What is the difference between a CT and a PET-CT scan?


CT and PET-CT scans are very common procedures that doctors administer every day to help localize their examination and to provide the most thorough diagnosis. Both procedures contain varying, minimal risks but can provide huge benefits for patients that need a more in-depth examination and specialized treatment.

What is a CT scan?

A CT scan or a Computed Tomography scan is a medical procedure that uses x-ray radiation and fascinating computer technology to create cross-sectional images of the body’s organs and tissues. CT scans can also be called CAT or Computed Axial Tomography. CT scans take helical images of the examined part of the body which produces better 3-dimensional imaging. The better the image, the better the diagnosis your doctor can make. CT scans are particularly useful in the examination of tissues, cancer staging, and determining vascular disease.

What is a PET-CT scan?

A PET-CT scan or Positron Emission Tomography is a medical procedure similar to a CT scan but PET-CT scans are commonly used in determining the difference between healthy and diseased tissue. Using nuclear medicine these exams allow particular focus on oncological symptoms in the brain and heart as well as any vascular or tissue abnormalities.

What are the procedures like?

The biggest difference between a CT and a PET-CT scan is the machinations of the procedure. There are varying states of discomfort between both procedures, but both are relatively painless and easy to complete for any patient.

A CT machine looks like a large tire with the patient placed inside the “hole.” The patient is placed on the examination table and will be administered contrast material through the mouth or intravenously. The feet will be the first to enter into the machine and the body will be slowly moved into the chamber. The procedure lasts approximately 10-30 minutes. Patients typically report that they hear a slight whirring sound which is the machine rotating around them gathering imaging. The doctor will able to speak to you and you will be able to respond.

A PET-CT scan is similar to a CT scan in some ways but the biggest difference between the two is the instructions prior to the exam. Most doctors and facilities will request that a patient not eat at least 4 hours prior to the scan and to drink lots of water. The exam also lasts slightly longer at about 30-45 minutes. Contrast material is commonly used as well and will either be  administered through an IV or by inhalation. If the PET-CT scan is being administered because of possible heart disease, the patient will often be asked to perform a stress test. The body will be examined at rest and during exercise in efforts to determine any cardiovascular problems. You may also hear a buzzing or clicking sound during this procedure.

Which procedure is more painful?

Both procedures have a minimal amount of pain and discomfort. The most common complaint is concerning the IV injection site or a claustrophobic feeling. But the contrast material is necessary for properly determining the condition of tissues and veins as well as highlighting possible cancerous cells. Furthermore, the body moves through the machine. It only covers the area that will be examined — it does not encapsulate the entire body.

Are there any risks?

Doctors and imaging facilities have been able to minimize the risks surrounding these procedures to practically nothing. Both a CT and PET-CT scan use small amounts of radiation to image the examined area. If you are pregnant or could possibly be pregnant, you should let your doctor know. There is no medical evidence that the amount of radiation is dangerous for an unborn child. But if there is another safer method to examine, your doctor can help you understand your options. Also if you have any implanted devices, artificial body parts or features such as hearing aids or dentures, talk to your doctor about what needs to removed for the procedure.

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Which is Better: CT or PET Scans for Cancer?

One of the more interesting elements of working in the medical field is that as technology and research advances, what we once believed to be the best method may not be. Where people once thought that butter was good for burns and that smoking wasn’t harmful, we now know better. The world of medical imaging is similar. As the technology advances, more studies are done for different diseases, and we are quickly learning that some of the standard ways of thinking might be subject to change.

Just recently, a new article was published in the Oncology Journal by Cancer Network showed that in one recent study where CTs were the premier choice for finding cancer and determining the degree of disease. CTs or computed tomography, uses computer technology and x-ray in order to create cross-sectional images that physicians glean information. CTs are beneficial when searching for cancer because CTs create cross-sectional images, allowing doctors to see deep into the body through organs, bones, vessels and other blockages. By making cross-sectional images, CTs can examine one section of the organ or area from a multitude of angles. For cancer in the beginning stages, it can very difficult to determine where it is located exactly and where in the body a biopsy needs to be performed.

That is why testing our old ways of thinking is so crucial in this field of medicine. This most recent article found that PET scans for cancer are more beneficial at finding and determining the extent of follicular lymphoma, a form of cancer in which cells a circular pattern in the lymph nodes. There are so many kinds of follicular lymphoma that classifying one in a patient can be difficult even for oncologists. 1 out 5 of every kind of lymphatic cancer is follicular lymphoma making it a common form of cancer and thus all the more important to have the best kind of procedure to go about diagnosing the disease.

PET scans can be used for determining a number of conditions. Most often PET scans for cancer, some cardiovascular problems and a few brain disorders. According to this recent study, PET-CT scans are more proficient at finding follicular lymphoma than contrast-enhanced CT. Contrast material is commonly used in CT scans as a ways for doctors to determine areas of increased or decreased blood flow and to increase the visibility of body tissue or blood vessels. Sometimes contrast material is administered orally to outline the digestive tract and sometimes and intravenous injection is needed to see if body organs are behaving abnormally and/or  possible tumors are present. In PET-CT scans for cancer or heart and brain health, a small dosages of radioactive drug is used to show the differences between healthy and diseased tissue. The radioactive material requires about 30-90 minutes to travel through the body in order to show up on the scan. Do not be alarmed by the use of the word “radioactive.” We use this term to mean that it will react to the PET-CT scan and provides a higher level of contrast which is particularly beneficial when trying to spot difficult to find cancer cells. When it comes to cancer cells, you want to be more than thorough, you want to be exact.