Since the 90ties the PET (Positron-Emission-Tomography) has gained increasing significance in the clinical diagnostics of cancer diseases and in early diagnosis of the Alzheimer’s disease. Oncological PET is based on the principle already discovered by Otto Warburg in 1927. It says that tumours have an intensified metabolism and thus have an increased sugar uptake and can thus be distinguished from malignant tumour tissue. Using weak radioactively marked glucose (sugar) the Positron-Emission-Tomography can track, and subsequently quantify the glucose metabolism within a patient without physical intervention. Functional images can be created from the data obtained. In most oncological problems the PET is absolutely superior to usual examination procedures, such as Computer-Tomography, nuclear spin resonance tomography, ultrasonography, tumour marker determination and clinical examinations. Thus PET detects e.g. even more tan 80times as much cancer in an early stage than examinations in the normal preventive medicine. PET is superior to all other methods in the search for unknown primary tumours or when distinguishing between a normal scar after a cancer operation and a cancer relapse.
Furthermore, PET can already diagnose after a short time period, whether chemotherapy will be useful for a patient suffering from cancer, so that, if necessary, a new therapy concept can be created. Thus side-effects of an ineffective chemotherapy can be avoided and costs can be saved.
As there already are medicaments that can delay or stop the development of the Alzheimer’s disease, the use of PET in the early diagnosis of Alzheimer’s is very important and most helpful.
In the new piece of equipment both a PET and CT machine of highest diagnostic quality have been combined. The combination of both allows a reduction of whole body examinations currently 60 minutes to 15 minutes with a much higher quality. Through the combination of both morphologic and metabolic information the significance of the separate procedures increases. A significant improvement of sensitivity as well as specificity is achieved. On the one hand the combination allows an exact anatomic assignment of conspicuous PET findings; on the other hand an improved assignment of marginal CT findings is made possible. Besides this, diagnostic findings of both processes that are not conclusive on their own, can give a conclusive answer in combination.
Altogether, PET is an non-invasive, imaging examination procedure with enormous potential and possibilities in cancer diagnostics, which has only in recent years been implemented in clinical routine. In the USA, as well as in Italy, Switzerland and Belgium, the procedure has already been accepted by the FDA and is paid for by compulsory health insurance funds. In Germany this applies only restrictedly PET examinations for patients suffering from lung cancer (also see News: PET for lung cancer now convention medical GKV service). This actually is the case, although a high number of original publications considering the topic PET/CT since 2004 made by well-known magazines, such was “New England Journal of Medicine” (Juweid and Cheson 2006), “Radiology” (by Schulthess et al. 2006) and “British Journal of Radiology” (EIL 2006), have declared the PET/CT in compendium works as the “Golden Standard”. A corresponding articles can be found in multidisciplinary German-speaking magazines, such was “Deutsche Medizinische Wochenschrift”, DMW (Bamberg, Diehl et al. 2006) and the “Deutsches Ärzteblatt” (Bockisch et al. 2006).
The detection margin of PET is placed in the area of 105 to 106 malignant cells. A tumour of 106 cells has a diameter of about 1mm (European Journal of Nuclear Medicine Vol.33 No6). PET can, according to this, detect malignant processes before morphologic changes occur.
What is PET/CT able to diagnose?
PET is used in various phases of cancer diseases and cancer treatments. Most importantly before therapy is the detection search of primary cancer focuses and especially the characaterisation and staging of the disease.
In therapy (Chemo/Radiationtherapy) the success can be assessed and judged directly after the end of therapeutic measures.
After a cancer therapy, in follow-up care, PET allows an early diagnosis of recurrent or metastatic disease.
- Search for cancer focuses and assessment of malignance
- Determination of disease stage
- Specified determination of target areas for irradiation to avoid damage to healthy tissue
- Early evaluation of therapy success
- Certainly after cancer operations
What else can PET/CT do?
Besides cancer diagnostics, PET plays an important role in coronary heart diseases and neurologic problems, e.g.
- in cardiology
- Diagnosis of cardiac infarction or regional myocardial perfusion rebleed
- Before heart transplantations
- Early diagnosis of the Alzheimer’s disease
- Differentiation of depression/dementia
- For the pre- surgical localisation of epilepsy focuses
- In early diagnostic of the Parkinson’s disease or a degenerative multisystem disease
Up to now the basis of most established staging methods of malignant tumors, e.g. the TNM-System, is morphologic imaging, e.g. CT. This staging method does not only serve as basis for therapeutic decisions, it is also used for risk assessment. As mentioned before, CT often is inferior to PET. A CT cannot be used to assess, whether small lymphatic nodes are affected by metastases whereas a PET can. In addition to this, PET can perform a whole body examination. However, a problem during the interpretation of PET images often is the exact anatomic determination as a result of partly insufficient contrast of healthy structures in those images. Thus localisation diagnostics for surgical interventions becomes difficult. The interaction of morphologic (CT) and functional (PET) images, which have been made by different machines, has intensively been researched since years.
An optimal solution to synchronise functional and anatomic information to accordance is the simultaneous acquisition of both functional (PET) and anatomic (CT) information using only one piece of equipment, without the patient having to move or leave the bed between examination procedures.
The machine, which has been installed now, consists of a PET, produced by CTI PET-System Inc., Knoxville, USA, that corresponds with the latest development standard with novel cristals, special electronics and software. The CT is a Multislice-CT with 16 rows, produced by the Siemens AG. The CT also corresponds with the latest development standard and is, without any doubt, the most interesting development in computer tomography, over the last years. The Multislice-CT technology has an immense and opened upon new perspective in the use of contrast agents during examinations, particularly in the area of CT-angiography of the brain, heart and vessels with high quality and artefact-free three-dimensional reconstruction.
Especially in the area of coronary blood vessels, this new technique allows a three-dimensional illustration of the vessels, without the necessity of invasive diagnostics using a catheter.
In the latest piece of equipment both a PET and a CT machine of highest diagnostic quality have been combined together. The combination allows a reduction of a whole body examination of currently about 60 minutes significantly down to less than 15 minutes with a much higher quality. Through the combination of morphologic and metabolic information, the significance of each sole procedure is vastly increased. A significant improvement is achieved concerning sensitivity as well as specificy. The combination allows on the one hand an exact anatomic determination of conspicuous PET-findings and on the other hand an improved determination of CT-findings with border-line values. Also findings, which are not conclusive in eithe examination procedure, can result in a definite finding together.
Alongside with this high diagnostic potential of the PET/CT, the combination of data shows an enormous improvement in the planning of radiationtherapies, as through the use of focal metabolic parameters in the radiation planning for an optimised target determination and a significantly improved care of healthy tissues surrounding the radiation area.
Our first PET in 1994:
At this time, we were the first surgery in Europe that installed a dedicated PET. In cooperation with the “Universitätsklink Bonn” we used the actual research findings to prepare the PET’s way into clincal routine.
State of the Art: A PET/CT with a 16 Multi-Slice-Technique
Our nuclear medical consultants Prof. Dr. Dr. med. J. Ruhlmann and Mrs. D. A. Rosanwo were under the first 40 doctors, who were certified in May 2006 by the DGN.