation times, respectively.ConclusionCIDP patients were significantly weaker compared to control subjects. When strength was normalized to total triceps surae volume the difference remained indicating CIDP patients have lower intrinsic muscle contractile quality. This is further reinforced by the significantly longer T2 relaxation times, which likely reflects an increase in intramuscular fat infiltration in the CIDP group. The results indicate that muscle quantity and quality are affected by alterations in axonal function due to CIDP.Support or Funding InformationSupported by NSERCThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Preoperative evaluation of neurovascular relationship in trigeminal neuralgia by three-dimensional fast low angle shot (3D-FLASH) and three-dimensional constructive interference in steady-state (3D-CISS) MRI sequence.

The purpose of the study was to evaluate the value of high-resolution three-dimensional fast low angle shot (3D-FLASH) and three-dimensional constructive interference in steady-state (3D-CISS) MRI sequence solely or the combination of both in the visualization of neurovascular relationship in patients with trigeminal neuralgia (TN). 65 patients with unilateral TN underwent 3D-FLASH and 3D-CISS imaging were retrospectively studied. Neurovascular relationship at the intracisternal segment of trigeminal nerve was reviewed by two experienced neuroradiologist, who was blinded to the clinical details. The imaging results were compared with the operative findings in all patients. The accuracy and positive rates of the 3D-FLASH + CISS imaging (98.46, 92.31%) in judging the symptomatic side according to the presence of vascular contacts were higher than those of 3D-CISS (90.77%, 84.62) or 3D-FLASH (89.23, 83.08%) sequence. In addition, the statistical analysis showed the sensitivity and accuracy of 3D-FLASH + CISS imaging was higher than that of 3D-FLASH (p < 0.05). The 3D-FLASH + CISS imaging was more accurate in determining the type of offending vessel than 3D-CISS or 3D-FLASH imaging. The retrospective study demonstrates that the combination of 3D-FLASH with 3D-CISS sequence well delineates the relationship between intracisternal segment of trigeminal nerve and adjacent vessels in terms of increased positive rates and accuracy. Advances in knowledge: The study firstly dealt with the combination of 3D-CISS and 3D-FLASH imaging in TN.

Accuracy of fully automated, quantitative, volumetric measurement of the amount of fibroglandular breast tissue using MRI: correlation with anthropomorphic breast phantoms.

To demonstrate the accuracy of fully automated, quantitative, volumetric measurement of the amount of fibroglandular breast tissue (FGT), using MRI, and to investigate the impact of different MRI sequences using anthropomorphic breast phantoms as the ground truth. In this study, 10 anthropomorphic breast phantoms that consisted of different known fractions of adipose and protein tissue, which closely resembled normal breast parenchyma, were developed. Anthropomorphic breast phantoms were imaged with a 1.5T unit (Siemens, Avantofit) using an 18-channel breast coil. The sequence protocol consisted of an isotropic Dixon sequence (Di), an anisotropic Dixon sequence (Da), and T1 3D FLASH sequences with and without fat saturation (T1). Fully automated, quantitative, volumetric measurement of FGT for all anthropomorphic phantoms and sequences was performed and correlated with the amounts of fatty and protein components in the phantoms as the ground truth. Fully automated, quantitative, volumetric measurements of FGT with MRI for all sequences ranged from 5.86 to 61.05% (mean 33.36%). The isotropic Dixon sequence yielded the highest accuracy (median 0.51%-0.78%) and precision (median range 0.19%) compared with anisotropic Dixon (median 1.92%-2.09%; median range 0.55%) and T1 -weighted sequences (median 2.54%-2.46%; median range 0.82%). All sequences yielded good correlation with the FGT content of the anthropomorphic phantoms. The best correlation of FGT measurements was identified for Dixon sequences (Di, R2 =0.999; Da, R2 =0.998) compared with conventional T1 -weighted sequences (R2 =0.971). MRI yields accurate, fully automated, quantitative, volumetric measurements of FGT, an increasingly important and sensitive imaging biomarker for breast cancer risk. Compared with conventional T1 sequences, Dixon-type sequences show the highest correlation and reproducibility for automated, quantitative, volumetric FGT measurements using anthropomorphic breast phantoms as the ground truth.

Improving structural brain images acquired with the 3D FLASH sequence

The three-dimension Fast Low Angle SHot Magnetic Resonance Imaging (3D FLASH) sequence has been widely adopted in medical diagnostic imaging because of its availability, simplicity, and high spatial resolution. To improve the quality of structural brain images acquired with the 3D FLASH sequence, we developed a parameter optimization scheme and image inhomogeneity correction methods. The optimal imaging parameters were determined by maximizing gray-matter and white-matter CNR efficiency. Compared to protocols based on published parameters, applying the proposed optimal imaging parameters increased CNR efficiency by >10%. Image inhomogeneity, including signal and CNR inhomogeneity, was corrected by the choice of an optimal flip angle, estimated transmit function, and estimated receive sensitivity. As a result, our optimization and image inhomogeneity correction greatly improved the quality of images acquired with the 3D FLASH sequence.

Time-Dependent Changes in T1 during Fracture Healing in Juvenile Rats: A Quantitative MR Approach.

Quantitative magnetic resonance imaging (qMRI) offers several advantages in imaging and determination of soft tissue alterations when compared to qualitative imaging techniques. Although applications in brain and muscle tissues are well studied, its suitability to quantify relaxation times of intact and injured bone tissue, especially in children, is widely unknown. The objective observation of a fracture including its age determination can become of legal interest in cases of child abuse or maltreatment. Therefore, the aim of this study is the determination of time dependent changes in intact and corresponding injured bones in immature rats via qMRI, to provide the basis for an objective and radiation-free approach for fracture dating. Thirty-five MR scans of 7 Sprague-Dawley rats (male, 4 weeks old, 100 ± 5 g) were acquired on a 3T MRI scanner (TimTrio, Siemens AG, Erlangen, Germany) after the surgical infliction of an epiphyseal fracture in the tibia. The images were taken at days 1, 3, 7, 14, 28, 42 and 82 post-surgery. A proton density-weighted and a T1-weighted 3D FLASH sequence were acquired to calculate the longitudinal relaxation time T1 of the fractured region and the surrounding tissues. The calculation of T1 in intact and injured bone resulted in a quantitative observation of bone development in intact juvenile tibiae as well as the bone healing process in the injured tibiae. In both areas, T1 decreased over time. To evaluate the differences in T1 behaviour between the intact and injured bone, the relative T1 values (bone-fracture) were calculated, showing clear detectable alterations of T1 after fracture occurrence. These results indicate that qMRI has a high potential not only for clinically relevant applications to detect growth defects or developmental alterations in juvenile bones, but also for forensically relevant applications such as the dating of fractures in cases of child abuse or maltreatment.

Reduced respiratory motion artifacts using structural similarity in fast 2D dynamic contrast enhanced MRI of liver lesions.

The purpose of this work was to improve dynamic contrast enhanced MRI (DCE-MRI) of liver lesions by removing motion corrupted images as identified by a structural similarity (SSIM) algorithm, and to assess the effect of this correction on the pharmacokinetic parameter Ktrans using automatically determined arterial input functions (AIFs). Fifteen patients with colorectal liver metastases were measured twice with a T1 weighted multislice 2D FLASH sequence for DCE-MRI (time resolution 1.2s). AIFs were automatically derived from contrast inflow in the aorta of each patient. Thereafter, SSIM identified motion corrupted images of the liver were removed from the DCE dataset. From this corrected data set Ktrans and its reproducibility were determined. Using the SSIM algorithm a median fraction of 46% (range 37-50%) of the liver images in DCE time series was labeled as motion distorted. Rejection of these images resulted in a significantly lower median Ktrans (p<0.05) and lower coefficient of repeatability of Ktrans in liver metastases compared with an analysis without correction. SSIM correction improves the reproducibility of the DCE-MRI parameter Ktrans in liver metastasis and reduces contamination of Ktrans values of lesions by that of surrounding normal liver tissue.