What is the difference between a CT scan and an MRI? What are PET and SPECT scans used for?
CT (Computerized Tomography) uses a sophisticated X-ray machine combined with a computer to create a detailed picture of the body’s tissues and structures. The scanner circles the patient’s head to obtain thin section views of the brain. Often, doctors will inject a special dye called contrast material into the patient’s vein before performing the scan; this makes it easier to see abnormal tissue. CT is used more often than the MRI because it is more widely available and less expensive. MRI (Magnetic Resonance Imaging) uses a magnetic field rather than X-rays, and can often distinguish more accurately between healthy and diseased tissue. Gadolinium is the contrast agent used with this technique. MRI gives better pictures of tumors located near bone than CT, does not use radiation as CT does, and provides pictures from various angles that can enable doctors to construct a three dimensional image of the tumor. Most patients cannot receive these scans because of problems that might be cau
