Signal, noise, and contrast in nuclear magnetic resonance (NMR) imaging

Edelstein, William A.; Bottomley, PA; Hart, H.R.; Smith, L.S.

doi:10.1016/0730-725x(84)90082-1

Cited by 15 publications

(27 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…64,65 To include this bias, the synthetic noiseless MR signal intensity in the previous section was placed entirely in the real channel, then independent noise fluctuations were added to the real and imaginary channels, and the modulus was computed and integerized (see Appendix).…”

Section: Addition Of Noise To the Synthetic Dt-mri Datamentioning

confidence: 99%

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

et al. 2002

View full text Add to dashboard Cite

We present a description, biological results and a reliability analysis for the method of diffusion tensor tracking (DTT) of white matter fiber pathways. In DTT, diffusion-tensor MRI (DT-MRI) data are collected and processed to visualize the line trajectories of fiber bundles within white matter (WM) pathways of living humans. A detailed description of the data acquisition is given. Technical aspects and experimental results are illustrated for the geniculo-calcarine tract with broad projections to visual cortex, occipital and parietal U-fibers, and the temporocalcarine ventral pathway. To better understand sources of error and to optimize the method, accuracy and precision were analyzed by computer simulations. In the simulations, noisy DT-MRI data were computed that would be obtained for a WM pathway having a helical trajectory passing through gray matter. The error vector between the real and ideal track was computed, and random errors accumulated with the square root of track length consistent with a random-walk process. Random error was most dependent on signal-to-noise ratio, followed by number of averages, pathway anisotropy and voxel size, in decreasing order. Systematic error only occurred for a few conditions, and was most dependent on the stepping algorithm, anisotropy of the surrounding tissue, and non-equal voxel dimensions. Both random and systematic errors were typically below the voxel dimension. Other effects such as track rebound and track recovery also depended on experimental conditions. The methods, biological results and error analysis herein may improve the understanding and optimization of DTT for use in various applications in neuroscience and medicine.

show abstract

Section: Addition Of Noise To the Synthetic Dt-mri Datamentioning

confidence: 99%

Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results

et al. 2002

View full text Add to dashboard Cite

show abstract

“…By varying β, a tradeoff between spatial resolution and contrast resolution is obtained in the reconstructed image. Let CNR be the local image contrast-to-noise ratio defined in [7], [11], and [19] (15) where Ī o and Ī b represent the average intensity (in dB) in the cysts region and the local background region containing the cysts, respectively, and σ I b denotes the standard deviation of the background intensity (in dB). The normalized CNR values of the cyst regions in Fig.…”

Section: B Phantom Imagesmentioning

confidence: 99%

Filter-based coded-excitation system for high-speed ultrasonic imaging

Shen

Ebbini

1998

IEEE Trans. Med. Imaging

View full text Add to dashboard Cite

We have recently presented a new algorithm for high-speed parallel processing of ultrasound pulse-echo data for real-time three-dimensional (3-D) imaging. The approach utilizes a discretized linear model of the echo data received from the region of interest (ROI) using a conventional beam former. The transmitter array elements are fed with binary codes designed to produce distinct impulse responses from different directions in ROI. Image reconstruction in ROI is achieved with a regularized pseudoinverse operator derived from the linear receive signal model. The reconstruction operator can be implemented using a transversal filter bank with every filter in the bank designed to extract echoes from a specific direction in the ROI. The number of filters in the bank determines the number of image lines acquired simultaneously. In this paper, we present images of a cyst phantom reconstructed based on our formulation. A number of issues of practical significance in image reconstruction are addressed. Specifically, an augmented model is introduced to account for imperfect blocking of echoes from outside the ROI. We have also introduced a column-weighting algorithm for minimizing the number of filter coefficients. In addition, a detailed illustration of a full image reconstruction using subimage acquisition and compounding is given. Experimental results have shown that the new approach is valid for phased-array pulse-echo imaging of speckle-generating phantoms typically used in characterizing medical imaging systems. Such coded-excitation-based image reconstruction from specklegenerating phantoms, to the best of our knowledge, have not been reported previously.

show abstract

“…When this problem is suspected, MR images acquired with and without the presence of the monitoring equipment must be compared for both presence of artifact and for overall image quality (generally assessed by measuring the signalto-noise). 4 Other problems occur when electrical artifacts and/ or heating is induced in the monitoring leads by the ra-CAN J ANAESTH 1993 / 40: I 1 / pp 1092-5 diofrequency (RF) pulses and switching of gradients required to generate the MR image. Bums as a result of overheating in leads or probes have been reported, s Risk to the patient from overheating is relatively easily avoided by insulating properly all leads and by assuring that the leads do not make a loop Within the bore of the magnet.…”

mentioning

confidence: 99%