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Purpose: To develop a 3D phase modulated UTE adiabatic T1ρ (PM‐UTE‐AdiabT1ρ) sequence for whole knee joint mapping on a clinical 3 T scanner. Methods: This new sequence includes six major features: (1) a magnetization reset module, (2) a train of adiabatic full passage pulses for spin locking, (3) a phase modulation scheme (i.e., RF cycling pair), (4) a fat saturation module, (5) a variable flip angle scheme, and (6) a 3D UTE Cones sequence for data acquisition. A simple exponential fitting was used for T1ρ quantification. Phantom studies were performed to investigate PM‐UTE‐AdiabT1ρ's sensitivity to compositional changes and reproducibility as well as its correlation with continuous wave–T1ρ measurement. The PM‐UTE‐AdiabT1ρ technique was then applied to five ex vivo and five in vivo normal knees to measure T1ρ values of femoral cartilage, meniscus, posterior cruciate ligament, anterior cruciate ligament, patellar tendon, and muscle. Results: The phantom study demonstrated PM‐UTE‐AdiabT1ρ's high sensitivity to compositional changes, its high reproducibility, and its strong linear correlation with continuous wave–T1ρ measurement. The ex vivo and in vivo knee studies demonstrated average T1ρ values of 105.6 ± 8.4 and 77.9 ± 3.9 ms for the femoral cartilage, 39.2 ± 5.1 and 30.1 ± 2.2 ms for the meniscus, 51.6 ± 5.3 and 29.2 ± 2.4 ms for the posterior cruciate ligament, 79.0 ± 9.3 and 52.0 ± 3.1 ms for the anterior cruciate ligament, 19.8 ± 4.5 and 17.0 ± 1.8 ms for the patellar tendon, and 91.1 ± 8.8 and 57.6 ± 2.8 ms for the muscle, respectively. Conclusion: The 3D PM‐UTE‐AdiabT1ρ sequence allows volumetric T1ρ assessment for both short and long T2 tissues in the knee joint on a clinical 3 T scanner. [ABSTRACT FROM AUTHOR]

Muscle degeneration following rotator cuff tendon tearing is characterized by fatty infiltration and fibrosis. While tools exist for the characterization of fat, the ability to noninvasively assess muscle fibrosis is limited. The purpose of this study was to evaluate the capability of quantitative ultrashort echo time T1 (UTE‐T1) and UTE magnetization transfer (UTE‐MT) mapping with and without fat suppression (FS) for the differentiation of injured and control rotator cuff muscles and for the detection of fibrosis. A rat model of chronic massive rotator cuff tearing (n = 12) was used with tenotomy of the right supraspinatus and infraspinatus tendons and silicone implants to prevent healing. Imaging was performed on a 3‐T scanner, and UTE‐T1 mapping with and without FS and UTE‐MT with and without FS for macromolecular fraction (MMF) mapping was performed. At 20 weeks postinjury, T1 and MMF were measured in the supraspinatus and infraspinatus muscles of the injured and contralateral, internal control sides. Histology was performed and connective tissue fraction (CTF) was measured, defined as the area of collagen‐rich extracellular matrix divided by the total muscle area. Paired t‐tests and correlation analyses were performed. Significant differences between injured and control sides were found for CTF in the supraspinatus (mean ± SD, 14.5% ± 3.9% vs. 11.3% ± 3.7%, p = 0.01) and infraspinatus (17.0% ± 5.4% vs. 12.5% ± 4.6%, p < 0.01) muscles, as well as for MMF using UTE‐MT FS in the supraspinatus (9.7% ± 0.3% vs. 9.5% ± 0.2%, p = 0.04) and infraspinatus (10.9% ± 0.8% vs. 10.1% ± 0.5%, p < 0.01) muscles. No significant differences between sides were evident for T1 without or with FS or for MMF using UTE‐MT. Only MMF using UTE‐MT FS was significantly correlated with CTF for both supraspinatus (r = 0.46, p = 0.03) and infraspinatus (r = 0.51, p = 0.01) muscles. Fibrosis occurs in rotator cuff muscle degeneration, and the UTE‐MT FS technique may be helpful to evaluate the fibrosis component, independent from the fatty infiltration process. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the use of ultrashort echo time (UTE) magnetic resonance imaging (MRI) techniques (T1 and magnetization transfer [MT] modeling) for imaging of the Achilles tendons and entheses in patients with psoriatic arthritis (PsA) compared with asymptomatic volunteers. The heels of twenty‐six PsA patients (age 59 ± 15 years, 41% female) and twenty‐seven asymptomatic volunteers (age 33 ± 11 years, 47% female) were scanned in the sagittal plane with UTE‐T1 and UTE‐MT modeling sequences on a 3‐T clinical scanner. UTE‐T1 and macromolecular proton fraction (MMF; the main outcome of MT modeling) were calculated in the tensile portions of the Achilles tendon and at the enthesis (close to the calcaneus bone). Mann–Whitney‐U tests were used to examine statistically significant differences between the two cohorts. UTE‐T1 in the entheses was significantly higher for the PsA group compared with the asymptomatic group (967 ± 145 vs. 872 ± 133 ms, p < 0.01). UTE‐T1 in the tendons was also significantly higher for the PsA group (950 ± 145 vs. 850 ± 138 ms, p < 0.01). MMF in the entheses was significantly lower in the PsA group compared with the asymptomatic group (15% ± 3% vs. 18% ± 3%, p < 0.01). MMF in the tendons was also significantly lower in the PsA group compared with the asymptomatic group (17% ± 4% vs. 20% ± 5%, p < 0.01). Percentage differences in MMF between the asymptomatic and PsA groups (−16.6% and −15.0% for the enthesis and tendon, respectively) were higher than the T1 differences (10.8% and 11.7% for the enthesis and tendon, respectively). The results suggest higher T1 and lower MMF in the Achilles tendons and entheses in PsA patients compared with the asymptomatic group. This study highlights the potential of UTE‐T1 and UTE‐MT modeling for quantitative evaluation of entheses and tendons in PsA patients. [ABSTRACT FROM AUTHOR]

The purpose of the current study was to investigate the effects of B0 and linear eddy currents on ultrashort echo time double echo steady state (UTE‐DESS) imaging and to determine whether eddy current correction (ECC) effectively resolves imaging artifacts caused by eddy currents. 3D UTE‐DESS sequences based on either projection radial or spiral cones trajectories were implemented on a 3‐T clinical MR scanner. An off‐isocentered thin‐slice excitation approach was used to measure eddy currents. The measurements were repeated four times using two sets of tested gradient waveforms with opposite polarities and two different slice locations to measure B0 and linear eddy currents simultaneously. Computer simulation was performed to investigate the eddy current effect. Finally, a phantom experiment, an ex vivo experiment with human synovium and ankle samples, and an in vivo experiment with human knee joints, were performed to demonstrate the effects of eddy currents and ECC in UTE‐DESS imaging. In a computer simulation, the two echoes (S+ and S‐) in UTE‐DESS imaging exhibited strong distortion at different orientations in the presence of B0 and linear eddy currents, resulting in both image degradation as well as misalignment of pixel location between the two echoes. The same phenomenon was observed in the phantom, ex vivo, and in vivo experiments, where the presence of eddy currents degraded S+, S‐, echo subtraction images, and T2 maps. The implementation of ECC dramatically improved both the image quality and image registration between the S+ and S‐ echoes. It was concluded that ECC is crucial for reliable morphological and quantitative UTE‐DESS imaging. [ABSTRACT FROM AUTHOR]

Osteoarthritis is a common chronic degenerative disease that causes pain and disability with increasing incidence worldwide. The osteochondral junction is a dynamic region of the joint that is associated with the early development and progression of osteoarthritis. Despite the substantial advances achieved in the imaging of cartilage and application to osteoarthritis in recent years, the osteochondral junction has received limited attention. This is primarily related to technical limitations encountered with conventional MR sequences that are relatively insensitive to short T2 tissues and the rapid signal decay that characterizes these tissues. MR sequences with ultrashort echo time (UTE) are of great interest because they can provide images of high resolution and contrast in this region. Here, we briefly review the anatomy and function of cartilage, focusing on the osteochondral junction. We also review basic concepts and recent applications of UTE MR sequences focusing on the osteochondral junction. [ABSTRACT FROM AUTHOR]

Conventional magnetic resonance imaging (MRI) often acquires no signal in anterior cruciate ligament (ACL) due to the short apparent transverse relaxation time of ACL. Ultrashort echo time (UTE) MRI is capable of imaging ACL with high signal which enables quantitative ACL assessment. This study aimed to investigate the correlations of the mechanical and microstructural properties of human ACL specimens with quantitative three‐dimensional UTE Cones (3D‐UTE‐Cones) MRI measures. ACL specimens were harvested from cadaveric knee joints of 13 (50.9 ± 21.1 years old, 11 males and 2 female) donors. Specimens were scanned using a series of quantitative 3D‐UTE‐Cones T2* (UTE‐T2*), T1 (UTE‐T1), Adiabatic T1ρ (UTE‐Adiab‐T1ρ), and magnetization transfer (UTE‐MT) sequences in a wrist coil on a clinical 3T scanner. ACL elastic modulus was measured using a uniaxial tensile mechanical test. Histomorphometry analysis was performed to measure the average fascicle specific surface, fascicle size, and number of cells per unit area. Spearman's rank correlations of UTE‐MRI biomarkers with mechanical and histomorphometry measures were investigated. The elastic modulus of ACL showed significant moderate correlations with UTE‐Adiab‐T1ρ (R = −0.59, p = 0.01), macromolecular fraction from MT modeling (R = 0.54, p = 0.01), magnetization transfer ratio (R = 0.53, p = 0.01), UTE‐T2* (R = −0.53, p = 0.01), and average fascicle specific surface (R = 0.54, p = 0.01). UTE‐MRI showed nonsignificant correlations with histomorphometry measures. UTE‐MRI biomarkers may be useful noninvasive tools for the ACL mechanical assessment. [ABSTRACT FROM AUTHOR]

This review article summarizes recent technical developments in ultrashort echo time (UTE) magnetic resonance imaging of musculoskeletal (MSK) tissues with short‐T2 relaxation times. A series of contrast mechanisms are discussed for high‐contrast morphological imaging of short‐T2 MSK tissues including the osteochondral junction, menisci, ligaments, tendons, and bone. Quantitative UTE mapping of T1, T2*, T1ρ, adiabatic T1ρ, magnetization transfer ratio, MT modeling of macromolecular proton fraction, quantitative susceptibility mapping, and water content is also introduced. Met and unmet needs in MSK imaging are discussed. Evidence Level: 1 Technical Efficacy: Stage 3 [ABSTRACT FROM AUTHOR]

The objective of the current study was to investigate the feasibility of quantitative 3D ultrashort echo time (UTE)‐based biomarkers in detecting proteoglycan (PG) loss and collagen degradation in human cartilage. A total of 104 cartilage samples were harvested for a trypsin digestion study (n = 44), and a sequential trypsin and collagenase digestion study (n = 60), respectively. Forty‐four cartilage samples were randomly divided into a trypsin digestion group (tryp group) and a control group (phosphate‐buffered saline [PBS] group) (n = 22 for each group) for the trypsin digestion experiment. The remaining 60 cartilage samples were divided equally into four groups (n = 15 for each group) for sequential trypsin and collagenase digestion, including PBS + Tris (incubated in PBS, then Tris buffer solution), PBS + 30 U col (incubated in PBS, then 30 U/ml collagenase [30 U col] with Tris buffer solution), tryp + 30 U col (incubated in trypsin solution, then 30 U/ml collagenase with Tris buffer solution), and tryp + Tris (incubated in trypsin solution, then Tris buffer solution). The 3D UTE‐based MRI biomarkers included T1, multiecho T2*, adiabatic T1ρ (AdiabT1ρ), magnetization transfer ratio (MTR), and modeling of macromolecular proton fraction (MMF). For each cartilage sample, UTE‐based biomarkers (T1, T2*, AdiabT1ρ, MTR, and MMF) and sample weight were evaluated before and after treatment. PG and hydroxyproline assays were performed. Differences between groups and correlations were assessed. All the evaluated biomarkers were able to differentiate between healthy and degenerated cartilage in the trypsin digestion experiment, but only T1 and AdiabT1ρ were significantly correlated with the PG concentration in the digestion solution (p = 0.004 and p = 0.0001, respectively). In the sequential digestion experiment, no significant differences were found for T1 and AdiabT1ρ values between the PBS + Tris and PBS + 30 U col groups (p = 0.627 and p = 0.877, respectively), but T1 and AdiabT1ρ values increased significantly in the tryp + Tris (p = 0.031 and p = 0.024, respectively) and tryp + 30 U col groups (both p < 0.0001). Significant decreases in MMF and MTR were found in the tryp + 30 U col group compared with the PBS + Tris group (p = 0.002 and p = 0.001, respectively). It was concluded that AdiabT1ρ and T1 have the potential for detecting PG loss, while MMF and MTR are promising for the detection of collagen degradation in articular cartilage, which could facilitate earlier, noninvasive diagnosis of osteoarthritis. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of fat saturation (FatSat) on quantitative UTE imaging of variable knee tissues on a 3T scanner. Methods: Three quantitative UTE imaging techniques, including the UTE multi‐echo sequence for T2∗ measurement, the adiabatic T1ρ prepared UTE sequence for T1ρ measurement, and the magnetization transfer (MT)‐prepared UTE sequence for MT ratio (MTR) and macromolecular proton fraction (MMF) measurements were used in this study. Twelve samples of cartilage and twelve samples of meniscus, as well as six whole knee cadaveric specimens, were imaged with the three above‐mentioned UTE sequences with and without FatSat. The difference, correlation, and agreement between the UTE measurements with and without FatSat were calculated to investigate the effects of FatSat on quantification. Results: Fat was well‐suppressed using all three UTE sequences when FatSat was deployed. For the small sample study, the quantification difference ratio (QDR) values of all the measured biomarkers ranged from 0.7% to 12.6%, whereas for the whole knee joint specimen study, the QDR values ranged from 0.2% to 12.0%. Except for T1ρ in muscle and MMF in meniscus (p > 0.05), most of the measurements showed statistical differences for T1ρ, MTR, and MMF (p < 0.05) between FatSat and non‐FatSat scans. Most of the measurements for T2∗ showed no significant differences (p > 0.05). Strong correlations were found for all the biomarkers between measurements with and without FatSat. Conclusion: The UTE biomarkers showed good correlation and agreement with some slight differences between the scans with and without FatSat. [ABSTRACT FROM AUTHOR]

Background: Concerns over gadolinium (Gd) retention encourage the use of lower Gd doses. However, lower Gd doses may compromise imaging performance. Higher relaxivity gadobenate may be suited to reduced dose protocols. Purpose: To compare 0.05 mmol/kg and 0.1 mmol/kg gadobenate in patients undergoing enhanced MRI of the central nervous system (CNS). Study Type: Retrospective, multicenter. Population: Three hundred and fifty‐two patients receiving 0.05 (n = 181) or 0.1 (n = 171) mmol/kg gadobenate. Field Strength/Sequences: 1.5 T and 3.0 T/precontrast and postcontrast T1‐weighted spin echo/fast spin echo (SE/FSE) and/or gradient echo/fast field echo (GRE/FFE); precontrast T2‐weighted FSE and T2‐FLAIR. Assessment: Images of patients with extra‐axial lesions at 1.5 T or any CNS lesion at 3.0 T were reviewed by three blinded, independent neuroradiologists for qualitative (lesion border delineation, internal morphology visualization, contrast enhancement; scores from 1 = poor to 4 = excellent) and quantitative (lesion‐to‐brain ratio [LBR], contrast‐to‐noise ratio [CNR]; SI measurements at regions‐of‐interest on lesion and normal parenchyma) enhancement measures. Noninferiority of 0.05 mmol/kg gadobenate was determined for each qualitative endpoint if the lower limit of the 95% confidence interval (CI) for the difference in precontrast + postcontrast means was above a noninferiority margin of −0.4. Statistical Tests: Student's t‐test for comparison of mean qualitative endpoint scores, Wilcoxon signed rank test for comparison of LBR and CNR values; Wilcoxon rank sum test for comparison of SI changes. Tests were significant for P < 0.05. Results: The mean change from precontrast to precontrast + postcontrast was significant for all endpoints. Readers 1, 2, and 3 evaluated 304, 225, and 249 lesions for 0.05 mmol/kg gadobenate, and 382, 309, and 298 lesions for 0.1 mmol/kg gadobenate. The lower limit of the 95% CI was above −0.4 for all comparisons. Significantly, higher LBR and CNR was observed with the higher dose. Data Conclusion: 0.05 mmol/kg gadobenate was noninferior to 0.1 mmol/kg gadobenate for lesion visualization. Evidence Level: 2 Technical Efficacy: Stage 3 [ABSTRACT FROM AUTHOR]

Introduction: Joint iron accumulation is the incendiary factor triggering osteochondral destruction, synovial hypertrophy, inflammation, and vascular remodelling in haemophilic arthropathy (HA). Hemosiderin depositions have been described in synovium and, more recently, in cartilage. Clinical observations also suggest hemosiderin accumulation in subchondral cysts, implying cyst bleeding. Aim: We explored associations between cystic iron accumulation, vascular remodelling and HA status to determine if cystic bleeding may contribute to HA progression. Methods: Thirty‐six haemophilic joints (16 knees, 10 ankles, and 10 elbows; 31 adult patients with haemophilia A/B) were evaluated by magnetic resonance imaging (MRI) for subchondral cysts and hemosiderin. Cyst score (WORMS) and hemosiderin presence were compared between haemophilic and osteoarthritic knees, matched for the degree of arthritis (Kellgren‐Lawrence score). Cystic iron accumulation, vascular remodelling and macrophage cell counts were also compared by immunohistochemistry in explanted joint tissues. In haemophilic knees, cyst number and extent of hemosiderin deposition were correlated with haemophilia joint health scores (HJHS). Results: Cystic hemosiderin was detected in 78% of haemophilic joints. Cyst score and presence of hemosiderin were significantly higher in haemophilic compared to osteoarthritic knees. Cyst score and presence of hemosiderin strongly correlated with HJHS. Moreover, iron deposition and vascular remodelling were significantly more pronounced within cysts in haemophilic compared to osteoarthritic knees, with similar total cell and macrophage count. Conclusion: These findings suggest the presence of subchondral bleeding in haemophilia, contributing to poor joint health outcomes. Observations of bleeding into osseous structures are novel and should inform investigations of new therapies. [ABSTRACT FROM AUTHOR]

Ultrashort echo time (UTE) sequences can image tissues with transverse T 2/T 2* relaxations too short to be efficiently observed on routine clinical MRI sequences, such as the vertebral body cartilaginous endplate (CEP). Here, we describe a 3D adiabatic inversion‐recovery‐prepared fat‐saturated ultrashort echo time (3D IR‐FS‐UTE) sequence to highlight the CEP of vertebral bodies in comparison to the intervertebral disc (IVD) and bone marrow fat (BF) at 3 T. The IR‐FS‐UTE sequence used a 3D UTE sequence combined with an adiabatic IR preparation pulse centered in the middle of the water and fat peaks, while a fat saturation module was used to suppress the signal from fat. A slab‐selective half pulse was used for signal excitation, and a 3D center‐out cones trajectory was used for more efficient data sampling. The 3D IR‐FS‐UTE sequence was applied to an ex vivo human spine sample, as well as the spines of six healthy volunteers and of three patients with back pain. Bright continuous lines representing signal from CEP were found in healthy IVDs. The measured contrast‐to‐noise ratio was 18.5 ± 4.9 between the CEP and BF, and 20.3 ± 4.15 between the CEP and IVD for the six volunteers. Abnormal IVDs showed CEP discontinuity or irregularity in the sample and patient studies. In conclusion, the proposed 3D IR‐FS‐UTE sequence is feasible for imaging the vertebral body's CEP in vivo with high contrast. [ABSTRACT FROM AUTHOR]

Background: Recent studies suggest that macromolecular fraction (MMF) derived from three-dimensional ultrashort echo time magnetization transfer (UTE-MT) imaging is insensitive to the magic angle effect. However, its clinical use in osteoarthritis (OA) remains to be investigated.Purpose: To investigate the feasibility of 3D UTE-MT-derived MMF in differentiating normal from degenerated cartilage.Study Type: Prospective.Subjects: Sixty-two participants (54.8 ± 16.7 years, 30 females) with and without OA, plus two healthy volunteers (mean age 35.0 years) for reproducibility test.Field Strength/sequence: 3 T/UTE-MT sequence.Assessment: A 3D UTE-MT sequence was employed to calculate MMF based on a two-pool model. Kellgren-Lawrence (KL) grade and Whole-Organ Magnetic Resonance Imaging Score (WORMS) were evaluated by three experienced musculoskeletal radiologists. KL grade was condensed into three groups: KL0, KL1-2, and KL3-4. WORMS was regrouped based on extent of lesion (extent group) and depth of lesion (depth group), respectively. The performance of MMF at evaluating the degeneration of cartilage was assessed via Spearman's correlation coefficient and the area under the curve (AUC) calculated according to the receiver-operating characteristic curve.Statistical Tests: After normality check, one-way analysis of variance was used to evaluate the performance. Tukey-Kramer test was performed for post hoc testing.Results: MMF showed significant negative correlations with KL grade (r = -0.53, P < 0.05) and WORMS (r = -0.49, P < 0.05). Significantly lower MMFs were found in subjects with greater KL grade (11.8 ± 0.8% for KL0; 10.9 ± 0.9% for KL1-2; 10.6 ± 1.1% for KL3-4; P < 0.05) and in cartilage with greater extent (12.1 ± 1.6% for normal cartilage; 10.9 ± 1.6% for regional lesions; 9.6 ± 1.7% for diffuse lesions; P < 0.05) and depth (12.1 ± 1.6% for normal cartilage; 10.6 ± 1.6% for partial-thickness lesions; 8.8 ± 1.7% for full-thickness lesions; P < 0.05) of lesions. AUC values of MMF for doubtful-minimal OA (KL1-2) and mild cartilage degradation (WORMS1-2) were 0.8 and 0.7, respectively.Data Conclusion: This study highlights the clinical potential of MMF in the detection of early OA.Level Of Evidence: 2 TECHNICAL EFFICACY STAGE: 2. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we aimed to develop a new technique, ultrashort echo time Cones double echo steady state (UTE‐Cones‐DESS), for highly efficient morphological imaging of musculoskeletal tissues with short T2s. We also proposed a novel, single‐point Dixon (spDixon)‐based approach for fat suppression. Methods: The UTE‐Cones‐DESS sequence was implemented on a 3T MR system. It uses a short radiofrequency (RF) pulse followed by a pair of balanced spiral‐out and spiral‐in readout gradients separated by an unbalanced spoiling gradient in‐between. The readout gradients are applied immediately before or after the RF pulses to achieve a UTE image (S+) and a spin/stimulated echo image (S−). Weighted echo subtraction between S+ and S− was performed to achieve high contrast specific to short T2 tissues, and spDixon was applied to suppress fat by using the intrinsic complex signal of S+ and S−. Six healthy volunteers and five patients with osteoarthritis were recruited for whole‐knee imaging. Additionally, two healthy volunteers were recruited for lower leg imaging. Results: The UTE‐Cones‐DESS sequence allows fast volumetric imaging of musculoskeletal tissues with excellent image contrast for the osteochondral junction, tendons, menisci, and ligaments in the knee joint as well as cortical bone and aponeurosis in the lower leg within 5 min. spDixon yields efficient fat suppression in both S+ and S− images without requiring any additional acquisitions or preparation pulses. Conclusion: The rapid UTE‐Cones‐DESS sequence can be used for high contrast morphological imaging of short T2 tissues, providing a new tool to assess their association with musculoskeletal disorders. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate the feasibility of ultrashort echo time quantitative susceptibility mapping (UTE‐QSM) for assessment of hemosiderin deposition in the joints of hemophilic patients. Methods: The UTE‐QSM technique was based on three sets of dual‐echo 3D UTE Cones data acquired with TEs of 0.032/2.8, 0.2/3.6, and 0.4/4.4 ms. The images were processed with iterative decomposition of water and fat with echo asymmetry and least‐squares estimation to estimate the B0 field map in the presence of fat. Then, the projection onto dipole field (PDF) algorithm was applied to acquire a local field map generated by tissues, followed by application of the morphology‐enabled dipole inversion (MEDI) algorithm to estimate a final susceptibility map. Three healthy volunteers and three hemophilic patients were recruited to evaluate the UTE‐QSM technique's ability to assess hemosiderin in the knee or ankle joint at 3T. One patient subsequently underwent total knee arthroplasty after the MR scan. The synovial tissues harvested from the knee joint during surgery were processed for histological analysis to confirm iron deposition. Results: UTE‐QSM successfully yielded tissue susceptibility maps of joints in both volunteers and patients. Multiple regions with high susceptibility over 1 ppm were detected in the affected joints of hemophilic patients, while no localized regions with high susceptibility were detected in asymptomatic healthy volunteers. Histology confirmed the presence of iron in regions where high susceptibility was detected by UTE‐QSM. Conclusion: The UTE‐QSM technique can detect hemosiderin deposition in the joint, and provides a potential sensitive biomarker for the diagnosis and prognosis of hemophilic arthropathy. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine the feasibility of using a single scan ramped hybrid‐encoding (RHE) method for rapid bicomponent T2* analysis of the human knee joint. The proposed method utilizes RHE to acquire ultrashort echo time (UTE) and subsequent gradient echo images at 16 different echo times ranging between 40 μs and 30 ms in a single scan. In the proposed RHE technique, UTE imaging was followed by acquisition of 14 gradient recalled echo images, where an additional UTE image was obtained within the first readout by oversampling single point imaging (SPI) encoding. The single scan RHE method with a 9‐minute scan time was performed on human cadaveric knee joints from six donors and in vivo knee joints from four healthy volunteers at 3 T. A bicomponent signal model was used to characterize the short T2* and long T2* water components. Mean bicomponent T2* parameters for patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL) and meniscus were calculated. In the experimental results, the RHE technique provided bicomponent T2* parameter estimations of tendon, ACL, PCL and meniscus, which were similar to previously reported values in the literature. In conclusion, the proposed single scan RHE technique provides rapid bicomponent T2* analysis of the human knee joint with a total scan time of less than 9 minutes. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the magic angle effect in three‐dimensional ultrashort echo time Cones Adiabatic T1ρ (3D UTE Cones‐AdiabT1ρ) imaging of articular cartilage at 3T. Methods: The magic angle effect was investigated by repeated 3D UTE Cones‐AdiabT1ρ imaging of eight human patellar samples at five angular orientations ranging from 0° to 90° relative to the B0 field. Cones continuous wave T1ρ (Cones‐CW‐T1ρ) and Cones‐ T2∗ sequences were also applied for comparison. Cones‐AdiabT1ρ, Cones‐CW‐T1ρ and Cones‐ T2∗ values were measured for four regions of interest (ROIs) (10% superficial layer, 60% transitional layer, 30% radial layer, and a global ROI) for each sample at each orientation to evaluate their angular dependence. Results: 3D UTE Cones‐AdiabT1ρ values increased from the radial layer to the superficial layer for all angular orientations. The superficial layer showed the least angular dependence (around 4.4%), while the radial layer showed the strongest angular dependence (around 34.4%). Cones‐AdiabT1ρ values showed much reduced magic angle effect compared to Cones‐CW‐T1ρ and Cones‐ T2∗ values for all four ROIs. On average over eight patellae, Cones‐AdiabT1ρ values increased by 27.2% (4.4% for superficial, 23.8% for transitional, and 34.4% for radial layers), Cones‐CW‐T1ρ values increased by 76.9% (11.3% for superficial, 59.1% for transitional, and 117.8% for radial layers), and Cones‐ T2∗ values increased by 237.5% (87.9% for superficial, 262.9% for transitional, and 327.3% for radial layers) near the magic angle. Conclusions: The 3D UTE Cones‐AdiabT1ρ sequence is less sensitive to the magic angle effect in the evaluation of articular cartilage compared to Cones‐ T2∗ and Cones‐CW‐T1ρ. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effect of extending the spiral sampling window on quantitative 3D ultrashort echo time (UTE) Cones imaging of major knee joint tissues including articular cartilage, menisci, tendons and ligaments at 3 T. Nine cadaveric human whole knee specimens were imaged on a 3 T clinical MRI scanner. A series of quantitative 3D UTE Cones imaging biomarkers including T2*, T1, adiabatic T1ρ, magnetization transfer ratio (MTR) and macromolecular fraction (MMF) were estimated using spiral sampling trajectories with various durations. Errors in UTE MRI biomarkers as a function of sampling time were evaluated using a nonstretched spiral trajectory as a reference standard. No significant differences were observed by increasing the spiral sampling window from 1116 to 2232 μs in the calculated T2*, T1, adiabatic T1ρ, MTR and MMF, as all P‐values were over.05 as assessed by ANOVA with two‐sided Dunnett's test. Although extending the sampling window results in signal loss for short T2 components, there was limited effect on the calculated quantitative biomarkers, with error percentages typically smaller than 5% in all the evaluated tissues. The total scan time can be reduced by up to 54% with quantification errors of less than 5% in any evaluated major tissue in the knee joint, suggesting that 3D UTE Cones MRI techniques can be greatly accelerated by using a longer spiral sampling window without causing additional quantitative bias. [ABSTRACT FROM AUTHOR]

Direct myelin imaging is promising for characterization of multiple sclerosis (MS) brains at diagnosis and in response to therapy. In this study, a 3D inversion recovery‐prepared ultrashort echo time cones (IR‐UTE‐Cones) sequence was used for both morphological and quantitative imaging of myelin on a clinical 3 T scanner. Myelin powder phantoms with different myelin concentrations were imaged with the 3D UTE‐Cones sequence and it showed a strong correlation between concentrations and UTE‐Cones signals, demonstrating the ability of the UTE‐Cones sequence to directly image myelin in the brain. Quantitative myelin imaging with multi‐echo IR‐UTE‐Cones sequences show similar T2* values for a D2O‐exchanged myelin phantom (T2* = 0.33 ± 0.04 ms), ex vivo brain specimens (T2* = 0.20 ± 0.04 ms) and in vivo healthy volunteers (T2* = 0.254 ± 0.023 ms), further confirming the feasibility of 3D IR‐UTE‐Cones sequences for direct myelin imaging in vivo. In ex vivo MS brain study, signal loss is observed in MS lesions, which was confirmed with histology. For the in vivo study, the lesions in MS patients also show myelin signal loss using the proposed direct myelin imaging method, demonstrating the clinical potential for MS diagnosis. Furthermore, the measured IR‐UTE‐Cones signal intensities show a significant difference between normal‐appearing white matter in MS patients and normal white matter in volunteers, which cannot be found in clinical used T2‐FLAIR sequences. Thus, the proposed 3D IR‐UTE‐Cones sequence showed clinical potential for MS diagnosis with the capability of direct myelin detection of the whole brain. [ABSTRACT FROM AUTHOR]

Background: Relatively weak correlations between patient symptoms and rotator cuff tendon (RCT) tearing have been reported; however, the relationship between symptoms and tendinosis has been less well-studied.Purpose/hypothesis: To use quantitative MRI to assess the bilateral RCTs in shoulders of both patients with unilateral symptomatic tendinopathy and control subjects. We hypothesized that quantitative MRI measures would differ between symptomatic patients and controls.Study Type: Prospective imaging study.Population/subjects: In all, 48 shoulders from 24 subjects (mean age, 32.8 years), including 14 patients with unilateral symptomatic tendinopathy and 10 asymptomatic controls.Field Strength/sequence: 3T/3D ultrashort echo time Cones sequence with magnetization transfer preparation (UTE-Cones-MT) and Carr-Purcell-Meiboom-Gill.Assessment: Macromolecular fraction (MMF) and T2 relaxation were measured in four regions of the superior RCT, including all-segments, and lateral-third, bursal-sided, and articular-sided segments. The Western Ontario Rotator Cuff (WORC) index and visual analog scale were assessed.Statistical Tests: Three shoulder groups were evaluated, including symptomatic shoulders, contralateral asymptomatic shoulders in patients, and asymptomatic controls. MMF and T2 values were compared between groups using a bootstrap-based comparison of means.Results: Significant differences were found in both MMF and T2 values between symptomatic and control RCTs when analyzing all-segments (P = 0.027 and P = 0.006, respectively) and articular-sided segments (both P = 0.001). Significant differences between asymptomatic RCTs in patients and control RCTs were also found, including MMF in all four anatomic regions analyzed (P = 0.024-0.044), as well as T2 in all-segments (P = 0.003), bursal-sided segments (P = 0.021), and articular-sided segments (P = 0.002). No significant differences in MMF (P = 0.420-0.950) or T2 (P = 0.380-0.910) were seen between ipsilateral symptomatic and contralateral asymptomatic RCTs in patients.Data Conclusion: Symptomatic RCTs showed significantly lower MMF values and higher T2 values compared with control RCTs. In patients with unilateral symptomatic tendinopathy, the contralateral shoulder can demonstrate asymptomatic tendinopathy, which can be quantified using MMF or T2 .Evidence Level: 2 TECHNICAL EFFICACY: Stage 2. J. Magn. Reson. Imaging 2020;52:864-872. [ABSTRACT FROM AUTHOR]

The protons in collagen‐rich musculoskeletal (MSK) tissues such as the Achilles tendon are subject to strong dipolar interactions which are modulated by the term (3cos2θ‐1) where θ is the angle between the fiber orientation and the static magnetic field B0. The purpose of this study was to investigate the magic angle effect in three‐dimensional ultrashort echo time Cones Adiabatic T1ρ (3D UTE Cones‐AdiabT1ρ) imaging of the Achilles tendon using a clinical 3 T scanner. The magic angle effect was investigated by Cones‐AdiabT1ρ imaging of five cadaveric human Achilles tendon samples at five angular orientations ranging from 0° to 90° relative to the B0 field. Conventional Cones continuous wave T1ρ (Cones‐CW‐T1ρ) and Cones T2* (Cones‐T2*) sequences were also applied for comparison. On average, Cones‐AdiabT1ρ increased 3.6‐fold from 13.6 ± 1.5 ms at 0° to 48.4 ± 5.4 ms at 55°, Cones‐CW‐T1ρ increased 6.1‐fold from 7.0 ± 1.1 ms at 0° to 42.6 ± 5.2 ms at 55°, and Cones‐T2* increased 12.3‐fold from 2.9 ± 0.5 ms at 0° to 35.8 ± 6.4 ms at 55°. Although Cones‐AdiabT1ρ is still subject to significant angular dependence, it shows a much‐reduced magic angle effect compared to Cones‐CW‐T1ρ and Cones‐T2*, and may be used as a novel and potentially more effective approach for quantitative evaluation of the Achilles tendon and other MSK tissues. [ABSTRACT FROM AUTHOR]

Purpose: We describe the measurement of bound water T1 (T1BW) of cortical bone in vitro and in vivo with a 3D adiabatic inversion recovery ultrashort echo time (IR‐UTE) Cones sequence using a clinical 3T scanner. Methods: A series IR‐UTE data from 6 repetition times (TRs) with 5 inversion times (TIs) at each TR were acquired from 12 human tibial bone specimens, and data from 4 TRs with 5 TIs at each TR were acquired from the tibial midshafts of 8 healthy volunteers. The pore water nulling point was calculated from exponential fitting of the inversion recovery curve at each TR. Bone specimens and volunteers were then scanned again with the calculated nulling point at each TR. T1BW was derived through exponential fitting of data from IR‐UTE images acquired at different TRs using the calculated pore water nulling point for each TR. Results: In vitro pore water nulling TIs were 141.3 ± 11.6, 123.4 ± 8.9, 101.3 ± 6.2, 88.9 ± 5.3, 74.8 ± 4.2, and 59.2 ± 3.9 ms for the 6 TRs of 500, 400, 300, 250, 200, and 150 ms, respectively. In vivo pore water nulling TIs were 132.8 ± 12.8, 110.3 ± 10.0, 80.0 ± 7.2, and 63.9 ± 5.4 ms for the 4 TRs of 400, 300, 200, and 150 ms, respectively. Excellent exponential fitting was achieved for IR‐UTE imaging of bound water with pore water nulled at each TR. The mean T1BW was 106.9 ± 6.3 ms in vitro and 112.3 ± 16.4 ms in vivo. Conclusion: Using the 3D IR‐UTE Cones with a variable TR/TI approach, T1BW of cortical bone was calculated after complete nulling of pore water signals. [ABSTRACT FROM AUTHOR]

Aim: The objective of this survey was to understand the global trends of imaging assessments in persons with haemophilia, focusing on point‐of‐care ultrasound (POCUS). Insights into the barriers impeding its widespread proliferation as a frontline imaging modality were obtained. Methods: The survey opened in September of 2017 and closed in May of 2018. Haemophilia Treatment Centres (HTCs) treating both paediatric/adult patients were the population of interest. A REDCap survey of 25 questions was disseminated to 232 clinical staff in 26 countries. Results: The majority of respondents (88.3%, 91/103) reported that POCUS is most useful to confirm or rule out a presumed acute joint bleed. European HTCs reported the highest routine use of POCUS at 59.5% (22/37) followed by HTCs in the "Other" countries of the world at 46.7% (7/15) and North American HTCs at 43.9% (25/57). At the time of the survey, physiotherapists were identified as the clinical staff who perform POCUS 52.8% (28/53) of the time, in contrast with nurses/nurse practitioners who represent only 5.7% (3/53) of users. The greatest perceived barriers to the implementation of POCUS are the lack of trained healthcare professionals who can perform POCUS at 69.2% (74/107) and the overall time commitment required at 68.2% (73/107). Conclusion: Despite POCUS being used in 49.5% (54/109) of sampled HTCs, it is still utilized almost 30% less globally than full diagnostic ultrasound. A list of barriers has been identified to inform HTCs which challenges they will likely need to overcome should they choose to incorporate this imaging modality into their practice. [ABSTRACT FROM AUTHOR]

Objectives: To assess the feasibility of using ultrasound (US) image features related to the median nerve echogenicity and shape for carpal tunnel syndrome (CTS) diagnosis. Methods: In 31 participants (21 healthy participants and 10 patients with CTS), US images were collected with a 30‐MHz transducer from median nerves at the wrist crease in 2 configurations: a neutral position and with wrist extension. Various morphologic features, including the cross‐sectional area (CSA), were calculated to assess the nerve shape. Carpal tunnel syndrome commonly results in loss of visualization of the nerve fascicular pattern on US images. To assess this phenomenon, we developed a nerve‐tissue contrast index (NTI) method. The NTI is a ratio of average brightness levels of surrounding tissue and the median nerve, both calculated on the basis of a US image. The area under the curve (AUC) from a receiver operating characteristic curve analysis and t test were used to assess the usefulness of the features for differentiation of patients with CTS from control participants. Results: We obtained significant differences in the CSA and NTI parameters between the patients with CTS and control participants (P <.01), with the corresponding highest AUC values equal to 0.885 and 0.938, respectively. For the remaining investigated morphologic features, the AUC values were less than 0.685, and the differences in means between the patients and control participants were not statistically significant (P >.10). The wrist configuration had no impact on differences in average parameter values (P >.09). Conclusions: Patients with CTS can be differentiated from healthy individuals on the basis of the median nerve CSA and echogenicity. Carpal tunnel syndrome is not manifested in a change of the median nerve shape that could be related to circularity or contour variability. [ABSTRACT FROM AUTHOR]

Purpose: To investigate direct imaging of trabecular bone using a 3D adiabatic inversion recovery prepared ultrashort TE cones (3D IR‐UTE‐Cones) sequence. Methods: The proposed 3D IR‐UTE‐Cones sequence used a broadband adiabatic inversion pulse together with a short TR/TI combination to suppress signals from long T2 tissues such as muscle and marrow fat, followed by multispoke UTE acquisition to detect signal from short T2 water components in trabecular bone. The feasibility of this technique for robust suppression of long T2 tissues was first demonstrated through numerical simulations. The proposed IR‐UTE‐Cones sequence was applied to a hip agarose bone phantom and to 6 healthy volunteers for morphologic and quantitative T2∗ and proton density mapping of trabecular bone. Results: Numeric simulation suggests that the IR technique with a short TR/TI combination provides sufficient suppression of long T2 tissues with a wide range of T1s. High contrast imaging of trabecular bone can be achieved ex vivo and in vivo, with fitted T2∗ values of 0.3–0.45 ms and proton densities of 5–9 mol/L. Conclusion: The 3D IR‐UTE‐Cones sequence with a short TR/TI combination provides robust suppression of long T2 tissues and allows both selective imaging and quantitative (T2∗ and proton density) assessment of short T2 water components in trabecular bone in vivo. [ABSTRACT FROM AUTHOR]

Purpose: Inversion recovery‐based UTE (IR‐UTE) sequences have been proposed to directly image myelin with extremely short T2∗ (~0.3 ms). In this study, we demonstrate the feasibility of complex echo subtraction to improve 3D IR‐UTE imaging of myelin in white matter of the brain in vivo. Methods: In IR‐UTE imaging, long T2 components in white matter (i.e., water) are suppressed using an adiabatic inversion recovery preparation pulse. Dual echo UTE data acquisition and magnitude echo subtraction are used to suppress the residual white matter and gray matter signals, providing high myelin contrast. Complex echo subtraction may further improve the myelin contrast by reducing the residual long T2 water signal contamination caused by regional T1 variations. To verify the efficacy of the complex subtraction technique, in vivo experiments were performed with 5 non‐symptomatic healthy volunteers and 5 multiple sclerosis patients on a 3T clinical MR system. Signal enhancement between the complex subtraction and the magnitude subtraction was introduced to evaluate the improvement. Results: The complex subtraction improved myelin contrast over the magnitude subtraction in both healthy and patient groups, with more fine myelin structures being revealed. The foci of the demyelinated lesion were more clearly detected by complex subtraction. An average signal enhancement of up to 135.9% was achieved with the complex subtraction over the magnitude subtraction. Conclusion: The complex echo subtraction improves 3D IR‐UTE morphologic imaging of myelin in white matter of the brain. [ABSTRACT FROM AUTHOR]

Purpose: Direct myelin imaging can improve the characterization of myelin‐related diseases such as multiple sclerosis. In this study, we explore a novel method to directly image myelin using inversion recovery‐prepared hybrid encoding (IR‐HE) UTE MRI. Methods: The IR‐HE sequence uses an adiabatic inversion pulse to suppress the long T2 white matter signal, followed by 3D dual‐echo HE utilizing both single point imaging and radial frequency encoding, for which the subtraction image between 2 echoes reveals the myelin signal with high contrast. To reduce scan time, it is common to obtain multiple spokes per IR. Here, we invented a novel method to improve the HE, adapted for the multi‐spoke IR imaging—termed interleavedHE—for which single point imaging encoding is interleaved between radial frequency encodings near nulling point to allow more efficient IR‐signal suppression. To evaluate the proposed approach, a computer simulation, myelin phantom experiment, an ex vivo experiment with a cadaveric multiple sclerosis brain, and an in vivo experiment with 8 healthy volunteers and 13 multiple sclerosis patients were performed. Results: The computer simulation showed that IR‐interleaved HE allows for improved contrast of myelin signal with reduced imaging artifacts. The myelin phantom experiment showed IR‐interleaved HE allows direct imaging of myelin lipid with excellent suppression of water signal. In the ex vivo and in vivo experiments, the proposed method demonstrated highly specific imaging of myelin in white matter of the brain. Conclusion: IR‐interleaved HE allows for time‐efficient, high‐contrast direct myelin imaging and can detect demyelinated lesions in multiple sclerosis patients. [ABSTRACT FROM AUTHOR]

Purpose: To develop a deep learning‐based method for knee menisci segmentation in 3D ultrashort echo time (UTE) cones MR imaging, and to automatically determine MR relaxation times, namely the T1, T1ρ, and T2∗ parameters, which can be used to assess knee osteoarthritis (OA). Methods: Whole knee joint imaging was performed using 3D UTE cones sequences to collect data from 61 human subjects. Regions of interest (ROIs) were outlined by 2 experienced radiologists based on subtracted T1ρ‐weighted MR images. Transfer learning was applied to develop 2D attention U‐Net convolutional neural networks for the menisci segmentation based on each radiologist's ROIs separately. Dice scores were calculated to assess segmentation performance. Next, the T1, T1ρ, T2∗ relaxations, and ROI areas were determined for the manual and automatic segmentations, then compared. Results: The models developed using ROIs provided by 2 radiologists achieved high Dice scores of 0.860 and 0.833, while the radiologists' manual segmentations achieved a Dice score of 0.820. Linear correlation coefficients for the T1, T1ρ, and T2∗ relaxations calculated using the automatic and manual segmentations ranged between 0.90 and 0.97, and there were no associated differences between the estimated average meniscal relaxation parameters. The deep learning models achieved segmentation performance equivalent to the inter‐observer variability of 2 radiologists. Conclusion: The proposed deep learning‐based approach can be used to efficiently generate automatic segmentations and determine meniscal relaxations times. The method has the potential to help radiologists with the assessment of meniscal diseases, such as OA. [ABSTRACT FROM AUTHOR]

Purpose: To design a soft‐hard composite pulse for fat suppression and water excitation in ultrashort echo time (UTE) imaging with minimal short T2 signal attenuation. Methods: The composite pulse contains a narrow bandwidth soft pulse centered on the fat peak with a small negative flip angle (–α) and a short rectangular pulse with a small positive flip angle (α). The fat magnetization experiences both tipping‐down and ‐back with an identical flip angle and thus returns to the equilibrium state, leaving only the excited water magnetization. Bloch simulations, as well as knee, tibia, and ankle UTE imaging studies, were performed to investigate the effectiveness of fat suppression and corresponding water signal attenuation. A conventional fat saturation (FatSat) module was used for comparison. Signal suppression ratio (SSR), defined as the ratio of signal difference between non‐fat‐suppression and fat‐suppression images over the non‐fat‐suppression signal, was introduced to evaluate the efficiency of the composite pulse. Results: Numerical simulations demonstrate that the soft‐hard pulse has little saturation effect on short T2 water signals. Knee, tibia, and ankle UTE imaging results suggest that comparable fat suppression can be achieved with the soft‐hard pulse and the FatSat module. However, much less water saturation is induced by the soft‐hard pulse, especially for short T2 tissues, with SSRs reduced from 71.8 ± 6.9% to 5.8 ± 4.4% for meniscus, from 68.7 ± 5.5% to 7.7 ± 7.6% for bone, and from 62.9 ± 12.0% to 4.8 ± 3.2% for the Achilles tendon. Conclusion: The soft‐hard composite pulse can suppress fat signals in UTE imaging with little signal attenuation on short T2 tissues. [ABSTRACT FROM AUTHOR]

Introduction: Evidence suggests that toxic iron is involved in haemophilic joint destruction. Aim: To determine whether joint iron deposition is linked to clinical and imaging outcomes in order to optimize management of haemophilic joint disease. Methods: Adults with haemophilia A or haemophilia B (n = 23, ≥ age 21) of all severities were recruited prospectively to undergo assessment with Hemophilia Joint Health Scores (HJHS), pain scores (visual analogue scale [VAS]) and magnetic resonance imaging (MRI) at 3T using conventional MRI protocols and 4‐echo 3D‐UTE‐Cones sequences for one affected arthropathic joint. MRI was scored blinded by two musculoskeletal radiologists using the International Prophylaxis Study Group (IPSG) MRI scale. Additionally, UTE‐T2* values of cartilage were quantified. Correlations between parameters were performed using Spearman rank correlation. Two patients subsequently underwent knee arthroplasty, which permitted linking of histological findings (including Perl's reaction) with MRI results. Results: MRI scores did not correlate with pain scores or HJHS. Sixteen joints had sufficient cartilage for UTE‐T2* analysis. T2* values for cartilage correlated inversely with HJHS (rs = −0.81, P < 0.001) and MRI scores (rs = −0.52, P = 0.037). This was unexpected since UTE‐T2* values decrease with better joint status in patients with osteoarthritis, suggesting that iron was present and responsible for the effects. Histological analysis of cartilage confirmed iron deposition within chondrocytes, associated with low UTE‐T2* values. Conclusions: Iron accumulation can occur in cartilage (not only in synovium) and shows a clear association with joint health. Cartilage iron is a novel biomarker which, if quantifiable with innovative joint‐specific MRI T2* sequences, may guide treatment optimization. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of stretching sampling window on quantitative 3D ultrashort TE (UTE) imaging of cortical bone at 3 T. Methods: Ten bovine cortical bone and 17 human tibial midshaft samples were imaged with a 3T clinical MRI scanner using an 8‐channel knee coil. Quantitative 3D UTE imaging biomarkers, including T1, T2∗, magnetization transfer ratio and magnetization transfer modeling, were performed using radial or spiral Cones sampling trajectories with various durations. Errors in UTE‐MRI biomarkers as a function of sampling time were evaluated using radial sampling as a reference standard. Results: For both bovine and human cortical bone samples, no significant differences were observed for all UTE biomarkers (single‐component T2∗, bicomponent T2∗ and relative fractions, T1, magnetization transfer ratio, and magnetization transfer modeling of macromolecular fraction) for spiral sampling windows of 992 µs to 1600 µs compared with a radial sampling window of 688 µs. Conclusion: The total scan time can be reduced by 76% with quantification errors less than 5%. Quantitative UTE‐MRI techniques can be greatly accelerated using longer sampling windows without significant quantification errors. [ABSTRACT FROM AUTHOR]

Purpose: To investigate tricomponent analysis of human cortical bone using a multipeak fat signal model with 3D ultrashort TE Cones sequences on a clinical 3T scanner. Methods: Tricomponent fitting of bound water, pore water, and fat content using a multipeak fat spectra model was proposed for 3D ultrashort TE imaging of cortical bone. Three‐dimensional ultrashort TE Cones acquisitions combined with tricomponent analysis were used to investigate bound and pore water T2∗ and fractions, as well as fat T2∗ and fraction in cortical bone. Feasibility studies were performed on 9 human cortical bone specimens with regions of interest selected from the endosteum to the periosteum in 4 circumferential regions. Microcomputed tomography studies were performed to measure bone porosity and bone mineral density for comparison and validation of the bound and pore water analyses. Results: The oscillation of the signal decay was well‐fitted with the proposed tricomponent model. The sum of the pore water and fat fractions from tricomponent analysis showed a high correlation with microcomputed tomography porosity (R = 0.74, P < 0.01). Estimated bound‐water fraction also demonstrated a high correlation with bone mineral density (R = 0.70, P < 0.01). Conclusion: Tricomponent analysis significantly improves the estimation of bound‐water and pore‐water fractions in human cortical bone. [ABSTRACT FROM AUTHOR]

Objectives: Musculoskeletal ultrasound (US) is used increasingly to examine hemophilic arthropathy. However, quantitative algorithms to document findings are lacking. We developed and sought to validate a protocol quantifying hemophilic joint abnormalities. Methods: Thirty‐one patients with hemophilia were examined serially for 2 years with musculoskeletal US (≈600 joint examinations and ≈6000 images). Based on the spectrum of pathologies, a quantitative algorithm, named Joint Tissue Activity and Damage Examination (JADE), was developed for soft tissue and osteochondral measurements, including power Doppler, using nominal group techniques. To study intra‐ and inter‐rater reliability, 8 musculoskeletal US–experienced hemophilia providers performed anatomic landmark recognition and tissue measurements on 86 images with arthropathic changes, with repetition 1 month later. Twenty‐three musculoskeletal US–inexperienced providers performed similar assessments. Inter‐operator reliability was established by 6 musculoskeletal US–experienced hemophilia providers, each acquiring images and JADE assessments of 3 hemophilic arthropathic joints. A radiologist and musculoskeletal sonographer functioned as adjudicators. The statistical analysis was performed with the intraclass correlation coefficient (ICC), Fleiss κ, and Cohen κ where appropriate. Results: The musculoskeletal US–experienced providers showed excellent intra‐and inter‐rater reliability for tissue measurements (ICCs, 0.94–0.96). Agreement was good to excellent for landmark recognition (Fleiss κ, 0.87‐0.94). Inter‐operator reliability was excellent for measurements and landmark recognition (ICC, 0.90; Fleiss κ, 1.0). Agreement with adjudicators was mostly good to excellent. Musculoskeletal US–inexperienced providers showed excellent inter‐rater reliability for measurements (ICC, 0.96) and moderate agreement for landmark recognition (Fleiss κ, 0.58). Conclusions: The JADE protocol appears feasible for quantifying hemophilic intra‐articular abnormalities. Musculoskeletal US–trained hemophilia providers showed high intra‐rater, inter‐rater, and inter‐operator reliability, supporting JADE as a protocol for clinical management and research. [ABSTRACT FROM AUTHOR]

Pelvic floor disorders negatively impact millions of women worldwide. Although there is a strong epidemiological association with childbirth, the mechanisms leading to the dysfunction of the integral constituents of the female pelvic floor, including pelvic floor skeletal muscles, are not well understood. This is in part due to the constraints associated with directly probing these muscles, which are located deep in the pelvis. Thus, experimental models and non‐invasive techniques are essential for advancing knowledge of various phenotypes of pelvic floor muscle injury and pathogenesis of muscle dysfunction, as well as developing minimally invasive approaches for the delivery of novel therapeutics. The most widely used animal model for pelvic floor disorders is the rat. However, the radiological anatomy of rat pelvic floor muscles has not been described. To remedy this gap, the current study provides the first detailed description of the female rat pelvic floor muscles' radiological appearance on MR and ultrasound images, validated by correlation with gross anatomy and histology. We also demonstrate that ultrasound guidance can be used to target rat pelvic floor muscles for possible interventional therapies. [ABSTRACT FROM AUTHOR]

Purpose: In this study, we explore the feasibility of a new imaging scheme for quantitative susceptibility mapping (QSM): continuous single‐point imaging (CSPI), which uses a pure phase encoding strategy to achieve true phase imaging and improve QSM accuracy. Methods: The proposed CSPI is a modification of conventional SPI to allow acquisition of multiple echoes in a single scan. Immediately following a phase encoding gradient, the free induction decay is continuously sampled with extremely high temporal resolution to obtain k‐space data at a fixed spatial frequency (i.e., at a fixed k‐space coordinate). By having near‐0 readout duration, CSPI results in a true snapshot of the transverse magnetization at each TE. Additionally, parallel imaging with autocalibration is utilized to reduce scan time, and an optional temporal averaging strategy is presented to improve signal‐to‐noise ratio for objects with low proton density or short T2* decay. The reconstructed CSPI images were input to a QSM framework based on morphology enabled dipole inversion. Result: In an experiment performed using iron phantoms, susceptibility estimated using CSPI showed high linearity (R2 = 0.9948) with iron concentration. Additionally, reconstructed CSPI phase images showed much reduced ringing artifact compared with phase images obtained using a frequency encoding strategy. In an ex vivo experiment performed using human tibia samples, estimated susceptibilities ranged from –1.6 to –2.1 ppm, in agreement with values reported in the literature (ranging from –1.2 to –2.2 ppm). Conclusion: We have demonstrated the feasibility of using CSPI to obtain true phase images for QSM. [ABSTRACT FROM AUTHOR]

Purpose: To measure T1 relaxations for the major tissues in whole knee joints on a clinical 3T scanner. Methods: The 3D UTE‐Cones actual flip angle imaging (AFI) method was used to map the transmission radiofrequency field (B1) in both short and long T2 tissues, which was then used to correct the 3D UTE‐Cones variable flip angle (VFA) fitting to generate accurate T1 maps. Numerical simulation was carried out to investigate the accuracy of T1 measurement for a range of T2 values, excitation pulse durations, and B1 errors. Then, the 3D UTE‐Cones AFI‐VFA method was applied to healthy volunteers (N = 16) to quantify the T1 of knee tissues including cartilage, meniscus, quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), marrow, and muscles at 3T. Results: Numerical simulation showed that the 3D UTE‐Cones AFI‐VFA technique can provide accurate T1 measurements (error <1%) when the tissue T2 is longer than 1 ms and a 150 μs excitation RF pulse is used and therefore is suitable for most knee joint tissues. The proposed 3D UTE‐Cones AFI‐VFA method showed an average T1 of 1098 ± 67 ms for cartilage, 833 ± 47 ms for meniscus, 800 ± 66 ms for quadriceps tendon, 656 ± 43 ms for patellar tendon, 873 ± 38 ms for ACL, 832 ± 49 ms for PCL, 379 ± 18 ms for marrow, and 1393 ± 46 ms for muscles. Conclusion: The 3D UTE‐Cones AFI‐VFA method allows volumetric T1 measurement of the major tissues in whole knee joints on a clinical 3T scanner. [ABSTRACT FROM AUTHOR]

Abstract This report describes a severe injury to the proximal rectus femoris (RF) muscle in a 37-year-old recreational athlete. This injury is a relatively rare occurrence in both the general and elite athletic populations. Acute and long-term imaging and functional outcomes are described. This athlete was able to return to full activity without surgical intervention. Follow-up imaging demonstrated gross healing of both complete (or near complete) muscle and tendon tears. Level of Evidence V [ABSTRACT FROM AUTHOR]

Purpose: To develop a 3D adiabatic T1ρ prepared ultrashort echo time cones (3D AdiabT1ρ UTE‐Cones) sequence for whole knee imaging on a clinical 3T scanner. Methods: A train of adiabatic full passage pulses were used for spin locking, followed by time‐efficient multispoke UTE acquisition to detect signals from both short and long T2 tissues in the whole knee joint. A modified signal model was proposed for multispoke UTE data fitting. The feasibility of this 3D AdiabT1ρ UTE‐Cones technique was demonstrated through numerical simulation, phantom, and ex vivo knee sample studies. The 3D AdiabT1ρ UTE‐Cones technique was then applied to 6 in vivo knee joints of healthy volunteers to measure T1ρ values of quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), meniscus, patellar cartilage, and muscle. Results: Numerical simulation, phantom and ex vivo knee sample studies demonstrated the feasibility of whole knee imaging using the proposed multispoke 3D AdiabT1ρ UTE‐Cones sequence. The healthy volunteer knee study demonstrated an averaged T1ρ of 13.9 ± 0.7 ms for the quadriceps tendon, 9.7 ± 0.8 ms for the patellar tendon, 34.9 ± 2.8 ms for the ACL, 21.6 ± 1.4 ms for the PCL, 22.5 ± 1.9 ms for the meniscus, 44.5 ± 2.4 ms for the patellar cartilage, and 43.2 ± 1.1 ms for the muscle. Conclusion: The 3D AdiabT1ρ UTE‐Cones sequence allows volumetric T1ρ assessment of both short and long T2 tissues in the knee joint on a clinical 3T scanner. [ABSTRACT FROM AUTHOR]

Peripheral nerves are a composite tissue consisting of neurovascular elements packaged within a well‐organized extracellular matrix. Their composition, size, and anatomy render nerves a challenging medical imaging target. In contrast to morphological MRI, which represents the predominant approach to nerve imaging, quantitative MRI sequences can provide information regarding tissue composition. Here, we applied standard clinical Carr‐Purcell‐Meiboom‐Gill (CPMG) and experimental three‐dimensional (3D) ultrashort echo time (UTE) Cones sequences for quantitative nerve imaging including T2 measurement with single‐component analysis, T2* measurement with single‐component and bi‐component analyses, and magnetization transfer ratio (MTR) analysis. We demonstrated the feasibility and the high quality of single‐component T2*, bi‐component T2*, and MTR approaches to analyze nerves imaged with clinically deployed 3D UTE Cones pulse sequences. For 24 single fascicles from eight nerves, we measured a mean single‐component T2* of 22.6 ±8.9 ms, and a short T2* component (STC) with a mean T2* of 1.7 ±1.0 ms and a mean fraction of (6.74 ±4.31)% in bi‐component analysis. For eight whole nerves, we measured a mean single‐component T2* of 16.7 ±2.2 ms, and an STC with a mean T2* of 3.0 ±1.0 ms and a mean fraction of (15.56 ±7.07)% in bi‐component analysis. For nine fascicles from three healthy nerves, we measured a mean MTR of (25.2 ±1.9)% for single fascicles and a mean MTR of (23.6 ±0.9)% for whole nerves. No statistically significant correlation was observed between any MRI parameter and routine histological outcomes, perhaps due to the small sample size and lack of apparent sample pathology. Overall, we have successfully demonstrated the feasibility of measuring quantitative MR outcomes ex vivo, which might reflect features of nerve structure and macromolecular content. These methods should be validated comprehensively on a larger and more diverse set of nerve samples, towards the interpretation of in vivo outcomes. These approaches have new and broad implications for the management of nerve disease, injury, and repair. [ABSTRACT FROM AUTHOR]

Purpose: To develop an accurate T1 measurement method for short T2 tissues using a combination of a 3‐dimensional ultrashort echo time cones actual flip angle imaging technique and a variable repetition time technique (3D UTE‐Cones AFI‐VTR) on a clinical 3T scanner. Methods: First, the longitudinal magnetization mapping function of the excitation pulse was obtained with the 3D UTE‐Cones AFI method, which provided information about excitation efficiency and B1 inhomogeneity. Then, the derived mapping function was substituted into the VTR fitting to generate accurate T1 maps. Numerical simulation and phantom studies were carried out to compare the AFI‐VTR method with a B1‐uncorrected VTR method, a B1‐uncorrected variable flip angle (VFA) method, and a B1‐corrected VFA method. Finally, the 3D UTE‐Cones AFI‐VTR method was applied to bovine bone samples (N = 6) and healthy volunteers (N = 3) to quantify the T1 of cortical bone. Results: Numerical simulation and phantom studies showed that the 3D UTE‐Cones AFI‐VTR technique provides more accurate measurement of the T1 of short T2 tissues than the B1‐uncorrected VTR and VFA methods or the B1‐corrected VFA method. The proposed 3D UTE‐Cones AFI‐VTR method showed a mean T1 of 240 ± 25 ms for bovine cortical bone and 218 ± 10 ms for the tibial midshaft of human volunteers, respectively, at 3 T. Conclusion: The 3D UTE‐Cones AFI‐VTR method can provide accurate T1 measurements of short T2 tissues such as cortical bone. Magn Reson Med 80:598–608, 2018. © 2018 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Objectives: Point‐of‐care musculoskeletal ultrasound (US) is increasingly used by hemophilia providers to guide management; however, pathologic tissue differentiation with US is uncertain. We sought to determine the extent to which point‐of‐care musculoskeletal US can identify and discriminate pathologic soft tissue changes in hemophilic arthropathy. Methods: Thirty‐six adult patients with hemophilia A/B were prospectively enrolled. Point‐of‐care musculoskeletal US examinations were performed on arthropathic joints (16 knees, 10 ankles, and 10 elbows) using standard views by a musculoskeletal US–trained and certified hematologist, who recorded abnormal intra‐articular soft tissue accumulation. Within 3 days, magnetic resonance imaging was performed using conventional and multiecho ultrashort echo time sequences. Soft tissue identification (synovial proliferation with or without hemosiderin, fat, and/or blood products) was performed by a musculoskeletal radiologist. Findings obtained with both imaging modalities were compared and correlated in a blinded fashion. Results: There was perfect agreement between the modalities on the presence of abnormal soft tissue (34 of 36 cases). However, musculoskeletal US was unable to discriminate between coagulated blood, synovium, intrasynovial or extrasynovial fat tissue, or hemosiderin deposits because of wide variations in echogenicity. Conclusions: Musculoskeletal US is valuable for point‐of‐care imaging to determine the presence of soft tissue accumulation in discrete areas. However, because of limitations of musculoskeletal US in discriminating the nature of pathologic soft tissues and detecting hemosiderin, magnetic resonance imaging will be required if such discrimination is clinically important. [ABSTRACT FROM AUTHOR]

Background: Rotator cuff tendons (RCTs) are challenging to image due to the "magic angle effect" and their short T2 .Purpose: To assess the degree of magic angle sensitivity of human RCTs and to utilize a 3D ultrashort echo time Cones sequence with magnetization transfer preparation (UTE-Cones-MT) and two-pool quantitative MT modeling with histological correlation. We hypothesized that MT parameters would be less sensitive to the magic angle compared with conventional T2 measurements.Study Type: Prospective imaging pathologic correlation.Specimen: Twenty cadaveric rotator cuff tendons were imaged at five sample orientations ranging from 0-90° relative to the B0 field.Field Strength/sequence: 3T/3D UTE-Cones-MT and Carr-Purcell-Meiboom-Gill (CPMG).Assessment: Two-pool quantitative MT modeling parameters and T2 values were calculated in regions of interest drawn by a medical physicist. Histopathological analysis was performed and mild and severe tendinopathy groups were assigned by a histopathologist and histotechnician.Statistical Tests: Coefficients of variations (CVs) were calculated for measures between the different orientations and group means were compared for each measure.Results: CVs of T2 and macromolecular fractions between orientations were 26.14 ± 16.82% and 6.18 ± 2.77% (mean ± SD), respectively. T2 measurements at 0°, 27°, 70°, and 90° showed significant differences between the two histological groups (P = 0.004, 0.008, 0.003, and 0.015, respectively), but not at 55° (P = 0.611). Mean T2 value ranges between orientations for the mild and severe tendinopathy groups were 15.27-30.32 msec and 20.81-35.85 msec, respectively, showing overlap despite statistically significant differences (P = 0.003). Macromolecular fractions at all angles showed significant differences between the two groups (P < 0.0001). Mean fraction ranges between orientations for the mild and severe tendinopathy groups were 14.32-17.17% and 10.00-13.75% respectively (P < 0.0001) with no overlap.Data Conclusion: Compared with T2 , macromolecular fraction obtained with the 3D UTE-Cones-MT technique is resistant to the magic angle effect and is more sensitive to RCT degeneration.Level Of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2017. [ABSTRACT FROM AUTHOR]

Purpose: To investigate high contrast imaging of short T2 tissues with a three‐dimensional double adiabatic inversion recovery prepared ultrashort echo time Cones (3D DIR‐UTE‐Cones) sequence. Methods: The sequence used two sequential adiabatic inversion pulses to suppress signals from long T2 tissues, followed by multispoke UTE acquisition to detect signals from short T2 tissues. The two adiabatic inversion pulses are identical with a center frequency located at the water peak, but the spectral width is broad enough to cover both water and fat frequencies. The feasibility of this technique was demonstrated through numerical simulation and phantom studies. Finally, DIR‐UTE‐Cones was applied to three healthy volunteers to image cortical bone, patellar tendon, and Achilles tendon. T 2 * was also measured via single‐component exponential fitting. Results: Numerical simulation suggests that the DIR technique provides perfect nulling of muscle and fat as well as efficient suppression of other long T2 tissues with T1 values between fat and water or those above water. Excellent image contrast can be achieved with DIR‐UTE‐Cones for the short T2 tissues, with fitted T 2 * values of 0.28–0.38 ms for cortical bone, 0.56 ± 0.07 ms for the patella tendon, and 0.45 ± 0.06 ms for the Achilles tendon, respectively. Conclusion: The 3D DIR‐UTE‐Cones sequence provides robust suppression of long T2 tissues and allows selective imaging as well as T 2 * measurement of short T2 tissues such as cortical bone, patellar tendon, and the Achilles tendon. Magn Reson Med 79:2555–2563, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Purpose: To investigate quantitative 2D ultrashort echo time magnetization transfer (UTE-MT) imaging in ex vivo bovine cortical bone and in vivo human tibial cortical bone. Methods: Data were acquired from five fresh bovine cortical bone samples and five healthy volunteer tibial cortical bones using a 2D UTE-MT sequence on a clinical 3T scanner. The 2D UTE-MT sequence used four or five MT powers with five frequency offsets. Results were analyzed with a two-pool quantitative MT model, providing measurements of macromolecular fraction (f), macromolecular proton transverse relaxation times (T2m), proton exchange rates from water/macromolecular to the macromolecular/water pool (RM0m/RM0w), and spin-lattice relaxation rate of water pool (R1w). A sequential air-drying study for a small bovine cortical bone chip was used to investigate whether above MT modeling parameters were sensitive to the water loss. Results: Mean fresh bovine cortical bone values for f, T2m, R1w, RM0m, and RM0w were 59.9 ± 7.3%, 14.6 ± 0.3 μs, 9.9 ± 2.4 s−1, 17.9 ± 3.6 s−1, and 11.8 ± 2.0 s−1, respectively. Mean in vivo human cortical bone values for f, T2m, R1w, RM0m and RM0w were 54.5 ± 4.9%, 15.4 ± 0.6 μs, 8.9 ± 1.1 s−1, 11.5 ± 3.5 s−1, and 9.5 ± 1.9 s−1, respectively. The sequential air-drying study shows that f, RM0m, and R1w were increased with longer drying time. Conclusion: UTE-MT two-pool modeling provides novel and useful quantitative information for cortical bone. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the echo dependence of 3D ultrashort echo time (TE) quantitative susceptibility mapping (3D UTE-QSM) and effective transverse relaxation rate ( R*2) measurement in the setting of high concentrations of iron oxide nanoparticles. Methods: A phantom study with iron concentrations ranging from 2 to 22 mM was performed using a 3D UTE Cones sequence. Simultaneous QSM processing with morphology-enabled dipole inversion (MEDI) and R*2 single exponential fitting was conducted offline with the acquired 3D UTE data. The dependence of UTE-QSM and R*2 on echo spacing (ΔTE) and first TE (TE1) was investigated. Results: A linear relationship was observed between UTE-QSM measurement and iron concentration up to 22 mM only, with the minimal TE1 of 0.032 ms and ΔTE of less than 0.1 ms. A linear relationship was observed between R*2 and iron concentration up to 22 mM only when TE1 was less than 0.132 ms and ΔTE was less than 1.2 ms. UTE-QSM with MEDI processing showed strong dependence on ΔTE and TE1, especially at high iron concentrations. Conclusion: UTE-QSM is more sensitive than R*2 measurement to TE selection. Both an ultrashort TE1 and a small ΔTE are needed to achieve accurate QSM for high iron concentrations. Magn Reson Med 79:2315–2322, 2018. © 2018 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Purpose To accelerate the quantitative ultrashort echo time imaging using a time-efficient 3D multispoke Cones sequence with magnetization transfer (3D UTE-Cones-MT) and signal modeling. Theory and Methods A 3D UTE-Cones-MT acquisition scheme with multispoke per MT preparation and a modified rectangular pulse (RP) approximation was developed for two-pool MT modeling of macromolecular and water components including their relative fractions, relaxation times and exchange rates. Numerical simulation and cadaveric specimens, including human Achilles tendon and bovine cortical bone, were investigated using a clinical 3T scanner. Results Numerical simulation showed that the modified RP model provided accurate estimation of MT parameters when multispokes were acquired per MT preparation. For the experiment with the Achilles tendon and cortical bone samples, the macromolecular fractions were 20.4 ± 2.0% and 59.4 ± 5.3%, respectively. Conclusion The 3D multispoke UTE-Cones-MT sequence can be used for fast volumetric assessment of macromolecular and water components in short T2 tissues. Magn Reson Med 79:692-700, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Inversion recovery ultrashort echo time (IR-UTE) imaging holds the potential to directly characterize MR signals from ultrashort T2 tissue components (STCs), such as collagen in cartilage and myelin in brain. The application of IR-UTE for myelin imaging has been challenging because of the high water content in brain and the possibility that the ultrashort T2* signals are contaminated by water protons, including those associated with myelin sheaths. This study investigated such a possibility in an ovine brain D2O exchange model and explored the potential of IR-UTE imaging for the quantification of ultrashort T2* signals in both white and gray matter at 3 T. Six specimens were examined before and after sequential immersion in 99.9% D2O. Long T2 MR signals were measured using a clinical proton density-weighted fast spin echo (PD-FSE) sequence. IR-UTE images were first acquired with different inversion times to determine the optimal inversion time to null the long T2 signals (TInull). Then, at this TInull, images with echo times (TEs) of 0.01-4 ms were acquired to measure the T2* values of STCs. The PD-FSE signal dropped to near zero after 24 h of immersion in D2O. A wide range of TInull values were used at different time points (240-330 ms for white matter and 320-350 ms for gray matter at TR = 1000 ms) because the T1 values of the long T2 tissue components changed significantly. The T2* values of STCs were 200-300 μs in both white and gray matter (comparable with the values obtained from myelin powder and its mixture with D2O or H2O), and showed minimal changes after sequential immersion. The ultrashort T2* signals seen on IR-UTE images are unlikely to be from water protons as they are exchangeable with deuterons in D2O. The source is more likely to be myelin itself in white matter, and might also be associated with other membranous structures in gray matter. [ABSTRACT FROM AUTHOR]

Purpose To investigate two-dimensional (2D) and three-dimensional (3D) ultrashort echo time (UTE) and 3D magnetization-prepared rapid gradient-echo (MP-RAGE) sequences for the imaging of iron-oxide nanoparticles (IONP). Methods The phantoms were composed of tubes filled with different IONP concentrations ranging from 2 to 45 mM. The tubes were fixed in an agarose gel phantom (0.9% by weight). Morphological imaging was performed with 3D MP-RAGE, 2D UTE, 2D adiabatic inversion recovery-prepared UTE (2D IR-UTE), 3D UTE with Cones trajectory (3D Cones), and 3D IR-Cones sequences. Quantitative assessment of IONP concentration was performed using [ABSTRACT FROM AUTHOR]