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.

Ready to make your appointment? You can use our request an appointment form online or just call us at 504-883-8111.

How PET-CT Scans help Diagnosing, Staging & Treatment for Parkinson’s

Parkinson’s is a disease that affects 1 million people and estimated reports claim that as many as 50,000 to 60,000 new cases are diagnosed per year. The disease has gained more notoriety and support since celebrities like Michael J. Fox and Muhammad Ali have revealed their conditions to the public. Thanks in part to their courageous choice to live in the spotlight with their disease, there more hope for finding a cure and counseling those diagnosed each year.

Neurodegenerative diseases are both emotionally and physically taxing. Whether it is Parkinson’s, Alzheimer’s, or Huntington’s, these kind of diseases can be hereditary and can present in different ways. For some there is a type of foreknowledge if a parent or family member had the same disease but for many, these kind of diseases come as a shock. After the initial diagnosis, most often people want to know how advanced their disease is. There are several tests that doctors will perform to determine a diagnosis of Parkinson’s.

To begin, questions are posed to the patient in regards to their daily life and movements. Has there been increased difficulty performing any of these tasks? Pain performing these tasks? Forgetfulness or lethargy where there was once more energy? After that, the doctor will perform a physical test looking to see the presence of tremors, face slanting, stiffness in the neck and limbs, and balance irregularities. Other tests to test motor functionality are done to see how a patient moves and the time it takes them to perform certain tasks to see if there is a slowing or difficulty.

One method of diagnosis that has been particularly important in studying these diseases and their symptoms is medical imaging. After these preliminary tests are conclusive for Parkinson’s, doctors may prescribe a PET-CT scan to patient. PET scans or positron emission tomography, is a way of imaging the brain that makes deciphering between diseased and healthy tissue the easiest.

Like a traditional CT scan, doctors administer a radioactive drug into the bloodstream that reacts when coming into contact with diseased tissue. The brain is an organ, made up of tissue and billions of nerve cells. Diseases like Parkinson’s cause degeneration in dopamine neurons located in the midbrain. By injecting the radioactive drug 18-fluorodopa into the bloodstream, the PET machine measures the presence of these neurons as highlighted by the drug. It may be worrying to see the word “radioactive” but the drug is an extremely low dose and the procedure only takes 30-45 minutes at most. It is a non-invasive and helps doctors to determine progression of diseases and recommend further treatment.

If you have more questions about Parkinson’s and PET-CT scans, feel free to contact Doctors Imaging office in Metairie at 504-883-8111 or by filling out this online form.