A major limitation of the commonly used clinical MRI contrast agents (CAs) suitable at lower magnetic field strengths (<3.0 T) is their inefficiency at higher fields (>7 T), where next-generation MRI scanners are going. We present dysprosium nanoparticles (β-NaDyF4 NPs) as T2 CAs suitable at ultrahigh fields (9.4 T). These NPs effectively enhance T2 contrast at 9.4 T, which is 10-fold higher than the clinically used T2 CA (Resovist). Evaluation of the relaxivities at 3 and 9.4 T show that the T2 contrast enhances with an increase in NP size and field strength. Specifically, the transverse relaxivity (r2) values at 9.4 T were ∼64 times higher per NP (20.3 nm) and ∼6 times higher per Dy(3+) ion compared to that at 3 T, which is attributed to the Curie spin relaxation mechanism. These results and confirming phantom MR images demonstrate their effectiveness as T2 CAs in ultrahigh field MRIs.

The purpose of the current thesis was twofold: (1) to examine various factors that might be contributing to age-related learning and memory deficits specifically related to the hippocampus, and (2) to validate our rat model of aging, employing a multilevel analysis. We found age-related deficits on both spatial and non-spatial hippocampus-dependent tasks that were accompanied by structural alterations observed both in vivo (volume, but not neuronal metabolic function) and post mortem (neuronal density and neurogenesis, but not synaptic or mitochondrial density). Furthermore, our results suggest that the observed hippocampal structural changes, namely decreased volume and neurogenesis, predict learning and memory deficits, and both can be accounted for by neurogenic reduction. In addition, the above-mentioned pattern of age-related deficits closely resembles that seen in humans, suggesting the present rat version of aging to be a very useful model for investigating hippocampal aging in humans.

MR images can be interpreted to measure tissue parameters correlated with cellulite. Considering that we had only three subjects in each group, the achievements of this pilot study were highly satisfactory. We have shown that the in vivo micro-MR is a technique able to detect the effects of cellulite and gender. This study can be extended for further investigations of drugs and/or medical devices for cellulite treatment.

The purpose was to determine if in vivo proton magnetic resonance spectroscopy ((1)H MRS) at 1.5 T can accurately provide the correct pathology of breast disease. Forty-three asymptomatic volunteers including three lactating mothers were examined and compared with 21 breast cancer patients. Examinations were undertaken at 1.5 T using a purpose-built transmit-receive single breast coil. Single voxel spectroscopy was undertaken using echo times of 135 and 350 ms. The broad composite resonance at 3.2 ppm, which includes contributions from choline, phosphocholine (PC), glycerophosphocholine (GPC), myo-inositol and taurine, was found not to be a unique marker for malignancy providing a diagnostic sensitivity and specificity of 80.0 and 86.0%, respectively. This was due to three of the asymptomatic volunteers and all of the lactating mothers also generating the broad composite resonance at 3.2 ppm. Optimised post-acquisitional processing of the spectra resolved a resonance at 3.22 ppm, consistent with PC, in patients with cancer. In contrast the spectra recorded for three false-positive volunteers, and the three lactating mothers had a resonance centred at 3.28 ppm (possibly taurine, myo-inositol or GPC). This improved the specificity of the test to 100%. Careful referencing of the spectra and post-acquisitional processing intended to optimise spectral resolution of in vivo MR proton spectra from human breast tissue resolves the composite choline resonance. This allows the distinction of patients with malignant disease from volunteers with a sensitivity of 80% and specificity of 100%. Therefore, resolution of the composite choline resonance into its constituent components improves the specificity of the in vivo (1)H MRS method, but does not overcome the problem of 20% false-negatives.

No abstract

Cation exchange was performed on up-conversion NaYF4:Yb,Tm nanoparticles, resulting in NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles as indicated by electron energy-loss spectroscopy 2D mapping. Results show that core–shell nanoparticles with a thin, tunable, and uniform shell of subnanometer thickness can be made via this cation exchange process. The resulting NaYF4:Yb,Tm-NaGdF4 core–shell nanoparticles have an enhanced up-conversion intensity relative to the initial core nanoparticles. As potential magnetic resonance imaging (MRI) contrast agents, they were tested for their proton relaxivities. The r1 relaxivity per Gd3+ ion of the nanoparticles with a thin NaGdF4 shell (ca. 0.6 nm thick) measured at 9.4 T was found to be 2.33 mM–1·s–1. This r1 relaxivity is among the highest in all the reported NaYF4–NaGdF4 core–shell nanoparticles. The r1 relaxivity per nanoparticle is 1.56 × 104 mM–1·s–1, which is over 4000 times higher than commercial Gd3+-complexes. The very high proton relaxivity per nanoparticle is critical for targeted MRI as such nanoparticles provide strong contrast even in low concentrations. The presented cation exchange method is a promising way to manufacture core–shell nanoparticles with up-conversion NaYF4:Yb,Tm core and paramagnetic NaGdF4 shell for bimodal imaging, i.e. MR and optical imaging.

riers R, Arora RC, Tian G. Adipose-derived stem cells are an effective cell candidate for treatment of heart failure: an MR imaging study of rat hearts.

Study design: A magnetic resonance imaging technique that enables indirect detection of neuronal activity has been developed for the spinal cord. In the present study, this method, spinal functional magnetic resonance imaging (fMRI), is applied to the first study of the injured spinal cord, with the goal of better clinical assessment of the entire cord. Objectives: The objectives of this project are: (1) to investigate the neuronal activity that can be detected in the spinal cord caudal to a chronic injury by means of spinal fMRI, and (2) to develop spinal fMRI as a clinical diagnostic tool. Setting: Institute for Biodiagnostics, National Research Council of Canada, Winnipeg, Manitoba, Canada. Methods: fMRI of the spinal cord was carried out in 27 volunteers with cervical or thoracic spinal cord injuries (SCIs). Of these volunteers, 18 had complete injuries, and nine had incomplete injuries. Spinal fMRI was carried out in a 1.5 T clinical MR system, using established methods. Thermal stimulation at 101C was applied to the fourth lumbar dermatome on each leg, and images were obtained of the entire lumbar spinal cord. Results: Areas of neuronal activity were consistently observed in the lumbar spinal cord in response to the thermal stimulation, even when the subjects had no awareness of the sensation. The pattern of activity was notably different compared with noninjured subjects. In general, subjects with complete SCI showed absent or diminished dorsal gray matter activity, but had enhanced ventral activity, particularly contralateral to the stimulation. Conclusions: Spinal fMRI is able to provide a noninvasive assessment of the injured spinal cord that does not depend on the patient's perception of the stimulus being applied. This work was carried out on a standard clinical MRI system without modification, and so is readily applicable in most MR units.