Topics in magnetic resonance imaging : TMRI
-
Top Magn Reson Imaging · Aug 1996
ReviewMagnetization transfer magnetic resonance imaging: a clinical review.
Magnetic resonance imaging has traditionally used the T1 and T2 relaxation times and proton density (PD) of tissue water (hydrogen protons) to manipulate contrast. Magnetization transfer (MT) is a new form of tissue contrast based on the physical concept that tissues contain two or more separate populations of hydrogen protons: a highly mobile (free) hydrogen (water) pool, Hr, and an immobile (restricted) hydrogen pool, Hr, the latter being those protons bound to large macromolecular proteins and lipids, such as those found in such cellular membranes as myelin. Direct observation of the Hr magnetization pool is normally not possible because of its extremely short T2 time (< 200 microseconds). ⋯ A variety of clinically important uses of MT have emerged. In this clinical review of the neuroradiological applications of MT, we briefly review the physics of MT, the appearance of normal brain with MT, and the use of MT as a method of contrast enhancement/background suppression and in tissue characterization, such as evaluation of multiple sclerosis and other white-matter lesions and tumors. The role of MT in small-vessel visualization on three-dimensional time-of-flight magnetic resonance angiography and in head and neck disease and newer applications of MT are also elaborated.
-
Cranial nerves IX (glossopharyngeal), X (vagus), and XI (spinal accessory) are intimately related. Therefore, for imaging purposes they are best considered as a unit rather than as individual structures. ⋯ Because the course of these four pairs of cranial nerves extends from the base of the skull to the upper thorax, a combination of both magnetic resonance imaging (MRI) and computed tomography is needed for optimal evaluation. This article will emphasize the use of MRI when appropriate.
-
Movements of the eye are produced by six extraocular muscles innervated by three cranial nerves: the oculomotor (III), the trochlear (IV), and the abducens (VI). These cranial nerves are discussed together because of the interrelated nuclear origins, neural pathways, and motor functions. The normal anatomic pathway of these three nerves is presented. The clinical and pathologic manifestations of lesions producing both isolated and complex palsies of these nerves are discussed along with imaging correlation.
-
Top Magn Reson Imaging · Jan 1995
ReviewThe use of MR contrast in nonneoplastic disease of the brain.
The clinical utility of intravenous contrast administration in nonneoplastic disease of the brain is well established. Although primarily providing improved diagnostic specificity, contrast use can also improve lesion detection. Applications are discussed in infection, vascular disorders, diseases of white matter, and trauma. ⋯ Basic research suggests efficacy for high dose in disease states with partial or early blood-brain barrier disruption. Gadolinium chelates play as important a role in the evaluation of nonneoplastic disease of the brain as do iodinated agents in computed tomography. Contrast administration facilitates time-efficient and cost-effective diagnosis.
-
Top Magn Reson Imaging · Jan 1995
Magnetic resonance imaging of the female pelvis: technical considerations.
To perform magnetic resonance imaging of the female pelvis, one must be familiar with the imaging appearance of normal structures as well as the disease entities that may be encountered. However, it is also important to be familiar with and understand the basic physical principles of the available imaging techniques to be able to optimize image quality and the detection of abnormalities. This discussion is intended to describe the available imaging techniques used in evaluation of the female pelvis. ⋯ Pelvic multicoils will also be described in detail, including the choice of imaging parameters when using these coils and the unique artifacts that can be encountered. Chemical-selective imaging and motion artifact reduction techniques will additionally be described. At the end of the discussion, suggested imaging parameters are given for CSE and FSE sequences and for body coil and multicoil imaging.