9702 · 24.3
PET scanning — FAQ
Frequently asked questions for 9702 PET scanning. Direct answers first, then deeper explanation — then practise with marking.
How does PET scanning help detect diseases like cancer?
Cancer cells often have a higher metabolic rate than healthy cells, meaning they consume more glucose. The PET tracer, often a glucose analogue like FDG, accumulates in these 'hungry' cancer cells, making them light up brightly in the scan, helping doctors identify tumours.
What is the typical half-life of radionuclides used in PET scanning?
Radionuclides used in PET, such as Fluorine-18 (F-18), typically have very short half-lives (e.g., F-18 has a half-life of about 110 minutes). This ensures the patient's exposure to radiation is minimised and the radioactive material decays quickly within the body.
Are there any alternatives to PET scanning?
Yes, other imaging techniques exist depending on the diagnostic need. MRI (Magnetic Resonance Imaging) and CT (Computed Tomography) scans provide detailed structural images. SPECT (Single-Photon Emission Computed Tomography) also uses radioactive tracers but detects single gamma rays emitted directly from the decay, not from annihilation, which generally results in lower resolution than PET.
Why are PET scans often combined with CT scans (PET-CT)?
PET provides excellent functional information (metabolic activity) but has poor spatial resolution. CT provides excellent anatomical detail but no functional information. By fusing the images from both scans, doctors get a single image that shows both the precise location (from CT) and the metabolic activity (from PET) of a lesion or tumour.