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Magnetic Resonance Imaging
Published in Bethe A. Scalettar, James R. Abney, Cyan Cowap, Introductory Biomedical Imaging, 2022
Bethe A. Scalettar, James R. Abney, Cyan Cowap
MRI has many strengths. MRI is very safe, due to the use of low-energy RF radiation, and is capable of evaluating both anatomy and function. MRI can generate slices at any orientation and can generate contrast using parameters, such as signal decay times, that are much more tissue-specific than proton density. This latter capability is a source of exceptional soft tissue contrast, and thus MRI commonly is used to study abdominal organs and soft tissue (e.g., cartilage and ligament) damage and to identify tumors. One application in which MRI particularly excels relative to competing modalities, notably CT, is imaging both function and abnormalities of the brain. In these cases, the superior contrast detail of MRI makes abnormalities more visible. Limitations of MRI include the high cost of the equipment, generally slow image acquisition and an associated need for patients to remain motionless, and incompatibility with pacemakers and metal implants. Exposure to high levels of RF radiation also has the potential to induce patient heating.
Living in a Magnetic World
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
During an MRI scan, the patient must lie very still inside the bore of an MRI scanner (such as that shown in Figure 8.11) containing a powerful permanent magnet or electromagnet that produces a magnetic field at least 1.5 T in strength, although generally higher. (A field of 1.5 T is 30,000 times greater than the Earth’s magnetic field and enables clear, high-quality images to be produced.) Water makes up around 65% of the human body, and the MRI image is obtained from the spins of protons within the hydrogen atoms present in this water. When they are not subjected to a high magnetic field, these proton spins are randomly aligned. However, once subjected to the field created by the scanner magnet, they align their spins within the applied field, precessing (wobbling) on their axes as they go round. (In fact, some protons align with the field, while others line up antiparallel to it.)
Segmentation and Clinical Outcome Prediction in Brain Lesions
Published in Shampa Sen, Leonid Datta, Sayak Mitra, Machine Learning and IoT, 2018
Sharmila Nageswaran, S. Vidhya, Deepa Madathil
A lesion can be defined as a region in a tissue, or an organ, which has been damaged through disease or injury. Diagnosis of lesions in real time, using reliable algorithms, has been the main focus of the latest developments in medical image processing. In this area, the major focus of research has been the detection of lesions using MR (magnetic resonance) and CT (computed tomography) images. Usually CT and MRI are used to examine the anatomy of brain lesions. Magnetic resonance imaging (MRI) is a technology used in biomedical applications to detect and visualize minute details of the internal body structure. This technique detects differences in the tissues, and is a far better technique compared to CT in terms of image properties and quality. Cancer imaging and lesion detection are major applications related to MRI [1]. Since MRI provides more accurate results and does not involve any radiation, it has an advantage over CT scans. MRI is a technology using magnetic fields and radio waves.
Analysis of SAR reduction to human head with plasma photonic crystals shield using ICCG-SFDTD method
Published in Radiation Effects and Defects in Solids, 2021
Da-Jie Song, Yun Zhang, Jin Xie, Yu-Jie Liu, Hong-Wei Yang
MRI is considered a safe technology because it relies on the spatial encoding of atomic nuclei (mainly protons) position in a static magnetic field by irradiation with radio-frequency (RF) pulses as opposed to ionizing radiation (11). MRI systems are routinely used for clinical diagnosis and can produce high-quality images with relatively low static magnetic field strengths (12). However, ultra-high-field MRI systems are required in order to achieve enhanced signal-to-noise ratio in images and to improve resolution for spectroscopy applications in the future, challenges exist as significantly strong electric field and eddy currents can result in more RF energy deposits that potentially initiate tissue heating and cause other side effects, such as alterations in visual, auditory and neural functions (13). SAR (14) is the most frequently used parameter for monitoring and quantifying the power deposition to subjects in the electromagnetic environment. Strict exposure limits to SAR levels are imposed by the International Commission on Non-Ionizing Radiation Protection.
In vivo person specific human body simulation for development and optimisation of surgical methods and materials
Published in Computer Methods in Biomechanics and Biomedical Engineering: Imaging & Visualization, 2019
Rashid Ahmad, Peter Hodgson, Xiao Bo Zhang, Andrew Whan, Kate Negus
As we are building a global model of a living person, so called in-vivo, the selection of the scanning technique plays an important role for the safety of the volunteer and details needed for the study. The two main imaging techniques available for creation of a three dimensional human anatomical dataset are CT and MRI. For comparison refer to CT vs. MRI (http://www.diffen.com/difference/CT_Scan_vs_MRI). As MRI imaging provides good contrast between the bones, muscles, cartilage, ligaments and various joints, MRI was selected for scanning. Moreover, due to the size of the anatomical area to be imaged and the need for multiple image acquisitions with different load scenarios (Section 2.4), using CT would unnecessarily expose the volunteer to ionising radiation (Radiation, http://www.nhs.uk/Conditions/Radiation/Pages/Introduction.aspx). MRI works on the principle that the body to be scanned contains water. The hydrogen molecules of water have a magnetic spin that can be aligned by a strong burst of radio-frequency waves from an MRI machine (Live Sciences, http://www.livescience.com/32282-how-does-an-mri-work.html). MRI is considered a very safe imaging tool with no lasting side effects. An Avanto 1.5 Tesla MRI scanner from Siemens, Erlangen, Germany, is used for imaging as detailed in Sections 2.4.1 and 2.4.2.
Hybrid deep learning algorithm for brain tumour detection
Published in The Imaging Science Journal, 2022
Jyoti Srivastava, Jay Prakash, Ashish Srivastava
If there is an unnatural rise in the total number of brain cells, then we are talking about a tumour in the brain. A powerful sense of solidity pervades the brain as the skull encloses the brain [1]. Complicating factors include any structural growth, such as a walled-in area. More often than not, brain tumours that are malignant (cancerous) are more likely to be cancerous than brain tumours that are benign (non-cancerous). There is a risk of brain injury and even death if these tumours keep growing and expanding at their current rate [2]. Two types of brain tumours can develop secondary tumours and primary tumours. It is possible to have an inoperable primary brain tumour that's non-cancerous develop in someone's brain [3]. Metastatic brain tumours are those cancers that have spread from another organ, such as the lung or the breast [4, 5]. In the end, the tumour was discovered thanks to medical imaging tools. Imaging techniques are one of the subfields of radiology. Radiological techniques can provide helpful information on the human body's anatomy and physiology, which can be used in a wide variety of contexts. Contrasting chemicals can enhance the quality of pictures [6] captured by imaging modalities such as ultrasound, CT, X-ray, and MRI. MRI (magnetic resonance imaging) is an advanced medical imaging technique that produces high-quality human body images. A radio wave-based imaging technique known as magnetic resonance imaging (MRI) is a type of MRI [7]. Tumours of the brain, ankles and feet can be detected and treated using magnetic resonance imaging (MRI). When studying, magnet fields and radio waves [8] are more successful than current imaging technologies since they are not detrimental to the human body.