Biomedical subjects

D D Blatter

Publications and source records attributed to D D Blatter.

42 records · Page 3Linked to original sources

PubMedDate not supplied

Accuracy of phase-contrast flow measurements in the presence of partial-volume effects.

The accuracy of volume flow rate measurements obtained with phase-contrast methods was assessed by means of computer simulation and in vitro experiments. Factors studied include (a) the partial-volume effect due to voxel dimensions relative to vessel dimensions and orientation and (b) intravoxel phase dispersion. It is shown that limited resolution (partial-volume effect) is the major obstacle to accurate flow measurement for both laminar and plug flow. The results show that at least 16 voxels must cover the cross section of the vessel lumen to obtain a measurement accuracy to within 10%. Measurement accuracy also greatly depends on the relative signal intensity of stationary tissue and is better for laminar flow than plug flow.

Biophysical Phenomena↗

PubMedDate not supplied

Reduction of slab boundary artifact with multiple overlapping thin slab acquisition in MR angiography of the cervical carotid artery.

Multiple overlapping thin slab acquisition (MOTSA) is a magnetic resonance (MR) angiography technique combining advantages of two- and three-dimensional time-of-flight techniques. The authors studied three image acquisition parameters (flip angle, TR, and the slab excitation fraction [SEF]) and a postprocessing algorithm, to evaluate their effect on MOTSA image quality, including contrast-to-noise ratio (C/N) and the severity of the slab boundary artifact. By increasing SEF from 0.75 to 1.10, the slab boundary artifact was reduced by 29%-56% (P < .0001). The boundary artifact can be reduced an additional 46% by postprocessing of the overlapping section data. In the healthy volunteers studied, C/N of the cervical carotid artery could be increased sixfold (P < .0001) by increasing the flip angle from 10 degrees to 50 degrees, without significant worsening of the boundary artifact due to top-of-slab saturation. The effect of TR on image quality was not statistically significant for the range studied (52-70 msec). We conclude that the slab boundary artifact seen with the MOTSA MR angiography technique can be reduced significantly by optimizing imaging acquisition parameters and using a postprocessing algorithm to combine overlapping section information.

Adult↗

PubMedDate not supplied

Correction of partial-volume effects in phase-contrast flow measurements.

Because of the relatively small size of vessels and limited magnetic resonance (MR) imaging resolution, the accuracy of volume flow rate measurements is limited. A technique that corrects the partial-volume effect in volume flow rate measurements is presented. The technique uses small-phase-shift approximation, with the assumption that blood flow in the voxels at the boundary of the vessel is slow. With the proposed correction technique, the volume flow rate in partially occupied voxels is corrected on a voxel-by-voxel basis and the accuracy of flow measurements increases. Results are shown analytically and for MR phantom data.

Artifacts↗

PubMedDate not supplied

The effect of image resolution on vessel signal in high-resolution magnetic resonance angiography.

In this paper, the theoretical dependence of the signal of flowing fluids is considered in terms of the imaging parameters and the physical condition of the flowing fluid. For the vessel sizes, flow ranges, and imaging conditions studied, it is demonstrated that the fluid signal can be predicted from the solution of Bloch equations. For vessels on the order of the imaging resolution or smaller, the effects of the image resolution must be included

Algorithms↗

PubMedDate not supplied

Neuropsychological outcome and quantitative image analysis of acute haemorrhage in traumatic brain injury: preliminary findings.

The effect on neuropsychological outcome of the number of acute haemorrhages, lesion volume, and lesion location in traumatic brain injury (TBI) was evaluated. Haemorrhagic lesion volume was associated with severity of injury. However, the number of petechial haemorrhages was not reliably associated with any of the clinical outcome measures. Likewise, despite the use of detailed morphometric methods to quantify volume, the acute lesion size did not significantly relate to neuropsychological sequelae. Furthermore, brain quadrant localization methods did not enhance outcome prediction. These results are discussed in the context of acute lesion analysis contrasted with chronic TBI-induced neuropathological changes associated with neuropsychological outcome.

Adolescent↗

PubMedDate not supplied

Fat suppression in combination with multiple overlapping thin-slab 3-D acquisition MR angiography: proposed technique for improved vessel visualization.

PURPOSE: To study the parameters of the 1331 fat saturation pulse (saturation pulse flip angle (SPFA) and interpulse delay (tau)) in order to identify values that provide optimal vessel visibility. METHODS: Carotid bifurcations of three healthy subjects were studied. RESULTS: The optimal values for the SPFA and tau were 60 degrees (7.5 degrees, -22.5 degrees, 22.5 degrees, -7.5 degrees) and 2.0-3.0 msec, respectively. At these values there was a 1.56-fold increase (SD = +/- .12, P less than .01) in the contrast-to-noise ratio between the left internal carotid artery and fat compared to the study without fat saturation. A 3.0-fold increase was noted for the smaller left occipital artery. Additionally, there was no statistically significant reduction in the vessel-muscle contrast-to-noise ratio nor in the absolute vessel signal-to-noise ratio at these values. CONCLUSION: Implementation of fat saturation into carotid MR angiography markedly improves visualization of vascular anatomy without increasing imaging time.

Adipose Tissue↗