Unexplained weight loss is defined as the unintentional loss of at least 10 pounds or 5 percent of body weight over a period of 6 to 12 months. This would be equivalent to a 200-pound man losing 10 pounds or a 130-pound woman losing six to seven pounds.
What It Is. Magnetic resonance imaging (MRI) of the brain is a safe and painless test that uses a magnetic field and radio waves to produce detailed images of the brain and the brain stem. An MRI differs from a CAT scan (also called a CT scan or a computed axial tomography scan) because it does not use radiation.
1 MRI scans are a non-invasive and painless procedure. 2  Unlike X-rays and CT scans, MRI does not ionize radiation, which is potentially harmful to the patient. 3  MRI is an acronym for magnetic resonance imaging.he scanner itself will resemble a large tube with a table in the middle, allowing the patient to slide into the tunnel. An MRI scan differs from CT scans and X-rays because it does not use ionizing radiation, which can be potentially harmful to a patient. 1.