MR fingerprinting (MRF) is a versatile method for rapid multi-parametric quantification. The application of MRF for lower MRI field could enable multi-contrast imaging and improve exam efficiency on ...these systems. The purpose of this work is to demonstrate the feasibility of 3D whole-brain T1 and T2 mapping using MR fingerprinting on a contemporary 0.55 T MRI system.
A 3D whole brain stack-of-spirals FISP MRF sequence was implemented for 0.55 T. Quantification was validated using the NIST/ISMRM Quantitative MRI phantom, and T1 and T2 values of white matter, gray matter, and cerebrospinal fluid were measured in 19 healthy subjects. To assess MRF performance in the lower SNR regime of 0.55 T, measurement precision was calculated from 100 simulated pseudo-replicas of in vivo data and within-session measurement repeatability was evaluated.
T1 and T2 values calculated by MRF were strongly correlated to standard measurements in the ISMRM/NIST MRI system phantom (R2 > 0.99), with a small constant bias of approximately 5 ms in T2 values. 3D stack-of-spirals MRF was successfully applied for whole brain quantitative T1 and T2 at 0.55 T, with spatial resolution of 1.2 mm × 1.2 mm × 5 mm, and acquisition time of 8.5 min. Moreover, the T1 and T2 quantifications had precision <5%, despite the lower SNR of 0.55 T.
A 3D whole-brain stack-of-spirals FISP MRF sequence is feasible for T1 and T2 mapping at 0.55 T.
While nanoparticles maximize the amount of chemotherapeutic drug in tumors relative to normal tissues, nanoparticle-based drugs are not accessible to the majority of cancer cells because ...nanoparticles display patchy, near-perivascular accumulation in tumors. To overcome the limitations of current drugs in their molecular or nanoparticle form, we developed a nanoparticle based on multicomponent nanochains to deliver drug to the majority of cancer cells throughout a tumor while reducing off-target delivery. The nanoparticle is composed of three magnetic nanospheres and one doxorubicin-loaded liposome assembled in a 100 nm long chain. These nanoparticles display prolonged blood circulation and significant intratumoral deposition in tumor models in rodents. Furthermore, the magnetic particles of the chains serve as a mechanical transducer to transfer radio frequency energy to the drug-loaded liposome. The defects on the liposomal walls trigger the release of free drug capable of spreading throughout the entire tumor, which results in a widespread anticancer effect.
To propose a new reconstruction method for multidimensional MR fingerprinting (mdMRF) to address shading artifacts caused by physiological motion-induced measurement errors without navigating or ...gating.
The proposed method comprises two procedures: self-calibration and subspace reconstruction. The first procedure (self-calibration) applies temporally local matrix completion to reconstruct low-resolution images from a subset of under-sampled data extracted from the k-space center. The second procedure (subspace reconstruction) utilizes temporally global subspace reconstruction with pre-estimated temporal subspace from low-resolution images to reconstruct aliasing-free, high-resolution, and time-resolved images. After reconstruction, a customized outlier detection algorithm was employed to automatically detect and remove images corrupted by measurement errors. Feasibility, robustness, and scan efficiency were evaluated through in vivo human brain imaging experiments.
The proposed method successfully reconstructed aliasing-free, high-resolution, and time-resolved images, where the measurement errors were accurately represented. The corrupted images were automatically and robustly detected and removed. Artifact-free T1, T2, and ADC maps were generated simultaneously. The proposed reconstruction method demonstrated robustness across different scanners, parameter settings, and subjects. A high scan efficiency of less than 20 s per slice has been achieved.
The proposed reconstruction method can effectively alleviate shading artifacts caused by physiological motion-induced measurement errors. It enables simultaneous and artifact-free quantification of T1, T2, and ADC using mdMRF scans without prospective gating, with robustness and high scan efficiency.
Glioblastoma multiforme is generally recalcitrant to current surgical and local radiotherapeutic approaches. Moreover, systemic chemotherapeutic approaches are impeded by the blood-tumor barrier. To ...circumvent limitations in the latter area, we developed a multicomponent, chain-like nanoparticle that can penetrate brain tumors, composed of three iron oxide nanospheres and one drug-loaded liposome linked chemically into a linear chain-like assembly. Unlike traditional small-molecule drugs or spherical nanotherapeutics, this oblong-shaped, flexible nanochain particle possessed a unique ability to gain access to and accumulate at glioma sites. Vascular targeting of nanochains to the αvβ3 integrin receptor resulted in a 18.6-fold greater drug dose administered to brain tumors than standard chemotherapy. By 2 hours after injection, when nanochains had exited the blood stream and docked at vascular beds in the brain, the application of an external low-power radiofrequency field was sufficient to remotely trigger rapid drug release. This effect was produced by mechanically induced defects in the liposomal membrane caused by the oscillation of the iron oxide portion of the nanochain. In vivo efficacy studies conducted in two different mouse orthotopic models of glioblastoma illustrated how enhanced targeting by the nanochain facilitates widespread site-specific drug delivery. Our findings offer preclinical proof-of-concept for a broadly improved method for glioblastoma treatment.
Purpose
Quantitative MRI techniques such as MR fingerprinting (MRF) promise more objective and comparable measurements of tissue properties at the point‐of‐care than weighted imaging. However, few ...direct cross‐modal comparisons of MRF's repeatability and reproducibility versus weighted acquisitions have been performed. This work proposes a novel fully automated pipeline for quantitatively comparing cross‐modal imaging performance in vivo via atlas‐based sampling.
Methods
We acquire whole‐brain 3D‐MRF, turbo spin echo, and MPRAGE sequences three times each on two scanners across 10 subjects, for a total of 60 multimodal datasets. The proposed automated registration and analysis pipeline uses linear and nonlinear registration to align all qualitative and quantitative DICOM stacks to Montreal Neurological Institute (MNI) 152 space, then samples each dataset's native space through transformation inversion to compare performance within atlas regions across subjects, scanners, and repetitions.
Results
Voxel values within MRF‐derived maps were found to be more repeatable (σT1 = 1.90, σT2 = 3.20) across sessions than vendor‐reconstructed MPRAGE (σT1w = 6.04) or turbo spin echo (σT2w = 5.66) images. Additionally, MRF was found to be more reproducible across scanners (σT1 = 2.21, σT2 = 3.89) than either qualitative modality (σT1w = 7.84, σT2w = 7.76). Notably, differences between repeatability and reproducibility of in vivo MRF were insignificant, unlike the weighted images.
Conclusion
MRF data from many sessions and scanners can potentially be treated as a single dataset for harmonized analysis or longitudinal comparisons without the additional regularization steps needed for qualitative modalities.
•MR Fingerprinting provides T1 and T2 quantification of the prostatic parenchyma.•Comprehensive ROIs were used to assess T1 and T2 values of the peripheral zone.•Mean T1 and T2 values were 1941 and ...88 ms for the whole peripheral zone.•Average peripheral zone thickness was correlated with mean T1 and T2 values.•Our data may serve as reference for diagnostics and tissue characterization studies.
To quantify and assess the distribution of MR fingerprinting (MRF)-derived T1 and T2 values of the whole prostatic peripheral zone (PZ), and perform subgroup analyses according to clinical and demographic features.
One hundred and twenty-four patients with prostate MR exams and MRF-based T1 and T2 maps of the prostatic apex, mid gland, and base were identified from our database and included. Regions of interest encompassing the right and left lobes of the PZ were drawn for each axial slice on the T2 map and copied to the T1 map. Clinical data were obtained from medical records. Kruskal-Wallis test was used for assessing differences between subgroups and the Spearman coefficient was used for assessing any correlations.
Mean T1 and T2 values were 1941 and 88 ms, respectively, for the whole-gland, 1884 and 83 ms for the apex, 1974 and 92 ms for the mid-gland, 1966 and 88 ms for the base. T1 values were weakly negatively correlated with PSA values, while T1 and T2 values were weakly positively correlated with prostate weight and moderately positively correlated with PZ width. Finally, patients with PI-RADS 1 scores had higher T1 and T2 values of the whole PZ, compared with those with scores 2–5.
Mean T1 and T2 values of the background PZ of the whole gland were 1941 ± 313 and 88 ± 39 ms, respectively. Among clinical and demographic factors, there was a significant positive correlation between T1 and T2 values and PZ width.
Objectives: The extent of medical knowledge increases yearly, but the time available for students to learn is limited, leading to administrative pressures to revise and reconfigure medical school ...curricula. The goal of the present study is to determine whether the mixed reality platform HoloAnatomy represents an effective and time-efficient modality to learn anatomy when compared to traditional cadaveric dissection.
Methods: This was a prospective, longitudinal study of medical students completing a musculoskeletal anatomy course at Case Western Reserve University School of Medicine. Participants were divided into two groups based on learning platform (HoloAnatomy versus traditional cadaveric dissection) and content area (upper limb versus lower limb anatomy). Time spent in lab and end of course practical exam scores were compared between groups.
Results: The average study time of 48 medical students who completed study requirements was 4.564 h using HoloAnatomy and 7.318 h in the cadaver lab (p = 0.001). No significant difference was found between exam scores for HoloAnatomy and cadaver learners (p = 0.185).
Conclusions: Our results indicate that HoloAnatomy may decrease the time necessary for anatomy didactics without sacrificing student understanding of the material.
Magnetic resonance fingerprinting (MRF) is a method to extract quantitative tissue properties such as Formula: see text and Formula: see text relaxation rates from arbitrary pulse sequences using ...conventional MRI hardware. MRF pulse sequences have thousands of tunable parameters, which can be chosen to maximize precision and minimize scan time. Here, we perform de novo automated design of MRF pulse sequences by applying physics-inspired optimization heuristics. Our experimental data suggest that systematic errors dominate over random errors in MRF scans under clinically relevant conditions of high undersampling. Thus, in contrast to prior optimization efforts, which focused on statistical error models, we use a cost function based on explicit first-principles simulation of systematic errors arising from Fourier undersampling and phase variation. The resulting pulse sequences display features qualitatively different from previously used MRF pulse sequences and achieve fourfold shorter scan time than prior human-designed sequences of equivalent precision in Formula: see text and Formula: see text Furthermore, the optimization algorithm has discovered the existence of MRF pulse sequences with intrinsic robustness against shading artifacts due to phase variation.
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