Positron EmissionTomography- Computer Tomography (PETCT) with 18F fluoro-2-deoxy-d-glucose (FDG) imaging is a fusion imaging technique that has emergedas a new diagnostic, screening and management tool for anatomical andfunctional evaluation in breast cancer. This new imaging tool provides valuableinsight pertaining accurate lesion detection and localization, lesion characterization, proper staging, and appropriatetreatment.
18 F FDG PETCT generallyinvolves two steps. First, a positron emission tomography (PET) is performed.This generates images that are attributed to the three-dimensionalradioactivity distribution from annihilation emitted by positron emitter. Thismode of imaging allows non-invasive quantitative assessment of biochemical andfunctional processes. The second part of 18 F FDG PETCT generates computertomography (CT) images. The produces images by using x-ray beams.
As a result,high resolution anatomic and morphological structures are displayed6. Thus, PETCT allows acquisition of functionaland morphological imaging in the same setting 7. Besides this advantage, other benefits of PET/CTare lesion detection and characterization. Studies have shown that comparisonof between PET and CT alone with hybrid imaging PETCT reveals the later to bemore precise or sensitive in terms of accuracy.
FDG (Flurodeoxyglucose- aglucose analogue) is the routine tracer used in breast cancer patients. 18 Fluorine is apositron-emitting radionuclide radioactive trace tagged onto FDG9. FDG is transported into cells after intravenousadministration. Subsequently, FDG undergoes phosphorylation by hexokinase itremains trapped in cells as FDG-6-phosphate. Hence, cellular glycolytic rate is proportional to accumulationof FDG in cells by reflecting cellular glucose transport and hexokinaseactivity which is potentially semi-quantitative with standardized uptake value(SUV) 11. The detection of phosphorylated 18F-labeledmetabolite by PETCT is the basis of accurate lesion detection and localization, lesion characterization.
An important note also shouldbe made to factors that influence FDG uptake for example tumor size and grade.In addition to that certain histological types of breast cancer namely lobularcarcinoma have reduced or no FDG uptake12. These are pertinent information that affect the tumouruptake on 18F FDG PETCT and determines the maximum standardize uptake value(SUVmax). It isimperative to distinguish normal and abnormal radiotracer uptake in 18 F FDGPETCT13, 14.
Some of the normal or better coined as physiologicallyincreased FDG uptake occurs in brain, heart, brown fat, urinary tract, the intestinaltract and muscles.Abnormal or pathologicalFDG uptake is demonstrated in malignant cells as there is an increased membraneglucose transporter proteins (notably GLUT1 and GLUT3) and enzymes (intracellularhexokinase and phosphofructokinase) along the glycolytic pathway. In additionto patient preparation, fasting is crucial to promote FDG accumulation inabnormal tissues and reduce competition of blood glucose with FDG