FDG-PET/CT in Oncology

F-18 fluorodeoxyglucose (FDG) PET/CT is the dominant molecular imaging exam in oncology. FDG, a glucose analog, concentrates in metabolically active cells — including most malignancies — and its gamma emissions (via positron annihilation) are detected by the PET ring. Combined with the CT for anatomic correlation and attenuation correction.

Clinical indications

Staging + restaging — lymphoma, lung cancer, head and neck cancer, melanoma, colorectal, esophageal, cervical, many others
Treatment response — mid-treatment assessment, post-treatment residual disease
Recurrence detection — rising tumor markers, indeterminate CT findings
Radiotherapy planning — biological target volume definition
Dementia workup — FDG pattern analysis (neuro PET, separate protocol)

Workflow

Patient prep — NPO 4–6 hours, glucose < 200 mg/dL at injection
Injection — ~10 mCi F-18 FDG IV
Uptake — 60 min in a quiet shielded uptake room
CT — low-dose CT for attenuation correction + anatomic localization (sometimes diagnostic-quality contrast CT)
PET acquisition — 6–8 bed positions skull base to mid-thigh, 2–3 min per bed
Reconstruction — ToF + iterative (Q.Clear on GE, TrueX on Siemens)
Read + report — SUV max measurements, staging, comparison to priors

Typical systems

GE Discovery 690 (ToF, LYSO)
GE Discovery MI (digital, SiPM)
Siemens Biograph mCT
Biograph Vision (digital)
Philips Vereos (digital)

Throughput reality

Scanner throughput rarely limits real-world PET volume. Limits are:

Tracer delivery timing — F-18 half-life is 110 min; daily morning delivery scheduled to the scan day
Uptake room count — patients occupy uptake rooms for 60+ min; 2 rooms ≈ 12–15 patients/day, 3 rooms ≈ 16–20
Injection cadence — one injection per 10–15 min during the morning

Dose + regulatory

Patient dose ~7–15 mSv (CT + PET combined). Staff dose ALARA — shielded injection, pre-injection room, uptake rooms, control area. NRC or Agreement State license required. RSO + authorized user credentialing mandatory.