A new application of MP-RAGE IP/OP images is able to substitute standard dual GR IP/OP imaging with moderate image quality in the elderly, severely debilitated, and in young children (Figure 1). Dual GE IP/OP imaging is performed as multiline GE acquisitions that require patients to suspend their respiration as the sequences are generally 10–20 seconds in duration. This sequence is useful for detecting the presence of fat within the liver and lipid within adrenal masses in order to characterize them as adenomas. The dual GE in-phase (IP) and opposed-phase (OP) sequence has become a routine component of liver MR imaging. Magnetization-Prepared Rapid-Acquisition Gradient Echo (MP-RAGE) Sequence Parameters for the motion-resistant protocol used for 3.0T MR imaging scanners.Ģ.1. Another approach used to minimize the impact of respiratory motion in the liver is to modify the data acquisition so as to minimize effects of motion using a radial k-space sampling scheme (Table 1). A strategy for achieving optimal images includes temporally matching the data acquisition and short scanning time by acquiring the critical data for image creation during a short breath-hold time and thus rendering this technique relatively insensitive to patient motion. Motion-resistant protocols achieve improved image quality in the setting of noncooperative patients. In this paper, we discuss motion-resistant MR imaging in terms of its technical basis, advantages and limitations, and primary clinical applications. With the recent advances in the development of high-performance gradient coils and phased-array torso coils as well as the continuing evolution of software, new pulse sequences have become available for motion-resistant liver MR imaging. Therefore, suppression of motion artifacts is the prime determinant of the diagnostic efficacy of liver MR imaging. Motion artifacts may also distinctly degrade the quality of MR images. Artifacts produced by physiological motion caused by patient respiration and bowel peristalsis are a challenge when using MR imaging for hepatic imaging. Magnetic resonance (MR) imaging is an excellent imaging modality to evaluate the liver which is vulnerable to a spectrum of neoplastic and nonneoplastic conditions, and MR imaging can provide various types of information that it is able to generate in order to demonstrate reliable display of disease process. Understanding of the different motion-resistant options allows radiologists to adopt the most appropriate technique for their clinical practice and thereby significantly improve patient care. In this setting, the recent advances in motion-resistant liver MR techniques, including faster imaging protocols (e.g., dual-echo magnetization-prepared rapid-acquisition gradient echo (MP-RAGE), view-sharing technique), the data under-sampling (e.g., gradient recalled echo (GRE) with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA), single-shot echo-train spin-echo (SS-ETSE)), and motion-artifact minimization method (e.g., radial GRE with/without k-space-weighted image contrast (KWIC)), can provide consistent, artifact-free images with adequate image quality and can lead to promising diagnostic performance. In uncooperative patients, motion artifacts can impair the image quality and lead to the loss of diagnostic information. However, as the tube ages further, resulting in images with more pronounced artifacts.MR imaging has unique benefits for evaluating the liver because of its high-resolution capability and ability to permit detailed assessment of anatomic lesions. In the early stages the arcing may be infrequent, and small artifacts begin to appear in the images. The arcing causes a momentary loss of xray output, which contaminates the xray signal collected at the detectors, affecting proper image reconstruction and hence producing artifacts. Once an xray tube starts to arc, a cascade -type effect may occur that sets event in motion that contribute to yet more frequent arcing. Arcing can also occur through the oil in the xray tube housing. As an xray tube ages, the tendency to arc often increases owing to such factors as degradation of the vacuum within the tube, which results in increased gas pressure. In a xray tube, arcing can occur through residual gas molecules present within the evacuated envelop of the xray tube. Arcing tends to occur whenever there is a large difference in electrical potential, such as the case between the anode and cathode in an xray tube. This is referred to as either high voltage arcing or tube arcing. A common cause of equipment induced artifact occurs when there is a undesired surge of electrical current like a short-circuit, within the xray tube.
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