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MRI’s application in clinical fields

Wakanda Hu

Overview of MRI

Biomedical Imaging Modalities

MRI, the abbreviation of magnetic resonance imaging is a type of biomedical imaging modalities, which includes ultrasounds, medical radiation, computed tomography (CT), and nuclear medicine (planar scintigraphy, SPECT, PET). It is a medical imaging technique of using energy sources like light, lasers, X-rays, etc. Medical image modalities are often used in biology and medical fields. The images produced span orders of magnitude. As for MRI, it uses magnetic resonance, transmitting radio frequency energy and receiving radio frequency energy to produce images. The items that can be presented in the image produced by MRI include organs, muscles, bones, and blood vessels. One thing worth noticing is that MRI does not use any radiation and is completely non-invasive, which is also a reason why it’s popular today.


MRI's Principles

The first step of conducting an MRI scan is to place a human into the magnetic field, which is usually in the form of an MRI machine. It is a cylindrical, tube-shaped machine that sends pulses of radio waves to create a strong magnetic field. The magnetic fields cause protons in the human body to align in the same direction, which is resonance, the R in MRI. The two aspects of the magnetic moment can be observed when protons are placed in a strong external magnetic field.


They either:

1.Align parallel

OR

2.Align anti-parallel to the external magnetic field

When protons are in a steady magnetic field, they are randomly spread.

And then detect the radio waves sent from MRI machines. These signals will be collected into the computer and converted into an image. The protons which go parallel to the field have relatively lower states, and the anti-parallel to the field has a higher energy state. Most of them cancel each other, and the excessive amount is called spin excess.


Another phenomenon is precession. The processional path is around the magnetic field like gyroscopes. It is a vertically orientated gyroscope.


Current Situation of MRI in Clinical Fields

Magnetic resonance imaging (MRI) is used today to look at organs tissues, skeletal systems, and structures inside the human body. After scanning, it will produce images of the body inside which are used for diagnoses, especially in fields of the brain and spinal cord. Several disadvantages of MRI which need improvement are the safety problems for patients who have metallic implants. The magnetic field will retain effects on the metal devices implanted in the body. Moreover, for patients who have Claustrophobia, MRI is also suffering because it is an enclosed place. Recent advances in MRI mainly focus on clinical operations, which as faster exam times, safer environment, and better image quality.


Applications


Neurosurgeons highly rely on iMRI (intraoperative magnetic resonance imaging) to obtain accurate images inside of the brain which helps them in fields of brain tumors, epilepsy, essential tremor, Glioma

Neuropsychiatric disorders, Parkinson's disease, Pediatric brain tumors, Pituitary tumors, etc.



Brain tumor

The use of MRI has been a critical tool in neurosurgeon’s armamentarium during tumor surgery. Research has shown it’s better to remove more tumor issues. Meanwhile, these brain tumors are extremely complex. Removing healthy tissue could cause deficits, which means people have to be accurate when doing brain tumor surgery. With innovative surgical technologies such as intraoperative MRI, people can identify and locate brain tumors more precisely and recognize their relation to their vital brain centers, such as but not limited to: control of speech, strength, vision, etc. Doctors use iMRI to assist in surgery to treat, there’re many benefits of iMRI. These include neuronavigation, compensation for movement, precision, mapping eloquent areas, and awake craniotomies. One of the biggest advantages of iMRI is its ability to precisely help locate brain tumors. The images generated are used during the surgery and serve as a guidance system. This directly solves the safety issues since it helps to identify and provide the safest surgical route to remove the tumor. During surgery, the organs on the side of the brain may shift, which will affect the precision of pre-surgical imaging. So the importance of having real-time iMRI images can be seen since people can adjust if needed according to the image produced by iMRI, which provides the actual position of the tumor. Another strength of iMRI is targeting the tumor embedded deep in the brain. MRI can be used in conjunction with functional MRI and other fiber-tracking technologies to visualize eloquent fields.



Dystonia

Dystonia according to Mayo Clinic is a movement disorder that causes muscles to contract involuntarily, including repetitive and twisting movement. It is a kind of neurological disorder linked to alterations in brain organization and environmental stressors and gene mutations. Neuro-imaging techniques had a substantial impact on the understanding of dystonia development, helping objective diagnosis and therapeutic interventions. It provides deeper insights into brain regional alterations at both structural and functional levels. Some recent improvements in apply of neuro-imaging in dystonia mainly focus on the attempt to link and understand the impact of gene mutations. Beginning with the discovery of DYT1. MRI help connects genetic factors and neural aberrancies.



Epilepsy

Epilepsy is a neuro disorder that happens in the central nervous system in which brain activity becomes abnormal and causes seizures. With symptoms like temporary confusion, stiff muscles, jerking movements of arms and legs, consciousness and awareness loss, fear, anxiety, déjà vu… MRI help to identify seizure and determine the proper seizure type. Tumors, malformations of cortical development, vascular malformations, mesial temporal sclerosis, and neocortical gliosis due to brain injury in epilepsy can be found on an MRI.


Notification before Taking an MRI Procedure

Because MRI is highly related to the magnetic field, any metal-made matters would affect the image. So patients need to report and remove any metal in the body. Consequently, it is required to remove all the piercings and leave all jewelry. If you are reporting it, make sure to include detailed information like the type of metal and location of metal, in order to determine the eligibility for MRI. As for food, drinks, and medications, people are allowed to have them as usual. Some people may need anti-anxiety medication due to claustrophobia. They may bring their prescription on the day of the appointment.


MRI Advantages and Disadvantages

As mentioned, no exposure to radiation and non-invasive is a huge advantage of MRI. It is also useful in scanning and detecting abnormalities in soft tissue. Thus, less likely to lead to an allergic reaction which may be caused by x-rays and CT scans.

The disadvantage of MRI scans focuses on their cost, health hazard, and the risk of creating negative feelings for patients. Since an MRI scan is conducted in an enclosed space with loud knocking noises made by magnets, it will make some people fear doing an MRI scan. In severe cases, it will harm hearing if adequate ear protection is absent. Some people might also feel a twitching sensation because it may cause peripheral muscle stimulation.


Conclusion

Magnetic Resonance Imaging still has much room for improvement and innovation and is highly used for detecting and identifying disease while creating a safe surgery path for neurosurgery.

Works Cited

Author links open overlay panelDivyaVaradarajanEnvelopeJustin P.HaldarPersonEnvelope, et al. “A Theoretical Signal Processing Framework for Linear Diffusion MRI: Implications for Parameter Estimation and Experiment Design.” NeuroImage, Academic Press, 19 Aug. 2017, https://www.sciencedirect.com/science/article/abs/pii/S105381191730695X.

Author links open overlay panelThomas T.LiuaPersonEnvelopeEric C.Wongab, et al. “A Signal Processing Model for Arterial Spin Labeling Functional MRI.” NeuroImage, Academic Press, 13 Nov. 2004, https://www.sciencedirect.com/science/article/abs/pii/S1053811904005890.

Authored By:Joseph I. Sirven MDRuben Kuzniecky, et al. “MRI.” Epilepsy Foundation, https://www.epilepsy.com/diagnosis/brain-imaging/mri.

“Brain Tumor.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 6 Aug. 2021, https://www.mayoclinic.org/diseases-conditions/brain-tumor/symptoms-causes/syc-20350084.

“Intraoperative Magnetic Resonance Imaging (IMRI).” Mayo Clinic, Mayo Foundation for Medical Education and Research, 5 Mar. 2022, https://www.mayoclinic.org/tests-procedures/intraoperative-magnetic-resonance-imaging/about/pac-20394451#:~:text=Overview,other%20conditions%20such%20as%20epilepsy.

JS;, Rogers CM;Jones PS;Weinberg. “Intraoperative MRI for Brain Tumors.” Journal of Neuro-Oncology, U.S. National Library of Medicine, https://pubmed.ncbi.nlm.nih.gov/33611714/.

“Magnetic Resonance Imaging (MRI).” Magnetic Resonance Imaging (MRI) | Johns Hopkins Medicine, 6 Dec. 2021, https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/magnetic-resonance-imaging-mri#:~:text=The%20strong%20magnetic%20field%20created,and%20send%20back%20radio%20signals.

“Magnetic Resonance Imaging (MRI).” Magnetic Resonance Imaging (MRI) | Johns Hopkins Medicine, 6 Dec. 2021, https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/magnetic-resonance-imaging-mri#:~:text=The%20strong%20magnetic%20field%20created,and%20send%20back%20radio%20signals.

Simonyan, Kristina. “Neuroimaging Applications in Dystonia.” International Review of Neurobiology, U.S. National Library of Medicine, 2018, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6331056/.

Sobol, Wlad T. “Recent Advances in MRI Technology: Implications for Image Quality and Patient Safety.” Saudi Journal of Ophthalmology : Official Journal of the Saudi Ophthalmological Society, U.S. National Library of Medicine, Oct. 2012, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3729307/.

University, Rice, and OpenStaxCollege. “Anatomy & Physiology.” Anatomy Physiology, 6 Mar. 2013, https://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/.



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