PET-CT scan studies are used especially in certain psychiatric, neurological and cardiological diseases, but unquestionably its main field of application is in oncology, where the introduction of whole body PET and the FDG radiopharmaceutical has achieved extraordinary clinical results.

Main indications for PET-CT scan. MUFACE Society.

Medical area: PET in Oncology

Indications for PET include the study of oncological, neurological and cardiological processes. However, its main field of application is in oncology, where the introduction of whole body PET and the FDG radiopharmaceutical has achieved extraordinary clinical results.

What are the general indications for a PET scan in oncology?

PET scans were initially used to obtain functional studies of the brain and heart, but, as from the introduction of whole body PET scans, they became especially indicated in oncology, as they provided coronal images of the body, complemented by sagittal and axial studies. The advantage of studies performed with PET is that they detect the activity of very small masses of cancerous cells, which give an adequate indication of tumour activity. Therefore, the general indications for a PET scan in oncology include:

  • Initial diagnosis of cancer. Very early diagnosis, in many cases earlier than with other examination methods.
  • Differentiation between benign and malignant tumours.
  • Determination of the degree of tumour malignancy, and therefore, prognosis of its course.
  • Staging the extent of the disease, as it is able to provide images of the primary tumour, lymph node involvement and metastasis.
  • Confirmation of lesion significance detected by CT, MRI and X-ray studies.
  • Treatment response follow-up monitoring.
  • Detection of possible disease recurrence, especially in patients with a high level of tumour markers, even with negative results in other examination techniques.
  • Differential diagnosis between tumour recurrence and scar tissue or radionecrosis, due to radiotherapy.

With which tumours is PET imaging particularly useful?

PET scan studies have proven useful with different types of tumours amongst which are the following:
  • Breast cancer
  • Colorectal cancer
  • Brain tumours
  • Lymphomas, Hodgkin and non-Hodgkin
  • Lung cancer, especially non-small-cell carcinoma
  • Melanoma
  • Head and neck cancer
  • Oesophagus cancer
  • Thyroid cancer
  • Ovarian cancer
  • Pancreas cancer

Medical area:PET in Neurology

What are the indications for a PET scan in psychiatry and neurology?

One of the fundamental indications for a PET scan is the study of all types of dementia and degenerative brain disease.

Owing to the high rate of glucose metabolism in brain cells, it is possible to detect a decrease in the very early stages. Thus, its capacity for the early detection of Alzheimer's disease and other processes (senile dementia, multisystemic atrophy, progressive supranuclear palsy, corticobasal nucleus degeneration, etc.).

The extraordinary importance of this technique will be confirmed as advances are made in the treatment for Alzheimer's disease in the early stages. A PET scan study is also useful in Parkinson's disease, fundamentally by means of the use of F18-Dopa, but also by means of FDG, as it is possible to observe a decrease in its metabolism at caudate nucleus level when this disease exists.

In a similar fashion, it is possible to detect the existence and location of epileptogenic sites, particularly in those cases in which treatment consisted of surgical resection; in certain psychiatric diseases (schizophrenia), in the after effects of traumatism and in drug abuse.

Medical area: PET in Cardiology

What are the indications for a PET scan in cardiology?

A PET scan study is essential in order to determine viability. When FDG metabolism still exists, surgery (a by-pass) may be indicated, whereas if there is no FDG metabolism, a heart transplant would normally be chosen as treatment.

Indeed, FDG PET scan studies allow discrimination between necrotic and viable ischemic myocardium. If a reduction in FDG metabolism is observed, it is possible to confirm that non-viable myocardium tissue exists, and that it will not benefit from restored blood circulation. On the other hand, the detection of normal tissue metabolism indicates its viability, and ensures there will be an improvement with restored blood circulation.

Thus, it is possible to remove from the transplant waiting list those patients who will improve with a by-pass or an angioplasty, therefore also allowing financial savings.

Myocardium perfusion and metabolism study with 13N-Amonium and FDG respectively, with a match pattern in which it can be seen that there is absence of both perfusion and metabolism in the antero-septal region, indicating lack of myocardium viability, and therefore discarding the possibility of revascularization treatment (by-pass).

Patient with acute myocardial infarction (AMI) history and PET mismatch pattern in which lack of perfusion can be seen laterally with metabolism persistence, compatible with viable myocardial tissue. After revascularization surgery, myocardium recovery is observed, together with perfusion and metabolism normalization.

Medical area: PET research

The continual development of radiopharmaceuticals leading to the almost daily appearance of new ones increases more and more the potential of PET scan studies, not only in the field of clinical application but also from the research point of view. It is possible to mark practically all biological molecules with a given positron emitting isotope, making the range of possible applications extremely wide.

From the development of new treatments, by checking their efficacy and receptor union, to its application in in vivo gene therapy, which is now so much on the increase, the possible applications are almost infinite.

What research are used in PET studies?

Only we mention the large number of studies using PET that are made today , both clinical and basic . Clinical studies cover the three main PET indications : Neurology (especially Alzheimer's disease, epilepsy, degenerative diseases ) ; Cardiology ( myocardial viability , other cardiological indications ) and especially Oncology ( new cancer markers, precocity in initial cancer detection, monitoring response to chemotherapy and radiotherapy , evaluation " in vivo " gene therapy etc. ) .

As for basic applications studies using PET, remember only three major fields of application, neuroscience , molecular biology and pharmacology , especially drug design , apart from many other specific applications in fields of medical research , drug and biological .

What is the future of PET ?

No imaging modality has undergone a more complex route that PET clinical acceptance . With its origins half a century ago founded on research, PET was given practically dead in the early 90s but increased funding and an increasing number of clinical uses have resulted in an almost unstoppable demand today .

Today , PET is demonstrating its utility in a wide range of conditions, from cancer to neurodegenerative diseases . But while its utility has become a point without discussion , there are still many questions about how to create a new PET facility especially for the high investment involved and the various possibilities that exist today. The new hybrid scanners CT / PET fused images provide anatomical images metabolism but at a price , now very high day , limiting his implantanción , as only large centers can undertake important investments.

PET provides quantitative in vivo measurement of functional processes such as perfusion, metabolism, and receptors. Its primary applications are in oncology, cardiology and neurology.

PET imaging has a brilliant future. New developments in tomography are pointing towards the manufacture of organ specific imaging devices, which will allow greater anatomical resolution. New, more efficient detection materials are being developed, and reconstruction techniques are improving. However, perhaps the most important area for further expansion of PET is the development of new radiopharmaceuticals, such as fluorotyrosine, fluorthymidine and C11-choline. When more tumour-specific agents are achieved, there is going to be a much more expansive application field, and it is likely that there will be diagnostic agents for every tumour.

PET imaging will soon be reimbursable for all cancers, and infectious diseases will become a major focus of PET procedures. The modality is already being used to detect infections in orthopaedic prostheses, which increases even more its potential applications.

In the near future, metabolism and anatomy image fusion will also be commonplace. This will provide more accurate diagnoses and more appropriate treatments to keep side effects down to a minimum.