Magnetic Resonance Imaging
Shoogo Ueno in Bioimaging, 2020
Magnetic resonance imaging is a technique to obtain images based on nuclear magnetic resonance (NMR) signals generated by nuclei under a strong magnetic field. Hemoglobin magnetic properties depend upon bonding with oxygen. Superconducting magnets are advantageous in that they can generate a strong magnetic field approaching a maximum of 10 T and the generated magnetic field is highly stable over time. Because permanent magnets do not require cooling, they are easy to maintain and are used in low magnetic field devices. Immediately after the strength of the external magnetic field applied to the nuclear spin changes abruptly or when the nuclear spin moves between Zeeman levels due to NMR, the magnetization temporarily deviates from the state of thermal equilibrium. The local magnetic field strength is different for each nucleus and varies with time. This acts in a direction to disassemble the orientation of the magnetic moments of the nuclei.
Evidence for the Presence of a Visceral Pain Pathway in the Dorsal Column of the Spinal Cord
Mark J Rowe, Yoshiaki Iwamura in Somatosensory Processing: From Single Neuron to Brain Imaging, 2001
Investigation of the dorsal column visceral pain pathway was extended to monkeys to ensure that evidence like that obtained in rats could be obtained in a species whose nervous system closely resembles that of humans. Long ascending axons in the dorsal column of the mammalian spinal cord are generally thought to arise either from dorsal root ganglion cells or from neurons whose cell bodies are located in the gray matter of the dorsal horn. In order to determine the brain structures that are affected by colorectal distention and the changes that might occur following a lesion of the dorsal column, a functional magnetic resonance imaging study was initiated. Clinical evidence indicates that the human dorsal column contains an important visceral pain pathway that, when interrupted, can relieve the pain of cancer affecting pelvic viscera. The dorsal column also mediates responses to weak mechanical stimulation of the skin.
Musculoskeletal system
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha in Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
Until the advent of high-resolution ultrasound and magnetic resonance imaging (MRI), the mainstay of musculoskeletal (MSK) investigation was plain image radiography. Plain radiography has a role, but the main modalities for MSK imaging are ultrasound and MRI. Plain radiography is the starting point for many MSK conditions including trauma, opaque foreign bodies, arthritides, bone or joint infection and tumours. MRI is considered by many to be the gold standard test for MSK problems due to the excellent soft tissue resolution achievable and ability to image in multiple planes. The management and optimal investigation pathway for MSK disorders will depend on the area of the body that is symptomatic, in that investigation of some joints and superficial lesions may be best by ultrasound, and larger joints or deeper structures by MRI.
Magnetic resonance imaging as a diagnostic modality in a child with acute lymphoblastic leukemia
Published in Baylor University Medical Center Proceedings, 2019
Nishath Farhad, Krista Birkemeier, Lea H. Mallett
Acute lymphoblastic leukemia is the most common form of childhood cancer. It presents with nonspecific symptoms, such as bone pain, that can be easily misdiagnosed at initial presentation. We present a 2-year-old boy with bilateral foot pain that worsened over 6 months. X-rays of the feet showed no obvious abnormalities. Magnetic resonance imaging revealed abnormal bone marrow consistent with an infiltrative process. The patient was found to have precursor B-cell acute lymphoblastic leukemia. Cases such as these highlight the possible future use of magnetic resonance imaging in the early diagnostic workup for bone and muscle pain.
Magnetic resonance imaging in the evaluation of intracranial hemorrhage
Published in Expert Review of Neurotherapeutics, 2004
Magnetic resonance imaging is emerging as a valuable tool for the urgent evaluation of patients with acute stroke. This review focuses on the applications of magnetic resonance imaging in the diagnosis and management of intracranial hemorrhage. The biophysical properties of blood in the neuroaxis and the magnetic resonance imaging evolution of intracranial bleeding are reviewed. The potential applications of magnetic resonance imaging in the evaluation and therapy of specific types of intracranial hemorrhage are discussed. Emphasis is made on the superiority of magnetic resonance imaging in detecting intracranial hemorrhage and ischemic stroke. Although there is some hesitation to perform magnetic resonance imaging to evaluate acute intracranial hemorrhage, there is strong evidence that magnetic resonance imaging is not inferior to computerized tomography in this clinical setting. In the era of acute stroke intervention, magnetic resonance imaging offers significant advantages over computed tomography.
Functional Magnetic Resonance Imaging in Patients with the Wet Form of Age-Related Macular Degeneration
Published in Neuro-Ophthalmology, 2013
Jan Lešták, Jaroslav Tintěra, Ivan Karel, Zuzana Svatá, Pavel Rozsíval
The study is designed to determine the relationship between the progress of the wet form of age-related macular degeneration and the activity of the visual cortex examined using functional magnetic resonance imaging. Ten patients with the wet form of age-related macular degeneration (9 female and 1 male) with a mean age of 74.7 years (58–85 years) at various stages of bilateral involvement of the disease were included. Patients did not suffer from any other ocular nor neurological disease. All the patients underwent functional magnetic resonance imaging examinations with stimulation of both eyes using a black-and-white checkerboard of size 25.8 × 16.2 degrees. The group was compared with a group of healthy subjects with an average age of 54.1 years (45–65 years). For statistical evaluation, the Mann-Whitney U test was used. Comparing the extent of visual cortex activations we found a statistically significant difference between both the groups (p = 0.0247). However, the dependence of functional magnetic resonance imaging activity on visual acuity was not statistically significant (p = 0.223). We conclude that in patients with the wet form of age-related macular degeneration, lower functional magnetic resonance imaging activity of the visual cortex was found compared with the control group of healthy subjects. Dependence of functional magnetic resonance imaging activity on visual acuity was not statistically significant.
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