Technical Aspects of the IVUS

The images of ultrasound 7 are based on the reception and transmission of high-frequency sound waves. The transmitted wave propagates through the material until it strikes the reflecting object. The reflected wave returns and is received by a transducer. The time interval between the transmission and the reception of the wave is directly related to the distance between the source and the reflector. The advantage of ultrasound is that it can travel through water smooth tissue. Additionally,...

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...

Numerical Solutions

The numerical solution for region force diffusion is discussed in detail in Section 10.5.1, but the detailed numerical solutions for RAGS level set representation are only presented in Appendix A as they are not critical to the understanding of the concepts underlying RAGS. In fact, the whole of this section can be skipped without loss of continuity. 10.5.1 Numerical Solutions for Region Force Diffusion for RAGS Initially, a mesh grid needs to be selected, with final accuracy directly dependent...

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

Gradient Echo Rephasing

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....

Gadolinium Enhanced MRA with MR Cholangiography MRC

Simultaneously both methods were used in the preoperative evaluation of gallbladder carcinoma 22 . All MR images were analyzed in order to assess bile duct invasion, vascular invasion, hepatic invasion or metastasis, lymph node metastasis, and invasion into adjacent organs. The sensitivity and specificity of MR examination were distinctive 100 and 89 for bile duct invasion, 100 and 87 for vascular invasion, 67 and 89 for hepatic invasion, and 56 and 89 for lymph node metastasis supported by...

Multislice GRE Techniques

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...