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In 2019, the Journal of Nuclear Cardiology published excellent articles pertaining to imaging in patients with cardiovascular disease. In this review we will summarize a selection of these articles to provide a concise review of the main advancements that have recently occurred in the field and provide the reader with an opportunity to review a wide selection of articles. In this first article of this 2-part series we will focus on publications dealing with positron emission tomography, computed tomography and magnetic resonance. We will specifically discuss imaging as it relates to coronary artery disease, atherosclerosis and inflammation, coronary artery calcification, cardiomyopathies, cardiac implantable electronic devices, prosthetic valves, and left ventricular assist devices. The second part of this review will place emphasis on myocardial perfusion imaging using single-photon emission computed tomography.

Amyloidosis is a disease that develops when abnormally folded proteins collect together to form amyloid fibrils, which deposit in various organs and cause organ damage. Amyloidosis in the heart can be identified by using various imaging tests. This patient page provides an overview of imaging in cardiac amyloidosis.

Widespread clinical use of MRI radiomic tumor profiling for prognostication and treatment planning in cancers faces major obstacles due to limitations in standardization of radiomic features. The purpose of the current work was to assess the impact of different MRI scanning- and normalization protocols for the statistical analyses of tumor radiomic data in two patient cohorts with uterine endometrial-(EC) (n = 136) and cervical (CC) (n = 132) cancer. 1.5 T and 3 T, T1-weighted MRI 2 min post-contrast injection, T2-weighted turbo spin echo imaging, and diffusion-weighted imaging were acquired. Radiomic features were extracted from within manually segmented tumors in 3D and normalized either using z-score normalization or a linear regression model (LRM) accounting for linear dependencies with MRI acquisition parameters. Patients were clustered into two groups based on radiomic profile. Impact of MRI scanning parameters on cluster composition and prognostication were analyzed using Kruskal–Wallis tests, Kaplan–Meier plots, log-rank test, random survival forests and LASSO Cox regression with time-dependent area under curve (tdAUC) (α = 0.05). A large proportion of the radiomic features was statistically associated with MRI scanning protocol in both cohorts (EC: 162/385 [42%]; CC: 180/292 [62%]). A substantial number of EC (49/136 [36%]) and CC (50/132 [38%]) patients changed cluster when clustering was performed after z-score-versus LRM normalization. Prognostic modeling based on cluster groups yielded similar outputs for the two normalization methods in the EC/CC cohorts (log-rank test; z-score: p = 0.02/0.33; LRM: p = 0.01/0.45). Mean tdAUC for prognostic modeling of disease-specific survival (DSS) by the radiomic features in EC/CC was similar for the two normalization methods (random survival forests; z-score: mean tdAUC = 0.77/0.78; LRM: mean tdAUC = 0.80/0.75; LASSO Cox; z-score: mean tdAUC = 0.64/0.76; LRM: mean tdAUC = 0.76/0.75). Severe biases in tumor radiomics data due to MRI scanning parameters exist. Z-score normalization does not eliminate these biases, whereas LRM normalization effectively does. Still, radiomic cluster groups after z-score- and LRM normalization were similarly associated with DSS in EC and CC patients. [ABSTRACT FROM AUTHOR]

Simple Summary: This is a contemporary overview of how cardiology issues arise in the breast cancer population from anti-cancer agents (e.g., chemotherapy, targeted therapy, endocrine therapy, and radiotherapy). The overview demonstrates how we identify these cardiac issues and what we can do about them. Breast cancer is amongst the most common invasive cancers in adults. There are established relationships between anti-cancer treatments for breast cancer and cardiovascular side effects. In recent years, novel anti-cancer treatments have been established, as well as the availability of multi-modal cardiac imaging and the sophistication of treatment for cardiac disease. This review provides an in-depth overview regarding the interface of breast cancer and cancer therapy-related cardiovascular toxicity. Specifically, it reviews the pathophysiology of breast cancer, the method of action in therapy-related cardiovascular toxicity from anti-cancer treatment, the use of echocardiography, cardiac CT, MRI, or nuclear medicine as diagnostics, and the current evidence-based treatments available. It is intended to be an all-encompassing review for clinicians caring for patients in this situation. [ABSTRACT FROM AUTHOR]

Background and Purpose: The purpose of this study is to evaluate the feasibility of using 3‐dimensional (3D) ultra‐short echo time (UTE) radial imaging method for measurement of the permeability of the blood‐brain barrier (BBB) to gadolinium‐based contrast agent. In this study, we propose to use the golden‐angle radial sparse parallel (GRASP) method with 3D center‐out trajectories for UTE, hence named as 3D UTE‐GRASP. We first examined the feasibility of using 3D UTE‐GRASP dynamic contrast‐enhanced (DCE)‐magnetic resonance imaging (MRI) for differentiating subtle BBB disruptions induced by focused ultrasound (FUS). Then, we examined the BBB permeability changes in Alzheimer's disease (AD) pathology using Alzheimer's disease transgenic mice (5xFAD) at different ages. Methods: For FUS experiments, we used four Sprague Dawley rats at similar ages where we compared BBB permeability of each rat receiving the FUS sonication with different acoustic power (0.4‐1.0 MPa). For AD transgenic mice experiments, we included three 5xFAD mice (6, 12, and 16 months old) and three wild‐type mice (4, 8, and 12 months old). Results: The result from FUS experiments showed a progressive increase in BBB permeability with increase of acoustic power (p <.05), demonstrating the sensitivity of DCE‐MRI method for detecting subtle changes in BBB disruption. Our AD transgenic mice experiments suggest an early BBB disruption in 5xFAD mice, which is further impaired with aging. Conclusion: The results in this study substantiate the feasibility of using the proposed 3D UTE‐GRASP method for detecting subtle BBB permeability changes expected in neurodegenerative diseases, such as AD. [ABSTRACT FROM AUTHOR]

INTRODUCTION: The rapid development of the space industry requires a deeper understanding of spaceflight's impact on the brain. MRI research reports brain volume changes following spaceflight in astronauts, potentially affecting cognition. Recently, we have demonstrated that this evidence of volumetric changes, as measured by typical T1-weighted sequences (e.g., magnetization-prepared rapid gradient echo sequence; MPRAGE), is error-prone due to the microgravity-related redistribution of cerebrospinal fluid in the brain. More modern neuroimaging methods, particularly dual-echo MPRAGE (DEMPRAGE) and magnetization-prepared rapid gradient echo sequence utilizing two inversion pulses (MP2RAGE), have been suggested to be resilient to this error. Here, we tested if these imaging modalities offered consistent segmentation performance improvements in some commonly employed neuroimaging software packages. METHODS: We conducted manual gray matter tissue segmentation in traditional T1w MRI images to utilize for comparison. Automated tissue segmentation was performed for traditional T1w imaging, as well as on DEMPRAGE and MP2RAGE images from the same subjects. Statistical analysis involved a comparison of total gray matter volumes for each modality, and the extent of tissue segmentation agreement was assessed using a test of similarity (Dice coefficient). RESULTS: Neither DEMPRAGE nor MP2RAGE exhibited consistent segmentation performance across all toolboxes tested. DISCUSSION: This research indicates that customized data collection and processing methods are necessary for reliable and valid structural MRI segmentation in astronauts, as current methods provide erroneous classification and hence inaccurate claims of neuroplastic brain changes in the astronaut population. [ABSTRACT FROM AUTHOR]

Oxygen extraction fraction (OEF), the fraction of oxygen that tissue extracts from blood, is an essential biomarker used to directly assess tissue viability and function in neurologic disorders. In ischemic stroke, for example, increased OEF can indicate the presence of penumbra—tissue with low perfusion yet intact cellular integrity—making it a primary therapeutic target. However, practical OEF mapping methods are not currently available in clinical settings, owing to the impractical data acquisitions in positron emission tomography (PET) and the limitations of existing MRI techniques. Recently, a novel MRI-based OEF mapping technique, termed QQ, was proposed. It shows high potential for clinical use by utilizing a routine sequence and removing the need for impractical multiple gas inhalations. However, QQ relies on the assumptions of Gaussian noise in susceptibility and multi-echo gradient echo (mGRE) magnitude signals for OEF estimation. This assumption is unreliable in low signal-to-noise ratio (SNR) regions like disease-related lesions, risking inaccurate OEF estimation and potentially impacting clinical decisions. Addressing this, our study presents a novel multi-echo complex QQ (mcQQ) that models realistic Gaussian noise in mGRE complex signals. We implemented mcQQ using a deep learning framework (mcQQ-NET) and compared it with the existing QQ-NET in simulations, ischemic stroke patients, and healthy subjects, using identical training and testing datasets and schemes. In simulations, mcQQ-NET provided more accurate OEF than QQ-NET. In the subacute stroke patients, mcQQ-NET showed a lower average OEF ratio in lesions relative to unaffected contralateral normal tissue than QQ-NET. In the healthy subjects, mcQQ-NET provided uniform OEF maps, similar to QQ-NET, but without unrealistically high OEF outliers in areas of low SNR, such as SNR ≤ 15 (dB). Therefore, mcQQ-NET improves OEF accuracy by more accurately reflecting realistic Gaussian noise in complex mGRE signals. Its enhanced sensitivity to OEF abnormalities, based on more realistic biophysics modeling, suggests that mcQQ-NET has potential for investigating tissue variability in neurologic disorders. [ABSTRACT FROM AUTHOR]

Objectives: CT is the clinical standard for surgical planning of craniofacial abnormalities in pediatric patients. This study evaluated three MRI cranial bone imaging techniques for their strengths and limitations as a radiation-free alternative to CT. Methods: Ten healthy adults were scanned at 3 T with three MRI sequences: dual-radiofrequency and dual-echo ultrashort echo time sequence (DURANDE), zero echo time (ZTE), and gradient-echo (GRE). DURANDE bright-bone images were generated by exploiting bone signal intensity dependence on RF pulse duration and echo time, while ZTE bright-bone images were obtained via logarithmic inversion. Three skull segmentations were derived, and the overlap of the binary masks was quantified using dice similarity coefficient. Craniometric distances were measured, and their agreement was quantified. Results: There was good overlap of the three masks and excellent agreement among craniometric distances. DURANDE and ZTE showed superior air-bone contrast (i.e., sinuses) and soft-tissue suppression compared to GRE. Discussions: ZTE has low levels of acoustic noise, however, ZTE images had lower contrast near facial bones (e.g., zygomatic) and require effective bias-field correction to separate bone from air and soft-tissue. DURANDE utilizes a dual-echo subtraction post-processing approach to yield bone-specific images, but the sequence is not currently manufacturer-supported and requires scanner-specific gradient-delay corrections. [ABSTRACT FROM AUTHOR]

Introduction: Quantification of longitudinal relaxation time T1 gained interest as an important MR-inducible tissue property for tissue characterization. Standard inversion recovery (IR) measurements for T1 determination take a prohibitively long time, and signal models assume a perfect inversion. Acceleration is possible by using the Look-Locker (LL) technique or other accelerated, model-based algorithms. However, the calculation of real T1 values from LL acquisitions necessitates the knowledge of equilibrium magnetization M0. Thus, usually, a waiting time to allow for free relaxation between global inversion pulses must be implemented. This study aims to introduce a novel model-based fitting approach for T1 mapping without the need for such waiting times. Methods: Single-inversion spiral LL spoiled gradient echo acquisitions were performed in a phantom and eight healthy volunteers using a 1.5T magnetic resonance imaging (MRI) scanner. The measurements comprised two parts, one without magnetization preparation and a second featuring a global inversion pulse preparation before each of the 35 slices. Acquisition was performed without any waiting time in between slices, i.e., before the inversion pulses. T1 maps were calculated based on an iterative model-based reconstruction algorithm which combines the information from these two measurements, with and without inversion. Results: Accurate T1 maps were obtained in phantom and volunteer measurements. ROI-based mean T1 values differ by an average of 1.5% in the phantom and 5% in vivo between reference measurements and the proposed method. The combined fit benefits from both the information obtained in the inversion prepared and the unprepared measurements. The former provides a large dynamic range for accurate model-based fitting of the relaxation process, while the latter provides equilibrium magnetization M0, necessary to obtain accurate T1 values from a LL-like acquisition. Conclusion: The proposed model of a combined fit of an inversion-prepared and an unprepared measurement allows for robust fast T1 mapping, even in cases of imperfect inversion due to skipped waiting times for magnetization recovery. Thus, it can render long waiting times in between inversion pulses redundant. [ABSTRACT FROM AUTHOR]

Background and purpose: Magnetic resonance imaging (MRI) measures of tissue microstructure are important for monitoring brain white matter (WM) disorders like leukodystrophies and multiple sclerosis. They should be sensitive to underlying pathological changes. Three whole‐brain isotropic quantitative methods were applied and compared within a cohort of controls and leukodystrophy patients: two novel myelin water imaging (MWI) techniques (multi‐compartment relaxometry diffusion‐informed MWI: MCR‐DIMWI, and multi‐echo T2 relaxation imaging with compressed sensing: METRICS) and neurite orientation dispersion and density imaging (NODDI). Methods: For 9 patients with different leukodystrophies (age range 0.4‐62.4 years) and 15 control subjects (2.3‐61.3 years), T1‐weighted MRI, fluid‐attenuated inversion recovery, multi‐echo gradient echo with variable flip angles, METRICS, and multi‐shell diffusion‐weighted imaging were acquired on 3 Tesla. MCR‐DIMWI, METRICS, NODDI, and quality control measures were extracted to evaluate differences between patients and controls in WM and deep gray matter (GM) regions of interest (ROIs). Pearson correlations, effect size calculations, and multi‐level analyses were performed. Results: MCR‐DIMWI and METRICS‐derived myelin water fractions (MWFs) were lower and relaxation times were higher in patients than in controls. Effect sizes of MWF values and relaxation times were large for both techniques. Differences between patients and controls were more pronounced in WM ROIs than in deep GM. MCR‐DIMWI‐MWFs were more homogeneous within ROIs and more bilaterally symmetrical than METRICS‐MWFs. The neurite density index was more sensitive in detecting differences between patients and controls than fractional anisotropy. Most measures obtained from MCR‐DIMWI, METRICS, NODDI, and diffusion tensor imaging correlated strongly with each other. Conclusion: This proof‐of‐concept study shows that MCR‐DIMWI, METRICS, and NODDI are sensitive techniques to detect changes in tissue microstructure in WM disorders. [ABSTRACT FROM AUTHOR]

To analyze cerebral arteriovenous pulse propagation and to generate phase-resolved pulse amplitude maps from a fast gradient-echo sequence offering flow-related enhancement (FREE). Brain MRI was performed using a balanced steady-state free precession sequence at 3T followed by retrospective k-space gating. The time interval of the pulse wave between anterior-, middle- and posterior cerebral artery territories and the superior sagittal sinus were calculated and compared between and older and younger groups within 24 healthy volunteers. Pulse amplitude maps were generated and compared to pseudo-Continuous Arterial Spin Labeling (pCASL) MRI maps by voxel-wise Pearson correlation, Sørensen-Dice maps and in regards to signal contrast. The arteriovenous delays between all vascular territories and the superior sagittal sinus were significantly shorter in the older age group (11 individuals, ≥ 31 years) ranging between 169 ± 112 and 246 ± 299 ms versus 286 ± 244 to 419 ± 299 ms in the younger age group (13 individuals) (P ≤ 0.04). The voxel-wise pulse wave amplitude values and perfusion-weighted pCASL values correlated significantly (Pearson-r = 0.33, P < 0.01). Mean Dice overlaps of high (gray) and low (white matter) regions were 73 ± 3% and 59 ± 5%. No differences in image contrast were seen in the whole brain and the white matter, but significantly higher mean contrast of 0.73 ± 0.23% in cortical gray matter in FREE-MRI compared to 0.52 ± 0.12% in pCASL-MRI (P = 0.01). The dynamic information of flow-related enhancement allows analysis of the cerebral pulse wave propagation potentially providing information about the (micro)circulation on a regional level. However, the pulse wave amplitude reveals weaknesses in comparison to true perfusion-weighting and could rather be used to calculate a pulsatility index. [ABSTRACT FROM AUTHOR]

In magnetic resonance imaging (MRI), it is necessary to reduce image distortion as much as possible because it suppresses the increase in the planning target volume. This study investigated the relationship between imaging parameters and image distortion when using G‐frames. The images were obtained using a 1.5‐T MRI system with a 09‐101 Pro‐MRI phantom. Image distortion was measured by changing the RF pulse mode, gradient mode, asymmetric echo, and bandwidth (BW). The image distortion was increased in the high RF mode than in the Normal mode. The image distortion increased in the following order: Whisper ≦ Normal < Fast in the different gradient modes. The image distortion increased in the following order: Without ≦ Weak < Strong in the different asymmetric echo modes. The image distortion increased in the following order: 300 Hz/pixel > 670 Hz/pixel ≧ REF (150 Hz/pixel) in the different Bw. The relationship between parameters and image distortion was clarified in this study when G‐frames were used for gamma knife therapy. There is had relationship between the parameters causing variation in the gradient magnetic field and image distortion. Therefore, these parameters should be adjusted to minimize distortion. [ABSTRACT FROM AUTHOR]

Mixed manganese–zinc ferrite nanoparticles coated with PEG were studied for their potential usefulness in MRI thermometry as temperature-sensitive contrast agents. Particles in the form of an 8.5 nm core coated with a 3.5 nm layer of PEG were fabricated using a newly developed, one-step method. The composition of Mn0.48Zn0.46Fe2.06O4 was found to have a strong thermal dependence of magnetization in the temperature range between 5 and 50 °C. Nanoparticles suspended in an agar gel mimicking animal tissue and showing non-significant impact on cell viability in the biological test were studied with NMR and MRI over the same temperature range. For the concentration of 0.017 mg/mL of Fe, the spin–spin relaxation time T2 increased from 3.1 to 8.3 ms, while longitudinal relaxation time T1 shows a moderate decrease from 149.0 to 125.1 ms. A temperature map of the phantom exposed to the radial temperature gradient obtained by heating it with an 808 nm laser was calculated from T2 weighted spin-echo differential MR images. Analysis of temperature maps yields thermal/spatial resolution of 3.2 °C at the distance of 2.9 mm. The experimental relaxation rate R2 data of water protons were compared with those obtained from calculations using a theoretical model incorporating the motion averaging regime. [ABSTRACT FROM AUTHOR]

Objective: To analyze the association of apparent diffusion coefficient (ADC) values measured by readout-segmented echo-planar imaging (rs-EPI) using different simultaneous multislice (SMS) acceleration factors and the differentiation of rectal cancer grade. Materials and methods: Patients with non-mucinous rectal adenocarcinoma diagnosed by biopsy (endoscope-guided biopsy or surgical resection) were retrospectively collected, and each patient underwent an MRI examination. ADC values of rs-EPI, 2 × SMS rs-EPI, and 3 × SMS rs-EPI were recorded as ADC1, ADC2, and ADC3, respectively. Results: The scanning time of 2 × SMS rs-EPI was 60 s, 56.2% shorter than 137 s of rs-EPI sequence, while that of 3 × SMS rs-EPI was 51 s, 72.8% less than that of rs-EPI time. The ADC value of the three groups dropped with the decrease in cancer grade (p < 0.05). The AUC values of ADC1, ADC2, and ADC3 in predicting highly differentiated rectal cancer were 0.74, 0.729, and 0.687, respectively. The difference in AUC values between ADC1 and ADC2 was not statistically significant (p = 0.889). Discussion: SMS technology with an acceleration factor of 2 could be applied clinically to evaluate the pathological differentiation of rectal cancer grade. [ABSTRACT FROM AUTHOR]

Receptor-enriched analysis of functional connectivity by targets (REACT) is a strategy to enrich functional MRI (fMRI) data with molecular information on the neurotransmitter distribution density in the human brain, providing a biological basis to the functional connectivity (FC) analysis. Although this approach has been used in BOLD fMRI studies only so far, extending its use to ASL imaging would provide many advantages, including the more direct link of ASL with neuronal activity compared to BOLD and its suitability for pharmacological MRI studies assessing drug effects on baseline brain function. Here, we applied REACT to simultaneous ASL/BOLD resting-state fMRI data of 29 healthy subjects and estimated the ASL and BOLD FC maps related to six molecular systems. We then compared the ASL and BOLD FC maps in terms of spatial similarity, and evaluated and compared the test–retest reproducibility of each modality. We found robust spatial patterns of molecular-enriched FC for both modalities, moderate similarity between BOLD and ASL FC maps and comparable reproducibility for all but one molecular-enriched functional networks. Our findings showed that ASL is as informative as BOLD in detecting functional circuits associated with specific molecular pathways, and that the two modalities may provide complementary information related to these circuits. [ABSTRACT FROM AUTHOR]

Differentiation of calcification and calcium-containing tissue from blood products remains challenging using magnetic resonance imaging (MRI). We developed a novel post-processing algorithm which creates both paramagnetic- and diamagnetic-specific SWI images generated from T2* weighted images using distinct "positive" and "negative" phase masks. 10 patients who had undergone clinical MRI scanning of the brain with a rapid echo planar based T2*-weighted EPI-GRE pulse sequence with evidence for either hemosiderin and/or calcifications were retrospectively identified. Complex raw k-space data from individual imaging coils were then extracted, reconstructed, and appropriately combined to produce magnitude and phase images using a phase preserving method. The final reconstructed images included the T2* EPI-GRE magnitude images, p-SWI and d-SWI images. Filtered phase images were also available for review. Correlation with CT scans and MR imaging appearance over time corroborated the composition of the voxels. Differential "blooming" of diamagnetic and paramagnetic foci was readily identified on the corresponding p-SWI and d-SWI images and provided fast and reliable visual differentiation of diamagnetic from paramagnetic susceptibility effects by ascertaining which of the two images depicted the greatest "blooming" effect. Correlation with the available filtered phase maps was not necessary for differentiation of paramagnetic from diamagnetic image components. Clinical interpretation of SWI images can be further enhanced by creating specific p-SWI and d-SWI image pairs which contain greater visual information than the combination of standard p-SWI images and phase image. [Display omitted] • New concept of individually reconstructed diamagnetic and paramagnetic specific SWI images: Current clinical/commercially available SWI post-processing algorithms only create images which enhance the paramagnetic component of susceptibility (e.g. p-SWI specific susceptibility weighted images). • In this work we separately reconstruct diamagnetic and paramagnetic susceptibility weight images (d-SWI, p-SWI) and use these to better discriminate hemosiderin from calcification. • The algorithm is described pictorially in the attached diagram. • The phase masks were applied exponentially to the magnitude image, with exponent of 4 for p-SWI and 5 for d-SWI. [ABSTRACT FROM AUTHOR]

To evaluate the diagnostic performance of a non-contrast magnetic resonance imaging (MRI) protocol combining high-resolution diffusion-weighted images (HR-DWI) using readout-segmented echo planar imaging, T1-weighted imaging (T1WI), and T2-weighted imaging (T2WI), using our modified Breast Imaging-Reporting and Data System (modified BI-RADS). Two experienced radiologists, blinded to the final pathological diagnosis, categorized a total of 108 breast lesions (61 malignant and 47 benign) acquired with the above protocol using the modified BI-RADS with a diagnostic decision tree. The decision tree included subcategories of category 4, as in mammography (categories 2, 3, 4A, 4B, 4C, and 5). These results were compared with the pathological diagnoses. The area under the ROC curve (AUC) was 0.89 (95% confidence interval [CI]: 0.83–0.95) for reader 1, and 0.89 (95% CI: 0.82–0.96) for reader 2. When categories 4C and above were classified as malignant, the sensitivity, specificity, and accuracy were 73.8%, 93.6%, and 82.4%, for reader 1; and 82.0%, 89.4%, and 85.2% for reader 2, respectively. Our results suggest that using HR-DWI, T1WI/T2WI analyzed with a modified BI-RADS and a decision tree showed promising diagnostic performance in breast lesions, and is worthy of further study. • HR-DWI enabled morphological evaluation of malignant lesions without contrast. • A modified BI-RADS MRI decision tree achieved promising diagnostic accuracy. • The area under the ROC curve for diagnosing malignancy was 0.89 for both readers. [ABSTRACT FROM AUTHOR]

Background: Paramagnetic species such as O2 and free radicals can enhance T1 and T2 relaxation times. If the change in relaxation time is sufficiently large, the contrast will be generated in magnetic resonance images. Since radiation is known to be capable of altering the concentration of O2 and free radicals during water radiolysis, it may be possible for radiation to induce MR signal change. Purpose: We present the first reported instance of x‐ray‐induced MR signal changes in water phantoms and investigate potential paramagnetic relaxation enhancement mechanisms associated with radiation chemistry changes in oxygen and free radical concentrations. Methods: Images of water and 10 mM coumarin phantoms were acquired on a 0.35 T MR‐linac before, during, and after a dose delivery of 80 Gy using an inversion‐recovery dual‐echo sequence with water nullified. Radiation chemistry simulations of these conditions were performed to calculate changes in oxygen and free radical concentrations. Published relaxivity values were then applied to calculate the resulting T1 change, and analytical MR signal equations were used to calculate the associated signal change. Results: Compared to pre‐irradiation reference images, water phantom images taken during and after irradiation showed little to no change, while coumarin phantom images showed a small signal loss in the irradiated region with a contrast‐to‐noise ratio (CNR) of 1.0–2.5. Radiation chemistry simulations found oxygen depletion of −11 µM in water and −31 µM in coumarin, resulting in a T1 lengthening of 24 ms and 68 ms respectively, and a simulated CNR of 1.0 and 2.8 respectively. This change was consistent with observations in both direction and magnitude. Steady‐state superoxide, hydroxyl, hydroperoxyl, and hydrogen radical concentrations were found to contribute less than 1 ms of T1 change. Conclusion: Observed radiation‐induced MR signal changes were dominated by an oxygen depletion mechanism. Free radicals were concluded to play a minor secondary role under steady‐state conditions. Future applications may include in vivo FLASH treatment verification but would require an MR sequence with a better signal‐to‐noise ratio and higher temporal resolution than the one used in this study. [ABSTRACT FROM AUTHOR]

Background: Quantitative magnetic resonance imaging provides robust biomarkers in clinics. Nevertheless, the lengthy scan time reduces imaging throughput and increases the susceptibility of imaging results to motion. In this context, a single‐shot T2 mapping method based on multiple overlapping‐echo detachment (MOLED) planar imaging was presented, but the relatively small echo time range limits its accuracy, especially in tissues with large T2. Purpose: In this work we proposed a novel single‐shot method, Multi‐Echo‐Train Multiple OverLapping‐Echo Detachment (METMOLED) planar imaging, to accommodate a large range of T2 quantification without additional measurements to rectify signal degeneration arisen from refocusing pulse imperfection. Methods: Multiple echo‐train techniques were integrated into the MOLED sequence to capture larger TE information. Maps of T2, B1, and spin density were reconstructed synchronously from acquired METMOLED data via multitask deep learning. A typical U‐Net was trained with 3000/600 synthetic data with geometric/brain patterns to learn the mapping relationship between METMOLED signals and quantitative maps. The refocusing pulse imperfection was settled through the inherent information of METMOLED data and auxiliary tasks. Results: Experimental results on the digital brain (structural similarity (SSIM) index = 0.975/0.991/0.988 for MOLED/METMOLED‐2/METMOLED‐3, hyphenated number denotes the number of echo‐trains), physical phantom (the slope of linear fitting with reference T2 map = 1.047/1.017/1.006 for MOLED/METMOLED‐2/METMOLED‐3), and human brain (Pearson's correlation coefficient (PCC) = 0.9581/0.9760/0.9900 for MOLED/METMOLED‐2/METMOLED‐3) demonstrated that the METMOLED improved the quantitative accuracy and the tissue details in contrast to the MOLED. These improvements were more pronounced in tissues with large T2 and in application scenarios with high temporal resolution (PCC = 0.8692/0.9465/0.9743 for MOLED/METMOLED‐2/METMOLED‐3). Moreover, the METMOLED could rectify the signal deviations induced by the non‐ideal slice profiles of refocusing pulses without additional measurements. A preliminary measurement also demonstrated that the METMOLED is highly repeatable (mean coefficient of variation (CV) = 1.65%). Conclusions: METMOLED breaks the restriction of echo‐train length to TE and implements unbiased T2 estimates in an extensive range. Furthermore, it corrects the effect of refocusing pulse inaccuracy without additional measurements or signal post‐processing, thus retaining its single‐shot characteristic. This technique would be beneficial for accurate T2 quantification. [ABSTRACT FROM AUTHOR]

17O and 14N are attractive targets for in vivo NMR spectroscopy and imaging, but low gyromagnetic ratios γ and fast spin relaxation complicate observations. This work explores indirect ways of detecting some of these sites with the help of proton‐detected double resonance techniques. As standard coherence transfer methods are of limited use for such indirect detection, alternative routes for probing the quadrupolar spectra on 1H were tested. These centered on modulating the broadening effects imparted onto protons adjacent to the low‐γ species through J couplings through either continuous wave or spin‐echo double‐resonance decoupling/recoupling sequences. As in all cases, the changes imparted by these double‐resonance strategies were small due to the fast relaxation undergone by the quadrupoles, the sensitivity of these approaches was amplified by transferring their effects onto the abundant water 1H signal. These amplifications were mediated by the spontaneous exchanges that the labile 1Hs bound to 17O or 14N undergo with the water protons. In experiments designed on the basis of double‐resonance spin echoes, these enhancements were imparted by looping the transverse encodings together with multiple longitudinal storage periods, leading to decoupling‐recoupling with exchange (D‐REX) sequences. In experiments designed on the basis of continuous on/off quadrupolar decoupling, these solvent exchanges were incorporated into chemical‐exchange saturation transfer schemes, leading to decoupling‐recoupling with saturation transfer (D‐REST) sequences. Both of these variants harnessed sizable proportions of the easily detectable water signals, in order to characterize the NMR spectra and/or to image with atomic‐site specificity the 17O and 14N species. [ABSTRACT FROM AUTHOR]

Objective. To develop a novel, free-induction-decay (FID)-calibrated single-shot simultaneous multi-slice fast spin echo (SMS-FSE) with very long hard pulse trains for high encoding efficiency and low energy deposition. Approach. The proposed single-shot SMS-FSE employs a mixed pulse configuration in which a long excitation pulse that is spatially multi-band (MB) selective is used in conjunction with short spatially nonselective refocusing pulses. To alleviate energy deposition to tissues while reducing signal modulation along the echo train, variable low flip angles with signal prescription are utilized in the refocusing pulse train. A time-efficient FID calibration and correction method is introduced before aliased voxels in the slice direction are resolved. Simulations and experiments are performed to demonstrate the feasibility of the proposed method as an alternative to conventional HASTE for generating T 2-weighted images. Main results. Compared with conventional HASTE, the proposed method enhances imaging speed effectively by an MB factor up to 5 without apparent loss of image contrast while successfully eliminating FID artifacts. Significance. We successfully demonstrated the feasibility of the proposed method as an encoding- and energy-efficient alternative to conventional HASTE for generation of T 2-weighted contrast. [ABSTRACT FROM AUTHOR]

Objectives: A novel magnetic resonance imaging (MRI) scan protocol is presented on the basis of ultra-short time to echo (UTE). By this MRI cephalometric projections (MCPs) can be acquired without the need of post processing in one shot. Different technical parameterizations of the protocol are performed. Their impact on the performance of MCPs is evaluated in comparison to the gold standard–the lateral cephalometric radiography (LCR) for cephalometric analysis (CA) in orthodontics. Methods: Seven MCPs with various scan parameters influencing the scan duration and one LCR are used from one subject. 40 expert assessors performed CA for 14 predefined cephalometric landmarks. Relative metric distances and absolute angular measurements were calculated. Statistical analysis is presented and the deviations are highlighted to demonstrate the potential of the method for further analysis. Results: The MCPs are acquired in 5–154 seconds, depending on resolution and contrast. Mean relative distances were 2.4–2.7 mm in MCPs and 1.6 mm in LCR, which demonstrate the accuracy and level of agreement of the expert assessors in identifying anatomical landmarks. In comparison to other studies, the presented MCP performed similar in angular analysis and demonstrated on average deviation of 1.2° ±1.1° in comparison to LCR. Despite the point articulare (Ar) and the related gonial angle the calculate distances and angles show outcomes in the range of ±2°/2mm. Conclusions: MCPs can be acquired much faster in comparison to other techniques known from literature for CA. This study demonstrated the potential of the new method and showed first feasible results. Further research is needed to analyze the performance on a broad range of patients. [ABSTRACT FROM AUTHOR]

: The principle of fast spin echo ( FSE ) producing stimulated echo and the relationship between stimulated echo and the phase angle of radio frequency pulse were investigated. For fast spin echo pulse sequence, a stimulated echo artifact correction method was proposed. The spin echo and stimulated echo were separated by two times of excitations, then the area of dispersion gradient was adjusted to make the center of stimulated echo coincide with that of the spin echo, and the phase angle of 180° refocusing pulse was modified to make the phase of stimulated echo and spin echo consistent. The correction method was tested and validated on a 1. 5 T superconducting MRI scanner. After stimulated echo artifact was corrected, the signal to noise ratio of the FSE image was improved by 57. 08%, while the image artifact was reduced by 76. 12% . The experimental results showed that the proposed method can effectively suppress stimulated echo artifacts on FSE image and improve the image quality. [ABSTRACT FROM AUTHOR]

Purpose: To determine the feasibility of ultra-short echo time (UTE) MRA for assessment of inferior vena cava (IVC) filters and evaluate the impact of different imaging protocols at 3.0 T, using conventional Cartesian MRA (cMRA) as the reference standard. Methods: Patients with IVC-filters were recruited for this prospective IRB-approved, HIPAA-compliant study. Subjects underwent contrast-enhanced breath-held and a free-breathing 3D radial acquisition UTE-MRA (bhUTE, fbUTE) at three different flip angles (FA: 10°, 15°, 20°) to optimize T1-weighted image quality. Two radiologists performed a direct comparison consensus reading to assess the optimal FA. Image quality (IQ) of both UTE techniques at the best FA was rated independently on a 4-point Likert scale (0 = non-diagnostic, 3 = excellent) and compared to 3D T1-weighted breath-held cMRA. Results: Nine subjects were recruited. Low FAs of 10° were rated best for both UTE techniques. fbUTE was excellent (3, IQR: 2; 3) and significantly better for IVC-filter depiction than cMRA (2, IQR: 0.75; 2, p = 0.001) and bhUTE (1.5, IQR: 0.75; 2, p < 0.001). Both UTE techniques showed significantly less filter-related artifacts (fbUTE: 28%, bhUTE: 33%) than cMRA (89%, p = 0.001 and p = 0.002, respectively). However, IQ of bhUTE was generally degraded due to high image noise and low image contrast. IQ of the IVC venogram was best with cMRA. Clinically relevant signal voids were only observed with the cage-shaped OptEase filter. Conclusion: UTE-MRA is feasible at 3.0 T for the assessment of IVC-filters, particularly using a free-breathing protocol. Larger studies are needed to investigate the clinical utility of free-breathing UTE-MRA for assessment of IVC-filter-related complications. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate a 3D registration approach by which double echo steady state (DESS) MR images with cartilage thickness segmentations are used to extract the cartilage transverse relaxation time (T2) from multi-echo-spin-echo (MESE) MR images, without direct segmentations for MESE. Materials and methods: Manual DESS segmentations of 89 healthy reference knees (healthy) and 60 knees with early radiographic osteoarthritis (early ROA) from the Osteoarthritis Initiative were registered to corresponding MESE images that had independent direct T2 segmentations. For validation purposes, (a) regression analysis of deep and superficial cartilage T2 was performed and (b) between-group differences between healthy vs. early ROA knees were compared for registered vs. direct MESE analysis. Results: Moderate to high correlations were observed for the deep (r = 0.80) and the superficial T2 (r = 0.81), with statistically significant between-group differences (ROA vs. healthy) of + 1.4 ms (p = 0.002) vs. + 1.3 ms (p < 0.001) for registered vs. direct T2 segmentation in the deep, and + 1.3 ms (p = 0.002) vs. + 2.3 ms (p < 0.001) in the superficial layer. Discussion: This registration approach enables extracting cartilage T2 from MESE scans using DESS (cartilage thickness) segmentations, avoiding the need for direct MESE T2 segmentations. [ABSTRACT FROM AUTHOR]

Background: The image quality of abdominal magnetic resonance imaging (MRI) in children who cannot hold their breath has been severely impaired by motion artifacts.Purpose: To evaluate the usefulness of T1-weighted (T1W) BLADE MRI for axial abdominal imaging in children who cannot hold their breath.Material and Methods: Two different BLADE sequences, with and without an inversion recovery (IR-BLADE), were compared to conventional turbo-spin echo (TSE) with a high number of excitations in 18 consecutive patients who cannot hold their breath. Overall image quality, motion artifact, radial artifact, hepatic vessel sharpness, renal corticomedullary differentiation, and lesion conspicuity were retrospectively assessed by two radiologists, using 4- or 5-point scoring systems. Signal variations of each sequence were measured for a quantitative comparison. The acquisition times of the three sequences were compared.Results: IR-BLADE and BLADE showed significantly improved overall image quality and reduced motion artifact compared with TSE. IR-BLADE showed significantly better hepatic vessel sharpness and corticomedullary differentiation compared to both BLADE and TSE. Radial artifacts were only observed on IR-BLADE and BLADE. In nine patients with lesions, there were no significant differences in lesion conspicuity among three sequences. Compared to TSE, both IR-BLADE and BLADE showed decreased signal variations in the liver and muscle, and an increased signal variation through air. The mean acquisition times for IR-BLADE, BLADE, and TSE were comparable.Conclusion: Compared to the TSE sequence, T1W IR-BLADE for pediatric abdominal MRI resulted in improved image quality, tissue contrast with a diminished respiratory motion artifact, and a comparable acquisition time. [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]

Bone is comprised of mineral, collagenous organic matrix, and water. X-ray-based techniques are the standard approach for bone evaluation in clinics, but they are unable to detect the organic matrix and water components in bone. Magnetic resonance imaging (MRI) is being used increasingly for bone evaluation. While MRI can non-invasively assess the proton pools in soft tissues, cortical bone typically appears as a signal void with clinical MR techniques because of its short T2*. New MRI techniques have been recently developed to image bone while avoiding the ionizing radiation present in x-ray-based methods. Qualitative bone imaging can be achieved using ultrashort echo time (UTE), single inversion recovery UTE (IR-UTE), dual-inversion recovery UTE (Dual-IR-UTE), double-inversion recovery UTE (Double-IR-UTE), and zero echo time (ZTE) sequences. The contrast mechanisms as well as the advantages and disadvantages of each technique are discussed. [ABSTRACT FROM AUTHOR]

Introduction: Cerebral Microbleeds (CMBs) are increasingly recognised as an important predictor of small vessel disease and cannot be detected on routine Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) sequences. Aim: This study was aimed at evaluating CMBs on MRI and to compare the sensitivity of SWI and T2* GRE sequences in detection of these microbleeds. In addition, we also sought to evaluate association between topography (size, number and location) of CMBs and various risk factors. Materials and Methods: This Prospective observational analytical study comprised of 67 patients with CMBs who were evaluated with Siemens 1.5 Tesla MRI machine. T2*-weighted gradient recalled echo sequence and Susceptibility-Weighted Imaging (SWI) were taken in all the patients in addition to routine MRI sequences. Two observers blinded to clinical information, independently interpreted the T2*GRE and SWI sequences. Both observers recorded the topographical details of CMBs which included presence, number, size and location and their association with various risk factors (hypertension, diabetes, smoking and hyperlipidemia). Inter-rater agreement for the number of CMBs on SWI and on T2*GRE was calculated using Cohen’s Kappa (κ) as measure of agreement. Intra-Class Correlation Coefficient (ICC) for reliability index in test-retest, intra-rater and interrater reliability was also analysed. The intra-rater reliabilities of each rater were compared. The Correlations between CMBs and risk factors was performed with Pearson’s correlation Coefficient (r). The p-value <0.05 was considered statistically significant. Results: The SWI with its Reverse Phase (RP) detected more number of CMBs as compared to T2*GRE. Majority of the subjects (71.6%) had more than 5 CMBs. CMBs ≥5 mm had a strong correlation with both hypertension and diabetes as compared to CMBs <5 mm. There was a higher frequency of patients with lobar CMBs (89.6%) followed by the deep location (70.1%). An almost perfect agreement was found between both observers for number of CMBs on RP SWI with ‘κ’ value of 0.97a (0.96-0.98) in contrast to a weak agreement on RP T2*GRE with κ=0.52a (0.40-0.64). For SWI, an almost perfect reliability was found (ICC=0.998) as compared to a moderate reliability on T2*GRE (ICC=0.6826). An excellent reliability was seen for size of CMBs <5 mm on RP SWI (ICC 0.998). Conclusion: SWI offered greater reliability and sensitivity for CMB detection as compared to the T2*GRE sequence and is presently the gold standard sequence of MRI for quantifying CMBs. The burden of CMBs may further indicate inappropriately treated hypertension and diabetes. [ABSTRACT FROM AUTHOR]

Background: Although magnetic resonance imaging (MRI) provides excellent soft-tissue contrast, long acquisition times are major disadvantages. Purpose: To evaluate the usefulness of compressed sensing (CS) for contrast-enhanced oral and maxillofacial MRI by comparing the 3D T1 turbo field echo with compressed SENSE (CS-3D-T1TFE) sequence with the multi-slice spin echo (MS-SE) sequence as the reference standard. Material and Methods: Thirty patients with orofacial lesions participated in this study. The scan times for MS-SE and CS-3D-T1TFE were 5 min 56 s and 1 min 43 s, respectively. The signal-to-noise ratio (SNR) was calculated for quantitative analysis and seven parameters (degree of lesion conspicuity, motion artifacts, metal artifacts, pulsation artifacts, quality of fat suppression, homogeneity of blood vessel signal intensity, and overall image quality) were evaluated using a 5-point scale (5 = excellent, 1 = unacceptable) by two observers for qualitative analysis. For comparisons between MS-SE and CS-3D-T1TFE, the paired t-test was used. Results: The SNR of CS-3D-T1TFE was higher than or equal to that of MS-SE. The CS-3D-T1TFE scores for motion artifacts, pulsation artifacts, and homogeneity of blood vessel signal intensity were higher than the corresponding MS-SE scores in assessments by both observers. The MS-SE scores for fat suppression were higher than or equal to the CS-3D-T1TFE scores. There were no significant differences in lesion conspicuity, metal artifacts, and overall image quality between the two sequences. Conclusion: CS-3D-T1TFE imaging, less than 30% of the scan time for MS-SE, showed no image degradation while retaining equal or higher SNR and image quality. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the feasibility and image quality of respiratory motion-resolved 4D zero echo time (ZTE) lung MRI compared with that of 3D ZTE.Methods: Our institutional review board approved this study. Twenty-one patients underwent lung scans using 3D ZTE and 4D ZTE sequences via prospective and retrospective soft gating techniques, respectively. Image qualities of 3D ZTE and 4D ZTE at end-expiration were compared through objective and subjective assessments. The quality of end-expiratory images of 3D ZTE and 4D ZTE of the two groups with different lung functions was also compared.Results: Images were successfully acquired in all patients without any adverse events. Signal-to-noise ratios (SNRs) of lung parenchyma and thoracic structures were significantly (all p < 0.001) higher in 4D ZTE. Contrast-to-noise ratios (CNRs) of peripheral bronchi, peripheral pulmonary vessels, and nodules or masses were significantly (all p < 0.001) higher in 4D ZTE. The subjective image quality assessed by two independent radiologists showed that intrapulmonary structures, noise and artifacts, and overall acceptability were superior in 4D ZTE (all p < 0.001). Image qualities of groups with normal and low lung functions differed significantly (all p < 0.05) in 3D ZTE, but not in 4D ZTE. The mean acquisition time was 136 s (127-143 s) in 3D ZTE and 325 s (308-352 s) in 4D ZTE.Conclusions: Respiratory motion-resolved 4D ZTE lung imaging was feasible as part of routine chest MRI. The 4D ZTE provides motion-robust lung parenchymal images with better SNR and CNR than the 3D ZTE, regardless of patients' lung function.Key Points: • ZTE MRI captures rapidly decaying transverse magnetization in the lung parenchyma. • 4D ZTE provides motion-robust lung parenchymal images with better SNR and CNR compared with 3D ZTE. • Compared with 3D ZTE, the image quality of 4D ZTE lung MRI was affected less by patients' lung function and respiratory performance. [ABSTRACT FROM AUTHOR]

The purpose of our study was to use Dual-TR STE-MR protocol as a clinical tool for cortical bone free water quantification at 1.5 T and validate it by comparing the obtained results (MR-derived results) with dehydration results. Human studies were compliant with HIPPA and were approved by the institutional review board. Short Echo Time (STE) MR imaging with different Repetition Times (TRs) was used for quantification of cortical bone free water T 1 (T 1 free) and concentration (ρ free). The proposed strategy was compared with the dehydration technique in seven bovine cortical bone samples. The agreement between the two methods was quantified by using Bland and Altman analysis. Then we applied the technique on a cross-sectional population of thirty healthy volunteers (18F/12M) and examined the association of the biomarkers with age. The mean values of ρ free for bovine cortical bone specimens were quantified as 4.37% and 5.34% by using STE-MR and dehydration techniques, respectively. The Bland and Altman analysis showed good agreement between the two methods along with the suggestion of 0.99% bias between them. Strong correlations were also reported between ρ free (r2 = 0.62) and T 1free and age (r2 = 0.8). The reproducibility of the method, evaluated in eight subjects, yielded an intra-class correlation of 0.95. STE-MR imaging with dual-TR strategy is a clinical solution for quantifying cortical bone ρ free and T 1free. [ABSTRACT FROM AUTHOR]

Background: Quantitative MRI of patellar tendinopathy (PT) can be challenging due to spatial variation of T2 * relaxation times.Purpose: 1) To compare T2 * quantification using a standard approach with analysis in specific tissue compartments of the patellar tendon. 2) To evaluate test-retest reliability of different methods for fitting ultrashort echo time (UTE)-relaxometry data.Study Type: Prospective.Subjects: Sixty-five athletes with PT.Field Strength/sequence: 3D UTE scans covering the patellar tendon were acquired using a 3.0T scanner and a 16-channel surface coil.Assessment: Voxelwise median T2 * was quantified with monoexponential, fractional-order, and biexponential fitting. We applied two methods for T2 * analysis: first, a standard approach by analyzing all voxels covering the proximal patellar tendon. Second, within subregions of the patellar tendon, by using thresholds on biexponential fitting parameter percentage short T2 * (0-30% for mostly long T2 *, 30-60% for mixed T2 *, and 60-100% for mostly short T2 *).Statistical Tests: Average test-retest reliability was assessed in three athletes using coefficients-of-variation (CV) and coefficients-of-repeatability (CR).Results: With standard image analysis, we found a median [interquartile range, IQR] monoexponential T2 * of 6.43 msec [4.32-8.55] and fractional order T2 * 4.39 msec [3.06-5.78]. The percentage of short T2 * components was 52.9% [35.5-69.6]. Subregional monoexponential T2 * was 13.78 msec [12.11-16.46], 7.65 msec [6.49-8.61], and 3.05 msec [2.52-3.60] and fractional order T2 * 11.82 msec [10.09-14.44], 5.14 msec [4.25-5.96], and 2.19 msec [1.82-2.64] for 0-30%, 30-60%, and 60-100% short T2 *, respectively. Biexponential component short T2 * was 1.693 msec [1.417-2.003] for tissue with mostly short T2 * and long T2 * of 15.79 msec [13.47-18.61] for mostly long T2 *. The average CR (CV) was 2 msec (15%), 2 msec (19%) and 10% (22%) for monoexponential, fractional order and percentage short T2 *, respectively.Data Conclusion: Patellar tendinopathy is characterized by regional variability in binding states of water. Quantitative multicompartment T2 * analysis in PT can be facilitated using a voxel selection method based on using biexponential fitting parameters.Level Of Evidence: 1 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:420-430. [ABSTRACT FROM AUTHOR]

Purpose: Transverse relaxation time (T2) mapping with MRI has a plethora of clinical and research applications. Current T2 mapping techniques are based primarily on spin‐echo (SE) relaxometry strategies that rely on the signal magnitude, and often suffer from lengthy acquisition times. In this work, we propose a phase‐based T2 mapping technique where T2 information is encoded into the signal phase of rapid gradient echo (GRE) acquisitions. Theory: Bloch equation simulations demonstrate that the phase of GRE acquisitions obtained with a very small inter‐repetition RF phase increment has a strong monotonic dependence on T2, resulting from coherent transverse magnetization. This T2‐dependent phase behavior forms the basis of the proposed T2 mapping technique. To isolate T2‐dependent phase from background phase, at least 2 data sets with different RF phase increments are acquired. The proposed method can also be combined with chemical shift encoded MRI to separate water and fat signals. Methods: The feasibility of the proposed technique was validated in a phantom experiment. In vivo feasibility was demonstrated in the brain, knee, abdomen, and pelvis. Comparisons were made with SE‐based T2 mapping, spectroscopy, and T2 values from the literature. Results: The proposed method produced accurate T2 maps compared with SE‐based T2 mapping in the phantom. Good qualitative agreement was observed in vivo between the proposed method and the reference. T2 measured in various anatomies agreed well with values reported in the literature. Conclusion: A phase‐based T2 mapping technique was developed and its feasibility demonstrated in phantoms and in vivo. [ABSTRACT FROM AUTHOR]

Background: Short T2 tissues can be directly visualized by dual-echo ultrashort echo time imaging with weighted subtraction. As a type of post-processing method, exponential subtraction of ultrashort echo time images with an optimal exponential factor is expected to provide improved positive short T2 contrast.Purpose: To test the feasibility and effectiveness of exponential subtraction in three-dimensional ultrashort echo time imaging and to determine the optimal exponential factor.Material and Methods: A dual-echo three-dimensional ultrashort echo time sequence was implemented on a 3-T MRI system. Exponential subtraction was performed on dual three-dimensional ultrashort echo time images of the tibia of seven healthy volunteers with exponential factors in the range of 1.00-3.00 in increments of 0.01. The regions of interest, including cortical bone, marrow, and muscle, were depicted on subtracted images of different exponential factors. Contrast-to-noise ratio values were calculated from these regions of interest and then used to assess the optimal exponential factor. To determine intra-observer agreement regarding region of interest selection, paired intra-observer measurements of regions of interest in all direct subtraction images were conducted with a one-week interval and the paired measurements were assessed using Bland-Altman analysis and paired-samples t-test.Results: Cortical bone can be better visualized by using exponential subtraction in three-dimensional ultrashort echo time imaging; the suggested optimal exponential factor is 1.99-2.03 in the tibia. Paired measurements showed excellent intra-observer agreement.Conclusion: It is feasible to visualize cortical bone of the tibia using exponential subtraction in three-dimensional ultrashort echo time imaging. Compared with weighted subtraction images, exponential subtraction images with an optimal exponential factor provide enhanced visualization of short T2 tissues. [ABSTRACT FROM AUTHOR]

To investigate the correlations between cortical bone microstructural properties and total water proton density (TWPD) obtained from three-dimensional ultrashort echo time Cones (3D-UTE-Cones) magnetic resonance imaging techniques. 135 cortical bone samples were harvested from human tibial and femoral midshafts of 37 donors (61 ± 24 years old). Samples were scanned using 3D-UTE-Cones sequences on a clinical 3T MRI and on a high-resolution micro-computed tomography (μCT) scanner. TWPD was measured using 3D-UTE-Cones MR images. Average bone porosity, pore size, and bone mineral density (BMD) were measured from μCT images at 9 μm voxel size. Pearson's correlation coefficients between TWPD and μCT-based measures were calculated. TWPD showed significant moderate correlation with both average bone porosity (R = 0.66, p < 0.01) and pore size (R = 0.57, p < 0.01). TWPD also showed significant strong correction with BMD (R = 0.71, p < 0.01). The presented 3D-UTE-Cones imaging technique allows assessment of TWPD in human cortical bone. This quick UTE-MRI-based technique was capable of predicting bone microstructure differences with significant correlations. Such correlations highlight the potential of UTE-MRI-based measurement of bone water proton density to assess bone microstructure. [ABSTRACT FROM AUTHOR]

[Display omitted] • Systematic study of core plugs with 3D Fast Spin Echo, and 3D SPRITE MRI methods. • A variable field superconducting magnet was used at: 0.79 T, 1.5 T, and 3 T. • FSE quantitative imaging employed to estimate local porosity in core plugs. • 3D SPRITE measurements of fluid saturation is recommended for core analysis. • 3 T is too high a static field in general for rock core MRI studies. Fast Spin Echo MRI is now widely employed in biomedicine for proton density and T 2 contrast imaging. Fast Spin Echo methods provide rapid data acquisition by employing multiple echoes to determine multiple k-space lines with single excitations. Due to the multi-exponential behavior of T 2 in typical porous media, and the strong dependence of T 2 on the details of the experiment, acquiring a proton density image with Fast Spin Echo methods requires favorable sample and acquisition parameters. In recent years, we have shown the value of pure phase encode Free Induction Decay based methods such as SPRITE. However, in a reservoir rock, a typical T 2 * is hundreds of µs, whereas a typical T 2 is hundreds of ms. Hence, there is merit in considering spin echo-based MRI measurements such as the Fast Spin Echo for rock core plug studies. A variable field superconducting magnet was employed in this study. This is a new class of magnet for MR/MRI. These magnets have the flexibility of operation in the field range of 0.01 Tesla to 3 Tesla. This is advantageous when working with rock core plugs, as it allows one to maximize sample magnetization, by increasing the static field while controlling magnetic susceptibility mismatch effects, and thereby T 2 and T 2 * , through reducing the static field. The magnetic fields employed in the study were 0.79, 1.5, and 3 Tesla. Measurements were undertaken on five brine-saturated reservoir rock core plugs (Bentheimer, Berea, Buff Berea, Nugget, and Wallace). The results show that Fast Spin Echo measurements are more sensitive than SPRITE methods in amenable samples and usually feature higher resolution. Quantification of saturation with Fast Spin Echo methods requires correction for T 2 attenuation. The results also show that 3 Tesla is too high a static field in general for rock core MRI studies with either method. While the current study is focused on five representative reservoir rock cores, the conclusions which result are general for MRI of fluids in porous media. [ABSTRACT FROM AUTHOR]

Ultrashort echo time imaging on clinical systems is still limited by the rather long radio frequency switching times achievable with standard front end concepts. In this contribution, an independent parallel receive-only system is interfaced to an unmodified clinical MRI system, enabling imaging of species with ultrashort relaxation times, such as bone, tendon, teeth, or lung tissue. Synchronization of the system is achieved by an electronically decoupled one-way trigger line, a clock reference signal, and RF pulse tracking, thus ensuring minimal interference with the host system. With the proposed system, an acquisition delay of 3 μs is experimentally demonstrated. [ABSTRACT FROM AUTHOR]

Introduction: Three-dimensional (3D) T1-weighted imaging (T1WI) is used for evaluation of the facial nerve. The signal intensity of normal and pathological facial nerves has been well evaluated at both 1.5T and 3.0T MRI after gadolinium (Gd)-enhancement with various pulse sequences. However, the continuity of the facial nerve has not been evaluated on 3D-T1WI. This study aims to compare the continuity of the normal facial nerve in the temporal bone demonstrated on T1-weighted volume isotropic turbo spin echo acquisition (T1-VISTA), which is a spin-echo sequence, to that on T1-weighted fast field echo (T1-FFE), which is a gradient-echo sequence, at 3.0T MRI.Methods: Forty-four normal facial nerves in 22 healthy volunteers were imaged with both sequences using 3.0T MRI without Gd-enhancement. The facial nerves were evaluated visually by two neuroradiologists in four anatomical segments with a 3-point grading system of continuity. The continuity was assessed by summing the grades of the four segments as a total score. The grades at each segment and the total scores were compared statistically between the T1-VISTA and T1-FFE.Results: The grades in all segments and the total score were significantly higher with T1-VISTA than those with T1-FFE.Conclusions: T1-VISTA was superior to demonstrate the facial nerve as a continuous anatomical structure in the temporal bone at 3.0T MRI. [ABSTRACT FROM AUTHOR]

Objective: Purely exponential decay is rarely observed in conventional mono-exponential T2 mapping due to transmit field inhomogeneity and calibration errors, which collectively introduce stimulated and indirect echo pathways. Stimulated echo correction (SEC) requires an additional fit parameter for the transmit field, resulting in greater uncertainty in T2 relative to mono-exponential fitting. The aim of this study was to develop an accurate and precise method for T2 mapping using SEC. Methods: The proposed method, called two-step SEC (tSEC), leverages spatial correlations in the transmit field to reduce the number of fully independent fitting parameters from three to two. The method involves a two-pass fit: the first pass involves a fast but standard SEC fit. The initially estimated transmit field is smoothed and provided as a fixed input to the second pass. Results: Simulations and in vivo experiments demonstrated up to 38% and 27% decreases in relative T2 variance with tSEC relative to SEC. Average T2 values were unchanged between tSEC and SEC fits. The proposed method uses the same input data as SEC and exponential fits, so it is applicable to existing data. Discussion: The proposed method generates reliable and reproducible quantitative T2 maps and should be considered for future relaxometry studies. [ABSTRACT FROM AUTHOR]

Magnetic Resonance Imaging (MRI) has become a valuable imaging modality in ophthalmology, especially for the diagnosis and treatment planning of patients with uveal melanoma, the most common primary intra-ocular tumor. We aim to develop and evaluate the value of silent Zero Echo Time (ZTE) MRI to image patients with ocular tumors at 7Tesla. Therefore, ZTE and different types of magnetization-prepared ZTE (FLAIR, SPIR, T2 and Saturation recovery), have been developed. After an initial validation with 7 healthy subjects, nine patients with an eye tumor have been evaluated. The ZTE scans were compared to their Cartesian equivalent in terms of contrast, motion-sensitivity, diagnostic quality and patient comfort. All volunteers and especially the patients reported a more comfortable experience during the ZTE scans, which had at least a 10 dB lower sound pressure. The image contrast in the native ZTE was poor, but in the different magnetization-prepared ZTE, the eye lens, cornea and retina were clearly discriminated. Overall the T2-prepared scan yielded the best contrast, especially between tumor and healthy tissue, and proved to be robust against eye motion. Although the intrinsic 3D nature of the ZTE-technique provides an accurate analysis of the tumor morphology, the quality of the ZTE-images is lower than their Cartesian equivalent. In conclusion, the quality of magnetization-prepared ZTE images is sufficient to assess the 3D tumor morphology, but insufficient for more detailed evaluations. As such this technique can be an option for patients who cannot comply with the sound-levels of Cartesian scans, but for other patients the conventional Cartesian scans offer a better image quality. [ABSTRACT FROM AUTHOR]

Introduction: This research was motivated by the increase of brain MRI examinations in emergency medicine. In an emergency, patients are often uncooperative, and they raise motion artefact on the image. Therefore, fast scanning techniques such as pulse Sequence Single Shot Fast Spin Echo (SS-FSE) is required to reduce the artefact. This study was conducted to determine the effectiveness of using SS-FSE technique to minimize motion artefact. Methods: This study was an observational analytic with prospective methods. Scanning was conducted to 16 normal patients (volunteers). Two neuro radiologists retrospectively and independently reviewed all images. Observations used standard diagnostic of brain MR Image by evaluating the anatomical and morphological structure. Results: Based on the results of the analysis of each organ that was assessed, it was obtained that the average of the image for overall organs on the brain; 76% looks sharp, 21% looks moderate (minimum blurred), and 3% looks blurred. Conclusion: SS-FSE technique affects reducing motion artefact due to object movement in MRI brain. The overall image SS-FSE produced has good image quality. [ABSTRACT FROM AUTHOR]

To develop an accelerated Cartesian MRF implementation using a multi-shot EPI sequence for rapid simultaneous quantification of T1 and T2 parameters. The proposed Cartesian MRF method involved the acquisition of highly subsampled MR images using a 16-shot EPI readout. A linearly varying flip angle train was used for rapid, simultaneous T1 and T2 quantification. The results were compared to a conventional spiral MRF implementation. The acquisition time per slice was 8s and this method was validated on two different phantoms and three healthy volunteer brains in vivo. Joint T1 and T2 estimations using the 16-shot EPI readout are in good agreement with the spiral implementation using the same acquisition parameters (<4% deviation for T1 and <6% deviation for T2). The T1 and T2 values also agree with the conventional values previously reported in the literature. The visual qualities of fine brain structures in the multi-parametric maps generated by multi-shot EPI-MRF and Spiral-MRF implementations were comparable. The multi-shot EPI-MRF method generated accurate quantitative multi-parametric maps similar to conventional Spiral-MRF. This multi-shot approach achieved considerable k-space subsampling and comparatively short TRs in a similar manner to spirals and therefore provides an alternative for performing MRF using an accelerated Cartesian readout; thereby increasing the potential usability of MRF. [ABSTRACT FROM AUTHOR]

Purpose: To perform and evaluate water–fat signal separation of whole‐body gradient echo scans using convolutional neural networks. Methods: Whole‐body gradient echo scans of 240 subjects, each consisting of 5 bipolar echoes, were used. Reference fat fraction maps were created using a conventional method. Convolutional neural networks, more specifically 2D U‐nets, were trained using 5‐fold cross‐validation with 1 or several echoes as input, using the squared difference between the output and the reference fat fraction maps as the loss function. The outputs of the networks were assessed by the loss function, measured liver fat fractions, and visually. Training was performed using a graphics processing unit (GPU). Inference was performed using the GPU as well as a central processing unit (CPU). Results: The loss curves indicated convergence, and the final loss of the validation data decreased when using more echoes as input. The liver fat fractions could be estimated using only 1 echo, but results were improved by use of more echoes. Visual assessment found the quality of the outputs of the networks to be similar to the reference even when using only 1 echo, with slight improvements when using more echoes. Training a network took at most 28.6 h. Inference time of a whole‐body scan took at most 3.7 s using the GPU and 5.8 min using the CPU. Conclusion: It is possible to perform water–fat signal separation of whole‐body gradient echo scans using convolutional neural networks. Separation was possible using only 1 echo, although using more echoes improved the results. [ABSTRACT FROM AUTHOR]

Background: Due to the very short T2 of its components, the normal anatomy of Achilles enthesis is impossible to define with "conventional" long echo time (TE) T2 sequences. However, this is a common site affected by rheumatologic disease. Early abnormalities related to inflammatory processes are impossible to detect in this location.Purpose: To assess the feasibility of a 3D-UTE (ultrashort echo time) sequence to evaluate normal and pathological Achilles entheses, determining both anterior fibrocartilaginous and posterior collagenic portions at 4.7T, in a rat model of spondyloarthropathy (SpA) with histological correlation. To assess whether this sequence detects SpA enthesopathy prior to long TE T2 sequences, enabling disease monitoring.Study Type: Prospective case-control study.Animal Model: Twelve immunocompetent Wistar male rats imaged before (controls); the model was induced in eight rats (16 tendons) imaged at day 6, day 13, and day 21 with regular sacrifice for ex vivo imaging and histological correlation.Field Strength: 4.7T Bruker Biospec Systems. 3D balanced steady-state free precession (bSSFP) and 3D-UTE sequences, performed at baseline (day 0, n = 12 animals / 24 tendons), day 6 (n = 8/16), 13 (n = 4/8), and day 21 (n = 2/4).Assessment: Visual analysis and signal intensity measurements (signal to noise ratio, SNR) of both bSSFP and UTE images were performed by two independent musculoskeletal radiologists at different locations of the Achilles enthesis and preinsertional area.Statistical Tests: Normal and pathological rat values were compared by Wilcoxon signed-rank tests, as well as interobserver differences. MRI findings were compared against histological data.Results: The 3D-UTE sequence identified the anterior fibrocartilage and posterior collagenic areas of Achilles entheses in all cases. Visual analysis and signal intensity measurements distinguished SpA-affected entheses from healthy ones at days 6 and 13 (P = 0.002 and P = 0.006, respectively). Neither the normal anatomy of the enthesis nor its pathological pattern could be identified on T2 bSSFP sequences.Data Conclusion: Unlike bSSFP T2 sequences, 3D-UTE sequences enable visualization of normal enthesis anatomy and early detection of abnormalities in pathological conditions.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:127-135. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance imaging (MRI) assessment for appendicitis is limited by exam time and patient cooperation. The radially sampled 3-dimensional (3-D) T1-weighted, gradient recalled echo sequence (radial GRE) is a free-breathing, motion robust sequence that may be useful in evaluating appendicitis in children.Objective: To compare the rate of detection of the normal appendix with contrast-enhanced radial GRE versus contrast-enhanced 3-D GRE and a multi-sequence study including contrast-enhanced radial GRE.Materials and Methods: This was a retrospective study of patients ages 7-18 years undergoing abdominal-pelvic contrast-enhanced MRI between Jan. 1, 2012, and April 1, 2016. Visualization of the appendix was assessed by consensus between two pediatric radiologists. The rate of detection of the appendix for each sequence and combination of sequences was compared using a McNemar test.Results: The rate of detection of the normal appendix on contrast-enhanced radial GRE was significantly higher than on contrast-enhanced 3-D GRE (76% vs. 57.3%, P=0.003). The rate of detection of the normal appendix with multi-sequence MRI including contrast-enhanced radial GRE was significantly higher than on contrast-enhanced 3-D GRE (81.3% vs. 57%, P<0.001). There was no significant difference between the rate of detection of the normal appendix on contrast-enhanced radial GRE alone and multi-sequence MRI including contrast-enhanced radial GRE (76% vs. 81.3%, P=0.267).Conclusion: Contrast-enhanced radial GRE allows superior detection of the normal appendix compared to contrast-enhanced 3-D GRE. The rate of detection of the normal appendix on contrast-enhanced radial GRE alone is nearly as good as when the contrast-enhanced radial GRE is interpreted with additional sequences. [ABSTRACT FROM AUTHOR]

Background: Two-point modified Dixon (mDixon) turbo spin-echo (TSE) sequence provides an efficient, robust method of fat suppression. In one mDixon acquisition, four image types can be generated: water-only, fat-only, in-phase and opposed-phase images.Objective: To determine whether PD mDixon TSE water-only and, by proxy, PD in-phase images generated by one acquisition can replace two conventional PD TSE sequences with and without fat suppression in routine clinical MR examination of the knee.Materials and Methods: This is a retrospective study of 50 consecutive pediatric knee MR examinations. PD mDixon TSE water-only and PD fat-saturated TSE sequences (acquired in the sagittal plane with identical spatial resolution) were reviewed independently by two pediatric radiologists for homogeneity of fat suppression and detection of intra-articular pathology. Thirteen of the 50 patients underwent arthroscopy, and we used the arthroscopic results as a reference standard for the proton-density fat-saturated and proton-density mDixon results. We used the Kruskal-Wallis rank test to assess difference in fat suppression between the proton-density mDixon and proton-density fat-saturated techniques. We used kappa statistics to compare the agreement of detection of intra-articular pathology between readers and techniques. We also calculated sensitivity, specificity and accuracy between arthroscopy and MR interpretations.Results: Proton-density mDixon water-only imaging showed significant improvement with the fat suppression compared with proton-density fat-saturated sequence (P=0.02). Each observer demonstrated near-perfect agreement between both techniques for detecting meniscal and ligamentous pathology and fair to substantial agreement for bone contusions, and chondral and osteochondral lesions.Conclusion: Two-point mDixon water-only imaging can replace conventional proton-density fat-saturated sequence. When same-plane proton-density fat-saturated and non-fat-saturated sequences are required, proton-density water-only and proton-density in-phase image types acquired in the same acquisition shorten the overall examination time while maintaining excellent intra-articular lesion conspicuity. [ABSTRACT FROM AUTHOR]

Objective: To determine the feasibility of using high-resolution volumetric zero echo time (ZTE) sequence in routine lung magnetic resonance imaging (MRI) and compare free breathing 3D ultrashort echo time (UTE) and ZTE lung MRI in terms of image quality and small-nodule detection.Materials and Methods: Our Institutional Review Board approved this study. Twenty patients underwent both UTE and ZTE sequences during routine lung MR. UTE and ZTE images were compared in terms of subjective image quality and detection of lung parenchymal signal, intrapulmonary structures, and sub-centimeter nodules. Differences between the two sequences were compared through statistical analysis.Results: Lung parenchyma showed significantly (p < 0.05) higher signal-to-noise ratio (SNR) in ZTE than in UTE. The SNR and contrast-to-noise ratio (CNR) of peripheral bronchus and small pulmonary arteries were significantly (all p < 0.05) higher in ZTE. Subjective image quality evaluated by two independent radiologists in terms of depicting normal structures and overall acceptability was superior in ZTE (p < 0.05). The diagnostic accuracy for sub-centimeter nodules was significantly higher for ZTE (reader 1: AUC, 0.972; p = 0.044; reader 2: AUC, 0.946; p = 0.045) than that for UTE (reader 1: AUC, 0.885; reader 2: AUC, 0.855). Mean scan time was 131 s (125-141 s) in ZTE and 467 s (453-508 s) in UTE. ZTE images were obtained with less acoustic noise.Conclusion: Implementing ZTE as an additional sequence in routine lung MR is feasible. ZTE can provide high-resolution pulmonary structural information with better SNR and CNR using shorter time than UTE.Key Points: • Both UTE and ZTE techniques use very short TEs to capture signals from very short T2/T2* tissues. • ZTE is superior in capturing lung parenchymal signal than UTE. • ZTE provides high-resolution structural information with better SNR and CNR for normal intrapulmonary structures and small nodules using shorter scan time than UTE. [ABSTRACT FROM AUTHOR]

Purpose of this work was to assess feasibility of cardiac diffusion tensor imaging (cDTI) at 7 T in a set of healthy, unfixed, porcine hearts using various parallel imaging acceleration factors and to compare SNR and derived cDTI metrics to a reference measured at 3 T. Magnetic resonance imaging was performed on 7T and 3T whole body systems using a spin echo diffusion encoding sequence with echo planar imaging readout. Five reference (b = 0 s/mm2) images and 30 diffusion directions (b = 700 s/mm2) were acquired at both 7 T and 3 T using a GRAPPA acceleration factor R = 1. Scans at 7 T were repeated using R = 2, R = 3, and R = 4. SNR evaluation was based on 30 reference (b = 0 s/mm2) images of 30 slices of the left ventricle and cardiac DTI metrics were compared within AHA segmentation. The number of hearts scanned at 7 T and 3 T was n = 11. No statistically significant differences were found for evaluated helix angle, secondary eigenvector angle, fractional anisotropy and apparent diffusion coefficient at the different field strengths, given sufficiently high SNR and geometrically undistorted images. R≥3 was needed to reduce susceptibility induced geometric distortions to an acceptable amount. On average SNR in myocardium of the left ventricle was increased from 29±3 to 44±6 in the reference image (b = 0 s/mm2) when switching from 3 T to 7 T. Our study demonstrates that high resolution, ex vivo cDTI is feasible at 7 T using commercial hardware. [ABSTRACT FROM AUTHOR]

[Display omitted] • MR microscopy with spin-echo (SE) and its DEFT variant (DE-SE) was compared. • The signal dependence on RF pulse flip angles and on diffusion was studied. • DE-SE was found considerably more sensitive to flip angle deviations than SE. • Diffusion signal attenuation in MR microscopy with DE-SE may be significant. • The water signal ratio between DE-SE and SE images was 10:1 with short TRs. Rapid MR imaging of slowly relaxing samples is often challenging. The most commonly used solutions are found in multi spin-echo (RARE) sequences or gradient-echo (GE) sequences, which allow faster imaging of such samples with multiple acquisitions of k -space lines per excitation or imaging with very short repetition times (TR s). Another solution is the use of a spin-echo (SE) sequence superimposed with a driven equilibrium Fourier transform (DEFT) method. Such a (DE-SE) imaging sequence has two refocusing RF pulses that produce two spin-echoes. In the first echo, the signal is acquired from the k -space line, and in the second echo, a 90° RF pulse is applied, typically 180° out of phase with respect to the excitation RF pulse. This last RF pulse allows almost complete magnetization reversal back to the longitudinal orientation with minimal magnetization loss. The DE-SE sequence and its RARE variant are widely used in clinical imaging, but its use in MR microscopy has some peculiarities related to the usually less perfect RF pulse flip angles and diffusion. In this study, their effects are first theoretically analyzed and later verified by experiments on test samples performed on a 9.4 T system for MR microscopy. Experiments on a water-filled tube for TE = 3.4 ms and TR = 25–200 ms showed that the DE-SE sequence produces about 10 times more signal than the SE sequence in this TR range. Finally, the performance of the DE-SE sequence compared to the SE sequence was demonstrated on a biological sample. The presented DE-SE sequence has been shown to be effective for rapid imaging of samples with long T 1 relaxation times in MR microscopy and can also be considered as a suitable method for rapid proton density weighed imaging of materials. [ABSTRACT FROM AUTHOR]