Velocity Imaging Technique Research Articles

The role of colour velocity imaging (CVI) in prostate ultrasound

Objectives: Until now, experience with colour Doppler imaging (CDI) or colour velocity imaging (CVI) for diagnosing prostatic diseases in addition to transrectal ultrasound (TRUS) is limited. The resistance index (RI) of the supplying arteries to the prostate was estimated and the change of the resistance index due to prostatic diseases was assessed. Methods: We investigated the location of the supplying arteries to the prostate and determined the resistance index in 123 males, either complaining of prostatism or looking for exclusion of prostate cancer. Ages varied from 37 to 86 years (mean 61). For ultrasound scanning and the determination of the resistance index a Philips P 700 was used with a multi-frequency probe and the colour velocity imaging technique. Results: In a number of patients a correlation between the presence and location of flow and certain prostatic diseases could be shown, though without statistical significance. In normal and diseased prostates the resistance index of the supplying arteries and its branches was calculated and compared. Using the Wilcoxon matched-pairs test and the Mann-Whitney U-test we could find a significant statistical difference between the main supplying arteries (neurovascular bundle) and its branches ( P < 0.0001). The lowest values of the resistance index were found in patients with prostate carcinoma or bacterial prostatitis. Conclusion: Colour velocity imaging and the resistance index of the supplying arteries of the prostate appear to have additional diagnostic value compared to TRUS alone, especially in patients suffering from bacterial prostatitis or prostate cancer.

Measurement of pulsatile flow using MRI and a Bayesian technique of probability analysis.

This work shows that complete spatial information of periodic pulsatile fluid flows can be rapidly obtained by Bayesian probability analysis of flow encoded magnetic resonance imaging data. These data were acquired as a set of two-dimensional images (complete two-dimensional sampling of k-space or reciprocal position space) but with a sparse (six point) and nonuniform sampling of q-space or reciprocal displacement space. This approach enables more precise calculation of fluid velocity to be achieved than by conventional two q-sample phase encoding of velocities, without the significant time disadvantage associated with the complete flow measurement required for Fourier velocity imaging. For experimental comparison with the Bayesian analysis applied to nonuniformly sampled q-space data, a Fourier velocity imaging technique was used with one-dimensional spatial encoding within a selected slice and a uniform sampling of q-space using 64 values of the pulsed gradients to encode fluid flow. Because the pulsatile flows were axially symmetric within the resolution of the experiment, the radial variation of fluid velocity, in the direction of the pulsed gradients, was reconstructed from one-dimensional spatial projections of the velocity by exploiting the central slice theorem. Data were analysed for internal consistency using linearised flow theories. The results show that nonuniform q-space sampling followed by Bayesian probability analysis is at least as accurate as the combined uniform q-space sampling with Fourier velocity imaging and projection reconstruction method. Both techniques give smaller errors than a two-point sampling of q-space (the conventional flow encoding experiment).

Phase velocity mapping with a real time line scan technique.

A real-time, 20-Hz, one-dimensional MR velocity imaging technique is described. A two-dimensional RF pulse excites a 3-cm diameter column. Velocity maps are formed from the phase difference between successive flow encoded and compensated acquisitions. A three-point subtraction variation provides reduced sensitivity to static spins.

Angle independent ultrasonic blood flow detection by frame-to-frame correlation of B-mode images

We have previously reported initial clinical results of a novel blood velocity imaging technique utilizing a two-dimensional correlation search applied to consecutively acquired echoes. In this paper, we describe both the physical principles underlying this technique and test tank experiments which define its performance under a variety of conditions. The results indicate that, unlike Doppler flow imaging systems, this technique defines the flow velocity vector in two dimensions and is not subject to aliasing.

Human brain motion and cerebrospinal fluid circulation demonstrated with MR velocity imaging.

Present theory holds that pulsatile pressure of cerebrospinal fluid (CSF) is driven by the force of expansion of the choroid plexus. Alternate theories postulating that a possible movement of the brain is involved in pumping CSF have not, to the authors' knowledge, been substantiated heretofore. In this study, in vivo, quantitative magnetic resonance (MR) imaging methods were developed to show reproducible magnitudes and directions of CSF flow. Measurements were obtained with a new MR velocity imaging technique at high resolution (0.4 mm/sec), requiring 64 cardiac cycles per image. Twenty-five healthy volunteers and five patients were studied. Observations of pulsatile brain motion, ejection of CSF out of the cerebral ventricles, and simultaneous reversal of CSF flow direction in the basal cisterns toward the spinal canal, taken together, suggest that a vascular-driven movement of the entire brain may be directly pumping the CSF circulation. The authors describe what they believe to be the first observations and measurements of human brain motion, which occurs in extensive internal regions (particularly the diencephalon and brain stem) and is synchronous with cardiac systole.