Discovery PET/CT 690 — Engineer Field Guide

Back to: GE Discovery PET/CT 690.

Two modalities, two failure domains

The 690 is two scanners sharing a table and a console. CT-side failures behave exactly like the LightSpeed VCT (tube, DAS, slip ring, chiller). PET-side failures are their own world.

PET-side failure modes

1. Regional sensitivity loss → PMT dropout. Channel diagnostic in service mode.
2. ToF timing drift → coincidence electronics. Physicist flags at quarterly NEMA.
3. Crystal block aging → gradual energy resolution loss over years. Block-level swap.
4. Calibration rod source handling → Ge-68 decays (~271-day half-life). The 690 automates load/store, but sources need regulated disposal.

CT-side failure modes (cross-reference)

See field-guide/ge-healthcare-lightspeed-vct. Tube scan counts, VDAS ring artifacts, slip ring wear, HV generator faults — same playbook.

Nuclear regulatory posture

Unlike the standalone VCT:

• NRC or Agreement State license required to hold F-18 / Ge-68
• Authorized User (physician) credentialed for PET/CT
• Radiation Safety Officer on file, with documented radiation safety program
• Area survey meter + dose calibrator + daily QC

Throughput truth

Scanner throughput is almost never the limit. Tracer delivery timing, uptake room count, and injected-patient flow gate real-world volume.

Accepting a refurbished 690

• LYSO block replacement history
• PMT channel-health diagnostic report
• ToF timing calibration report
• Ge-68 rod source age and activity
• CT tube scan count + model (Performix Pro)
• VDAS + slip ring service history (see VCT checklist)
• Reconstruction software revision (Q.Clear licensed?)
• NEMA acceptance test data
• NRC license transferability confirmed