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What’s the Difference Between a CT Scan and an MRI?

CT scans and MRI scans both provide diagnostic images of the inside of your body. However, they accomplish this important task in very different ways. Here are a few key differences between CT scans and MRI scans.

Radiation

CT, which is short for computerized tomography, uses x-ray technology to produce diagnostic images. These x-rays require a small dose of ionizing radiation. Basically, the CT scanner rotates on an axis, taking multiple 2D images of a person’s body from different angles. When a computer places all of these cross-sectional images together on a monitor, the result is a 3D image of the inside of the body that can reveal the presence of disease or injury to a physician.

MRI scans do not work this way. Instead of using ionizing radiation, magnetic resonance imaging (MRI) uses radio waves and powerful magnets to produce diagnostic images. An MRI scanner can apply a magnetic field that lines up all of your body’s protons. Radio waves are applied to these protons in short bursts, which in turn relate a signal that is picked up by the MRI scanner. A computer processes this signal and generates a 3D image of the segment of the body being examined.

Time

CT scans typically take diagnostic images more quickly than MRI scans. For example, a CT scan can often be completed in less than 5 minutes while MRIs take an average of 30 minutes.

Purpose

CT scans and MRIs are also used for different purposes, although either can be used in some instances. CT scans are extremely helpful in diagnosing serious injuries to the head, chest, abdomen, spine and pelvis, especially fractures. CT scans are also used to pinpoint the size and location of tumors.

MRIs, on the other hand, often do a better job of diagnosing issues in your soft tissues, joints, tendons and ligaments. Doctors frequently order MRIs to scan the brain, spine, neck, breast, abdomen and muscles. MRI is a particularly good tool for evaluating the spine and spinal ligaments, according to ABC News.

Seattle Diagnostic Imaging Services

Via Radiology provides Seattle radiology and diagnostic imaging procedures including bone density exams, mammography, ultrasound, MRI, PET scan exams and CT scan exams. Contact us online for more information.