Spine Scans Explained: X-ray, MRI, CT and More
X-ray, MRI, CT, myelogram, SPECT-CT. Spine care comes with a lot of tests. Here is what each one shows, when it is used, and what to expect, in plain English.
First, the big idea
A scan is a picture. Pictures are important, but they do not feel pain. You do. A good spine doctor matches what is on your pictures to where you hurt and what they find when they examine you. That match is what tells us what is really going on. Many findings on scans are normal aging and cause no pain at all.
X-ray
Shows: Bones and how they line up. Standing X-rays show your spine under the weight of your body. Bending X-rays (leaning forward and back) show whether a bone slides or wobbles.
Does not show: Discs, nerves or the spinal cord.
What to expect: A few minutes. A small amount of radiation.
MRI (magnetic resonance imaging)
Shows: Soft parts of the spine: discs, nerves, the spinal cord, ligaments, swelling and fluid. It is the best test for a pinched nerve or a herniated disc.
Does not show well: Fine bone detail, or whether a bone moves when you bend, because you lie still during the test.
What to expect: No radiation. It is loud, and you lie still in a tube for about 20 to 45 minutes. Tell the staff about any metal in your body, a pacemaker, or if you are claustrophobic. Some people need contrast dye, often after a prior spine surgery.
After surgery: Metal screws and implants can blur nearby parts of the picture. Special MRI settings help. Read about MRI after spine surgery.
CT scan (computed tomography)
Shows: Bones in sharp 3D detail: bone spurs, fractures, whether a fusion has healed, and exactly where screws sit.
Does not show well: Nerves and discs. It is better than MRI for bone and worse for soft parts.
What to expect: Fast, usually a few minutes. It uses X-rays, so there is more radiation than a plain X-ray.
CT myelogram
Shows: A doctor places dye into the fluid around the nerves through a small needle in the back, then a CT is done. The dye outlines the nerves and the spinal cord, so we can see exactly what is pressing on them.
When it is used: When you cannot have an MRI (some pacemakers or metal), when metal from a prior surgery blurs the MRI, or when the MRI does not answer the question.
What to expect: A needle in the back, then a CT. You may be asked to rest afterward. A headache is possible.
SPECT-CT (bone scan with CT)
Shows: A small amount of tracer is injected in a vein. It collects where bone is active or irritated. Combined with a CT, it shows “hot spots,” such as an inflamed joint or a fusion that has not healed.
When it is used: To help find which joint or level may be causing pain when the MRI does not answer it, or to check a fusion that may not have healed.
What to expect: An injection, a wait of a few hours, then the scan.
MR spectroscopy
Shows: A newer MRI-based test that measures the chemistry inside discs to help point to which disc may be causing low back pain.
Good to know: It is not offered everywhere and insurance may not cover it. It can add information but does not replace your exam and other tests.
Discogram
Shows: A needle is placed into a disc and fluid is injected to see if it brings on your usual pain.
Good to know: It is used rarely now. It can be uncomfortable, and doctors disagree about how useful it is.
Bone density (DEXA) scan
Shows: How strong your bones are. It checks for thin bones (osteopenia or osteoporosis).
When it is used: Not everyone needs one. Your surgeon may order it before a fusion or disc replacement if you are at higher risk for weak bones, for example if you are older, have had a fracture from a minor fall, smoke, or have taken steroids for a long time. Screws and implants hold best in strong bone.
What to expect: You lie on a table for a few minutes. Very little radiation.
EMG and nerve conduction test
Shows: Not a picture. Small needles and stickers on the skin test how well your nerves and muscles work.
When it is used: To tell a pinched nerve in the spine apart from a nerve problem in the arm or leg, such as carpal tunnel syndrome or neuropathy.
Quick guide
| Test | Best at showing | Radiation |
|---|---|---|
| X-ray | Bone alignment, slipping or wobbling bones | Small |
| MRI | Discs, nerves, spinal cord | None |
| CT | Bone detail, fusion healing, screws | Yes |
| CT myelogram | What is pressing on nerves when MRI is not possible or not clear | Yes |
| SPECT-CT | Irritated or active bone, unhealed fusion | Yes |
| MR spectroscopy | Disc chemistry | None |
| Discogram | Whether a disc reproduces pain | Small |
| Bone density (DEXA) | Bone strength | Very small |
| EMG | How nerves and muscles work | None |
Bring the pictures, not just the report
The written report is one person’s reading of your images. Reports can differ from reader to reader. Read why MRI reports differ. If you are seeing us, please send the actual images. Confused by the words in your report? See our MRI report glossary.
Call 609-800-3472 or send us your MRI.
This page is general information, not medical advice. Talk with your own doctor about your situation.