The main difference in a PET scan vs. MRI or CT scan is that it can show cellular-level changes and issues with oxygen use, glucose metabolism and blood flow that reveal medical problems at a very early stage.
One thing to note is that traditional PET scan images are less detailed than the images created by MRIs or CT scans. Because of this, there is a hybrid PET-CT scan available that combines the two techniques and creates a very detailed, accurate image. The PET-CT scan is often used to help diagnose cancer.
Magnetic resonance imaging (MRI) scans use magnets and radio waves. Both produce still images of organs and body structures. PET scans use a radioactive tracer to show how an organ is functioning in real time. PET scan images can detect cellular changes in organs and tissues earlier than CT and MRI scans.
Both PET and MRI scans can help detect abnormalities in your body before they get worse. Since PET scans use radiation, MRI scans can be better options for annual screening. And upon your physician's recommendation, you may go for a PET scan.
PET scanning can give false results if chemical balances within the body are not normal. Specifically, test results of diabetic patients or patients who have eaten within a few hours prior to the examination can be adversely affected because of altered blood sugar or blood insulin levels.
Not all cancers show up on a PET scan. PET scan results are often used with other imaging and lab test results. Other tests are often needed to find out whether an area that collected a lot of radioactive material is non-cancerous (benign) or cancerous (malignant).
If undergoing a combination PET-CT scan, the iodine-based contrast dye used for the CT component can cause side effects, including nausea, vomiting, headache, itching, flushing, and mild rash. In rare cases, a serious, all-body allergic reaction known as anaphylaxis may occur.
Weaknesses of PET/MR imaging tool
Technical challenges in building PET/MR systems include: The addition of PET components to the system in the presence of strong magnetic field from MR. Working with long optical fibers. Use of semiconductor light detectors for counting photons.
PET/CT is the most useful test for determining the stage of cancer. It is more accurate than any other test in finding local or metastatic tumors. Although PET can't detect microscopic cells, it can detect clusters of tumor cells that metastasized, or spread, to other tissues or organs.
In general, PET scans may be used to evaluate organs and/or tissues for the presence of disease or other conditions. PET may also be used to evaluate the function of organs, such as the heart or brain. The most common use of PET is in the detection of cancer and the evaluation of cancer treatment.
PET scans can help detect cancer and how far it has spread. PET scans can show solid tumors in the brain, prostate, thyroid, lungs, and cervix. The scans can also evaluate the occurrence of colorectal, lymphoma, melanoma, and pancreatic tumors.
18F-Fluorodeoxy glucose positron emission tomography‒computed tomography (18F-FDG-PET) can detect malignant lymph nodes of even normal size, thus overcoming one of the major limitations of CT.
This type of scan help determine whether a smaller spot is cancerous or benign, as cancerous lesions are much more likely to light up on a PET scan than benign spots or scar tissue.
However, PET scans are more accurate in detecting larger and more aggressive tumors than they are in locating tumors that are smaller than 8 mm a pinky nail (or half of a thumb nail) and/or less aggressive cancers.
The magnetic fields that change with time create loud knocking noises which may harm hearing if adequate ear protection is not used. They may also cause peripheral muscle or nerve stimulation that may feel like a twitching sensation. The radiofrequency energy used during the MRI scan could lead to heating of the body.
The scan usually takes about 15 to 20 minutes but you can expect to be in the PET imaging department for between 2 and 3 hours. Before the scan, you should: ask about any food and drink restrictions before your scan. bring any previous x-ray or radiology images you have.
Why PET scans are used. An advantage of a PET scan is that it can show how well certain parts of your body are working, rather than showing what it looks like. They're particularly helpful for investigating confirmed cases of cancer, to determine how far the cancer has spread and how well it's responding to treatment.
The radioactive tracer gives off very small levels of radiation that go away very quickly. As a precaution, you should avoid close contact with pregnant women, babies and young children for 6 hours after the scan. You need someone to take you home and stay overnight if you've had medicine to help you relax (sedative).
Avoid exercising 24 hours before the scan. Follow a special diet for 12 to 24 hours before the scan. Don't drink or eat anything, except water, for 6 hours before the scan.
Because PET scans read your sugar metabolism, eating sugar could affect the results of your scan. It's also important that you don't exercise for 24 hours before your PET scan. That's because exercise affects the radiotracer's reading and could cause the results to be inaccurate.
[13] showed that PET/CT scan can identify more bone marrow involvement in DLBCL and Hodgkin's lymphoma as compared to bone marrow biopsy with sensitivity, specificity, accuracy, and positive and negative predictive values of 95%, 86%, 87%, and 54% and 99%, respectively.
After the PET-CT scan
You can do normal activities after the scan. This includes driving. The staff will tell you to drink several glasses of water. This helps wash the radioactive substance and dye out of your body.