Download Positron Emission Tomography / Computer Tomography (PET/CT

Positron Emission Tomography / Computer Tomography (PET/CT)
Positron Emission Tomography (PET)(1,2) is a nuclear medicine, functional imaging technique
that produces a three-dimensional (3D) image of functional processes in the living body. The
system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide
(tracer), which is introduced into the body on a biologically active molecule.
3D images of tracer concentration within the body are then constructed by computer
technique and analysis. In PET/Computer Tomography (PET/CT) scanners, 3D imaging is
often accomplished with a diagnostic CT (X-ray) scan performed on the patient during the
same session, in the same position.
Built into one instrument, with the combined PET/CT technique the aquisition is processed in
the same time and position, decreasing 4-5 times the former PET test duration. During the
examination the functional map provided by PET is projected into CT morphological data,
thereby significantly improving the accuracy of the lesion localization. The dual-modality
technology is spreading rapidly in the world. In the oncology patient care - clinical and
diagnostic experts general opinion is - that the PET/CT measurements are indispensable for a
quality patient care.
The use of PET/CT corresponding the algorithm trigger other processes, (may) reducing the
number of unnecessary surgical interventions, can change the therapy etc, reducing „the total
cost of a patient care”. The biggest indication field of using PET/CT is oncology, followed by
neurology and cardiology. The most commonly used glucose-metabolic PET with measuring
the metabolic-activity create an opportunity to a „non-invasive” estimation of the growth rate
of tumors, where the agressive tumors exhibit increased glucose uptake and contrary.
The different function display PET method can detect the lesion prior to conventional imaging
procedures. The hibrid technigue is widely used for staging, restaging of patients with
different malignant tumors, to detect cancers of unknown origin, etc. PET/CT provides
information in many fields where the other non-invasive tests ((laboratory, endoscopy, X-ray,
ultrasound CT, MRI techniques, SPECT/CT) fail or insufficient.
The PET is adapted to – in contrast to the conventional imaging techniques – demonstrate
with a single test the primary tumor, the local and distant metastasis. The PET/CT provides
reliable information in mapping the exact location of the biopsy specimen, in planning of
surgery or radiotherapy, in definition of the target volume, in the measurement of the response
to therapy even if the results of other diagnostic tests are uncertain or insufficient.
The most widely used tracer is 18F-fluorodeoxyglucose (18F-FDG), an analogue of glucose. If
the biologically active molecule chosen for PET is 18F-FDG the concentrations of tracer
imaged will indicate tissue metabolic activity by virtue of the regional glucose uptake. Use of
this tracer to explore the possibility of cancer metastasis (i.e., spreading to other sites) is the
most common type of PET scan in standard medical care (90% of current PET scans in the
world and 99% in Hungary). However, on a minority basis, many other radioactive tracers are
used in PET to image the tissue concentration of many other types of molecules of interest
(18F-DOPA, 68Ga-DOTATOC or -DOTATE for endocrine tumors, 18F-NaF for bone lesions,
18
F- or 11C-Choline or Acetate for prostate tumors, etc.)(3).
Borbély K.: Az agyi működészavarok megjelenítése funkcionális képalkotó módszerekkel. Medicina
Könyvkiadó, Budapest, 2005, pp. 431.
2. Borbély K.: Funkcionális képalkotás az onkológiában. In: Kásler M. (szerk.): Az onkológia alapjai.
Egyetemi tankönyv. Medicina Könyvkiadó Zrt., Budapest, 2011, 229-256.
3. Borbély K.: PET/CT és prosztatarák. In: Géczi L., Kásler M. (szerk.): Prosztatarák. Gyakorlati
kézikönyv. Zafír Press, Budapest, 2013, 93-140.
1.