Hi Ladies,
I’m nearly two years post treatment, surgery, chemon and rads for triples neg. I had appointment with my Onc last Wednesday and she wants me to have an MRI and CT scan due to pain in my back and tingling in my leg. Well got the MRI the next day at 11.00 and results at 2.30 and was fine - what I don’t understand is if MRI was clear why is she still sending me for a CT scan. Does anyone know the differences in these scans.
Angela
angie
hi. welcome to the forum, but am so sorry that you are having this problem. I am also triple negative; have had surgery, 6 of 9 chemo treatments and will be having radiation shortly. I did a bit of research for you…something in normal english instead of medical jargon. Hope it helps. It is from Ask Alice.
What is the difference between CT and MRI? And what does with or without dye mean?
CT scans and MRIs are both diagnostic tests that provide us with high-resolution pictures of the structure of any organ or area of the body which requires a thorough examination. Both tests take place in big, somewhat intimidating machines. They each us e computers to construct pictures of the inside of the body. There are, however, inherent differences in these tests’ mechanisms, as well as sophistication and applications. Since CT scans were developed and used before MRIs (in 1972), let’s discuss them first. CT, or CAT, stands for “computerized axial tomography.” Basically, CT scans consist of a highly sensitive x-ray beam that is focused on a specific plane of the body. As this beam passes through the body, it is picked up by a detector, which feeds the information it receives into a computer. The computer then analyzes the information on the basis of tissue density. This analyzed data is then fed into a cathode ray tube (the device responsible for producing pictures on your TV screen), and a picture of the x-rayed, cross-section of the body is produced. Bone shows up as white; gases and liquids as black; and, tissue as varying shades of gray, depending on its densi ty.
Magnetic resonance imaging (MRI) was developed later than CT scanning, first being used in the late 1980s. An MRI machine uses computer-controlled radio waves and very big magnets, which create a magnetic field roughly 25,000 times stronger than the eart h’s magnetic field. After the machine creates a magnetic field, it sends radio waves into the body and then measures the response of its cells (how much energy they release) with a computer. From these responses, the computer is able to create a three-d imensional picture of the inside of the body. MRI makes use of the fact that all living cells have a certain magnetic quality to them; because of this, MRI can provide a look at the biochemistry of living cells.
Both tests provide detailed pictures of areas of the body that used to be inaccessible by conventional x-rays. Therefore, 20 - 25 years ago, exploratory or invasive surgery may have been required. CT scans give us excellent information on anatomical fea tures and tissue density (this allows for the detection of tumors, and sometimes the ability to distinguish between malignant and benign tumors). CT scans can also detect calcium deposits, cysts, and abscesses. They are often used in place of ultrasound for obese patients because fat deposits often hinder ultrasonic waves. CT scanning does carry with it the risks associated with x-ray exposure, although it is significantly less than that from ordinary x-rays.
On the other hand, MRI has no known associated health risks. However, people with pacemakers, aneurysm clips, or other implants that contain magnetic materials are generally advised not to undergo MRI testing. What can be learned from MRIs is, generally , more sophisticated and detailed than from CT scanning. MRI is best put to use in examining the central nervous system (the brain and spinal cord). It can also be used to identify tumors, strokes, degenerative diseases, inflammation, infection, and oth er abnormalities in organs and other soft tissue of the body. One last major difference is cost – MRIs cost a lot more than CT scans.
“With or without dye” simply refers to a contrasting agent that is sometimes used with these tests. It is either injected into or ingested by the patient. When the test is performed, the contrast allows the radiologist to see more clearly the image of a certain area or organ of the body.
There are other more complicated differences than Alice has described here, especially in terms of how the tests actually work. Alice hopes that she was still able to shed some light on the basic differences between the two tests. If you want to know mo re, especially if you are having one of these tests done, you can ask for information at a radiology department, where you have to go for these tests. And, if the answers you’re given still aren’t enough, ask one of the technicians or your doctor.
Hi EmilyJane,
wow, thanks so much for that, certainly helps explain things.
angela