CLINICAL APPLICATIONS OF 18F-FDG PET/CT EXAMINATION IN ONCOLOGY
- Evaluation of disease extent in known malignancies (staging/restaging).
- Detection of tumor recurrence in the presence of elevated tumor markers but without clinical or morphological evidence of disease.
- Search for unknown primary cancer when metastatic disease is the first clinical presentation or when patients present with paraneoplastic syndrome.
- Differentiation between benign and malignant lesions.
- Assessment of disease response to chemotherapy, radiation therapy, targeted biological therapy, and immunotherapy.
- Selection of area for tumor biopsy guidance.
- Preoperative planning.
- Planning of radical and palliative radiation therapy.
CLINICAL APPLICATIONS OF 18F-FDG PET/CT BEYOND ONCOLOGY
The clinical applications of positron emission tomography/computed tomography (PET-CT) using the glucose analog 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) extend beyond the field of oncology.
In the last 2 decades, more clinical applications have been investigated with excellent results in certain pathologies, such as large vessel vasculitis (LVV), spinal infections (SI), osteomyelitis and prosthetic joint infections, diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), inflammatory bowel diseases (IBD), vascular graft infections (VGI), retroperitoneal fibrosis (RF), and COVID-19 infections.
The clinical applications of positron emission tomography/computed tomography (PET-CT) using the glucose analog 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) extend beyond the field of oncology.
- In the heart, FDG uptake by the myocardium allows assessment of myocardial viability in patients with left ventricular dysfunction and coronary artery disease who are planning to undergo coronary revascularization, revealing potential areas of hibernating but viable myocardial tissue. In fact, in many centers, cardiac FDG PET/CT is becoming the gold standard for evaluating myocardial viability. Cardiac FDG PET/CT has high sensitivity of 88% and specificity of 80% with proper preparation (prolonged fasting, increased fat intake, and minimal carbohydrate intake the day before).
- In patients with cardiac sarcoidosis, FDG PET/CT has proven to be a useful tool for disease monitoring. Notably, a high percentage of patients with cardiac sarcoidosis have arrhythmias and implantable cardiac devices that may interfere with cardiac magnetic resonance imaging.
- In Atherosclerosis: Atherosclerotic vessels take up FDG in the intima of large vessels such as the aorta and other major arteries. Increased metabolic activity from macrophages in atherosclerotic plaque is responsible for FDG uptake. Smooth muscles in arterial walls also take up FDG and are visualized with PET/CT.
- In the brain, FDG uptake by cortical and subcortical structures allows non-invasive quantification of cerebral metabolism and can provide valuable information before any morphological changes become visible. Current evidence in epilepsy patients shows that FDG PET can provide crucial data guiding surgical resections of the epileptogenic zone for medically resistant epilepsy. A decade of brain PET research has also proven that FDG PET brain examination is an effective and safe method for identifying diagnostic patterns of glucose hypometabolism in neurodegenerative dementias. The differentiation of 3 major neurodegenerative disorders by 18F-FDG PET, such as Alzheimer's disease (AD), frontotemporal dementia (FTD), and dementia with Lewy bodies (DLB), has become established practice and an effective and useful complement to other diagnostic methods in evaluating patients with progressive cognitive decline.
- In evaluating inflammation and infection: The diagnosis, severity, and extent of aseptic inflammation or septic infection can be challenging, as there is no single test capable of achieving accurate diagnosis. The clinical use of 18F-FDG PET/CT in evaluating inflammation and infection is increasing worldwide. Besides concentration in malignant tissues, FDG also accumulates at sites of infection and inflammation due to increased glycolytic activity of inflammatory cells such as neutrophils, lymphocytes, and macrophages. The first clinical application, from this perspective, was fever and inflammation of unknown origin (FUO/IUO), as FDG PET/CT was able to change clinical management of patients in a high percentage of cases.
In the last 2 decades, more clinical applications have been investigated with excellent results in certain pathologies, such as large vessel vasculitis (LVV), spinal infections (SI), osteomyelitis and prosthetic joint infections, diabetic foot (DF), fungal infections (FI), tuberculosis (TBC), inflammatory bowel diseases (IBD), vascular graft infections (VGI), retroperitoneal fibrosis (RF), and COVID-19 infections.
