41 research outputs found
Fat suppression for coronary MR angiography at 3T: 2 point Dixon versus Spectral Presaturation with Inversion Recovery (SPIR)
Assessment of the grey zone: a comparison of two methods in heart failure patients awaiting cardiac resynchronization therapy
Phosphorothioate antisense oligonucleotides induce the formation of nuclear bodies
Antisense oligonucleotides are powerful tools for the in vivo regulation of gene expression. We have characterized the intracellular distribution of fluorescently tagged phosphorothioate oligodeoxynucleotides (PS-ONs) at high resolution under conditions in which PS-ONs have the potential to display antisense activity. Under these conditions PS-ONs predominantly localized to the cell nucleus where they accumulated in 20-30 bright spherical foci designated phosphorothioate bodies (PS bodies), which were set against a diffuse nucleoplasmic population excluding nucleoli. PS bodies are nuclear structures that formed in cells after PS-ON delivery by transfection agents or microinjection but were observed irrespectively of antisense activity or sequence. Ultrastructurally, PS bodies corresponded to electron-dense structures of 150-300 nm diameter and resembled nuclear bodies that were found with lower frequency in cells lacking PS-ONs. The environment of a living cell was required for the de novo formation of PS bodies, which occurred within minutes after the introduction of PS-ONs. PS bodies were stable entities that underwent noticeable reorganization only during mitosis. Upon exit from mitosis, PS bodies were assembled de novo from diffuse PS-ON pools in the daughter nuclei. In situ fractionation demonstrated an association of PS-ONs with the nuclear matrix. Taken together, our data provide evidence for the formation of a nuclear body in cells after introduction of phosphorothioate oligodeoxynucleotides
Fat suppression for coronary MR angiography at 3T: 2 point Dixon versus Spectral Presaturation with Inversion Recovery (SPIR)
Fast multi-component analysis using a joint sparsity constraint for MR fingerprinting
PurposeTo develop an efficient algorithm for multiācomponent analysis of magnetic resonance fingerprinting (MRF) data without making a priori assumptions about the exact number of tissues or their relaxation properties.MethodsDifferent tissues or components within a voxel are potentially separable in MRF because of their distinct signal evolutions. The observed signal evolution in each voxel can be described as a linear combination of the signals for each component with a nonānegative weight. An assumption that only a small number of components are present in the measured field of view is usually imposed in the interpretation of multiācomponent data. In this work, a joint sparsity constraint is introduced to utilize this additional prior knowledge in the multiācomponent analysis of MRF data. A new algorithm combining joint sparsity and nonānegativity constraints is proposed and compared to stateāofātheāart multiācomponent MRF approaches in simulations and brain MRF scans of 11 healthy volunteers.ResultsSimulations and in vivo measurements show reduced noise in the estimated tissue fraction maps compared to previously proposed methods. Applying the proposed algorithm to the brain data resulted in 4 or 5 components, which could be attributed to different brain structures, consistent with previous multiācomponent MRF publications.ConclusionsThe proposed algorithm is faster than previously proposed methods for multiācomponent MRF and the simulations suggest improved accuracy and precision of the estimated weights. The results are easier to interpret compared to voxelāwise methods, which combined with the improved speed is an important step toward clinical evaluation of multiācomponent MRF.ImPhys/Quantitative Imagin