The last five years have seen unprecedented advances in medical imaging techniques, allowing doctors an extraordinary view into the human body and the opportunity to fine-tune treatments.
Speaking at a recent international radiology conference in Cape Town, Professor Raffaele Giubbini, Chief of Nuclear Medicine at the University of Brescia, Italy, says "It is not an exaggeration to say that there has been a revolution in radiology over the last five years."
He cites PET/CT imaging as the most important of the new technologies.
What is PET/CT?
Positron Emission Tomography (PET) and Computed Tomography (CT) are imaging techniques that have been around for some time. The innovation has been to combine the two into one procedure: PET/CT.
Using CT alone
CT scans produce detailed images of anatomical structures: organs and tissues.
The technique makes use of x-rays and a computer to produce images of sections of the body, showing greater detail and clarity than with standard x-rays.
The patient receives a contrast enhancing agent by intravenous line (IV), which helps produce an even clearer image.
Using PET alone
PET scans aren't designed to show biological structures. Instead, they provide images of biological functions, like blood flow or glucose metabolism (the breakdown and use of sugar by the body).
Cancer cells metabolize sugar at a higher rate than normal cells do, and this abnormal activity can show up on a PET scan. PET can be used to detect the metabolic changes associated with cancer much earlier than is apparent from looking at tumors or other physical changes in the organs.
For the PET scan, a small amount of radioactive material, called a radioisotope, is injected into the bloodstream. The PET scanner detects the radioisotope and then creates an image on a computer screen.
'Fusing' PET and CT
The 'fusion' of PET and CT provides both the metabolic information of PET and the fine anatomic detail of CT at once. Together, PET and CT produce a more accurate image of disease in the body than PET or CT alone.
A PET image is colour coded, with the different colours indicating different levels of cell activity. A CT scan shows the locations of the body’s organs and also can show abnormal growths.
When a CT scan is superimposed on a PET scan, doctors can ascertain the exact location of abnormal cell activity. They can also use PT/CT to decide at what stage the cancer is, and whether and how far it has spread.
Not only van PET/CT help with early diagnosis, it can help doctors decide on the best treatment, and then also show how the cancer is responding to treatment.
PET/CT and heart disease
PET/CT is also proving to be an effective tool in diagnosing cardiovascular problems. It can be used to produce images of the anatomical structures of the heart, blood flow in the coronary arteries and metabolic rate within the heart.
In patients with heart disease, doctors can use PET/CT to identify areas of decreased blood flow such as occurs when there is a blockage, or where the heart muscle has been damaged.
Prof. Giubbini anticipates that the current radiology revolution is just the start.
"One thinks of science fiction movies, where the doctor holds a device over the patient and gets all the information needed. We're not quite there yet, of course, but the field is making huge strides."
Giubbini explains that the focus has moved from viewing gross anatomical structures (such as a tumour), to viewing the physiological processes involved in disease (such as rapid multiplication of cancerous cells). In the near future, the focus will increasingly be on a cellular and molecular scale.
PET/CT scanning can be viewed as a major development in this direction: looking deeper and deeper into the body at smaller and smaller structures and processes – right down to cellular and even genetic level. The obvious advantage of this is that diseases can be caught and treated far sooner, and more appropriately.
- Health24, September 2006