Editing Brain tumor (section)

==== Different Types of MRI Scans ====
'''Magnetic Resonance Angiography (MRA)'''{{snd}} looks at the blood vessels in the brain. In the diagnosis of brain tumor, MRAs are typically carried out before surgery to help surgeons get a better understanding of the tumor vasculature. For example, a study was done where surgeons were able to separate benign brain tumors from malignant ones by analyzing the shapes of the blood vessels that were extracted from MRA.<ref>{{cite conference | vauthors = Bullitt E, Jung I, Muller K, Gerig G, Aylward S, Joshi S, Smith K, Lin W, Ewend M |title=Determining Malignancy of Brain Tumors by Analysis of Vessel Shape |date=2004 | doi = 10.1007/978-3-540-30136-3_79 | conference = Medical Image Computing and Computer-Assisted Intervention – MICCAI 2004 |pages=645–653 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |isbn=978-3-540-22977-3 |doi-access=free }}</ref> Although not required, some MRA may inject contrast agent, gadolinium, into the patient to get an enhanced image

'''Magnetic Resonance Spectroscopy (MRS)'''{{snd}} measures the metabolic changes or chemical changes inside the tumor. The most common MRS is proton spectroscopy with its frequency measured in parts per million (ppm). Gliomas or malignant brain tumors have different spectra from normal brain tissue in that they have greater choline levels and lower N-acetyl aspartate (NAA) signals.<ref>{{cite journal | vauthors = Horská A, Barker PB | title = Imaging of brain tumors: MR spectroscopy and metabolic imaging | journal = Neuroimaging Clinics of North America | volume = 20 | issue = 3 | pages = 293–310 | date = August 2010 | pmid = 20708548 | doi = 10.1016/j.nic.2010.04.003 | pmc = 2927327 }}</ref> Using MRS in brain tumor diagnosis can help doctors identify the type of tumor and its aggressiveness. For example, benign brain tumors or meningioma have increased alanine levels. It can also help to distinguish brain tumors from scar tissues or dead tissues caused by previous radiation treatment, which does not have increased choline levels<ref>{{Cite web |title=MRI (magnetic resonance imaging) |url=https://mayfieldclinic.com/pe-mrspectroscopy.htm |access-date=2022-11-28 |website=mayfieldclinic.com |language=EN}}</ref> that brain tumors have, and from tumor-mimicking lesions such as abscesses or infarcts.

'''Perfusion Magnetic Resonance Imaging (pMRI)'''{{snd}} assess the blood volume and blood flow of different parts of the brain and brain tumors. pMRI requires the injection of contrast agent, usually gadopentetate dimeglumine (Gd-DTPA) into the veins in order to enhance the contrast. pMRI provides a cerebral blood volume map that shows the tumor vascularity and angiogenesis. Brain tumors would require a larger blood supply and thus, would show a high cerebral blood volume on the pMRI map. The vascular morphology and degree of angiogenesis from pMRI help to determine the grade and malignancy of brain tumors. For brain tumor diagnosis, pMRI is useful in determining the best site to perform biopsy and to help reduce sampling error. pMRI is also valuable for after treatment to determine if the abnormal area is a remaining tumor or a scar tissue. For patients that are undergoing anti-angiogenesis cancer therapy, pMRI can give the doctors a better sense of efficacy of the treatment by monitoring tumor cerebral blood volume.<ref>{{cite journal | vauthors = Cha S | title = Perfusion MR imaging of brain tumors | journal = Topics in Magnetic Resonance Imaging | volume = 15 | issue = 5 | pages = 279–289 | date = October 2004 | pmid = 15627003 | doi = 10.1097/00002142-200410000-00002 | s2cid = 25773559 | doi-access = free }}</ref>

'''Functional MRI (fMRI)'''{{snd}} measures blood flow changes in active parts of the brain while the patient is performing tasks and provides specific locations of the brain that are responsible for certain functions. Before performing a brain tumor surgery on patients, neurosurgeons would use fMRI to avoid damage to structures of the brain that correspond with important brain functions while resecting the tumor at the same time. Preoperative fMRI is important because it is often difficult to distinguish the anatomy near the tumor as it distorts its surrounding regions. Neurosurgeons would use fMRI to plan whether to perform a resection where tumor is surgically removed as much as possible, a biopsy where they take a surgical sampling amount to provide a diagnosis, or to not undergo surgery at all. For example, a neurosurgeon may be opposed to resecting a tumor near the motor cortex as that would affect the patient's movements. Without preoperative fMRI, the neurosurgeon would have to perform an awake-craniotomy where the patient would have to interact during open surgery to see if tumor removal would affect important brain functions.<ref>{{cite journal | vauthors = Bogomolny DL, Petrovich NM, Hou BL, Peck KK, Kim MJ, Holodny AI | title = Functional MRI in the brain tumor patient | journal = Topics in Magnetic Resonance Imaging | volume = 15 | issue = 5 | pages = 325–335 | date = October 2004 | pmid = 15627006 | doi = 10.1097/00002142-200410000-00005 | s2cid = 45995537 }}</ref>

'''Diffusion Weighted Imaging (DWI)'''{{snd}} a form of MRI that measures random Brownian motion of water molecules along a magnetic field gradient. For brain tumor diagnosis, measurement of apparent diffusion coefficient (ADC) in brain tumors allow doctors to categorize tumor type. Most brain tumors have higher ADC than normal brain tissues and doctors can match the observed ADC of the patient's brain tumor with a list of accepted ADC to identify tumor type. DWI is also useful for treatment and therapy purposes where changes in diffusion can be analyzed in response to drug, radiation, or gene therapy. Successful response results in apoptosis and increase in diffusion while failed treatment results in unchanged diffusion values.<ref>{{cite journal | vauthors = Maier SE, Sun Y, Mulkern RV | title = Diffusion imaging of brain tumors | journal = NMR in Biomedicine | volume = 23 | issue = 7 | pages = 849–864 | date = August 2010 | pmid = 20886568 | pmc = 3000221 | doi = 10.1002/nbm.1544 }}</ref>