Quadruple Contrast Enhancement with MRA and MR Spectroscopic Imaging

This approach minimized the false tissue classifications by (1) improving the lesion-to-tissue contrast on MR images by developing a fast imaging pulse sequence that incorporated both cerebrospinal fluid signal attenuation and magnetization transfer contrast (see Fig. 3.33) and (2) including information from MR flow images 24 . In pathologically defined abnormalities in the cortical gray matter (GM) and normal volunteers, high resolution MRI and short echo Figure 3.33 An approach is represented...

Phase Contrast Angiography

3D PC MRA technique relies on velocity-induced phase shifts to distinguish flowing blood from surrounding tissue. The phase contrast approach can be made sensitive to slow flow in small vessels. The reason for this can be attributed to the fact that the contrast between flowing blood and stationary-tissues is related to blood velocity, rather than stationary-tissue T1. PC angiography also permits excellent cancellation of stationary tissues and offers the potential for quantitative measurements...

Principles of Magnetization and Flow

The vascular system experiences motion of blood due to continuous flow of blood inside. Precession frequency and gradient field vectors are related. These vectors are represented as spin isochromats. The behavior of the moving spin 1 Department of Medicine, Columbia University, New York, NY 10032, USA 2Electrical Engineering Department, Indian Institute of Technology, New Delhi 10016, India isochromats can be explained as follows S St 0 Y (B + xGx + yGy + zGz) (3.1) where y is gyromagnetic...

Results

8.6.5.1 Transmission Electron Microscopy Transmission electron microscopy is the process of using transmission images of electron beams to reveal biological structures on very small dimensions. Typically transmission electron microscopy (TEM) datasets are produced using a dye that highlights regions of interest, e.g. the interior of a microscopic structure, such as a cell (see Fig. 8.22(a)). There are technical limits to the projection angles from which data can be measured. These limits are...

Tof

This approach is based on flow-related enhancement in which 2D or 3D GRE techniques are applied (see Fig. 3.6). Usually, FC (flow compensation) is used perpendicular to the lumen of the vessel. So, it relies primarily on flow-related Figure 3.6 Two-dimensional TOF MRA pulse sequence (left) and 3D TOF pulse sequence (right) are shown. Several gradient waveforms are combined to reduce TE. Figure 3.6 Two-dimensional TOF MRA pulse sequence (left) and 3D TOF pulse sequence (right) are shown. Several...

Stateofthe Art and Applications

In this section, we review two examples of multiscale denoising. To illustrate the power of multiscale analysis, two extreme cases of medical imaging modalities (ultrasound and PET SPECT) with high noise level and complicated noise patterns were considered. A more detailed description of these clinical applications can be found in 59, 60 . 6.3.5.1 Spatial-Temporal Analysis of Real-Time 3D Cardiac Ultrasound Using Brushlet 59 Recent development of a real-time three-dimensional (RT3D) ultrasound...

MRA Image Reformation

The MR data from MRA images is reformatted and this reformatting plays a major role in vascular anatomy observed in the MRA imaging. The common method for reformatting TOF-MRA uses the technique known as MIP. This technique also generates 3D images of blood vessels with blood motion. The other method for reformatting MRA images is shaded surface display. This method reformats image data in such a way that it appears as if a light is thrown onto structures to generate 3D appearance of...

Phase Contrast MRA

Acute Infarction Mri

Phase contrast PC MRA is based on the fact that the phase gain of flowing blood through a gradient is proportional to its velocity assuming constant velocity . Figure 3.14 Two-dimensional Phase contrast pulse sequence left and 3D phase contrast pulse sequence right are shown with velocity-induced phase shift to distinguish stationary and flowing spins. In both 2D 3D PC MRA, two or more acquisitions with opposite polarity of the bipolar flow-encoding gradients are subtracted to produce image of...

Attenuation Correction

One of the most important data correction techniques for PET and also SPECT studies is the correction for attenuation. Although the basic principles of image reconstruction in emission computed tomography PET and SPECT are the same as transmission tomography X-ray CT , there is a distinct difference in these two modalities on the data to be reconstructed. In X-ray CT, image reconstruction gives attenuation coefficient distribution of a known source while scattering is usually ignored. In PET...

Framework Results

Figure 8.4 presents one slice from an MRI scan of a mouse embryo, and an isosurface model of its liver extracted from the unprocessed dataset. Figure 8.5 presents 3D renderings of the sequence of steps performed on the mouse MRI data to segment the liver. The first step is the initialization, which includes smoothing the input data, thresholding followed by a a flood fill to remove isolated holes, and finally applying morphological operators to remove small gaps and protrusions on the surface....

Multislice GRE Techniques

Tilted Optimized Non Saturated

These techniques use longer decrease in repetition time TR. As a result, the saturation effects lead to signal loss with the use of larger flip angles. This approach using longer decrease in TR improves the SNR. Other ways are also used to decrease saturation effects. Common use of paramagnetic contrast agent such as gadolinium chelate causes spin-lattice relaxation time T1 shortening of blood see Fig. 3.25 . Consequently, the T1 recovery from short T1 to normal T1 values is faster with less...